U.S. patent application number 16/086880 was filed with the patent office on 2019-04-04 for method for initial access using signatures.
This patent application is currently assigned to IDAC HOLDINGS, INC.. The applicant listed for this patent is IDAC HOLDINGS, INC.. Invention is credited to Yugeswar Deenoo, Ghyslain Pelletier, J. Patrick Tooher.
Application Number | 20190104551 16/086880 |
Document ID | / |
Family ID | 58640992 |
Filed Date | 2019-04-04 |
United States Patent
Application |
20190104551 |
Kind Code |
A1 |
Deenoo; Yugeswar ; et
al. |
April 4, 2019 |
METHOD FOR INITIAL ACCESS USING SIGNATURES
Abstract
A method for use in a wireless transmit/receive unit (WTRU) for
initial access using a system signature or signature sequence is
described herein. The WTRU may receive a system signature from at
least one transmission-reception points (TRP) of a plurality of
TRPs. The system signature may be associated with a numerology, a
network slice, a discontinuous transmission (DTX) state, a control
channel characteristic, and/or a network service. The WTRU may then
determine with use of a stored access table a resource selection,
an initial access method of a plurality of initial access methods,
a network slice, a network service, or a group of the at least one
TRP. The WTRU may then receive at least one random access response
(RAR) message from the at least one TRP. The WTRU may then
associate with the at least on TRP based on the received at least
one RAR message.
Inventors: |
Deenoo; Yugeswar; (Chalfont,
PA) ; Pelletier; Ghyslain; (Montreal, CA) ;
Tooher; J. Patrick; (Montreal, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
IDAC HOLDINGS, INC. |
Wilmington |
DE |
US |
|
|
Assignee: |
IDAC HOLDINGS, INC.
Wilmington
DE
|
Family ID: |
58640992 |
Appl. No.: |
16/086880 |
Filed: |
March 30, 2017 |
PCT Filed: |
March 30, 2017 |
PCT NO: |
PCT/US2017/024966 |
371 Date: |
September 20, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62315458 |
Mar 30, 2016 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W 72/0453 20130101;
H04W 48/08 20130101; H04W 74/0833 20130101; H04W 76/28 20180201;
H04W 74/006 20130101; H04W 72/0446 20130101; H04W 4/70 20180201;
H04L 5/0007 20130101 |
International
Class: |
H04W 74/08 20060101
H04W074/08; H04W 72/04 20060101 H04W072/04; H04W 76/28 20060101
H04W076/28 |
Claims
1. A method performed by a wireless transmit/receive unit (WTRU),
the method comprising: receiving, by the WTRU from one or more
transmission-reception points (TRPs) of a plurality of TRPs, a
signature sequence, wherein the signature sequence is related to a
numerology of a network; determining, by the WTRU with use of an
access table, resource selection and an initial access from a
plurality of access procedures that are based on the numerology, or
a group of the one or more TRPs; and receiving, by the WTRU, one or
more random access response (RAR) messages from one TRP in the
group of the one or more TRPs.
2. The method of claim 1 further comprising transmitting, in a
control message, an indication of a selected RAR from the one or
more RAR messages.
3. The method of claim 1, wherein the access table is acquired on a
condition that the WTRU triggered an acquisition of the access
table.
4. (canceled)
5. The method of claim 1, wherein the signature sequence is
associated with a network slice.
6. The method of claim 1, wherein the signature sequence is
associated with a discontinuous transmission (DTX) state.
7.-9. (canceled)
10. The method of claim 1, further comprising: transmitting a
preamble using the received signature sequence.
11. The method of claim 1, further comprising: associating with the
one TRP in the group of the one or more TRPs based on the received
one or more RAR messages.
12. (canceled)
13. A wireless transmit/receive unit (WTRU) configured comprising:
a receiver configured to receive, from one or more
transmission-reception points (TRPs) of a plurality of TRPs, a
signature sequence, wherein the signature sequence is related to a
numerology of a network; a processor configured to determine, with
use of an access table, resource selection and an initial access
from a plurality of access procedures that are based on the
numerology or a group of the one or more TRPs; and the receiver
further configured to receive one or more random access response
(RAR) messages from one TRP in the group of the one or more
TRPs.
14. The WTRU of claim 13 further comprising transmitting, in a
control message, an indication of a selected RAR from the one or
more RAR messages.
15. WTRU of claim 13, wherein the access table is acquired on a
condition that the WTRU triggered an acquisition of the access
table.
16. (canceled)
17. The WTRU of claim 13, wherein the signature sequence is
associated with a network slice.
18. The WTRU of claim 13, wherein the signature sequence is
associated with a discontinuous transmission (DTX) state.
19.-21. (canceled)
22. The WTRU of claim 13, further comprising: a transmitter
configured to transmit a preamble using the received signature
sequence.
23. The WTRU of claim 13, further comprising: the processor
configured to associate the WTRU with the one TRP in the group of
the one or more TRPs based on the received one or more RAR
messages.
24. (canceled)
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application Ser. No. 62/315,458 filed Mar. 30, 2016, the contents
of which is hereby incorporated by reference herein.
BACKGROUND
[0002] Mobile communications are in continuous evolution and are at
the doorstep of its fifth incarnation, 5G. As with previous
generations, new use cases largely contributed in setting the
requirements for the new system. The 5G air interface may at least
enable the following use cases: improved broadband performance
(IBB); industrial control and communications (ICC) and vehicular
applications (V2X); and massive machine-type communications
(mMTC).
[0003] The above uses cases may be translated into the following
requirements for the 5G interface: support for ultra-low
transmission latency (LLC); support for ultra-reliable transmission
(URC); and support for MTC operation (including narrowband
operation).
[0004] One of the goals for the next generation radio access
technology is to achieve improved energy efficiency. Energy
consumption in the radio access network is dominated by always-on
broadcast signaling.
SUMMARY
[0005] A system and method for providing access to a wireless
communication system is disclosed. The system and method include
receiving by a communications device a system signature,
determining via the received system signature one or more
parameters associated with the wireless communication system, and
accessing the wireless communication system using the
communications device based on the one or more parameters.
[0006] A method for use in a wireless transmit/receive unit (WTRU)
for initial access using a system signature or signature sequence
is described herein. The WTRU may receive a system signature from
at least one transmission-reception points (TRP) of a plurality of
TRPs. The system signature may be associated with a numerology, a
network slice, a discontinuous transmission (DTX) state, a control
channel characteristic, and/or a network service. The WTRU may then
determine with use of a stored access table a resource selection,
an initial access method of a plurality of initial access methods,
a network slice, a network service, or a group of the at least one
TRP. The WTRU may then receive at least one random access response
(RAR) message from the at least one TRP. The WTRU may then
associate with the at least on TRP based on the received at least
one RAR message.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] A more detailed understanding may be had from the following
description, given by way of example in conjunction with the
accompanying drawings wherein:
[0008] FIG. 1A is a system diagram of an example communications
system in which one or more disclosed embodiments may be
implemented;
[0009] FIG. 1B is a system diagram of an example wireless
transmit/receive unit (WTRU) that may be used within the
communications system illustrated in FIG. 1A;
[0010] FIG. 1C is a system diagram of an example radio access
network and an example core network that may be used within the
communications system illustrated in FIG. 1A;
[0011] FIG. 2 is a diagram that provides an example of some of the
system transmission bandwidths supported by a 5gFLEX system;
[0012] FIG. 3 is a diagram of an example flexible spectrum
allocation supported by a 5gFLEX system;
[0013] FIG. 4 is a diagram of an example flexible frame structure
for TDD that may be used in a wireless communications system such
as a 5gFLEX system;
[0014] FIG. 5 is a diagram of an example frame structure for FDD
that may be used in a wireless communications system such as a
5gFLEX system;
[0015] FIG. 6 is a diagram of the example assistance modes
available;
[0016] FIG. 7 is a diagram of an example system for initial access
using system signatures or signature sequences;
[0017] FIG. 8 is a flow diagram of an example process for initial
access using system signatures or signature sequences;
[0018] FIG. 9 is a flow diagram of an example process for
detecting/acquiring system information via access tables;
[0019] FIG. 10 is a flow diagram of an example random access
procedure using initial access using system signatures or signature
sequences; and
[0020] FIG. 11 is a flow diagram of an example procedure for
configuration of diverse access methods.
DETAILED DESCRIPTION
[0021] FIG. 1A is a diagram of an example communications system 100
in which one or more disclosed embodiments may be implemented. The
communications system 100 may be a multiple access system that
provides content, such as voice, data, video, messaging, broadcast,
etc., to multiple wireless users. The communications system 100 may
enable multiple wireless users to access such content through the
sharing of system resources, including wireless bandwidth. For
example, the communications system 100 may employ one or more
channel access methods, such as code division multiple access
(CDMA), time division multiple access (TDMA), frequency division
multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrier
FDMA (SC-FDMA), and the like.
[0022] As shown in FIG. 1A, the communications system 100 may
include wireless transmit/receive units (WTRUs) 102a, 102b, 102c,
102d, a radio access network (RAN) 104, a core network 106, a
public switched telephone network (PSTN) 108, the Internet 110, and
other networks 112, though it will be appreciated that the
disclosed embodiments contemplate any number of WTRUs, base
stations, networks, and/or network elements. Each of the WTRUs
102a, 102b, 102c, 102d may be any type of device configured to
operate and/or communicate in a wireless environment. By way of
example, the WTRUs 102a, 102b, 102c, 102d may be configured to
transmit and/or receive wireless signals and may include user
equipment (UE), a mobile station, a fixed or mobile subscriber
unit, a pager, a cellular telephone, a personal digital assistant
(PDA), a smartphone, a laptop, a netbook, a personal computer, a
wireless sensor, consumer electronics, and the like.
[0023] The communications systems 100 may also include a base
station 114a and a base station 114b. Each of the base stations
114a, 114b may be any type of device configured to wirelessly
interface with at least one of the WTRUs 102a, 102b, 102c, 102d to
facilitate access to one or more communication networks, such as
the core network 106, the Internet 110, and/or the other networks
112. By way of example, the base stations 114a, 114b may be a base
transceiver station (BTS), a Node-B, an eNodeB (eNB), a Home Node
B, a Home eNodeB, a site controller, an access point (AP), a
wireless router, and the like. While the base stations 114a, 114b
are each depicted as a single element, it will be appreciated that
the base stations 114a, 114b may include any number of
interconnected base stations and/or network elements.
[0024] The base station 114a may be part of the RAN 104, which may
also include other base stations and/or network elements (not
shown), such as a base station controller (BSC), a radio network
controller (RNC), relay nodes, etc. The base station 114a and/or
the base station 114b may be configured to transmit and/or receive
wireless signals within a particular geographic region, which may
be referred to as a cell (not shown). The cell may further be
divided into cell sectors. For example, the cell associated with
the base station 114a may be divided into three sectors. Thus, in
one embodiment, the base station 114a may include three
transceivers, i.e., one for each sector of the cell. In another
embodiment, the base station 114a may employ multiple-input
multiple-output (MIMO) technology and, therefore, may utilize
multiple transceivers for each sector of the cell.
[0025] The base stations 114a, 114b may communicate with one or
more of the WTRUs 102a, 102b, 102c, 102d over an air interface 116,
which may be any suitable wireless communication link (e.g., radio
frequency (RF), microwave, infrared (IR), ultraviolet (UV), visible
light, etc.). The air interface 116 may be established using any
suitable radio access technology (RAT).
[0026] More specifically, as noted above, the communications system
100 may be a multiple access system and may employ one or more
channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA,
and the like. For example, the base station 114a in the RAN 104 and
the WTRUs 102a, 102b, 102c may implement a radio technology such as
Universal Mobile Telecommunications System (UMTS) Terrestrial Radio
Access (UTRA), which may establish the air interface 116 using
wideband CDMA (WCDMA). WCDMA may include communication protocols
such as High-Speed Packet Access (HSPA) and/or Evolved HSPA
(HSPA+). HSPA may include High-Speed Downlink Packet Access (HSDPA)
and/or High-Speed Uplink Packet Access (HSUPA).
[0027] In another embodiment, the base station 114a and the WTRUs
102a, 102b, 102c may implement a radio technology such as Evolved
UMTS Terrestrial Radio Access (E-UTRA), which may establish the air
interface 116 using Long Term Evolution (LTE) and/or LTE-Advanced
(LTE-A).
[0028] In other embodiments, the base station 114a and the WTRUs
102a, 102b, 102c may implement radio technologies such as Institute
for Electrical and Electronics Engineers (IEEE) 802.16 (i.e.,
Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000,
CDMA2000 1X, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000),
Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), Global
System for Mobile communications (GSM), Enhanced Data rates for GSM
Evolution (EDGE), GSM EDGE (GERAN), and the like.
[0029] The base station 114b in FIG. 1A may be a wireless router,
Home Node B, Home eNodeB, or access point, for example, and may
utilize any suitable RAT for facilitating wireless connectivity in
a localized area, such as a place of business, a home, a vehicle, a
campus, and the like. In one embodiment, the base station 114b and
the WTRUs 102c, 102d may implement a radio technology such as IEEE
802.11 to establish a wireless local area network (WLAN). In
another embodiment, the base station 114b and the WTRUs 102c, 102d
may implement a radio technology such as IEEE 802.15 to establish a
wireless personal area network (WPAN). In yet another embodiment,
the base station 114b and the WTRUs 102c, 102d may utilize a
cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, etc.)
to establish a picocell or femtocell. As shown in FIG. 1A, the base
station 114b may have a direct connection to the Internet 110.
Thus, the base station 114b may not be required to access the
Internet 110 via the core network 106.
[0030] The RAN 104 may be in communication with the core network
106, which may be any type of network configured to provide voice,
data, applications, and/or voice over internet protocol (VoIP)
services to one or more of the WTRUs 102a, 102b, 102c, 102d. For
example, the core network 106 may provide call control, billing
services, mobile location-based services, pre-paid calling,
Internet connectivity, video distribution, etc., and/or perform
high-level security functions, such as user authentication.
Although not shown in FIG. 1A, it will be appreciated that the RAN
104 and/or the core network 106 may be in direct or indirect
communication with other RANs that employ the same RAT as the RAN
104 or a different RAT. For example, in addition to being connected
to the RAN 104, which may be utilizing an E-UTRA radio technology,
the core network 106 may also be in communication with another RAN
(not shown) employing a GSM radio technology.
[0031] The core network 106 may also serve as a gateway for the
WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet
110, and/or other networks 112. The PSTN 108 may include
circuit-switched telephone networks that provide plain old
telephone service (POTS). The Internet 110 may include a global
system of interconnected computer networks and devices that use
common communication protocols, such as the transmission control
protocol (TCP), user datagram protocol (UDP) and the internet
protocol (IP) in the TCP/IP internet protocol suite. The networks
112 may include wired or wireless communications networks owned
and/or operated by other service providers. For example, the
networks 112 may include another core network connected to one or
more RANs, which may employ the same RAT as the RAN 104 or a
different RAT.
[0032] Some or all of the WTRUs 102a, 102b, 102c, 102d in the
communications system 100 may include multi-mode capabilities,
i.e., the WTRUs 102a, 102b, 102c, 102d may include multiple
transceivers, transmitters, or receivers for communicating with
different wireless networks over different wireless links. For
example, the WTRU 102c shown in FIG. 1A may be configured to
communicate with the base station 114a, which may employ a
cellular-based radio technology, and with the base station 114b,
which may employ an IEEE 802 radio technology.
[0033] FIG. 1B is a system diagram of an example WTRU 102. As shown
in FIG. 1B, the WTRU 102 may include a processor 118, a transceiver
120, a transmit/receive element 122, a speaker/microphone 124, a
keypad 126, a display/touchpad 128, non-removable memory 130,
removable memory 132, a power source 134, a global positioning
system (GPS) chipset 136, and other peripherals 138. It will be
appreciated that the WTRU 102 may include any sub-combination of
the foregoing elements while remaining consistent with an
embodiment.
[0034] The processor 118 may be a general purpose processor, a
special purpose processor, a conventional processor, a digital
signal processor (DSP), a plurality of microprocessors, one or more
microprocessors in association with a DSP core, a controller, a
microcontroller, Application Specific Integrated Circuits (ASICs),
Field Programmable Gate Array (FPGAs) circuits, any other type of
integrated circuit (IC), a state machine, and the like. The
processor 118 may perform signal coding, data processing, power
control, input/output processing, and/or any other functionality
that enables the WTRU 102 to operate in a wireless environment. The
processor 118 may be coupled to the transceiver 120, which may be
coupled to the transmit/receive element 122. While FIG. 1B depicts
the processor 118 and the transceiver 120 as separate components,
it will be appreciated that the processor 118 and the transceiver
120 may be integrated together in an electronic package or
chip.
[0035] The transmit/receive element 122 may be configured to
transmit signals to, or receive signals from, a base station (e.g.,
the base station 114a) over the air interface 116. For example, in
one embodiment, the transmit/receive element 122 may be an antenna
configured to transmit and/or receive RF signals. In another
embodiment, the transmit/receive element 122 may be an
emitter/detector configured to transmit and/or receive IR, UV, or
visible light signals, for example. In yet another embodiment, the
transmit/receive element 122 may be configured to transmit and
receive both RF and light signals. It will be appreciated that the
transmit/receive element 122 may be configured to transmit and/or
receive any combination of wireless signals.
[0036] In addition, although the transmit/receive element 122 is
depicted in FIG. 1B as a single element, the WTRU 102 may include
any number of transmit/receive elements 122. More specifically, the
WTRU 102 may employ MIMO technology. Thus, in one embodiment, the
WTRU 102 may include two or more transmit/receive elements 122
(e.g., multiple antennas) for transmitting and receiving wireless
signals over the air interface 116.
[0037] The transceiver 120 may be configured to modulate the
signals that are to be transmitted by the transmit/receive element
122 and to demodulate the signals that are received by the
transmit/receive element 122. As noted above, the WTRU 102 may have
multi-mode capabilities. Thus, the transceiver 120 may include
multiple transceivers for enabling the WTRU 102 to communicate via
multiple RATs, such as UTRA and IEEE 802.11, for example.
[0038] The processor 118 of the WTRU 102 may be coupled to, and may
receive user input data from, the speaker/microphone 124, the
keypad 126, and/or the display/touchpad 128 (e.g., a liquid crystal
display (LCD) display unit or organic light-emitting diode (OLED)
display unit). The processor 118 may also output user data to the
speaker/microphone 124, the keypad 126, and/or the display/touchpad
128. In addition, the processor 118 may access information from,
and store data in, any type of suitable memory, such as the
non-removable memory 130 and/or the removable memory 132. The
non-removable memory 130 and the removable memory 132 may include
any volatile or non-volatile read/write memory. The non-removable
memory 130 may include random-access memory (RAM), read-only memory
(ROM), a hard disk, or any other type of memory storage device. The
removable memory 132 may include but is not limited to a subscriber
identity module (SIM) card, a memory stick, a secure digital (SD)
memory card, and the like. In other embodiments, the processor 118
may access information from, and store data in, memory that is not
physically located on the WTRU 102, such as on a server or a home
computer (not shown). The processor 118 may access information
from, and store data in, an access table stored in any type of
suitable memory, such as the non-removable memory 130 and/or the
removable memory 132. The access table that is stored in any type
of suitable memory, such as the non-removable memory 130 and/or the
removable memory 132, may be received from communication networks,
such as the core network 106, the Internet 110, and/or the other
networks 112, or any of the 3GPP or 5G network entities described
herein.
[0039] The processor 118 may receive power from the power source
134, and may be configured to distribute and/or control the power
to the other components in the WTRU 102. The power source 134 may
be any suitable device for powering the WTRU 102. For example, the
power source 134 may include one or more dry cell batteries (e.g.,
nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel metal hydride
(NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, and
the like.
[0040] The processor 118 may also be coupled to the GPS chipset
136, which may be configured to provide location information (e.g.,
longitude and latitude) regarding the current location of the WTRU
102. In addition to, or in lieu of, the information from the GPS
chipset 136, the WTRU 102 may receive location information over the
air interface 116 from a base station (e.g., base stations 114a,
114b) and/or determine its location based on the timing of the
signals being received from two or more nearby base stations. It
will be appreciated that the WTRU 102 may acquire location
information by way of any suitable location-determination method
while remaining consistent with an embodiment.
[0041] The processor 118 may further be coupled to other
peripherals 138, which may include one or more software and/or
hardware modules that provide additional features, functionality
and/or wired or wireless connectivity. For example, the peripherals
138 may include an accelerometer, an e-compass, a satellite
transceiver, a digital camera (for photographs or video), a
universal serial bus (USB) port, a vibration device, a television
transceiver, a hands free headset, a Bluetooth.RTM. module, a
frequency modulated (FM) radio unit, a digital music player, a
media player, a video game player module, an Internet browser, and
the like.
[0042] FIG. 1C is a system diagram of the RAN 104 and the core
network 106 according to an embodiment. As noted above, the RAN 104
may employ an E-UTRA radio technology to communicate with the WTRUs
102a, 102b, 102c over the air interface 116. The RAN 104 may also
be in communication with the core network 106.
[0043] The RAN 104 may include eNodeBs (eNBs) 140a, 140b, 140c,
though it will be appreciated that the RAN 104 may include any
number of eNodeBs while remaining consistent with an embodiment.
The eNodeBs 140a, 140b, 140c may each include one or more
transceivers for communicating with the WTRUs 102a, 102b, 102c over
the air interface 116. In one embodiment, the eNodeBs 140a, 140b,
140c may implement MIMO technology. Thus, the eNodeB 140a, for
example, may use multiple antennas to transmit wireless signals to,
and receive wireless signals from, the WTRU 102a.
[0044] Each of the eNodeBs 140a, 140b, 140c may be associated with
a particular cell (not shown) and may be configured to handle radio
resource management decisions, handover decisions, scheduling of
users in the uplink and/or downlink, and the like. As shown in FIG.
1C, the eNodeBs 140a, 140b, 140c may communicate with one another
over an X2 interface.
[0045] The core network 106 shown in FIG. 1C may include a mobility
management entity (MME) 142, a serving gateway 144, and a packet
data network (PDN) gateway 146. While each of the foregoing
elements are depicted as part of the core network 106, it will be
appreciated that any one of these elements may be owned and/or
operated by an entity other than the core network operator.
[0046] The MME 142 may be connected to each of the eNodeBs 140a,
140b, 140c in the RAN 104 via an Si interface and may serve as a
control node. For example, the MME 142 may be responsible for
authenticating users of the WTRUs 102a, 102b, 102c, bearer
activation/deactivation, selecting a particular serving gateway
during an initial attach of the WTRUs 102a, 102b, 102c, and the
like. The MME 142 may also provide a control plane function for
switching between the RAN 104 and other RANs (not shown) that
employ other radio technologies, such as GSM or WCDMA.
[0047] The serving gateway 144 may be connected to each of the
eNodeBs 140a, 140b, 140c in the RAN 104 via the S1 interface. The
serving gateway 144 may generally route and forward user data
packets to/from the WTRUs 102a, 102b, 102c. The serving gateway 144
may also perform other functions, such as anchoring user planes
during inter-eNodeB handovers, triggering paging when downlink data
is available for the WTRUs 102a, 102b, 102c, managing and storing
contexts of the WTRUs 102a, 102b, 102c, and the like.
[0048] The serving gateway 144 may also be connected to the PDN
gateway 146, which may provide the WTRUs 102a, 102b, 102c with
access to packet-switched networks, such as the Internet 110, to
facilitate communications between the WTRUs 102a, 102b, 102c and
IP-enabled devices.
[0049] The core network 106 may facilitate communications with
various networks. For example, the core network 106 may provide the
WTRUs 102a, 102b, 102c with access to circuit-switched networks,
such as the PSTN 108, to facilitate communications between the
WTRUs 102a, 102b, 102c and traditional land-line communications
devices. For example, the core network 106 may include, or may
communicate with, an IP gateway (e.g., an IP multimedia subsystem
(IMS) server) that serves as an interface between the core network
106 and the PSTN 108. In addition, the core network 106 may provide
the WTRUs 102a, 102b, 102c with access to the various networks
including the PSTN 108, Internet 110, and other networks 112, which
may include other wired or wireless networks that are owned and/or
operated by other service providers.
[0050] Other networks 112 may further be connected to an IEEE
802.11 based wireless local area network (WLAN) 160. The WLAN 160
may include an access router 165. The access router may contain
gateway functionality. The access router 165 may be in
communication with a plurality of access points (APs) 170a, 170b.
The communication between access router 165 and APs 170a, 170b may
be via wired Ethernet (IEEE 802.3 standards), or any type of
wireless communication protocol. AP 170a is in wireless
communication over an air interface with WTRU 102d.
[0051] Although the embodiments described herein consider 3GPP
specific protocols, the embodiments described herein are not
restricted to a 3GPP system and are applicable to other wireless
systems.
[0052] While not intending to limit the applicability to other
meanings and/or other type of signals, configuration methods, or
logical associations between different user data units, the
following definitions and terms are used herein in support for the
description of the various methods.
[0053] The following abbreviations and acronyms are provided to aid
and enhance the understanding of the embodiments described
herein.
[0054] .DELTA.f Sub-carrier spacing
[0055] 5gFlex 5G Flexible Radio Access Technology
[0056] 5gNB 5GFlex NodeB
[0057] ACK Acknowledgement
[0058] BLER Block Error Rate
[0059] BTI Basic TI (in integer multiple of one or more symbol
duration)
[0060] CB Contention-Based (e.g., access, channel, resource)
[0061] CoMP Coordinated Multi-Point transmission/reception
[0062] CP Cyclic Prefix
[0063] CP-OFDM Conventional OFDM (relying on cyclic prefix)
[0064] CQI Channel Quality Indicator
[0065] CN Core Network (e.g., LTE packet core)
[0066] CRC Cyclic Redundancy Check
[0067] CSG Closed Subscriber Group
[0068] CSI Channel State Information
[0069] D2D Device to Device transmissions (e.g., LTE Sidelink)
[0070] DCI Downlink Control Information
[0071] DL Downlink
[0072] DM-RS Demodulation Reference Signal
[0073] DRB Data Radio Bearer
[0074] EPC Evolved Packet Core
[0075] FBMC Filtered Band Multi-Carrier
[0076] FBMC/OQAM A FBMC technique using Offset Quadrature Amplitude
Modulation
[0077] FDD Frequency Division Duplexing
[0078] FDM Frequency Division Multiplexing
[0079] ICC Industrial Control and Communications
[0080] ICIC Inter-Cell Interference Cancellation
[0081] IP Internet Protocol
[0082] LAA License Assisted Access
[0083] LBT Listen-Before-Talk
[0084] LCH Logical Channel
[0085] LCP Logical Channel Prioritization
[0086] LLC Low Latency Communications
[0087] LTE Long Term Evolution e.g., from 3GPP LTE R8 and up
[0088] MAC Medium Access Control
[0089] NACK Negative ACK
[0090] MC MultiCarrier
[0091] MCS Modulation and Coding Scheme
[0092] MIMO Multiple Input Multiple Output
[0093] MTC Machine-Type Communications
[0094] NAS Non-Access Stratum
[0095] OFDM Orthogonal Frequency-Division Multiplexing
[0096] OOB Out-Of-Band (emissions)
[0097] Pcmax Total available WTRU power in a given TI
[0098] PHY Physical Layer
[0099] PRACH Physical Random Access Channel
[0100] PDU Protocol Data Unit
[0101] PER Packet Error Rate
[0102] PLMN Public Land Mobile Network
[0103] PLR Packet Loss Rate
[0104] PSS Primary Synchronization Signal
[0105] QoS Quality of Service (from the physical layer
perspective)
[0106] RAB Radio Access Bearer
[0107] RACH Random Access Channel (or procedure)
[0108] RAR Random Access Response
[0109] RCU Radio access network Central Unit
[0110] RF Radio Front end
[0111] RNTI Radio Network Identifier
[0112] RRC Radio Resource Control
[0113] RRM Radio Resource Management
[0114] RS Reference Signal
[0115] RTT Round-Trip Time
[0116] SCMA Single Carrier Multiple Access
[0117] SDU Service Data Unit
[0118] SOM Spectrum Operation Mode
[0119] SS Synchronization Signal
[0120] SSS Secondary Synchronization Signal
[0121] SRB Signaling Radio Bearer
[0122] SWG Switching Gap (in a self-contained subframe)
[0123] TB Transport Block
[0124] TBS Transport Block Size
[0125] TDD Time-Division Duplexing
[0126] TDM Time-Division Multiplexing
[0127] TI Time Interval (in integer multiple of one or more
BTI)
[0128] TTI Transmission Time Interval (in integer multiple of one
or more TI)
[0129] TRP Transmission/Reception Point
[0130] TRPG Transmission/Reception Point Group
[0131] TRx Transceiver
[0132] UFMC Universal Filtered MultiCarrier
[0133] UF-OFDM Universal Filtered OFDM
[0134] UL Uplink
[0135] URC Ultra-Reliable Communications
[0136] URLLC Ultra-Reliable and Low Latency Communications
[0137] V2V Vehicle to vehicle communications
[0138] V2X Vehicular communications
[0139] WLAN Wireless Local Area Networks and related technologies
(IEEE 802.xx domain)
[0140] One of the goals for next generation radio access technology
such as 5gFLEX is to achieve improved energy efficiency. Energy
consumption in the radio access network may be due to always-on
broadcast signaling. Reducing mandatory periodic transmissions that
are not directly related to user data transmission is one solution
provided by the embodiments described herein.
[0141] Next generation radio access technology such as 5gFLEX is
also expected to support diverse sets of services in the same
spectrum. Legacy LTE systems may define one initial access method
for example, random access, but in 5G diverse sets of access
methods may be used to handle different use cases including but not
limited to enhanced mobile broadband (eMBB), mMTC, and URLLC.
Mechanisms to handle a diverse set of access methods is another
solution provided by the embodiments described herein.
[0142] The embodiments described herein may be used in deployment
scenarios including but not limited to (1) LTE-assisted 5gFLEX
Aggregation (DC/CA/Offload), (2) LTE-assisted 5gFLEX Transport
Channel(s) (which includes for example, LTE CP, LTE UP, LTE Uu with
one or more 5gFLEX TrCH/Physical channels plugged into LTE Uu),
LTE-based Stand-alone 5gFLEX operation (which includes for example,
LTE CP, LTE L2 at least in part, 5gFLEX PHY), and (3) Stand-alone
5gFLEX operation.
[0143] For LTE-assisted 5gFLEX Aggregation (DC/CA/Offload), the
WTRU may be configured using the LTE Control Plane, for example
with a LTE RRC connection, and using the LTE User Plane, for
example with one or more LTE Uu interfaces. The WTRU may further be
configured to operate with one or more additional 5gFLEX Uu(s)
using the principles of LTE DC, LTE CA or LTE-WLAN offload. This
configuration may be performed by reception of access table(s) from
broadcast or dedicated signaling. Triggers for initial access to
5gFLEX PHY may use similar triggers as for LTE CA/DC/Offload or
other types of triggers.
[0144] For LTE-assisted 5gFLEX Transport Channel(s) (which includes
for example, LTE CP, LTE UP, LTE Uu with one or more 5gFLEX
TrCH/Physical channels plugged into LTE Uu), the WTRU may be
configured for LTE Uu operation using legacy methods. The WTRU may
be further configured with one or more physical layer (control
and/or data) channels for a 5gFLEX Uu of the configuration of the
WTRU. The downlink physical channels may co-exist in the DL carrier
and/or frequency band while the UL carrier may also be common or
separate (e.g., for uplink control channels). From the perspective
of the WTRU configured with one or more 5gFLEX physical channels,
the cell-specific LTE signals/channels may be viewed as holes in
the 5gFLEX map of physical layer resources. Triggers for initial
access to 5gFLEX PHY may use similar triggers as for LTE DL data
arrival and/or LTE UL data arrival or other triggers as 5G
transmission/reception points (TRPs) may not necessarily be
collocated with the LTE eNB (e.g., 5G RRHs).
[0145] For LTE-based Stand-alone 5gFLEX operation (which includes
for example, LTE CP, LTE L2, 5gFLEX PHY), the WTRU may be
configured with components of the LTE control plane (for example,
RRC connection, security, etc.) and with components of the LTE user
plane (for example, EPS RABs, PDCP, RLC). The WTRU may also be
configured with one or more 5G MAC instance(s) each with one or
more 5gFLEX Uu(s). Triggers for initial access may be similar to
the ones of a stand-alone 5gFLEX system or be a variation a
stand-alone 5gFLEX system.
[0146] For stand-alone 5gFLEX operation, the WTRU may be configured
with a 5G control plane and a 5G user plane. 5gFLEX Uu operation
may be addressed in this case.
[0147] The methods and processes described herein may be performed
on any of the devices described herein. In particular, the methods
for initial access using system signatures or signature sequences
may be performed on a WTRU, base station, AP, eNB, 5gNB, any other
device described herein, or any other device that is capable of
operating in a wireless communications system.
[0148] A system and method for providing access to a wireless
communication system, such as a 5gFLEX system, is described herein.
The system and method may include receiving by a communications
device a system signature or signature sequence, determining, via
the received system signature or signature sequence, one or more
parameters associated with the wireless communication system, and
accessing the wireless communication system using the
communications device based on the one or more parameters. The
embodiments described herein may be described using various
wireless technologies including the 5G air interface, 5gFLEX.
However, such descriptions are for exemplary purposes and do not
limit the applicability of the embodiments described herein to
other wireless technologies and/or to wireless technology using
different principles.
[0149] The embodiments described herein may be used in support of
the use cases enabled by the 5G air interface including but not
limited to IBB, ICC, V2X, and mMTC. Support for ultra-low
transmission latency (LLC) may include air interface latency as low
as 1 ms RTT, which may support TTIs between 100 us and 250 us.
Support for ultra-low access latency (for example, time from
initial system access until the completion of the transmission of
the first user plane data unit) may also be supported. At least ICC
and V2X require end-to-end (e2e) latency of less than 10 ms.
[0150] Support for ultra-reliable transmission (URC) may include
transmission reliability that is higher than legacy LTE systems.
The transmission reliability target for URC is 99.999% transmission
success and service availability. Mobility for speed in the range
of 0-500 km/h may also be supported. At least IC and V2X require
Packet Loss Ratio of less than 10e-6.
[0151] MTC operation (including narrowband operation) may also be
supported. The air interface may efficiently support narrowband
operation (for example, using less than 200 KHz), extended battery
life (for example, up to 15 years of autonomy), and minimal
communication overhead for small and infrequent data transmissions
(for example, low data rate in the range of 1-100 kbps with access
latency of seconds to hours).
[0152] OFDM is used as the basic signal format for data
transmissions in LTE and IEEE 802.11. OFDM efficiently divides the
spectrum into multiple parallel orthogonal subbands. Each
subcarrier is shaped using a rectangular window in the time domain
leading to sinc-shaped subcarriers in the frequency domain. OFDMA
uses frequency synchronization and tight management of uplink
timing alignment within the duration of the cyclic prefix to
maintain orthogonality between signals and to minimize intercarrier
interference. Such tight synchronization may also not be
well-suited in a system where a WTRU is connected to multiple
access points simultaneously. Additional power reduction is also
typically applied to uplink transmissions to be compliant with
spectral emission requirements to adjacent bands, in particular in
the presence of aggregation of fragmented spectrum for the WTRU's
transmissions.
[0153] Some of the shortcomings of conventional OFDM (CP-OFDM) may
be addressed by more stringent RF requirements for implementations,
especially when operating using a large amount of contiguous
spectrum not requiring aggregation. A CP-based OFDM transmission
scheme may also lead to a downlink physical layer for 5G that is
similar to that of legacy system with, for example, modifications
to pilot signal density and location.
[0154] Therefore, the 5gFLEX design may focus on other waveform
candidates although conventional OFDM remains a candidate for 5G
systems at least for the downlink transmission scheme. Flexible
radio access for 5G may build upon technologies such as OFDMA and
legacy LTE systems.
[0155] The 5gFLEX downlink transmission scheme may be based on a
multicarrier (MC) waveform characterized by high spectral
containment (i.e. lower side lobes and lower OOB emissions).
Multicarrier modulation waveforms divide the channel into
subchannels and modulate data symbols on subcarriers in these
subchannels. MC waveform candidates for 5G include but are not
limited to OFDM-OQAM and UFMC (UF-OFDM).
[0156] With OFDM-OQAM, a filter is applied in the time domain per
subcarrier to the OFDM signal to reduce OOB. OFDM-OQAM causes very
low interference to adjacent bands, does not need large guard
bands, and does not require a cyclic prefix. OFDM-OQAM may be the
most popular FBMC technique. However, it is sensitive to multipath
effects and to high delay spread in terms of orthogonality thereby
complicating equalization and channel estimation.
[0157] With UFMC (UF-OFDM), a filter is also applied in the time
domain to the OFDM signal to reduce OOB. However, filtering is
applied per subband to use spectrum fragments thereby reducing
complexity and making UF-OFDM more practical to implement. However,
if there are unused spectrum fragments in the band, OOB emissions
in these fragments may remain as high as for conventional OFDM. In
other words, UF-OFDM may improve over OFDM at the edges of the
filtered spectrum and not in the spectral hole.
[0158] The waveforms described herein are used for exemplary
purposes. Accordingly, the embodiments described herein are not
limited to the above waveforms and may be applicable to other
waveforms.
[0159] These waveforms may enable multiplexing signals with
non-orthogonal characteristics (such as different subcarrier
spacing) in frequency and the co-existence of asynchronous signals
without requiring complex interference cancellation receivers and
may facilitate the aggregation of fragmented pieces of spectrum in
the baseband processing as a lower cost alternative to its
implementation as part of the RF processing.
[0160] Co-existence of different waveforms within the same band may
be used, for example, to support mMTC narrowband operation using
SCMA. Another example is supporting within the same band a
combination of different waveforms, such as for example, CP-OFDM,
OFDM-OQAM and UF-OFDM for all aspects and for both downlink and
uplink transmissions. Such co-existence may include transmissions
using different types of waveforms between different WTRUs or
transmissions from the same WTRU, which may be either
simultaneously with some overlap or consecutive in the time
domain.
[0161] Further co-existence aspects may include support for hybrid
types of waveforms, including but not limited to the following:
waveforms and/or transmissions that support at least one of a
possibly varying CP duration (for example, from one transmission to
another), a combination of a CP and a low power tail (for example,
a zero tail), a form of hybrid guard interval using a low power CP
and an adaptive low power tail, and the like. Such waveforms may
support dynamic variation and/or control of further aspects such as
how to apply filtering (for example, whether filtering is applied
at the edge of the spectrum used for reception of any
transmission(s) for a given carrier frequency, at the edge of a
spectrum used for reception of a transmission associated with a
specific spectrum operation mode (SOM), per subband, or per group
thereof).
[0162] The uplink transmission scheme may use the same or a
different waveform as used for downlink transmissions.
[0163] Multiplexing of transmissions to and from different WTRUs in
the same cell may be based on FDMA and TDMA.
[0164] The 5gFLEX radio access design may be characterized by a
very high degree of spectrum flexibility that may enable deployment
in different frequency bands with different characteristics. These
characteristics may include different duplex arrangements, and
different and/or variable sizes of the available spectrum including
contiguous and non-contiguous spectrum allocations in the same or
different bands. The 5gFLEX radio access design may support
variable timing aspects including support for multiple TTI lengths
and support for asynchronous transmissions.
[0165] Both TDD and FDD duplexing schemes may be supported in the
embodiments described herein. For FDD operation, supplemental
downlink operation is supported using spectrum aggregation. FDD
operation supports both full-duplex FDD and half-duplex FDD
operation. For TDD operation, the DL/UL allocation is dynamic; i.e.
the DL/UL allocation may not be based on a fixed DL/UL frame
configuration. Rather, the length of a DL or a UL transmission
interval is set per transmission opportunity.
[0166] The 5G air interface design may enable different
transmission bandwidths on both the uplink and the downlink ranging
from anything between a nominal system bandwidth up to a maximum
value corresponding to the system bandwidth.
[0167] FIG. 2 is a diagram that provides an example of some of the
system transmission bandwidths 200 supported by a 5gFLEX system
that supports methods for initial access using system signatures or
signature sequences in accordance with any of the embodiments
described herein. For single carrier operation, supported system
bandwidths may include at least 5, 10, 20, 40 and 80 MHz. In some
embodiments, supported system bandwidths may include any bandwidth
in a given range (for example, from a few MHz up to 160 MHz).
Nominal bandwidths may have one or more fixed possible values.
Narrowband transmissions of up to 200 KHz may be supported within
the operating bandwidth for MTC devices. It is noted that system
bandwidth 201, as used herein, may refer to the largest portion of
spectrum that may be managed by the network for a given carrier.
For such a carrier, the portion of spectrum that a WTRU minimally
supports for cell acquisition, measurements, and initial access to
the network may be referred to herein as the nominal system
bandwidth 202.
[0168] A WTRU may be configured with channel bandwidths 203, 204,
and/or 205 that are within the range of the entire system
bandwidth. The configured channel bandwidths 203, 204, and 205 of a
WTRU may or may not include the nominal system bandwidth 202 part
of the system bandwidth 201. Bandwidth flexibility may be achieved
by the 5G air interface of FIG. 2 because all applicable sets of RF
requirements for a given maximum operating bandwidth in a band may
be met without the introduction of additional allowed channel
bandwidths for that operating bandwidth due to the efficient
support of baseband filtering of the frequency domain waveform.
Methods to configure, reconfigure and/or dynamically change the
configured channel bandwidths 203, 204, and 205 of a WTRU for
single carrier operation may be supported by the 5G air interface
of FIG. 2 as well as methods to allocate spectrum for narrowband
transmissions within the nominal system bandwidth 202, system
bandwidth 201, or configured channel bandwidths 203, 204, and
205.
[0169] The physical layer of a 5G air interface may also be
band-agnostic and may support operation in licensed bands below 5
GHz as well as operation in the unlicensed bands in the range 5-6
GHz. For operation in the unlicensed bands, LBT Cat 4 based channel
access framework similar to LTE LAA may be supported. Methods to
scale and manage (e.g., scheduling, addressing of resources,
broadcasted signals, measurements) cell-specific and/or
WTRU-specific channel bandwidths for arbitrary spectrum block sizes
may also be supported.
[0170] Downlink control channels and signals may support FDM
operation. A WTRU may acquire a downlink carrier by receiving
transmissions using only the nominal part of the system bandwidth;
i.e. the WTRU may not initially be required to receive
transmissions covering the entire bandwidth that is being managed
by the network for the concerned carrier.
[0171] Downlink data channels may be allocated over a bandwidth
that may or may not correspond to the nominal system bandwidth,
without restrictions other than being within the WTRU's configured
channel bandwidth. For example, the network may operate a carrier
with a 12 MHz system bandwidth using a 5 MHz nominal bandwidth
allowing devices supporting at most 5 MHz maximum RF bandwidth to
acquire and access the system while possibly allocating +10 to -10
MHz of the carrier frequency to other WTRU's supporting up to 20
MHz worth of channel bandwidth.
[0172] FIG. 3 is a diagram of an example flexible spectrum
allocation 300 supported by a 5gFLEX system that supports methods
for initial access using system signatures or signature sequences
in accordance with any of the embodiments described herein. The
system bandwidth 301 may support spectrum allocation with variable
transmission characteristics 302 and the nominal system bandwidth
303. In the example of FIG. 3, the different subcarriers 304 may be
at least conceptually assigned to different modes of operation
(e.g., SOM). Different SOM may be used to fulfill different
requirements for different transmissions. A SOM may include a
subcarrier spacing, a TTI length, and/or one or more reliability
aspects (e.g., hybrid automatic repeat request (HARQ) processing
aspects) and possibly also a secondary control channel. SOM may
refer to a specific waveform or to a processing aspect (e.g.,
support for co-existence of different waveforms in the same carrier
using FDM and/or TDM, or support for coexistence of FDD operation
in a TDD band in a TDM manner or otherwise).
[0173] A WTRU may be configured to perform transmissions according
to one or more SOMs. For example, a SOM may correspond to
transmissions that use at least one of the following: a specific
TTI duration, a specific initial power level, a specific HARQ
processing type, a specific upper bound for successful HARQ
reception/transmission, a specific transmission mode, a specific
physical channel (uplink or downlink), a specific waveform type, or
a transmission according to a specific RAT (for example, legacy LTE
or according to a 5G transmission method). A SOM may also
correspond to a QoS level and/or a related aspect, for example,
maximum/target latency, maximum/target BLER, or another QoS level
or related aspect. A SOM may further correspond to a spectrum area
and/or to a specific control channel or aspect thereof (including
search space, DCI type, etc.). For example, a WTRU may be
configured with a SOM for each of a URC type of service, a LLC type
of service, and a MBB type of service. A WTRU may have a
configuration for a SOM for system access and also for
transmission/reception of L3 control signaling (for example, RRC
signaling) in a portion of a spectrum associated with the system
such as in nominal system bandwidth 303.
[0174] Spectrum aggregation may be supported for single carrier
operation, whereby the WTRU supports transmission and reception of
multiple transport blocks (TBs) over contiguous or non-contiguous
sets of physical resource blocks (PRBs) within the same operating
band. A single TB may also be mapped to separate sets of PRBs.
[0175] Simultaneous transmissions may be associated with different
SOM requirements. Multicarrier operation may also be supported
using contiguous or non-contiguous spectrum blocks within the same
operating band, or across two or more operating bands. Aggregation
of spectrum blocks using different modes (for example, FDD and TDD)
and using different channel access methods (for example, licensed
and unlicensed band operation below 6 GHz) may also be supported.
The multicarrier aggregation of a WTRU may be configured,
reconfigured, or dynamically changed.
[0176] Downlink and uplink transmissions may be organized into
radio frames characterized by a number of fixed aspects (for
example, location of downlink control information (DCI)) and a
number of varying aspects (for example, transmission timing and
supported types of transmissions).
[0177] A basic time interval (BTI) is expressed in terms of an
integer number of one or more symbol(s), where symbol duration may
be a function of the subcarrier spacing applicable to the
time-frequency resource. For FDD, subcarrier spacing may thus
differ between the uplink carrier frequency f.sub.UL and the
downlink carrier frequency f.sub.DL for a given frame.
[0178] A transmission time interval (TTI) may be the minimum time
supported by the system between consecutive transmissions where
each would be associated with different TBs for the downlink
(TTI.sub.DL), for the uplink (UL TRx) excluding any preamble (if
applicable) but including any control information (for example,
downlink control information (DCI) or uplink control information
(UCI)). A TTI may be expressed in terms of integer number of one of
more BTI(s). A BTI may be specific and/or associated with a given
SOM.
[0179] Supported frame durations may include but are not limited to
100 us, 125 us (1/8 ms), 142.85 us (1/7 ms is 2 nCP LTE OFDM
symbols), and 1 ms to enable alignment with the legacy LTE timing
structure.
[0180] FIG. 4 is a diagram of an example flexible frame structure
400 for TDD that may be used in a wireless communications system
such as a 5gFLEX system supporting initial access using system
signatures or signature sequences in accordance with one
embodiment, which may be used in combination with any of the
embodiments described herein. As shown in the example of FIG. 4,
the start of each frame may be indicated by a downlink control
information (DCI) 401a and 401b of a fixed time duration t.sub.dci
412a and 412b preceding any DL transmission portion of each frame
(DL TRx) 402a and 402b for the concerned carrier frequency,
f.sub.UL+DL. The duration of the DL transmission portions 402a and
402b may be based on an integer number of transmit blocks
(TBs).
[0181] In the example of FIG. 4, the DCI 401a may indicate at least
duration t.sub.DL(n) 405a for the DL TRx portion 402a for frame n,
and DCI 401b may indicate at least duration t.sub.DL(n+1) 405b for
the DL TRx portion 402b for frame n+1, in addition to any downlink
assignment(s) and/or any uplink grant(s) indicated by the DCIs 401a
and 401b.
[0182] The frame may also include an UL transmission portion of the
frame (UL TRx) 403a and 403b. The duration of the UL transmission
portions 403a and 403b may be based on an integer number of
transmit blocks (TBs). In the example of FIG. 4, the DCI 401a may
indicate at least duration t.sub.UL(n) 406a for the UL TRx portion
403a for frame n, and DCI 401b may indicate at least duration
t.sub.UL(n+1) 406b for the UL TRx portion 403b for frame n+1. If
the uplink portion of the frame is present as shown in the example
of FIG. 4, a switching gap (SWG) 404a and 404b may precede the
uplink portion of each frame.
[0183] The WTRU may then derive the resulting TTI duration for each
frame based on the DCIs 401a and 401b. As shown in the example of
FIG. 4, the variable duration of each frame may be expressed in
terms of a TTI duration expressed in terms of an integer number of
BTIs. In the example of FIG. 4, the duration of frame n is
expressed in terms of a TTI.sub.n expressed as x*BTI 409a, and the
duration of frame n+1 is expressed in terms of a TTI.sub.n+1
expressed as y*BTI 409b. The example of FIG. 4 also shows the
inter-subframe spacing (ISS) 411.
[0184] For TDD, 5gFLEX may support device-to-device
(D2D)/vehicle-to-everything (V2X)/Sidelink operation in the frame
structure 400 by including respective downlink control and forward
direction transmissions in the DCI and DL TRx portion (if a
semi-static allocation of the respective resources is used).
Alternatively, D2D/V2X/Sidelink operation may be supported in the
frame structure 400 by including respective downlink control and
forward direction transmissions in the DL TRx portion (for dynamic
allocation) and by including the respective reverse direction
transmission in the UL TRx portion of the frame structure 400.
[0185] FIG. 5 is a diagram of an example frame structure 500 for
FDD that may be used in a wireless communications system such as a
5gFLEX system supporting initial access using system signatures or
signature sequences in accordance with another embodiment, which
may be used in combination with any of the embodiments described
herein. The frame structure 500 may include a downlink reference
TTI and one or more TTI(s) for the uplink. As shown in the example
of FIG. 5, the start of the frame may be indicated by a DCI 501a
and 501b of a fixed time duration t.sub.dci. 506a and 506b
preceding any downlink data transmission portion (DL TRx) 502a and
502b for the concerned carrier frequency f.sub.DL. The duration of
the DL transmission portions 502a and 502b may be based on an
integer number of transmit blocks (TBs).
[0186] In the example of FIG. 5, the DCI 501a may indicate the
duration t.sub.DL(n) 507a for the DL TRx portion 502a for frame n,
and DCI 501b may indicate the duration for t.sub.DL(n+1) 507b for
the DL TRx portion 502b for frame n+1. As shown in the example of
FIG. 5, the variable duration of each frame may be expressed in
terms of the downlink reference TTI durations expressed in terms of
an integer number of BTIs. In the example of FIG. 5, the duration
of frame n is expressed in terms of a TTI.sub.DL(n) expressed as
x*BTI 509a, and the duration of frame n+1 is expressed in terms of
a TTI.sub.DL(n+1) expressed as y*BTI 509b.
[0187] The DCI(s) may indicate an offset (t.sub.offset) 505 and the
TTI duration for any applicable uplink transmission(s) that
contains a transport block. Separate DCIs may also be used for the
downlink and uplink directions. In the example, of FIG. 5, the
frame may include an uplink transmission portion (UL TRx) 503a,
503b, and 503c for the concerned carrier frequency fuL. The
duration of the UL transmission portions 503a, 503b, and 503c may
be based on an integer number of transmit blocks (TBs). The start
of an uplink TTI may be derived using the offset (t.sub.offset) 505
applied from the start of the offset) downlink reference frame that
overlaps with the start of the uplink frame. The t.sub.offset 505
may include a timing advance, for example, in cases where UL
synchronization is applicable. In the example of FIG. 5, DCI 501a
may indicate at least duration t.sub.UL(n,0) 508a and t.sub.UL(n,1)
508b for the UL TRx portions 503a and 503b for frame n. DCI 501b
may indicate at least duration t.sub.UL(n+1,0) 508c for the UL TRx
portion 503c for frame n+1. The example of FIG. 5 also shows the
ISS 504.
[0188] For FDD, 5gFLEX may support D2D/V2x/Sidelink operation in
the UL TRx portion of the frame structure 500 by including
respective downlink control, forward direction, and reverse
direction transmissions in the UL TRx portion (dynamic allocation
of the respective resources may be used).
[0189] A scheduling function may be supported in the medium access
control (MAC) layer. Scheduling modes including but not limited to
the following may be used: (1) network-based scheduling for tight
scheduling in terms of resources, timing, and transmission
parameters of downlink transmissions and/or uplink transmissions;
and (2) WTRU-based scheduling for more flexibility in terms of
timing and transmission parameters. For these modes, scheduling
information may be valid for a single or for multiple TTIs.
[0190] Network-based scheduling enables the network to tightly
manage the available radio resources assigned to different WTRUs
such as to optimize the sharing of such resources. Dynamic
scheduling is supported in this mode.
[0191] WTRU-based scheduling enables the WTRU to opportunistically
access uplink resources with minimal latency on an as-needed basis
within a set of shared or dedicated uplink resources assigned
(dynamically or not) by the network. Both synchronized and
unsynchronized opportunistic transmissions are supported. Both
contention-based transmissions and contention-free transmissions
are supported. Support for opportunistic transmissions (scheduled
or unscheduled) may meet the ultra-low latency requirements for 5G
and the power saving requirement of the mMTC use case.
[0192] 5gFLEX may support an association between data available for
transmission and available resources for uplink transmissions.
Multiplexing of data with different QoS requirements within the
same TB may be supported as long as such multiplexing neither
introduces negative impact to the service with the most stringent
QoS requirement nor introduces unnecessary waste of system
resources.
[0193] A transmission may be encoded using a number of different
encoding methods, which may have different characteristics. For
example, an encoding method may generate a sequence of information
units. Each information unit, or block, may be self-contained. For
example, an error in the transmission of a first block may not
impair the ability of the receiver to successfully decode a second
block, and in particular if the second block is error-free and/or
if sufficient redundancy may be found in the second block or in a
different block for which at least a portion was successfully
decoded. Examples of encoding methods also include raptor/fountain
codes whereby a transmission may consist of a sequence of N raptor
codes. One or more such codes may be mapped to one or more
transmission "symbols" in time. A "symbol" may thus correspond to
one or more sets of information bits, for example, one or more
octets. Such encoding may be used to add forward error correction
(FEC) to a transmission whereby the transmission may use N+1 or N+2
raptor codes (or symbols, assuming a one raptor code symbol
relationship) so that the transmission may be more resilient to the
loss of one "symbol," for example, due to interference or
puncturing by another transmission overlapping in time.
[0194] Logical Transport Connectivity may be different than the
logical channel (LCH) used for legacy LTE. An LCH may represent a
logical association between data packets and/or PDUs. Such an
association may be based on such data units being associated with
the same bearer (similar to legacy) and/or being associated with
the same SOM and/or slice. For example, the association may be
characterized by at least one of a chaining of processing
functions, an applicable physical data (and/or control) channel (or
instance thereof), an instantiation of a protocol stack including a
specific portion being centralized (for example, PDCP only or
anything except RF), and/or another portion closer to the edge (for
example, MAC/PHY in the TRP or RF only) that may be separated by a
fronthauling interface. Different access procedures may be
triggered as a function of the type of LCH for which data is
available when the trigger is based on data arrival.
[0195] Logical Channels Grouping (LCG) may be different than the
LCH grouping or characterization used for legacy LTE. An LCG may
consist of a group of LCH using one or more criteria. The criteria
may be that the one or more LCH may have a similar priority level
applicable to all LCHs of the LCG (similar to legacy). The criteria
may also be that the one or more LCH may be associated with the
same SOM or type thereof or the same slice or type thereof. This
association may characterized by at least one of a chaining of
processing functions, an applicable physical data (and/or control)
channel (or instance thereof), an instantiation of a protocol stack
including a specific portion being centralized (for example, PDCP
only, or anything except RF) and/or another portion closer to the
edge (for example, MAC/PHY in the TRP or RF only) that may be
separated by a fronthauling interface.
[0196] A RAN slice may include the RAN functions, transport network
functions, and resources (for example, radio resources and
backhaul/fronthaul resources along with core network
functions/resources required to provide end-to-end services to the
user). The terms RAN slice or slice may be used interchangeably
herein. The transport or core network functions may be virtualized
on a general purpose processor, run as network functions on
specialized hardware, or split between specialized hardware and
general purpose hardware. A PLMN may comprise one or more slices,
wherein each slice is equivalent to a single, common, or general
purpose network of an operator. Each slice may include one or more
SOMs optimized to support various services that the slice offers.
For example, WTRUs served within a slice may have one or more of
the following aspects in common: services and/or QoE requirements
(e.g., ULLRC, eMBB, MMTC), WTRU categories (for example, CAT 0 to M
and beyond, and additional categories may be defined for >6 GHz
to differentiate beamforming capability), coverage requirements
(for example, normal coverage, enhanced coverage), PLMN/operators,
support of a specific Uu interface (for example, LTE, LTE-Evo, 5G
below 6 GHz, 5G above 6 GHz, Unlicensed), and served by same core
network slice.
[0197] A Transport Channel (TrCH) as referred to herein may include
a specific set of processing steps and/or a specific set of
functions applied to the data that may affect one or more
transmission characteristics over the radio interface. Legacy LTE
defines multiple types of TrCHs, including, for example, the
Broadcast Channel (BCH), the Paging Channel (PCH), the Downlink
Shared Channel (DL-SCH), the Multicast Channel (MCH), the Uplink
Shared Channel (UL-SCH), and the Random Access Channel (that
typically does not carry any user plane data). The main transport
channels for carrying user plane data are the DL-SCH and the
UL-SCH, for the downlink and for the uplink, respectively.
[0198] For 5G systems, the augmented set of requirements supported
by the air interface may lead to the support of multiple transport
channels, such as for user and/or control plane data and for a
single WTRU. Accordingly, the term TrCH as used herein may have a
broader meaning than when the term is used in reference to LTE
systems. For example, a transport channel for URLLC such as the
URLLCH, a transport channel for mobile broadband (MBBCH), and/or a
transport channel for machine type communications (MTCCH) may be
defined for downlink transmission (for example, DL-URLLCH, DL-MBBCH
and DL-MTCCH) and for uplink transmissions (for example, UL-URLLCH,
UL-MBBCH and UL-MTCCH). A type of TrCH may correspond to a type of
physical data channel, may be associated with a SOM, may be
associated with a physical control channel, and/or with a specific
set of DCIs. Different access and procedures may be triggered as a
function of the type of TrCH LCH required by the network/WTRU or
for the type of associated priority/QoS level and/or SOM.
[0199] FIG. 6 is a diagram of the example assistance modes 600
available, which may be used in combination with any of the
embodiments described herein. WTRUs may be connected to TRPs either
in standalone mode 609 or assisted mode 610. For example, WTRUs
604a, 604b, and 604c are connected in standalone mode 609, while
WTRUs 611a, 611b, 611c, and 611d are connected in assisted mode
610. The group of cells that require assistance may be called the
assisted layer 603 and the group of cells that provides the
assistance may be called the assistance layer 602.
[0200] In the example of FIG. 6, the following assistance modes are
shown:
[0201] WTRU 611a connected to 5Gflex small cell in sub-6 GHz band
607 assisted by 5Gflex macro cell in sub-6 GHz band 606;
[0202] WTRU 611b connected to 5Gflex small cell in sub-6 GHz band
607 assisted by LTE-Evo macro cell 605;
[0203] WTRU 611c connected to 5Gflex small cell in above-6 GHz band
608 assisted by 5Gflex macro cell in sub-6 GHz band 606;
[0204] WTRU 611d connected to 5Gflex small cell in above-6 GHz band
608 assisted by LTE-Evo macro cell 605;
[0205] WTRU 611e connected to 5Gflex small cell in below-6 GHz band
607 assisted by 5Gflex small cell in above-6 GHz band 608;
[0206] In the example of FIG. 6, the following standalone modes are
shown:
[0207] WTRU 604b connected 612 to 5Gflex small cell in below-6 GHz
band 607 in standalone mode;
[0208] WTRU 604a connected 601 to 5Gflex macro cell in sub-6 GHz
band 606 in standalone mode; and
[0209] WTRU 604c connected 613 to 5Gflex small cell in above-6 GHz
608 band in standalone mode.
[0210] FIG. 7 is a diagram of an example system 700 for initial
access using system signatures or signature sequences, which may be
used in combination with any of the embodiments described herein. A
network may support different numerologies, each associated with a
specific access method tailored for a specific type of service/use
case. Referring to FIG. 7, WTRU 707 may include the elements of
example WTRUs 102 of FIG. 1A, FIG. 1B, and FIG. 1C. WTRU 707 may be
configured to receive and/or detect one or more system signatures
or system signature sequences.
[0211] A system signature may include or comprise a signal
structure using a sequence. The terms system signature, system
signature sequence, signature sequence, and signature may be used
interchangeably herein. These system signatures may be similar to a
synchronization signal, such as LTE PSS or SSS. A system signature
as used herein may be any type of signal received or transmitted by
a WTRU, TRP, any other device described herein, or any other device
capable of operating in a wireless communications system, and a
system signature may be used in any of the embodiments described
herein.
[0212] In the example of FIG. 7, each TRP of a plurality of TRPs
each transmit a system signature. TRPs 705a, 705b, 705c, 705d, and
705e transmit system signature A 701, which may, for example, be
associated with Numerology A and mMTC services. TRPs 704a, 704b,
and 704c transmit system signature B 702, which may, for example,
be associated with Numerology B and Default Access and eMBB
services. TRPs 706a, 706b, and 706c transmit system signature C
703, which may, for example, be associated with Numerology C and
URLLC services. TRPs, such as TRP 704c in the example of FIG. 7,
may be connected to MME 711 via S1-C interface 712 and serving
gateway (S-GW) 710 via S1-U interface 713.
[0213] A node, such as the TRPs and/or WTRU of FIG. 7, may transmit
and/or receive one or more system signature on one or more
frequency and time resources. System signatures may occupy the
entire bandwidth of an operating channel or only a portion of the
bandwidth. System signatures may be transmitted once within a
period or multiple times per window. For example, a burst of a
signal may be transmitted x times in a window and not transmitted
until a next window occurs. The windows may or may not overlap.
System signatures may occupy either a partial OFDM symbol (for
example, transmitted in the guard period or cyclic prefix as a
unique word) or occupy one or more OFDM symbols. Different types of
physical signals may be used as system signatures including but not
limited to the following: synchronization signals, cell or TRP
specific reference signals (for example, CRS), reference signals
that are common to a group of TRPs (TRPG), preambles, a unique
word, a positioning reference signal, other reference signals, bits
in a master information block (MIB), bits in a system information
block (SIB), any other broadcast channel, or a low overhead
physical channel that carries a low number of payload bits. Such a
physical channel may be designed for additional robustness, for
example, with an attached CRC.
[0214] System signatures may be specific to a particular node or
TRP within a given area (for example, by uniquely identifying the
node), or they may be common to a plurality of nodes or TRPs within
an area. A WTRU may identify or distinguish the transmitting node
uniquely from the system signature. A given system signature may be
associated with more than one node, and a WTRU may use the received
system signature to identify/characterize one or more parameters or
operational aspects associated with a group of nodes. For example,
a system signature may be characterized as follows:
[0215] A system signature may be TRP specific and may be used to
identify and/or distinguish TRPs;
[0216] A system signature may be TRPG specific in which a same
system signature for two or more TRPGs within a layer may identify
common access parameters;
[0217] A system signature may be layer specific and may
differentiate a macro layer from a small cell layer;
[0218] A system signature may be WTRU specific such as for use in
D2D operation;
[0219] A system signature may be relay specific such as for use in
relay operation;
[0220] A system signature may be SOM/slice specific. Each SOM/Slice
may carry its own system signature. In one example, the system
signature associated with the SOM/slice may be transmitted using
the radio resources (time/frequency resources) and/or parameters
(for example, numerology, TTI, CP etc.) specific to that
SOM/slice.
[0221] Each system signature may be composed of different parts
called sub-signatures. For example, one sub-signature may be
antenna port specific, TRP specific, SOM specific, or specific to
plurality of TRPs, etc. Alternatively or additionally, a WTRU may
receive more than one distinct system signature from the
transmitter (TRP or another WTRU).
[0222] Different types of system signatures may be identified
and/or distinguished by the format of the signals used as
signatures. For example, synchronization signals may be used as
layer specific system signatures, whereas positioning reference
signals may be used as TRP specific reference signals. Different
types of system signatures may be defined and/or transmitted in
order to support different WTRU capabilities. For example, WTRUs
under normal coverage may receive the whole system signature,
whereas WTRUs with enhanced coverage requirements and/or with
limited RF bandwidth capability may receive a sub-signature of the
whole signature and obtain partial information associated with the
received sub-signature. Different sub-signatures of system
signatures may be associated with a different periodicity or
repetition factor.
[0223] Different sub-signatures and/or distinct system signatures
may have a predefined linkage between them. The linkage may be
defined in terms of one or more of the following: a timing relation
(for example, symbols, subframes, etc.), a frequency relation (for
example, subcarrier mapping, RB offset, etc.), a spatial relation
(for example, mapped to different beams or different types of beams
such as wide beams or narrow beams), aspects of the signal itself
(for example, sequence number, orthogonal code, signal structure
used, repetition number), and a different antenna port (for
example, TRP specific system signatures from antenna port x and
TRPG specific system signatures from antenna port y). A WTRU may
determine one or more system parameters or a configuration using
the linkage between system signatures and/or sub-signatures.
[0224] A WTRU may determine the placement of system signatures in
the frame structure and/or resource grid (for example, in time
and/or frequency resources) using a predefined configuration.
Alternatively, the placement of a system signature within the frame
structure and/or resource grid may be flexible to avoid
interference and to enable forward compatibility. The WTRU may
determine this flexible placement from a cell specific
configuration or in relation to other signals/channels or provided
by an assistance layer (for example, LTE layer) or using a blind
detection within a time window. Detection of one signature may
enable detection of other signatures associated with the same
transmitting node (for example, TRP and/or WTRU).
[0225] Referring to FIG. 7, WTRU 707 may support multiple services
such as mMTC, eMBB, and URLLC, access methods in support of the
multiple services, and multi-connectivity. WTRU 707 may receive
system signature A 701, system signature B 702, and system
signature C 703 and then determine one or more parameters
associated with a network based on each system signature. For
example, WTRU 707 may derive an index from each system signature
and may use it to retrieve associated parameters, which may for
example be retrieved from an access table stored in the WTRU. For
example, WTRU 707 may use the received power associated with the
system signature for open-loop power control, which may be used for
the purpose of setting the initial transmission power if WTRU 707
determines that it may access and/or transmit to the system using
applicable resources of the system. In another example, WTRU 707
may use the timing of the received system signature or signature
sequence for the purpose of setting the timing of a transmission
such as a preamble on a PRACH resource if WTRU 707 determines that
it may access and/or transmit to the system using applicable of the
system.
[0226] WTRU 707 may be configured with a list of one or more
entries, which may be referred to herein as an access table. The
access table may be stored in the memory of WTRU 707 as described
above, and the access table may be indexed whereby each entry is
associated with a system signature and/or to a sequence thereof.
The entries may be parameters for each system signature. Such
entries may include but are not limited to an access method (for
example, PRACH) numerology aspects (for example, TTI duration), and
TRP/G-specific control channel information. Based on this index, an
entry in the access table may be associated with a plurality of
nodes or TRPs. The WTRU may receive the access table by means of a
transmission as described above. This received transmission may use
dedicated resources, which may for example be by RRC configuration
and/or by means of a transmission using broadcasted resources. When
using broadcasted resources, the periodicity of the transmission of
an access table may be relatively long (for example, up to 10240
ms), and it may be longer than the periodicity of the transmission
of a signature (for example, in the range of 100 ms). An access
table as referred to herein may comprise any type of system
information received by WTRU 707 for any of the purposes described
herein.
[0227] The access table may provide initial access parameters for
one or more areas. Each entry in the access table may provide one
or more parameters necessary for performing an initial access
procedure with the system. These parameters may include at least
one set of one or more random access parameters, which may include
but are not limited to applicable physical layer resources in time
and/or frequency (for example, PRACH resources), an initial power
level, and physical layer resources for reception of a response.
These parameters may further include access restrictions, which may
include but are not limited to Public Land Mobile Network (PLMN)
identity and/or CSG information. These parameters may further
include routing-related information such as the applicable routing
area(s).
[0228] WTRU 707 may have data available for transmission associated
with a specific service, determine by measurements the detected
system signatures, determine the access configuration applicable to
the service, and perform a corresponding access procedure using
system information associated with the determined access table
entry. WTRU 707 may then receive at least one random access
response (RAR) such as RAR 708 or 709 and establish a Uu connection
with the system.
[0229] FIG. 8 is a flow diagram of an example process for initial
access using system signatures or signature sequences 800 that may
be performed in the example system 700 described above and used in
combination with any of the embodiments described herein. While
each step of the process 800 in FIG. 8 is shown and described
separately, multiple steps may be executed in a different order
than what is shown, in parallel with each other, or concurrently
with each other. The process of FIG. 8 is performed by a WTRU for
exemplary purposes, but it may also be performed by any node
operating in a wireless communications system such as a TRP, eNB,
5gNB, AP, or base station. In the example of FIG. 8, a WTRU, via
the transceiver or receiver of the WTRU as described above, may
receive a system signature 801 from at least one TRP of a plurality
of TRPs. The system signature may be associated with any of the
parameters and characteristics described above. For example, the
received system signature may be associated with a numerology, a
network slice, a discontinuous transmission (DTX) state, a control
channel characteristic, or a network service.
[0230] The WTRU may then determine, with use of a stored access
table, a resource selection, an initial access method of a
plurality of access methods that are specific to the numerology
associated with the system signature, a network slice, a network
service, and/or a group of the at least one TRP 802. During this
step, the WTRU may measure, read, and/or decode the received system
signature and perform one or more actions related to a specific
aspect of the system signatures. The relation between different
sub-signatures, different distinct system signatures, and/or types
of signatures sequences may convey one or more aspects of the
system configuration. The relation may be in the time domain (for
example, symbols or an offset) and/or frequency domain (for
example, subcarriers or resource blocks (RBs)). The relation may
also include properties of the system signature (for example, type,
sequence number, or the root sequence). Referring to FIG. 8, the
WTRU may then receive at least one RAR message from the at least
one TRP 803.
[0231] During the procedure described in FIG. 8, the WTRU may
determine system operation/configurations from the received system
signatures including but not limited to the following:
[0232] The WTRU may determine a logical area with one or more
common aspects/properties. The WTRU may assume that a group of TRPs
with the same system signature uses a common system configuration
(for example, initial access parameters). The group of TRPs may
belong to the same signature area or common SIB area within which
the WTRU may not reacquire the system information upon TRP change.
In some embodiments, the WTRU may see the group of TRPs as a single
TRP or a logical cell. The WTRU may assume that the group of TRPs
with the same system signature is associated with the same central
unit. The WTRU may for example perform layer 2 re-establishment
within the TRPs associated with the same central unit instead of
layer 3 re-establishment.
[0233] The WTRU may determine a pointer to an entry in a global
system information table. The WTRU may apply the system information
(for example, initial access parameters including a PRACH
configuration, etc.) in the access table associated with or indexed
by that system signature or parts of the system signature. Also,
when the WTRU no longer receives a system signature or parts of a
system signature, the WTRU may cease to use the current system
information associated with that system signature or parts of the
system signature.
[0234] The WTRU may determine a mapping to a pre-defined broadcast
RNTI. The WTRU may start to monitor control channels for a
pre-defined broadcast RNTI associated with that system signature.
The broadcast RNTI may then be used to schedule system information
and/or an access table associated with that system signature.
[0235] The WTRU may determine support of a service (for example,
eMBB, MMTC, ULLRC) or parts of a system signature or a group of
reserved system signature sequences that may indicate support of
specific service. For example, system signature 1 may indicate
support of eMBB, signature 2 may indicate support of MMTC, and
signature 3 may indicate support for ULLRC. Alternatively, a
relation between system signatures or parts of system signatures
may convey the same information.
[0236] The WTRU may determine support of a SOM by using a system
signature that may be associated with a plurality of SOMs. The
mapping between a SOM and a system signature may be pre-defined or
indicated as a part of the access table information. The WTRU may
determine the presence of one or more SOMs within the frame
structure based on the presence of one or more system signatures
associated with those SOMs.
[0237] The WTRU may determine the DTX state of the network. Each
TRP in the network may be in one of the various DTX states or
visibility levels. For example, completely OFF, transmitting only
system signatures, CRS is OFF, CRS is ON, periodic transmission of
access tables, on-demand transmission of access tables,
transmitting access tables for high priority services (for example,
emergency calls), etc. The WTRU may determine the DTX state of the
TRP from the system signatures transmitted by the TRP. One or more
system signatures may not directly provide system information, and
rather they may point to specific UL resources that may be used to
activate the system information. The WTRU may request the
transmission of access tables using those UL resources. In one
embodiment, WTRUs may be configured to report the TRPs in DTX (for
example, using reserved system signatures). The network may
determine the activation of TRPs based on a number of WTRU
reports.
[0238] The WTRU may determine paging via system signatures.
Pre-defined system signatures may be used for the paging procedure.
This may include the presence of a paging message for one or more
WTRUs to be indicated via a pre-defined system signature. Such an
indication may be of different levels, which may be for example a
frame level or subframe level. Time/frequency resources for actual
paging message transmission may be indicated via a predefined
signature, and such resources may, for example, be defined in the
access table. UL time/frequency resources for a paging
response/preamble transmission may be indicated via a predefined
system signature, and such resources may be defined in the access
table.
[0239] The WTRU may determine an indication of an association with
a specific node in the assistance layer. The WTRU may consider one
or more TRPs in an assisted layer transmitting same system
signatures to be associated with the same node in the assistance
layer. For example, a group of 5Gflex TRPs transmitting a same
reference signal may be associated with the same LTE-Evo macro eNB.
The WTRU may determine the specific LTE-Evo macro eNB.
[0240] The WTRU may determine an indication of a control channel
characteristic/property that may be used. The WTRU may determine
one or more of the following characteristics/properties associated
with the control channel from the system signature:
[0241] Type of control channel: the WTRU may determine the type of
control channel based on the system signature. For example, the
WTRU may determine the presence of a control channel associated
with more than one TRP based on the presence of a predefined system
signature. Similarly, the WTRU may determine the presence of a TRP
specific control channel based on the presence of a TRP specific
system signature. The WTRU may determine the presence of a
SOM/slice specific control channel based on the presence of a
system signature specific to that SOM/slice. The WTRU may determine
whether the control channel is beamformed or not based on a
presence of a predefined system signature. The WTRU may determine
the presence of an enhanced coverage control channel (for example,
with repetition in time and/or frequency) based on the presence of
a pre-defined system signature.
[0242] Location of the control channel: WTRU may obtain the
location of the control channel based on the relative location of
the system signature. For example, the control channel may be
placed at a predefined offset in terms of time (for example,
symbols) and/or frequency (for example, sub-carrier offset, RB
offset, etc.)
[0243] Length/size/bandwidth of the control channel: the WTRU may
determine the size of the control channel (for example, in terms of
a number of OFDM symbols) as a function of the system signature.
For example, a predefined mapping may exist between the system
signature sequence and a number of OFDM symbols carrying the
control channel. Similarly, the WTRU may determine the bandwidth of
the control channel either explicitly based on a pre-defined system
signature or implicitly based on resources occupied by the system
signature.
[0244] The WTRU may determine an identity related to the TRP or
TRPG. The WTRU may identify and/or distinguish a TRP from other
TRPs based on the received system signature. A WTRU may identify
two or more TRPs being part of the same group based on the presence
of a common system signature. The WTRU may identify and/or
distinguish a TRPG from other TRPGs based on the received system
signature. The WTRU may consider a TRP belonging to two or more
TRPGs when it receives two or more TRPG specific system signatures
from the same TRP. In some embodiments, a system signature may
comprise two or more parts, for example a first part that is TRPG
specific and a second part that is TRP specific.
[0245] The WTRU may determine a specific network slice wherein each
RAN slice is associated with a set of radio resources, which may be
dedicated or shared with other RAN slices. The WTRU may identify
the parts of radio resources associated with a specific RAN slice
based on the presence of a system signature associated with that
slice. In one example, the WTRU may determine the bandwidth
allocated to a specific RAN slice based on the bandwidth occupied
by the system signature associated with that slice or based on a
function of system signature sequence associated with that slice.
The WTRU may determine if the one or more subframes and/or TTIs
and/or OFDM symbols are associated with a specific RAN slice based
on the presence of a predefined system signature in those subframes
and/or TTIs and/or OFDM symbols. The WTRU may obtain the mapping
between the system signatures and associated RAN slice, which may
be for example, obtained from an access table or a WTRU specific
configuration. Similar mechanisms may be used to associate a SOM or
a signal structure with a system signature.
[0246] The WTRU may determine a specific numerology. This may
include situations where the WTRU determines one or more parameters
associated with the numerology as a function of the system
signature. For example, the one or more parameters associated with
the numerology may include but are not limited to: TTI length,
number of symbols per TTI, bandwidth, subcarrier spacing, and
cyclic prefix. In one example, a set of supported or allowed
numerology configurations may be predefined and mapped to unique
system signatures using an access table.
[0247] The WTRU may determine a specific frame structure that may
be used. For example, the WTRU may determine the duplex mode or a
frame structure type based on the received system signature. For
example, a predefined system signature may be reserved to indicate
one of TDD duplex mode, FDD duplex mode, half duplex mode, or full
duplex mode, etc. The WTRU may additionally determine the type of
one or more physical channels within a frame structure as a
function of the presence of predefined system signatures. For
example, a first symbol in a subframe may carry a signature that
describes the rest of the frame, whether the frame is almost blank
or if the frame is self-contained (i.e. there is support for
transmissions in both the uplink and downlink multiplexed in time
within the same subframe) and a specific format of the
self-contained frame (i.e. DL control and/or data followed by UL
control and/or data, UL data and/or control followed by DL control
and/or data, etc.). Similarly, the WTRU may determine the subframe
number, slot number, system frame number, etc. as a function of the
system signature.
[0248] The WTRU may determine an indication of the network
capabilities/features that may be used. For example, in legacy
systems, the WTRU may be required to decode system information to
determine the network capability, i.e. if the network supports one
or more features. In next generation systems, the WTRU may directly
determine one or more network capabilities based on the presence of
one or more system signatures. This may reduce the latency and
overhead, as the WTRU may not be required to receive and decode the
system information from each TRP. For example, predefined system
signatures may be reserved to indicate support for eMBMS, D2D,
above 6 GHz carrier, etc. Additionally, a first group of system
signatures may be reserved to indicate the network support of an
initial set of 5G features (for example, phase 1) and a second
group of signatures may be reserved to indicate network support of
an extended set of 5G features (for example, phase 2). In one
example, WTRUs with phase 2 capability may perform preferential
access towards TRPs with the second group of signatures.
[0249] The WTRU may determine a specific deployment or mode of
operation that may be used. The WTRU may distinguish between the
LTE-assisted 5GFlex transport channels and the standalone 5GFlex
operation based on system signatures. Predefined system signatures
may be placed in an LTE frame structure to indicate the presence of
one or more 5GFlex physical channels. Similarly, a different set of
system signatures may indicate a standalone 5GFlex operation. WTRU
logic to perform initial access may be a function of the system
signatures that are received within a frame. The WTRU may
differentiate between a macro TRP and a low power TRP based on the
predefined system signature transmitted from the TRPs.
[0250] The WTRU may determine the suitability of the TRP or TRPG.
The WTRU may determine the suitability of a TRP or group of TRPs
using a quality metric based on measurements performed using a
system signature. Such measurements may be used for selection of
TRP/TRPGs for initial access, for handover, or to perform idle mode
paging monitoring.
[0251] The WTRU may determine a specific version (with respect to a
predefined set of information) of system information that may be
used. Each system signature may be associated with a predefined set
of system information. Upon reception of such a system signature,
the WTRU may apply the associated configuration in the system
information.
[0252] The WTRU may determine the size and the format of the
initial access message (e.g., msg1, msg3 etc.) as function of a
system signature.
[0253] The WTRU may determine that the timing of system signatures
may be used as a DL timing reference.
[0254] The WTRU may determine that the received power of system
signatures may be used as DL pathloss references.
[0255] The WTRU may determine the location of an access table based
on the received system signature. For example, the WTRU may
determine the presence and format of a data channel carrying the
access table based on the system signature. The WTRU may not need
to know or decode the control channel in order to receive the
access table information. The access table information may be, for
example, transmitted with a predefined MCS. In one example, the
WTRU may determine the redundancy version for the access table
transmission using the received system signature.
[0256] The WTRU may determine linked bands/DL/UL frequencies (for
example, the relation between system signature and placement and
bands of operation).
[0257] The information contained in the transmission of system
information may be structured in a specific manner. For example,
such information may be received as a list of elements. Each
element may represent a modular element, for example, in the access
table. System information in the access table may be grouped into
different sub-tables.
[0258] The information in such elements may be grouped based on
characteristics including but not limited to the following:
[0259] Specific to a physical node: for example, a TRP specific
sub-table, TRPG specific sub-table. For example, the WTRU may
determine that parameters associated with one such element may be
associated with the configuration a distinct and/or dedicated MAC
instance.
[0260] Specific to a RAN slice: for example, the WTRU may determine
that parameters associated with one such element may be associated
with the configuration and/or availability of one or more specific
type(s) of processing (for example, L1, L2) and/or a specific type
and/or level of supported QoS.
[0261] Specific to a service (eMBB, ULLRC, mMTC): for example, the
WTRU may determine that parameters associated with one such element
may be associated with the configuration and/or availability of one
or more specific type(s) of control channel, physical data channel
(uplink and/or downlink), and/or type of supported QoS.
[0262] Specific to a SOM: for example, the WTRU may determine that
parameters associated with one such element may be associated with
the configuration and/or availability of one or more specific
type(s) and/or set of physical resources.
[0263] Specific to a feature/capability (for example, MBMS, D2D,
and the like): for example, the WTRU may determine that parameters
associated with one such element may be associated with the
configuration and/or availability and/or support for one or more
specific types of (for example, WTRU-related) capabilities or
combinations thereof. For example, the WTRU may determine that one
or more sets of features are supported by the network using the
associated access parameters.
[0264] Specific to a layer (for example, macro sub-table, small
cell sub-table): for example, the WTRU may determine that
parameters associated with one such element may be associated with
the configuration and/or availability and/or support for one or
more specific types of radio access method(s), which for example,
may be based on system information broadcasts and RRC connectivity,
signature-based access, or other methods.
[0265] Specific to a component carrier (Pcell sub-table, PScell
sub-table, Scell sub-tables): for example, the WTRU may determine
that parameters associated with one such element may be associated
with the configuration and/or availability and/or support for one
or more specific types of aggregation of radio resources. For
example, an access method whereby the outcome of the L1 access (for
example, preamble transmission and/or random access) may result in
a plurality of associations each with different carriers and/or
TRPs.
[0266] Group IEs: Group IEs that are cell specific separately from
IEs that are layer specific (or common to more than one TRP).
[0267] Specific to a mobility set and/or an access set (for
example, to a group of one or more TRPs that share at least some
aspects): such aspects may include procedures and/or functions such
as, for example, support for coordinated scheduling, COMP, carrier
aggregation, MBMS area, common access rights, seamless mobility
within TRPs of such a group, common security context, WTRU context
availability/sharing for all TRPs of such a group, and the like.
For example, this may be applicable when all TRPs in a set are
controlled by the same central entity and/or are connected to each
other and/or to the central control entity by interfaces enabling
such coordination (for example, an ideal interface). For example,
the WTRU may determine that parameters associated with one such
element may be associated with the configuration and/or
availability of one or more specific procedure(s), for example,
such as L1/PHY mobility.
[0268] Specific to a type of radio access technology (for example,
LTE, 5gFLEX): for example, the WTRU may determine that parameters
associated with one such element may be associated with the
configuration and/or availability and/or support for one or more
specific types of radio access and/or access methods. For example,
the WTRU may determine that the associated radio access procedure
uses legacy LTE methods (or an evolution thereof) for standalone
access. For example, the WTRU may determine that the associated
radio access procedure uses the 5gFLEX procedures for standalone
access. For LTE CP/PHY+5gFLEX PHY superposition, DC or CA, for
example, the WTRU may determine that the associated radio access
procedure uses legacy LTE methods (or an evolution thereof) such
that the WTRU may first establish an RRC Connection for the
subsequent configuration of one or more 5gFLEX TrCH(s) and/or
physical data channel(s). The WTRU may possibly further determine
whether such a configuration is for the same carrier (for example,
by superposition of additional physical channels), a different
carrier (for example, by carrier aggregation principles) and/or
separate MAC instances (for example, using different schedulers by
dual connectivity principles). For LTE CP+5gFLEX PHY substitution,
for example, the WTRU may determine that the associated radio
access procedure uses legacy LTE methods (or an evolution thereof)
for the L3/RRC Control Plane following an access using the 5gFLEX
procedures, for example, based on 5gFLEX access tables, signature
detection, transmission over 5gFLEX TrCH(s), and/or physical
access/data channel(s). These elements may be further grouped
together respectively. Such groups may be further separated from
each other.
[0269] FIG. 9 is a flow diagram of an example process for
detecting/acquiring system information via access tables 900 that
may be performed in the example system 700 described above and used
in combination with any of the embodiments described herein. While
each step of the procedure 900 in FIG. 9 is shown and described
separately, multiple steps may be executed in a different order
than what is shown, in parallel with each other, or concurrently
with each other. The process of FIG. 9 is performed by a WTRU for
exemplary purposes, but it may also be performed by any node
operating in a wireless communications system such as a TRP, eNB,
5gNB, AP, or base station. In the example of FIG. 9, a WTRU, via
the transceiver or transmitter of the WTRU as described above, may
trigger a procedure to acquire or reacquire at least one access
table 901 based on a received system signature, an aspect
associated with the validity of a previously received access table,
for pre-acquisition of an access table, upon power up, and/or upon
expiration of a timer.
[0270] For example, the WTRU may receive a system signature
periodically to stay up to date with the system configuration. The
WTRU may trigger a procedure to acquire or reacquire the at least
one access table 901 when the WTRU receives an unknown system
signature. For example, the WTRU may declare a received system
signature as unknown when the WTRU does not have a valid access
table associated with the system signature stored in its memory. If
the WTRU receives an unknown system signature, it may perform
actions including but not limited to the following: reporting the
unknown system signature to the currently associated TRPs or TRPGs
and/or reporting the unknown system signature to the assistance
layer, triggering an on-demand access table transmission procedure,
or considering the unknown system signature as being from
inaccessible transmitter.
[0271] In another example, the WTRU may trigger a procedure to
acquire or reacquire the at least one access table 901 when the
WTRU receives a reserved signature, which is special signature that
may be reserved to indicate a change in the access table.
[0272] In another example, the WTRU may trigger a procedure to
acquire or reacquire the at least one access table 901 when the
WTRU determines that a measurement related and/or associated with a
system signature and/or to the reception of an access table is no
longer of sufficient quality. In this example, the validity of an
access table may be a function of a reception quality of the
transmitted access table.
[0273] In another example, a WTRU may trigger a procedure to
acquire or reacquire the at least one access table 901 after
determining that one or more entries in the stored access table are
no longer valid. The validity of the access table may be determined
by a change in a value tag when the value tag associated with the
stored access table information is different from the network
broadcasted value tag. The value tag may be defined at different
levels of granularity. The value tag may be associated with a whole
access table, and/or sub-table, and/or group of entries, and/or a
specific entry in the table. When reacquiring an access table, the
WTRU may reacquire only the relevant portion of the access table
according to the granularity of the value tag. The WTRU may receive
the value tag used to determine the validity of the access table in
several ways, including but not limited to the following: as a
separate entry in the access table, in a MAC control element, in a
physical channel reserved to carry value tag information, using one
or more properties of the synchronization channel or demodulation
reference signal, and/or in a paging message.
[0274] In another example, a WTRU may trigger a procedure to
acquire or reacquire the at least one access table 901 via
pre-acquisition of the access table. In this example, the WTRU may
pre-acquire the access table associated with one or more system
signatures, before actually receiving the one or more system
signatures. WTRU may pre-acquire the access table using one or more
of the following methods:
[0275] The WTRU may determine the need to acquire or re-acquire the
access table based on its location and proximity to one or more
system signatures. For example, the WTRU may be configured with a
list of system signatures that are active in a geographical
location defined by the location area, routing area, RAN area, or
relation based on positioning reference signals, or other means to
obtain location information (for example, GPS/GNSS).
[0276] As part of handover information, the WTRU may receive a list
of access tables from the source cell, which may correspond to one
or more system signatures in the target cell.
[0277] The WTRU may receive parts of access table information
during a connection release procedure. The WTRU may use the access
table information in the idle mode for example.
[0278] The WTRU may pre-acquire access table information associated
with one or more system signatures that are turned off. These
system signatures may correspond to one more TRPs in a DRX state
and/or one or more inactive services within the active TRPs.
[0279] In another example, a WTRU may trigger a procedure to
acquire or reacquire the at least one access table 901 upon power
up. In this example, the WTRU may acquire the access table upon
power up when, a stored access table is empty, and/or the WTRU does
not have a valid access table associated with the received
signature.
[0280] In another example, a WTRU may trigger a procedure to
acquire or reacquire the at least one access table 901 upon expiry
of a timer. In this example, the WTRU may acquire or re-acquire the
access table upon expiry of a periodic refresh timer.
[0281] After triggering a procedure to acquire or reacquire the at
least one access table 901, the WTRU may receive the at least one
access table 902. The WTRU may detect and receive the at least one
access table that includes system information using several
methods. For example, access table transmissions may be associated
with a separate logical channel and be mapped to a transport
channel that may include one or more of the following transmission
characteristics:
[0282] The periodicity of the transmission of an access table may
be relatively long (for example, up to 10240 ms). The periodicity
also may be longer than the periodicity of the transmission of a
system signature (for example, in the range of 100 ms).
[0283] Different parts of the access table (for example,
sub-tables) may be transmitted with different periodicity based on
the order of importance to regular WTRU operation. For example, a
sub-table carrying information regarding the accessibility/PLMN
information or initial access information may be transmitted more
frequently than others.
[0284] Various modes of access table transmission may also be
implemented. The WTRU may receive the access table information
associated with an assisted layer from the assistance layer. For
example, the WTRU may receive the access table information for a
5gFLEX small cell layer from a LTE-Evo macro cell using methods
including but not limited to the following: a type of system
information in the assistance layer (for example, a SIB in the
macro cell for the group of small cells/TRPG), a SC-PTM mode in the
assistance layer, and/or a shared data channel (e.g., PDSCH) as
dedicated WTRU information. In another example, the WTRU may
combine transmissions from the assistance layer and assisted layer
to form the complete access table. For example, WTRU may receive a
baseline access table from the LTE macro layer and only the delta
changes on top of the baseline table from the 5gFLEX small cell
layer.
[0285] For multi-TRP coordinated broadcast mechanisms (single
frequency mode), the WTRU may receive the access table information
from more than one TRP on the same time/frequency resource. The
WTRU may consider such access table information being applicable to
more than one TRP, which may be over a geographical region. A
separate antenna port may be defined for access table transmission.
The WTRU may perform layer mapping and precoding assuming that a
single antenna port is used. The access table transmissions may use
an extended cyclic prefix. Multi-TRP coordinated broadcast channel
may be associated with a dedicated reference signal that is
different from a cell specific reference signal.
[0286] For TRP specific transmission, an access table may be
transmitted within the coverage of a single cell/TRP using a shared
or common data channel or broadcast channel. The downlink control
messages corresponding to access table transmissions may be
identified by a reserved RNTI. For example, at least two RNTIs may
be used to identify different sub-tables of an access table.
Alternatively, the access table may be transmitted using a Single
Cell Point to Multipoint transmission (SC-PTM) within a TRP.
[0287] A hybrid mechanism may also be implemented for transmission
of an access table. The WTRU may receive RAN area/layer specific
parts of an access table using a multi-TRP mechanism, and cell
specific parts of an access table may be received via a broadcast
or unicast mechanism. For example, the WTRU may differentiate the
modes of transmission as a function of system signatures. For
example, different system signatures may be reserved for a specific
mode of access table transmission.
[0288] Access table transmissions may be multiplexed with other
logical channels in the same subframe/TTI. Access table
transmissions may also be self-contained, i.e. associated with a
dedicated synchronization signal and/or a demodulation reference
signal. The resource elements carrying the demodulation reference
signal may be time and/or frequency multiplexed with the resource
elements carrying the access table information. The WTRU may obtain
time and/or frequency synchronization using the synchronization
signal dedicated for access table acquisition. Some examples of the
synchronization signals include but are not limited to preambles
and/or sequences, functions of system signatures, or predefined
sequences reserved for an access table, unique word, etc. In
another example, the dedicated synchronization signal may be
different from a cell specific synchronization signal. The
dedicated synchronization signal may transmit on demand, i.e.
transmitted only when there is an associated access table
transmission active. The synchronization signal may be located at
an offset from the access table transmission. The WTRU may detect
the presence of the access table from the presence of a dedicated
synchronization signal associated with the access table
transmission. The maximum transport block size for an access table
transmission may be restricted to be less than a threshold to
accommodate different WTRU capabilities. WTRUs in coverage limited
scenarios or RF bandwidth restricted scenarios may receive
additional repetitions of access table transmissions to increase
SNR and robustness.
[0289] After receiving the at least one access table 902, the WTRU
may store the at least one access table 903 associated with one or
more system signatures in memory. The memory of the WTRU may
include but not is not limited to non-removable memory 130,
removable memory 132 described above with respect to FIG. 1B. When
storing the at least one access table 903, the WTRU may store a
base line configuration, which has common values for most of the
system, parameters and then may only store the delta configuration
for each system signature. Additionally, the WTRU may receive a
long term configuration that may be WTRU specific, to be used in
cells/TRPs where the WTRU visits frequently.
[0290] Assuming that the WTRU memory may hold access tables
corresponding at most n system signatures, the WTRU may use one or
more of the following algorithms to make room for an access table
corresponding to a newly received system signature when its memory
is full (already holding n signatures):
[0291] The WTRU may keep track of how often the access table
information was retrieved for each system signature. The WTRU may
overwrite the nth most frequently used system signature memory with
the newly received system signature.
[0292] The WTRU may keep track of the time spent (or time of stay)
in each cell/area associated with the signature. The WTRU may
overwrite the system signature where the least amount of time was
spent with the new signature.
[0293] The WTRU may keep track of most recently received system
signatures. The WTRU may overwrite the least recently used system
signature with the new system signature.
[0294] The WTRU overwrite the oldest signature (in terms of when it
was written into the memory) memory with the new signature
information (i.e. First in First Out).
[0295] Before initiating the procedure 900 of FIG. 9 to acquire or
re-acquire an access table, the WTRU may first determine that it
has access rights to the cell (e.g., PLMN ID, CSG, access barring
etc.). The WTRU may then ensure that it has valid initial access
parameters associated with the system signature(s), before any
uplink transmission in the cell. These parameters may be provided
by one or more entries in the access table.
[0296] The WTRU may determine the transmission characteristics of
the access table including the resources used for access table
transmission in terms of time, frequency, space and/or code, using
one or more of the following methods:
[0297] The WTRU may determine that scheduling modes for the access
table may be periodic or on-demand. For a periodic scheduling mode,
parts of the access table may be transmitted at a predefined
periodicity. For example, only the absolute minimum required for
initial WTRU access may be transmitted periodically. In this
example, only the UL resource configuration for initial access PLMN
ID, Access restriction, Non-critical extensions etc., may be
transmitted. Such periodic transmissions may not be limited to just
one TRP and may be common parameters applicable to two or more
TRPs. The on-demand solution may be considered as a leaner approach
compared to sending all the system parameters for all TRPs all the
time. Parts of an access table may not be transmitted periodically
and only transmitted based on a request by the WTRU. A WTRU
triggered activation of the access table transmission may include
WTRUs requiring access table information be configured to transmit
an explicit access table activation request/interest notification
message. The WTRU may use UL resources reserved to trigger
on-demand access table transmissions. (e.g., UL RACH resources or
UL signal). In an example, the WTRU may request specific parts of
the access table by transmitting detected a system signature and/or
a value tag and/or a reason/cause code. The WTRU may receive a RAR
related message that carries a DL grant carrying the requested
access table information. There may be timing relations between
on-demand requests and SIB transmission (with or without PDCCH).
Alternatively, the WTRU may receive a paging like message that
carries information about the on-demand access table transmission.
Such a paging mechanism may be beneficial for WTRUs to receive the
access table opportunistically (i.e. WTRUs that did not transmit an
access table request). In a hybrid scheduling mode, the access
table transmission may dynamically switch between on-demand and
periodic modes. The hybrid method may allow a flexible periodicity
for the access table transmission ranging from frequent
transmission to completely on-demand transmission. The periodicity
may be determined by the number of WTRU requests (for example,
WTRUs may be configured to report TRPs in DTX using reserved
signatures), network listening (for example, TRPs may listen to
other TRP transmissions or WTRU transmissions), based on cell load
(for example, it may be efficient to do periodic transmission if
the number of WTRUs in the cell are high), based on assistance
layer, based on active SOM/Services, based on inter-TRP
coordination (e.g., over X2), based on RRM aspects (e.g., resource
utilization, time of day etc.), etc.
[0298] The WTRU may determine the DL resources for access table
transmission based on one or more of the following methods:
[0299] A paging related message that indicates the presence of
access table information. Additionally, the paging message may also
carry DL resource grant with the scheduling information of access
table transmission.
[0300] A downlink control information (DCI) in a control channel
(for example, PDCCH, EPDCCH etc.).
[0301] An implicit relationship to the time/frequency resources
occupied by the system signature, and a dedicated control channel
common to a plurality of TRPs (for example, for single frequency
mode of transmission).
[0302] The WTRU may request one or more parts of the access table
that contains parameters related to a particular connection
procedure. The network may then, in addition to transmitting the
requested connection procedure parameters, allocate resources for
connection procedure (i.e. piggyback the access table request and
connection request procedure). Alternatively, the WTRU may include
specific reasons for a connection request (for example, MO data or
signaling), and the network may then provide the relevant SIB to
the WTRU and additionally allocate resources for the connection
procedure. Additionally, the WTRU may include a value tag in the
connection request.
[0303] FIG. 10 is a flow diagram of an example random access
procedure using initial access using system signatures or signature
sequences 1000 that may be performed in the example system 700
described above and used in combination with any of the embodiments
described herein. While each step of the procedure 1000 in FIG. 10
is shown and described separately, multiple steps may be executed
in a different order than what is shown, in parallel with each
other, or concurrently with each other. The process of FIG. 10 is
performed by a WTRU for exemplary purposes, but it may also be
performed by any node operating in a wireless communications system
such as a TRP, eNB, 5gNB, AP, or base station.
[0304] In the example of FIG. 10, a WTRU, via the transceiver or
receiver of the WTRU as described above, may receive at least one
set of RACH configurations via an access table 1001 received in
accordance with any of the methods described herein. As a result,
the WTRU may be configured with one or more sets of potential RACH
configurations via the access table. RACH configurations may
include a preamble configuration (for example, number of preambles,
preamble grouping, preamble selection criteria, etc.), power
ramping parameters, RAR window configuration, retransmission
configuration, PRACH configuration (for example, RACH occasion,
time/frequency resources, RACH format, etc.), retransmission, etc.
Additionally, the WTRU may distinguish two different categories of
RACH configurations, which may each be associated with one TRP or
associated with a plurality of TRPs.
[0305] The WTRU may receive a system signature 1002. The WTRU may
then determine the allowed RACH configurations of the at least one
set of RACH configurations based on the received system signature
1003. In some embodiments, the WTRU may select a subset of RACH
configurations among a plurality of allowed RACH configurations
based on criteria including but not limited to the following:
[0306] The trigger for random access: the WTRU may determine the
RACH configuration based on whether the msg3 has signaling or data
PDUs. Each SOM may be associated with a specific RACH
configuration. The WTRU may determine the RACH configuration
according to the SOM for which the data becomes available. Each
network slice may be associated with a specific RACH configuration.
The WTRU may determine the RACH configuration according to the
slice for which the data becomes available.
[0307] WTRU state: the WTRU may be in the ACTIVE/CONNECTED state.
For example, the WTRU may be already connected to the network and
upon wake up from DRX, the WTRU may select the RACH configuration
associated with the serving TRP. Alternatively, the WTRU may
perform a RACH procedure in response to a network trigger (for
example, RACH order). In this case, the WTRU may determine the
network node that triggered the RACH order and select the RACH
configuration associated with the network node. The WTRU may be in
the PASSIVE/IDLE state. For example, the WTRU may have no active
connections to the network node and/or during a network node
selection procedure. The WTRU may select a RACH configuration
associated with multiple TRPs and perform TRP selection based on
RACH procedure.
[0308] WTRU coverage status: the WTRU may choose a RACH
configuration based on its coverage status, for example normal
coverage or needing enhanced coverage.
[0309] Measurement results: the WTRU may select one or more TRPs
based on measurements on one or more system signatures and/or
reference signals. The WTRU may then determine the RACH
configuration associated with selected TRPs.
[0310] WTRU capability: the WTRU may receive different RACH
configurations indicative of network node capability. For example,
a WTRU with expanded features such as a phase2 5G WTRU may
prioritize a RACH configuration associated with TRPs with 5G phase2
capability, whereas a WTRU with limited features such as a phase1
5G WTRU may select RACH configurations associated with LTE assisted
TRPs.
[0311] DL path loss.
[0312] Size of data and/or signaling PDU (for example, MSG3).
[0313] The WTRU may be preconfigured with different RACH resource
sets, and each set associated with one of more of the following
properties: TRP specific RACH resources reserved for a point to
point RACH procedure; RACH resources specific to two or more TRPs
reserved for a point to multi-point RACH procedure. The multi-point
RACH resource configuration may include whether the WTRU waits for
a first RAR (in the case of TRP coordination) or whether the WTRU
waits for the whole RACH window (in case of WTRU based RAR
selection).
[0314] Referring to FIG. 10, the WTRU may then transmit a preamble
using the received system signature 1004. For example, during
preamble transmission, the WTRU may use the system signatures for
initial power setting and timing reference (for example, a
measurement based on the reception of the system signature). The
WTRU may indicate some form of the identity of the WTRU using the
Msg1/Preamble transmission, wherein the WTRU ID may be one of: ID
of the WTRU specific to a serving TRP (for example, RNTI); ID of
the WTRU specific to a group of TRPs (for example, allocated by a
central unit); RNTI of the WTRU allocated in the assistance layer
(for example, in the LTE-Evo macro eNB); temporary NAS identifier
of the WTRU; and an Explicit RAN level WTRU context identifier (for
example, unique within a logical RAN area).
[0315] Preamble selection and/or PRACH resource selection for use
in the preamble transmission may be a function of the WTRU ID. The
WTRU may select the preamble and RACH resource based on a hashing
function. The hashing function may map the WTRU ID to a specific
PRACH resource. The number of WTRUs may typically be greater than
available PRACH resources and may result in a collision. A WTRU may
randomize the collision by using, for example, one or more
following parameters as input to the hashing function: WTRU
identity, an ID related to time domain (for example, subframe
number, symbol number where the RACH is transmitted), an ID related
to frequency domain (for example, starting subcarrier index, RB
number, bandwidth region, etc.), cell ID/System signature, and
retransmission count.
[0316] The WTRU may transmit additional information along with the
PRACH transmission. For example, the WTRU may attach a small
payload or MAC control element along with the RACH preamble
transmission that carries additional information such as an
explicit WTRU ID or WTRU context identifier. In another example,
the WTRU may convey additional information by selection of a
specific RACH resource. For example, the WTRU may select RACH
resources associated with multiple TRPs to convey the need for
network node selection. In another example, the WTRU may select a
RACH configuration associated with resource repetition to convey
the need for enhanced coverage. In yet another example, the WTRU
may transmit an indication of the WTRU's needs (for example, size
of the data packet, type of service, type of signal structure
requested).
[0317] The preamble transmissions of the WTRU may be associated
with a DL system signature, which may be associated with one or
more MAC instances in the network. The RACH resources (for example,
time, frequency, preamble, etc.) may be associated with one TRP or
group of TRPs. The WTRU may determine the RACH configuration
associated with a signature from the access table. Alternatively,
parts of the RACH configuration may be implicitly determined by one
or more aspects of the system signature itself (for example,
relative offset in time/frequency, bandwidth, etc.).
[0318] The WTRU may be configured with a common RACH configuration
irrespective of the number of TRPs listening to a RACH on those
resources. The WTRU may be transparent to the number of network
nodes that receive and process the UL random access message.
[0319] In another example, the WTRU may indicate to the network if
the RACH is targeted towards one TRP or multiple TRPs. The WTRU may
provide such an indication by either including additional
information with the PRACH transmission, for example, a MAC control
element and/or attaching a unique word to an OFDM symbol and/or as
a small payload and/or selection of RACH resource group and/or
preamble and/or time/frequency resource selection.
[0320] The retransmission behavior of the WTRU may be a function of
the RACH resource selection. For example, each RACH resource set
may be associated with a different retransmission
characteristics/parameters including but not limited to the maximum
number of retransmissions allowed, a length of the response window,
a contention resolution timer, etc. The WTRU may apply different
RACH configurations for retransmissions compared to initial
transmission. The WTRU may be configured with additional RACH
opportunities for retransmission. For example, the WTRU may
consider additional pre-configured RACH resources for transmission,
which may be reserved for retransmission only. The WTRU may select
a RACH configuration associated with multiple TRPs after a
preconfigured number of attempts on a TRP specific RACH have
expired. For example, the initial transmission of the WTRU may be
specific to a TRP, and upon failure (for example, no RAR or
contention resolution timer expiry), the WTRU may target the
retransmission to more than one TRP to increase possibility of a
success.
[0321] Referring to FIG. 10, the WTRU may receive at least one RAR
message corresponding to the preamble transmission 1005. The WTRU
may receive a RAR corresponding to each RACH transmission. RARs
from the same TRP (for example, to provide enhanced coverage) or
RARs from different TRPs (for multi-connectivity) may be separated
in time and/or frequency, but within a predefined RAR window. The
WTRU may be required to receive all possible RARs within the RAR
window and not stop after the first RAR. The RAR window size may be
function of number of TRPs involved in the RACH procedure. Or a
default RAR window size may be defined and a bitmap in RAR indicate
that it is the last RAR message within the window. The WTRU may
also receive different RAR messages (formats/contents) based on
selection of RACH configuration. The WTRU may receive information
including but not limited to the following in the RAR message:
[0322] The WTRU may receive a synchronization signal specific to
TRP in the RAR message. The WTRU may perform synchronization with
the preferred/selected TRP based on the synchronization signal
received within the RAR from that TRP. WTRU may consider the
received RAR message as a DL timing reference for initial access
towards that TRP.
[0323] The WTRU may receive a TRP identity or an identity specific
to group of TRPs in the RAR message.
[0324] The WTRU may receive a number of allowed associations in the
RAR message. The WTRU may limit the max number of associations
according to a value signaled in the received RAR message.
[0325] The WTRU may receive a reference signal for measurement and
selection of TRPs in the RAR message. The WTRU may use either a
combination of measurements made on system signatures and reference
signals included in the RAR or the measurements made on reference
signals included in the RAR for selection of TRP(s)
[0326] The WTRU may receive a last RAR indication in the RAR
message. If the last RAR indication is false, the WTRU may wait for
one or more RAR messages within the current RAR window else the
WTRU may stop listening to RAR messages and assume an end of the
RAR window at the subframe carrying the RAR message with last RAR
indication as true. Upon the end of the RAR window, the WTRU may
perform initial access procedures based on received RAR messages
within the window.
[0327] The WTRU may receive additional system information in the
RAR message. For example, the RAR message may explicitly include a
dedicated configuration to perform further initial access or a
connection establishment procedure. Alternatively, the RAR message
may implicitly indicate such a configuration via additional
signatures or a DCI for the transmission of additional system
information.
[0328] The WTRU may transmit additional context information if the
RAR message includes a request for additional WTRU context
information. This may happen for example, when the WTRU context
cannot be retrieved or is unknown from the preamble or the WTRU ID
is ambiguous (i.e. there exists more than one WTRU context for a
given WTRU ID).
[0329] The WTRU may receive a redirection message that may be
included in the RAR message. For example the WTRU may be redirected
to a different TRP which was turned OFF earlier and/or redirected
to different layer (for example, a macro layer or small cell
layer), different RAT (for example, to a sub 6 GHz or above 6 GHz
RAT) or a different spectrum (for example, unlicensed spectrum).
The redirection message may additionally provide assistance
information, such as timing assistance (for synchronization to
redirected TRP), initial access assistance (for example, a
dedicated preamble and/or RACH resources), etc.
[0330] The WTRU may receive an activation message that may be
included in the RAR message. For example, an identity or
configuration of a new WTRU specific SOM or slice which may be
activated based on WTRU request.
[0331] The WTRU may receive a demodulation reference signal that
may be included in the RAR message to decode it.
[0332] The WTRU may receive an L3 control message to provide
additional information (for example, a dedicated configuration, a
WTRU specific control channel configuration, etc.) that may be
included in the RAR message.
[0333] The WTRU may receive information on the set of TRPs that
coordinated to transmit the RAR in the RAR message.
[0334] The WTRU may receive information on the TRPG in the RAR
message, which may be associated with the TRP transmitting the
RAR.
[0335] The WTRU may receive information indicating whether handover
was successfully performed in the RAR message. For example, an
indication may be included to the WTRU to drop connectivity to a
source TRP.
[0336] The WTRU may receive assistance information for the WTRU to
begin monitoring other TRPs/TRPGs in the RAR message.
[0337] The WTRU may receive an indication in the RAR message that
previous grants for PUSCH (for example, for SPS) are still
valid.
[0338] The WTRU may receive a timing advance in the RAR message
that is specific to a TRP or a group of TRPs in a single RAR
message.
[0339] The WTRU may receive an UL grant specific to one TRP or
possibly different UL resources for more than one TRP in the RAR
message.
[0340] The WTRU may receive a temporary RNTI in the RAR
message.
[0341] Referring to FIG. 10, the WTRU may determine TRP association
based on the received at least one RAR 1006. WTRU may associate to
one or more TRPs as a function of the number of RAR messages
received and the selection criteria applied by the WTRU. The
selection criteria may include one or more of the following: based
on measurements over the RS transmitted with the RAR, based on
measurements made on a previous RS (for example, the WTRU may
pre-rank them beforehand), a combination of measurements made with
a previous RS, an RS transmitted with the RAR, ranking metric
included in the payload of the RAR, earliest timing using the
timing advance value in RAR, and timing of the RAR
transmission.
[0342] The WTRU may determine association with at least one TRP
based on this random access procedure. The WTRU may determine a
number of TRPs to associate based on network configuration (for
example, max number of connections may be configured in the access
table), number of RAR messages that satisfy WTRU selection
criteria, WTRU state (for example, the WTRU may be already
connected to a serving TRP, and the WTRU may select the RAR
received from the serving TRP), WTRU type of service/QoS (for
example, ultra-reliable service may need connectivity to more than
one TRP), WTRU mobility status (for example, a stationary WTRU may
select one TRP, WTRUs with medium/fast mobility may select more
than one TRP for seamless handover), WTRU capability (for example,
the WTRU may be restricted by number of RF chains), and the type of
physical channel (for example, for a beamformed random access the
WTRU may select more than one TRP for increased robustness against
link failure).
[0343] The WTRU may associate with a number of TRPs according to
Min (network configured max connections, number of RAR messages
satisfying WTRU selection criteria, supported max connections based
on WTRU capability). WTRU may indicate the selection of TRPs to the
network in one of the following ways: the WTRU may transmit the
identities of selected TRPs in a control message (e.g., a L3
message or MSG3) in a common UL resource configured for all the
TRPs; the WTRU may transmit a control message on the UL resources
granted/configured by the RAR messages selected by the WTRU; and
the WTRU may transmit the of selected TRPs in a control message
(e.g., a L3 message) to the serving cell in assistance layer (e.g.,
LTE-Evo eNB).
[0344] The WTRU may identify the TRPs using one or more of system
signature, system signature sequence, or identity of the TRPs
included in the RAR message.
[0345] In one embodiment, TRPs may select the best RAR for the
WTRU. The coordination between the TRPs may be distributed or
centralized (for example, in a RAN central unit). The TRPs may
exchange a suitability metric to determine the best TRP to serve
the WTRU. The suitability may include one or more of SNR on the
received PRACH for a specific TRP, load on TRPs, (for example, to
achieve implicit load balancing), TRPs that already have a stored
WTRU context (for example, based on historical association), TRPs
matching WTRU capability, any other proximity criteria, and based
on WTRU's needs, for example, UL or DL heavy, or transmission
type.
[0346] In another embodiment, the WTRU may determine whether to
perform WTRU based RAR selection or use network based RAR selection
based on system signature, type of RACH resource, or based on
explicit network configuration in access table. In another example,
the WTRU may determine the need to perform WTRU based RAR selection
based on the number of RAR messages; if only one RAR message is
received the WTRU may consider it as network based selection. If
WTRU receives more than one RAR message, then WTRU may perform RAR
selection procedure as described above. In another example, the
mode of RAR selection may be explicitly indicated in the RAR
message itself, for example with a control bit.
[0347] A hybrid solution may be also used, wherein both a network
based selection and a WTRU based selection are applied. In one
example, TRPs may coordinate to down select two or more RARs among
multiple RAR messages, and the WTRU may then select one or more
TRPs for association. In another example, WTRUs may receive two or
more RARs and transmit the identity of selected TRPs to the
network. The network may then perform the second stage of selection
and indicate the result to the WTRU in a new control message.
[0348] System signatures may be used for a rapid reconfiguration of
WTRU specific resources. The WTRU may obtain one or more
pre-configuration sets, as part of dedicated signaling or cell
specific signaling. The pre-configuration set may include but is
not limited to the following: a scheduling grant, another downlink
or uplink control configuration, and/or a L2/L3 configuration. For
example, a scheduling grant may include a pre-defined resource
allocation granularity (for example, one, two or more resource
blocks).
[0349] Each of the preconfigured sets may be mapped to one or more
system signature resources (for example, sequences and
time/frequency resources). The WTRU may be required to monitor the
presence of system signatures.
[0350] The WTRU upon receiving one of the signatures may apply the
associated pre-configuration. The WTRU may be configured to
transmit an acknowledgement upon activation of the pre-configured
resources. Alternatively, a short control message with a few bits
of information may be used to activate one of the pre-configured
sets.
[0351] A WTRU may be configured to utilize diverse access methods,
wherein each access method is defined in terms of a specific
combination of one or more of UL synchronization aspect, an
arrangement related to the number of network nodes, a timing
relation between a first uplink transmission and an actual data PDU
transmission, a contention resolution and/or WTRU identification,
UL resources used for access, a characteristic associated to HARQ
processing, multiple access scheme, and assistance aspect.
[0352] For the UL synchronization aspect, the WTRU may select a
different initial access procedure based on its UL synchronization
status. For example, if the WTRU is required to be synchronized in
the uplink before the data transmission, the WTRU may select a
random access method to acquire UL synchronization and then perform
data transfer. If the WTRU is not required to be UL synchronized,
then WTRU may perform an asynchronous access method with relaxed
time and frequency synchronization requirements. In one example,
two different access methods may be defined based on how the
synchronization is performed, WTRU based or network based.
[0353] An arrangement related to the number of network nodes, for
example, may include a common configuration and/or UL resource
across a group of TRPs that may be reserved for multi-point initial
access, wherein WTRU uplink transmissions may be received by more
than one TRP. Alternatively, the WTRU may first select a specific
TRP (for example, based on suitability criteria) and then may
acquire initial access parameters corresponding to that TRP and
subsequently perform an initial access procedure towards the
selected TRP.
[0354] For a timing relation between first uplink transmission and
actual data PDU transmission, different initial access methods may
be defined based on a relation between the first uplink
transmission and the actual data PDU transmission. For example, the
WTRU may include a portion of a data PDU or the whole data PDU in
the first uplink transmission during initial access. Alternatively,
the WTRU may transmit one or more signals/preambles before
acquiring resources for actual data PDU transmission.
[0355] For contention resolution and/or WTRU identification,
different initial access methods may be defined based on whether
the WTRU should confirm that contention is resolved before data
transmission, or the WTRU may transmit data before the actual
contention resolution step. For example, the WTRU may initiate a
contention based data transfer and if there was no contention, the
WTRU may avoid the need for contention resolution step or
alternatively the WTRU may be required to provide additional
identification to resolve the contention or to identify the WTRU
context, but this may happen after the actual data PDU
transmission.
[0356] UL resources used for access includes one or more of
following aspects a transmission scheme: single-carrier or
multi-carrier scheme or a specific multi-carrier scheme such as
OFDM, SC-FDMA, FBMC, UFMC, zero tail or the like; a parameter
associated with a transmission scheme: for example, numerology
aspects such as subcarrier spacing, symbol duration, cyclic prefix
duration/guard length/zero tail length, transmit power (desired
and/or compensation factor), spreading factor, bandwidth, etc.;
frame structure, for example placement in time and/or frequency of
one or more reference signal(s), synchronization signals(s),
physical signal(s)/channel(s), TTI length, frame, subframe length,
TDD configuration etc.; scheduling aspects of the resources
including a maximum number of data bits allowed, for example,
depends on the size of time frequency/code resources, MCS,
repetition factor and or periodicity, number of retries, response
window etc.; and other physical processing aspects, for example,
spatial processing (precoding, transmit diversity, spatial
multiplexing), beamforming (analog, digital or hybrid), etc.
[0357] For a characteristic associated with HARQ processing,
different initial access methods may be defined based on whether
HARQ is used for the data transfer and HARQ parameters such as a
number of HARQ processes, relative timing between scheduling
grants, transmission/reception of data and transmission/reception
of HARQ feedback, etc.
[0358] For multiple access schemes, different initial access
schemes may be defined based on the type of multiple access used,
for example, resource spread multiple access, sparse code multiple
access, contention based access, scheduled access, etc. Each
initial access scheme may be associated with parameters specific to
a multiple access scheme (for example, a random access power level,
preamble, power ramping factor, max number of retransmissions etc.,
time frequency resource pattern, spreading code, sparse code etc.).
In one embodiment, resources may be grouped according to the
multiple access scheme, for example, groups of WTRUs may be
pre-configured (for example, via dedicated RRC signaling) for a
common grant less resource that may be accessed by WTRUs
autonomously, groups of resources may be configured (for example,
via an access table) for contention based access that may be
accessed by all WTRUs in the cell, groups of resources may be
configured (for example, via downlink control information) for
scheduled access that may be accessed only by WTRUs that have a
valid WTRU specific scheduling grant.
[0359] For the assistance aspect, the WTRU may perform initial
access on an assisted carrier/cell/cell group/slice/SOM based on
assistance information received from assistance carrier/cell/cell
group/slice/SOM. Such assistance information includes one or more
characteristics of the access method described above.
[0360] Various access methods may be performed by the WTRU.
[0361] One example access method includes the WTRU transmitting
data on a contention based data channel. The first uplink message
from the WTRU (for example, msg1) may carry a whole data PDU or
portions of it. The WTRU may also transmit a demodulation reference
signals, preambles, and/or the WTRU identity along with msg1. The
WTRU may choose the demodulation reference signal from a pool of
available sequences. Alternatively, the WTRU may choose the
demodulation reference signal as a function of the WTRU identity.
In another embodiment, the WTRU may be configured with a unique
demodulation reference signal and/or an explicit WTRU identity. The
WTRU may receive an acknowledgement from the network which includes
one or more of the following: a reference to the UL data PDU (for
example, time/frequency resource occupied by the data PDU),
demodulation reference signal sequence used in the UL PDU, WTRU ID
included in the data PDU, etc.
[0362] A second example access method is based on multi-point
random access as described above. Other example access methods may
include but are not limited to: beamformed random access for above
6 GHz, access methods specific to coverage enhanced WTRUs using
repetition, asynchronous access method with relaxed synchronization
requirements.
[0363] Configuration of diverse access methods may include one or
more characteristics/properties/parameters listed above, including
the resources to be used for the access method.
[0364] FIG. 11 is a flow diagram of an example procedure 1100 for
configuration of diverse access methods that may be performed in
the example system 700 described above and used in combination with
any of the embodiments described herein. While each step of the
procedure 1100 in FIG. 11 is shown and described separately,
multiple steps may be executed in a different order than what is
shown, in parallel with each other, or concurrently with each
other. The process of FIG. 11 is performed by a WTRU for exemplary
purposes, but it may also be performed by any node operating in a
wireless communications system such as a TRP, eNB, 5gNB, AP, or
base station. In the example of FIG. 11, a WTRU, via the
transceiver or receiver of the WTRU as described above, may receive
a configuration for at least one diverse access method 1101. This
reception of a at least one diverse access method 1101 may be
achieved according to at least one of the following: via a default
access method, a broadcasted configuration, a particular
arrangement of system signatures, an access table, a dedicated
configuration, an assisted configuration, and/or an implicit
determination.
[0365] For example, a default access method may be pre-configured
and the WTRU may use the default access method in the absence of
any other configuration or until it has acquired any of the
configurations described below.
[0366] A broadcasted configuration may include a list of
allowed/possible access methods may be broadcasted e.g., using RRC
msg (including system information messages), MAC control element
(in a shared scheduling information on a common channel and/or
initial access response message (for example, a RAR received during
random access procedure)), master information block (which may
include for example the initial access method used on a generic
SOM/slice or when detailed access table is not yet
acquired/available), system information broadcast (which may
include access methods allowed in a specific SOM/slice which may or
may not carry system information broadcast).
[0367] For using a particular arrangement of system signatures, a
predefined signal sequence may be used and/or relative
timing/frequency offset between such signals may be used (for
example, an access method may be indicated and/or determined as a
function of index associated with the sequence of broadcast signal
and/or relative placement (in time/frequency) between the plurality
of such signals).
[0368] A configuration for one or more access methods may be
provided in the access table, which may be indexed by a system
signature or a reserved value. For example, each access method may
be associated with a different system signature, and such an
association may additionally imply a mapping between a bandwidth
region where the system signature is transmitted and the applicable
access method within the associated bandwidth region. The WTRU may
obtain the access table transmitted using a broadcast mechanism
(for example, via a shared data channel) or using a dedicated
channel (for example, as a WTRU specific RRC configuration).
[0369] For a dedicated configuration, the WTRU may be explicitly
configured with one or more access methods/parameters using a
control protocol (for example, RRC protocol), medium access
protocol (for example, MAC control element or by means of RAR
message during a random access procedure), a paging message may be
used to indicate both a DL data arrival and the associated UL
access method/parameters to use, a NAS message (for example, a WTRU
may receive set of allowed access methods during attachment, and it
may be a function of WTRU subscription), downlink control signaling
(for example, by means of a DCI received, additionally the DCI may
indicate the resources or slices where the access methods are
applicable). The WTRU may prioritize the dedicated configuration
over other configurations. For example, one or more parameters in
the dedicated configuration may take precedence over parameters
configured through other means.
[0370] For an assisted configuration, the WTRU may obtain the
configuration for an access method from an assistance layer. Such a
configuration may be provided via a RRC configuration or may be
signaled using access table. For example an access method
configuration for the small cell layer may be provided by a macro
layer. In another example, the configuration for a beamformed small
cell layer (operating for example above 6 GHz) may be provided by
the assistance layer operating in the sub 6 GHz frequency.
[0371] For an implicit determination, the WTRU may implicitly
identify one or more aspects of access method from the
configuration of rest of the parameters. For example, the choice of
multiple access method may be implicitly determined by the nature
of resource allocation and/or parameterization of the UL
resources.
[0372] Configuration aspects may include the information necessary
for the WTRU to identify different access methods, select an
appropriate access method (for example, information applicable to
access method selection) and to perform access procedure. One or
more configuration aspects of the access method may be static,
whereas the others may be dynamic. In one example, the WTRU may
combine parts of configurations signaled using different methods to
obtain an overall configuration for an access method. For example,
a choice of multiple access method may be signaled in a broadcast
system information/access table, and the resources for the access
method may be dynamically scheduled via a control channel.
Additionally, the WTRU may obtain parts of the configuration from
different nodes to determine the overall configuration for an
access method. The WTRU may obtain assistance from a macro layer,
combined with specific information from small cell layers to
perform initial access on the small cell layer. The WTRU may
receive a configuration of UL resources independent of the access
methods. For example, a linkage may be provided between the UL
resources and the access method to be used on that UL resource. In
another example, a specific slice isolated from other slices may be
reserved for initial access procedures.
[0373] Referring to FIG. 11, the WTRU may trigger at least one
initial access procedure 1102. This step may be performed when one
or more of the following conditions are satisfied:
[0374] There is an arrival of UL data and/or higher layer signaling
(for example, RRC, NAS) and one or more of the following conditions
are satisfied: when WTRU UL synchronization status is
non-synchronized; data belongs to a logical channel or logical
channel group for which no connection exists, irrespective of the
status of other logical channels (for example, being active or
inactive); data belongs to a new logical channel group or logical
channel for which no transport channel mapping exists; data is for
a different service than the services that are currently active;
data belongs to the logical channel which is associated with a
different mode/slice/SOM than the currently active logical channel;
data on the LCH is configured to be transmitted to a TRP for which
WTRU doesn't have UL synchronization; data is for which no defined
configuration/i.e. radio bearers or logical channels exist; and
data is mapped to a different layer or RAT or component carrier or
cell group than the currently active layer/RAT/component carrier or
cell group.
[0375] There is DL data arrival and one or more of the following
conditions are satisfied: the WTRU receives a paging message or a
signal indicating DL data arrival and the paging message may
additionally indicate a new logical channel/transport channel
configuration; there is an explicit indication in a paging message
to trigger a specific access method, which may be on a specific SOM
and/or slice; and for example, the DL paging message may indicate
DL data arrival, along with either a logical channel identity
and/or mapping to a specific transport channel type and/or explicit
indication of initial access method.
[0376] There are aspects related to new or unknown system
signatures: the WTRU may be preconfigured to detect new signatures
and trigger a report to the network. Reception of an unknown system
signature for which no valid entry in the access table exists may
occur, for example, when a TRP transitions from an OFF state to ON
state, or when a new slice or SOM is instantiated and a system
signature specific to that slice/SOM is transmitted. Alternatively,
the WTRU may view unknown signatures simply as a non-accessible
transmission point or slice or SOM.
[0377] The L3 is re-established (for example, RRC connection): for
example, the L3 may be re-established due to a failure such as a
radio link failure, handover failure, or security failure. The WTRU
may be configured to initiate an access procedure for the purposes
of reporting the invalid configuration and/or to resume the data
transfer. For example, when the WTRU may be unable to comply with
one or more aspects of a configuration received in access table or
higher layer message (for example, L3) or MAC Control element or
any other means.
[0378] An initial access procedure is triggered by mobility of the
WTRU: for example, an initial access procedure may be triggered
when the WTRU moves into a new RAN routing area that is different
from the previous area or not included in the previous RAN routing
area group, or a change of RAN routing area, TRPG or RAN central
unit and handover.
[0379] There are aspects related to UL synchronization and timing
advance: the WTRU may lose UL synchronization (for example, the
WTRU may be required to maintain UL synchronization for low latency
transfer); for positioning purposes, when timing advance is needed
for WTRU positioning; and time elapsed, periodic such as when WTRU
enters DRX but still needs to maintain UL synchronization.
[0380] In the case of LTE-assisted 5gFLEX transport channels: the
WTRU monitors preconfigured time/frequency resources within LTE Uu
for 5GFlex operation. The WTRU may trigger initial access when it
detects one or more system signatures and/or when the received
power of the system signatures is above a threshold in the
resources configured for 5GFlex operation.
[0381] The WTRU receives an explicit order from the network (for
example, when the network orders the WTRU to transition from
asynchronous access to synchronous access, PDCCH order, and/or
network triggered initial access (for example to retrieve unknown
WTRU context)).
[0382] The WTRU changes coverage status: including moving back to
in-coverage from out-of-coverage, when the serving cell quality
drops below a threshold, and when WTRU enters enhanced coverage
mode. The WTRU may initiate initial access corresponding to
enhanced coverage mode (for example, repetition of RACH
preambles).
[0383] The WTRU is unable to acquire access table within time
elapsed: for example, the WTRU may use a default access method on a
low periodic resource that may be a function of system
signature.
[0384] The WTRU triggers at least one access procedure upon power
up.
[0385] The WTRU triggers at least one access procedure upon
activation of UL resources corresponding to a different access
method: including when a new slice or SOM is activated and one or
more UL resources in the slice/SOM is reserved for initial access.
The WTRU may perform the initial access method associated and/or
configured for that SOM or slice. When a new component carrier (for
example, in case of carrier aggregation) or when a small cell is
added (for example, in case of multi-connectivity), the WTRU may
trigger the initial access method configured for that carrier or
small cell, etc. For example, when above 6 GHz carrier is
activated, the WTRU may then perform initial access (for example,
beamformed initial access) specific to that carrier.
[0386] There is a trigger to a new/secondary access method as an
outcome of the primary access method or failure of the previous
access method. Triggers may be specific to D2D or relay mode.
[0387] Referring to FIG. 11, the WTRU may select at least one
access method of a plurality of access methods 1103. This selection
may be according to various selection criteria. WTRU may determine
the UL resources associated with and configured for the selected
access method. WTRU may then perform the at least one access
procedure 1104. This may be performed according to the rules
defined for the access method.
[0388] The selection criteria used to select the at least one
access method may include but is not limited to the following: as a
function of a logical channel type for which data becomes
available; based on the outcome of a previous initial access
procedure; based on the outcome of a primary initial access
procedure; as a function of a size of the data PDU; as a function
of a type of the data PDU (for example, IP or non-IP data); as a
function of the service request type; as a function of the existing
LCH connections/link; a type of connection; as a function of an
access class; as a function of the radio interface; as a function
of signal structure, SOM, or bandwidth region; as a function of
slice; as a function of Type of Service/QoS; as a function of TRP
cell group specific, TRP specific, TRPG specific; as a function of
a layer; a configuration aspect; based on resource selection;
generic access methods and specific access methods; as a function
of a received system signature; as a function of the capability
and/or subscription of the WTRU; based on the coverage status of
the WTRU; based on a function of the operation mode; based on more
than one initial access procedure in parallel.
[0389] For a function of logical channel type for which data
becomes available, different types of radio bearer and/or logical
channels and/or logical connections, logical channel groups and/or
transport channels and a mapping between them may be defined to
characterize different types of end to end service (for example,
eMBB, URLLC, or mMTC) to be supported by the 5GFlex. Each logical
channel and/or transport channel may be associated with one or more
access methods. Upon arrival of data for an empty logical channel,
the WTRU may first select one (if more than one exist) and then
perform the initial access procedure associated with that LCH.
[0390] When based on the outcome of a previous initial access
procedure, the WTRU may maintain a count of number of failures with
a particular access method. The WTRU may switch to a different
access method when the number of failures exceeds a predefined
threshold. Additionally, the failed access method may be barred for
a predefined time specified, for example, via a prohibit timer. The
WTRU may retry a failed access method with different parameters
(including but not limited to power ramp, increased repetition, and
different resources reserved/prioritized for colliding WTRUs (for
example, some dedicated resources)). The WTRU may declare a radio
link failure when all or a set of initial access methods or a
counter across all access methods exceeds a threshold or when a
predefined time elapses from the start of the initial access
procedure.
[0391] The selection may be based on the outcome of a primary
initial access procedure, for example, when the primary initial
access procedure provides more information about the secondary
initial access procedure. There may be a redirection to another in
case of SOM.
[0392] The selection may be a function of existing LCH
connections/links. For example, upon arrival of data in a new LCH
the WTRU may use specific methods corresponding to the current
active LCH, TCH, slice, SOM (for example, using current UL control
channel).
[0393] The selection may be based on type of connection. The WTRU
may be configured to perform a connection based data transfer or a
connectionless data transfer, for example, based on a size of the
data PDU, latency, and/or overhead requirements. The WTRU may
select different access methods associated with the nature of the
connection. For example, the connection may be based on a random
access procedure for a connection oriented data transfer, a
contention based data transfer procedure for connectionless data
transfer, an establishment cause (MO signaling or MO data),
re-establishment or establishment, high priority access, delay
tolerant access, emergency connection, etc.
[0394] The selection may be a function of an access class. The WTRU
may select different access methods based on an access class, and
some of the access methods may be restricted for certain access
classes.
[0395] The WTRU may select the access method as a function of the
radio interface. For example, different access methods may be
defined for LTE, LTEEvo, 5GFlex below 6 GHz, and 5GFlex above 6
GHz. The WTRU may select one access method out of possible access
methods for each of the radio interfaces. The WTRU may prioritize
selection of radio interfaces based on an allowed access method
that meets one or more requirements in terms of latency and/or
overhead.
[0396] The selection may be a function of the signal structure,
SOM, or bandwidth region. There may be a set of allowed resources
within the SOM. The WTRU may select a SOM and then perform access
method associated with it.
[0397] The selection may be a function of slice (type of slice).
The WTRU may perform an initial access method on a particular slice
according to the type of service provided by the slice (function of
system signature).
[0398] The selection may be a function of a layer. The access
method may also be determined from a property associated with the
node, such as an indication of a layer.
[0399] The selection may be based on a configuration aspect. For
example, the WTRU may be configured with a specific access method
for the DL data arrival in the DL paging message. The WTRU may
trigger the configured access method to use in the target cell upon
handover.
[0400] The selection may be based on resource selection. The WTRU
may determine the access method based on, for example, the UL
resource selection. The WTRU may select an earliest occurring UL
resource and then select the access method associated/configured
for that resource. Among the available access methods, WTRU may
choose one as a function of its reducing latency aspect. The WTRU
may compare the scheduling periodicity of different access
methods/resources and select the earliest or one with least
overhead, etc.
[0401] The selection may be based on a generic access method and/or
a specific access method. The WTRU may first select a default
access method configured for/associated with a generic
SOM/slice/preferred cells/RATs and subsequently perform specific
access methods associated with other SOMs/slices/cells/cell
groups/RATs. The specific access methods may be
configured/activated as a result of default access method. In one
solution the default access method may be cell specific, and the
specific access method may be WTRU specific. For example, there may
be a distinction between the initial access using the nominal
bandwidth (for example, power on, obtaining PDP context, etc.) and
an initial access for a specific SOM, which may be associated with
a given signature. Some eNBs/TRPs may support only one, the other,
or both. For example, a macro eNB may support access using a
nominal SOM, while TRPs may support only SOM-specific access (no
means to exchange L3/NAS signaling), while others (eNBs or TRPs)
may support both.
[0402] The selection may be a function of a received system
signature. The WTRU may select the initial access method associated
with/configured for the received system signature. For example,
when the WTRU receives multiple system signatures, the WTRU may
select the initial access method associated with the system
signatures of a highest received power or preferred type of system
signature.
[0403] The selection may be based on coverage status of the WTRU,
which may include in-coverage, out of coverage, enhanced coverage,
etc. Function of operation mode may include different access
methods based on whether the operating mode is infrastructure mode,
D2D mode, relay mode or transport (for example,
self-backhaul/fronthaul) mode. More than one initial access
procedure may be used in parallel.
[0404] Although features and elements are described above in
particular combinations, one of ordinary skill in the art will
appreciate that each feature or element can be used alone or in any
combination with the other features and elements. In addition, the
methods described herein may be implemented in a computer program,
software, or firmware incorporated in a computer-readable medium
for execution by a computer or processor. Examples of
computer-readable media include electronic signals (transmitted
over wired or wireless connections) and computer-readable storage
media. Examples of computer-readable storage media include, but are
not limited to, a read only memory (ROM), a random access memory
(RAM), a register, cache memory, semiconductor memory devices,
magnetic media such as internal hard disks and removable disks,
magneto-optical media, and optical media such as CD-ROM disks, and
digital versatile disks (DVDs). A processor in association with
software may be used to implement a radio frequency transceiver for
use in a WTRU, UE, AP, eNB, 5gNB, terminal, base station, RNC, or
any host computer.
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