U.S. patent application number 16/088200 was filed with the patent office on 2020-09-24 for method and procedures for downlink physical channels to reduce latency in an lte advanced system.
This patent application is currently assigned to INTERDIGITAL PATENT HOLDINGS, INC.. The applicant listed for this patent is INTERDIGITAL PATENT HOLDINGS, INC.. Invention is credited to Erdem Bala, Moon-il Lee, Janet A. Stern-Berkowitz.
Application Number | 20200305129 16/088200 |
Document ID | / |
Family ID | 1000004927675 |
Filed Date | 2020-09-24 |
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United States Patent
Application |
20200305129 |
Kind Code |
A1 |
Lee; Moon-il ; et
al. |
September 24, 2020 |
METHOD AND PROCEDURES FOR DOWNLINK PHYSICAL CHANNELS TO REDUCE
LATENCY IN AN LTE ADVANCED SYSTEM
Abstract
A wireless transmit/receive unit (WTRU) may receive, in a higher
layer message, a configuration for a short transmission time
interval (sTTI) physical downlink control channel (sPDCCH). The
WTRU may monitor, on a condition that a sPDCCH is configured, a
subset of PDCCH candidates of one or more aggregation levels. The
WTRU may monitor, on a condition that the sPDCCH is not configured,
the PDCCH candidates.
Inventors: |
Lee; Moon-il; (Melville,
NY) ; Stern-Berkowitz; Janet A.; (Little Neck,
NY) ; Bala; Erdem; (East Meadow, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
INTERDIGITAL PATENT HOLDINGS, INC. |
Wilmington |
DE |
US |
|
|
Assignee: |
INTERDIGITAL PATENT HOLDINGS,
INC.
Wilmington
DE
|
Family ID: |
1000004927675 |
Appl. No.: |
16/088200 |
Filed: |
March 30, 2017 |
PCT Filed: |
March 30, 2017 |
PCT NO: |
PCT/US2017/024943 |
371 Date: |
September 25, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62373046 |
Aug 10, 2016 |
|
|
|
62334886 |
May 11, 2016 |
|
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62315404 |
Mar 30, 2016 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W 72/042 20130101;
H04L 5/0053 20130101; H04L 1/1812 20130101; H04L 1/1861 20130101;
H04W 72/0446 20130101 |
International
Class: |
H04W 72/04 20060101
H04W072/04; H04L 1/18 20060101 H04L001/18; H04L 5/00 20060101
H04L005/00 |
Claims
1. A method performed by a wireless transmit/receive unit (WTRU),
the method comprising: receiving, in a higher layer message, a
configuration for a short transmission time interval (sTTI)
physical downlink control channel (sPDCCH); monitoring, on a
condition that a sPDCCH is configured, a subset of PDCCH candidates
of one or more aggregation levels; and monitoring, on a condition
that the sPDCCH is not configured, the PDCCH candidates.
2. The method of claim 1 further comprising receiving a physical
hybrid-ARQ indicator channel (PHICH) on a known sPDCCH resource
that indicates presence of a configured sTTI resource.
3. (canceled)
4. The method of claim 1, wherein a configuration of sTTI resources
is received in a sTTI indicator.
5. The method of claim 4, wherein the sTTI indicator is based on a
set of physical hybrid-ARQ indicator channel (PHICH) resources.
6. A wireless transmit/receive unit (WTRU) comprising: a processor;
a receiver; and wherein the receiver is configured to receive, in a
higher layer message, a configuration for a short transmission time
interval (sTTI) physical downlink control channel (sPDCCH); the
processor is configured to monitor, on a condition that a sPDCCH is
configured, a subset of PDCCH candidates of one or more aggregation
levels; and the processor is further configured to monitor, on a
condition that the sPDCCH is not configured, the PDCCH
candidates.
7. The WTRU of claim 6, wherein a physical hybrid-ARQ indicator
channel (PHICH) is received on a known sPDCCH resource that
indicates presence of a configured sTTI resource.
8. (canceled)
9. The WTRU of claim 6, wherein a configuration of sTTI resources
is received in a sTTI indicator.
10. The WTRU of claim 9, wherein the sTTI indicator is based on a
set of physical hybrid-ARQ indicator channel (PHICH) resources.
11-15. (canceled)
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
application No. 62/315,404 Filed on Mar. 30, 2016, U.S. Provisional
Application No. 62/334,886 filed on May 11, 2016, and U.S.
Provisional Application No. 62/373,046 filed on Aug. 10, 2016, the
contents of all of which are hereby incorporated by reference
herein.
BACKGROUND
[0002] With new applications emerging for cellular technology such
as alarm reporting, automotive safety, and factory process control,
the importance of low latency cellular communications, including
machine type communications (MTC), has rapidly increased. For
example, in an LTE Advanced (LTE-A) system, the typical 1 ms
transmission time interval (TTI) and associated latencies may no
longer be sufficient. Existing applications such as gaming and
real-time applications like VoLTE and video telephony/conferencing,
may also benefit from reduced latency in terms of, for example,
increased perceived quality of experience.
SUMMARY
[0003] A method for a wireless transmit receive unit WTRU to
receive control information for a short transmission time interval
(sTTI) communications are disclosed. The method may include
receiving a configuration for one or more sTTI resources, receiving
an indication of the presence. of a configured sTTI resource, and
monitoring a short PDCCH (sPDCCH) in the configured sTTI resource
using with a number of blind decoding candidates. The number blind
decoding candidates may be based on the length of the sTTI. The
indication may be received on a physical hybrid-ARQ indicator
channel (PHICH). The configuration of sTTI resources may be
received in a sTTI indicator. The sTTI indicator may be based on a
set of PHICH resources.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] A more detailed understanding may be had from the following
description, given by way of example in conjunction with the
accompanying drawings wherein:
[0005] FIG. 1A is a system diagram of an example communications
system in which one or more disclosed embodiments may be
implemented;
[0006] 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;
[0007] 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;
[0008] FIG. 2 is a diagram illustrating a conventional hybrid
automatic repeat request (HARQ) and a HARQ for a shortened
transmission time interval (sTTI);
[0009] FIG. 3 is a diagram illustrating the use of legacy EPDCCH
for sTTI resource scheduling;
[0010] FIGS. 4 and 5 are examples of Resource Element Groups
(REGs);
[0011] FIG. 6 is a diagram illustrating allocation of the Physical
Control Format Indicator Channel (PCFICH) REGs according to a
physical cell-ID (PCI);
[0012] FIG. 7 is a diagram illustrating PCFICH and Physical
Hybrid-ARQ Indicator Channel (PHICH) REGs according to PCI;
[0013] FIG. 8 is a diagram illustrating multiple sTTI resource
types configured in a subframe;
[0014] FIGS. 9 and 10 are diagrams of control region locations for
a short Transmission Time Interval-indicator (sTTI-indicator);
[0015] FIG. 11 is a diagram illustrating sTTI Physical Downlink
Control Channel (sPDCCH) and sTTI Physical Downlink Shared Channel
(sPDSCH) association per sTTI; and
[0016] FIG. 12 is a diagram illustrating sPDCCH and sPDSCH
association with multiple sTTIs; and
[0017] FIG. 13 is a diagram illustrating the use of PHICH resources
as sTTI indicators.
DETAILED DESCRIPTION
[0018] 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 systems 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.
[0019] 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.
[0020] 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 eNode B, a Home Node B, a
Home eNode B, 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.
[0021] 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.
[0022] 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).
[0023] 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).
[0024] 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).
[0025] In other embodiments, the base station 114a and the WTRUs
102a, 102b, 102c may implement radio technologies such as IEEE
802.16 (i.e., Worldwide Interoperability for Microwave Access
(WiMAX)), CDMA2000, CDMA2000 1.times., 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.
[0026] The base station 114b in FIG. 1A may be a wireless router,
Home Node B, Home eNode B, 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.
[0027] 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.
[0028] 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.
[0029] 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 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.
[0030] 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.
[0031] 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.
[0032] 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.
[0033] 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.
[0034] 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.
[0035] 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 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 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).
[0036] 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.
[0037] 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.
[0038] 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.
[0039] 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.
[0040] The RAN 104 may include eNode-Bs 140a, 140b, 140c, though it
will be appreciated that the RAN 104 may include any number of
eNode-Bs while remaining consistent with an embodiment. The
eNode-Bs 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 eNode-Bs 140a, 140b, 140c may
implement MIMO technology. Thus, the eNode-B 140a, for example, may
use multiple antennas to transmit wireless signals to, and receive
wireless signals from, the WTRU 102a.
[0041] Each of the eNode-Bs 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 eNode-Bs 140a, 140b, 140c may communicate with one another
over an X2 interface.
[0042] The core network 106 shown in FIG. 1C may include a mobility
management entity gateway (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.
[0043] The MME 142 may be connected to each of the eNode-Bs 140a,
140b, 140c in the RAN 104 via an S1 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.
[0044] The serving gateway 144 may be connected to each of the
eNode Bs 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-eNode B 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.
[0045] 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.
[0046] The core network 106 may facilitate communications with
other 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 networks 112, which
may include other wired or wireless networks that are owned and/or
operated by other service providers.
[0047] Other network 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.
[0048] A short transmission time interval (sTTI) may be used to
reduce latency. Physical channels that have been designed based on
one normal TTI (nTTI) length (e.g., 1 ms) may not be optimized for,
or may not work properly for, a shorter TTI length (e.g., one or
several symbols in duration). For example, shortening the TTI of a
control channel (e.g., a downlink (DL) control channel) or reducing
the number of symbols available for a control channel may impact
the performance of the channel. A redesign of one or more channels
may be needed to reduce the performance impact that may occur due
to TTI shortening.
[0049] In addition, the rules for control channel monitoring have
been designed for a level of blind decoding complexity and battery
consumption for a particular TTI length. Shortening the TTI by a
factor of N may result in an N-fold increase in the number of blind
decodes if the same rules are used. Mechanisms may be needed to
reduce the impact to blind decoding complexity and battery
consumption that may occur due to TTI shortening.
[0050] The terms low latency transmission, reduced latency
transmission, and sTTI transmission may be used interchangeably. A
reduced latency transmission may use a reduced TTI or sTTI. The
terms reduced TTI, short TTI, sTTI, and rTTI may be used
interchangeably. The terms TTI and TTI length may be used
interchangeably. A short TTI length may refer to a TTI length
shorter than another TTI length that may be a typical, normal,
nTTI, or regular TTI length such as 1 ms or 14 Orthogonal Frequency
Division Multiplex (OFDM) symbols. A regular (e.g., normal or
legacy) transmission may use a nTTI. The terms typical, normal,
regular, and legacy may be used interchangeably. A short TTI length
may be defined by a number, Ns, of OFDM symbols, where Ns may be
smaller than the number of OFDM symbols for a nTTI (e.g.,
Ns<14).
[0051] A time, frequency, and/or spatial resource may be
configured, predefined, allocated, or indicated as a resource for
sTTI transmission and/or reception. It should be noted that a
resource for sTTI transmission, sTTI resource, sTTI PRBs, sTTI
subframes, sTTI symbols, sTTI REs, and sTTI antenna ports may be
used interchangeably herein.
[0052] A time resource may include, but may not be limited to, one
or more OFDM symbols, one or more SC-FDMA symbols, one or more time
slots, one or more subframes, one or more radio frames, and/or one
or more time samples. A frequency resource may include, but may not
be limited to, one or more subcarriers, one or more PRBs, and/or
one or more component carriers. A spatial resource may include, but
may not be limited to, one or more antenna ports, one or more
reference signals, one or more cells, one or more physical cell-IDs
(PCID), and/or one or more virtual cell-IDs (VOID).
[0053] FIG. 2 shows an example 200 of a conventional hybrid
automatic repeat request (HARQ) for an nTT 210, and a HARQ for a
shortened transmission time interval (sTTI) 220. In an embodiment
the sTTI length may be between 1 symbol and 1 timeslot, which may
be 7 symbols. As shown in FIG. 2, a sTTI may require less
processing time and may provide for reduced hybrid automatic repeat
request (HARQ) round trip time (RTT). The nTTI length of 1 ms may
be too long to meet the needs of low latency communications, such
as, for example, machine-type communications, alarm reporting,
automotive safety, factory process control, gaming, and voice over
LTE (VoLTE). The scope of reduced latency may include: Physical
channel design with shortened TTI for PDCCH, PDSCH, PUSCH, and
PUCCH; reference signal design for the shortened TTI physical
channel demodulation; and HARQ operation with a sTTI.
[0054] One or more components may contribute to the total end to
end delay for connected WTRUs. These components may include, for
example, one or more of the following: scheduling grant acquisition
time, TTI, processing time, and hybrid-RTT. The transmission of a
request, grant, HARQ feedback, and/or data may be done according to
the timing of blocks or chunks, for example subframes, which may
have a fixed or known duration (e.g., 1 ms). The duration may be
referred to as a TTI. Processing time may be, or may include, the
time needed or used to process (e.g., encode and/or decode) data
and/or control signaling or information. This may be done, for
example, at or by the WTRU and/or the eNB. Data processing time may
be proportional to the TTI and/or transport block (TB) size of the
data.
[0055] Downlink (DL) control channels may be mapped to at least a
portion of a subframe. For example, DL control channels may be
located in (e.g., may be transmitted in) a set of OFDM symbols of a
subframe, such as the first 1-3 or the first 2-4 OFDM symbols of a
subframe. The range of OFDM symbols that may be used (e.g., 1-3 or
2-4) may be based on the system bandwidth. DL control channels may
be located in one or more subframes. In an embodiment, the DL
control channels may be located in every subframe.
[0056] A DL control channel for sTTI resources (e.g., sPDCCH)
scheduling is needed. FIG. 3 is an example of using a legacy EPDCCH
for sTTI resource scheduling. In FIG. 3, a subframe includes a
PDCCH region at the beginning of the sub frame. The subframe also
includes an EPDCCH region occurring in symbols after the PDCCH
across a portion of the bandwidth. The subframe also includes 6
sPDSCH regions occurring across a portion of the bandwidth
allocated for sTTI frequency resources. Each sPDSCH region has
duration of one sTTI.
[0057] As shown in FIG. 3, the use of legacy PDCCH for sTTI
resource scheduling may increase latency depending on sTTI resource
location in a subframe.
Also, the use of legacy EPDCCH for sTTI resource scheduling may not
reduce the latency since a WTRU may need to wait until the end of a
subframe to decode the EPDCCH. If a sPDCCH is located in each sTTI
resource, complexity of blind decoding within a time window (e.g.,
1 ms) may increase due to the additional sPDCCH blind decoding
operations on top of the legacy EPDCCH.
[0058] The number of symbols (e.g., 1-3 or 2-4) that may be used
for DL control channels in a subframe may be determined according
to the overhead of the control channels. The overhead of the
control channels may be the amount of control information to be, or
being transmitted, for example in the subframe. The number of
symbols that may be used may be different in different subframes.
For example, according to downlink control channel overhead,
dynamic resource allocation may enable efficient downlink resource
utilization, which may result in higher system throughput. The DL
control channels that may be transmitted in a subframe may include
one or more of a Physical Control Format Indicator Channel
(PCFICH), a Physical Hybrid-ARQ Indicator Channel (PHICH), and a
Physical Downlink Control Channel (PDCCH).
[0059] A DL control channel resource unit may be defined as one or
more resource elements (REs) that may be contiguous in the
frequency domain. In an embodiment, the DL control channel resource
unit may contain 4 REs. A DL control channel resource element may
be called a REG (Resource Elements Group).
[0060] Referring now to FIGS. 4 and 5, examples of REGs are shown.
FIGS. 4 and 5 show example definitions of REGs according to the
number of cell specific reference signals (CRS), which may be CRS
ports. FIG. 4 illustrates a REG definition in a downlink control
channel region with 2 Tx cell specific reference signals (CRS)
shown as RS0 and RS1. FIG. 5 illustrates a REG definition in
downlink control channel region with 4 Tx CRS shown as RS0, RS1,
RS2, and RS3. If a CRS is located in the same OFDM symbol as a DL
control channel, a DL control channel REG may be comprised of REs
(e.g., 4 REs) that are contiguous with the exception of REs
containing CRS, which may be skipped over. In the examples, 3
symbols are used for the DL control channels, however, other
configurations are possible. The set of symbols that may be used
for DL control channels, for example in a subframe, may be referred
to herein as a DL control channel region.
[0061] A PCFICH may be transmitted in an OFDM symbol (e.g., the
first OFDM symbol or symbol 0) in one or more subframes, which may
include every subframe. The PCFICH may indicate the number of OFDM
symbols that may be used for downlink control channels in the
subframe. The subframe-level dynamic downlink control channel
resource allocation may be performed using the PCFICH. A WTRU may
detect a Control Format Indicator (CFI) from a PCFICH. The downlink
control channel region (e.g., the size of the DL control channel
region) may be defined in a subframe according the CFI value. Table
1 shows an example of CFI codewords that may be detected from the
PCFICH. Table 2 shows examples of downlink control channel resource
allocation according to one or more parameters such as CFI value,
subframe type, frame structure, and system bandwidth. System
bandwidth in the DL may be represented by the number of resource
blocks in the DL, N.sub.RB.sup.DL.
TABLE-US-00001 TABLE 1 Example CFI codewords CFI CFI codeword
<b.sub.0, b.sub.1, . . . , b.sub.31> 1 <0, 1, 1, 0, 1, 1,
0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0,
1, 1, 0, 1> 2 <1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1,
1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0> <1, 1, 0,
1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1,
1, 0, 1, 1, 0, 1, 1> 4 <0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, (Reserved) 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0>
TABLE-US-00002 TABLE 2 Example Number of OFDM symbols used for
PDCCH according to various parameters Number of OFDM Number of OFDM
symbols for PDCCH symbols for PDCCH Subframe when N.sub.RB.sup.DL
> 10 when N.sub.RB.sup.DL .ltoreq. 10 Subframe 1 and 6 for frame
1, 2 2 structure type 2 MBSFN subframes on a 1, 2 2 carrier
supporting PDSCH, configured with 1 or 2 cell-specific antenna
ports MBSFN subframes on a 2 2 carrier supporting PDSCH, configured
with 4 cell-specific antenna ports Subframes on a carrier not 0 0
supporting PDSCH Non-MBSFN subframes 1, 2, 3 2, 3 (except subframe
6 for frame structure type 2) configured with positioning reference
signals Other cases (e.g., 1, 2, 3 2, 3, 4 all other cases)
[0062] A PCFICH may not be transmitted and/or used in some
subframes, for example in a subframe that does not support PDSCH or
in a subframe in which PDSCH or another DL channel begins in a
known symbol or time location. A WTRU may not try to detect the
PCFICH in a subframe in which PCFICH may not be transmitted and/or
used.
[0063] A number of REGs (e.g., 4 REGs) may be used for PCFICH
transmission, for example in the first OFDM symbol in a subframe.
The REGs may be uniformly distributed, in at least part of the
system bandwidth (e.g., the DL system bandwidth) or throughout the
whole system bandwidth. The distribution may exploit frequency
diversity gain.
[0064] Referring now to FIG. 6, a diagram illustrating allocation
of the PCFICH REGs according to a physical cell-ID (PCI). The
starting point of a PCFICH transmission (e.g., in frequency) may be
different according to the PCI. A frequency shift of PCFICH based
on a cell-ID may improve PCFICH detection performance, for example
by avoiding PCFICH collision among multiple neighbor cells.
[0065] A WTRU may begin downlink control channel detection in a
subframe by decoding PCFICH to determine the number of OFDM symbols
for downlink control channels in the subframe. PCFICH detection
error may result in the loss of at least one of a downlink grant,
an uplink grant, and PHICH reception, for example since downlink
control resources may be defined by PCFICH.
[0066] A PHICH may be used to transmit ACK or NACK corresponding to
a PUSCH transmitted in an uplink subframe. A PHICH may be
transmitted in a distributed manner, for example across at least
part of the system bandwidth (e.g., the DL system bandwidth) and at
least some of the OFDM symbols within the downlink control channel
region. The number of OFDM symbols that may be used for PHICH may
be referred to as a PHICH duration. The PHICH duration may be
configurable, for example, by higher layer signaling or broadcast
signaling (e.g., in a MIB or SIB). The PHICH resource position
(e.g., in frequency) may vary according to PCI and/or PHICH
duration.
[0067] Referring now to FIG. 7, a diagram illustrating PCFICH and
PHICH REGs according to PCI is shown. Multiple PHICH groups may
defined or used in a cell. A PHICH group may contain multiple
PHICHs that may have or use orthogonal sequences. The PHICH that
may be intended for a WTRU may be defined dynamically, for example,
with resource information provided in an uplink grant. The uplink
grant may be for the PUSCH, for which the PHICH may include an ACK
or NACK. The resource information may include a lowest PRB index
(l.sub.PRB_RA.sup.lowest_index) and/or DM-RS cyclic shift
(n.sub.DMRS). A two index pair (e.g., PHICH group index:
n.sub.PHICH.sup.group, PHICH sequence index: n.sub.PHICH.sup.seq)
may indicate the PHICH resource for a specific WTRU.
[0068] In an example PHICH index pair (n.sub.PHICH.sup.group,
n.sub.PHICH.sup.seq), each index may be defined as follows:
n.sub.PHICH.sup.group=(l.sub.PRB_RA.sup.lowest_index+n.sub.DMRS)mod
N.sub.PHICH.sup.group Equation (1)
n.sub.PHICH.sup.seq=(.left
brkt-bot.l.sub.PRB_RA.sup.lowest_index/N.sub.PHICH.sup.group.right
brkt-bot.+n.sub.DMRS)mod 2N.sub.SF.sup.PHICH, Equation (2)
where the N.sub.PHICH.sup.group may indicate the number of PHICH
groups available in the system. The N.sub.PHICH.sup.group may be
defined as follows:
N PHICH group = { N g ( N RB DL / 8 ) 2 N g ( N RB DL / 8 )
Equation ( 3 ) ##EQU00001##
where N.sub.g may be information (e.g., 2 bit information) that may
be transmitted via PBCH (Physical Broadcasting Channel) and the
information may be within N.sub.g.di-elect cons.{1/6,1/2,1,2}.
[0069] The orthogonal sequence may be determined according to the
spreading factor. An example is shown in Table 3.
TABLE-US-00003 TABLE 3 Example orthogonal sequence according to
sequence index and spreading factor Orthogonal sequence Sequence
Normal cyclic Extended cyclic index prefix prefix
n.sub.PHICH.sup.seq N.sub.SF.sup.PHICH = 4 N.sub.SF.sup.PHICH = 2 0
[+1 +1 +1 +1] [+1 +1] 1 [+1 -1 +1 -1] [+1 -1] 2 [+1 +1 -1 -1] [+j
+j] 3 [+1 -1 -1 +1] [+j -j] 4 [+j +j +j +j] -- 5 [+j -j +j -j] -- 6
[+j +j -j -j] -- 7 [+j -j -j +j] --
[0070] The HARQ indicator (HI) may be coded, for example as shown
in Table 4. For a positive acknowledgement, HI may equal 1 and for
a negative acknowledgement HI may equal 0.
TABLE-US-00004 TABLE 4 Example HI code words HI HI code word
<b.sub.0, b.sub.1, b.sub.2> 0 <0, 0, 0> 1 <1, 1,
1>
[0071] A PDCCH (or a PDCCH candidate) may be comprised of one or
more Control Channel Element (CCE) resources that may be
consecutive. One CCE may contain a number of REGs such as 9 REGs.
The number of available CCEs (N.sub.CCE) may be defined, for the
example of 9 REGs per CCE, as N.sub.CCE=.left
brkt-bot.N.sub.REG/9.right brkt-bot. where N.sub.REG may be the
number of REGs not assigned to PCFICH or PHICH. Table 5 shows
examples of PDCCH formats according to the number of CCEs where the
CCEs may be consecutive.
TABLE-US-00005 TABLE 5 Example PDCCH formats Number of PDCCH Number
of resource-element Number of format CCEs groups PDCCH bits 0 1 9
72 1 2 18 144 2 4 36 288 3 8 72 576
[0072] A WTRU may monitor or may need to monitor one or more PDCCH
candidates, for example to decode or successfully decode a PDCCH
format, such as a DL Control information (DCI) format, that may be
intended for the WTRU. A WTRU may decode (e.g., blindly decode) or
attempt to decode one or more candidates at each of one or more
aggregation levels. The set of PDCCH candidates a WTRU may monitor,
may decode (e.g., blindly), may attempt to decode, may need to
monitor, may need to decode (e.g., blindly), or may need to attempt
to decode may be a search space. Table 6 shows examples of search
spaces and associated PDCCH candidates.
TABLE-US-00006 TABLE 6 Example search spaces and associated PDCCH
candidates that may be monitored by a WTRU Search space
S.sub.k.sup.(L) Number of Aggregation level PDCCH Type L Size [in
CCEs] candidates M.sup.(L) WTRU- 1 6 6 specific 2 12 6 4 8 2 8 16 2
Common 4 16 4 8 16 2
[0073] The number of CCEs may be different for different PDCCH
formats, for example as shown in Table 5. An aggregation level may
correspond to a number of CCEs, for example in a PDCCH format. A
set of aggregation levels (e.g., {1, 2, 4, 8}) may be supported or
used in a WTRU-specific search space. Another set of aggregation
levels (e.g., {4, 8}) may be supported or used in a common search
space. A WTRU-specific search space may be a search space
configured for a WTRU that the WTRU may monitor. A common search
space may be a search space that may be configured for the cell,
for example in broadcast signaling, that one or more (e.g., all)
WTRUs in the cell may monitor.
[0074] A search space S.sub.k.sup.(L) at aggregation level L may be
defined by a set of PDCCH candidates where, for example, L.di-elect
cons.{1,2,4,8} or L.di-elect cons.{4,8}. For a serving cell on
which PDCCH is monitored, the CCEs corresponding to PDCCH candidate
m of the search space S.sub.k.sup.(L) may be given by:
L{(Y.sub.k+m')mod .left brkt-bot.N.sub.CCE,k/L.right brkt-bot.}+i
Equation (4)
The term i may be defined as i=0, . . . , L-1. The term in may be
defined as m=0, . . . , M.sup.(L)-1. The term M.sup.(L) may be the
number of PDCCH candidates to monitor in the given search space.
For a common search space, the term Y.sub.k may be set to 0, for
example for the two aggregation levels L=4 and L=8.
[0075] For a WTRU-specific search space S.sub.k.sup.(L) at
aggregation level L, the variable Y.sub.k may be defined by:
Y.sub.k=(AY.sub.k-1)mod D Equation (5)
where, for example, Y.sub.-1=n.sub.RNTI.noteq.0, A=39827, D=65537,
k=.left brkt-bot.n.sub.s/2.right brkt-bot., and n.sub.s is the slot
number within a radio frame.
[0076] The value of m' may be defined according to one or more of
the search space type and configuration for use of cross carrier
scheduling. Configuration for use of cross carrier scheduling may
be indicated by configuration with carrier indicator field. When
cross carrier scheduling is not used or configured for a serving
cell, control channels (e.g., carrying grants or ACK/NACK) for the
serving cell may be transmitted and/or monitored on, for example,
the DL control channel region of that serving cell. When cross
carrier scheduling is used or configured for a serving cell,
control channels (e.g., carrying grants or ACK/NACK) for the
serving cell may be transmitted and/or monitored on, for example,
the DL control channel region of another serving cell.
[0077] For example, for the common search space, m' may be defined
as m'=m. For a WTRU-specific search space, and for the serving cell
on which PDCCH is monitored, m' may be defined as
m'=m+M.sup.(L)n.sub.CI. This may be applied when the monitoring
WTRU is configured with a carrier indicator field, for example, for
the serving cell to which the PDCCH candidates apply. The value of
n.sub.CI may be the carrier indicator field value. For a
WTRU-specific search space, and for the serving cell on which PDCCH
is monitored, m' may be defined as m'=m. This may be applicable
when the monitoring WTRU is not configured with carrier indicator
field, for example, for the serving cell to which the PDCCH
candidates apply.
[0078] Resource element (RE) muting may be used in order to avoid
collisions of signals. For a muted RE, puncturing or rate-matching
may be used, for example, in a coding chain perspective. When
puncturing is used, a signal which may be mapped to a punctured RE
may not be transmitted or may be transmitted at zero power in that
RE. When rate-matching is used, mapping of signals to REs may avoid
mapping to certain REs, which may result in other signals not being
transmitted.
[0079] In an example, a N-bit coded bit sequence for a channel, for
example (c.sub.1, . . . , c.sub.N), may be an output of a channel
encoder with a payload or information as an input. The channel
encoder may be any channel code, including, for example, a turbo
code, convolutional code, or Reed-Muller code. The coded bit
sequence may be an input of a mapper.
[0080] A M-symbol modulated symbol sequence, for example (x.sub.1,
. . . , x.sub.M), may be an output of a mapper where the coded bit
sequence is modulated to a modulation scheme (e.g., BPSK, QPSK,
16QAM, or 64QAM). According to the modulation scheme used, the
modulated symbol sequence length M may be equal to or smaller than
N.
[0081] The modulated symbol sequence may be mapped to a set of REs
for the channel according to a predefined order. For example,
x.sub.1, . . . , x.sub.M may be mapped onto M REs, which may be
used for the channel in a predefined order. If the k.sup.th (where
k.ltoreq.M) RE is muted, for example due to a collision, puncturing
may mean that modulated symbol x.sub.k is not be transmitted.
Rate-matching may mean that the mapping skips REs that are muted
and that fewer modulated symbols may be mapped. For one
rate-matched RE, M-1 modulated symbols may be mapped and
transmitted. For example, x.sub.1, . . . , x.sub.M-1 may be
transmitted and one last modulated symbol may not be transmitted
due to the muting of the k.sup.th RE. Puncturing may result in the
loss of coded bits in the positions of the muted REs, while the
rate-matching may result in the loss of coded bits from the last
coded bits.
[0082] Hereinafter, RE muting with puncturing may be referred to as
"RE puncturing" and RE muting with rate-matching may be referred to
as "RE rate-matching." The term "RE muting" may include RE
puncturing and/or RE rate-matching.
[0083] In conventional LTE systems, RE muting may be performed to
avoid collisions between signals of different types in the same
direction. For example, in the DL, PDSCH REs may be muted to avoid
collisions with CSI-RS, and PRS REs may be muted to avoid
collisions with PSS and SSS. In the UL, PUSCH and PUCCH may be
shortened to avoid collision with SRS in the UL.
[0084] In an embodiment, one or more sTTI resource types may be
used. A sTTI resource type may be associated with, and/or may be
determined based on one or more parameters. One parameter may be a
frequency location including at least one of PRB location,
component carrier location, frequency band, and subcarrier
location. Another parameter may be a frequency resource amount used
including at least one of a number of PRBs, a number of
subcarriers, a number of REs, and a number of component carriers.
Another parameter may be a time location including at least one of
a DL or UL symbol location within a subframe, a starting DL or UL
symbol location within a subframe, a subframe number or a starting
subframe number, and a SFN number.
[0085] Another parameter may be a time resource amount including at
least one of a number of DL symbols (e.g., OFDMA symbols) or UL
symbols (e.g., SC-FDMA symbols), a number of slots, a number of
subframes, a number of time samples, and a number of radio frames.
The time resource amount may be a function of or determined based
on the number of sTTIs available in a subframe. Another parameter
may be a spatial resource including at least one of an associated
antenna port number or numbers, reference signal type (e.g., DM-RS
or CRS), associated physical cell-ID, and associated virtual
cell-ID.
[0086] One or more sTTI resource types may be used, configured,
allocated, and/or indicated for a time period. The time period may
be one or more, symbols, subframes, radio frames, or slots. The
time period may be referred to herein as a sTTI time window. The
terms sTTI time period, sTTI window, sTTI resource type time
window, and sTTI time window may be used interchangeably. A sTTI
window may be one or more of: the time period of a sTTI, the time
period of a regular TTI, and/or a subframe.
[0087] A sTTI resource type may refer to resources for a sTTI
physical downlink control channel (sPDCCH), a sTTI physical
downlink shared data channel (sPDSCH), a sTTI physical uplink
shared data channel (sPUSCH), and/or a sTTI physical uplink control
channel (sPUCCH). The terms sTTI resource type and sTTI type may be
used interchangeably. A channel or signal described herein may be
respresented by an abbreviation that begins with s such as sPDCCH,
sPDSCH, sPUSCH and sPUCCH. In the examples and embodiments
described herein, the beginning s may be used to represent short or
sTTI.
[0088] FIG. 8 is a diagram illustrating multiple sTTI resource
types configured in a subframe is shown. More specifically, FIG. 8
shows an example of a resource configuration with multiple sTTI
resource types in a subframe, where a non-overlapped frequency may
be used for different sTTI resource types. A first sTTI resource
type and a second sTTI resource type may be located in
non-overlapped sets of PRBs.
[0089] As described herein, a sTTI resource type may be determined,
configured, or predefined for one or more sTTI physical channels
(e.g., per sTTI physical channel). For example and a first sTTI
resource type (e.g., sTTI type-0) may be used for sPDCCH and a
second sTTI resource type (e.g., sTTI type-1) may be used for
sPDSCH. In another example, a first sTTI resource type may be used
for downlink physical channels and a second sTTI resource type may
be used for uplink physical channels. In another example, a first
sTTI resource type may be used for physical shared data channels
(e.g., sPDSCH and/or sPUSCH) and a second sTTI resource type may be
used for physical control channel (e.g., sPDCCH and/or sPUCCH).
[0090] In another example, a first sTTI resource type may be used
for one or more sTTI physical channels using a first sTTI (e.g.,
sPDSCH using N symbols, where N may be 2) and a second sTTI
resource type may be used for one or more sTTI physical channels
using a second sTTI (e.g., sPDSCH using M symbols, where M may be
7). The sTTI physical channels using the first and second sTTI
resource types may be transmitted and/or received in the same
subframe. The sTTI physical channels using the first and second
sTTI resource types may be intended for and/or received by
different WTRUs (or by the same WTRU).
[0091] While FIG. 8. shows an example where sTTI resources are
overlapped in time, and are not overlapped in frequency, it should
be noted that there are many different possible configurations for
allocating sTTI resources in a subframe. For example, one or more
sTTI resource types may be configured in a subframe and the one or
more sTTI resource types may be non-overlapped in time, frequency,
and spatial resources. In another example, one or more sTTI
resource types may be configured in a subframe and the one or more
sTTI resource types may be fully or partially overlapped in time,
frequency, and/or spatial resources. It should be noted that the
terms resource overlapping and resource sharing may be used
interchangeably. Two or more sTTI resource types may be fully or
partially overlapped in a first resource (e.g., time, frequency, or
spatial) while non-overlapped in a second resource (e.g., time,
frequency, or spatial), where the first resource and the second
resource may be different. Two or more sTTI resource types may be
fully or partially overlapped in time and/or frequency resources
while a different spatial resource may be used for the two or more
sTTI resource types. Two or more sTTI resource types may be fully
or partially overlapped in time while a different frequency
resource may be used for the two or more sTTI resource types. Two
or more sTTI resource types may be fully or partially overlapped in
frequency while a different time resource may be used for the two
or more sTTI resource types. Two or more sTTI resource types may be
allocated to any other combination of overlapping and non-over
lapping, time, frequency, and spatial resources in a sub frame.
[0092] One or more of following parameters may apply for sets of
PRBs. One or more PRB allocation types may be used to determine a
set of PRBs allocated for a sTTI resource type. A first PRB
allocation type may use localized PRBs (e.g., contiguous PRBs) to
allocate a set of PRBs. A second PRB allocation type may use
distributed PRBs (e.g., noncontiguous PRBs) to allocate a set of
PRBs. The PRB allocation type (or PRB locations for a set of PRBs)
may be defined (e.g., predefined) and/or determined based on the
sTTI resource type. The PRB allocation type (or PRB locations for a
set of PRBs) may be configured via higher layer signaling. The PRB
allocation type may be configured for one or each of the sTTI
resource type or configured in a cell-specific manner or
WTRU-specific manner. The PRB allocation type (or PRB locations for
a set of PRBs) may be indicated dynamically in one or each of the
sTTI time windows.
[0093] One or more sTTI resources with the same sTTI resource type
may be used, for example, in a sTTI, sTTI window, regular TTI,
and/or subframe. For example, a first sTTI resource may be
configured in a first frequency location and a second sTTI resource
may be configured in a second frequency location. The first
frequency location and the second frequency location may be
non-overlapped in frequency domain. The first sTTI resource and the
second sTTI resource may be the same sTTI resource type. For
example, one or more of the following may be the same: a time
resource amount, a frequency resource amount, and a spatial
resource.
[0094] A sTTI resource type may refer to resources for multiple
sTTI physical channels such as sPDCCH and sPDSCH, or sPDSCH and
sPUCCH, where the resources of the multiple channels may not
overlap or may not fully overlap, but may be related. For example a
sTTI resource type may be used for sPDCCH and sPDSCH where the
channels may use the same frequency resources, but the sPDSCH may
be after the sPDCCH in time (e.g., by a configured, predetermined,
or known relationship).
[0095] A WTRU may transmit, receive, monitor, attempt to receive,
or attempt to decode, one or more sTTIs in a sTTI time window. A
WTRU may transmit, receive, monitor, attempt to receive, or attempt
to decode, one or more sTTI resources and/or resource types in a
sTTI time window.
[0096] The following description may include a sTTI resource
presence and/or sTTI resource type indication. In an embodiment, a
WTRU may receive or attempt to decode an indication for a sTTI
resource presence and/or one or more sTTI resource types for a sTTI
time window. The WTRU may receive and attempt to decode the
indication in a control channel region that may be located in the
sTTI time window. The indicator may be referred to as a
sTTI-indicator.
[0097] A sTTI-indicator may be or include an indicator for sTTI
resource presence or an indicator for sTTI resource type. Indicator
and indication may be used interchangeably. One or more
sTTI-indicators may be used for one or more sTTI resources. For
example, if multiple sTTI resources are configured or used in a
sTTI time window, the presence of a sTTI resource may be indicated
by an associated sTTI-indicator. The multiple sTTI resources may be
of the same sTTI resource type or a different sTTI resource type.
The sTTI-indicator may be an explicit indication or based on an
event, signaling format, timing or the like.
[0098] One or more control regions (e.g., control channel regions)
may be located in a sTTI time window and a WTRU may receive or
attempt to decode at least one sTTI-indicator in at least one of
the control regions. A control region may comprise a set of time
and/or frequency resources. A control region may carry control
information and/or one or more control channels. The terms control
region and control channel region may be used interchangeably. A
control region that may carry a sTTI-indicator may be a control
region (e.g., the first control region) located at the beginning of
a time period that may be a sTTI time window.
[0099] FIGS. 9 and 10 are diagrams showing control region locations
for a sTTI-indicator. In FIG. 9, the PDCCH region 910 is located at
the beginning of a regular TTI or subframe. The PDCCH region 910
may include an indication 940 of presence and/or resource type and
location of sTTI resources in the subframe. In the example of FIG.
9, a first frequency region includes sTTI type 1 resources 920, and
a second frequency region includes sTTI type-0 resources 930. The
sTTI type 1 resources 920 and the sTTI type-0 resources 930 are
over lapping in time. In this example, the PDCCH region 910
includes an indication 940 of presence and/or resource type and
location of for each sTTI region 920 and 930.
[0100] In FIG. 10 shows a subframe that includes a PDCCH region
1010 at the beginning of the subframe. A control region may be the
first sPDCCH region 1025 within or among multiple sPDCCH regions
1035, 1045 as shown in FIG. 10. The control region may be the first
sPDCCH region within or among multiple sPDCCH regions (e.g., all
the sPDCCH regions) within a time period that may be a sTTI time
window (e.g., a regular TTI or subframe).
[0101] A control region that may carry a sTTI-indicator may be the
PDCCH control region (e.g., legacy PDCCH control region) that may
be located at the first N OFDM symbols of a subframe. The value of
N may be a defined, determined, or configured value (e.g., N=2),
for example, when the subframe contains one or more sTTI resources.
The value of N may be dynamically indicated from the PCFICH. The
PCFICH may be located in the control region (e.g., the first
control region) that may carry a sTTI-indicator.
[0102] A control region that may carry a sTTI-indicator may be the
first sPDCCH in a sTTI time window. For example, M sTTIs may be
used, configured, or available in a sTTI time window. At least one
of the M sTTIs may contain an associated sPDCCH. A WTRU may receive
or attempt to receive at least one sTTI-indicator in the sPDCCH in
the first sTTI of the M sTTIs.
[0103] A WTRU may monitor, attempt to monitor, receive, or attempt
to receive a sTTI-indicator in at least one control region in a
sTTI time window. The WTRU may use a sTTI-indicator to determine
the presence of at least one sTTI resource in the sTTI time window
or another time period. An example of the time period may be when
the WTRU successfully receives or successfully determines the
presence of the sTTI-indicator. Another other possible time period
may be a later sTTI time window.
[0104] The WTRU may determine the presence of at least one sTTI
resource in a sTTI time window, for example based on at least one
of the presence, value, or contents of a sTTI-indicator that may be
received in the sTTI time window or another time period. An example
of another time period may be a previous (e.g., adjacent preceding)
or earlier sTTI time window. If a sTTI resource is configured, in a
sTTI time window, the WTRU may attempt to receive one or more
sPDCCHs within the sTTI resource. If a sTTI resource is not
configured, a WTRU may not attempt to receive at least some sTTI
physical channels in the sTTI time window or other physical
channels that may be in the sTTI time window. Other physical
channels may refer to physical channels other than the one in which
the WTRU monitored, attempted to receive, or received a
sTTI-indicator. A control region that may carry a sTTI-indicator
may be part of or included in a sTTI resource (or resource type)
for which the sTTI-indicator may indicate presence (or lack of
presence).
[0105] The presence of a sTTI resource or a sTTI resource type may
be determined based on one or more of following parameters: system
parameters, which may include one or more of system bandwidth,
physical cell-ID, slot number, subframe number, and SFN number;
WTRU-specific parameters which may include one or more of WTRU-ID
(e.g., C-RNTI, IMSI, sTMSI, etc.); and configuration information
for sTTI that may be signaled in a higher layer signaling (e.g.,
MIB, SIB, or WTRU-specific RRC signaling).
[0106] The following description may include sTTI resource
configuration mechanisms. A sTTI resource may be configured and/or
used. One or more sTTI resources may be configured via higher layer
signaling. A sTTI resource may be configured with a time/frequency
location. A sTTI resource may refer to a resource that may carry at
least one sTTI physical channel (e.g., sPDCCH, sPDSCH, sPUCCH,
sPUSCH).
[0107] One or more sTTI resources may be configured via a DCI. A
DCI that may configure one or more sTTI resources may be monitored
by a WTRU, for example, periodically or at configured or
predetermined times. A DCI scrambled with a RNTI associated with at
least one sTTI transmission may be used. The DCI may, for example,
be referred to as sTTI-RNTI. For example, a DCI scrambled with
sTTI-RNTI may be monitored in a subframe, a set of subframes, an
SFN, and/or a set of SFNs (e.g., a certain set of SFNs or a set of
SFNs that satisfy certain criteria).
[0108] The DCI may configure one or more sTTI resources. For
example, a DCI scrambled with sTTI-RNTI may be transmitted (e.g.,
by a base station) and/or monitored by a WTRU in a first subframe
of each radio frame. The set of subframes or SFNs in which to
monitor for sTTI-RNTI may be configured. A DCI scrambled with
sTTI-RNTI may be transmitted (e.g., by a base station) and/or
monitored by a WTRU, for example in the set of subframes or SFNs
that may be configured and/or used for sTTI-RNTI.
[0109] A sTTI resource may be configured by a base station. A WTRU
may receive a sTTI resource configuration, for example from a base
station. A WTRU may use (e.g., transmit in, receive in, or attempt
to receive in) a sTTI resource that may be configured by a base
station or other network entity.
[0110] A base station may transmit in a sTTI resource, for example,
in the DL. A WTRU may receive or attempt to receive a transmission
in a sTTI resource, for example in the DL. A WTRU may transmit in a
sTTI resource, for example in the UL. A base station may receive or
attempt to receive a transmission in a sTTI resource, for example
in the UL.
[0111] An sTTI-indicator may be based on, transmitted on, or
associated with PHICH resources. In an embodiment, one or more
PHICH resources may be located in a control region such as a a
PDCCH region or a sPDCCH region, and such region may carry or may
be used to provide a sTTI-indicator. For example, one or more sTTI
resources may be configured and the presence of a sTTI resource may
be indicated in a sTTI time window by a sTTI-indicator. One or more
PHICH resources (e.g., resources that may be configured for,
reserved for, or used for PHICH) may be used to carry at least one
sTTI-indicator. One or more PHICH resources may be configured for
and/or used for a sTTI-indicator.
[0112] A PHICH resource may be represented by a PHICH group index
n.sub.PHICH.sup.group and a PHICH sequence index within the PHICH
group Tables 7 and 8 show examples of a sTTI-indicator using one or
more of PHICH resources. Table 7 shows an example of a
sTTI-indicator using one or more PHICH resources for sTTI resource
presence.
TABLE-US-00007 TABLE 7 sTTI-indicator using one or more PHICH
resources for sTTI resource presence sTTI-indicator
n.sub.PHICH.sup.group n.sub.PHICH.sup.seq HI Configuration 1 0 0 A
first sTTI resource is present 1 0 1 A first sTTI resource is not
present 2 0 0 A second sTTI resource is present 2 0 1 A second sTTI
resource is not present
[0113] Table 8 shows an example of sTTI-indicator using one or more
PHICH resources for sTTI resource presence and sTTI resource type
indication.
TABLE-US-00008 TABLE 8 sTTI-indicator n.sub.PHICH.sup.group
n.sub.PHICH.sup.seq HI Configuration 1 0 0 A (e.g., a first) sTTI
resource is present and it is type-0 sTTI resource (e.g., 1 sTTI =
2 symbols) 1 0 1 A (e.g., a first) sTTI resource is present and it
is type-1 sTTI resource (e.g., 1 sTTI = 4 symbols) 1 4 0 A (e.g., a
first) sTTI resource is present and it is type-2 sTTI resource
(e.g., 1 sTTI = 7 symbols) 1 4 1 A (e.g., a first) sTTI resource is
not present
[0114] It should be noted that Table 7 and Table 8 provide
non-limiting examples of using PHICH resources to indicate sTTI
resource presence and/or sTTI resource type.
[0115] The transmission and/or reception of the indicated HARQ
Indicator (HI) codeword using the indicated PHICH sequence in the
indicated PHICH location, according to the indicated PHICH group,
may correspond to the indicated sTTI configuration (e.g., in the
sTTI window of the PHICH transmission and/or reception).
[0116] When using a PHICH resource to carry a sTTI-indicator, one
or more of the following parameters may apply. A sTTI-indicator for
a first sTTI resource and a sTTI-indicator for a second sTTI
resource may be in a different PHICH group and/or use a different
PHICH sequence. A sTTI-indicator for a first sTTI resource type and
a sTTI-indicator for a second sTTI resource type may be in a
different PHICH group and/or use a different PHICH sequence. HI
code words may be used to indicate the presence of a sTTI resource
or sTTI resource type. Even-numbered or odd-numbered PHICH
sequences may be used for sTTI-indicator. Two PHICH sequences with
a maximum distance (e.g., index 0 and 4 for normal CP) or a minimum
distance (e.g., consecutive two sequence numbers) may be used to
indicate the presence of a sTTI resource.
[0117] Based on reception of a sTTI-indicator using PHICH
resources, a WTRU may determine that a sTTI resource or resource
type is present, for example, in a sTTI window such as the sTTI
window in which the sTTI-indicator or PHICH resources are received.
A WTRU may monitor, attempt to receive, and/or receive a sTTI
resource when the WTRU determines that a sTTI resource is present.
A WTRU may monitor, attempt to receive, and/or receive a sTTI
resource according to a sTTI resource type when the WTRU determines
that a sTTI resource of the sTTI resource type is present.
[0118] One or more PHICH resources that may be used for at least
one sTTI-indicator may be determined based on at least one of the
following parameters: system parameters that may include one or
more of system bandwidth, PHICH configurations, physical cell-ID,
subframe number, and/or SFN number; WTRU-specific parameters that
may include one or more of WTRU-ID (e.g., C-RNTI, full or partial
IMSI, sTMSI, etc.); and configuration information for sTTI that may
be signaled in a higher layer signaling (e.g., MIB, SIB, or
WTRU-specific RRC signaling). A PHICH resource that may carry a
sTTI-indicator may be part of or included in a sTTI resource (or
resource type) for which the sTTI-indicator may indicate presence
(or lack of presence).
[0119] A signal may be used to convey a sTTI-indicator. The term
sTTI-indicator signal may be used to represent a signal that may be
used as a sTTI-indicator. A sTTI-indicator signal may be a
predefined, configured, or known signal. A sTTI-indicator signal
may be associated with one or more sTTI resources and/or sTTI
resource types. Presence of a sTTI-indicator signal may indicate
presence of the associated sTTI resources and/or sTTI resource
types in a sTTI window, such as the sTTI window in which the
sTTI-indicator signal is present.
[0120] A sTTI-indicator signal may be transmitted in a known
location. For example, a predefined signal may be transmitted in a
known location and the presence of the predefined signal (e.g.,
sTTI-indicator signal) may determine the presence of a sTTI
resource.
[0121] The sTTI-indicator signal may be located in N.sub.sTTI
symbols (e.g., the first N.sub.sTTI symbols) of a sTTI time window
or a sTTI resource. N.sub.sTTI may be a positive integer number,
including 1. N.sub.sTTI may be predefined or configured via higher
layer signaling. N.sub.sTTI may be determined as a function of at
least one of the following parameters: a time resource amount of
the associated sTTI resource; a sTTI window length; a subframe
number, a slot number, and/or SFN; and system parameters including
frame structure (e.g., TDD, FDD), system bandwidth, and/or physical
or virtual cell-ID. N.sub.sTTI may be indicated dynamically from an
associated control channel (e.g., legacy PDCCH).
[0122] The sTTI-indicator signal may be a PCFICH. The
sTTI-indicator signal may be transmitted in a sPDCCH region (e.g.,
the first sPDCCH region) within a sTTI time window. The
sTTI-indicator signal may be a known sequence (e.g., Zadoff-Chu
sequence, PN sequence, Golay sequence).
[0123] A WTRU may attempt to receive, receive, decode or attempt to
decode a sTTI-indicator signal to determine the presence of one or
more sTTI resources. The WTRU may monitor, receive, attempt to
receive, decode and/or attempt to decode one or more sTTI resources
(e.g., sTTI channels such as sPDCCH), for example when the WTRU
determines that one or more sTTI resources are present. The WTRU
may monitor, receive, attempt to receive, decode and/or attempt to
decode one or more sTTI resources (e.g., sTTI channels such as
sPDCCH) in the sTTI window of the sTTI indicator signal when the
WTRU determines that one or more sTTI resources are present based
on the reception and/or decoding (e.g., successful reception and/or
decoding) of the sTTI-indicator signal.
[0124] A WTRU may skip reception of (e.g., not attempt to monitor,
receive, and/or decode) a sTTI resource (e.g., sPDCCH and/or
sPDSCH) if the WTRU determines that no (or no additional) sTTI
resources are present. A WTRU may skip reception of a sTTI resource
in a sTTI window if the WTRU determines that no (or no additional)
sTTI resources are present in the sTTI window. A WTRU may determine
that no (or no additional) sTTI resources are present (e.g., in a
sTTI window) if the WTRU does not detect, receive, or decode a
sTTI-indicator signal.
[0125] A WTRU may assume that no sPDCCH and/or sPDSCH is
transmitted in a sTTI window in which the WTRU does not detect,
receive, or decode a sTTI-indicator or sTTI-indicator signal in the
sTTI window or time that corresponds to the sTTI window.
[0126] The reception of one or more sTTI resources when one or more
sTTI resources are present may include at least one of the
following: monitoring sPDCCH for a downlink DCI (e.g., DCI
indicating a DL grant or other DL request or allocation) and/or a
uplink DCI (e.g., DCI indicating an UL grant or other UL request or
allocation) in the associated sTTI resources; and reception of one
or more sPDSCH in the scheduled time, frequency, and/or spatial
resources.
[0127] In another embodiment, a set of REGs in a control region
(e.g., PDCCH region or sPDCCH region) that is within a sTTI time
window may be reserved or used for the sTTI-indicator signal. The
set of REGs may be distributed over a system bandwidth or part of a
system bandwidth. The set of REGs may be associated with a CCE
number (e.g., a certain CCE number that may be configured and/or
known). The set of REGs may be determined based on at least one of
the following parameters: system parameters (e.g., physical or
virtual cell-ID, system bandwidth), sTTI resource type (e.g.,
time/frequency/spatial resources, sTTI length), and WTRU-specific
parameters (e.g., WTRU-ID, C-RNTI).
[0128] A Down Link Control Information (DCI) message may be used to
configure sTTI resources. In an embodiment, a DCI may be used to
indicate the presence of one or more sTTI resources. For example, a
DCI may be used to indicate the presence of one or more sTTI
resources in a sTTI time window. A DCI in a sTTI time window may be
used to indicate the presence of one or more sTTI resources in the
same sTTI time window or another time period, such as another sTTI
window.
[0129] One or more sTTI resources may be configured via higher
layer signaling. The presence of one or more sTTI resources (e.g.,
one or more of the configured sTTI resources) in a sTTI time window
may be indicated in a DCI (e.g., a DCI in the sTTI time window or
another time period such as a previous sTTI time window). The DCI
may be transmitted in a control region within a sTTI window. For
example, the DCI may be transmitted in a legacy PDCCH region within
a sTTI window. The DCI may be monitored in a common search space of
a control region (e.g., legacy PDCCH region). Alternatively, the
DCI may be monitored in a set (e.g., a predetermined set or
configured set) of PDCCH resources (e.g., legacy PDCCH resources).
For example, a set of predetermined or configured CCEs (e.g., CCE
#16-32) may be used. The DCI may be scrambled with a sTTI specific
RNTI (e.g., sTTI-RNTI). The DCI may indicate the presence of a sTTI
resource and/or the associated sTTI resource type. The presence of
a sTTI resource may be determined based on a sTTI specific RNTI
used. For example, one or more sTTI specific RNTIs may be used to
indicate the presence of one or more sTTI resources. Each sTTI
resource may be associated with a specific sTTI-RNTI. A bitmap may
be used in the DCI to indicate which sTTI resources are present in
a sTTI time window.
[0130] A DCI may be used to configure a sTTI resource within a sTTI
time window. For example, time, frequency, and/or spatial resources
for a sTTI resource may be indicated in the DCI.
[0131] A downlink control channel, referred to as a sPDCCH, may be
associated with one or more sTTIs. The terms sPDCCH, downlink
control channel for sTTI, downlink control information for sTTI,
sTTI DCI, and sDCI may be used interchangeably.
[0132] A sPDCCH may be located in a sTTI resource. A sTTI resource
may be, or may include, at least one sPDCCH. A sPDCCH may be or may
be referred to as a sTTI resource. A sPDCCH may be, or may be
referred to as a part of a sTTI resource. The terms sPDCCH
resource, sPDCCH region, sPDCCH symbols, sPDCCH subcarriers, and
sPDCCH REs may be used interchangeably.
[0133] A sPDCCH resource may be associated with one or more sTTIs.
For example, a sPDCCH may be associated with one or more sPDSCHs
located in sTTIs that may be the same as or different from each
other or the same as or different from the sTTI of the sPDCCH. A
sPDCCH may include scheduling information for the associated one or
more sPDSCHs.
[0134] A sTTI may include at least one sPDCCH. A sTTI may include
at least one sPDSCH that may be associated with a sPDCCH that may
be included in the sTTI. For example, in a sTTI, a subset of sTTI
resources may be used for sPDCCH and the rest of the sTTI resources
may be used for sPDSCH. A WTRU may monitor or attempt to decode
sPDCCH in a sTTI or a sPDCCH region. A sPDCCH may indicate one or
more scheduled sPDSCHs.
[0135] A WTRU may not monitor, or may skip monitoring, sPDCCH in
resources (e.g., in a sTTI) where sPDSCH may be scheduled. The WTRU
may determine where sPDSCH resources are scheduled (e.g., in a
sTTI) based on reception of a sPDCCH including sPDSCH scheduling
(e.g., for the sTTI). For example, two or more sTTIs, which may be
of the same or different length, may overlap. Each sTTI may include
a subset of resources for sPDCCH and a subset of resources for
sPDSCH. For each sTTI, the resources for sPDCCH and sPDSCH may not
overlap. The resources for sPDSCH of the first sTTI may overlap
with the sPDCCH resources of the second sTTI. If sPDSCH resources
are determined by the WTRU to be scheduled in the first sTTI, the
WTRU may not monitor sPDCCH in the sPDCCH resources in the second
sTTI. This may be due to an overlap with the sPDSCH resources
scheduled in the first sTTI. The WTRU may monitor sPDCCH in the
sPDCCH resources in the second sTTI when the sPDCCH resources in
the second TTI are not overlapped with scheduled sPDSCH resources
(e.g., in the first sTTI). The WTRU may determine that the sPDCCH
resources in the second TTI are not overlapped with scheduled
sPDSCH resources.
[0136] A sTTI window may include one or more sTTIs that may or may
not overlap. The sTTIs in a sTTI window may be the same or
different lengths. A control channel (e.g., PDCCH or sPDCCH) or
control information (e.g., DCI or sDCI) may indicate potential
scheduling that may be present in a sTTI window (e.g., regular TTI
or subframe). The potential scheduling may be or may include at
least one of the following parameters: the number of sTTIs, the
number of sPDSCHs, the number of sPDCCHs, the number of sTTI
control regions, and/or the number of sPDCCH regions. A WTRU may
monitor sPDCCH in one or more sTTIs or one or more sPDCCH regions
in a sTTI window. A WTRU may not monitor a sPDCCH in a sTTI window
after receiving sPDSCH scheduling in or for the sTTI window. A WTRU
may not monitor sPDCCH in a sTTI window in resources overlapped
with a scheduled sPDSCH. This may occur, for example, when the WTRU
receives scheduling for the sPDSCH and/or determines the sPDSCH is
scheduled.
[0137] A sPDCCH (e.g., sDCI) may indicate a number of sPDSCHs that
may be within a set, such as {n1, n2, n3, n4}. The set may be
configured, defined, and/or determined. The number of sPDSCHs
(e.g., n2) may determine the number of sTTIs (e.g., consecutive
sTTIs) that may be used for sPDSCH scheduling in, for example, a
sTTI window. A WTRU may monitor sPDCCH in a sTTI or a sPDCCH
region, for example when a WTRU is not scheduled (e.g., in the sTTI
window or in resources overlapping the sPDCCH resources).
[0138] A sPDCCH (e.g., sDCI) may indicate a set of sTTIs within a
sTTI time window for the scheduling of sPDSCHs. For example, a
bitmap may be used to indicate which sTTI or sTTIs within a sTTI
time window may carry a sPDSCH. A sPDCCH region in a sTTI may be
used for sPDSCH transmission, for example when the sPDSCH may be
scheduled in a previous sTTI (e.g., by a sPDCCH in a sPDCCH region
in a previous sTTI). A sPDCCH region which may be used for the
scheduling of sPUSCH may be reserved and/or may not be used for
sPDSCH transmission. It should be noted that, a PDCCH may be
substituted for sPDCCH and a DCI may be substituted for sDCI.
[0139] FIG. 11 is a diagram illustrating examples of sPDCCH and
sPDSCH association per sTTI. The sPDCCH may be located in each sTTI
and the associated sPDSCH may be scheduled from the sPDCCH located
in the same sTTI.
[0140] FIG. 12 is a diagram illustrating sPDCCH and sPDSCH
association with multiple sTTIs. A sPDCCH may be associated with
one or more sPDSCHs, and the number of sPDSCHs associated with a
sPDCCH may be determined based on a sPDCCH cycle.
[0141] FIG. 13 is a diagram illustrating the use of PHICH resources
as sTTI indicators. One or more sTTI resources may be configured
via higher layer signaling. A WTRU may receive one or more sTTI
indicators associated with one or more sTTI resources in a
subframe. The WTRU may monitor sPDCCH in one or more sTTI resources
based on the configuration indicated from sTTI indicators. The WTRU
may receive sPDSCH or transmit sPUSCH based on scheduling
information from a DCI in sPDCCH.
[0142] A sPDCCH cycle may be the time between sPDCCH regions. A
sPDCCH cycle may be the time period during which a sPDCCH region
may be present. A sPDCCH cycle may indicate the number and/or
location (e.g., time location) of the sPDCCH regions, for example
in a sTTI window (e.g., normal TTI or subframe).
[0143] One or more of the following parameters may apply for sPDCCH
configuration. A sPDCCH cycle may be determined based on system
parameters, WTRU-specific parameters, and/or sTTI resource
configuration information. A sPDCCH cycle may be determined as an
integer multiple of sTTI length. A different sPDCCH cycle may be
used for sTTI resources (e.g., different sTTI resources) that may
be configured and/or used. A sDCI may be associated with one or
more sPDSCHs.
[0144] A sDCI may be associated with a sPDSCH and one or more sDCI
may be transmitted or monitored in a sPDCCH region. For example, a
sDCI (or DCI) may include or identify an associated sTTI, sPDSCH,
or sPDSCH region (e.g., an associated sTTI, sPDSCH, or sPDSCH
region) implicitly or explicitly. For example, a sPDCCH or sPDCCH
region may be associated with one or more sTTIs, sPDSCHs, and/or or
sPDSCH regions, where a scheduling information for a sTTI, sPDSCH,
and/or a sPDSCH region may be received via a sDCI in the associated
sPDCCH or sPDCCH region.
[0145] A RNTI may be used to indicate a sTTI (e.g., a sTTI length
or a sTTI time location). For example, the CRC of a DCI or sDCI may
be scrambled with a RNTI that may correspond to an sTTI that may be
used in a sTTI window. A RNTI associated with a specific sTTI may
be used for a sDCI. The RNTI may indicate the sTTI length (or a
sTTI time location) for the one or more sPDSCHs associated with the
sDCI. A RNTI associated with a specific sTTI may be used to
indicate the sTTI for sPDCCH monitoring or the sPDCCH cycle in, for
example, a sTTI window.
[0146] For example, a set of RNTIs may be used. Each RNTI may be
associated with a sTTI, sTTI length, sPDCCH cycle, and/or sPDSCH
region. A WTRU may monitor one or more sPDCCHs or sPDCCH regions
according to the sTTI length or sPDCCH cycle indicated by the RNTI.
A WTRU may monitor one or more sPDCCHs or sPDCCH regions according
to the sTTI length or sPDCCH cycle indicated by the RNTI. A WTRU
may obtain the sTTI length of a sPDSCH region from the RNTI. The
WTRU may use the sTTI length to receive and/or decode a scheduled
sPDSCH.
[0147] A RNTI may be used to indicate or identify a sPDSCH or
sPDSCH region (e.g., by CRC scrambling with the corresponding
RNTI). A RNTI may be used to indicate the time and/or frequency
location of one or more sPDCCH regions (e.g., by CRC scrambling
with the corresponding RNTI). A WTRU may determine the location of
a sPDCCH region and/or sPDSCH region from a RNTI. A WTRU may
monitor, receive, attempt to receive, decode, and/or attempt to
decode a sPDCCH in the determined location. A WTRU may receive
and/or decode a scheduled sPDSCH from the determined location. The
terms sPDSCH, sPDSCH region, and sPDSCH in a sTTI may be used
interchangeably.
[0148] A location (e.g., starting control channel element (CCE)
number and/or sPDCCH candidate number) of a sPDCCH candidate that
may carry a sDCI may determine the associated sTTI location (e.g.,
the associated sPDSCH region). A WTRU may determine the location of
the associated sPDSCH from the location of the sPDCCH. The WTRU may
receive and/or decode a scheduled sPDSCH from the determined
location. A bit field in a sDCI may be used to indicate the
associated sPDSCH region.
[0149] In a sTTI, a signal (e.g., predefined or known signal) may
be transmitted to indicate the presence of sPDCCH in at least the
sTTI. The signal may be transmitted in a location (e.g., predefined
or known location) within a sTTI. For example, a PCFICH may be
transmitted in a symbol (e.g., the first symbol) of a sTTI to
indicate presence of sPDCCH in at least the sTTI. When the signal
is present or determined by a WTRU to be present, the WTRU may
monitor sPDCCH in at least the sTTI. The signal may indicate at
least one of the following: a presence of sPDCCH in the sTTI; a
presence of sPDCCH in at least one sTTI or sPDCCH region in the
sTTI window; the sTTI length; a sPDCCH cycle within the sTTI time
window; and a sTTI length for sPDSCH. The signal may be transmitted
in a previous sTTI or sTTI window. The signal may indicate sPDCCH
presence and/or one or more of the parameters above for a
subsequent or later sTTI or sTTI window.
[0150] The following description may include a sPDCCH resource
indicator DCI. In an embodiment, a DCI in a certain sPDCCH search
space in each sTTI resource may indicate the presence of a sPDCCH
resource. In the indicated sPDCCH resource, a WTRU may need to
monitor a DCI which may be associated with a sTTI resource
allocation. The DCI to indicate the presence of a sPDCCH resource
in a sTTI may be referred to as config-DCI, configuration DCI, or
monitoring indicator.
[0151] For example, one or more potential sPDCCH resources may be
configured, predefined, used, or determined in a subframe. Whether
a WTRU may need to monitor one or more sPDCCH candidates for sPDSCH
and/or sPUSCH in the potential sPDCCH resource may be determined
based on the config-DCI. It should be noted that the term
"potential sPDCCH resource" may be used interchangeably with the
term "sTTI resource" and still be consistent with this
disclosure.
[0152] The config-DCI may be monitored in one or more sPDCCH
candidates. The one or more sPDCCH candidates which may carry
config-DCI may be located in a known location in each potential
sPDCCH resource.
[0153] A single sPDCCH candidate may be used. The time/frequency
location and/or (E)CCE aggregation level of the sPDCCH candidate
which may carry config-DCI may be predetermined. For example, a
first sPDCCH candidate with a largest (E)CCE aggregation level in a
set may be used for a config-DCI. The time/frequency location
and/or (E)CCE aggregation level of the sPDCCH candidate that may
carry config-DCI may be configured via higher layer signaling
and/or may be dynamically indicated from a DCI from a control
channel region such as a legacy control channel region (e.g.,
PDCCH).
[0154] A search space may be defined for config-DCI monitoring. The
search space may be common for all WTRUs or for a group of WTRUs.
The number of blind decoding attempts for config-DCI monitoring
(e.g., the number of sPDCCH candidates for monitoring config-DCI)
may be determined as Nbd. Nbd may be predefined, configured, or
determined based on at least one of the following: a number of
potential sPDCCH resources within an sTTI time window, a number of
symbols used for an sPDCCH resource; a number of (E)CCEs; or a
number of PRBs used for an sPDCCH resource. A common search space
may be configured or predefined. A common search space may be
determined based on at least one of the following: a sTTI length; a
number of sTTI resources in a sTTI time window (e.g., subframe); or
the number of potential sPDCCH resources in a sTTI time window.
[0155] A specific RNTI may be used for a config-DCI. For example, a
config-DCI-RNTI may be used to scramble the CRC of the
config-DCI.
[0156] A WTRU may receive, monitor, or attempt to decode one or
more sPDCCH candidates which may carry a config-DCI in a potential
sPDCCH resource. If a WTRU receives the config-DCI in a potential
sPDCCH resource, the WTRU may start monitoring sPDCCH candidates
for sPDSCH and/or sPUSCH. If a WTRU does not receive a config-DCI
in a potential sPDCCH resource, the WTRU may skip monitoring sPDCCH
candidates for sPDSCH and/or sPUSCH.
[0157] The presence of config-DCI in a potential sPDCCH resource
may determine the presence of sPDCCH candidates for sPDSCH and/or
sPUSCH scheduling. The config-DCI may include one or more of the
following: the sPDCCH candidate set of the subset that may be
monitored by a WTRU for sPDSCH and/or sPUSCH; the aggregation
levels that may be monitored by a WTRU; or a sPDCCH resource for
monitoring of one or more DCIs associated with sPDCCH and/or
sPUSCH.
[0158] The number of sPDCCH candidates (Mbd) for sPDSCH and/or
sPUSCH may be indicated from an associated config-DCI. For example,
a WTRU may monitor Nbd sPDCCH candidates for a config-DCI in a
potential sPDCCH resource and the WTRU may monitor Mbd sPDCCH
candidates, wherein Mbd may be indicated from the config-DCI.
[0159] A WTRU may monitor Mbd sPDCCH candidates for sPDSCH and/or
sPUSCH in a sPDCCH resource. A WTRU may determine Mbd (e.g, a value
of Mbd). Mbd may be determined by, from, or based on the number of
sPDCCH candidates (Nbd) for config-DCI. Mbd may be determined by,
from, or based on the number of potential sPDCCH resources in which
a config-DCI may be received. Mbd may be determined by, from, or
based on the number of potential sPDCCH resources in a sTTI time
window (e.g., subframe). Mbd may be determined by, from, or based
on the number of sPDCCH resources indicated for monitoring within
the potential sPDCCH resources. For example, a WTRU may be
indicated to monitor a subset of Nsp potential sPDCCH resources and
the Mbd may be determined based on the number of sPDCCH resources
in the subset. Mbd may be determined by, from, or based on the
number of PRBs configured, used, or determined for at least one
potential sPDCCH resource. Mbd may be determined by, from, or based
on the sTTI length associated with a potential sPDCCH resource.
[0160] Nsp potential sPDCCH resources may be configured,
determined, used, or indicated and a WTRU may receive, monitor, or
attempt to decode at least one of Nsp potential sPDCCH resources
for config-DCI. Each potential sPDCCH resource may be configured or
determined based on one or more parameters that may include at
least one of the following: a starting symbol, a number of symbols,
a number of PRBs, a number of (E)CCEs, or a reference signal type
associated with or that may be used for demodulation. The starting
symbol of sPDCCH resources may be determined as a function of the
number of sPDCCH resources within a sTTI time window (e.g.,
subframe). The number of symbols for a sPDCCH resource may be
predetermined, configured, or indicated, for example by a base
station. The potential sPDCCH resources may be configured in a
WTRU-specific manner. sTTI window and sTTI time window may be used
interchangeably.
[0161] In another embodiment, one or more sPDCCH resources in a
sTTI time window may be activated or deactivated for monitoring.
Activation and/or deactivation may be configured, received, or
indicated via a higher layer signaling (e.g., via RRC signaling, or
via a MAC-CE). For example, one or more sPDCCH regions may be used
and each sPDCCH region may include one more sPDCCH resources. One
or more sPDCCH regions may be located in different frequency
resources which may be non-overlapped in frequency within a sTTI
time window.
[0162] A WTRU may receive an indication via higher layer signaling
(e.g., MAC-CE) in a subframe n-k. The indication may or may
indicate to activate (or deactivate) one or more sPDCCH regions
associated with a subframe n. The WTRU may monitor (or skip
monitoring) sPDCCH resources in one or more sPDCCH regions
activated (or deactivated) from the indication or higher layer
signaling in the subframe n. The variable k may be a predefined
number or a configured number.
[0163] A WTRU may be associated with a (e.g., a single) sPDCCH
region, where one or more sPDCCH resources (or potential sPDCCH
resources) may be used. The one or more sPDCCH resources within a
sPDCCH region may be located in different times (e.g., in different
time locations). The Config-DCI may be monitored by WTRUs in each
potential sPDCCH resource if the associated sPDCCH region is
activated.
[0164] A sPDCCH (or sPDCCH region) may include one or more sPDCCH
candidates. For example, a sPDCCH region in a sTTI may include
N.sub.sPDCCH candidates, where N.sub.sPDCCH may be determined based
on at least one of the following parameters. A parameter may be a
sPDCCH resource configuration that may include or identify time
and/or frequency resources that may be used. A parameter may be a
sTTI resource configuration that may include or identify time
and/or frequency resources that may be used. A parameter may be one
or more system parameters. A parameter may be a number of available
resource elements (REs). The number of available REs may, for
example, exclude REs that may be used for at least one of
cell-specific reference signals, CSI-RS, DM-RS, and RS for
sTTI.
[0165] A sPDCCH candidate may carry a sDCI that may be used for at
least one the following: a scheduling of one or more sPDSCHs;
scheduling of one or more sPUSCHs; a system information update
indication; a sPDCCH order to initiate PRACH transmission; and an
activation or deactivation of semi-persistent scheduling of sPUSCH
or sPDSCH.
[0166] A sPDCCH candidate may be determined based on one or more
short-TTI control channel elements (sCCE). One or more sPDCCH
candidates may be used, transmitted, and/or monitored in a sPDCCH
region. A sPDCCH candidate may be determined based on at least one
of the following parameters: the number of sCCEs used, a starting
sCCE, a starting sCCE and the number of sCCEs used, a sDCI type
carried, and a sCCE type (e.g., localized or distributed).
[0167] A sCCE may be determined or defined as a set of REs within a
sPDCCH region. For example, a sCCE may be defined or determined as
consecutive N.sub.sCCE,RE REs in a PRB-pair in a downlink OFDM
symbol. One or more of the following parameters may apply. The
N.sub.sCCE,RE may be 12. The number of sCCEs in a sPDCCH region may
be determined based on the number of PRBs and the number of OFDM
symbols used for the sPDCCH region. The reference signal type,
antenna port number, and/or the number of antenna ports used for a
sCCE may be determined based on (or as a function of) at least one
of the following: the sTTI resource type; system parameters,
WTRU-specific parameters, the associated PRB number, and a
transmission mode (e.g., CRS based transmission mode or DM-RS based
transmission mode) used for the associated sPDSCH transmission. A
sCCE may be determined, defined, and/or configured with one or more
short-TTI resource element groups (sREG).
[0168] In another embodiment, a subset of nPDCCH resources may be
used as a sPDCCH resource. For example, Ncce (E)CCEs may be located
in an nPDCCH region and a subset of (E)CCEs may be used for sPDCCH
transmission. The subset of (E)CCEs may be determined based on one
or more of following parameters. A predefined set of (E)CCEs may be
used. For example, the first Ns (E)CCEs (except for the (E)CCEs
used for common search space) may be used as a set of (E)CCEs for
sPDCCH transmission.
[0169] A first Ncom (E)CCEs may be used for the nPDCCH common
search space and the (E)CCEs from Ncom+1 to Ncom+Ns may be used for
sPDCCH transmission. In an example, Ncom may be 16. A WTRU may
attempt to decode, monitor, or receive nPDCCH candidates, which may
not include the one or more (E)CCEs used for sPDCCH. For example,
if a nPDCCH candidate in a WTRU-specific search space includes one
or more (E)CCEs for sPDCCH transmission, a WTRU may skip monitoring
the nPDCCH candidate.
[0170] A subset of (E)CCEs may be configured via higher layer
signaling. A starting (E)CCE number and/or the number of (E)CCEs
may be configured, for example via higher layer signaling. The
subset of (E)CCEs may be determined as a function of Ncce. The
subset of (E)CCEs may be dynamically indicated from a DCI in a
common search space. The subset of (E)CCEs may be replaced by
(E)REG or (E)CCE/(E)REG.
[0171] An sPDCCH search space may be provided and/or used. The
sPDCCH search space may include one or more sPDCCH candidates. The
sPDCCH search space may be cell-specific, WTRU-specific, and/or
physical channel specific. A sPDCCH search space may include one or
more sPDCCH candidates that may be associated with one or more
sPDCCH search space types (e.g., cell-specific, WTRU-specific,
and/or physical channel specific).
[0172] A WTRU may attempt to decode, monitor, receive, or attempt
to receive the sPDCCH candidates within a certain sPDCCH search
space that may be associated with the WTRU. The sPDCCH candidates
within a certain sPDCCH search space may be blindly decoded for a
certain sDCI scrambled with a RNTI that may be associated with the
WTRU. The number of blind decoding attempts within a certain sPDCCH
search space may be the same as the number of sPDCCH candidates in
the sPDCCH search space.
[0173] In an embodiment, a sPDCCH search space may be defined,
configured, or determined per sTTI time window. For example, a sTTI
time window may include one or more sPDCCH regions and a WTRU may
monitor or attempt to decode one or more sPDCCH regions within a
sTTI time window.
[0174] In an example, a total number of blind decoding attempts
(e.g., a total number of sPDCCH candidates) within a sTTI time
window may split into (or across or among) the number of sPDCCH
regions. If the number of sPDCCH regions is increased, the number
of blind decoding attempts (e.g., the number of sPDCCH candidates)
in a sPDCCH region may be decreased. The number of sPDCCH
candidates in a sPDCCH region may be determined based on the number
of sPDCCH regions configured or determined in a sTTI time window.
The terms sPDCCH region and sPDCCH search space may be used
interchangeably.
[0175] In a sTTI time window, at least one cell-specific sPDCCH
region and at least one WTRU-specific sPDCCH region may be used,
configured, and/or determined. A cell-specific sPDCCH region and a
WTRU-specific sPDCCH region may be located in non-overlapped
time/frequency resources. A cell-specific sPDCCH region may be
located in a first sPDCCH region within a sTTI time window. A
WTRU-specific region may be located in one or more sPDCCH regions
that may not be used as cell-specific sPDCCH regions. A
WTRU-specific sPDCCH region may be a subset of a cell-specific
sPDCCH region. For example, a cell-specific sPDCCH region may be
configured for each sTTI and WTRU-specific sPDCCH regions may be
determined or configured in a subset of sTTIs within a sTTI time
window.
[0176] A WTRU may determine a number of sPDCCH regions within a
sTTI time window. The number of sPDCCH regions within a sTTI time
window may be determined in a WTRU-specific manner. The number of
sPDCCH candidates in a sPDCCH region may be determined based on the
TTI length of the sPDCCH region and/or the sTTI length of an
associated sPDSCH.
[0177] A WTRU may determine a number of sPDCCH candidates in a
sPDCCH region. A WTRU may monitor one or more sPDCCH candidates,
e.g., the determined number of sPDCCH candidates, in a sPDCCH
region. The number of sPDCCH candidates in a sPDCCH region may be
determined based on the number of sPDSCHs (or sTTIs) associated
with the sPDCCH region. For example, a first number of sPDCCH
candidates may be monitored in a sPDCCH region if one sTTI or one
sPDSCH is associated with the sPDCCH region. A second number of
sPDCCH candidates may be monitored in a sPDCCH region if multiple
sTTIs or multiple sPDSCHs are associated with the sPDCCH region.
The second number of sPDCCH candidates may be larger than the first
number of sPDCCH candidates. If m1 sPDCCH candidates are monitored
in a sPDCCH region when the sPDCCH region is associated with a
sPDSCH region (or one sTTI), m2 sPDCCH candidates may be monitored
in a sPDCCH region when the sPDCCH region is associated with
multiple sPDSCH regions (e.g., sTTIs). The value m2 may be an
integer multiple of m1 (e.g., m2=m1.times.K), where K may be the
number of sPDSCH regions associated with the sPDCCH region.
[0178] In another embodiment, the sPDCCH search space may be
defined, configured, or determined per sTTI. A predefined or
configured number of sPDCCH candidates may be monitored in each
sPDCCH region. One or more of following parameters may apply.
[0179] A WTRU may skip monitoring sPDCCH candidates in a sTTI (or a
sPDCCH region) if one or more of following conditions are
satisfied. A sPDSCH may be scheduled in the sTTI or in the sTTI
window, for example by scheduling in a previous sPDCCH (e.g., a
sPDCCH in a previous sTTI). The sTTI may not be associated with the
WTRU (or WTRU-ID). The association may be predetermined,
configured, or dynamically indicated. The sTTI may not be used for
one or more physical channels such as sPDCCH and/or sPDSCH. In the
sTTI, available resources for sTTI may be less than a threshold
that may be defined (e.g., predefined) or configured. A WTRU may
monitor sPDCCH in a subset of sTTIs that may be used for a sPDCCH
search sp ace.
[0180] In an example, a nPDCCH search space and one or more
potential sPDCCH search spaces may be located in a sTTI time window
(e.g., subframe). The number of nPDCCH candidates that may be
monitored by a WTRU may be determined, for example by the WTRU,
based on the number of sPDCCH search spaces configured or present
in a sTTI time window.
[0181] For example, one or more potential sPDCCH search spaces may
or may not be present in a sTTI time window. The presence of one or
more sPDCCH search spaces may be indicated from an indicator
described herein (e.g., sTTI resource indicator, config-DCI, etc.).
The number of nPDCCH candidates may be determined, for example by a
WTRU, based on the number of sPDCCH search spaces in a sTTI time
window.
[0182] It should be noted that the term "sPDCCH search space" may
be used interchangeably with the terms "sTTI resource," "sPDCCH
resource," and "sTTI." If no sPDCCH search space is present in a
sTTI time window, the number of nPDCCH candidates may be the same
as the number of legacy PDCCH candidates. A smaller number of
nPDCCH candidates may be monitored by a WTRU if a larger number of
sPDCCH search spaces are located or used in a sTTI time window. If
the number of sPDCCH search spaces is larger than a threshold that
may be predefined or configured, a WTRU may not monitor nPDCCH
candidates in a WTRU-specific search sp ace.
[0183] In another embodiment, a nPDCCH search space and one or more
potential sPDCCH search spaces may be located in a sTTI time window
(e.g., subframe). The monitoring of the nPDCCH search space may be
determined, foe example by aWTRU, based on nPDCCH type and the
presence of one or more sPDCCH search spaces.
[0184] If at least one sPDCCH search space is present, the search
space of a first nPDCCH type may not be monitored, for example by a
WTRU, while the search space of a second nPDCCH type may be
monitored, for example by the WTRU. For example, a first nPDCCH
type may be EPDCCH and a second nPDCCH type may be PDCCH. If a
sPDCCH search space is present, nPDCCH candidates of a first nPDCCH
type may be switched to nPDCCH candidates of a second nPDCCH
type.
[0185] A WTRU may be configured with a first nPDCCH type for a
WTRU-specific search space. The WTRU-specific search space may be
based on the first nPDCCH type (e.g., EPDCCH) if the WTRU does not
need to monitor any sPDCCH search spaces in a subframe. The
WTRU-specific search space may be based on a second nPDCCH type
(e.g., PDCCH) if the WTRU needs to monitor one or more sPDCCH
search spaces in a subframe.
[0186] The following description may include sPDCCH and nPDCCH
joint operation. In an embodiment, joint sPDCCH and normal PDCCH
(nPDCCH) search spaces may be used. A normal PDCCH (e.g., legacy
PDCCH, nPDCCH) search space and sPDCCH search space may be
configured (e.g., jointly configured) within a sTTI time window.
For example, at least one normal PDCCH (nPDCCH) search space (or
nPDCCH region) may be located in a sTTI time window. A DCI (e.g., a
specific DCI), referred to herein as nTTI, may be transmitted in at
least one nPDCCH search space.
[0187] The nPDCCH may include one or more nPDCCH candidates, which
may carry one or more nDCI that may be used for nTTI operation. The
nPDCCH may be at least one of PDCCH, enhanced PDCCH (EPDCCH), MTC
PDCCH (M-PDCCH), and narrowband PDCCH (NB-PDCCH). A nDCI may
include information related to sPDCCH search space configuration. A
number of sPDCCH candidates may be indicated in nDCI. A subset of
sPDCCH regions in a sTTI time window may be indicated in nDCI and a
WTRU may monitor sPDCCH candidates within the subset of sPDCCH
regions. A number of sCCEs in a sPDCCH region may be indicated in
nDCI. A sTTI resource configuration including at least one of time
resource configuration, frequency resource configuration, spatial
resource configuration, and sTTI length may be indicated in a nDCI.
A sDCI that may not be transmitted in an associated sPDCCH region,
for example due to collision with other signals or limited
resources, may be indicated in a nDCI.
[0188] In an embodiment, a nDCI may be used to configure a mode of
operation. For example, two operation modes may be used (e.g.,
normal TTI mode and short-TTI mode) and the nDCI may configure,
indicate, or (de)activate an associated operation mode. A WTRU may
monitor a nDCI in a nPDCCH region. The WTRU may determine the
operation mode based on the information in the nDCI. A WTRU may
monitor PDCCH candidates in one or more PDCCH regions based on the
determined operation mode. If a WTRU determines a first operation
mode (e.g., normal TTI), the WTRU may monitor nPDCCH candidates in
one or more nPDCCH regions. If a WTRU determines a second operation
mode (e.g., short TTI), the WTRU may monitor sPDCCH candidates in
one or more sPDCCH regions.
[0189] A nDCI may be transmitted in at least one, and as many as
every, sTTI time window. The sTTI time window may be a time window
for an operation mode. A nDCI may be transmitted in a subset of
subframes and/or SFNs. A nDCI may be transmitted in a common search
space in a nPDCCH region which may be monitored (e.g., commonly) by
WTRUs configured for sTTI operation.
[0190] In another embodiment, a nDCI may be used as a fallback DCI
between at least two operation modes. For example, a WTRU may
monitor a nPDCCH region to receive a nDCI when the WTRU is
configured with a certain operation or transmission mode (e.g.,
sTTI operation mode or sTTI transmission mode).
[0191] In an embodiment, a WTRU may be dynamically indicated to
monitor, attempt to decode, or receive one or more sPDCCH search
spaces in a sTTI time window (e.g., a subframe). The WTRU may
determine a set (or subset) of nPDCCH candidates in the nPDCCH
search space based on the indication.
[0192] In the case that a WTRU receives an indication of the
presence of one or more sPDCCH search spaces in a sTTI time window,
the WTRU may skip monitoring the nPDCCH search space in the sTTI
time window. If the WTRU receives an indication of the absence of a
sPDCCH search space in a sTTI time window, the WTRU may monitor the
nPDCCH search space.
[0193] If the WTRU receives an indication of the presence of one or
more sPDCCH search spaces, the WTRU may only monitor the nPDCCH
common search space and may skip monitoring the nPDCCH UE-specific
search space. The indication of the presence of one or more sPDCCH
search spaces may be received in a DCI which may be monitored,
received, or signaled in the nPDCCH common search space or may be
received in one or more CCEs in a predetermined nPDCCH region.
[0194] In the case that a WTRU receives an indication of the
presence of one or more sPDCCH search spaces in a sTTI time window,
the WTRU may monitor, attempt to decode, or receive a subset of
nPDCCH candidates in the associated nPDCCH search space in the sTTI
time window. The WTRU may also monitor, attempt to decode, or
receive a full set of nPDCCH candidates in the associated nPDCCH
search space in the sTTI time window if the WTRU receives an
indication of the absence of one or more sPDCCH search spaces in
the sTTI time window.
[0195] The full set of nPDCCH candidates may be the same as the
nPDCCH candidates the WTRU may need to monitor in a nPDCCH
WTRU-specific search if the WTRU is not configured with sPDCCH
monitoring or a sTTI operation mode. The subset of nPDCCH
candidates may be determined based on at least one of following
parameters: the presence of one or more sPDCCH search spaces; the
number of sPDCCH search spaces in a sTTI time window, wherein a
sPDCCH search space may be defined, determined, or configured as
the sPDCCH search space associated with a sTTI; the number of
sPDCCH candidates for a sPDCCH search space; and/or the number of
total sPDCCH candidates for one or more sPDCCH search spaces
presented or indicated.
[0196] The presence of one or more sPDCCH search spaces in a sTTI
time window may be indicated in a nPDCCH region. The number of
sPDCCH search spaces may be explicitly indicated in a DCI, which
may be monitored in a nPDCCH region. The sTTI length associated
with one or more sPDCCH search spaces may be indicated, wherein the
number of sPDCCH search spaces may be determined as a function of
the indicated sTTI length.
[0197] The subset of nPDCCH candidates may be determined based on
the CCE aggregation levels. For example, a subset of CCE
aggregation levels may be monitored if the presence of one or more
sPDCCH search spaces is indicated.
[0198] In another embodiment, a set (or a subset) of nDCI types,
which may be monitored in a nPDCCH search space, may be determined
based on the presence of one or more sPDCCH search spaces in a sTTI
time window and/or sDCI types. The one or more sPDCCH search spaces
in a sTTI time window and/or sDCI types may be monitored in the
sPDCCH search spaces.
[0199] A WTRU may be indicated, configured, or determined to
monitor one or more sDCI types in one or more sPDCCH search spaces.
For example, a first sDCI type may be associated with sPDSCH
transmissions and a second sDCI type may be associated with sPUSCH
transmissions. If the WTRU is indicated, configured, or determined
to monitor the first sDCI type in one or more sPDCCH search spaces
in an sTTI time window, the WTRU may monitor a set (or a subset) of
nPDCCH candidates for a nDCI type associated with nPUSCH
transmissions, and may skip monitoring nPDCCH candidates for a nDCI
type associated with nPDSCH transmissions.
[0200] A WTRU may monitor either nDCI or sDCI for a similar
transmission direction (downlink or uplink). A WTRU may be
scheduled (or assume to be scheduled) with either sPDSCH or nPDSCH
in a sTTI time window. A WTRU may be scheduled (or assume to be
scheduled) with either sPUSCH or nPUSCH in a sTTI time window.
[0201] If a WTRU is indicated, configured, or determined to monitor
a sDCI associated with sPUSCH transmissions in a sTTI time window
(e.g., subframe n), the WTRU may skip monitoring a nDCI associated
with nPUSCH transmissions in the same sTTI time window (e.g.,
subframe n). The sPUSCH and nPUSCH transmissions in the same sTTI
time window may include full or partial overlapping of the sPUSCH
and nPUSCH transmissions.
[0202] In another example, a WTRU may receive an indication of
which subset of sPDCCH candidates to monitor. For example, one or
more subsets of sPDCCH candidates may be configured, defined,
predefined, determined, or predetermined and one of the subsets may
be indicated in a DCI.
[0203] A DL reference signal for sPDSCH and sPDCCH channels may be
needed. sPDSCH and/or sPDCCH transmission may be associated with
one or more reference signal types (e.g., CRS, DM-RS), antenna
ports, and/or precoding granularity. One or more reference signal
types may be used. The reference signal type may be determined
based on at least one of the following parameters. A parameter may
be a scrambling sequence used. For example, a parameter used for a
scrambling sequence initialization (e.g., physical cell-ID,
WTRU-ID, virtual cell-ID) may be used. A parameter may be reference
signal locations in time and frequency grid. A parameter may be
precoding granularity of the reference signal. Within a precoding
granularity, a WTRU may use the reference signal for channel
estimation for the same antenna port. A parameter may be
WTRU-specific or cell-specific configuration. A parameter may be
reference signal power. A parameter may be reference signal
overhead within a certain time/frequency resource. For example, RS
type-0 may have zero reference signal overhead (e.g., no reference
signal) for sPDSCH and/or sPDCCH transmission, RS type-1 may have
10% reference signal overhead, and RS type-2 may be 20% reference
signal overhead.
[0204] The reference signal type may be determined based on a
transmission mode configured for sPDSCH. The reference signal type
may be indicated in a downlink control information associated with
the sPDCCH or sPDSCH resource. The downlink control information for
sPDSCH resource may be sDCI which may be carried in a sPDCCH
region. The downlink control information for sPDCCH resource may be
nDCI which may be carried in nPDCCH region.
[0205] In an embodiment, the reference signal type associated with
sPDSCH and/or sPDCCH transmission may be determined based on at
least one of following parameters. A parameter may be a
transmission mode or scheme used. A parameter may be the time
location of sTTI, or sTTI number within a sTTI time window. A
parameter may be a modulation and coding scheme (MCS) used for the
associated channel. A parameter may be a number of sTTIs bundled
for sPDSCH transmission. For example, a RS type-1 may be used for a
sPDSCH transmission if a single sPDSCH is scheduled in a sTTI time
window while a RS type-2 may be used for a first sPDSCH and RS
type-0 may be used for the rest of sPDSCH when multiple sPDSCHs are
scheduled in a sTTI time window.
[0206] In another embodiment, the presence of a reference signal in
a sTTI for sPDSCH and/or sPDCCH may be determined based on the
location of sTTI or the sTTI number within a sTTI time window. For
example, if N.sub.sTTI is located within a sTTI time window and
each sTTI within the sTTI time window is numbered from 0 to
N.sub.sTTI-1, the reference signal may be present in (e.g., only
in) a subset of sTTI numbers (e.g., even-numbered sTTIs or
odd-numbered sTTIs).
[0207] A method for sPDCCH resource allocation is needed. In an
embodiment, sCCEs may be defined, configured, and/or used in sTTI
resources. The sCCEs may be used for sPDCCH and/or sPDSCH
transmission. For example, a subset of sCCEs may be used for sPDCCH
transmission and the rest of the sCCEs may be used for sPDSCH
transmission.
[0208] A sTTI resource may be defined, configured, or determined
based on a set of sCCEs. The number sCCEs in a sTTI resource may be
determined based on the time/frequency resource used for the sTTI.
A first subset of sCCEs in a sTTI resource may be defined or
determined as sPDCCH region and a second subset of sCCEs in the
sTTI resource may be defined or determined as sPDSCH region. A WTRU
may receive a sDCI in a sPDCCH region and the WTRU may receive an
associated sPDSCH in the sPDSCH region. The first subset of sCCEs
and the second subset of sCCEs may be mutually exclusive. The first
subset of sCCEs and the second subset of sCCEs may be fully or
partially overlapped.
[0209] A sPDCCH region may be determined based on the sPDCCH
candidate used for sDCI transmission. The number of sCCEs for a
sPDCCH region may be determined based on the number of sCCEs used
for a sPDCCH transmission and the rest of the sCCEs may be
considered as a sPDSCH region. The number of sCCEs used for a
sPDCCH transmission may be indicated from the associated sDCI for a
sPDSCH transmission.
[0210] A sPDCCH region may be determined based on the number of
sCCEs used for transmission of sDCIs. The sPDSCH region (or sPDSCH
resource allocation) may be indicated dynamically from the
associated sDCI. For example, a starting sCCE number and an end
sCCE number may be indicated. A sTTI resource configured for sPDCCH
may be used for sPDSCH transmission if one or more sCCEs are unused
for sPDCCH transmission.
[0211] In another embodiment, one or more sPDCCH candidates may be
used for sPDSCH transmission. For example, a sTTI resource may be
defined as a sPDCCH search space and one or more sPDCCH candidates
in a sPDCCH search space may be used for sPDSCH transmission. A
sPDCCH candidate number may be indicated for sPDSCH transmission.
Starting and end sPDCCH candidate numbers may be indicated from an
associated sDCI for a sPDSCH transmission.
[0212] A system information (SI) update in an sTTI operation may be
provided. A WTRU may monitor a nPDCCH common search space to
receive a DCI with P-RNTI for SI update. The DCI with P-RNTI may
include scheduling information of a PDSCH, which may include paging
message. The paging message may include at least one of the
following: the SI update, Earthquake Tsunami Warning System (ETWS),
Commercial Mobile Alert Service (CMAS), or Extended Access Barring
(EAB) parameters. Hereafter, the SI update, ETWS, CMAS, and/or EAB
may all be referred to as a "direct indication." The direct
indication may also include a valueTag and SI update per SI
message.
[0213] A WTRU may attempt to receive the direct indication from a
paging message when the WTRU monitors a nPDCCH search space in a
subframe. A WTRU may attempt to receive the direct indication from
a DCI in a sPDCCH search space if one or more sPDCCH search spaces
are present. A sPDCCH candidate for the DCI which may carry the
direct indication may be monitored in a known location (e.g., a
sPDCCH common search space). One or more sPDCCH candidates may be
monitored by a WTRU for the DCI which may carry the direct
indication. The DCI which may carry the direct indication may be
scrambled with a specific RNTI (e.g., direct-RNTI).
[0214] A WTRU may attempt to receive the direct indication from a
DCI in an nPDCCH search space if one or more sPDCCH search spaces
are present. A nPDCCH candidate for the DCI which may carry the
direct indication may be monitored in a known location (e.g., a
nPDCCH common search space). One or more nPDCCH candidates may be
monitored by a WTRU for the DCI which may carry the direct
indication. The DCI which may carry the direct indication may be
scrambled with a specific RNTI (e.g., direct-RNTI).
[0215] In another embodiment, a WTRU may skip monitoring one or
more sPDCCH candidates in a subframe if the UE may need to monitor
a DCI with P-RNTI. For example, if a UE may need to monitor paging
message in an nPDCCH common search space, the UE may skip
monitoring one or more sPDCCH candidates in the subframe.
[0216] RE muting of sTTI resources may be performed. In an example,
one or more REs in a sTTI resource (e.g., sPDCCH, sPDSCH) may be
muted if the REs are used, configured, and/or occupied for one or
more reference signals. The reference signals may include but are
not limited to, at least one of: a periodic CSI-RS, an aperiodic
CSI-RS, a demodulation RS (DM-RS), a cell-specific RS (CRS), and a
positioning RS (PRS). One or more of the following parameters may
apply.
[0217] The presence of a reference signal in a sTTI resource may be
determined based on a higher layer configuration. Therefore, the
presence of a reference signal (e.g., periodic CSI-RS, CRS, or PRS)
may be known to the WTRU for a sTTI time window.
[0218] The presence of a reference signal and/or reference signal
configurations in a sTTI resource may be dynamically indicated in a
DCI. The DCI may be received, monitored, decoded, and/or
transmitted in one or more following resources and according to one
or more of the following parameters. The DCI may include
configuration information of the reference signal presented. For
example, one or more CSI-RS reuse patterns may be indicated in the
DCI, wherein the REs to be used for the indicated one or more
CSI-RS reuse patterns may be muted.
[0219] The DCI may be monitored in a nPDCCH region. The indication
may be transmitted in a DCI that may be used to indicate the
presence of one or more sTTI resources or one or more sPDCCH search
spaces. The indication may be transmitted in a sDCI associated with
one or more sPDSCH transmissions if a reference signal is presented
within the associated one or more sPDSCH transmissions. The
reference signal configurations may include at least one of the
following: one or more CSI-RS reuse patterns; CSI-RS transmission
power of the indicated one or more CSI-RS reuse patterns; a set of
frequency resources in which a reference signal is presented; and a
number of contiguous subframes in which the reference signal is
presented.
[0220] The RE muting may be referred to as RE puncturing or RE
rate-matching. The use of RE puncturing or RE rate-matching may be
dynamically indicated for a certain reference signal. For example,
RE rate-matching may be used for periodic CSI-RS, while RE muting
(RE puncturing or RE rate-matching) may be indicated in a DCI for
aperiodic CSI-RS. The DCI for RE muting type indication may be
monitored in a common search space (e.g., nPDCCH common search
space).
[0221] In some cases, the number of available REs within a sTTI
resource (e.g., sPDCCH resource and/or sPDSCH resource) may be used
to determine whether a WTRU monitors the sPDCCH search space. For
example, the WTRU may calculate, determine, estimate, or count the
number of available REs within a sTTI resource. If the number of
available REs within the sTTI resource is lower than a threshold,
the WTRU may skip monitoring the corresponding sPDCCH.
[0222] One or more of following may be considered as unavailable
REs: a reference signal (e.g., periodic CSI-RS, aperiodic CSI-RS,
IMR, CRS, DM-RS, PRS, and discovery RS), a physical broadcasting
channel (PBCH), a synchronization signal (e.g., PSS or SSS), and
the nPDCCH.
[0223] The threshold may be determined as a function of sTTI
length. For example, a first threshold number (e.g., N1) may be
used if a first sTTI length (e.g., 2 symbols) is used and a second
threshold number (e.g., N2) may be used if a second sTTI length
(e.g., 7 symbols) is used. One or more threshold numbers may be
predefined, configured, or dynamically indicated. The associated
threshold number may be dynamically indicated in a DCI used to
indicate the presence of a sTTI resource in a sTTI time window. The
DCI may be monitored in a nPDCCH region (e.g., a nPDCCH common
search space or a known location within nPDCCH region).
[0224] The threshold numbers may be determined as a function of the
number of frequency resource used for a sTTI resource. The periodic
CSI-RS, which may be configured via higher layer signaling, may be
considered to be unavailable REs, while the aperiodic CSI-RS, which
may be indicated in a DCI, may be considered as to be available
REs.
[0225] In another embodiment, the number of sTTI resources for a
downlink transmission (e.g., sPDSCH and/or sPDCCH) may be
determined based on the number of available REs in a sTTI resource.
For example, if the number of available REs for a sTTI resource is
lower than a threshold, the sTTI resource may be used together (or
bundled) with one or more consecutive sTTI resources within a sTTI
time window.
[0226] If the number of available REs for a sTTI resource within a
sTTI time window (e.g., resource # n) is lower than a threshold,
the number of available REs may be counted by combining a next sTTI
resource (e.g., sTTI resource # n+1). If the number of available
REs for combined (or bundled) sTTI resources is higher than a
threshold, the WTRU may monitor a sPDCCH search space in the
combined (or bundled) sTTI resources. The timing of HARQ-ACK and
sPUSCH transmission may be based on the latest sTTI resource within
the bundled sTTI resources. The effective sTTI length may be
increased to K times if K sTTI resources are combined or
bundled.
[0227] The number of sPDCCH candidates in each sPDCCH region for
blind decoding may be determined based on the number of sTTI
resources in a subframe. A smaller number of sPDCCH candidates may
be monitored if the number of sTTI resources in a subframe gets
larger. A common search space definition for legacy PDCCH and
sPDCCH may be used for dynamic configuration between normal TTI and
short TTI. A fallback DCI may be monitored in the common search
space.
[0228] A set of sCCEs may be used in a sTTI resource, where sPDCCH
and sPDSCH may be transmitted in mutually exclusive subsets of
sCCEs. A first subset of sCCEs may be determined as sPDCCH carrying
a DCI for sPDSCH scheduling in a sTTI resource. The remaining sCCEs
may be used to transmit sPDSCH.
[0229] 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, terminal, base station, RNC, or any host
computer.
* * * * *