U.S. patent application number 15/193693 was filed with the patent office on 2016-10-20 for method and apparatus for radio resources management in multi-radio access technology wireless systems.
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 Diana Pani, Ghyslain Pelletier.
Application Number | 20160309394 15/193693 |
Document ID | / |
Family ID | 46634537 |
Filed Date | 2016-10-20 |
United States Patent
Application |
20160309394 |
Kind Code |
A1 |
Pelletier; Ghyslain ; et
al. |
October 20, 2016 |
METHOD AND APPARATUS FOR RADIO RESOURCES MANAGEMENT IN MULTI-RADIO
ACCESS TECHNOLOGY WIRELESS SYSTEMS
Abstract
Methods and apparatus for performing wireless communication in a
wireless transmit/receive unit (WTRU) configured for multi-radio
access technology (RAT) operation are disclosed. A method includes
the WTRU wirelessly communicating information on a first operating
frequency according to a first RAT. The WTRU also wirelessly
communicates information on a second operating frequency according
to a second RAT.
Inventors: |
Pelletier; Ghyslain;
(Montreal, CA) ; Pani; Diana; (Montreal,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
INTERDIGITAL PATENT HOLDINGS, INC. |
Wilmington |
DE |
US |
|
|
Assignee: |
INTERDIGITAL PATENT HOLDINGS,
INC.
Wilmington
DE
|
Family ID: |
46634537 |
Appl. No.: |
15/193693 |
Filed: |
June 27, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14673000 |
Mar 30, 2015 |
9380628 |
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15193693 |
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13557853 |
Jul 25, 2012 |
8995370 |
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14673000 |
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61513180 |
Jul 29, 2011 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W 76/15 20180201;
H04W 76/16 20180201; H04W 76/20 20180201; H04W 88/06 20130101; H04W
40/248 20130101; H04W 76/19 20180201; H04W 72/0453 20130101; H04W
84/042 20130101 |
International
Class: |
H04W 40/24 20060101
H04W040/24; H04W 76/02 20060101 H04W076/02 |
Claims
1. A wireless transmit/receive unit (WTRU) comprising: a
transceiver operatively coupled to a processor configured to detect
a radio link failure (RLF) of a serving cell of a first radio
access technology (RAT); the transceiver operatively coupled to the
processor, in response to detecting the RLF of the serving cell of
the first RAT, configured to stop uplink (UL) transmissions for all
serving cells of the first RAT; and the transceiver operatively
coupled to the processor configured to send an indication of the
RLF of the serving cell of the first RAT to an evolved Node B (eNB)
connected via a second RAT.
2. The WTRU of claim 1, wherein the first RAT and the second RAT
are different air interface technologies.
3. The WTRU of claim 1, wherein the first RAT and the second RAT
are a same air interface technology.
4. The WTRU of claim 1, wherein the WTRU is connected to a primary
serving cell via the second RAT.
5. The WTRU of claim 1, wherein the WTRU is connected to a primary
serving cell via the first RAT and a different primary serving cell
via the second RAT.
6. A method performed by a wireless transmit/receive unit (WTRU),
the method comprising: detecting a radio link failure (RLF) of a
serving cell of a first radio access technology (RAT); in response
to detecting the RLF of the serving cell of the first RAT, stopping
uplink (UL) transmissions for all serving cells of the first RAT;
and sending an indication of the RLF of the serving cell of the
first RAT to an evolved Node B (eNB) connected via a second
RAT.
7. The method of claim 6, wherein the first RAT and the second RAT
are different air interface technologies.
8. The method of claim 6, wherein the first RAT and the second RAT
are a same air interface technology.
9. The method of claim 6, wherein the WTRU is connected to a
primary serving cell via the second RAT.
10. The method of claim 6, wherein the WTRU is connected to a
primary serving cell via the first RAT and a different primary
serving cell via the second RAT.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 14/673,000 filed Mar. 30, 2015, and issued as
U.S. Pat. No. 9,380,628 on Jun. 28, 2016, which is a continuation
of U.S. patent application Ser. No. 13/557,853 filed Jul. 25, 2012,
and issued as U.S. Pat. No. 8,995,370, on Mar. 31, 2015, which
claims the benefit of U.S. Provisional Application No. 61/513,180,
which was filed on Jul. 29, 2011, all of which are hereby
incorporated by reference herein.
BACKGROUND
[0002] Demand for improved network coverage, improved capacity and
increasing bandwidth for voice and data services in wireless
systems has led to continuous development of a number of radio
access technologies (RATs). Examples of such RATs include, for
example, Global Systems Mobile (GSM), Wideband Channel Division
Multiple Access (WCDMA), High-Speed Packet Access (HSPA) (which may
include High-Speed Downlink Packet Access (HSDPA) and High-Speed
Uplink Packet Access (HSUPA) with their respective multicarrier
counterparts), Long Term Evolution (LTE) (which may include support
for carrier aggregation in LTE Release 10 and beyond) in the Third
Generation Partnership Project (3GPP), IEEE 802.11b/a/g/n, IEEE
802.16a/e, IEEE 802.20, Code Division Multiple Access 2000 1.times.
(CDMA2000 1.times.) and cdma2000 Evolution-Data Optimized (cdma200
EV-DO) in the Third Generation Partnership Project 2 (3GPP2).
SUMMARY
[0003] Methods and apparatus for performing wireless communication
in a wireless transmit/receive unit (WTRU) configured for multi-RAT
operation are disclosed. A method includes the WTRU wirelessly
communicating information on a first operating frequency according
to a first RAT and wirelessly communicating information on a second
operating frequency according to a second RAT.
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 block diagram of an example system for multi-RAT
communication;
[0009] FIG. 3 is a block diagram of an example control plane for
multi-RAT operation using a single RRC instance and a single RRC
connection per WTRU;
[0010] FIG. 4 is a flow diagram of an example method of performing
wireless communication in a WTRU configured for multi-RAT operation
corresponding to the embodiment illustrated in FIG. 3;
[0011] FIG. 5 is a block diagram of an example control plane for
multi-RAT operation using an RRC instance for each configured RAT
and a single RRC connection per WTRU;
[0012] FIG. 6 is a flow diagram of an example method of performing
wireless communication in a WTRU configured for multi-RAT operation
corresponding to the embodiment illustrated in FIG. 5;
[0013] FIG. 7 is a block diagram of an example control plane for
multi-RAT operation using an RRC instance and an RRC connection for
each configured RAT;
[0014] FIG. 8 is a flow diagram of an example method of performing
wireless communication in a WTRU configured for multi-RAT operation
corresponding to the embodiment illustrated in FIG. 7; and
[0015] FIG. 9 is a block diagram illustrating the E-UTRA RRC states
and mobility support between E-UTRAN, UTRAN and GERAN.
DETAILED DESCRIPTION
[0016] 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.
[0017] 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.
[0018] 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 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.
[0019] 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.
[0020] 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).
[0021] 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).
[0022] 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).
[0023] 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.
[0024] 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.
[0025] 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.
[0026] 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.
[0027] 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.
[0028] 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.
[0029] 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.
[0030] 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.
[0031] 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.
[0032] 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.
[0033] 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).
[0034] 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.
[0035] 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.
[0036] 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.
[0037] 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.
[0038] 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.
[0039] 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.
[0040] The core network 106 shown in FIG. 1C may include a mobility
management 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.
[0041] The MME 142 may be connected to each of the eNode-Bs 142a,
142b, 142c 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.
[0042] 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.
[0043] 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.
[0044] 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.
[0045] As RATs such as WCDMA and LTE have developed, they have been
made to enable use of more than one component carrier (CC) for
transmissions and receptions between a WTRU and a base station. A
CC may be, for example, a frequency on which a WTRU operates. For
example, a WTRU may receive transmissions on a downlink (DL) CC,
which may comprise a plurality of DL physical channels. For another
example, a WTRU may perform transmissions on an uplink (UL) CC,
which may comprise a plurality of UL physical channels.
[0046] A cell typically minimally includes a DL CC which may be
linked to a UL CC based on the SI received by the WTU that is
either broadcast on the DL CC or using dedicated configuration
signaling from the network. For example, when the SI is broadcast
on the DL CC, the WTRU may receive the UL frequency and bandwidth
of the linked UL CC as part of the SI IE (e.g., when in RRC_IDLE
for LTE or when in idle/CELL_FACH for WCDMA (i.e., when the WTRU
does not yet have an RRC connection to the network).
[0047] More specifically, 3GPP WCDMA Release 8 provided support for
simultaneous use of two HSDPA component carriers (2C-HSDPA),
Release 9 provided support for MIMO in multicarrier DL WCDMA and
also introduced support for two HSUPA UL CCs, and Release 10
introduced support for up to four DL CCs (4C-HSDPA). For Release
11, the number of DL CCs may be increased to eight (8C-HSDPA). 3GPP
LTE Release 10 introduced support for simulaneous transmission
and/or reception using the radio resources of a plurality of CCs
between a base station and a mobile terminal within the same
transmission interval. The transmission time interval (TTI) for
HSPA is a 2 ms subframe, and the TTI for 3GPP LTE Releases 8, 9 and
10 is a 1 ms subframe (each radio frame (10 ms) includes 10 equally
sized sub-frames of 1 ms).
[0048] Network architectures for different Rats may support
different network functionalities at different entities within the
architecture. For some RATs, similar functionalities (e.g., MAC
functionalities) may be performed by different entities within the
same architecture, and architectures for different RATs may include
different entities. For example, for UTRAN, the radio resource
control (RRC), packet data control protocol (PDCP), radio link
control (RLC), medium access control dedicated (MAC-d) and MAC-is
sub-layers are located in the radio network controller (RNC), while
medium access control high speed (MAC-hs), MAC-i and layer 1 (L1)
are located in the Node B. Further, for universal terrestrial radio
access network (UTRAN), security (e.g. ciphering), segmentation and
reassembly services to MAC, as well as in-order delivery services
to PDCP, are provided by the RLC, while MAC ensures ordering
between the hybrid automatic repeat request (HARQ) processes for
the RLC layer. For evolved UTRAN (eUTRAN), for another example,
there is no RNC, and the RRC, PDCP, RLC and MAC layers are all
located in the eNodeB (eNB). Security (e.g., ciphering, integrity
and authentication) and in-order delivery services (e.g., at
handover) are provided by the PDCP, while the RLC provides
segmentation, re-segmentation and reassembly services to MAC.
[0049] One of the design objectives for LTE release 8 was to allow
operators to deploy LTE using the same sites as for legacy WCDMA
deployments to reduce deployment and radio planning costs.
Accordingly, network operators may deploy both WCDMA/HSPA and LTE
in the same coverage areas, LTE deployments may have similar
coverage as existing WCDMA/HSPA deployments and multi-mode WTRUs
supporting both WCDMA/HSPA and LTE accesses may be widely
deployed.
[0050] However, spectrum is a costly resource, and not all
frequency bands may be available to all operators. Thus, while it
is expected that operators may offer support for both HSPA and LTE
services, carrier aggregation scenarios may be limited to at most
2-3 component carriers per RAT for a given operator. In addition,
legacy deployments may be maintained for the foreseeable future
while LTE is being deployed, which may lead to a situation where
operators see periods of underutilization of radio
resources/spectrum and capacity in one of their RATs.
[0051] HSPA Release 10 with MIMO offers downlink peak data rates of
42 Mbps, and Release 10 multicarrier HSPA may further increase the
peak rate by introducing support for up to four DL CCs. LTE
Releases 8 and 9 offer up to 100 Mbps in the single CC DL, and LTE
Release 10 with intra-RAT carrier aggregation may further increase
the peak rate by combining transmission resources of up to 5 CCs.
Some motivations for taking advantage of the combined data
rates/capacity of the multi-RAT deployment may include, for
example, reducing the cost of offering higher data rates (data
enhancement scenario), migrating from WCDMA/HSPA to LTE with
limited spectrum available (migration scenario), maximizing usage
of deployed RATs (e.g., through load balancing), and maximizing
usage of radio components in the WTRU (e.g., dual-band
receiver).
[0052] In addition to capitalizing on increased peak rates, an
operator may want to reserve a frequency band for other reasons
(e.g., for home eNB deployment). Further, combining HSPA resources
with LTE resources may additionally provide means for ensuring
service continuity (e.g., either for circuit switched (CS) Voice
and/or for services requiring LTE data rates). Accordingly, it may
be desirable to have methods allowing a WTRU to operate
simultaneously on multiple frequencies, where the WTRU operates on
at least one of the frequencies according to a different RAT.
[0053] Embodiments described herein may relate to multi-mode WTRUs
supporting simultaneous (or near-simultaneous) operation on CCs of
a plurality of different RATs. Embodiments described herein may
also relate to how multi-mode WTRUs may perform radio resource
management and related RRC procedures when using different RATs. In
an embodiment, the WTRUs may perform radio resource management and
related RRC procedures using different RATs on different
frequencies.
[0054] Some embodiments described herein are described with respect
to the first RAT being LTE and the second RAT being WCDMA, HSUPA
and/or HSDPA, and vice versa. However, the embodiments described
herein may be applicable to any wireless technology. Further, while
not explicitly described herein, embodiments described herein may
be applicable to WTRUs that transmit using different RATs only in
different time intervals (i.e., some form of time division
operation on a TTI basis) on different frequencies and/or where
such transmissions are performed in the same frequency band.
[0055] FIG. 2 is a block diagram of an example system 200 for
multi-RAT communication. The illustrated system 200 includes a WTRU
204 and two base stations (e.g., eNBs) 202 and 206. In FIG. 2, one
WTRU 204 is in communication with two base stations 202 and 206
using channels 208, 210, 212 and 214. The channels 208, 210, 212
and 214 may be any combination of UL and DL channels of any number
of different RATs.
[0056] A multi-RAT operation may include any multi-mode WTRU
simultaneously configured for operation with at least one CC of a
first RAT (e.g., a DL CC, a UL CC, or one or more serving cell(s))
and with at least one CC of a second RAT (e.g., a DL CC, a UL CC,
or one or more serving cell(s)). The operation on the different CCs
may occur either simultaneously, or near-simultaneously in time.
Operation according to different RATs may also be used
sequentially, for example, on the same CC. A multi-mode WTRU may
include any mobile terminal supporting a plurality of RATs, such
as, for example, any combination of GSM, WCDMA, HSPA, HSDPA, HSUPA,
LTE, IEEE 802.11b/a/g/n, IEEE 802.16a/e, IEEE 802.20, cdma2000
1.times. and cdma2000 EV-DO.
[0057] A serving cell may include, for example, a primary cell
(PCell) or a secondary cell (SCell). More specifically, for a WTRU
that is not configured with any SCell or that does not support
operation on multiple CCs (carrier aggregation), there may be only
one serving cell (the PCell). For a WTRU that is configured with at
least one SCell, the serving cells may include a set of one or more
cells comprising all configured PCell(s) and all configured
SCell(s).
[0058] In an embodiment, the WTRU 204 may wirelessly communicate
information on a first operating frequency according to a first RAT
and may wirelessly communicate information on a second operating
frequency according to a second RAT. The communications on the
first and second operating frequencies may occur over any
combination of the channels 208, 210, 212 and 214. For example, the
WTRU 204 may wirelessly communicate information on a first
operating frequency according to a first RAT (e.g., LTE) over a DL
channel 208 (e.g., LTE DL) and may wirelessly communicate
information on a second operating frequency according to a second
RAT (e.g., WCDMA) over a DL channel 212 (e.g., WCDMA HSDPA). For
another example, the WTRU 204 may wireless communicate information
on a first operating frequency according to a first RAT (e.g.,
WCDMA) over a UL channel 212 (e.g., WCDMA HSUPA) and may wirelessly
communicate information on a second operating frequency according
to a second RAT (e.g., LTE) over a UL channel 214 (e.g., LTE
UL).
[0059] A WTRU, such as the WTRU 204 illustrated in FIG. 2, may be
configured for multi-RAT operation. A WTRU that supports access to
a plurality of RATs may access those resources using one of a
number of different control plane arrangements and any one of a
number of different methods such as, for example, the control
planes and methods illustrated and described below with respect to
FIGS. 3-8.
[0060] FIG. 3 is a block diagram of an example control plane 300
for multi-RAT operation using a single RRC instance 302, a single
state machine 304, a single RRC connection 306 per WTRU, and one or
more SRBs 308. When referred to hereafter, the term RRC instance
may conceptually represent, without limiting to possible additional
aspects or a subset of the following aspects, the use of an RRC
protocol that may comprise a single state machine operating using a
plurality of RRC states (e.g., CONNECTED or IDLE for the LTE RRC
protocol) with corresponding state transitions, RRC procedures
(including related timers) including RRC control and measurement
procedures, RRC PDUs and information elements (IEs), the RRC
configuration (including parameters for configuration of RRC, PDCP,
RLC, MAC), and the physical (PHY) layer. In the example illustrated
in FIG. 3, the single RRC instance 302 may handle the management of
radio resources for all configured RATs.
[0061] For HSPA, there are at least four RRC states: CELL_DCH,
CELL_FACH, CELL_PCH/URA_PCH and UTRA_IDLE. For LTE, there are at
least two RRC states: RRC_CONNECTED and RRC_IDLE. The WTRU is in
RRC_CONNECTED when an RRC Connection has been established.
Otherwise, the WTRU is in RRC_IDLE.
[0062] In the RRC_IDLE state, the WTRU at least monitors the paging
channel to detect incoming calls, change of SI, and, in an
embodiment, early terrestrial warning system (ETWS)/commercial
mobile alert system (CMAS) notifications, and performs neighboring
cell measurements, cell selection, cell reselection, and SI
acquisition. In the RRC_CONNECTED state, the WTRU may
transmit/receive on unicast channels and at least monitor the
paging channel and/or SI Block Type 1 to detect incoming calls,
change of SI, and, in an embodiment, ETWS/CMAS notifications. The
WTRU may also be configured with one or most secondary cells in
addition to the primary cell.
[0063] For each of the RRC protocols described in the above
paragraph, a set of states, transitions, messages (e.g., protocol
data units (PDUs)) and procedures are defined. FIG. 9 is a block
diagram 900 illustrating the E-UTRA (e.g., LTE) RRC states
including, for example, the CELL_DCH state 902, the CELL_FACH state
904, the CELL_PCH and URA_PCH states 906, the UTRA_IDLE state 908,
the E-UTRA RRC CONNECTED state 910, the E-UTRA RRC_IDLE state 912,
the GSM_Connected state 914, the GPRS packet transfer mode 916 and
the GSM Idle/GPRS Packet Idle State 918. FIG. 9 also illustrates
mobility support between E-UTRAN, UTRAN and GERAN.
[0064] In an embodiment, the single RRC instance 302 may manage the
single RRC Connection 306, which may be used to handle radio
resources management for all configured serving cells of any RAT.
According to this embodiment, there may be at most one RRC instance
and one RRC connection per WTRU at any time.
[0065] FIG. 4 is a flow diagram 400 of an example method of
performing wireless communication in a WTRU configured for
multi-RAT operation corresponding to the embodiment illustrated in
FIG. 3. In the example illustrated in FIG. 4, a WTRU may first
access a network and establish the RRC connection 306 in a first
RAT (e.g., a primary RAT (PRAT)) using the RRC instance 302 (402).
The WTRU may subsequently receive a configuration that adds at
least one serving cell of a second RAT (e.g., a secondary RAT
(SRAT) over the RRC connection 306 (404). The WTRU may then
configure the radio resources using the single RRC instance 302
(406).
[0066] A primary cell (PCell) may include, for example, a cell
operation on a primary frequency in which the WTRU performs the
initial access to the system (e.g., the cell in which the WTRU
performs the initial connection establishment procedure, the cell
in which the WTRU initiates the connection re-establishment
procedure, or the cell indicated as the primary cell in the
handover procedure). The PCell may also correspond to a frequency
indicated as part of the RRC configuration procedure. Some
functions may be only supported on the PCell. For example, the UL
CC of the PCell may correspond to the CC whose physical UL control
channel resources are configured to carry all HARQ
acknowledgement/non-acknowledgement (ACK/NACK) feedback for a given
WTRU. For example, in LTE, the WTRU may use the PCell to derive the
parameters for the security functions and for upper layer SI such
as Non-Access Stratum (NAS) mobility information. Other functions
that may be supported only on the PCell DL may include SI
acquisition and change monitoring procedures on the broadcast
channel (BCCH) and paging. For example, the PCell of WCDMA may be
similar to the PCell of LTE. A secondary cell (SCell) may include,
for example, a cell operating on a secondary frequency, which may
be configured once an RRCconnection is established and may be used
to provide additional radio resources. SI relevant for operation in
the concerned SCell may be provided using dedicated signaling when
the SCell is added to the WTRU's configuration. Although the
parameters may have different values than those broadcast on the DL
of the concerned SCell using the SI signaling, this information may
be referred to as SI of the concerned SCell independently of the
method used by the WTRU to acquire this information.
[0067] A primary RAT (PRAT) (or anchor RAT) may include the radio
access network technology. At least one serving cell may be
configured as the PCell for the PRAT. The PCell may support at
least one of establishing a first RRC connection, deriving security
parameters (e.g., in case a single security context is used), using
UL resources to transmit UL control information (UCI) (e.g., if UCI
is transmitted only on a serving cell of a first RAT), and/or
configuring at least one serving cell with UL resources (e.g., if
UL resources are configured only in a first RAT). Consequently, in
some embodiments, the PRAT, or the anchor RAT, may also be referred
to as the first RAT. A secondary RAT (SRAT) (or non-anchor RAT) may
include the RAT for which none of the configured serving cell(s) is
for the PRAT of the WTRU's configuration.
[0068] In an embodiment, a WTRU may access an LTE cell and
establish an RRC connection 306 with LTE as the PRAT using the
corresponding RRC connection establishment procedure. The WTRU may
be configured using the RRC connection reconfiguration procedure of
the PRAT with additional serving cells, which may include one or
more HSPA serving cells as the SRAT. In an embodiment, the RRC
connection reconfiguration procedure may be performed only once the
security is activated in the PRAT. Further, in an embodiment, the
WTRU may receive an RRC message including one or more IEs
pertaining to the HSPA configuration (e.g., SI configuration IEs,
radio bearer IEs, transport channel IEs and physical channel IEs)
during the RRC reconfiguration procedure.
[0069] In another embodiment, a WTRU may access an HSPA cell and
establish an RRC connection 306 with HSPA as the PRAT using the
corresponding RRC connection establishment procedure. The WTRU may
be configured using the RRC connection reconfiguration procedure of
the PRAT with additional serving cells (e.g., one or more LTE
serving cells) as the SRAT. In an embodiment, the WTRU may be
configured using the RRC Radio bearer setup procedures of the PRAT
to configure the PRAT specific information and simultaneously
configured the WTRU with SRAT serving cells. Alternatively, the
WTRU may be configured with the SRAT in the RRC Connection Setup
using the signaling radio bearer (SRB) of the PRAT. In an
embodiment, the RRC connection reconfiguration procedure may be
performed only once the security is activated in the PRAT. Further,
in an embodiment, the WTRU may receive an RRC message including one
or more IEs pertaining to the LTE configuration (e.g., SI
configuration IEs and/or RRC IEs, which may include at least one of
a MAC-MainConfig IE, a CQI-ReportConfig IE, a PDSCH-Config IE, a
PhysicalConfigDedicated IE, a RadioResourceConfigDedicated IE,
and/or a RadioConfigCommon IE for the DL configuration of a serving
cell and/or at least one of a PUSCH-Config IE and/or a
SoundingRS-UL-Config IE for the UL configuration of the serving
cell) during the RRC reconfiguration procedure.
[0070] SRBs are radio bearers used only for the transmission of RRC
and NAS messages. SRB0 is used for RRC messages using the common
control channel (CCH) logical channel. SRB1 is for RRC messages
(e.g., with a piggybacked NAS message) and for NAS messages prior
to establishment of SRB2 using the dedicated control channel (DCCH)
logical channel. SRB2 is for NAS messages and is always configured
after activation of security. Once security is activated, all RRC
messages on SRB1 and SRB2 may be integrity protected and
ciphered.
[0071] When CCs (or serving cells) of different RATs are aggregated
and configured for a given WTRU, it may, thus, be necessary to have
methods to handle the management of radio resource connections. In
particular, if a plurality of RRC connections and/or state machines
(SMs) may be used for multi-RAT access (e.g., one per RAT on which
the WTRU operates), it may be desirable to define methods to ensure
proper handling of each RRC connection and possible interactions in
between. Alternatively, if a single RRC connection and/or state
machine may be used for multi-RAT access, it may be desirable to
define methods by which a single RRC state machine can control a
plurality of radio resources.
[0072] FIG. 5 is a block diagram of an example control plane 500
for multi-RAT operation using an RRC instance for each configured
RAT, a state machine for each RRC instance and a single RRC
connection per WTRU. More specifically, the illustrated example
includes an RRC instance 502 for a PRAT, a state machine 504 for
the PRAT, an RRC instance 508 for an SRAT, a state machine 506 for
the SRAT, a single RRC connection 510 and one or more SRB(s) 512.
In the example illustrated in FIG. 5, radio resources for a
plurality of RATs (e.g., the PRAT and the SRAT) may be managed
using a plurality of RRC instances (e.g., a single instance of the
control plane per configured RAT).
[0073] In an embodiment, the RRC instance 508 for the SRAT
comprises a subset of the RRC protocol for the concerned RAT. For
example, the RRC instance 508 for the SRAT may handle at least some
radio resource management functions for the corresponding RAT
(e.g., intra-frequency and inter-frequency measurement
configuration and reporting, radio link monitoring (RLM), SI
maintenance and error handling). In an embodiment, the RRC instance
508 for each SRAT may interact with the RRC instance 502 for the
PRAT. In the illustrated embodiment, the RRC instance 502 manages
the single RRC connection 510, which may be used to handle radio
resources management of at least one RAT. There is also an
additional RRC instance for each additional configured RAT (e.g.,
the RRC instance 508 for the SRAT), which may comprise a subset of
the RRC protocol for the concerned RAT (SRAT).
[0074] For an LTE serving cell, a WTRU may perform RLM and
determine UL radio link failure (RLF) when it reaches the maximum
number of preamble transmissions for the random access procedure
and/or repeated failure to perform the random access procedure on
the concerned serving cell. Further, for an LTE serving cell, a
WTRU may determine DL RLF when the RRC instance receives number
N310 consecutive out-of-synch indications from the physical (PHY)
layer and a timer T310 subsequently expires while the WTRU has not
recovered from the error condition that started the timer.
[0075] FIG. 6 is a flow diagram 600 of an example method of
performing wireless communication in a WTRU configured for
multi-RAT operation corresponding to the embodiment illustrated in
FIG. 5. In the example illustrated in FIG. 6, a WTRU may first
access a network and establish the RRC connection 510 in a first
RAT (e.g., PRAT) using a first RRC instance (RRC instance 502 for
the PRAT) (602). The WTRU may subsequently receive a configuration
that adds at least one serving cell of a second RAT (e.g., the
SRAT) over the RRC connection 510 (604). The WTRU may then use a
second RRC instance (RRC instance 508 for the SRAT), which may
configure the radio resources of the SRAT, using the RRC PDU(s)
(e.g., received over different SRBs) and/or configuration
information received over the RRC connection 510 (606). In an
embodiment, the second RRC instance 508 may initially operate
according to an RRC connected mode (e.g., LTE CONNECTED or HSPA
CELL_DCH). The states of the RRC instance for an SRAT may not be
active, or the RRC connected mode may be initiated by the PRAT.
[0076] For example, a WTRU may access an LTE cell and establish a
RRC connection with LTE as the PRAT using the corresponding RRC
connection establishment procedure. The WTRU may be configured with
additional serving cells, for example, including one or more HSPA
serving cells as the SRAT. In an embodiment, the configuration
procedure may be performed only once the security is activated in
the PRAT.
[0077] In an embodiment, the configuration may be received via the
RRC connection reconfiguration procedure of the PRAT. In an
embodiment, the WTRU may receive an RRC message including one or
more IEs pertaining to the HSPA configuration, which may include,
for example, at least one of SI configuration IEs, radio bearer
IEs, transport channel IEs, physical channel IEs, and secondary
serving HS-DSCH IEs during the RRC reconfiguration procedure. In an
embodiment, the RRC instance of the PRAT may forward the received
configuration information of the SRAT to the RRC instance of the
corresponding SRAT, which may configure the corresponding radio
resources of the SRAT.
[0078] In another embodiment, the configuration may be received
over an SRB configured such that it is associated with the RRC
instance 508 of the SRAT. In an embodiment, the WTRU may receive an
RRC PDU of the RRC protocol of the SRAT over the SRB. In an
embodiment, the RRC message may include one or more IEs pertaining
to the HSPA configuration, which may include, for example, at least
one of SI configuration IEs, radio bearer IEs, transport channel
IEs, and physical channel IEs. In an embodiment, the RRC instance
of the SRAT may perform the corresponding configuration procedures,
such as a radio bearer control procedure and a physical channel
configuration procedure.
[0079] For example, a WTRU may access an HSPA cell and establish an
RRC connection with HSPA as the PRAT using the corresponding RRC
connection establishment procedure. The WTRU may be configured with
additional serving cells, which may include, for example, one or
more LTE serving cells as the SRAT. In an embodiment, this
configuration procedure may be performed only once the security is
activated in the PRAT.
[0080] In an embodiment, the configuration may be received over the
RRC connection reconfiguration procedure of the PRAT. In an
embodiment, the WTRU may receive an RRC message including one or
more IEs pertaining to the LTE configuration, which may include,
for example, at least one of SI configuration IEs, RRC IEs (which
may include at least one of a MAC-MainConfig IE, CQI-ReportConfig
IE, PDSCH-Config IE, PhysicalConfigDedicated IE,
RadioResourceConfigDedicated IE, and RadioConfigCommon IE for the
DL configuration of a serving cell and may also include at least
one of a PUSCH-Config IE and SoundingRS-UL-Config IE for the UL
configuration of the serving cell). In an embodiment, the RRC
instance 502 of the PRAT may forward the received configuration
information of the SRAT to the RRC instance of the corresponding
SRAT, which may configure the corresponding radio resources of the
SRAT.
[0081] In another embodiment, the configuration may be received
over an SRB configured such that it is associated with the the RRC
instance 508 of the SRAT. In an embodiment, the WTRU may receive an
RRC PDU of the RRC protocol of the SRAT over the SRB. In an
embodiment, the RRC message may include one or more IEs pertaining
to the LTE configuration, which may include, for example, at least
one of SI configuration IEs, radio resource control IEs (e.g.,
including at least one of a MAC-MainConfig IE, CQI-ReportConfig IE,
PDSCH-Config IE, PhysicalConfigDedicated IE,
RadioResourceConfigDedicated IE, and a RadioConfigCommon IE for the
DL configuration of a serving cell and at least one of a
PUSCH-Config IE and a SoundingRS-UL-Config IE for the UL
configuration of the serving cell). In an embodiment, the RRC
instance of the SRAT may perform the corresponding RRC
reconfiguration procedure(s), such as a radio resource
configuration procedure.
[0082] FIG. 7 is a block diagram of an example control plane 700
for multi-RAT operation using an RRC instance for each configured
RAT, a state machine for each RRC instance, and an RRC connection
for each configured RAT. More specifically, the illustrated example
includes an RRC instance 702 for a PRAT, a state machine 704 for
the PRAT, an RRC instance 708 for an SRAT, a state machine 706 for
the SRAT, an RRC connection 710 for the PRAT, an RRC connection 712
for the SRAT and one or more SRB(s) 714. In the example illustrated
in FIG. 7, radio resources for a plurality of RATs (e.g., the PRAT
and the SRAT) may be managed using a plurality of RRC instances
(e.g., a single instance of the control plane per configured
RAT).
[0083] FIG. 8 is a flow diagram 800 of an example method of
performing wireless communication in a WTRU configured for
multi-RAT operation corresponding to the embodiment illustrated in
FIG. 7. In the example illustrated in FIG. 8, a WTRU may establish
the first RRC connection 710 in the first RAT (e.g., the PRAT)
using the first RRC instance 702 (802). The WTRU may also establish
the second RRC connection 712 in the second RAT (e.g., the SRAT)
using the second RRC instance 708 (804).
[0084] In the embodiment illustrated in FIG. 7, each RRC instance
702 and 708 manages a single RRC connection 710 and 712 for its
respective configured serving cell(s) of the concerned RAT.
[0085] In an embodiment, the RRC connections 710 and 712 may be
established according to any number of different methods. In an
embodiment, a WTRU may receive RRC signaling from the network on an
existing RRC connection. The RRC signaling may include, for
example, a request to establish an additional RRC connection to an
SRAT, parameters to uniquely identify a concerned cell (e.g., a
frequency (DL and UL), a cell identity, and SI). In another
embodiment, the WTRU may receive an RRC reconfiguration message
from the network on an existing RRC connection that adds at least
one serving cell for an SRAT. The RRC reconfiguration message may
include, for example, parameters to uniquely identify a concerned
cell (e.g., a frequency (DL and UL), a cell identity, and SI). In
another embodiment, when a packet data protocol (PDP) context is
established for a new application, the WTRU may receive a request
to establish an additional RRC connection to an SRAT. In another
embodiment, a WTRU may autonomously initiate an access to a cell of
a second RAT while it is already connected to a first RAT. This
embodiment may be used, for example, where the WTRU supports
multi-RAT access using two independent RRC instances.
[0086] The WTRU may autonomously initiate the access to the cell of
the second RAT, for example, in response to receiving a paging
message on a RAT while the WTRU is camping on a cell with an RRC
instance in idle mode. Alternatively, a WTRU may autonomously
initiate an access to a cell of a secondary RAT on a condition that
it determines that an application is requesting service. For
example, if the WTRU wants to initiate a CS call, and if it
determines that it is a multi-RAT capable WTRU, it may initiate
access to a cell in the secondary RAT and, in an embodiment,
indicate the reason in the RRC connection establishment. In another
embodiment, the WTRU may send a request to the network over the
PRAT indicating that it may initiate the setup of the SRAT (e.g.,
following a WTRU specific trigger). The WTRU may send the request
to the network, for example, in response to receiving a certain
service request, and, in an embodiment, indicate a reason in the
RRC message sent over the PRAT. In this embodiment, the WTRU may
wait for an explicit setup message from the network to instantiate
the SRAT RRC connection.
[0087] In an embodiment, there may be no interaction between the
RRC instances 702 and 708. This may apply, for example, where a
multi-mode WTRU operates as a multi-homed IP device (e.g., where
each RAT may correspond to a different IP interface from a network
connectivity perspective), which may be configured using NAS
procedures. More specifically, the WTRU may be seen by the network
as a single device implementing two different IP network
interfaces, and, in an embodiment, each with its own PDP context
(i.e., IP address), control/user data paths, and security context.
RRM, mobility management, scheduling, and admission control for
each RRC connection may be independent from each other.
[0088] In another embodiment, there may be additional interactions
between the RRC instances 702 and 708. For example, an RRC message
on a first RRC connection (e.g., 702) may initiate a procedure by
the WTRU by which the WTRU may perform at least one of entering an
idle mode state, performing the cell selection procedure to
determine a suitable cell to camp on (or alternatively camp on a
cell of a frequency indicated in the said RRC message), acquire the
SI, monitor a paging channel, and perform an access to the SRAT.
Alternatively, it may immediately perform an initial access to a
cell, either selected by the WTRU using the cell selection
procedure or, alternatively, to a cell of a frequency indicated in
the RRC message.
[0089] In an embodiment, parameters may be exchanged or may be
common to a plurality of RRC instances, including at least one of
security parameters, NAS configuration (including PDP context), and
user plane parameters if a single data path is used). For example,
from a network connectivity perspective, the WTRU may still be seen
as a single device implementing a single IP network interface with
a single PDP context (i.e., IP address), a single data path, and a
single security context. The necessary parameter may be common to
all RRC instances and obtained, for example, from the PRAT
connection and/or the initial NAS configuration. In an embodiment,
RRM and mobility management for each RRC connection may be
configured independently from one another. Alternatively, mobility
may be based on the PRAT connection (e.g., 710).
[0090] In an embodiment, the WTRU may be configured with zero or
more SCells for the PRAT.
[0091] For the embodiments described with respect to FIGS. 5-8
wherein the control plane includes a separate RRC instance for each
configured RAT for radio resource management, the different RRC
instances may interact with one another using any one of a number
of different methods, for example, for security configuration,
security activation, security failure, failure handling,
reconfiguration of an RRC connection, RLM, error recovery, state
transition, transaction back to idle mode and action upon PUCCH/SRS
release requests.
[0092] With respect to security configuration, activation and
failure, the WTRU may use a second RRC instance when it adds a
first serving cell for an SRAT. In an embodiment, on a condition
that security is activated for another RRC instance, the WTRU may
consider that security is already activated for the second RRC
instance and apply the same configuration for integrity protection
and ciphering for the access stratum, when applicable.
[0093] With respect to failure handling, the WTRU may receive
control plane information (e.g., an RRC PDU or an IE) for the RRC
instance of an SRAT, which it may fail to process. On a condition
that the WTRU receives control plane information for the RRC
instance of an SRAT that it fails to process, the WTRU may indicate
to the network that the configuration failed, suspend any ongoing
transmission on a serving cell of the concerned SRAT, invalidate
the configuration for all servicing cells of the SRAT, remove the
configuration for all serving cells of the SRAT, indicate to the
network that the configuration failed and/or terminate the
secondary RAT RRC instance or secondary RAT RRC connection. On a
condition that the WTRU receives a configuration message that adds,
modifies or removes at least part of a configuration for at least
one serving cell of the SRAT, the WTRU may not successfully apply
the concerned configuration. In this case, the WTRU may invalidate
the configuration of the concerned serving cell, remove the
configuration of the concerned serving cell, invalidate the
configuration for all serving cells of the SRAT, remove the
configuration for all serving cells of the SRAT, indicate to the
network that the configuration failed and/or terminate the SRAT RRC
instance or secondary RAT connection. Any of these failures may not
impact the operation and/or configuration of the RRC connection for
the PRAT.
[0094] With respect to reconfiguring an RRC connection, the WTRU
may receive a radio resource reconfiguration message that adds a
configuration for a first LTE serving cell with configured UL
resources. The WTRU may subsequently initiate a procedure to gain
UL timing synchronization (e.g., a random access procedure on the
UL PRACH resources of the cell). In an embodiment, the WTRU may
receive a handover command, which may include a configuration with
at least one LTE serving cell with configured UL resources. In this
embodiment, in addition to the initial access to the HSPA target
cell, the WTRU may also initiate a procedure to gain UL timing
synchronization (e.g., a random access procedure on the UL PRACH
resources of the LTE target cell).
[0095] With respect to RLM, a WTRU may perform RLM for configured
serving cells of an SRAT. In an embodiment, the WTRU may determine
that it is experiencing RLF, for example, according to the
criterion for RLF of a serving cell of the corresponding RAT. When
a WTRU determines RLF (DL or UL) for a serving cell of a first RAT,
the WTRU may remove the configuration for all serving cells of the
first RAT, turn off the radio front end for the first RAT and/or
indicate to the network of the RLF condition for the concerned
serving cell. In an embodiment, the RRC instance of a first RAT may
indicate the UL RLF condition to the RRC instance of a second
RAT.
[0096] With respect to state transition and related procedures, a
change of RRC state in a first RRC instance may trigger a change in
state and/or a procedure in a second RRC instance. For example, a
state transition in a first RRC instance may trigger a state
transition in a second RRC instance, a release of the RRC
connection in a second RRC instance, and/or the WTRU may turn off
the radio front end for a second RAT corresponding to a second RRC
instance. In an embodiment, an RRC state transition from CELL_DCH
to any other state for an HSPA RRC instance may trigger an LTE RRC
instance to perform a state transition to RRC_IDLE, release the RRC
LTE connection and/or turn off the LTE front end. For example, if
HSPA is the PRAT, LTE may be the SRAT and UL resources may not be
configured for the LTE RAT. In another embodiment, an RRC state
transition to idle mode in a first RAT may trigger a state
transition to the idle mode for the RRC instance of each configured
SRAT or, alternatively, to release the RRC connection and/or turn
off the front end of each configured SRAT, for example. If HSPA is
the PRAT, LTE is the SRAT and only the HSPA RRC instance may
perform the cell reselection procedure.
[0097] For another example, a state transition in a second RRC
instance may not be allowed depending on the state of a first RRC
instance. In an embodiment, an RRC state may not be allowed in an
RRC instance for an SRAT based on the current state of another RRC
instance. In particular, a WTRU may not transition to a CELL-FACH
state or a CELL_PCH state for an HSPA RRC instance if an LTE RRC
instance is in an RRC_CONNECTED state.
[0098] For another example, the operational state of a second RRC
instance may follow the state of a first RRC instance. In an
embodiment, the initial state of an RRC instance of an HSPA SRAT
may be CELL_DCH when the state of the RRC instance of an LTE PRAT
is RRC_CONNECTED.
[0099] With respect to transition back to idle mode, a transition
to RRC idle for an RRC connection that is the PRAT of the WTRU may
trigger either the release of other RRC connections and/or a move
to RRC_IDLE for another RRC instance (e.g., all RATs or only a RAT
for which the WTRU should be in IDLE mode when not connected to the
network). The RRC instance of the PRAT may notify another RRC
instance for an SRAT of a change of state to IDLE. The RRC instance
for the SRAT may then perform the procedure to move to IDLE mode,
remove the dedicated configuration for the SRAT, revert to the
default configuration and/or activate and/or turn off the
transceiver module and/or some functionality of the SRAT.
[0100] With respect to action upon a PUCCH/SRS release request, the
PRAT LTE RRC instance may receive an indication to release
PUCCH/SRS dedicated resources from the lower layers (e.g., LTE
MAC). This may occur, for example, upon reaching the maximum number
of scheduling request (SR) transmissions on the configured PUCCH
resource for SR or if the timing alignment timer (TAT) expires.
When the TAT expires, the WTRU no longer has a valid timing advance
and is no longer synchronized for UL transmissions. In this case,
the RRC instance of the PRAT may indicate the loss of UL
synchronization in the PRAT to the RRC instance of an SRAT.
[0101] For embodiments that use a single RRC connection for all
configured RATs (e.g., embodiments described with respect to FIGS.
3, 4, 5 and 6 above), a WTRU may, for example, receive RRC messages
and configuration parameters regarding the SRAT via SRAT IEs that
are piggybacked inside RRC PDUs of the PRAT. In this embodiment, a
WTRU may multiplex and/or demultiplex RAT-specific IEs inside the
RRC PDU of the single RRC connection and identify the IE using an
explicit identifier (e.g., an identity of the RRC state machine or
SRAT) inside the RRC PDU.
[0102] In an embodiment, the RRC message of the PRAT may include an
SRAT container IE. The SRAT container IE may include the
information for the SRAT, which may be processed according to the
RRC of the SRAT. For example, if the PRAT is LTE, then an HSPA SRAT
may be established by including a utra-Secondarycell-Container IE.
In an embodiment, the presence of this IE may trigger the
initiation of the secondary RAT.
[0103] If more than one SRAT may be established, an SRAT type IE
and an SRAT message container IE may be used. The SRAT message
container IE may carry a message specified in another standard as
indicated by the SRAT type IE. This container may carry the
information and radio parameters required for the SRAT to be
configured.
[0104] For example, a WTRU may be configured such that each group
of cells configured for a given RAT is associated with an identity
for that RAT. When the WTRU receives an RRC PDU, it may determine
with what RAT an IE is associated and, for example, process the RRC
PDU according to the applicable RAT. Similarly, the WTRU may
transmit an RRC PDU including one or more information elements
inside the RRC PDU. If, at most, two RATs are supported, this may
be determined implicitly by the presence of the IE itself inside
the PDU.
[0105] For embodiments that use a separate RRC instance for each
configured RAT (e.g., embodiments described with respect to FIGS.
5, 6, 7 and 8 above), a WTRU may, for example, receive
configuration parameters regarding the SRAT via multiplexing an RRC
PDU for the PRAT and SRAT using different SRB identifiers
(SRB_IDs). In an embodiment, a WTRU may multiplex and/or
demultiplex RRC PDUs over the data path and identify the RRC
connection and/or state machine to which the RRC message is
applicable based on the radio bearer identity used for the
transmission of the RRC PDU.
[0106] For example, a WTRU may be configured such that one or more
SRBs are associated with control signaling of a specific RAT, for
example, based on SRB_ID. When the WTRU receives an RRC PDU, it may
determine what radio bearer the PDU is associated with and, for
example, apply the proper security context for authentication (if
any) and deciphering if the WTRU is configured with a RAT-specific
security context and/or process the RRC PDU using the applicable
RRC state machine for the associated RAT. Similarly, the WTRU may
transmit an RRC PDU using the associated with the applicable RRC
state machine.
[0107] In an embodiment, the SRBs applicable for an SRAT may be
configured after security activation and being associated with a
given priority. For example, the WTRU may be configured such that
the SRBs applicable to, for example, a subset or a type of an HSPA
RRC PDU have the same (or, alternatively, a lower) priority than
SRB 1 for the transport of the HSPA RRC PDUs over the LTE MAC. For
example, the WTRU may be configured such that the logical
channel(s) applicable to, for example, a subset or a type of LTE
RRC PDU are mapped to a specific priority in the multiplexing
functionality of MAC-ehs.
[0108] For embodiments that use a single RRC instance for all
configured RATs (e.g., embodiments described with respect to FIGS.
3 and 4 above), radio resource management may be carried out using
one of more of the examples described below on a condition that the
WTRU receives a configuration that adds at least one serving cell
for an SRAT. In such embodiments, a WTRU may have an established
RRC connection (e.g. 306 in FIG. 3) with a PRAT.
[0109] In an embodiment, the WTRU may add a serving cell for an
SRAT when security is activated (e.g., for the PRAT), in which case
it may apply the same configuration for integrity protection and
ciphering for the access stratum when applicable (e.g., when
multiple data paths are used).
[0110] In an embodiment, a WTRU may receive an RRC message that
adds, modifies or removes at least part of a configuration for at
least one serving cell of the SRAT. The WTRU may not successfully
apply the concerned configuration, in which case it may invalidate
the configuration of the concerned serving cell, remove the
configuration of the concerned serving cell, invalidate the
configuration for all serving cells of the SRAT, remove the
configuration for all serving cells of the SRAT, turn off the radio
front end for the SRAT, indicate to the network that the
configuration failed and/or terminate the SRAT RRC instance of the
SRAT RRC connection. In particular, a failure to apply a
configuration for an SRAT may not impact the operation and/or the
configuration of the RRC connection for the PRAT. In case of a
failure to successfully complete an RRC procedure applicable to an
SRAT, the WTRU may abort the procedure and revert to the state
before the WTRU initiated the procedure for the concerned SRAT.
[0111] When LTE is the PRAT, the RRC instance may perform radio
resource management for an SRAT according to any of the following
embodiments. In an embodiment, the WTRU operation for the PRAT may
be according to typical procedures for the concerned RAT. In an
embodiment, a WTRU may perform RLM for configured serving cells of
an LTE PRAT, for example, for the PCell. The WTRU may determine,
according to the criterion for RLF of a serving cell of the
corresponding RAT, that it is experiencing UL RLF on the PCell of
the LTE PRAT. The WTRU may perform an RRC state transition away
from RRC_CONNECTED to RRC_IDLE when it determines RLF (DL or UL)
for a PCell of an LTE PRAT, in which case it may remove the
configuration for all serving cells of an HSPA SRAT and/or turn off
the radio front end for the HSPA SRAT.
[0112] The WTRU may also perform RLM for configured serving cells
of an HSPA SRAT. The WTRU may determine, according to the criterion
for RLF of a serving cell of the corresponding RAT, that it is
experiencing UL RLF on the primary serving cell. On a condition
that the WTRU determines UL RLF for a serving cell of an HSPA SRAT,
the WTRU may invalidate the configuration of the concerned serving
cell, remove the configuration of the concerned serving cell,
invalidate the random access configuration of the concerned serving
cell, remove the random access configuration of the concerned
serving cell, invalidate the configuration for all serving cells of
the HSPA SRAT, remove the configuration for all serving cells of
the HSPA SRAT, turn off the radio front end for the HSPA SRAT,
indicate to the network of the UL RLF condition for the concerned
serving cell, consider the secondary RAT serving cells as
deactivated and/or terminate the SRAT RRC instance of SRAT RRC
connection.
[0113] In an embodiment, the WTRU may determine, according to the
criterion for RLF of a serving cell of the corresponding RAT, that
it is experiencing DL RLF. On a condition that the WTRU determines
DL RLF for a serving cell of an HSPA SRAT, the WTRU may invalidate
the configuration of the concerned serving cell, remove the
configuration of the concerned serving cell, invalidate the
configuration for all serving cells of the HSPA SRAT, remove the
configuration for all serving cells of the HSPA SRAT turn off the
radio front end for the HSPA SRAT and/or indicate to the network
the DL RLF condition for the concerned serving cell.
[0114] A WTRU may perform an RRC state transition from LTE
RRC_CONNECTED to LTE RRC_IDLE, in which case the WTRU may
invalidate the configuration for all serving cells of the SRAT,
remove the configuration for all serving cells of the SRAT, turn
off the radio front end for the SRAT and/or terminate the secondary
RAT RRC instance or SRAT RRC connection.
[0115] The PRAT LTE RRC instance may receive an indication to
release PUCCH/SRS dedicated resources from the lower layers (e.g.,
LTE MAC). This may occur, for example, upon reaching the maximum
number of SR transmissions on the configured PUCCH resource for SR
or if the TAT expires. When the TAT expires, the WTRU no longer has
a valid timing advance and is no longer synchronized for UL
transmissions. In this case, the WTRU may invalidate the
configuration for all serving cells of the SRAT, remove the
configuration for all serving cells of the SRAT, turn off the radio
front end for the SRAT and/or terminate the SRAT RRC instance or
SRAT RRC connection.
[0116] When HSPA is the PRAT, the RRC instance may perform radio
resource management for an SRAT according to any of the following
embodiments. In addition, the WTRU operation for the PRAT may be
according to typical procedures for the concerned RAT.
[0117] In an embodiment, the WTRU may receive a radio resource
reconfiguration message that adds a configuration for a first LTE
serving cell with configured UL resources, and subsequently may
initiate a procedure to gain UL timing synchronization (e.g., a
random access procedure on the UL PRACH resources of the cell). In
an embodiment, the WTRU may receive a handover command, which may
include a configuration for at least one LTE serving cell with
configured UL resources. The WTRU may, in addition to the initial
access to the HSPA target cell, also initiate a procedure to gain
UL timing synchronization (e.g., a random access procedure on the
UL PRACH resources of the LTE target cell).
[0118] In an embodiment, the WTRU may perform RLM for one or more
of the configured serving cells of a PRAT, in particular, for the
primary serving cell of the HSPA PRAT. The WTRU may determine,
according to, for example, the criterion for RLF of a serving cell
of the corresponding RAT, that it is experiencing UL RLF on the
primary serving cell. On a condition that it determines UL RLF for
a primary serving cell of an HSPA PRAT, the RRC instance for the
HSPA PRAT may receive a first out-of-synch indication from the
physical layer and may refrain from performing UL transmissions. If
at least one serving cell of the LTE SRAT is configured with UL
resources and may transmit UL feedback information on the serving
cell, then the WTRU may continue any transmission on the LTE
SRAT.
[0119] The WTRU may perform an RRC state transition away from
CELL_DCH (and/or to CELL_FACH) when it determines RLF (DL and/or
UL) for a primary serving cell of an HSPA PRAT, in which case it
may remove the configuration for all serving cells of the LTE SRAT,
turn off the radio front end for the LTE SRAT and/or consider the
LTE SRAT as deactivated by an order.
[0120] In an embodiment, the WTRU may perform RLM for configured
serving cells of an LTE SRAT. The WTRU may determine, according to
the criterion for RLF of a serving cell of the corresponding RAT,
that it is experiencing UL RLF on a serving cell of an LTE SRAT, in
particular the PCell. On a condition that it determines UL RLF for
a serving cell of an LTE SRAT, the WTRU may invalidate the
configuration of the concerned serving cell, remove the
configuration of the concerned serving cell, invalidate the random
access configuration of the concerned serving cell, remove the
random access configuration of the concerned serving cell,
invalidate the configuration for all serving cells of the LTE SRAT,
remove the configuration for all serving cells of the LTE SRAT,
turn off the radio front end for the LTE SRAT, indicate to the
network the UL RLF condition for the concerned serving cell and/or
terminate the SRAT RRC instance or SRAT RRC connection.
[0121] In an embodiment, the WTRU may determine, according to the
criterion for RLF of a serving cell of the corresponding RAT, that
it is experiencing DL RLF. On a condition that it determines DL RLF
for a serving cell of an LTE SRAT, the WTRU may invalidate the
configuration of the concerned serving cell, remove the
configuration of the concerned serving cell, invalidate the
configuration for all serving cells of the LTE SRAT, remove the
configuration for all serving cells of the LTE SRAT, turn off the
radio front for the LTE SRAT, indicate to the network the DL RLF
condition for the concerned serving cell and/or terminate the SRAT
RRC instance or SRAT RRC connection.
[0122] In an embodiment, the WTRU may perform an RRC state
transition from a connected state (e.g., CELL_DCH, CELL_PCH or
URA_PCH) to an idle mode, in which case the WTRU may invalidate the
configuration for all serving cells of the LTE SRAT, remove the
configuration for all serving cells of the LTE SRAT and/or turn off
the radio front end for the LTE SRAT.
[0123] 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.
* * * * *