UNIT COOPERATION

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. provisional application

No. 61/345,783 filed May 18, 2010, the contents of which are hereby incorporated by reference herein.

BACKGROUND

[0002] As the distance between a wireless transmit/receive unit (WTRU) and a base station increases, reduced coverage or capacity may result. For example, as the distance between the WTRU and the base station increases, the rate of throughput may decrease. Further, the WTRU may be located at such a distance from the base station or may have an obstructed propagation channel such that the WTRU is unable to receive any coverage from the base station. Accordingly, it may be advantageous for a WTRU to use another WTRU as a "relay" to access the base station.

[0003] For example, a WTRU that does not have an optimal radio link may use another WTRU with a better radio link to access the base station. In this scenario, the other WTRU acts as a "relay" between the WTRU and the base station. A WTRU-to-WTRU relay may be used as either a capacity enhancement or a coverage enhancement. A capacity enhancement relay relates to a scenario in which the WTRUs are within the range of a base station, but the overall throughput and capacity of a network may be increased via the use of one or more relay WTRUs. A coverage enhancement relay relates to a scenario in which one or more WTRUs are unable to receive any coverage from a base station. The WTRUs that are unable to receive any coverage may be provided coverage through the use of one or more relay WTRUs that are receiving coverage from the base station. The use of any relay scheme may require cooperation between the plurality of WTRUs and base stations involved. SUMMARY

[0004] A method and apparatus for WTRU cooperation are disclosed. An evolved Node B (eNB) may transmit information to a terminal WTRU (T-WTRU) and/or a helper WTRU (H-WTRU). The H-WTRU may re-transmit the information to the T-WTRU. The eNB may re-transmit the information to the T- WTRU. The transmissions to the T-WTRU may be performed during a first hop or a second hop. The eNB may send scheduling and control information to the T- WTRU. In the uplink direction, a T-WTRU may transmit information to an eNB and/or a H-WTRU. The H-WTRU may re-transmit the information to the eNB. The T-WTRU may re-transmit the information to the eNB. The transmissions to the eNB may be performed during a first hop or a second hop. An "RRC_HELPER_STATE" may be used to indicate that a WTRU is an active H- WTRU. A Hybrid Automatic Repeat Request (HARQ) entity at the H-WTRU may perform decode-forward functions and/or acknowledgement functions. A T- WTRU may receive logical channel data from an eNB on a first Physical Downlink Shared Channel (PDSCH). A T-WTRU may receive Dedicated Traffic Channel (DTCH) data from the H-WTRU on a second PDSCH. Resources may be partitioned by time and/or frequency. The traditional radio link (TRL) between the eNB and the T-WTRU may be in the same band (in-band) as the crosslink (XL) between the H-WTRU and the T-WTRU or the TRL may be in a different band (out-band) than the XL. At least one timing parameter may be used to synchronize communications between the eNB, T-WTRU, and H-WTRU.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] A more detailed understanding may be had from the following description, given by way of example in conjunction with the accompanying drawings wherein: [0006] FIG. 1A is a system diagram of an example communications system in which one or more disclosed embodiments may be implemented;

[0007] FIG. IB is a system diagram of an example wireless transmit/receive unit (WTRU) that may be used within the communications system illustrated in FIG. 1A;

[0008] 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;

[0009] FIG. 2 shows an overview of an evolved Node B (eNB) and a plurality of WTRUs participating in WTRU cooperation;

[0010] FIGs. 3A-D show examples of downlink relay options;

[0011] FIGs. 4A-C show examples of uplink relay options;

[0012] FIGs. 5A-B show examples of protocol stacks for WTRU cooperation;

[0013] FIG. 6 shows an example downlink channel scheme for WTRU cooperation;

[0014] FIG. 7 shows an example uplink channel scheme for WTRU cooperation;

[0015] FIG. 8 shows an example Medium Access Control (MAC) architecture for WTRU cooperation;

[0016] FIG. 9 shows an example WTRU Radio Resource Control (RRC) state machine;

[0017] FIGs. 10A-B show examples of frequency division multiplexing

(FDM) resource partitioning in frequency division duplex (FDD);

[0018] FIGs. 11A-B show examples of FDM resource partitioning in time division duplex (TDD);

[0019] FIG. 12 shows an example of time division multiplexing (TDM) resource allocation in FDD;

[0020] FIG. 13 shows an example of downlink time alignment for traditional radio link and crosslink reception in a carrier;

[0021] FIG. 14 shows an example of time alignment for crosslink reception at a helper WTRU; and [0022] FIG. 15 shows an example of selection of a helper WTRU.

DETAILED DESCRIPTION

[0023] 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.

[0024] 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 tablet personal computer, a personal computer, a wireless sensor, consumer electronics, and the like.

[0025] 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.

[0026] 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.

[0027] 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).

[0028] 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).

[0029] 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).

[0030] 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 IX, 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] FIG. IB is a system diagram of an example WTRU 102. As shown in FIG. IB, 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 106, 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 subcombination of the foregoing elements while remaining consistent with an embodiment.

[0036] 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. IB 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.

[0037] 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.

[0038] In addition, although the transmit/receive element 122 is depicted in

FIG. IB 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.

[0039] 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.

[0040] 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 106 and/or the removable memory 132. The non-removable memory 106 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).

[0041] 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. [0042] 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.

[0043] 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® 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] The MME 142 may be connected to each of the eNode-Bs 142a, 142b,

142c in the RAN 104 via an Si interface and may serve as a control node. For example, the MME 142 may be responsible for authenticating users of the WTRUs 102a, 102b, 102c, bearer activation/deactivation, selecting a particular serving gateway during an initial attach of the WTRUs 102a, 102b, 102c, and the like. The MME 142 may also provide a control plane function for switching between the RAN 104 and other RANs (not shown) that employ other radio technologies, such as GSM or WCDMA.

[0049] The serving gateway 144 may be connected to each of the eNode Bs

140a, 140b, 140c in the RAN 104 via the Si 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.

[0050] 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.

[0051] 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.

[0052] WTRU-to- WTRU relays may be used in a variety of ways and for a variety of purposes. As described above, relays may be used for both capacity enhancements and coverage enhancements. Capacity enhancements may increase throughput to and from particular WTRUs as well as increase the capacity of a network as a whole. Coverage enhancements may provide coverage to one or more WTRUs that are not within a coverage area via the help of other WTRUs that are within a coverage area.

[0053] More particularly, capacity enhancements may be employed in several scenarios. For example, a particular WTRU may not have an adequate radio link with an eNB. This may occur because, for example, a WTRU is located inside of a building. One or more other WTRUs in the vicinity of the WTRU may have better direct links with the eNB. Each of these other WTRUs may act as a "helper WTRU" to increase the throughput to the target WTRU by, for example, relaying data to and from the eNB. As an additional example, a relay may be used to improve the scalability of a cellular network. For example, this may occur if there is high temporal correlation of requested services. An example of this may be if a large crowd of people are gathered in one place, such as in a stadium to watch a popular event, and a particular situation or event is likely to trigger many people to attempt to use their WTRUs to request the same content (such as a replay). In this example, WTRUs may receive requested data as well as help neighboring WTRUs by relaying the same data to the neighboring WTRUs.

[0054] As used herein, the term "traditional radio link" (TRL) may refer to a radio link between an eNB and a WTRU. As used herein, the term "terminal WTRU" (T-WTRU) may refer to a WTRU that is assisted by one or more helper WTRUs. As used herein, the term "helper WTRU" (H-WTRU) may refer to a WTRU that assists one or more T- WTRUs and/or acts as a relay. As used herein, the term "other WTRU" (O-WTRU) may refer to any WTRU that is not currently being used or described as a T-WTRU or H-WTRU. As used herein, the term "crosslink" (XL) may refer to a radio link between a H-WTRU and a T-WTRU. As used herein, the term "helper active set" (HAS) may refer to a set of H-WTRUs associated with a given T-WTRU. The terms used herein are for illustrative purposes, and other terms may be used.

[0055] In a capacity enhancement scenario, a direct link may remain active between the eNB and the T-WTRU. The direct link may provide sufficient signal quality to allow the T-WTRU to receive broadcast and unicast control signaling from the eNB. Further, the eNB may receive physical layer (PHY) and higher layer control signaling from the T-WTRU. User data may also be communicated directly from the eNB to the T-WTRU. This communication may occur while either the eNB or T-WTRU is communicating with a H-WTRU. The T-WTRU may be considered to be anchored to (or camped on) the eNB whether or not the T-WTRU is communicating via a crosslink. The H-WTRU may not transmit system information and other signaling necessary to support camping on an eNB. The eNB may schedule the relay transmissions and indicate the scheduling directly to the T-WTRU.

[0056] FIG. 2 shows an overview 200 of an eNB and a plurality of WTRUs participating in WTRU cooperation. The eNB 202 may be in communication with a plurality of O-WTRUs 204A-B, a plurality of H-WTRUs 206A-B, and a T-WTRU 208. Direct Link Coverage Area 210 may include a plurality of direct links (also referred to as traditional radio links) 212A-E between the eNB 202 and the 0- WTRUs 204A-B, the H-WTRUs 206A-B, and the T-WTRU 208. Crosslink Coverage Area 214 may include a plurality of crosslinks (XLs) 216A-B between the H-WTRUs 206A-B and the T-WTRU 208, respectively.

[0057] XLs 216A-B may be WTRU-to-WTRU radio links between the H-

WTRUs 206A-B and the T-WTRU 208. The eNB 202 may share its spectral resources between each of the wireless links, TRLs 212A-E and XLs 216A-B. The resources allocated for XLs 216A-B may be reused multiple times within the same cell beyond the reuse that multiple -input multiple -output (MIMO) techniques allow.

[0058] For a given connection, any WTRU may assume the role of an H-

WTRU or a T-WTRU. The H-WTRUs 206A-B may be responsible for helping deliver data to or from a T-WTRU 208. The H-WTRUs 206A-B may serve as intermediate nodes between the eNB 202 and T-WTRU 208. The T-WTRU 208 may receive assistance from the H-WTRUs 206A-B. WTRUs that do not assume the role of an H-WTRU or T-WTRU may utilize only TRLs and may be referred to as the O-WTRUs. A helper function may be used as a mechanism for transferring data between the T-WTRU 208 and the eNB 202 with assistance from the H-WTRUs 206A-B. For example, the H-WTRUs 206A-B may relay the data to the T-WTRU 208 using one of several mechanisms, such as amplify-and- forward, decode-and-forward, compress-and-forward, and estimate-and-forward.

[0059] FIGs. 3A-D show examples 300A-D of downlink relay options for a capacity enhancement. Shown in FIGs. 3A-D is an eNB 302, a T-WTRU 304, and an H-WTRU 306, and various communication signals between these entities, as described in detail in the following. As used herein, the term "first hop" may mean a first time period during which a transmission may occur and the term "second hop" may mean a second time period during which a transmission may occur. FIG. 3A shows an example of a downlink relay option. The eNB 302 may transmit information to the T-WTRU 304 and the H-WTRU 306. The transmission from the eNB 302 to the T-WTRU 304 may occur during a first hop 310. The transmission from the eNB 302 to the H-WTRU 306 may also occur during a first hop 312. The eNB 302, T-WTRU 304, and H-WTRU 306 may determine whether the transmitted information was received using acknowledgements (ACKs) and negative acknowledgements (NACKs). Still referring to FIG. 3A, the T-WTRU 304 may transmit a NACK 316 to the eNB 302 while the H-WTRU 306 may transmit an ACK 318 to the eNB 302. In this example, the T-WTRU 304 may not have received the transmission from the eNB 302 while the H-WTRU 306 may have received the transmission from the eNB 302. The T-WTRU 304 may transmit a NACK 320 to the H-WTRU 306 to indicate, for example, that the T-WTRU 304 did not receive the transmission from the eNB 302. In this example, the H-WTRU 306 may re-transmit the information during a second hop 324 to the T-WTRU 304. As shown in this example, the H-WTRU 306 may act as a relay for re-transmission. Throughout the example described above, control data may be communicated directly between the eNB 302 and the T-WTRU 304.

[0060] FIG. 3B shows another example 300B of a downlink relay option.

An eNB 302 may transmit information to a T-WTRU 304 and a H-WTRU 306. The transmission from the eNB 302 to the T-WTRU 304 may occur during a first hop 328. The transmission from the eNB 302 to the H-WTRU 306 may also occur during a first hop 330. The H-WTRU 306 may transmit the information during a second hop 332 to the T-WTRU 302. The eNB 302, T-WTRU 304, and H-WTRU 306 may determine whether the transmitted information was received using ACKs and NACKs. In this example, neither the T-WTRU 304 nor the H-WTRU 306 may have received the transmission from the eNB 302. Still referring to FIG. 3B, the T-WTRU 304 may transmit a NACK 336 to the eNB 302 and the H- WTRU 306 may transmit a NACK 338 to the eNB 302. The T-WTRU 304 may transmit a NACK 340 to the H-WTRU 306 to indicate, for example, that the T- WTRU 304 did not receive the transmission from the eNB 302. In this example, the eNB 302 may re-transmit the information to both the T-WTRU 304 and the H-WTRU 306. The re-transmission may be similar to the original transmission. For example, the transmission from the eNB 302 to the T-WTRU 304 may occur during a first hop 344 and the transmission from the eNB 302 to the H-WTRU 306 may also occur during a first hop 346. The H-WTRU 306 may transmit the information during a second hop 348 to the T-WTRU 302. As shown in this example, the eNB 302 may perform re-transmissions to both the T-WTRU 304 and H-WTRU 306 if neither the T-WTRU 304 nor the H-WTRU 306 receives the original transmission. Throughout the example described above, control data may be communicated directly between the eNB 302 and the T-WTRU 304.

[0061] FIG. 3C shows another example 300C of a downlink relay option.

An eNB 302 may transmit information to a T-WTRU 304 and a H-WTRU 306. The transmission from the eNB 302 to the H-WTRU 306 may occur during a first hop 352. The transmission from the eNB 302 to the T-WTRU 304 may occur during a second hop 354. The H-WTRU 306 may transmit the information during a second hop 356 to the T-WTRU 302. The eNB 302, T-WTRU 304, and H-WTRU 306 may determine whether the transmitted information was received using ACKs and NACKs. In this example, the T-WTRU 304 may not have received the transmission from the eNB 302 while the H-WTRU 306 may have received the transmission from the eNB 302. Still referring to FIG. 3C, the T- WTRU 304 may transmit a NACK 360 to the eNB 302 and the H-WTRU 306 may transmit an ACK 362 to the eNB 302. The T-WTRU 304 may transmit a NACK 364 to the H-WTRU 306 to indicate, for example, that the T-WTRU 304 did not receive the transmission from the eNB 302. In this example, the eNB 302 may re-transmit the information 368 to the T-WTRU 304. The H-WTRU 306 may also re-transmit the information 370 to the T-WTRU 304. As shown in this example, the H-WTRU 306 may act as a relay for re-transmission and the eNB 302 may also perform re-transmission. Throughout the example described above, control data may be communicated directly between the eNB 302 and the T-WTRU 304.

[0062] FIG. 3D shows another example 300D of a downlink relay option.

An eNB 302 may transmit information to a H-WTRU 306. The transmission from the eNB 302 to the H-WTRU 306 may occur during a first hop 374. The H- WTRU 306 may transmit the information during a second hop 376 to the T- WTRU 302. The eNB 302, T-WTRU 304, and H-WTRU 306 may indicate whether the transmitted information was received using ACKs and NACKs. In this example, the T-WTRU 304 may not have received the transmission from the eNB 302. Still referring to FIG. 3C, the T-WTRU 304 may transmit a NACK 380 to the eNB 302. The re-transmission may be performed in the same manner as the original transmission. The eNB 302 may transmit the information to the H- WTRU 306 during a first hop 384. The H-WTRU 306 may re-transmit the information during a second hop 386 to the T-WTRU 304. As shown in this example, the H-WTRU 306 may act as a relay for transmission and retransmission. The eNB 302 may also perform re-transmission. Throughout the example described above, control data may be communicated directly between the eNB 302 and the T-WTRU 304.

[0063] FIGs. 4A-C show examples 400A-C of uplink relay options for a capacity enhancement. Shown in FIGs. 4A-C are a T-WTRU 402, an eNB 404, and an H-WTRU 406, and various communication signals between these entities, as described in detail in the following. FIG. 4A shows an example 400A of an uplink relay option. The T-WTRU 402 may transmit information to the eNB 404 during the first hop and the second hop 410. The T-WTRU 402 may also transmit information to the H-WTRU 406 during the first hop 412. The H- WTRU 406 may transmit the information to the eNB 404 during a second hop 414 and, as explained above, the T-WTRU 402 may also transmit to the eNB 404 during the second hop 410. The eNB 404 may listen to the first hop transmissions and the second hop transmissions from the T-WTRU 402 and the H-WTRU 404.

[0064] FIG. 4B shows another example 400B of an uplink relay option. The

T-WTRU 402 may transmit information to the eNB 404 during a first hop 420. The T-WTRU 402 may also transmit information to the H-WTRU 406 during the first hop 422. The H-WTRU 406 may transmit the information to the eNB 404 during a second hop 424. Thus, the eNB 404 may listen to the XL transmission from the T-WTRU 402 to the H-WTRU 406 during the first hop 422. Alternatively or additionally, the T-WTRU 402 may transmit to the eNB 404 over a TRL and transmit to the H-WTRU 406 over a XL. [0065] FIG. 4C shows another example 400C of an uplink relay option. The

T-WTRU 402 may transmit information to the H-WTRU 406 during a first hop 430. The T-WTRU 402 may transmit information to the eNB 404 during a second hop 432. The H-WTRU 406 may also transmit the information to the eNB 404 during the second hop 434.

[0066] The examples described above are for exemplary purposes and may be used in any combination. In any of the examples described above, the eNB may listen to an XL transmission during a first hop. Alternatively or additionally, smart power control may allow the XL transmission to be transmitted at a lower power than necessary to reach the eNB. Control signaling on a Physical Uplink Control Channel (PUCCH) may still be performed such that the signaling will be decodable by the eNB. For example, smart power control may be used. XL transmissions may be intended to be received by a WTRU that may be closer to the transmitting WTRU than an eNB. XL transmissions may therefore require a lower transmit power, such that the transmission reaches the recipient WTRU, but may not reach the eNB. In this example, it may be necessary to allow control signaling to be received at the eNB.

[0067] FIGs. 5A-B show examples of protocol stacks for control planes and user planes 500A-B. To enable the relay options described herein, modifications to the protocol stack may be implemented. Modifications to existing protocols and inclusion of new protocols may be required to implement WTRU cooperation.

[0068] FIG. 5A shows one example of a modified protocol stack with control plane and user plane signaling 500A. Signaling for an MME 502, an eNB 504, a H-WTRU 506, and a T-WTRU 508 is shown. The signaling includes control plane signaling 512 and user plane signaling 516. Referring to the control plane 512, the MME 502 may communicate with the T-WTRU 508 via Non Access Stratum (NAS) signaling 520. The eNB 504 may communicate with the T-WTRU 508 via RRC signaling 522. Referring to the user plane 516, the eNB 504 may communicate with the T-WTRU 508 via Radio Link Control (RLC) signaling 524. The eNB 504 may communicate with the T-WTRU 508 via Medium Access Control (MAC) signaling 526. The eNB 504 may communicate with the T-WTRU 508 via a Hybrid Automatic Repeat Request (HARQ) entity and may use the H- WTRU 506 as a relay. In this example, the HARQ entity at the H-WTRU 506 may perform both acknowledgement functions 528 as well as decode-forward functions 530. The acknowledgement functions 528 and the decode-forward functions 530 may be performed between the H-WTRU 506 and the eNB 504 and/or the T-WTRU 508. The eNB 504 may also communicate directly with the T-WTRU 508 via the respective HARQ entities of the eNB 504 and T-WTRU 508. The HARQ entities may perform acknowledgement functions 532 and decode- forward functions 534. The eNB 504 may communicate with the T-WTRU 508 via the physical layer (PHY). The eNB may communicate with the T-WTRU 508 via the PHY 536 at the H-WTRU 506 or the eNB may communicate directly 538 with the T-WTRU 508.

[0069] FIG. 5B shows another example of a modified protocol stack with control plane and user plane signaling 500B. Signaling for an MME 502, an eNB 504, a H-WTRU 506, and a T-WTRU is shown. The signaling includes control plane 512 signaling and user plane 516 signaling. Referring to the control plane 512, the MME 502 may communicate with the T-WTRU 508 via NAS signaling 550. The eNB 504 may communicate with the T-WTRU 508 via RRC signaling 552. Referring to the user plane 516, the eNB 504 may communicate with the T- WTRU 508 via RLC signaling 554. The eNB 504 may communicate with the T- WTRU 508 via MAC signaling 556. The eNB 504 may communicate with the T- WTRU 508 via a HARQ entity and may use the H-WTRU 506 as a relay. In this example, the HARQ entity at the H-WTRU 506 may perform decode-forward functions 558. The decode-forward functions 558 may be performed between the H-WTRU 506 and the eNB 504 and/or the T-WTRU 508. The eNB 504 may also communicate directly with the T-WTRU 508 via the respective HARQ entities of the eNB 504 and T-WTRU 508. The HARQ entities may perform acknowledgement functions 560 and decode-forward functions 562. The eNB 504 may communicate with the T-WTRU 508 via the PHY. The eNB may communicate with the T-WTRU 508 via the PHY 564 at the H-WTRU 506 or the eNB may communicate directly 566 with the T-WTRU 508. [0070] As described above, a TRL may exist between the eNB and the T-

WTRU. A XL between the T-WTRU and H-WTRU may allow higher data rate applications to be performed at the T-WTRU. Higher layer control information such as, for example, system information, paging, RACH access, RRC signaling, NAS signaling (for example, signaling radio bearers), or multicast traffic may be transmitted on the TRL between the eNB and the T-WTRU. The higher level control information may be on the TRL and may not need to be transmitted via the H-WTRU. Appropriate channels may be mapped to implement the radio links and signaling described above. For example, logical and transport channels may be routed via the H-WTRU or may be routed directly to the T-WTRU. Multiple traffic channels may be mapped to a shared channel to be transmitted via the H-WTRU. For example, one or more Dedicated Traffic Channels (DTCHs) may be mapped to a Physical Downlink Shared Channel (PDSCH) or a Physical Uplink Shared Channel (PUSCH).

[0071] In the downlink, there may be two instantiations of PDSCH. One

PDSCH instantiation may be used for carrying logical channels. The logical channels may include a Paging Control Channel (PCCH), Broadcast Control Channel (BCCH), Common Control Channel (CCCH), one or more Dedicated Control Channels (DCCHs), and one or more DTCHs. Any of these logical channels may be routed directly to a T-WTRU without the assistance of a H- WTRU. A DTCH mapped to a PDSCH may carry low data rate services such as, for example, voice. Another PDSCH instantiation may be used for carrying DTCH logical channel data to be routed via a H-WTRU to a T-WTRU.

[0072] FIG. 6 shows an example of downlink logical and transport channel mapping 600. FIG. 6 shows downlink logical channels 602, downlink transport channels 606, and downlink physical channels 610. At least one instance of a PDSCH 620 is shown. Logical channels PCCH 622, BCCH 624, CCCH 626, DCCH 628, and DTCH 630 are shown. Downlink transport channels Paging Channel (PCH) 632, Broadcast Channel (BCH) 634, and Downlink Shared Channel (DL-SCH) 636 are shown. A Physical Broadcast Channel (PBCH) 638 is shown. Not all channels are shown. One or more of any of logical channels PCCH 622, BCCH 624, CCCH 626, DCCH 628, or DTCH 630 may be routed directly to a T-WTRU without the assistance of a H-WTRU. Another instance of a PDSCH 620 may carry DTCH 630 logical channel data to be routed via a H- WTRU to a T-WTRU. The descriptions and channel mappings described herein are for exemplary purposes and any channels may be used to support WTRU cooperation.

[0073] In the uplink, there may be two instantiations of PUSCH. One

PUSCH instantiation may be used for carrying logical channels. The logical channels may include a CCCH, one or more DCCHs, and one or more DTCHs. Any of these logical channels may be routed directly to an eNB without the assistance of a H-WTRU. A DTCH mapped to a PUSCH may carry low data rate services such as, for example, voice. Another PUSCH instantiation may be used for carrying DTCH logical channel data to be routed via a H-WTRU to an eNB.

[0074] FIG. 7 shows an example of uplink logical and transport channel mapping 700. FIG. 7 includes uplink logical channels 702, uplink transport channels 706, and uplink physical channels 710. At least one instance of a PUSCH 720 is shown. Logical channels are shown. Uplink transport channel Uplink Shared Channel (UL-SCH) 730 is shown. Not all channels are shown. One or more of any of logical channels CCCH 722, DCCH 724, and DTCH 726 may be routed directly to an eNB without the assistance of a H-WTRU. Another instance of a PUSCH 720 may carry DTCH 726 logical channel data to be routed via a H-WTRU to a T-WTRU. The descriptions and channel mappings described herein are for exemplary purposes and any channels may be used to support WTRU cooperation.

[0075] FIG. 8 shows an example of MAC architecture 800. While WTRU

MAC architecture 800 may be used for exemplary purposes, similar MAC architecture may be used at an eNB or other entity. To enable user traffic to be routed via a H-WTRU, traditional MAC architecture may be updated. The MAC architecture as illustrated in FIG. 8 includes upper layers 804 and lower layers 806. The upper layers 804 may include at least a PCCH 810, a BCCH 820, a CCCH 822, a DCCH 824, one or more DTCHs 826, and a MAC-control 874. The lower layers 806 may include at least one or more Downlink Shared Channels (DL-SCHs) 830a-b, one or more Uplink Shared Channels (UL-SCHs) 832a-b, a PCH 876, a BCH 878, and a Random Access Channel (RACH) 880. Not all channels are shown. A Random Access Control entity 858 and a Control entity 860 are shown.

[0076] The one or more DTCHs 826 may pass through a new logical channel prioritization (LCP) 840 and/or a multiplexing (or de-multiplexing) module 842 and/or a HARQ entity module 844. The MAC architecture described herein may be used in parallel with LCP and (de-) multiplexing modules currently used for TRLs between eNBs and T-WTRUs. The CCCH 822 and/or the DCCH 824 may pass through an LCP 850 and/or a multiplexing (or demultiplexing) module 852 and/or a HARQ entity module 854. The functionality supported by the LCPs 840, 850 and the (de-) multiplexing modules 842, 852 in the MAC architecture 800 may be similar to the standard functionality of LCPs and (de-) multiplexing modules. One or more of the HARQ entities 844, 854 may be modified to support routing traffic through a H-WTRU. The modifications to the HARQ entities 844, 854 may be specific to each configuration option and are explained in detail below.

[0077] To perform the WTRU cooperation described herein, a new RRC state called "E-UTRA RRC HELPER" state may be defined. The new "E-UTRA RRC HELPER" state may support helper functions required for H-WTRU operation. A particular WTRU may be part of a helper active set (HAS) and may be selected to be an "active" H-WTRU. If an RRC connection is established with a H-WTRU, a new command called "ENTER HELPER MODE" may be received at the H-WTRU. The "ENTER HELPER MODE" command may transition the H-WTRU to "E-UTRA RRC HELPER" state. The "ENTER HELPER MODE" command may provide a group radio network temporary identifier (RNTI) that will be used for transmissions related to helper functionality. If an active H- WTRU decides to exit "E-UTRA RRC HELPER" state, the WTRU may send a request to an eNB to exit the helper mode. The eNB may respond with an "EXIT HELPER MODE" command that may transition the WTRU to a traditional "RRC CONNECTED" mode. The eNB may also decide to put the WTRU in "RRC IDLE" mode by releasing the existing connection to the WTRU.

[0078] FIG. 9 shows an example of a WTRU RRC state machine 900 including a new "E-UTRA RRC_HELPER_STATE" 902. The states shown in the WTRU RRC state machine 900 are "E-UTRA RRC_HELPER_STATE" 902, "E- UTRA RRC_CONNECTED" 904, and "E-UTRA RRCJDLE" 906. To transition from "E-UTRA RRC_CONNECTED" 904 to "E-UTRA RRC_HELPER_STATE" 902, an "ENTER HELPER MODE" command 910 may be used. To transition from "E-UTRA RRC_HELPER_STATE" 902 to "E-UTRA RRC_CONNECTED" 904, an "EXIT HELPER MODE" command 912 may be used. To transition from "E-UTRA RRC_HELPER_STATE" 902 to "E-UTRA RRCJDLE" 906, a "CONNECTION RELEASE" command 914 may be used. To transition from "E- UTRA RRC_CONNECTED" 904 to "E-UTRA RRC JDLE" 906, a "CONNECTION RELEASE" command 916 may be used. To transition from "E-UTRA RRCJDLE" 906 to "E-UTRA RRC_CONNECTED" 904, a "CONNECTION ESTABLISHMENT" command 918 may be used. The states and commands described above are for exemplary purposes only. The names provided for the states and commands are examples and any name may be used. Any combination of the states and commands described above may be used.

[0079] To perform the WTRU cooperation described herein, resources may be allocated in a variety of ways. Resource partitioning may affect other aspects of a system, including for example, hardware capability requirements of a T- WTRU or H-WTRU, interference between TRLs and XLs and/or XLs and other XLs, HARQ design, or latency. The following examples show a variety of ways to perform resource partitioning including the available resource partitioning dimensions and resource partitioning options using the dimensions.

[0080] Table 1 shows an example categorization of the various relay configurations using resource partitioning and/or duplexing dimensions. XL in the same band as TRL (ln-band) XL in a different band from

TRL iOut bandl

Resource Duplexing► FDD TDD FDD TDD

Partitioning

(XL/TRL)

T

Frequency Case A: FIG. 10A (XL on Case B: Case E (reuse Case F

'reserved' subcarriers; FIG. 1 1A among multiple

reuse among multiple XLs)

XLs) Case B':

FIG. 1 1 B

Case A': FIG. 10B (Underlay)

(Underlay of XL on tones

used by TRL)

Time Case C: FIG. 12 (XL on Case D

'reserved' TTIs; reuse

among multiple XLs)

Table 1

[0081] Spectrum partitioning may be used for a XL between a H-WTRU and a T-WTRU. The separation of the spectrum may be classified as "in-band" and "out-band." For the in-band, the TRL may share the same band and potentially the same carrier frequency as the XL. The in-band TRL-XL partitioning may also be categorized as follows. The XL may use a set of statically or dynamically reserved frequency resources. For example, the resources may not be allocated to the TRL at the same time. The resources may also be used for one or more XLs within a network (for example, Case A or Case B in Table 1). The XL may share frequency resources with a TRL. For example, the TRL transmission in the shared resources may be to or from other WTRUs (for example, Case A' or Case B' in Table 1) or to or from the T-WTRU. For the out- band separation, the XL may not operate in the same band as the TRL.

[0082] Duplexing may also be used for WTRU cooperation. Duplexing may occur on the downlink and uplink and on the TRL and the XL. For example, frequency division duplexing (FDD) or time division duplexing (TDD) may be used. At a particular time, either FDD or TDD may be used for the active TRLs and XLs. [0083] Using the resource dimensions described above, several options exist for resource portioning for WTRU relays. For example, frequency domain multiplexing may be used for the XL. If the XL may utilize frequency resources from the same channel as the TRL, any of the following options may be used.

[0084] As used herein, the term "underlay case" may be used to describe XL resources being reused for the TRL. Any resource partitioning scheme may decide whether DL or UL resources are used for the XL. If DL resources are used for the XL, there may be interference between the DL TRL and the XL. The interference may be detrimental to a T-WTRU, H-WTRU, and/or O-WTRU. If UL resources are used for the XL, there may be interference between the UL TRL and the XL. The interference may be detrimental to a T-WTRU, H-WTRU, and/or eNB. A DL XL may use resources from the DL band and an UL XL may use resources from the UL band. If a DL XL uses UL band resources or an UL XL uses DL band resources, it may interfere with any design that allows a T- WTRU to receive from an eNB and a H-WTRU simultaneously.

[0085] FIGs. 10A-B show frequency division multiplexing (FDM) in FDD scenarios 1000, 1050. FIG. 10A shows a scenario 1000 with frequency division between the TRL and the XL. FIG. 10A may include Case A as shown in Table 1. FIG. 10B shows a scenario 1050 with XL resources being reused for the TRL. FIG. 10B may include Case A' as shown in Table 1. Referring to FIG. 10A, a resource partitioning scheme 1000 is shown that includes an eNB 1002, a T- WTRU 1004, a H-WTRU 1006, and an O-WTRU 1008. In the DL direction, the eNB 1002 may transmit information on f _d i 1010 to the T-WTRU 1004 during a first transmission time interval (TTI) t or a second TTI t'. The eNB 1002 may also transmit information on f _d i 1012 to the H-WTRU 1006 during TTI t. The eNB 1002 may transmit information on f _d3 1014 to the O-WTRU 1008 during TTI t or TTI t'. As used herein, fdi, fd2, and fd3 may be TRL resources or any other physical resources. The H-WTRU 1006 may transmit the information on fd2 1016 to the T-WTRU 1004 during TTI t'. If the eNB 1002 transmits to the T-WTRU 1004 and O-WTRU 1008 during TTT t, the TRL and XL transmissions may be time-separated. For the UL direction, a similar partitioning strategy may be used. The T-WTRU 1004 may transmit information on f _u i 1020 to the eNB 1002 during the first TTI t or the second TTI t'. The H-WTRU 1006 may also transmit information on f _u i 1022 to the eNB 1002 during TTI t. The O-WTRU 1008 may transmit information on f _u3 1024 to the eNB 1002 during TTI t or TTI t'. As used herein, f _u i and f _U 3 may be TRL resources. The T-WTRU 1004 may transmit the information on f _u2 1026 to the H-WTRU 1006 during TTI t'. If the T-WTRU 1004 and O-WTRU 1008 transmit to the eNB 1002 during TTT t, the TRL and XL transmissions may be time- separated.

[0086] FIG. 10A may also include Case E as shown in Table 1. In this example, the XL is in a different band than the TRL, which may be referred to as "out-band." This example may use FDM in FDD. Some or all of the transmissions described above may remain the same for this example. For Case E, the frequency resources may be in different bands. For example, fdi and fd2, as described above, may be in different bands.

[0087] Referring to FIG. 10B, a resource partitioning scheme 1050 is shown that includes the eNB 1002, the T-WTRU 1004, the H-WTRU 1006, and the O- WTRU 1008. In the DL direction, the eNB 1002 may transmit information on fdi 1060 to the T-WTRU 1004 during a first TTI t. The eNB 1002 may transmit information on f _d i 1062 to the H-WTRU 1006 during TTI t. The eNB 1002 may transmit information on f _d2 1064 to the O-WTRU 1008 during TTI t or second TTI t'. The H-WTRU 1006 may transmit the information on f _d2 1066 to the T-WTRU 1004 during TTI t'. For the UL direction, a similar partitioning strategy may be used. The T-WTRU 1004 may transmit information on f _u i 1070 to the eNB 1002 during TTI t. The H-WTRU 1006 may also transmit information on f _u i 1072 to the eNB 1002 during TTI t. The O-WTRU 1008 may transmit information on f _u2 1074 to the eNB 1002 during TTI t or TTI t'. The T-WTRU 1004 may transmit the information on f _u2 1076 to the H-WTRU 1006 during TTI t'. In this example, resources for the O-WTRU 1008 may overlap with the resources for the H-WTRU 1004.

[0088] In an FDM XL design, the XL subcarriers may be in the same channel as the TRL or in an adjacent channel. Performance degradation in either the TRL or the XL may occur due to received power imbalance between the TRL and the XL. A single receiver may be used, whereby the T-WTRU may consider the TRL and the XL as part of same channel and/or carrier. The T- WTRU may perform composite Fast Fourier Transform (FFT) receiver processing. To service the additional dynamic range due to the imbalance described above, more fidelity in the A/D converter may be required. Alternatively or additionally, a dual receiver design may be used if the resources for the TRL and the XL are adjacently located, but not interleaved. If there is a large imbalance between the TRL and the XL, separate Automatic Gain Control (AGC) setpoints may be enabled for the two receivers.

[0089] FIGs. 11A-B show FDM in TDD scenarios 1100, 1150. FIG. 11A shows a scenario 1100 in which the TRL and the XL may be scheduled over non- overlapping subscarriers. FIG. 11A may include Case B as shown in Table 1. FIG. 11B shows a scenario 1150 in which the XL may use the same time- frequency resources as the link between the eNB and the O-WTRU, which is also an example of the "underlay case." FIG. 11B may include Case B' as shown in Table 1. Referring to FIG. 11 A, a resource partitioning scheme 1100 is shown that includes an eNB 1102, a T-WTRU 1104, a H-WTRU 1106, and an O-WTRU 1108. The TRL and the XL may be scheduled over non-overlapping subcarriers f 1 and f2, respectively. The TRL and the XL may also be time- separated. O-WTRU 1108 transmissions may co-exist in the same TTI as the XL. In the DL direction, the eNB 1102 may transmit information on fi 1110 to the T-WTRU 1104 during TTI td. The eNB 1102 may also transmit information on fi 1112 to the H-WTRU 1106 during TTI t _d . The eNB 1102 may transmit information on f ₃ 1114 to the O- WTRU 1108 during TTI t _d or TTI t _d ', where t _d may come before td'. The H-WTRU 1106 may transmit the information on f ₂ 1116 to the T-WTRU 1104 during TTI td'. For the UL direction, a similar partitioning strategy may be used. The T- WTRU 1104 may transmit information on fi 1120 to the eNB 1102 during TTI t _u . The H-WTRU 1106 may also transmit information on fi 1122 to the eNB 1102 during TTI t _u . The O-WTRU 1108 may transmit information on f ₃ 1124 to the eNB 1102 during first TTI t _u or second TTI t _u '. The T-WTRU 1104 may transmit the information on f ₂ 1126 to the H-WTRU 1106 during TTI t _u '.

[0090] FIG. 11A may also include Case F as shown in Table 1. In this example, the XL is in a different band than the TRL, which may be referred to as "out-band." This example may use FDM in TDD. Some or all of the transmissions described above may remain the same for this example. For Case F, the frequency resources may be in different bands. For example, fi and f ₂ , as described above, may be in different bands.

[0091] Referring to FIG. 11B, a resource partitioning scheme 1150 is shown that includes the eNB 1102, the T-WTRU 1104, the H-WTRU 1106, and the O- WTRU 1108. The XL may use the same time-frequency resources as the eNB 1102 to O-WTRU 1108 link. In the DL direction, the eNB 1102 may transmit information on fi 1160 to the T-WTRU 1104 during TTI t _d . The eNB 1102 may also transmit information on fi 1162 to the H-WTRU 1106 during TTI td. The eNB 1102 may transmit information on f ₂ 1164 to the O-WTRU 1108 during TTI td or TTI td', where td may come before td'. The H-WTRU 1106 may transmit the information on f ₂ 1166 to the T-WTRU 1104 during TTI td'. For the UL direction, a similar partitioning strategy may be used. The T-WTRU 1104 may transmit information on fi 1170 to the eNB 1102 during TTI t _u . The H-WTRU 1106 may also transmit information on fi 1172 to the eNB 1102 during TTI t _u . The O- WTRU 1108 may transmit information on f ₂ 1174 to the eNB 1102 during first TTI t _u or second TTI t _u '. The T-WTRU 1104 may transmit the information on f ₂ 1176 to the H-WTRU 1106 during TTI t _u '.

[0092] Time domain multiplexing (TDM) may also be used for the XL. The

XL may have dedicated time slots during which one or more subcarriers may be used for XL transmissions. The TDM as used herein may refer to TDM with respect to the TRL transmissions to or from all WTRUs in a network and may be distinct from the first and second hops described herein.

[0093] FIG. 12 shows an example of TDM resource allocation using FDD

1200 that includes an eNB 1202, a T-WTRU 1204, a H-WTRU 1206, and an O- WTRU 1208. FIG. 12 may include Case C as shown in Table 1. In the DL direction, the eNB 1202 may transmit information on fdi 1210 to the T-WTRU 1204 during time t, where time t may represent time slots allocated for TRL transmissions and another time, t , may represent time slots allocated for XL transmissions. Times t and t may be mutually exclusive. During time t , the eNB 1202 may not transmit to the T-WTRU 1204. The eNB 1202 may transmit information on f _d i 1212 to the H-WTRU 1206 during time t. The eNB 1202 may transmit information on f<j2 1214 to the O-WTRU 1208 during time t and/or may not transmit during time t . The H-WTRU 1206 may transmit the information on fdi and/or f _d2 1216 to the T-WTRU 1204 during time t . For the UL direction, a similar strategy may be used. The T-WTRU 1204 may transmit information on fui 1220 to the eNB 1202 during time t and/or may not transmit during time t . The H-WTRU 1206 may also transmit information on f _u i 1022 to the eNB 1202 during time t. The O-WTRU 1208 may transmit information on f _U 2 1224 to the eNB 1202 during time t and/or may not transmit during time t . The T-WTRU 1204 may transmit the information on f _ui and/or f _u2 1226 to the H-WTRU 1206 during time t . FIG. 12 may also include Case D as shown in Table 1. For example, TDD may be used and the TRL and XL may be time-division multiplexed. The communications may be assigned DL, UL, and XL time slots.

[0094] Subframe or symbol level TDM may be used for WTRU cooperation.

In the PHY structure, each millisecond subframe may be divided into two slots, each of which may include one or more OFDM symbols. The TDM partitioning may occur at many levels, for example, the subframe level, slot level, or the symbol level. For example, TDD partitioning between the uplink and downlink may occur at the subframe level for a type-1 PHY frame structure. TDM partitioning for the XL may also occur at the subframe level for a type-1 PHY frame structure, whereby certain subframes may be reserved for the crosslink. The eNB may not transmit any data in the subframe, but may still transmit broadcast and control signals.

[0095] For the downlink, symbol level partitioning may consider the presence of broadcast and control signaling in some of the symbols. If the broadcast and control signaling is blanked out, it may have a negative impact on legacy WTRUs. Similarly, on the uplink, the PUCCH for a single user may be transmitted over an entire subframe (for example, 2 slots) and/or over all the symbols in the subframe. The PUCCH resources may be concentrated at either edge of the operational bandwidth (BW) and may not be used for the XL. A symbol level TDM approach may not grant entire OFDM symbols to the XL and a symbol TDM approach may involve a frequency division in which a subset of the frequency resources may be available for the XL.

[0096] Time alignment may also be used for the XL. The XLs may be short distance links and they may be, for example, limited to less than 200m. This is shown, for example, in simulations using reasonable assumptions in the helper selection algorithm. At the distances described above, the propagation delays may be restricted to less than a μββο, which may be significantly less than the cyclic prefix length of about 5 μ sec.

[0097] The alignment of the frame boundary for the XL is also considered.

If the TRL and XL may be received separately, for example, either separated in the time domain or separated due to widely separated channels (for example, in different bands), then the receiver may treat the timing for the two links as independent of each other. This technique may be used both DL and UL XL transmissions. If the TRL and XL subcarriers are adjacent or interleaved in the same carrier, the T-WTRU may receive both the TRL and XL on the DL in the same TTI. One or more of the time alignments described below may accommodate this scenario. Similarly, on the UL, if the T-WTRU is required to transmit to both the H-WTRU and the eNB simultaneously, one or more of the following timing solutions may be used for the H-WTRU receiver.

[0098] Downlink time alignment may be performed according to any of the following timing schemes. A timing scheme for a H-WTRU XL transmitter may be used to allow the DL XL to be received and decoded by the T-WTRU simultaneously with the DL TRL. This may occur if the T-WTRU is required to receive control and data from the eNB on the TRL while also receiving separate data on the XL. [0099] Figure 13 shows an example of DL time alignment 1300 for simultaneous TRL and XL reception in the same carrier. The propagation delay 1310 is shown for an H-WTRU 1312, an eNB 1314, and a T-WTRU 1316. The H- WTRU 1312 may realize a propagation delay of Tl from the eNB 1314. The T- WTRU 1316 may realize a propagation delay of T2 from the eNB 1314. The delay between the H-WTRU 1312 and T-WTRU 1316 may be T3. It may be assumed that the maximum delay on the crosslink (max (T3)) and the maximum difference between the delays Tl and T2 (ΔΤ = max( | T1-T2 | )) are known parameters. A helper assignment algorithm may be configured to ensure these conditions. One or more of the parameters described above may be signaled system-wide for use by any prospective H-WTRU 1312.

[0100] Referring to FIG. 13, the eNB's transmit frame boundary 1330 may be denoted as 't.' The H-WTRU 1312 may receive the TRL 1332 from the eNB 1314 at t + Tl. This may be considered the reception subframe at the H-WTRU 1312. The H-WTRU 1312 may derive its timing based on (t + Tl). For the XL transmission, the H-WTRU 1312 may transmit 1340 with frame boundary t + Tl + AT. By transmitting at this frame boundary, the T-WTRU 1316 may see the XL channel arrive 1344 at (t + Tl + AT + T3), which may be considered a reception subframe at the T-WTRU 1316. This may be a positive delay with respect to the TRL receive frame boundary 1346 of (t + T2) received from the eNB 1314. This may be considered a reception subframe at the T-WTRU 1316. This additional delay in the XL may be absorbed, for example, due to the length of a cyclic prefix budget 1348.

[0101] Uplink time alignment may be performed according to any of the following timing schemes. A timing scheme for a H-WTRU may be used to allow the UL XL to be received and decoded. The timing schemes described herein may be similar to one or more of the downlink timing schemes described above. Any combination of the timing schemes described herein may be used. The T-WTRU may transmit to both the eNB on the TRL and the H-WTRU on the XL. This may result in a scenario in which a WTRU may need to transmit control information and/or data to the eNB and transmit the first hop of the UL transmission to the H-WTRU on the XL. These transmissions may need to occur at the same time.

[0102] In UL direction, WTRUs may advance their transmit frame timing using a timing advance (TA) value equivalent or approximately equivalent to the propagation delay to the eNB. This may allow the eNB to receive the UL transmissions from some or all of the WTRUs within a cyclic prefix window. FIG. 14 shows an example of time alignment 1400 at a H-WTRU for XL reception. The propagation delay 1410 is shown for an H-WTRU 1412, an eNB 1414, and a T-WTRU 1416. The propagation delay between the H-WTRU 1412 and the eNB 1414 may be Tl. The propagation delay between the T-WTRU 1416 and the eNB 1414 may be T2. The propagation delay between the H-WTRU 1412 and T- WTRU 1416 may be T3.

[0103] Referring to FIG. 14, the H-WTRU 1412 timing advance may be TAl

= Tl. The T-WTRU 1416 timing advance may be TA2 = T2. The T-WTRU 1416 may also transmit on the UL XL using the same timing as the UL TRL. For example, the UL XL may use a TA of TA2. The H-WTRU 1412 receiver may be responsible for using appropriate receive frame timing. The H-WTRU 1412 may control its XL receiver timing based on the H-WTRU 1412 UL TRL timing advance. The H-WTRU 1412 may use a receive boundary 1420 that is advanced by AT = max( | T1-T2 | ) from its transmit frame boundary 1422. The H-WTRU 1412 may be configured with the parameter AT by the eNB 1414. This parameter may also be the value required for the DL timing alignment discussed above. The H-WTRU 1412 may have the UL XL channel fall within its cyclic prefix delay budget. FIG. 14 also shows the channel delay spread realized by the H-WTRU on the XL 1424, the T-WTRU 1416 UL TRL transmit frame boundary 1426, and the eNB 1412 UL receive frame boundary 1428. In each of the DL and UL timing schemes described herein, there may be loss in the overall cyclic prefix budget of the cell due to, for example, the backoff requirement AT.

[0104] Mobility handling and helper set maintenance may be used as part of a WTRU cooperation scheme. T- WTRUs and/or eNBs may need to be able to identify potential H-WTRUs in a timely manner. The T- WTRUs and/or eNBs may also need to be able to refresh the set of available H-WTRUs periodically based on, for example, measurements and other factors. Neighbor discovery may be used to identify potential H-WTRUs. Neighbor discovery may be performed at power up or as a response to specific events, such as, for example, one or more H- WTRUs no longer being available. The result of neighbor discovery may be a set of candidate H-WTRUs for each T-WTRU. From the candidate set, a subset of H- WTRUs may form the Helper Active Set (HAS). Members of the HAS may be available to help the T-WTRU instantaneously and in every TTI. Fast dynamic switching between H-WTRUs may therefore be possible.

[0105] FIG. 15 shows an example of the H-WTRU discovery and selection process 1500. Different levels and grouping of WTRUs may be used to support neighbor discovery and mobility. A Candidate Set 1510 and a HAS 1520 may be maintained for each WTRU. The Candidate Set 1510 may be a collection of WTRUs that are suitable H-WTRUs. The Candidate Set 1510 may be a subset of the WTRUs identified during a neighbor discovery 1530 process. A Proximity Group 1540 may be determined at the beginning of a neighbor discovery 1530 process. The Proximity Group 1540 may be updated via a neighbor update if there is a need to update neighbors or may be updated periodically. A neighbor update may be configured and coordinated by a network. WTRUs in the Proximity Group 1540 may be "attached" WTRUs and/or registered WTRUs. These WTRUs may or may not be in "RRC_CONNECTED" mode. A suitability index 1542 may be used to determine whether a WTRU may transition from the Proximity Group 1540 to the Candidate Set 1510. Advanced topology (AT) events 1542 may also be used to trigger neighbor discovery. For example, an AT- neighbor seeking user equipment (AT-NSUE) event may be used to indicate that a neighbor WTRU is seeking a helper or initiating neighbor discovery and/or an AT- neighbor present user equipment (AT-NPUE) event may be used to indicate that a neighbor WTRU is present.

[0106] If a neighbor set is determined from the Proximity Group 1540,

WTRUs in the neighbor set may be requested to send information that may be indicative of their availability as a H-WTRU, such as, for example, TRL conditions, capability information, their battery status, user subscription level, and the like. These WTRUs may be ranked based on a suitability index derived from a variety of factors, including any of the factors described above. The suitability index may be derived from a combination of real-time data including XL conditions, TRL conditions, battery status, hardware limitations, user subscription level, willingness to help another WTRU, and the like. The realtime data may be derived from the information provided by each WTRU.

[0107] If the Candidate Set 1510 is determined, WTRUs in the candidate set may transition to "RRC_CONNECTED" mode. This may allow the eNB to be aware of the mobility of WTRUs in the Candidate Set 1510. WTRUs in the Candidate Set 1510 may be in discontinuous reception (DRX) mode and may measure both the TRL and the XL. Periodic measurements may be configured for WTRUs in the Candidate Set 1510 to obtain TRL conditions, XL conditions, and the like. WTRUs in the Candidate Set 1510 may be configured with DRX to conserve WTRU battery. Measurement periods may be configured to coordinate with the DRX cycle for WTRUs in the Candidate Set 1510.

[0108] A subset of WTRUs from the Candidate Set 1510 may be selected to the HAS 1520. The selection may be based on, for example, measurements and other information that is part of the suitability index. The HAS 1520 may be established at the beginning of connection with a T-WTRU and may be maintained throughout the life of a connection. The HAS 1520 may be updated, for example, based on an event or periodically throughout the life of the connection. WTRUs that are in the HAS 1520 are configured to be in RRC_HELPER_STATE. WTRUs in the HAS 1520 may be in DRX. The eNB may configure the WTRUs in the HAS 1520 to report measurements differently than WTRUs in the Candidate Set 1510. For example, WTRUs in the HAS 1520 may report measurements more frequently and may report more measurement events compared to WTRUs in the Candidate Set 1510.

[0109] As shown in FIG. 15, measurement events Event AT-1 1512, Event

AT-2 1514, and Event AT-3 1516 provide examples of WTRU transition into and out of the Candidate Set 1510 and the HAS 1520. For example, Event AT-1 1512 shows WTRU "x" transitioning from the Candidate Set 1510 to the HAS 1520. The transition may occur, for example, because WTRU "x" is a Candidate Set 1510 WTRU that exceeds the threshold for becoming a member of the HAS 1520. Event AT-2 1514 shows WTRU "y" transitioning out of the Candidate Set 1510. The transition may occur, for example, because WTRU "y" is below a threshold required to remain in the Candidate Set 1510. Event AT-3 1516 shows WTRU "z" transitioning from the HAS 1520 to the Candidate Set 1510. This transition may occur, for example, because WTRU "z" is a HAS 1520 WTRU that has fallen below the threshold required to be in the HAS 1520.

[0110] HAS 1520 and Candidate Set 1510 selection and maintenance may not involve the Evolved Packet Core (EPC). The eNB may be involved in this procedure. If a connection to the T-WTRU is formed, there may be at least one WTRU in the HAS 1520. The eNB may provide an indication to the T-WTRU that includes all WTRUs that may be included in the HAS 1520 and Candidate Set 1510. The T-WTRU may be required to measure and report on each of these WTRUs.

[0111] A WTRU in the HAS 1520 may be selected as an "active" H- WTRU

1550. An active H-WTRU 1550 is an H-WTRU actively assisting a T-WTRU. The transition to active H-WTRU 1550 may occur dynamically 1552, for example, at the TTI level. The transition may also be driven by measurement reports. An active H-WTRU 1550 may be in an "RRC_HELPER_STATE" state. An active H- WTRU 1550 may not be in a DRX state. A T-WTRU may be informed as to which H-WTRU from the HAS 1520 is the active H-WTRU 1550. The T-WTRU may be being provided the identity of a specific H-WTRU and scheduling information via PHY signaling.

[0112] Embodiments:

1. A method for downlink wireless transmit/receive unit (WTRU) cooperation, the method comprising:

a helper WTRU receiving a downlink transmission from a Node-B; and the helper WTRU forwarding the downlink transmission to an associated WTRU. 2. The method of embodiment 1, wherein WTRUs are grouped in a particular group.

3. The method of embodiment 2, wherein the WTRUs belongs to one of N groups, N being a positive integer greater than one.

4. The method as in any one of embodiments 1-3, wherein the helper WTRU receives the downlink transmission from the Node-B via a radio resource reserved for a channel between the helper WTRU and the Node-B.

5. The method as in any one of embodiments 1-4, wherein the helper WTRU forwards the downlink transmission to the associated WTRU via a radio resource reserved for a crosslink between the helper WTRU and the associated WTRU.

6. The method of embodiment 5, wherein a first radio link (RL) phase during which a downlink transmission is transmitted from the Node-B to a first group of WTRUs and a second RL phase during which a downlink transmission is transmitted from the Node-B to a second group of WTRUs alternate.

7. The method as in any one of embodiments 5-6, wherein a first radio link (RL) phase during which a downlink transmission is transmitted from the Node-B to a first group of WTRUs and a second crosslink phase during which a downlink transmission is forwarded to an associated WTRU in a second group overlap, and a second RL phase during which a downlink transmission is transmitted from the Node-B to a second group of WTRUs and a first crosslink phase during which a downlink transmission is forwarded to an associated WTRU in a first group overlap.

8. The method as in any one of embodiments 5-7, wherein the radio resource for the crosslink is reused in a sector or a cell.

9. The method as in any one of embodiments 7-8, wherein during the first RL phase and the second RL phase, WTRUs are scheduled with one of a round-robin scheduler, proportionally fair scheduler, a fair throughput scheduler, or a maximum carrier-to-interference ratio (C/I) scheduler. 10. The method as in any one of embodiments 2-9, wherein the WTRUs are grouped randomly.

11. The method as in any one of embodiments 2-9, wherein a WTRU is put into a group where a minimum distance between WTRUs is highest among groups.

12. The method as in any one of embodiments 1-11, wherein the helper WTRU is selected for the associated WTRU on a condition that the associated WTRU has less than a predetermined number of helper WTRUs already associated.

13. The method as in any one of embodiments 1-12, wherein the helper WTRU is selected for the associated WTRU on a condition that the helper WTRU is within a predetermined distance of the associated WTRU.

14. The method as in any one of embodiments 1-13, wherein the helper WTRU is selected for the associated WTRU on a condition that the helper WTRU radio link received power from the Node-B divided by the associated WTRU radio link received power from the Node-B is greater than a predetermined ratio.

15. A method for downlink wireless transmit/receive unit (WTRU) cooperation, the method comprising:

a WTRU receiving a downlink transmission from a helper WTRU via a crosslink.

16. The method of embodiment 15 wherein the WTRU receives the downlink transmission from the helper WTRU via a radio resource reserved for a crosslink between the helper WTRU and the WTRU.

17. The method as in any one of embodiments 15-16, wherein a first radio link (RL) phase during which a downlink transmission is transmitted from the Node-B to a first group of WTRUs and a second RL phase during which a downlink transmission is transmitted from the Node-B to a second group of WTRUs alternate.

18. The method as in any one of embodiments 15-17, wherein a first radio link (RL) phase during which a downlink transmission is transmitted from the Node-B to a first group of WTRUs and a second crosslink phase during which a downlink transmission is forwarded to an associated WTRU in a second group overlap, and a second RL phase during which a downlink transmission is transmitted from the Node-B to a second group of WTRUs and a first crosslink phase during which a downlink transmission is forwarded to an associated WTRU in a first group overlap.

19. The method as in any one of embodiments 15-18, wherein the radio resource for the crosslink is reused in a sector or a cell.

20. The method as in any one of embodiments 15-19, wherein WTRUs are grouped randomly.

21. The method as in any one of embodiments 15-19, wherein a WTRU is put into a group where a minimum distance between WTRUs is highest among groups.

22. The method as in any one of embodiments 15-21, wherein the helper WTRU is selected for the WTRU on a condition that the WTRU has less than a predetermined number of helper WTRUs already associated.

23. The method as in any one of embodiments 15-22, wherein the helper WTRU is selected for the WTRU on a condition that the helper WTRU is within a predetermined distance of the WTRU.

24. The method as in any one of embodiments 15-23, wherein the helper WTRU is selected for the WTRU on a condition that the helper WTRU radio link received power from the Node-B divided by the WTRU radio link received power from the Node-B is greater than a predetermined ratio.

25. A method for use in a first wireless transmit/receive unit (WTRU) associated with a Long Term Evolution (LTE) evolved NodeB (eNB), the method comprising:

receiving a first transmission from the eNB, wherein the first transmission includes user data.

26. The method as in any one of the preceding embodiments, further comprising:

receiving a second transmission from a helper WTRU (H-WTRU), wherein the second transmission includes the user data. 27. The method as in any one of the preceding embodiments, wherein control information associated with the first and second transmissions is received from the eNB.

28. The method as in any one of the preceding embodiments, wherein the first transmission is received during a first time period and the second transmission is received during a second time period.

29. The method as in any one of the preceding embodiments, wherein the first transmission and the second transmission are received during a same time period.

30. The method as in any one of the preceding embodiments, further comprising:

receiving a re-transmission of the second transmission from the H-WTRU on a condition that the first transmission and the second transmission were not received.

31. The method as in any one of the preceding embodiments, further comprising:

receiving a third transmission from the eNB, wherein the third transmission includes the user data.

32. The method as in any one of the preceding embodiments, wherein the first transmission is received over a first Physical Downlink Shared Channel (PDSCH) and the second transmission is received over a second PDSCH.

33. The method as in any one of the preceding embodiments, wherein a first Dedicated Traffic Channel (DTCH) is mapped to the first PDSCH and a second DTCH is mapped to the second PDSCH.

34. The method as in any one of the preceding embodiments, wherein the first WTRU receives first logical channel data from the eNB over the first PDSCH and second logical channel data from the H-WTRU over the second PDSCH.

35. The method as in any one of the preceding embodiments, wherein the first transmission and the second transmission share frequency resources. 36. The method as in any one of the preceding embodiments, wherein the first transmission and the second transmission are scheduled over non- overlapping subcarriers.

37. A method for use in a helper wireless transmit/receive unit (H- WTRU) associated with a Long Term Evolution (LTE) evolved NodeB (eNB), the method comprising:

receiving a first transmission from the eNB, wherein the transmission includes user data.

38. The method as in any one of the preceding embodiments, further comprising:

transmitting a second transmission to a terminal WTRU (T-WTRU), wherein the second transmission includes the user data.

39. The method as in any one of the preceding embodiments, wherein control information associated with the user data is transmitted from the eNB to the T-WTRU.

40. The method as in any one of the preceding embodiments, wherein the transmitting of the second transmission is performed on a condition that the H-WTRU is in an RRC_HELPER_STATE state.

41. The method as in any one of the preceding embodiments, further comprising performing decode-forward

and acknowledgement functions.

42. The method as in any one of the preceding embodiments, wherein the performing decode-forward

and acknowledgement functions is done by a Hybrid Automatic Repeat Request (HARQ) entity.

43. The method as in any one of the preceding embodiments, further comprising:

receiving user plane signaling from the eNB and T-WTRU; and transmitting user plane signaling to the eNB and T-WTRU.

44. The method as in any one of the preceding embodiments, further comprising: receiving at least one timing parameter, each of the at least one timing parameters indicating a propagation delay of transmissions from the eNB; and transmitting the second transmission at a predetermined time based on the at least one timing parameter.

45. The method as in any one of the preceding embodiments, further comprising:

re-transmitting the second transmission to the T-WTRU on a condition that the T-WTRU did not receive the second transmission.

46. The method as in any one of the preceding embodiments, further comprising:

transmitting to a T-WTRU on a first hop.

47. The method as in any one of the preceding embodiments, further comprising:

transmitting to a T-WTRU on a second hop.

48. The method as in any one of the preceding embodiments, further comprising:

instantiating a first PDSCH and a second PDSCH, wherein the first PDSCH carries data from an eNB and the second PDSCH carries data from a H- WTRU.

49. The method as in any one of the preceding embodiments, further comprising:

instantiating a first Physical Uplink Shared Channel (PUSCH) and a second PUSCH, wherein the first PUSCH carries data to an eNB and the second PDSCH carries data to a H-WTRU.

50. The method as in any one of the preceding embodiments, further comprising:

duplexing communications by time or frequency and partitioning resources by time or frequency.

51. The method as in any one of the preceding embodiments, further comprising:

performing time division multiplexing at a subframe or symbol level. 52. A method for use in a first wireless transmit/receive unit (WTRU) associated with a Long Term Evolution (LTE) evolved NodeB (eNB), the method comprising:

receiving a first transmission from the eNB, wherein the first transmission includes user data; and

receiving a second transmission from a helper WTRU (H-WTRU), wherein the second transmission includes the user data;

wherein control information associated with the first and second transmissions is received from the eNB.

53. A method for use in a helper wireless transmit/receive unit (H- WTRU) associated with a Long Term Evolution (LTE) evolved NodeB (eNB), the method comprising:

receiving a first transmission from the eNB, wherein the transmission includes user data; and

transmitting a second transmission to a terminal WTRU (T-WTRU), wherein the second transmission includes the user data;

wherein control information associated with the user data is transmitted from the eNB to the T-WTRU.

54. A wireless transmit/receive unit (WTRU) configured to perform a method as in any one of embodiments 1-53.

55. An apparatus configured to perform a method as in any one of embodiments 1-53.

56. A system configured to perform a method as in any one of embodiments 1-53.

57. An integrated circuit configured to perform a method as in any one of embodiments 1-53.

58. An evolved Node B (eNB) configured to perform a method as in any one of embodiments 1-53.

[0113] 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.

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