WO2011119750A1 - Method, apparatus and system for enabling resource coordination in cellular networks - Google Patents

Abstract

A method, apparatus and system for coordinating scheduling of resources among different cells in a wireless network are disclosed. A base station receives a notification or indication from a wireless transmit/receive unit (WTRU) associated with the base station that interference was detected or is suspected. The base station transmits a coordination message to another base station associated with the interference that was detected or is suspected. The coordination message includes resource scheduling information for the WTRU associated with the base station.

Description

Method, Apparatus and System for Enabling Resource Coordination in Cellular Networks

CROSS REFERENCE TO RELATED APPLICATIONS

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

Application No. 61/316,556, filed March 23, 2010, the contents of which is hereby incorporated by reference herein.

BACKGROUND

[0002] Base stations in a given cellular network are generally uncoordinated in that they schedule communications on any available resource without regard to the resources in use by other cells in the network. When adjacent cells schedule communications on overlapping resources, this may cause interference among them. Such inter cell interference (ICI) may inhibit uniform performance and high throughput at cell edge.

[0003] ICI may be higher in heterogeneous networks than in homogenous networks. For example, in a heterogeneous network, a micro node may have significantly lower transmit power than a macro node, and some macro wireless transmit/receive units (WTRUs) near the edge of a micro cell maybe closer to the micro node than to the macro node serving the macro WTRU. As a result, in the uplink, the macro WTRU near the edge of the micro cell may cause high interference with the micro cell due to small path loss. Further, if the micro cell provides service to a closed subscriber group (CSG), the interference may be even higher because a WTRU not belonging to the CSG communicates with the macro node even if it is located in the center of the micro cell.

SUMMARY

[0004] A method, apparatus and system for coordinating scheduling of resources among different cells in a wireless network are disclosed. In an embodiment, a base station receives a notification or an indication (such as

-1-

1547351-1 channel quality) from a wireless transmit/receive unit (WTRU) associated with the base station that interference was detected or is suspected. The base station transmits a coordination message to at least one other base station associated with the interference that was detected or suspected. The coordination message includes resource scheduling information for the WTRU associated with the base station.

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 is an example flow diagram of a method of coordinating scheduling of resources among different cells in a wireless network;

[0010] FIG. 3A is an example signal diagram illustrating more detailed signaling that may be used to coordinate scheduling of resources among different cells in a wireless network;

[0011] FIG. 3B is another signal diagram illustrating more detailed signaling that may be used to coordinate scheduling of resources among different cells in a wireless network;

[0012] FIG. 4 is a diagram illustrating an example of uncoordinated resource scheduling across two cells;

-2-

1547351-1 [0013] FIG. 5 is a diagram illustrating an example coordinated scheduling pattern that may be used when base stations are aware of each other's scheduling patterns;

[0014] FIG. 6 is a diagram illustrating an example coordinated scheduling pattern that may be used when base stations jointly reach a scheduling agreement;

[0015] FIG. 7 is a diagram of an example two user interfering channel illustrating an interference cancellation method;

[0016] FIG. 8 is a diagram illustrating an example operation of a successive interference cancellation (SIC) method in the uplink; and

[0017] FIG. 9 is an example flow diagram of a method of performing SIC with coordinated resource scheduling.

DETAILED DESCRIPTION

[0018] When multiple scheduling units do not share each other's resource allocation patterns and/or do not coordinate resource scheduling with each other, a receiving node may suffer interference from an arbitrary number of sources on each of the resources the receiving node is scheduled on. This may affect the accuracy of channel quality indicators (CQIs) and may result in more requested retransmissions. It may also lead to an increase in latency and inefficient use of network resources.

[0019] For example, interference from an arbitrary number of sources on one resource may complicate interference mitigation. By way of example, if interfering sources agree to use zero-forcing beamforming (ZFBF) to reduce their harmful effects, overhead for control signal exchange and channel feedback may grow significantly with the number of interferers. Hence, system latency may increase and throughput gains may be limited. By way of another example, if a receiving node wishes to perform SIC, the receiving node may listen to more resources than the receiving node is scheduled on to ensure correct decoding of the interfering signals. Then, the receiving node performs multiple rounds of SIC

-3-

1547351-1 to cancel each of the interfering signals. Latency and waste of network resources are further affected.

[0020] Coordinating resource allocation across various scheduling units may play an important role in minimizing interference across cells in homogenous and heterogeneous networks and efficiently using resources and reducing latency across the network. More specifically, such coordination may reduce or avoid arbitrary interference across the scheduled resources of a desired receiver (i.e., it may be better to have one interferer throughout all available PRBs than to have two or more interferers on less than all of the available PRBs), minimize overlap of scheduling grant of two or more WTRUs, and/or coordinate the overlap of the scheduling grant of two WTRUs.

[0021] Some cellular networks may enable minimal coordination among their base stations, providing for minimal reduction of ICI. Long term evolution (LTE) systems, for example, may employ Inter cell Interference Coordination (ICIC) to signal problematic physical resource blocks (PRBs) and facilitate interference avoidance techniques. Some systems may also, or alternatively, employ interference cancellation techniques, such as Successive Interference Cancellation (SIC) and zero forcing beam forming (ZFBF).

[0022] ICIC messaging is described in LTE Release 9. Base stations in

LTE systems may employ specified messaging techniques to inform other base stations in neighboring cells that certain PRBs are experiencing higher levels of interference. These messaging techniques may include exchanging information elements (IEs) such as interference overload indications (OIs) and/or high interference indications (HIIs) for uplink communications and relative narrowband transmit power (RNTPs) for downlink communications.

[0023] OIs may indicate to a neighboring cell a level of uplink interference experienced on PRBs of the cell bandwidth. For example, an OI may indicate that a PRB being reported is currently experiencing a high, medium or low level of interference. Upon receiving an OI, a neighboring cell may reduce the interference indicated by the OI by adjusting its scheduling, for example, by

-4-

1547351-1 using a different set of resources on the PRBs for which an 01 is received. Table 1 illustrates an example of OI reporting.

Table 1: OI Reporting

[0024] HIIs may indicate to a neighboring cell which portion or portions of the cell bandwidth a base station intends to schedule its cell-edge users on. This may notify the neighboring base stations to expect high uplink power on the corresponding PRBs. Because cell-edge users may be more susceptible to ICI, a base station receiving an HII may schedule the PRBs signaled in the HII to users located at or near the center of the cell in order to reduce the interference. Table 2 illustrates an example of HII reporting using a bit map denoting high or low interference for each PRB.

Table 2: HII Reporting

[0025] For ICIC in the downlink, transmission power may be restricted in portions of the transmission bandwidth. A cell may use RNTPs to dynamically inform neighboring cells which PRBs have restricted transmission power. Table

-5-

1547351-1 3 illustrates an example of RNTP reporting, denoting in a binary map a 0 or 1 for each PRB to indicate whether the power is restricted for the PRB.

Table 3: RNTP Reporting

[0026] While ICIC provides some information to neighboring nodes about expected interference on particular PRBs, this information does not enable the receiving node to coordinate resource scheduling with the sending node or to effectively cancel interfering signals (e.g., using SIC). The embodiments that follow may enable base stations to receive information that they may use to effectively coordinate resource scheduling with other base stations and/or to cancel interfering signals. It should be noted that the embodiments described herein provide specific examples that are adapted for use in long term evolution (LTE) systems. However, one of ordinary skill in the art will understand that the concepts described herein may be readily adapted for use in other communication systems. Further, the embodiments may be described in terms of base stations coordinating resource scheduling. However, it should be understood that any scheduling unit may perform resource coordination, regardless of whether the scheduling unit is located internal or external to a base station.

-6-

1547351-1 [0027] 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.

[0028] 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.

[0029] 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

-7-

1547351-1 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.

[0030] 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.

[0031] 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).

[0032] 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).

-8-

1547351-1 [0033] 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).

[0034] 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.

[0035] 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.

[0036] 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,

-9-

1547351-1 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.

[0037] 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.

[0038] 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.

[0039] 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

-10-

1547351-1 peripherals 138. It will be appreciated that the WTRU 102 may include any subcombination of the foregoing elements while remaining consistent with an embodiment.

[0040] 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.

[0041] 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.

[0042] 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

-11-

1547351-1 more transmit/receive elements 122 (e.g., multiple antennas) for transmitting and receiving wireless signals over the air interface 116.

[0043] 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.

[0044] 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).

[0045] 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.

[0046] The processor 118 may also be coupled to the GPS chipset 136, which may be configured to provide location information (e.g., longitude and

-12-

1547351-1 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.

[0047] 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.

[0048] 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, and 102c over the air interface 116. The RAN 104 may also be in communication with the core network 106.

[0049] 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.

-13-

1547351-1 [0050] Each of the eNode-Bs 140a, 140b, and 140c maybe 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.

[0051] 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.

[0052] The MME 142 may be connected to each of the eNode-Bs 142a, 142b, and 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.

[0053] 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.

[0054] 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.

-14-

1547351-1 [0055] 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.

[0056] The embodiments that follow may enable coordination of resource allocation across cells in homogenous and heterogeneous networks. For example, given a set of scheduling units, one or more of which wish to coordinate with other scheduling units, the one or more scheduling units may be provided with access to enough information about transmission patterns of one or more other cells to be able to track, directly or indirectly, one or more transmissions and, for each transmission, know which resources are scheduled for the same codeword or WTRU. This information may include an identifier for at least one of a plurality of WTRUs associated with a base station and a mapping of resources scheduled for each identifier. More specifically, the information may include a mapping of a WTRU identifier (ID) versus the resources across a cell or a problematic region of the cell (such as cell edge) or an indication of the WTRU IDs of all the WTRUs that may be interfering with a WTRU requesting coordination.

[0057] The WTRU ID may be a Radio Network Temporary Identifier

(RNTI) or any other ID that may clearly indicate a transmission of a same codeword or a transmission from or for a same WTRU. This information may be exchanged as an independent message or as an amendment to ICIC messaging. Embodiments for both scenarios are described below. In the embodiments that follow, the information being communicated may be referred to in terms of a PRB coordination message.

-15-

1547351-1 [0058] According to an embodiment, base stations may choose to exchange a PRB coordination message among them regardless of the existent ICIC signaling. This coordination message may include information regarding all the PRB usage and allocation throughout the cell or only regarding the PRBs that present severe interference issues and require special attention.

[0059] According to an embodiment, the PRB coordination message may include a number, N, of scheduled WTRUs reported, an ID for each codeword or WTRU that is to be reported and a mapping of the resource scheduling for each ID. The ID may be any ID that may be traced back or recovered, even if multiple codewords or WTRUs share the same PRB.

[0060] By way of example, the ID for each codeword or WTRU may be a different prime number associated with each codeword or WTRU. The prime number associated with a specific code word or WTRU may be mapped to each PRB used to transmit the codeword or by the same WTRU. For example, the PRB coordination message may include a string of numbers. Each position in the string may indicate a specific PRB and may include a product of the prime numbers associated with the WTRUs scheduled for the PRB or the codewords that the PRB is used to transmit. So if two or more WTRUs are scheduled on the same PRB, or two or more codewords are transmitted on the same PRB, the product of the IDs of those WTRUs or codewords may be reported in the position of that PRB in the PRB coordination message. If the number in that position is prime, the scheduling unit receiving the message knows that only one codeword or WTRU is scheduled on that PRB. If the number is not prime, the scheduling unit receiving the message may use a prime decomposition method to determine how many and which WTRUs or codewords are scheduled on the PRB. Thus, the scheduling unit may trace the full scheduling information of the PRB.

[0061] Use of prime numbers or other non-RNTI identifiers as IDs may be particularly useful where a base station does not wish to share the actual ID of its scheduled WTRU and wishes to mask its information for security reasons. However, where this is not a concern, for example, the RNTI of the scheduled WTRU may be used as the ID. Using the RNTI of the scheduled WTRU as the ID

-16-

1547351-1 may be more useful where the neighboring receiver wishes to decode the interfering signal to perform interference mitigation, such as SIC. The modulation and coding scheme (MCS) used for each WTRU or codeword may be appended as another layer of information.

[0062] When the RNTI is used as the ID, the PRB coordination message may include a string of Boolean values of size <MaxNofPRB> (e.g., 110 PRBs) for each scheduled WTRU identified by its RNTI. Each position in the bitmap may represent a PRB. For example, a '0' in a given position may indicate that the associated PRB is not scheduled for that RNTI and a '1' in a given position may indicate that the associated PRB is scheduled for that RNTI, and vice versa. By way of example, a table may be defined to communicate a mapping of the RNTIs to the string of Boolean values and 'N' may be exchanged separately. Table 4 illustrates an example table that may be used for this purpose.

Table 4: RNTI to PRB Allocation Message

[0063] By way of another example, the PRB coordination message may include a sequential listing of the IDs of the scheduled WTRUs in the same order as the PRB listing. Where multiple WTRUs share the same resources, their IDs may also be listed sequentially. Table 5 illustrates an example PRB coordination

-17-

1547351-1 message for this example. In Table 5, 'NaN' represents a non-valid RNTI, indicating an empty field or "nothing to report" for a non- scheduled PRB.

Table 5: PRB Coordination Message

[0064] According to another embodiment, ICIC messages (e.g., HII, 01 and

RNTP) may be amended to include RNTIs, or any other IDs, associated with WTRUs scheduled on PRBs to be reported. Such PRBs may be, for example, PRBs having power that exceeds a defined threshold as per an RNTP signal, PRBs having a value of '1' in the HII message, or PRBs having high or medium interference levels in the OI message.

[0065] By way of example, for a WTRU scheduled on a problematic PRB, an associated base station may choose to report the RNTI of that WTRU on all the PRBs the WTRU is scheduled on, even if those PRBs are not included in the set

-18-

1547351-1 of PRBs with problems. Where the base station does not choose to do so, a neighboring base station or WTRU (macro or micro) may obtain the complete scheduling grant of the WTRUs pertinent to its operation by receiving the amended ICIC message.

[0066] An example amended HII message is illustrated in Table 6. OI and

RNTP signaling may be similarly amended.

Table 6: Amended HII Reporting

-19-

1547351-1 [0067] Since the scheduling operation may be performed dynamically, the coordination message may be timely updated. This may take place over the X2 channel if low latency is required or through the air if latency requirements allow. Further, semi-persistent scheduling may be applied on a WTRU once the WTRU is identified for resource coordination (e.g., triggered by an SIC application or any other kind of interference mitigation or avoidance technique) to reduce the X2 latency and message update interval requirement. By doing so, frequent exchange of information may be avoided and the overhead of the resource coordination may be reduced.

[0068] FIG. 2 is an example flow diagram 200 of a method of coordinating scheduling of resources among different cells in a wireless network. In step 202, a scheduling unit (such as a base station) may receive a notification from a WTRU associated with the base station in its cell that interference was detected. In step 204, the base station may generate and transmit a coordination message to a base station in another cell that is associated with the interference that was detected. The coordination message may be any of the coordination messages described above and may include resource scheduling information for the WTRU associated with the base station.

[0069] FIG. 3A is an example signal diagram 300A illustrating more detailed signaling for coordinating scheduling of resources among different cells in the wireless network. In FIG. 3A, a heterogeneous network including a Micro- WTRU, a Macro-WTRU, a Macro-eNB and a Micro-eNB is illustrated. However, the illustrated signaling may be implemented in any heterogeneous or homogeneous network including any number and type of receiving nodes and scheduling entities.

[0070] As illustrated in FIG. 3A, a receiving node (e.g., Macro-WTRU) may perform signal and interference measurement. For example, the receiving node may receive and measure a signal 302 and interference 304. In step 306, the receiving node may determine whether it experiences interference that is above a pre-set threshold. In step 308, the receiving node may identify the origin of the interference. If the interference from a certain cell or sector exceeds the pre-set

-20-

1547351-1 threshold in step 306, the receiving node may inform its corresponding base station (e.g., Macro-eNB), for example, by transmitting a report 310 indicating that interference was detected and identifying the origin of the interference. In step 312, the Macro-eNB may coordinate with the base station of the interfering cell (e.g., Micro-eNB) to coordinate scheduling the WTRU (e.g., Macro-WTRU) associated with the base station (e.g., Macro-eNB) with the base station of the interfering cell (e.g., Micro-eNB), for example, using the messaging described above. In an embodiment, the messaging includes exchanging coordination messages over the X2 backhaul link. Both eNBs may send new scheduling grants 316 and 318 and any corresponding control information 314 to their corresponding WTRUs. The Macro WTRU may then receive and measure a signal 322 and interference 320. The Macro WTRU may use information received in a coordination message to cancel the interference 320 from the signal 322 (e.g., using SIC or ZFBF, as described in more detail with respect to FIG. 9 below) in step 324.

[0071] FIG. 3B is another signal diagram illustrating more detailed signaling for coordinating scheduling of resources among different cells in the wireless network. In FIG. 3B, some elements are the same as in FIG. 3A and are given the same numbering. Those elements are not described further here.

[0072] In FIG. 3B, the signal measurement described with respect to FIG.

3A may be a channel quality measurement, as indicated in step 303. If the channel quality is found not satisfactory by the receiving node or the corresponding base station, in step 310, the receiving node may inform its corresponding base station (e.g., Macro-eNB), for example, by transmitting a report (e.g., a measuring report) indicating same. In step 311, the Macro-eNB may try to find the likely or suspected source(s) of interference and coordinate with the base station of the suspected interfering cell (e.g., Micro-eNB) to coordinate scheduling the WTRU (e.g., Macro-WTRU) associated with the base station (e.g., Macro-eNB) with the base station of the interfering cell (e.g., Micro- eNB), for example, using the messaging described above. The Macro-eNB may

-21-

1547351-1 use the location or any other type of information to find the likely or suspected source(s) of the interference.

[0073] One of ordinary skill in the art will recognize that base stations may coordinate scheduling of resources in many different ways using the information provided in the coordination messages. For purposes of comparison, Fig. 4 illustrates an example uncoordinated resource scheduling across two cells (a micro and a macro cell). More specifically, FIG. 4 illustrates messages 402, 404, 406 and 408 generated by a Macro WTRU and three Micro WTRUs, respectively. Each illustrated message includes information transmitted on select ones of eight PRBs 410, 412, 414, 416, 418, 420, 422 and 424. In this example, per a scheduling grant from a Micro eNB (not shown), the Micro WTRU 1 transmits on PRBs 410, 416 and 418, the Micro WTRU 2 transmits on PRBs 412 and 420 and the Micro WTRU 3 transmits on PRBs 412, 414, 420 and 422. Micro WTRUs 2 and 3 may be scheduled on overlapping resources to enable Multiuser-MIMO techniques. Since the Micro eNB does not share any of the scheduling information with the Macro eNB, the Macro eNB proceeds to schedule the Macro WTRU 1 on PRBs 410, 412 and 414. Accordingly, the Macro WTRU 1 suffers interference of only one signal on PRB 410 and PRB 414 and of two signals on PRB 412. Thus, the Macro WTRU 1 has three signals that arbitrarily overlap in scheduled resources with the Macro WTRU 1.

[0074] If the Macro eNB were aware of the scheduling pattern shown in

FIG. 4, it may have scheduled the Macro WTRU 1 on different resources to minimize the number of interferers experienced by Macro WTRU 1. For example, in FIG. 5, the Micro WTRUs 1, 2 and 3 are scheduled on the same PRBs as in FIG. 4, but the Macro eNB (not shown) is aware of the scheduling pattern for the Micro WTRUs 1, 2 and 3 and adjusts its scheduling of the Macro WTRU 1 accordingly. In the illustrated example, the Macro WTRU 1 is scheduled on PRBs 510, 516 and 518. With proper adjustment of transmission parameters (MCS, coding rate, etc.), this scheduling pattern for the Macro WTRU 1 may result in a better overall system throughput and reduction in latency at Macro

-22-

1547351-1 WTRU 1 at least. A maximum of two WTRUs are scheduled on any given PRB in this example.

[0075] By way of another example, the Micro and Macro eNBs may jointly reach a scheduling agreement. FIG. 6 illustrates an example where the Micro eNB schedules only Micro WTRUs 1 and 2 to interfere with Macro WTRU 1 and not to overlap with each other. In FIG. 6, messages 602, 604 and 606 are generated by a Macro WTRU 1 and two Micro WTRUs 1 and 2, respectively. Each illustrated message includes information transmitted on select ones of six PRBs 608, 610, 612, 614, 616 and 618. In this example, per a scheduling grant from a Macro eNB (not shown), the Macro WTRU 1 spreads its transmission across all the PRBs scheduled for Micro WTRUs 1 and 2 combined (namely, PRBs 608, 610, 612, 614 and 616). Here, each PRB is scheduled for two transmissions each. While the Macro WTRU 1 is scheduled on more resources than in the example illustrated in FIG. 5, this may be justified with the higher rate that is possible with the example illustrated in FIG. 6.

[0076] As indicated in FIGs. 3A and 3B, WTRUs may use the information provided in the coordination messages to cancel interference. Two potential methods for canceling interference, ZFBF and SIC, are described below.

[0077] With ZFBF, a transmitter may use a precoding matrix that enables the nulling of its transmission at a receiver suffering interference from the transmitter. Channel estimation of the transmitter's link to the receiver may be required to accurately construct the precoding matrix.

[0078] SIC includes iteratively decoding interfering signals and canceling their impact under certain conditions. By way of example, a two user interfering channel 700 is illustrated in FIG. 7. In step 706, a transmitter (Txi) 708 of user 702 sends a message mi to a receiver (Rxj) 710, and in step 718, a transmitter (Txi) 720 of user 704 sends a message mi to a receiver (Rxj) 722. For i = 1, 2, the received signal at each receiver may be described as follows:

y_x = A_{j χ}χ_χ + ^2^2 ^{+ z}i '■_> Equation (1) y₂ = h^₂x_x + /222^x2 ^{+ z}2 ' Equation (2)

-23-

1547351-1 as illustrated in boxes 712 and 724 in FIG. 7. In equations 1 and 2, denotes the channel between transmitter Txi and receiver Rxj, "x. " is the codeword transmitted by Txi, and " z . " is the noise experienced on the link to receiver Rxi. On a condition that receiver 710 experiences strong interference, receiver 710 may estimate and cancel x2 , as illustrated in box 714. Receiver 710 may then decode xl, as illustrated in box 716, and enjoy an interference free channel. On a condition that receiver 722 does not experience strong interference, or if the receiver 722 is not SIC capable, receiver 722 may simply decode x2, as illustrated in box 726.

[0079] In cellular systems, SIC may be applied both in the uplink between base stations and in the downlink between WTRUs. It may also be applied between macro cells and between macro and micro cells.

[0080] SIC may be used between macro and micro cells in heterogeneous networks to mitigate Id. FIG. 8 illustrates an example operation of SIC in the uplink. In FIG. 8, a Micro Cell 808 and a Macro Cell 802 are illustrated. The Macro Cell 802 includes a Macro eNB 804 and a Macro WTRU 812, and the Micro Cell 808 includes a Micro eNB 806 and a Micro WTRU 810. The Micro WTRU 810 transmits the Micro WTRU data, as reflected in 818, and the Macro WTRU 812 transmits the Macro WTRU data, as reflected in 820.

[0081] The Micro eNB 806 may receive the Micro WTRU data transmission intended for it and also the Macro WTRU data as interference. Because the Micro eNB 806 is SIC capable, it may decode the interference data received from the Macro WTRU 812, as reflected in 816. If the data is decoded without error, the Micro eNB 806 may subtract the re-encoded interference data from the received signal so that the Micro Cell 808 may decode the desired Micro WTRU data without the interference from the Macro WTRU 812, as also reflected in 816. On a condition that the Macro WTRU 812 transmits multiple codewords, the codewords may be decoded in a successive manner, or part of the codewords may be decoded at the Micro eNB 806. The Micro eNB 806 may successfully decode the interference data with a high probability at least because MCS level of the

-24-

1547351-1 Macro WTRU 812 may be determined based on a relatively large path loss to the Macro eNB 804. A similar procedure may be applicable to the downlink, enabling SIC at the Macro WTRU 812. In FIG. 8, the Macro eNB 804 is not SIC capable and, therefore, it only decodes the Macro WTRU data intended for it.

[0082] In either the uplink or the downlink, a receiver wishing to perform

SIC may first intercept the interfering signal and fully decode it. To enable this, in the uplink for example, the Macro and Micro eNBs may exchange the uplink scheduling grant of the Macro WTRU over the X2 interface so that the Micro eNB has all the control information required to correctly receive and decode the uplink transmission from the Macro WTRU. In LTE and LTE-Advanced (LTE-A) systems, the uplink scheduling grant may be embedded in Downlink Control Information (DCI) format 0 and may include an RNTI of the scheduled WTRU, an MCS level, a resource block allocation, a new data indication, a phase rotation of Demodulation Reference Signal (DMRS), etc.

[0083] Similarly, for the downlink, Macro WTRUs near the micro cell may receive strong interference, and the Macro WTRUs may conduct SIC to eliminate interference from the Micro eNB. Although the Micro WTRU may also receive interference, the Micro WTRU may overcome the ICI with high received desired signal power and enough resource allocation. As described above, for SIC, the Macro WTRU requires control information from the Micro WTRUs, and it may be signaled by the macro cell or the micro cell.

[0084] According to an embodiment, SIC may be implemented in conjunction with coordinated resource scheduling. For example, if scheduling of resources is coordinated, as in the examples illustrated in FIGs. 5 and 6, the Macro WTRU may also perform SIC if the interfering signals may be correctly decoded at the Macro WTRU.

[0085] FIG. 9 is an example flow diagram 900 of a method of performing

SIC. In step 902, the Macro WTRU may obtain control information from the Micro eNB, either directly or through the Macro eNB. This may include the RNTIs of the interfering nodes and their scheduling grants. In step 904, the Macro WTRU may listen to PRBs. In step 906, the Macro WTRU may identify

-25-

1547351-1 which Micro WTRU to decode interference from first. Alternatively, the Macro WTRU may decide to decode all of the interferers in parallel. In step 908, the Macro WTRU may decode interference from the identified WTRU. In step 910, the Macro WTRU may cancel the interference from the identified WTRU. In decision block 912, the Macro WTRU may determine whether any interferers remain. If so, the method may return to step 906 and steps 906, 908, 910 and 912 may be repeated until no interferers remain. If no interferers remain at decision block 912, the Macro WTRU may decode the communication that was intended for it.

[0086] In the embodiment illustrated in FIG. 9, if resources were not coordinated (e.g., as in FIG. 4), in step 904, the Macro WTRU may listen to all of the available resources (e.g., PRBs 410, 412, 414, 416, 418, 420, 422 and 424). Also, in this embodiment, multiple rounds of SIC may be performed to cancel interference from all of Micro WTRUs 1, 2 and 3. However, when resource scheduling is coordinated (e.g., as in FIG. 5 or FIG. 6), the Macro WTRU may only need to listen to the resources on which it is scheduled (e.g., PRBs 510, 516 and 518 in FIG. 5). Further, only one round of SIC may need to be conducted because only one interfering WTRU may be identified in step 906 (e.g., Micro WTRU 1 in FIG. 5).

[0087] Thus, when scheduling of resources is coordinated, as described, for example, in the embodiments above, the macro WTRU may only need to listen to the PRBs on which it is scheduled. Further, less rounds of SIC may need to be conducted in order to cancel all interferers.

[0088] With the exchange of the information provided in the coordination messages, as described above, a scheduling unit aware of a receiving node wishing to perform SIC may look for the best matching interferer to enable SIC and increase throughput of at least one of them. Also, if SIC were to be enabled across the cell, information pertinent to decoding interfering signals such as MCS may be exchanged under the umbrella of this information exchange.

-26-

1547351-1 EMBODIMENTS

1. A method of coordinating scheduling of resources among different cells in a wireless network.

2. The method of embodiment 1, further comprising a base station receiving an indication from a wireless transmit receive unit (WTRU) associated with the base station that interference is suspected.

3. The method of embodiment 2, further comprising the base station estimating a likely source of interference.

4. The method of embodiment 3, further comprising the base station transmitting a coordination message to at least one other base station associated with the interference that was suspected, the coordination message including resource scheduling information for the WTRU associated with the base station.

5. The method of embodiment 1, further comprising a base station receiving a notification from a wireless transmit receive unit (WTRU) associated with the base station that interference was detected.

6. The method of embodiment 5, further comprising the base station transmitting a coordination message to at least one other base station associated with the interference that was detected, the coordination message including resource scheduling information for the WTRU associated with the base station.

7. The method of any one of embodiments 4 and 6, further comprising the base station coordinating scheduling the WTRU associated with the base station with the at least one other base station.

8. The method of any one of embodiments 2-7, wherein a plurality of WTRUs are associated with the base station.

9. The method of embodiment 8, wherein the resource scheduling information includes an identifier for at least one of the plurality of WTRUs associated with the base station.

10. The method of embodiment 9, wherein the resource scheduling information includes a mapping of resources scheduled for each identifier.

11. The method of embodiment 10, wherein the resources are physical resource blocks (PRBs).

-27-

1547351-1 12. The method of any one of embodiments 9-11, wherein the identifier includes a different prime number assigned to the at least one of the plurality of WTRUs associated with the base station, and the mapping includes a string of numbers, each of the numbers representing a product of the identifiers scheduled for a respective one of the PRBs.

13. The method of any one of embodiments 9-12, wherein the identifier includes a radio network temporary identifier (RNTI) for each of the at least one of the plurality of WTRUs associated with the base station, and the mapping includes a string of bits indicating, for each of the WTRUs associated with the base station, whether the WTRU is scheduled for each respective one of the PRBs.

14. The method of any one of embodiments 4 and 6, wherein a plurality of WTRUs are associated with the base station, and the coordination message is an Inter cell Interference Coordination (ICIC) message that also includes an identifier for each of the plurality of WTRUs associated with the base station that is scheduled on a physical resource block (PRB) that is experiencing a defined level of interference.

15. The method of embodiment 14, wherein the ICIC message is one of an overload indication (01), a high interference indication (HII) and a relative narrowband transmit power (RNTP).

16. A method implemented in a wireless transmit/receive unit (WTRU).

17. The method of embodiment 16, further comprising receiving an allocation of resources for communications.

18. The method of any one of embodiments 16 and 17, further comprising detecting interference.

19. The method of embodiment 18, further comprising identifying an origin of the interference.

20. The method of embodiment 19, further comprising transmitting a report indicating that interference was detected and identifying the origin of the interference.

-28-

1547351-1 21. The method of embodiment 20, further comprising receiving a new allocation of resources for communications in response to transmission of the report.

22. The method of embodiment 16, further comprising receiving an allocation of resources for communications.

23. The method of any one of embodiments 16 and 22, further comprising

transmitting a report indicating that interference is suspected.

24. The method of embodiment 23, further comprising receiving a new allocation of resources for communications in response to transmission of the report.

25. A wireless network comprising a wireless transmit/receive unit (WTRU) configured to perform the method of any one of embodiments 16-24.

26. The wireless network of embodiment 25, further comprising a base station configured to perform the method of any one of embodiments 1-15.

27. The wireless network of embodiment 26, wherein the WTRU is further configured to transmit a report that interference was detected from a particular cell.

28. The wireless network of any one of embodiments 26-27, wherein the base station is further configured to receive the report from the WTRU and transmit a coordination message to at least one other base station in the particular cell, the coordination message including resource scheduling information for the WTRU.

29. The wireless network of any one of embodiments 26-28, wherein the base station and the at least one other base station are configured to coordinate scheduling of resources between one another based at least on the coordination message.

30. The wireless network of embodiment 29, wherein the base station and the at least one other base station are configured to coordinate scheduling of the resources between one another by ensuring that no more than a defined number of WTRUs in the first and second cells combined are scheduled on the

-29-

1547351-1 same resource.

31. The wireless network of any one of embodiments 29 and 30, wherein the base station is further configured to transmit an allocation of resources for communications to the WTRU and transmit a new allocation of resources for communications to the WTRU based on the coordinated scheduling of resources.

32. The wireless network of any one of embodiments 27-31, further comprising a plurality of WTRUs associated with the base station.

33. The wireless network of embodiment 32, wherein the resource scheduling information includes an identifier for at least one of the plurality of WTRUs associated with the base station.

34. The wireless network of any one of embodiments 32 and 33, wherein the resource scheduling information includes a mapping of resources scheduled for each identifier.

35. The wireless network of any one of embodiments 26-34 wherein the base station and the at least one other base station are configured to communicate using a long term evolution (LTE) air interface, and the resources are physical resource blocks (PRBs).

36. The wireless network of any one of embodiments 33-35, wherein the identifier includes a radio network temporary identifier (RNTI) for each of the at least one of the plurality of WTRUs associated with the base station, and the mapping includes a string of bits indicating, for each of the WTRUs associated with the base station, whether the WTRU is scheduled for each respective one of the PRBs.

37. The wireless network of any one of embodiments 33-36, wherein the identifier includes a different prime number assigned to the at least one of the plurality of WTRUs associated with the base station, and the mapping includes a string of numbers, each of the numbers representing a product of the identifiers scheduled for a respective one of the PRBs.

38. The wireless network of any one of embodiments 28-37, further comprising a plurality of WTRUs associated with the base station, wherein the coordination message is an Inter cell Interference Coordination (ICIC) message

-30-

1547351-1 that also includes an identifier for any WTRUs associated with each cell that are scheduled on a PRB that is experiencing a defined level of interference.

39. The wireless network of embodiment 38, wherein the ICIC message is one of an overload indication (OI), a high interference indication (HII) and a relative narrowband transmit power (RNTP).

40. The wireless network of any one of embodiments 27-39, wherein the WTRU is further configured to detect the interference and identify the particular cell from which the interference originated.

[0088] 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.

-31-

1547351-1

Claims

CLAIMS What is claimed:

1. A method of coordinating scheduling of resources among different cells in a wireless network, the method comprising:

a base station receiving an indication from a wireless transmit receive unit (WTRU) associated with the base station that interference is suspected;

the base station estimating a likely source of interference; and the base station transmitting a coordination message to at least one other base station associated with the interference that was suspected, the coordination message including resource scheduling information for the WTRU associated with the base station.

2. A method of coordinating scheduling of resources among different cells in a wireless network, the method comprising:

a base station receiving a notification from a wireless transmit receive unit (WTRU) associated with the base station that interference was detected; and the base station transmitting a coordination message to at least one other base station associated with the interference that was detected, the coordination message including resource scheduling information for the WTRU associated with the base station.

3. The method of claim 2, further comprising the base station coordinating scheduling the WTRU associated with the base station with the at least one other base station.

4. The method of claim 2, wherein a plurality of WTRUs are associated with the base station, and the resource scheduling information includes:

an identifier for at least one of the plurality of WTRUs associated with the base station; and

a mapping of resources scheduled for each identifier.

-32-

1547351-1

5. The method of claim 4, wherein the resources are physical resource blocks (PRBs).

6. The method of claim 5, wherein the identifier includes a different prime number assigned to the at least one of the plurality of WTRUs associated with the base station, and the mapping includes a string of numbers, each of the numbers representing a product of the identifiers scheduled for a respective one of the PRBs.

7. The method of claim 5, wherein the identifier includes a radio network temporary identifier (RNTI) for each of the at least one of the plurality of WTRUs associated with the base station, and the mapping includes a string of bits indicating, for each of the WTRUs associated with the base station, whether the WTRU is scheduled for each respective one of the PRBs.

8. The method of claim 2, wherein a plurality of WTRUs are associated with the base station, and the coordination message is an Inter cell Interference Coordination (ICIC) message that also includes an identifier for each of the plurality of WTRUs associated with the base station that is scheduled on a physical resource block (PRB) that is experiencing a defined level of interference.

9. The method of claim 8, wherein the ICIC message is one of an overload indication (01), a high interference indication (HII) and a relative narrowband transmit power (RNTP).

10. A method implemented in a wireless transmit/receive unit (WTRU), the method comprising:

receiving an allocation of resources for communications;

detecting interference;

identifying an origin of the interference;

-33-

1547351-1 transmitting a report indicating that interference was detected and identifying the origin of the interference; and

receiving a new allocation of resources for communications in response to transmission of the report.

11. A method implemented in a wireless transmit/receive unit (WTRU), the method comprising:

receiving an allocation of resources for communications;

transmitting a report indicating that interference is suspected; and receiving a new allocation of resources for communications in response to transmission of the report.

12. A wireless network comprising:

a wireless transmit/receive unit (WTRU) configured to transmit a report that interference was detected from a particular cell; and

a base station configured to receive the report from the WTRU and transmit a coordination message to at least one other base station in the particular cell, the coordination message including resource scheduling information for the WTRU.

13. The wireless network of claim 12, wherein the base station and the at least one other base station are configured to coordinate scheduling of resources between one another based at least on the coordination message.

14. The wireless network of claim 12, wherein the base station and the at least one other base station are configured to coordinate scheduling of the resources between one another by ensuring that no more than a defined number of WTRUs in the first and second cells combined are scheduled on the same resource.

15. The wireless network of claim 12, wherein the base station is

-34-

1547351-1 further configured to transmit an allocation of resources for communications to the WTRU and transmit a new allocation of resources for communications to the WTRU based on the coordinated scheduling of resources.

16. The wireless network of claim 12, further comprising a plurality of WTRUs associated with the base station, wherein the resource scheduling information includes:

an identifier for at least one of the plurality of WTRUs associated with the base station and

a mapping of resources scheduled for each identifier.

17. The wireless network of claim 16, wherein the base station and the at least one other base station are configured to communicate using a long term evolution (LTE) air interface, and the resources are physical resource blocks (PRBs).

18. The wireless network of claim 17, wherein the identifier includes a radio network temporary identifier (RNTI) for each of the at least one of the plurality of WTRUs associated with the base station, and the mapping includes a string of bits indicating, for each of the WTRUs associated with the base station, whether the WTRU is scheduled for each respective one of the PRBs.

19. The wireless network of claim 17, wherein the identifier includes a different prime number assigned to the at least one of the plurality of WTRUs associated with the base station, and the mapping includes a string of numbers, each of the numbers representing a product of the identifiers scheduled for a respective one of the PRBs.

20. The wireless network of claim 12, further comprising a plurality of WTRUs associated with the base station, wherein the coordination message is an Inter cell Interference Coordination (ICIC) message that also includes an

-35-

1547351-1 identifier for any WTRUs associated with each cell that are scheduled on a PRB that is experiencing a defined level of interference.

21. The wireless network of claim 20, wherein the ICIC message is one of an overload indication (OI), a high interference indication (HII) and a relative narrowband transmit power (RNTP).

22. The wireless network of claim 12, wherein the WTRU is further configured to detect the interference and identify the particular cell from which the interference originated.

-36-

1547351-1