HK1170611A - Data transmission with cross-subframe control in a wireless network - Google Patents

Description

Data transmission with cross-subframe control in wireless networks

The present application claims priority OF U.S. provisional application entitled "SYSTEMS AND METHODS OF supporting assisted/random EXTENSION information associated with network OF VIA CROSS section SUBFRAME CONTROL", serial No.61/184,218, and U.S. provisional application entitled "TRANSMITTING GREEURCE UTILIZATION MESSAGES ON THE PHYSICAL DOWNLINKCONHOL CHANNEL", serial No.61/184,224, both OF which were filed 6/4/2009, assigned to their assignee, and incorporated herein by reference.

Technical Field

The present disclosure relates generally to communication, and more specifically to techniques for supporting data transmission in a wireless communication network.

Background

Wireless communication networks are widely deployed to provide various communication content such as voice, video, packet data, messaging, broadcast, and so on. These wireless networks may be multiple-access networks capable of supporting multiple users by sharing the available network resources. Examples of such multiple-access networks include Code Division Multiple Access (CDMA) networks, Time Division Multiple Access (TDMA) networks, Frequency Division Multiple Access (FDMA) networks, orthogonal FDMA (ofdma) networks, and single carrier FDMA (SC-FDMA) networks.

A wireless communication network may include multiple base stations, which may support communication for multiple User Equipments (UEs). A UE may communicate with a base station via the downlink and uplink. The downlink (or forward link) refers to the communication link from the base stations to the UEs, and the uplink (or reverse link) refers to the communication link from the UEs to the base stations.

A base station may transmit data to one or more UEs on the downlink and may receive data from one or more UEs on the uplink. On the downlink, data transmissions from a base station may experience interference due to data transmissions from neighboring base stations. On the uplink, data transmissions from each UE may experience interference due to data transmissions from other UEs communicating with neighboring base stations. For both downlink and uplink, performance may be degraded due to interference caused by interfering base stations and interfering UEs.

Disclosure of Invention

Techniques for supporting communication in a dominant interference scenario are described herein. A dominant interference scenario is a scenario where a UE or base station experiences high interference, which may severely degrade data transmission performance.

In an aspect, cross-subframe control may be used to support communication in a dominant interference scenario. Different base stations may be allocated different subframes to transmit control information. Each base station may transmit control messages in subframes allocated to that base station. Different base stations may have different timelines for sending control messages due to their allocation of different subframes. With cross-subframe control, control information (e.g., grants, acknowledgements, etc.) may be sent in a first subframe and may be applied for data transmission in a second subframe, which may be a variable number of subframes from the first subframe.

In one design, control information may be exchanged (e.g., transmitted or received) in a first subframe. Data may be exchanged in the second subframe based on the control information exchanged in the first subframe. The second subframe may be a variable number of subframes from the first subframe. Acknowledgements for data exchanged in the second subframe may be exchanged in the third subframe. The third subframe may also be a variable number of subframes from the second subframe.

In another aspect, a message may be sent on a Physical Downlink Control Channel (PDCCH) to suppress interference. In one design, the base station may send a message on the PDCCH requesting reduced interference. Thereafter, the base station may exchange (e.g., transmit or receive) data on resources having reduced interference due to the message sent on the PDCCH. In one design, the UE may monitor for a message sent by at least one base station on the PDCCH to request reduced interference. The UE may exchange data on resources with reduced interference due to the message sent on the PDCCH by the at least one base station.

Various aspects and features of the disclosure are described in further detail below.

Drawings

Fig. 1 illustrates a wireless communication network.

Fig. 2 shows an exemplary frame structure.

Fig. 3 shows two exemplary subframe formats for the downlink.

Fig. 4 shows an exemplary subframe format for the uplink.

Fig. 5 shows an exemplary interlace structure.

Fig. 6 illustrates an exemplary Frequency Division Multiplexing (FDM) partition for the uplink.

Fig. 7 and 8 show data transmission with interference suppression on the downlink and uplink, respectively.

Fig. 9 and 10 illustrate data transmission with interference suppression on the downlink and uplink, respectively, with Time Division Multiplexed (TDM) partitioning of the downlink.

Fig. 11 and 12 show a process and an apparatus, respectively, for exchanging data in the case of cross-subframe control.

Fig. 13 and 14 illustrate a process and apparatus, respectively, for sending at least one grant for data transmission in a variable number of subframes.

Fig. 15 and 16 show a process and apparatus, respectively, for sending a message for interference suppression on PDCCH.

Fig. 17 and 18 illustrate a process and apparatus, respectively, for receiving a message for interference suppression sent on a PDCCH.

Fig. 19 shows a block diagram of a base station and a UE.

Detailed Description

The techniques described herein may be used for various wireless communication networks such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA and other networks. The terms "network" and "system" are generally used interchangeably. A CDMA network may implement a radio technology such as Universal Terrestrial Radio Access (UTRA), CDMA 2000, etc. UTRA includes wideband CDMA (W-CDMA) and other variants of CDMA. cdma 2000 covers IS-2000, IS-95 and IS-856 standards. TDMA networks may implement radio technologies such as global system for mobile communications (GSM). OFDMA networks may implement methods such as evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE802.11(Wi-Fi), IEEE 802.16(WiMAX), IEEE 802.20, and,Etc. radio technologies. UTRA and E-UTRA are parts of the Universal Mobile Telecommunications System (UMTS). 3GPP Long Term Evolution (LTE) and LTE-advanced (LTE-A) are new versions of UMTS that use E-UTRA, which employ OFDMA on the downlink and SC-FDMA on the uplink. UTRA, E-UTRA, UMTS, LTE-A, and GSM are described in literature from an organization named "third Generation partnership project" (3 GPP). Cdma 2000 and UMB are described in documents from an organization named "third generation partnership project 2" (3GPP 2). The techniques described herein may be used for the wireless networks and radio technologies described above as well as other wireless networks and radio technologies. For clarity, some aspects of these techniques are described below for LTE, and are described below in the followingLTE terminology is used in some of the description.

Fig. 1 shows a wireless communication network 100, which may be an LTE network or some other wireless network. Wireless network 100 may include a plurality of evolved node bs (enbs) 110 and other network entities. An eNB may be an entity in communication with a UE and may also be referred to as a base station, a node B, an access point, etc. Each eNB may provide communication coverage for a particular geographic area. In 3GPP, the term "cell" can refer to a coverage area of an eNB and/or an eNB subsystem serving the coverage area, depending on the environment in which the term is used.

An eNB may provide communication coverage for a macro cell, pico cell, femto cell, and/or other types of cells. A macro cell may cover a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by UEs with service subscriptions. A pico cell may cover a relatively small geographic area and may allow unrestricted access by UEs with service subscription. A femto cell may cover a relatively small geographic area (e.g., a home) and may allow limited access by UEs already associated with the femto cell (e.g., UEs in a Closed Subscriber Group (CSG)). An eNB for a macro cell may be referred to as a macro eNB. An eNB for a pico cell may be referred to as a pico eNB. An eNB for a femto cell may be referred to as a femto eNB or a home eNB (henb). In the example shown in fig. 1, eNB110a may be a macro eNB for macro cell 102a, eNB110b may be a pico eNB for pico cell 102b, and eNB110 c may be a femto eNB for femto cell 102 c. One eNB may support one or more (e.g., three) cells. The terms "eNB", "base station", and "cell" may be used interchangeably herein.

Wireless network 100 may also include relay stations. A relay station may be an entity capable of receiving a transmission of data from an upstream station (e.g., an eNB or UE) and sending a transmission of data to a downstream station (e.g., a UE or eNB). A relay station may also be a UE that is capable of relaying transmissions for other UEs. In the example shown in fig. 1, relay 110d may communicate with UE 120d via an access link and with macro eNB110a via a backhaul link, thereby facilitating communication between eNB110a and UE 120 d. A relay station may also be referred to as a relay eNB, a relay base station, a relay device, etc.

Wireless network 100 may be a heterogeneous network that includes different types of enbs, e.g., macro enbs, pico enbs, femto enbs, relay enbs, and so on. These different types of enbs may have different transmit power levels, different coverage areas, and different effects on interference in wireless network 100. For example, macro enbs may have a high transmit power level (e.g., 5 to 40 watts), while pico enbs, femto enbs, and relay enbs may have a lower transmit power level (e.g., 0.1 to 2 watts).

Network controller 130 may be coupled to a set of enbs and may provide coordination and control for these enbs. Network controller 130 may communicate with the enbs via a backhaul. The enbs may also communicate with each other, directly or indirectly, e.g., via a wireless or wired backhaul.

UEs 120 may be dispersed throughout wireless network 100, and each UE may be fixed or mobile. A UE may also be referred to as a mobile station, terminal, access terminal, subscriber unit, station, etc. A UE may be a cellular telephone, a Personal Digital Assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a laptop computer, a cordless telephone, a Wireless Local Loop (WLL) station, a smart phone, a netbook, a smartbook, or the like. The UE can communicate with macro enbs, pico enbs, femto enbs, relay enbs, and the like. In fig. 1, the solid double-arrow line indicates the desired transmission between the UE and the serving eNB, which is the eNB designated to serve the UE on the downlink and/or uplink. The dashed double arrow indicates interfering transmissions between the UE and the eNB.

Fig. 2 shows an exemplary frame structure 200 for frequency division multiplexing (FDD) in LTE. The transmission timeline for each of the downlink and uplink may be divided into units of radio frames. Each radio frame may have a predetermined duration (e.g., 10 milliseconds (ms)) and may be divided into 10 subframes indexed 0 through 9. Each subframe may include two slots. Each radio frame may thus include 20 slots with indices of 0 through 19. Each slot may include L symbol periods, e.g., seven symbol periods for a normal cyclic prefix (as shown in fig. 2) or six symbol periods for an extended cyclic prefix. The 2L symbol periods in each subframe may be assigned indices of 0 through 2L-1.

LTE uses Orthogonal Frequency Division Multiplexing (OFDM) on the downlink and single carrier frequency division multiplexing (SC-FDM) on the uplink. OFDM and SC-FDM divide a frequency range into multiple (N)_FFTMultiple) orthogonal subcarriers, which are also commonly referred to as tones (tones), bins (bins), and so on. Each subcarrier may be modulated with data. In general, modulation symbols are sent in OFDM in the frequency domain and SC-FDM in the time domain. The interval between adjacent subcarriers may be fixed, and the total number of subcarriers (N)_FFT) May depend on the system bandwidth. For example, N for a system bandwidth of 1.25, 2.5, 5, 10, or 20 megahertz (MHz)_FFTMay be equal to 128, 256, 512, 1024 or 2048, respectively. The system bandwidth may also be divided into multiple sub-bands, and each sub-band may cover a frequency range, e.g., 1.08 MHz.

Each time-frequency resource available for downlink and uplink may be divided into a plurality of resource blocks. Each resource block may cover 12 subcarriers in one slot and may include multiple resource units. Each resource element may cover one subcarrier in one symbol period and may be used to transmit one modulation symbol, which may be real or complex valued.

Fig. 3 shows two exemplary subframe formats 310 and 320 with a normal cyclic prefix for downlink in LTE. The subframe for downlink may include a control region followed by a data region, and the subframe may be time division multiplexed. The control region may include the first M symbol periods of the subframe, where M may be equal to 1, 2, 3, or 4. M may be different between sub-frames and may be transmitted in the first symbol period of a sub-frame. The control region may carry control information, such as control messages. The data region may include the remaining 2L-M symbol periods of the subframe and may carry data and/or other information.

In LTE, an eNB may transmit a Physical Control Format Indicator Channel (PCFICH), a physical hybrid ARQ indicator channel (PHICH), and a Physical Downlink Control Channel (PDCCH) in a control region of a subframe. The PCFICH may convey the size of the control region (e.g., the value of M). The PHICH may carry positive Acknowledgements (ACKs) and Negative Acknowledgements (NACKs) for data transmissions sent on the uplink with hybrid automatic repeat request (HARQ). The PDCCH may carry downlink grants, uplink grants, and/or other control information. The eNB may also transmit a Physical Downlink Shared Channel (PDSCH) in a data region of the subframe. The PDSCH may carry data of the UE that is scheduled for data transmission on the downlink.

Subframe format 310 may be for an eNB equipped with two antennas. Cell-specific reference signals (CRS) may be transmitted from antennas 0 and 1 in symbol periods 0, 4, 7, and 11. The reference signal is a signal known a priori by the transmitter and receiver and may also be referred to as a pilot. The CRS is a cell-specific reference signal, and is generated based on, for example, a cell Identification (ID). In FIG. 3, R for the label_aFor a given resource unit, modulation symbols may be transmitted from antenna a on that resource unit, and no modulation symbols may be transmitted from other antennas on that resource unit. Subframe format 320 may be for an eNB equipped with four antennas. CRS may be transmitted from antennas 0 and 1 in symbol periods 0, 4, 7, and 11, and from antennas 2 and 3 in symbol periods 1 and 8. For both subframe formats 310 and 320, the CRS may be transmitted on evenly spaced subcarriers, which may be determined based on the cell ID. Different enbs may transmit the CRSs of their cells on the same or different subcarriers, depending on the cell IDs of these cells. For both subframe formats 310 and 320, resource elements not used for CRS may be used to transmit data or control information.

Fig. 4 shows an exemplary subframe format 400 for the uplink in LTE. The subframe of the uplink may include a control region and a data region, and the subframe may be frequency division multiplexed. The control region may be formed at both edges of the system bandwidth and may have a configurable size. The data region may include all resource blocks not included in the control region.

The UE may be assigned resource blocks in the control region to send control information to the eNB. The UE may also be assigned resource blocks in the data region to send data to the eNB. The UE may send control information on a Physical Uplink Control Channel (PUCCH) in resource blocks 410a and 410b assigned in the control region. The UE may transmit only data or both data and control information on a Physical Uplink Shared Channel (PUSCH) in resource blocks 420a and 420b assigned in the data region. The uplink transmission may span two slots of a subframe and may hop across frequency, as shown in fig. 4.

PCFICH, PDCCH, PHICH, PDSCH, PUCCH, PUSCH, and CRS in LTE are under the heading "Evolved Universal Radio Access (E-UTRA); physical Channels and Modulation ", 3GPP TS 36.211, which is publicly available.

The UE may be located within the coverage of multiple enbs. One of the enbs may be selected to serve the UE. The serving eNB may select based on various criteria such as received signal strength, received signal quality, path loss, and so on. The received signal quality may be quantified by a signal-to-noise-and-interference ratio (SINR) or some other metric.

A UE may operate in a dominant interference scenario (dominant interference scene) where the UE may encounter high interference from one or more interfering enbs. A dominant interference scenario may occur due to restricted association. For example, in fig. 1, UE 120c may be close to femto eNB110 c and may have high received power for eNB110 c. However, UE 120c may not be able to access femto eNB110 c due to restricted association and may then connect to macro eNB110a with lower received power. UE 120c may then encounter high interference from femto eNB110 c on the downlink and may also cause high interference to femto eNB110 c on the uplink.

A dominant interference scenario may also occur due to range extension, a scenario in which a UE connects to an eNB with lower path loss and possibly lower SINR than some other enbs connected to which the UE detects. For example, in fig. 1, UE 120b may be closer to pico eNB110b than macro eNB110a and may have a lower path loss for pico eNB110 b. However, since pico eNB110b has a lower transmit power level than macro eNB110a, UE 120b may have a lower received power for pico eNB110b than for macro eNB110 a. However, it may be desirable for UE 120b to connect to pico eNB110b due to lower path loss. For a given data rate for UE 120b, the range extension may result in less interference on the uplink. The range extension may also provide cell splitting gain on the downlink, as multiple pico enbs may serve UEs that may otherwise be served by a macro eNB. Range extension may thus improve overall network performance.

Interference significant scenarios may also occur due to relay operations. For example, a relay eNB may have a good access link to UEs and a poor backhaul link to a donor (donor) eNB serving the relay eNB. The UE may then communicate directly with the donor eNB due to the poor backhaul link of the relay eNB. The UE may then encounter high interference from the relay eNB on the downlink and may cause high interference to the relay eNB on the uplink. The dominant interference scenario may also occur when a relay eNB is used for range extension, similar to the case of range extension for pico enbs.

In one aspect, communications in a dominant interference scenario may be supported with TDM partitioning of downlink control resources used to transmit control information on the downlink. For TDM partitioning, different enbs may be allocated different time resources. Each eNB may transmit its control information in its allocated time resources, which may have reduced interference (e.g., no interference) from a strong interfering eNB. Each eNB may avoid transmitting control information in time resources allocated to other enbs (or may transmit control information at a lower transmit power level) and may avoid causing high interference to other enbs. This may enable the UE to communicate with a weaker serving eNB in the presence of a strong interfering eNB. An eNB may be classified as "weak" or "strong" based on the eNB received power at the UE (and not based on the eNB transmit power level).

In one design, the TDM partitioning of downlink control resources may be performed at a subframe level. In this design, different enbs may be assigned different sets of subframes. Each eNB may transmit its control information in the control region of the subframe allocated to that eNB. Each eNB may refrain from transmitting control information in the control region of subframes allocated to other enbs (or may transmit control information at a lower transmit power level).

Fig. 5 illustrates an exemplary interlace structure 500, which may be used for each of the downlink and uplink for FDD in LTE. As shown in FIG. 5, Q interlaces may be defined with indices of 0 through Q-1, where Q may be equal to 4, 6, 8, 10, or some other value. Each interlace may include subframes spaced apart by Q frames. Specifically, interlace Q may include subframes Q, Q +2Q, etc., where Q ∈ { 0., Q-1 }.

In one design, different enbs may be assigned different interlaces. For example, eight interlaces may be defined, two interlaces 0 and 4 may be allocated for pico eNB110b in fig. 1, and the remaining six interlaces may be allocated for macro eNB110 a. Pico eNB110b may transmit its control information in the control regions of subframes in interlaces 0 and 4 and may avoid transmitting control information in the control regions of subframes in the other six interlaces. In contrast, macro eNB110a may transmit its control information in the control regions of subframes in interlaces 1, 2, 3, 5, 6, and 7, and may avoid transmitting control information in the control regions of subframes in the other two interlaces.

Different enbs may also be assigned different sets of subframes defined in other ways. In general, the available subframes may be allocated to any number of enbs, and each eNB may be allocated any set of subframes. Different enbs may be allocated the same or different number of subframes. Each eNB may transmit its control information in the control region of the subframe allocated to it and may refrain from transmitting control information in the control regions of other subframes (or transmitting control information at a lower transmit power level).

As described above, the control region of the subframe may have a configurable size of M symbol periods. Because the control region size may vary, the interfering eNB may not know the size of the control region used by the weaker eNB. In one design, the interfering eNB may assume the largest possible control region size, which may be three symbol periods for a system bandwidth of 5MHz or greater in LTE. The interfering eNB may then avoid transmitting data or control information within the control region of the assumed size. In another design, each eNB may have a configured control region size, which may be determined via negotiation between enbs or may be assigned by a designated network entity. The interfering eNB may then clear (clear) the control region of the other eNB within a number of symbol periods determined by the configured control region size of the other eNB.

In another design, the TDM partitioning of the downlink control resources may be performed at the symbol level. In this design, different enbs may be allocated different symbol periods in each subframe control region. Each eNB may transmit its control information in one or more symbol periods allocated to the eNB in each subframe control region, and may avoid transmitting the control information in the remaining symbol periods of the control region. For example, the control region may include M ═ 3 symbol periods, a pico eNB110b in fig. 1 may be allocated symbol period 2 in each subframe control region, and a macro eNB110a may be allocated symbol periods 0 and 1. Pico eNB110b may transmit its control information in symbol period 2 of each subframe and may avoid transmitting control information in symbol periods 0 and 1 of each subframe. In contrast, macro eNB110a may send its control information in symbol periods 0 and 1 of each subframe and may avoid sending control information in symbol period 2 of each subframe. In general, M symbol periods in each subframe control region may be allocated to up to M different enbs. Each eNB may be assigned one or more symbol periods in the control region.

In yet another design, the TDM partitioning of the downlink control resources may be performed at both the subframe and symbol levels. Different enbs may be allocated different symbol periods in the control region of different subframes. For example, eight interlaces may be defined and the control region may include M-3 symbol periods. Macro eNB110a of fig. 1 may be allocated all three symbols in the control region of the subframes in interlaces 0, 2, 4, and 6, and macro eNB110a may be allocated symbol period 0 in the control region of each remaining subframe. Pico eNB110b may be allocated symbol periods 1 and 2 in the control region of the subframes in interlaces 1, 3, 5, and 7.

The TDM partitioning of the downlink control resources may also be performed in other manners, e.g., based on other units of time. In one design, different enbs that may potentially cause high interference to each other may be pre-allocated with different time resources, e.g., by a designated network entity. In another design, the enbs may negotiate the TDM partitioning (e.g., via backhaul) to allocate sufficient time resources to each eNB. In general, the TDM partitioning may be static and unchanging, or semi-static and infrequently changing (e.g., changing every 100 milliseconds), or dynamic and frequently changing as needed (e.g., changing every subframe or every radio frame).

In another aspect, communications in a dominant interference scenario may be supported with FDM partitioning of uplink control resources used for sending control information on the uplink. For FDM partitioning, different enbs may be allocated different frequency resources. The UEs served by each eNB may transmit control information in the allocated frequency resources, which may have reduced interference from UEs communicating with other enbs. This may enable each eNB to communicate with its UEs in the presence of strong interfering UEs.

Fig. 6 shows a design of uplink control resource FDM partitioning for three enbs in a dominant interference scenario. In the example shown in fig. 6, band 1 may be used for the uplink of a first eNB (e.g., macro eNB110a in fig. 1) and may have a bandwidth corresponding to the system bandwidth. Frequency band 2 may be used for the uplink of a second eNB (e.g., pico eNB110 b) and may have a smaller bandwidth than frequency band 1. Band 3 may be used for the uplink of the third eNB and may have a smaller bandwidth than band 2.

A UE communicating with a first eNB may transmit a PUCCH in a control region 610 formed near both edges of band 1 and may transmit a PUSCH in a data region 612 in the center of a band. A UE communicating with the second eNB may transmit PUCCH in a control region 620 formed near both edges of band 2 and may transmit PUSCH in a data region 622 in the center of band 2. A UE communicating with the third eNB may transmit PUCCH in the control region 630 formed near both edges of band 3 and may transmit PUSCH in the data region 632 in the center of band 3. The control regions 610, 620, and 630 may be non-overlapping as shown in fig. 6 in order to avoid interference with the uplink control information of the three enbs. The control regions 610, 620, and 630 may be defined by different PUCCH offsets (offsets), and each PUCCH offset may indicate an outer frequency (outer frequency) for the control region of the eNB.

Fig. 6 shows an exemplary design of FDM partitioning of uplink control resources. FDM partitioning may also be performed in other manners. For example, the frequency bands for different enbs may have the same bandwidth, but may be shifted in frequency to avoid control region overlap.

It may be desirable to use TDM partitioning for downlink control resources. This may allow the eNB to transmit PDCCH over the entire system bandwidth and obtain frequency diversity. However, FDM partition may also be used for downlink control resources. It may be desirable to use FDM partitioning for the uplink control resources. This may allow the UE to transmit PUCCH in each subframe to reduce latency. FDM partitioning may not affect the operation of the UE because the PUCCH is typically transmitted in one or several resource blocks in each slot, as shown in fig. 4. However, TDM partitioning may also be used for uplink control resources. For clarity, much of the description below assumes that TDM partitioning is used for downlink control resources and FDM partitioning is used for uplink control resources.

Communication in a dominant interference scenario may also be supported with short-term interference suppression. Interference suppression may eliminate or reduce the transmit power of interfering transmissions, thereby allowing higher received signal quality for the desired transmission. Interference suppression may be short-term and on-demand (e.g., on a subframe-by-subframe or packet-by-packet basis).

Fig. 7 shows a design of a downlink data transmission strategy 700 with interference suppression. The serving eNB may have data to send to the UE and may have knowledge that the UE is experiencing high interference on the downlink. For example, a serving eNB may receive a pilot measurement report from a UE, and the report may indicate and/or identify a strong interfering eNB. The serving eNB may send a Resource Usage Message (RUM) trigger on the PDCCH to the UE. RUM triggers may also be referred to as RUM requests, interference suppression triggers, and so on. A RUM trigger may require the UE to request the eNB to clear or reduce interference on the downlink. The RUM trigger may convey a particular data resource (e.g., a particular sub-band in a particular subframe), a requested priority, and/or other information on which to reduce interference.

A UE served by a serving eNB may receive a RUM trigger and may transmit an uplink RUM (UL-RUM) to an interfering eNB. The interfering eNB may receive other UL-RUMs from other UEs that experience high interference from the interfering eNB. The UL-RUM may also be referred to as a reduce interference request. The UL-RUM may require the interfering eNB to reduce interference on designated data resources and may also transmit a priority of the request, a target interference level for the UE, and/or other information. An interfering eNB may receive UL-RUMs from its neighboring UEs and/or the UE, and may be based on the requestThe buffer status of the interfering eNB, and/or other factors to grant or deny each request for interference reduction. If the request from the UE is granted, the interfering eNB may adjust its transmit power and/or steer its transmissions in order to reduce interference to the UE. The interfering eNB may determine a transmit power level P that it will use on the indicated data resource_DL-DATA。

The interfering eNB may then operate at power level P_DL-RQI-RSTransmitting a downlink resource quality indicator reference signal (DL-RQI-RS), wherein P_DL-RQI-RSMay be equal to P_DL-DATAOr P_DL-DATAA scaled version of (a). The RQI reference signal may also be referred to as a power decision pilot, a Power Decision Pilot Indicator Channel (PDPICH), and so on. The interfering eNB may transmit DL-RQI-RS on DL-RQI-RS resources, which may be paired with designated data resources. For example, R sets of data resources may be available in subframe t, and R corresponding sets of DL-RQI-RS resources may be available in subframe t-x, where x may be a fixed offset. Each set of data resources may correspond to one set of resource blocks, and each set of DL-RQI-RS resources may correspond to one resource block. The interfering eNB may transmit the DL-RQI-RS on DL-RQI-RS resource r', which may correspond to the designated data resource r. Similarly, the serving eNB may receive a UL-RUM from its neighboring UEs and may transmit a DL-RQI-RS in response to the UL-RUM.

In one design, the eNB may transmit its DL-RQI-RS on DL-RQI-RS resources, which may be common to all enbs. The DL-RQI-RS resources may be some resources reserved by all enbs in the data region to transmit DL-RQI-RS, or may be otherwise defined. The DL-RQI-RS resources may include a sufficient number of resource elements to enable accurate SINR estimation. DL-RQI-RS may enable UEs to more accurately estimate the received signal quality of their serving eNB on the indicated data resources.

On the DL-RQI-RS resources, the UE may receive DL-RQI-RS from the serving eNB as well as from the interfering eNB. The UE may estimate SINR for DL-RQII-RS resources of the serving eNB based on the received DL-RQII-RS, and may determine RQI based on the estimated SINR. The RQI may indicate the received signal quality on the designated data resources and may be similar to a Channel Quality Indicator (CQI). The RQI may indicate good received signal quality for the serving eNB on the indicated data resources if the strong-interference eNB reduces interference on these data resources. The UE may transmit RQI on PUCCH to the serving eNB. The serving eNB may receive the RQI from the UE and may schedule the UE for data transmission on assigned data resources, which may include all or a subset of the designated data resources. The serving eNB may select a Modulation and Coding Scheme (MCS) based on the RQI and may process the data according to the selected MCS. The serving eNB may generate a Downlink (DL) grant, which may include assigned data resources, a selected MCS, and so on. The serving eNB may send a downlink grant to the UE on the PUCCH and data to the UE on the PUSCH. The UE may receive a downlink grant and data from the serving eNB and may decode the received data transmission based on the selected MCS. The UE may obtain an ACK if the data is decoded correctly or a NACK if the data is decoded in error and the UE may send the ACK or NACK to the serving eNB on the PUCCH.

Fig. 8 shows a design of a strategy 800 for uplink data transmission with interference suppression. The UE may have data to send to the serving eNB and may send a scheduling request on the PUCCH. The scheduling request may indicate a priority of the request, an amount of data to be transmitted by the UE, and so on. The serving eNB may receive the scheduling request and may send a RQI-RS request on the PDCCH to ask the UE to send an uplink RQI reference signal (UL-RQI-RS). The serving eNB may also send a downlink RUM (DL-RUM) on the PDCCH to request the interfering UE to reduce interference on the designated data resources.

The UE may receive an RQI-RS request from a serving eNB and may also receive one or more DL-RUMs from one or more neighboring enbs. The UE may determine that it will or may use on the designated data resources based on DL-RUMs from all neighboring eNBsTransmit power level P_UL-DATA. The UE may then transmit power level P on UL-RQI-RS resources_UL-RQI-RSTransmitting UL-RQI-RS at the transmission power level P_UL-RQI-RSMay be equal to P_UL-DATAOr P_UL-DATAA scaled version of (a). In one design, the UE may send the UL-RQI-RS on UL-RQI-RS resources, which may be common to all UEs. The UL-RQI-RS resources may be certain resources in the data region that all enbs reserve for UEs to transmit UL-RQI-RS, or may be otherwise defined.

The serving eNB may receive UL-RQI-RS from the UE and from the interfering UE on UL-RQI-RS resources and may estimate SINR of the UE on these resources. The SINR may be good if the interfering UE will clear the indicated data resources. The serving eNB may then schedule the UE on the indicated data resources and may select an MCS for the UE based on the estimated SINR. The serving eNB may generate an uplink grant, which may include a selected MCS, assigned data resources, transmit power levels used for the assigned data resources, and so on. The serving eNB may send an uplink grant on the PDCCH to the UE. The UE may receive the uplink grant, process data based on the selected MCS, and send the data on assigned data resources on a PUSCH. The serving eNB may receive and decode data from the UE, determine ACK or NACK based on the decoding result, and transmit the ACK or NACK to the UE on PHICH.

Fig. 7 illustrates an exemplary message sequence that may be used to support data transmission on the downlink with interference suppression. Fig. 8 illustrates an exemplary message sequence that may be used to support data transmission on the uplink with interference mitigation. Interference mitigation on the downlink and/or uplink may also be supported with other message sequences used to determine data resource usage between enbs. For example, enbs may communicate via a backhaul in order to determine (i) specific downlink data resources and/or transmit power levels to be used by different enbs for downlink interference mitigation and/or (ii) specific uplink data resources and/or transmit power levels to be used by different UEs for uplink interference mitigation.

Fig. 7 and 8 assume that each eNB and each UE can transmit control information in an appropriate subframe. For the strategies in fig. 7 and 8, the eNB should be able to reliably send downlink control messages on the downlink, such as RUM triggers, DL-RUMs, RQI-RS requests, downlink grants, uplink grants, and ACK/NACK feedback, even in a dominant interference scenario. Furthermore, the UE should be able to reliably send uplink control messages such as UL-RUM, scheduling request, RQI, and ACK/NACK feedback on the uplink even in a dominant interference scenario. Reliable transmission of downlink control messages may be achieved with TDM partitioning of downlink control resources as described above. Reliable transmission of uplink control messages may be achieved with FDM partitioning of uplink control resources as also described above.

Fig. 7 and 8 also illustrate exemplary physical channels that may be used for transmitting control messages on the downlink and uplink in LTE. In one design, an eNB may send downlink control messages such as RUM triggers, DL-RUMs, RQI-RS requests, downlink grants, and uplink grants on a PDCCH, and may send ACK/NACK feedback on a PHICH. The eNB may also transmit multiple downlink control messages (e.g., DL-RUM and RQI-RS requests) in the same control message. The eNB may reliably send these downlink control messages in a subframe control region allocated to the eNB, which should have reduced interference (e.g., no interference) from the interfering eNB.

In one design, the UE may send uplink control messages such as UL-RUM, scheduling request, RQI, and ACK/NACK feedback on the PUCCH (as shown in fig. 7 and 8) or with data on the PUSCH (not shown in fig. 7 and 8). The UE may reliably send these uplink control messages in the control region allocated to its serving eNB, where high interference from interfering UEs communicating with neighboring enbs should be cleaned up.

In yet another aspect, cross-subframe control may be used to support data transmission on the downlink and/or uplink, with TDM partitioning of downlink control resources. The control information may be sent in TDM partitions with different enbs allocating different subframes. Each eNB may send control messages in subframes allocated to the eNB to support data transmission. Different enbs may have different timelines for transmitting control messages due to their allocation of different subframes. With cross-subframe control, control information (e.g., grants, ACK/NACK, etc.) may be sent in a first subframe and may be applied for data transmission in a second subframe, which may be a variable number of subframes from the first subframe.

Fig. 9 shows a design of a strategy 900 for downlink data transmission with interference suppression when TDM partitioning is used for downlink control resources. In the example shown in fig. 9, eight interlaces are defined, with interlaces 0 and 4 being allocated for eNB1, interlaces 1 and 5 being allocated for eNB 2, interlaces 2 and 6 being allocated for eNB3, and interlaces 3 and 7 being allocated for eNB 4. Each eNB may transmit control information in a control region of a subframe in an interlace allocated thereto. Each eNB may transmit data in the data region of any subframe and may contend with other enbs for downlink data resources. enbs 1, 2, 3 and 4 serve UEs 1, 2, 3 and 4, respectively. Fig. 9 assumes a delay of 1 subframe between the reception of an incoming message and the transmission of the corresponding outgoing message.

For data transmission on the downlink, enbs 1, 2, 3 and 4 may transmit RUM triggers in the control regions of subframes 0, 1, 2 and 3, respectively, in the interlaces allocated thereto. UEs 1, 2, 3, and 4 may receive RUM triggers from neighboring enbs and may transmit UL-RUMs to their serving enbs in subframes 2, 3, 4, and 5, respectively. These UEs may also transmit these UL-RUMs in the same subframe (e.g., subframe 5). enbs 1, 2, 3 and 4 may receive the UL-RUM from the served UE and may transmit the DL-RQI-RS in subframe 7 on the same downlink resource. UEs 1, 2, 3, and 4 may receive DL-RQI-RSs from these enbs, estimate SINRs, and transmit RQIs to their serving enbs at subframe 9.

enbs 1, 2, 3, and 4 may receive RQIs from UEs 1, 2, 3, and 4, respectively, and may schedule UEs for data transmission on the downlink. Due to the processing delay of 1 subframe, enbs 1, 2, 3 and 4 may transmit downlink grants to UEs 1, 2, 3 and 4 at subframes 12, 13, 14 and 11 of the interlace allocated thereto, respectively. enbs 1, 2, 3, and 4 may transmit data to UEs 1, 2, 3, and 4 in subframes 14 through 17, respectively, which subframes 14 through 17 may be shared by the enbs. UEs 1, 2, 3, and 4 may receive data from their serving eNB in subframes 14 through 17 and may send ACK/NACK feedback in subframes 16 through 19, respectively.

As shown in fig. 9, the eNB may transmit its control information in a subframe of an interlace allocated thereto to avoid high interference to the control information. One or more enbs may transmit data in the same subframe and may adjust their transmit power and/or control their transmission to avoid high interference with the data. With cross-subframe control, a downlink grant may have a variable delay with a corresponding data transmission (rather than being transmitted in the same subframe as the corresponding data transmission as shown in fig. 7). The variable delay may result from allocating different subframes for different enbs to transmit control information. Furthermore, a given downlink grant may apply to data transmission in one or more subframes on the downlink. In the example shown in fig. 9, each eNB may transmit control information in every fourth subframe, and one downlink grant may be applied for data transmission in up to four subframes. In general, if an eNB can transmit control information in every S subframe, one downlink grant may be applied to data transmission in up to S subframes.

The eNB may send a RUM trigger in the subframe allocated for it. The eNB may then send the DL-RQI-RS on the same downlink resources to enable the UE to estimate the SINR that may be expected for subsequent data transmissions on the downlink. There may be a variable delay between the RUM trigger from the eNB and the DL-RQI-RS from the eNB, which may be supported with cross-subframe control.

Fig. 10 shows a design of a scheme 1000 for uplink data transmission with interference suppression when TDM partitioning is used for downlink control resources. The example in fig. 10 assumes four enbs 1, 2, 3, and 4, serving four UEs 1, 2, 3, and 4, respectively. As described above for fig. 9, each eNB may be allocated two of the eight interlaces.

For data transmission on the uplink, UEs 1, 2, 3, and 4 may send scheduling requests to serving enbs 1, 2, 3, and 4, respectively (not shown in fig. 10). eNB1, 2, 3, and 4 may send a DL-RUM to the interfering UE and a RQI-RS request to the served UE in subframes 0, 1, 2, and 3, respectively, of the interlace allocated thereto. UEs 1, 2, 3, and 4 may receive DL-RUMs from neighboring enbs and RQI-RS requests from their serving enbs. UEs 1, 2, 3, and 4 may transmit UL-RQI-RS in subframe 5 on the same uplink resource. enbs 1, 2, 3, and 4 may receive the UL-RQI-RS from the UE, estimate SINR, and select an MCS for UEs 1, 2, 3, and 4, respectively. enbs 1, 2, 3, and 4 may schedule UEs for data transmission on the uplink and may send uplink grants to UEs 1, 2, 3, and 4 in subframes 8, 9, 10, and 7, respectively, of the interlace allocated thereto.

UEs 1, 2, 3, and 4 may transmit data to enbs 1, 2, 3, and 4 in subframes 12 through 15, respectively. enbs 1, 2, 3 and 4 may receive data from the UEs they serve in subframes 12 to 15. Due to the processing delay of 1 subframe, the eNB1 may transmit ACK/NACK for data received from the UE 1 in subframes 12, 13, and 14 in subframe 16, and may transmit ACK/NACK for data received in subframe 15 in subframe 20. The eNB 2 may transmit ACK/NACK for data received from the UE 2 in subframes 12 to 15 in subframe 17. The eNB3 may transmit ACK/NACK for data received from the UE 3 in subframe 12 in subframe 14 and may transmit ACK/NACK for data received in subframes 13, 14 and 15 in subframe 18. The eNB 4 may send ACK/NACK for data received from the UE 4 in subframes 12 and 13 in subframe 15 and may send ACK/NACK for data received in subframes 14 and 15 in subframe 19.

As shown in fig. 10, the eNB may transmit control information in a subframe of an interlace allocated thereto. One or more UEs may send data in the same subframe and may adjust their transmit power and/or control their transmission to avoid high interference with the data. With cross-subframe control, the uplink grant may have a variable delay with the corresponding data transmission. The variable delay may result from allocating different subframes for different enbs to transmit control information. Furthermore, a given uplink grant may apply to data transmission on the uplink in one or more subframes.

The UE may send data transmissions on the uplink in the same subframe. The eNB may send ACK/NACK feedback in different subframes of the interlace allocated to it. With cross-subframe control, the ACK/NACK feedback may have a variable delay with the corresponding data transmission. Further, ACK/NACK feedback for data transmission in a variable number of subframes may be sent in a given subframe.

The eNB may send the DL-RUM and RQI-RS requests in different subframes of the interlace allocated to it. The UE may send UL-RQI-RS on the same uplink resources to enable the eNB to estimate the SINR that may be expected for subsequent data transmissions on the uplink. There may be a variable delay between the DL-RUM and RQII-RS requests from the eNB and the UL-RQII-RS from the UE. The variable delay may be supported with cross-subframe control.

Fig. 9 and 10 illustrate exemplary timelines for cases where four enbs may cause high interference to each other and each eNB may be allocated two interlaces to transmit control information. The eNB may also be assigned fewer or more interlaces to send control information. The eNB may then have different timelines for transmitting various control messages. For downlink data transmission with interference suppression, there may be a variable delay between a downlink grant and the corresponding data transmission on the downlink, as shown in fig. 9. The eNB may send a downlink grant prior to or with data transmission in any subframe assigned to the eNB. For uplink data transmission with interference suppression, there may be a variable delay between an uplink grant and a corresponding data transmission on the uplink, as shown in fig. 10. The eNB may send an uplink grant prior to data transmission in any subframe assigned to the eNB. The eNB may also send ACK/NACK feedback after data transmission in any subframe assigned to the eNB. The specific subframes used by the eNB to send the downlink control messages and ACK/NACK feedback may depend on the interlace allocated to the eNB.

For data transmissions without cross-subframe control (e.g., as shown in fig. 7 and 8), there may be a fixed delay between the various transmissions. For data transmissions with cross-subframe control (e.g., as shown in fig. 9 and 10), there may be a variable delay between the various transmissions. Table 1 lists subframes in which grants, data and ACK/NACK may be sent for different data transmission scenarios. For scenarios with cross-subframe control, the offsets x and y may be variable and may depend on the subframes allocated to the eNB.

TABLE 1

In the examples shown in fig. 9 and 10, each UE is scheduled for data transmission in four subframes. In general, a UE may be scheduled for data transmission in one or more subframes. In one design, a single downlink or uplink grant for data transmission in all scheduled subframes may be sent. In another design, one downlink or uplink grant for data transmission in each scheduled subframe may be sent. The downlink and uplink grants may also be sent in other manners.

As described above, control information may be transmitted in TDM partitions with different enbs allocating different subframes. The eNB may avoid transmitting control information in the control region of subframes allocated to other enbs. However, the eNB may continue to transmit certain designated channels and/or signals in the control and/or data regions of subframes allocated to other enbs. For example, an eNB may transmit CRS in all subframes (i.e., in subframes allocated to the eNB and in subframes allocated to other enbs). The designated channels and/or signals may be used to support operation of legacy UEs that may desire to have these channels and/or signals present and, if not, may not function properly.

In yet another aspect, a UE may perform interference cancellation for one or more designated channels and/or signals in order to improve performance of control information and/or data. For interference cancellation, the UE may estimate interference due to a given channel or signal, cancel the estimated interference, and then recover the desired channel or signal after canceling the estimated interference.

In one design, the UE may perform interference cancellation for CRS, which may be transmitted by each eNB in the control region and the data region of each subframe, e.g., as shown in fig. 3. The CRS from the eNB may cause interference in one or more of the following ways:

● CRS collide for CRS-multiple enbs transmit their CRS on the same resource elements,

● CRS vs. control collisions-one eNB transmits its CRS on the resource elements used by another eNB for control information, and

● CRS collides with data-an eNB transmits its CRS on the resource elements used by another eNB for data.

The UE may perform interference cancellation for CRS versus CRS collisions, CRS versus control collisions, or CRS versus data collisions, or a combination thereof. The UE may determine whether CRS-to-CRS collision has occurred between the CRS of its serving eNB and the CRS of the interfering eNB based on the cell IDs of the serving and interfering enbs. If so, the UE may interference cancel CRS collision for CRS by estimating interference caused by CRS from the interfering eNB and canceling the estimated interference from a received signal at the UE to obtain an interference canceled signal. The UE may then perform channel estimation based on the CRS from the serving eNB in the interference canceled signal. The UE can obtain a more accurate channel estimate for the serving eNB by canceling interference caused by CRS from the interfering eNB.

The UE may interference cancel control collisions for CRS by: the interference caused by the CRS from the interfering eNB is estimated, the estimated interference is cancelled, and the interference cancelled signal (rather than the received signal) is processed to recover the control information transmitted by the serving eNB. The UE may also decode the control information by considering interference from the CRS of the interfering eNB. For example, a UE may decode (i) by giving smaller weights to symbols detected from resource elements used by the interfering eNB to transmit CRS, and (ii) by giving larger weights to symbols detected from other resource elements. The UE may interference cancel data collisions for CRS in a manner similar to the manner in which control collisions are interference cancelled for CRS.

In another design, enbs that may interfere with each other may be assigned cell IDs such that their CRSs are transmitted on different resource elements and thus do not collide. This may improve channel estimation performance of the UE. The UE may perform interference cancellation for CRS versus control collisions and/or CRS versus data collisions.

The wireless network may support operation on one or more carriers in the downlink and one or more carriers in the uplink. A carrier may refer to a range of frequencies used for communication and may be associated with certain characteristics. For example, a carrier may be associated with system information or the like that describes operation on the carrier. The carriers may also be referred to as channels, frequency channels, and so on. The downlink carrier may be referred to as a downlink carrier, and the uplink carrier may be referred to as an uplink carrier.

The techniques described herein may be used for multi-carrier operation. In one design, the techniques described herein may be performed for each downlink carrier and each uplink carrier. For example, the eNB may be assigned a set of subframes on each carrier to transmit control information on the downlink. The eNB may be assigned staggered subframe sets of different downlink carriers so that the eNB may transmit control information in as many subframes as possible. The eNB may also be assigned a frequency range on each uplink carrier to receive control information on the uplink. The eNB may send a RUM trigger, DL-RUM, RQI-RS request, grant, and/or other downlink control message for each downlink carrier in its allocated subframe. The eNB may receive a scheduling request, UL-RUM, and/or other uplink control message for each uplink carrier in its allocated frequency range. The UE may monitor each downlink carrier on which the UE may receive control information and may detect RUM triggers, DL-RUMs, RQI-RS requests, grants, and/or other downlink control messages. The UE may transmit a scheduling request, UL-RUM, and/or other uplink control messages on each uplink carrier in the allocated frequency range of the uplink carrier.

In another design, the eNB may be assigned a set of subframes on a designated downlink carrier to send control information for all downlink carriers. The eNB may also be assigned a frequency range on a designated uplink carrier to receive control information for all uplink carriers. The eNB may send RUM triggers, DL-RUMs, RQI-RS requests, grants, and/or other downlink control messages for all downlink carriers in the allocated subframes on the designated downlink carrier. The eNB may receive a scheduling request, UL-RUM, and/or other uplink control message for all uplink carriers in the assigned frequency range for the designated uplink carrier. The UE may monitor the designated downlink carrier and may detect a RUM trigger, DL-RUM, RQI-RS request, grant, and/or other downlink control message for all downlink carriers. The UE may send scheduling requests, UL-RUMs, and/or other uplink control messages for all uplink carriers in a frequency range that specifies an allocation of uplink carriers.

The techniques described herein may support communication in a dominant interference scenario. In a dominant interference scenario, a UE may reliably receive transmissions from a serving eNB on resources on which the interfering eNB is not transmitting. The interfering eNB may clear (or transmit at a lower power level on) resources used by the serving eNB to transmit control information and resources used by the serving eNB to transmit data. As described above, resources for control information may be statically or semi-statically cleaned with TDM partitioning for downlink and FDM partitioning for uplink. Resources for data may be dynamically cleaned up with short-term interference mitigation, which may assume that control information can be reliably transmitted on the downlink and uplink.

Fig. 11 shows a design of a process 1100 for exchanging data in a wireless network. Process 1100 may be performed by a UE, a base station/eNB, or some other entity. Control information may be exchanged (e.g., transmitted or received) in a first subframe (block 1112). Data may be exchanged in a second subframe based on the control information exchanged in the first subframe (block 1114). The second subframe may be a variable number of subframes from the first subframe. ACK/NACK feedback for the data exchanged in the second subframe may be exchanged in the third subframe (block 1116). The third subframe may also be a variable number of subframes from the second subframe.

In one design, a first subframe may be allocated to a base station and may have reduced interference from at least one interfering base station. The second subframe may be available to the base station and the at least one interfering base station. In one design, the base station may be assigned a set of subframes to send control information. The base station may transmit control information in the set of subframes and may avoid transmitting control information in the remaining subframes. The first subframe may belong to the set of subframes. In another design, the base station may be assigned at least one interlace to send control information. The subframes in the at least one interlace may have reduced interference from at least one interfering base station. The first subframe may belong to the at least one interlace allocated to the base station.

In one design, a base station (e.g., eNB1 in fig. 9) may perform process 1100 to transmit data on the downlink. The base station may send a downlink grant in a first subframe (e.g., subframe 12) in block 1112 and may send data in a second subframe (e.g., subframe 14) in block 1114. The base station may receive ACK/NACK feedback for the data sent in the second subframe in a third subframe (e.g., subframe 16) in block 1116. The base station may send a message (e.g., a RUM trigger) in a fourth subframe (e.g., subframe 0) to request reduced interference on the downlink in the second subframe. The fourth subframe may be a variable number of subframes from the second subframe. The base station may transmit a reference signal (e.g., DL-RQI-RS) in a fifth subframe (e.g., subframe 7), which may be a variable number of subframes from the fourth subframe.

In another design, a UE (e.g., UE 1 in fig. 9) may perform process 1100 to receive data on the downlink. The UE may receive a downlink grant in a first subframe (e.g., subframe 12) in block 1112 and may receive data in a second subframe (e.g., subframe 14) in block 1114. The UE may send ACK/NACK feedback for the data received in the second subframe in a third subframe (e.g., subframe 16) in block 1116.

In yet another design, a base station (e.g., eNB1 in fig. 10) may perform process 1100 to receive data on the uplink. The base station may send an uplink grant in a first subframe (e.g., subframe 8) in block 1112 and may receive data in a second subframe (e.g., subframe 12) in block 1114. The base station may send ACK/NACK feedback in a third subframe (e.g., subframe 16) for the data received in the second subframe. The third subframe may be a variable number of subframes from the second subframe. The base station may transmit a message (e.g., DL-RUM) in a fourth subframe (e.g., subframe 0) to request reduced interference on the uplink in the second subframe. In one design, the fourth subframe may be a variable number of subframes from the second subframe, e.g., as shown in fig. 10. In another design, the fourth subframe may be a fixed number of subframes from the second subframe. The base station may also send a message (e.g., a RQI-RS request) in the fourth subframe to request the UE to send a reference signal (e.g., a UL-RQI-RS) in the fifth subframe (e.g., subframe 5). The fourth subframe may be a variable number of subframes from the fifth subframe. The base station may receive a plurality of reference signals from a plurality of UEs (including the UE) in a fifth subframe. The base station may determine a received signal quality of the UE based on the plurality of reference signals. The base station may select a Modulation and Coding Scheme (MCS) for the UE based on the received signal quality of the UE and may transmit an uplink grant including the selected MCS.

In yet another design, the UE may perform process 1100 to transmit data on the uplink. The UE may receive an uplink grant in a first subframe (e.g., subframe 8) in block 1112 and may send data in a second subframe (e.g., subframe 12) in block 1114. The UE may receive ACK/NACK feedback in a third subframe (e.g., subframe 16) for the data sent in the second subframe.

In one design, operation on multiple carriers may be supported. In one design, grants for data transmission on multiple carriers may be exchanged in block 1112. Data may be exchanged over the multiple carriers indicated by the grant in block 1114.

Fig. 12 shows a design of an apparatus 1200 for exchanging data in a wireless network. The apparatus 1200 includes: a module 1212 for exchanging control information in a first subframe; a module 1214 for exchanging data in a second subframe based on the control information exchanged in the first subframe, wherein the second subframe is a variable number of subframes from the first subframe; and a module 1216 for exchanging ACK/NACK feedback for data exchanged in the second subframe in a third subframe, wherein the third subframe is a variable number of subframes from the second subframe.

Fig. 13 shows a design of a process 1300 for exchanging data in a wireless network. Process 1300 may be performed by a UE, a base station/eNB, or some other entity. At least one grant for the UE may be exchanged (e.g., sent or received) (block 1312). Data may then be exchanged in a variable number of subframes indicated by the at least one grant (block 1314).

In one design of block 1312, the at least one grant may be exchanged in subframes allocated to a base station and having reduced interference from at least one interfering base station. In one design, the base station may be allocated a set of subframes out of all available subframes to send control information. The base station may send grants in this set of subframes to UEs experiencing high interference and may avoid sending grants in the remaining subframes to these UEs. Each grant may cover data transmission in a single subframe or multiple subframes.

In one design, for example as shown in fig. 9, a base station may perform process 1300 to transmit data to a UE on the downlink. The base station may send at least one downlink grant to the UE in block 1312 and may send data to the UE in a variable number of subframes in block 1314.

In another design, the UE may perform process 1300 to receive data from the base station on the downlink, e.g., as shown in fig. 9. The UE may receive at least one downlink grant in block 1312 and may receive data in a variable number of subframes in block 1314.

In yet another design, for example as shown in fig. 10, the base station may perform process 1300 to receive data from the UE on the uplink. The base station may send at least one uplink grant to the UE in block 1312 and may receive data from the UE in a variable number of subframes in block 1314.

In yet another design, the UE may perform process 1300 to transmit data on the downlink to the base station, e.g., as shown in fig. 10. The UE may receive at least one uplink grant in block 1312 and may transmit data in a variable number of subframes in block 1314.

In one design, multiple grants, one for data transmission in each of a variable number of subframes, may be sent to the UE in block 1312. The multiple grants may be sent in a single subframe or in multiple subframes (e.g., one subframe for each subframe in which data is sent). In one design, each grant may include an indication of a subframe to which the grant applies. The indication may be given explicitly by a field in the grant or implicitly by the resource on which the grant is sent or the scrambling code used for the grant, etc. In another design, a single grant for data transmission in all of the variable number of subframes may be sent to the UE in block 1312.

Fig. 14 shows a design of an apparatus 1400 for exchanging data in a wireless network. The apparatus 1400 comprises: a module 1412 for exchanging at least one grant for the UE; and a module 1414 for exchanging data in a variable number of subframes indicated by the at least one grant.

Fig. 15 shows a design of a process 1500 for exchanging data in a wireless network. Process 1500 may be performed by a base station/eNB (as described below) or some other entity. The base station may send a message on the PDCCH requesting reduced interference (block 1512). Thereafter, the base station may exchange (e.g., transmit or receive) data on resources having reduced interference due to the message transmitted on the PDCCH (block 1514).

In one design, a base station may perform process 1500 to transmit data on the downlink, e.g., as shown in fig. 7. For block 1512, the base station may send a message (e.g., a RUM trigger) on the PDCCH requesting reduced interference from the at least one interfering base station. For block 1514, the base station may transmit data to the UE on resources with reduced interference from the at least one interfering base station due to the message transmitted on the PDCCH. The base station may transmit a downlink grant on the PDCCH to the UE and may transmit data to the UE based on the downlink grant.

In another design, such as shown in fig. 8, the base station may perform process 1500 to receive data on the uplink. For block 1512, the base station may send a message (e.g., a DL-RUM) on the PDCCH requesting reduced interference from at least one interfering UE communicating with at least one neighboring base station. For block 1514, the base station may receive data from the UE on resources having reduced interference from the at least one interfering UE due to the message sent on the PDCCH. In one design, the base station may send a second message (e.g., a RQI-RS request) on the PDCCH requesting the UE to send a reference signal (e.g., a UL-RQI-RS). The base station may receive a plurality of reference signals from a plurality of UEs including the UE, and may estimate received signal quality of the UE based on the reference signals. The base station may determine a Modulation and Coding Scheme (MCS) based on the estimated received signal quality of the UE. The base station may generate an uplink grant including the selected MCS, transmit the uplink grant on the PDCCH to the UE, and receive data transmitted by the UE based on the uplink grant.

In one design, multi-carrier operation may be supported. In one design, a base station may send a message on each of multiple carriers on the PDCCH. Each message may request reduced interference on the carrier on which the message is sent. In another design, the base station may send the message on a PDCCH on a designated carrier of multiple carriers. Each message may request reduced interference on one or more of the plurality of carriers.

Fig. 16 shows a design of an apparatus 1600 for exchanging data in a wireless network. The apparatus 1600 includes: a module 1612 for sending a message on PDCCH requesting reduced interference; and a module 1614 for exchanging data on resources with reduced interference due to the message sent on the PDCCH.

Fig. 17 shows a design of a process 1700 for exchanging data in a wireless network. Process 1700 may be performed by a UE (as described below) or some other entity. The UE may monitor for a message sent on the PDCCH by at least one base station to request reduced interference (block 1712). The UE may exchange (e.g., transmit or receive) data on resources with reduced interference due to the message sent on the PDCCH by the at least one base station (block 1714).

In one design, the UE may perform process 1700 to receive data on the downlink, e.g., as shown in fig. 7. The UE may receive data from the serving base station on resources with reduced interference from at least one neighboring base station. In one design, the UE may receive a first message (e.g., a RUM trigger) sent by a neighboring base station on a PDCCH to request reduced interference. The UE may send a second message (e.g., a UL-RUM) to the serving base station to forward the request for reduced interference from the neighboring base station. In another design, the UE may receive a first message sent by the serving base station on a PDCCH to request reduced interference. The UE may send a second message to the at least one neighboring base station to forward the request for reduced interference from the serving base station. In one design, a UE may receive multiple reference signals (e.g., DL-RQI-RS) from multiple base stations including a serving base station and at least one neighboring base station. The UE may estimate a received signal quality of the serving base station based on the plurality of reference signals. The UE may send an RQI indicating the received signal quality of the serving base station.

In another design, the UE may perform process 1700 to transmit data on the uplink, e.g., as shown in fig. 8. The UE may transmit data to the serving base station on resources with reduced interference from at least one interfering UE communicating with at least one neighboring base station. In one design, the UE may receive at least one message (e.g., a DL-RUM) sent on a PDCCH by at least one neighboring base station to request reduced interference. The UE may determine whether to transmit data on the resources based on the at least one message received from the at least one neighboring base station. The UE may receive a message (e.g., RQI-RS request) sent on the PDCCH by the serving base station to request transmission of a reference signal. The UE may determine a first transmit power level for the resource in response to the at least one message from the at least one neighboring base station and the message from the serving base station. The UE may then transmit a reference signal (e.g., UL-RQI-RS) at a second transmit power level determined based on the first transmit power level.

In one design, multi-carrier operation may be supported. In one design, the UE may monitor for messages from the at least one base station on each of a plurality of carriers. In another design, the UE may monitor for messages from the at least one base station on a designated carrier of the multiple carriers.

Fig. 18 shows a design of an apparatus 1800 for exchanging data in a wireless network. The apparatus 1800 includes: means 1812 for monitoring messages sent on PDCCH by at least one base station to request reduced interference; and means 1814 for exchanging data on resources with reduced interference due to the message sent on the PDCCH by the at least one base station.

The modules in fig. 12, 14, 16, and 18 may comprise processors, electronics devices, hardware devices, electronics components, logic circuits, memories, software codes, firmware codes, etc., or any combination thereof.

Fig. 19 shows a block diagram of a design of base station/eNB 110 and UE 120, which base station/eNB 110 and UE 120 may be one of the base stations/enbs in fig. 1 and one of the UEs in fig. 1. Base station 110 may be equipped with T antennas 1934a through 1934T and UE 120 may be equipped with R antennas 1952a through 1952R, where T ≧ 1 and R ≧ 1 in general.

At base station 110, a transmit processor 1920 can receive data from a data source 1912 and can receive control information from a controller/processor 1940. The control information may include control messages such as RUM triggers, DL-RUMs, RQI-RS requests, downlink grants, uplink grants, and the like. Processor 1920 may process (e.g., encode and modulate) the data and control information to obtain data symbols and control symbols, respectively. Processor 1920 may also generate reference symbols, e.g., for CRS, DL-RQI-RS, etc. A Transmit (TX) multiple-input multiple-output (MIMO) processor 1930 may spatially process (e.g., precode) the data symbols, the control symbols, and/or the reference symbols, if applicable, and may provide T output symbol streams to T Modulators (MODs) 1932a through 1932T. Each modulator 1932 may process a respective output symbol stream (e.g., for OFDM, etc.) to obtain an output sample stream. Each modulator 1932 may further process (e.g., convert to analog, amplify, filter, and upconvert) the output sample stream to obtain a downlink signal. T downlink signals from modulators 1932a through 1932T may be transmitted via T antennas 1934a through 1934T, respectively.

At UE 120, antennas 1952a through 1952r may receive downlink signals from base station 110 and other base stations and may provide received signals to demodulators (DEMODs) 1954a through 1954r, respectively. Each demodulator 1954 may condition (e.g., filter, amplify, downconvert, and digitize) a respective received signal to obtain input samples. Each demodulator 1954 may further process the input samples (e.g., for OFDM, etc.) to obtain received symbols. A MIMO detector 1956 may obtain received symbols from all R demodulators 1954a through 1954R, perform MIMO detection on the received symbols if applicable, and provide detected symbols. A receive processor 1958 may process (e.g., demodulate and decode) the detected symbols, provide decoded data for UE 120 to a data sink 1960, and provide decoded control information to a controller/processor 1980.

On the uplink, at UE 120, a transmit processor 1964 may receive data from a data source 1962 and may receive control information from a controller/processor 1980. The control information may include control messages such as scheduling requests, UL-RUMs, RQIs, etc. A processor 1964 may process (e.g., encode and modulate) the data and control information to obtain data symbols and control symbols, respectively. Processor 1964 may also generate reference symbols, e.g., for UL-RQI-RS. The symbols from transmit processor 1964 may be processed by a TX MIMO processor 1966 if applicable, further processed by modulators 1954a through 1954r (e.g., for SC-FDM, OFDM, etc.), and transmitted to base station 110 and possibly other base stations. At base station 110, the uplink signals from UE 120 and other UEs may be received by antennas 1934, processed by demodulators 1932, detected by a MIMO detector 1936 (if applicable), and further processed by a receive processor 1938 to obtain the decoded data and control information transmitted by UE 120 and other UEs. Processor 1938 can provide decoded data to a data sink 1939 and decoded control information to controller/processor 1940.

Controllers/processors 1940 and 1980 may direct operation at base station 110 and UE 120, respectively. Processor 1940 and/or other processors and modules at base station 110 may perform or direct process 1100 in fig. 11, process 1300 in fig. 13, process 1500 in fig. 15, and/or other processes for the techniques described herein. Processor 1980 and/or other processors and modules at UE 120 may perform or direct process 1100 in fig. 11, process 1300 in fig. 13, process 1700 in fig. 17, and/or other processes for the techniques described herein. Memories 1942 and 1982 may store data and program codes for base station 110 and UE 120, respectively. A scheduler 1944 may schedule UEs for data transmission on the downlink and/or uplink.

Those of skill in the art would understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

Those of skill would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the disclosure herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure.

The various illustrative logical blocks, modules, and circuits described in connection with the disclosure herein may be implemented or performed with a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

The steps of a method or algorithm described in connection with the disclosure herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In the alternative, the processor and the storage medium may reside as discrete components in a user terminal.

In one or more exemplary designs, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A storage media may be any available media that can be accessed by a general purpose or special purpose computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to carry or store desired program code means in the form of instructions or data structures and which can be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, Digital Subscriber Line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. Disk and disc, as used herein, includes Compact Disc (CD), laser disc, optical disc, Digital Versatile Disc (DVD), floppy disk and blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

The previous description of the disclosure is provided to enable any person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations without departing from the spirit or scope of the disclosure. Thus, the disclosure is not intended to be limited to the examples and designs described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (73)

1. A method for wireless communication, comprising:

exchanging control information in a first subframe; and

exchanging data in a second subframe, the second subframe being a variable number of subframes from the first subframe, based on the control information exchanged in the first subframe.

2. The method of claim 1, further comprising:

exchanging acknowledgement/negative acknowledgement (ACK/NACK) feedback for the data exchanged in the second subframe in a third subframe, the third subframe being a variable number of subframes from the second subframe.

3. The method of claim 1, wherein the first subframe is allocated to a base station and has reduced interference from at least one interfering base station, and wherein the second subframe is available to the base station and the at least one interfering base station.

4. The method of claim 1, further comprising:

determining a set of subframes allocated to a base station for transmitting control information and having reduced interference from at least one interfering base station, wherein the first subframe is in the set of subframes.

5. The method of claim 1, further comprising:

determining at least one interlace allocated to a base station for transmitting control information, wherein subframes in the at least one interlace have reduced interference from at least one interfering base station, and wherein the first subframe belongs to the at least one interlace allocated to the base station.

6. The method of claim 1, wherein the exchanging control information comprises: transmitting a downlink grant in the first subframe, and wherein the exchanging data comprises: transmitting data in the second subframe.

7. The method of claim 1, wherein the exchanging control information comprises: receiving a downlink grant in the first subframe, and wherein the exchanging data comprises: receiving data in the second subframe.

8. The method of claim 1, wherein the exchanging control information comprises: transmitting an uplink grant in the first subframe, and wherein the exchanging data comprises: receiving data in the second subframe.

9. The method of claim 1, wherein the exchanging control information comprises: receiving an uplink grant in the first subframe, and wherein the exchanging data comprises: transmitting data in the second subframe.

10. The method of claim 1, further comprising:

transmitting a message in a third subframe to request reduced interference on a downlink in the second subframe, the third subframe being a variable number of subframes from the second subframe.

11. The method of claim 10, further comprising:

transmitting a reference signal in a fourth subframe, the fourth subframe being a variable number of subframes from the third subframe.

12. The method of claim 1, further comprising:

transmitting a message in a third subframe to request reduced interference on uplink in the second subframe, the third subframe being a variable number of subframes from the second subframe.

13. The method of claim 1, further comprising:

transmitting a message in a third subframe to request a User Equipment (UE) to transmit a reference signal in a fourth subframe, the third subframe being a variable number of subframes from the fourth subframe.

14. The method of claim 13, further comprising:

receiving a plurality of reference signals from a plurality of User Equipments (UEs) including the UE in the fourth subframe; and

determining a received signal quality of the UE based on the plurality of reference signals.

15. The method of claim 1, wherein the exchanging control information comprises: exchanging grants for data transmission on a plurality of carriers, and wherein the exchanging data comprises: exchanging data over the plurality of carriers indicated by the grant.

16. An apparatus for wireless communication, comprising:

means for exchanging control information in a first subframe; and

means for exchanging data in a second subframe based on the control information exchanged in the first subframe, the second subframe being a variable number of subframes from the first subframe.

17. The apparatus of claim 16, further comprising:

means for exchanging acknowledgement/negative acknowledgement (ACK/NACK) feedback for the data exchanged in the second subframe in a third subframe, the third subframe being a variable number of subframes from the second subframe.

18. The apparatus of claim 16, further comprising:

means for transmitting a message in a third subframe to request reduced interference on a downlink in the second subframe, the third subframe being a variable number of subframes from the second subframe.

19. The apparatus of claim 18, further comprising:

means for transmitting a reference signal in a fourth subframe, the fourth subframe being a variable number of subframes from the third subframe.

20. The apparatus of claim 16, further comprising:

means for transmitting a message in a third subframe to request reduced interference on uplink in the second subframe, the third subframe being a variable number of subframes from the second subframe.

21. An apparatus for wireless communication, comprising:

at least one processor configured to: exchanging control information in a first subframe; and exchanging data in a second subframe based on the control information exchanged in the first subframe, the second subframe being a variable number of subframes from the first subframe.

22. The apparatus of claim 21, wherein the at least one processor is configured to exchange positive acknowledgement/negative acknowledgement (ACK/NACK) feedback for the data exchanged in the second subframe in a third subframe, the third subframe being a variable number of subframes from the second subframe.

23. The apparatus of claim 21, wherein the at least one processor is configured to send a message in a third subframe to request reduced interference on downlink in the second subframe, the third subframe being a variable number of subframes from the second subframe.

24. The apparatus of claim 23, wherein the at least one processor is configured to send reference signals in a fourth subframe, the fourth subframe being a variable number of subframes from the third subframe.

25. The apparatus of claim 21, wherein the at least one processor is configured to send a message in a third subframe to request reduced interference on uplink in the second subframe, the third subframe being a variable number of subframes from the second subframe.

26. A computer program product, comprising:

a computer readable medium, the computer readable medium comprising:

code for causing at least one computer to exchange control information in a first subframe, and

code for causing the at least one computer to exchange data in a second subframe based on the control information exchanged in the first subframe, the second subframe being a variable number of subframes from the first subframe.

27. A method for wireless communication, comprising:

exchanging at least one grant for a User Equipment (UE); and

exchanging data in a variable number of subframes indicated by the at least one grant.

28. The method of claim 27, wherein the exchanging at least one permit comprises: the at least one grant is exchanged in subframes allocated to a base station and having reduced interference from at least one interfering base station.

29. The method of claim 28, wherein the base station is allocated a set of subframes of all available subframes for transmitting control information, and wherein the base station transmits grants to high-interference-encountering UEs in the set of subframes and does not transmit grants to the high-interference-encountering UEs in remaining subframes.

30. The method of claim 27, wherein the exchanging at least one permit comprises: transmitting at least one downlink grant to the UE, and wherein the exchanging data comprises: transmitting data to the UE in the variable number of subframes.

31. The method of claim 27, wherein the exchanging at least one permit comprises: receiving at least one downlink grant at the UE, and wherein the exchanging data comprises: receiving data in the variable number of subframes at the UE.

32. The method of claim 27, wherein the exchanging at least one permit comprises: transmitting at least one uplink grant to the UE, and wherein the exchanging data comprises: receiving data from the UE in the variable number of subframes.

33. The method of claim 27, wherein the exchanging at least one permit comprises: receiving at least one uplink grant at the UE, and wherein the exchanging data comprises: transmitting data from the UE in the variable number of subframes.

34. The method of claim 27, wherein the exchanging at least one permit comprises: transmitting a plurality of grants to the UE, one grant for data transmission in each of the variable number of subframes.

35. The method of claim 34, wherein the plurality of grants are transmitted in a single subframe.

36. The method of claim 34, wherein each grant comprises an indication of a subframe to which the grant applies, the indication being given by a field in the grant or by a resource on which the grant is sent or a scrambling code used for the grant.

37. The method of claim 27, wherein the exchanging at least one permit comprises: transmitting a single grant for data transmission in all of the variable number of subframes.

38. An apparatus for wireless communication, comprising:

means for exchanging at least one grant for a User Equipment (UE); and

means for exchanging data in a variable number of subframes indicated by the at least one grant.

39. The apparatus of claim 38, wherein the means for exchanging at least one grant comprises means for receiving at least one downlink grant at the UE, and wherein the means for exchanging data comprises means for receiving data in the variable number of subframes at the UE.

40. The apparatus of claim 38, wherein the means for exchanging at least one grant comprises means for receiving at least one uplink grant at the UE, and wherein the means for exchanging data comprises means for transmitting data from the UE in the variable number of subframes.

41. The apparatus of claim 38, wherein the means for exchanging at least one grant comprises means for sending a plurality of grants to the UE, one grant for data transmission in each of the variable number of subframes.

42. The apparatus of claim 38, wherein the means for exchanging at least one grant comprises means for sending a single grant for data transmission in all of the variable number of subframes.

43. An apparatus for wireless communication, comprising:

at least one processor configured to: exchanging at least one grant for a User Equipment (UE); and exchanging data in a variable number of subframes indicated by the at least one grant.

44. A computer program product, comprising:

a computer readable medium, the computer readable medium comprising:

code for causing at least one computer to exchange at least one grant for a User Equipment (UE), and

code for causing the at least one computer to exchange data in a variable number of subframes indicated by the at least one grant.

45. A method for wireless communication, comprising:

transmitting a message on a Physical Downlink Control Channel (PDCCH) requesting reduced interference; and

exchanging data on resources having reduced interference due to the message sent on the PDCCH.

46. The method of claim 45, wherein the sending the message comprises: transmitting, by a base station, the message on a PDCCH to request reduced interference from at least one interfering base station, and wherein the exchanging data comprises: transmitting data to a User Equipment (UE) on the resource with reduced interference from the at least one interfering base station due to the message transmitted on the PDCCH.

47. The method of claim 46, further comprising:

transmitting a downlink grant to the UE on the PDCCH, wherein data is transmitted to the UE based on the downlink grant.

48. The method of claim 45, wherein the sending the message comprises: transmitting, by a base station, the message on a PDCCH to request reduced interference from at least one interfering User Equipment (UE) in communication with at least one neighboring base station, and wherein the exchanging data comprises: receiving data from the UE on the resource with reduced interference from the at least one interfering UE due to the message sent on the PDCCH.

49. The method of claim 48, further comprising:

transmitting an uplink grant to the UE on a PDCCH, wherein data is transmitted by the UE based on the uplink grant.

50. The method of claim 45, further comprising:

transmitting a second message on the PDCCH to request a User Equipment (UE) to transmit a reference signal;

receiving a plurality of reference signals from a plurality of UEs including the UE;

estimating a received signal quality of the UE based on the plurality of reference signals; and

determining a modulation and coding scheme for the data exchanged on the resources based on the estimated received signal quality of the UE.

51. The method of claim 45, further comprising:

transmitting a message on each of a plurality of carriers on the PDCCH, each message requesting reduced interference on the carrier on which the message is transmitted.

52. The method of claim 45, further comprising:

transmitting messages on a PDCCH on designated carriers of a plurality of carriers, each message requesting reduced interference on one or more of the plurality of carriers.

53. An apparatus for wireless communication, comprising:

means for transmitting a message on a Physical Downlink Control Channel (PDCCH) requesting reduced interference; and

means for exchanging data on resources with reduced interference due to the message sent on the PDCCH.

54. The apparatus of claim 53, wherein the means for transmitting the message comprises means for transmitting the message on a PDCCH by a base station to request reduced interference from at least one interfering base station, and wherein the means for exchanging data comprises means for transmitting data to a User Equipment (UE) on the resource with reduced interference from the at least one interfering base station due to the message transmitted on the PDCCH.

55. The apparatus of claim 53, wherein the means for transmitting the message comprises means for transmitting the message on a PDCCH by a base station to request reduced interference from at least one interfering User Equipment (UE) in communication with at least one neighboring base station, and wherein the means for exchanging data comprises means for receiving data from a UE on the resource with reduced interference from the at least one interfering UE due to the message transmitted on the PDCCH.

56. The apparatus of claim 53, further comprising:

means for transmitting a second message on the PDCCH requesting a User Equipment (UE) to transmit a reference signal;

means for receiving a plurality of reference signals from a plurality of UEs including the UE;

means for estimating a received signal quality of the UE based on the plurality of reference signals; and

means for determining a modulation and coding scheme for the data exchanged on the resource based on the estimated received signal quality of the UE.

57. An apparatus for wireless communication, comprising:

at least one processor configured to transmit a message on a Physical Downlink Control Channel (PDCCH) requesting reduced interference; and exchanging data on resources having reduced interference due to the message sent on the PDCCH.

58. A computer program product, comprising:

a computer readable medium, the computer readable medium comprising:

code for causing at least one computer to transmit a message on a Physical Downlink Control Channel (PDCCH) requesting reduced interference; and

code for causing the at least one computer to exchange data on resources having reduced interference due to the message sent on the PDCCH.

59. A method for wireless communication, comprising:

monitoring messages sent by at least one base station on a Physical Downlink Control Channel (PDCCH) to request reduced interference; and

exchanging data on resources having reduced interference due to the message sent on the PDCCH by the at least one base station.

60. The method of claim 59, wherein the exchanging data comprises: receiving data from a serving base station on the resource with reduced interference from at least one neighboring base station.

61. The method of claim 60, further comprising:

receiving a first message sent by a neighboring base station on a PDCCH to request reduced interference; and

transmitting a second message to the serving base station to forward the request for reduced interference from the neighboring base station.

62. The method of claim 60, further comprising:

receiving a first message sent by the serving base station on a PDCCH to request reduced interference; and

transmitting a second message to the at least one neighboring base station to forward the request for reduced interference from the serving base station.

63. The method of claim 59, further comprising:

receiving a plurality of reference signals from a plurality of base stations including a serving base station and at least one neighbor base station;

estimating a received signal quality of the serving base station based on the plurality of reference signals; and

transmitting a Resource Quality Indicator (RQI) indicating the received signal quality of the serving base station.

64. The method of claim 59, wherein the exchanging data comprises: transmitting data to a serving base station on the resources with reduced interference from at least one interfering User Equipment (UE) communicating with at least one neighboring base station.

65. The method of claim 59, further comprising:

receiving at least one message sent by at least one neighboring base station on a PDCCH to request reduced interference;

receiving a message sent by a serving base station on a PDCCH to request transmission of a reference signal;

determining a first transmit power level for the resource in response to the at least one message from the at least one neighboring base station and the message from the serving base station; and

transmitting a reference signal at a second transmit power level determined based on the first transmit power level.

66. The method of claim 59, further comprising:

receiving at least one message transmitted on the PDCCH by at least one neighboring base station to request reduced interference; and

determining whether to transmit data on the resources based on the at least one message received from the at least one neighboring base station.

67. The method of claim 59, wherein the monitoring message comprises:

monitoring messages from the at least one base station on each of a plurality of carriers.

68. The method of claim 59, wherein the monitoring message comprises:

monitoring for messages from the at least one base station on a designated carrier of a plurality of carriers.

69. An apparatus for wireless communication, comprising

Means for monitoring messages sent by at least one base station on a Physical Downlink Control Channel (PDCCH) to request reduced interference; and

means for exchanging data on resources with reduced interference due to the message sent on the PDCCH by the at least one base station.

70. The apparatus of claim 69, further comprising:

means for receiving a first message sent by a neighboring base station on a PDCCH to request reduced interference; and

means for transmitting a second message to a serving base station to forward a request for reduced interference from the neighboring base station.

71. The apparatus of claim 69, further comprising:

means for receiving at least one message sent by at least one neighboring base station on a PDCCH to request reduced interference;

means for receiving a message sent on a PDCCH by a serving base station to request transmission of a reference signal;

means for determining a first transmit power level for the resource in response to the at least one message from the at least one neighboring base station and the message from the serving base station; and

means for transmitting a reference signal at a second transmit power level determined based on the first transmit power level.

72. An apparatus for wireless communication, comprising

At least one processor configured to: monitoring messages sent by at least one base station on a Physical Downlink Control Channel (PDCCH) to request reduced interference; and exchanging data on resources having reduced interference due to the message sent on the PDCCH by the at least one base station.

73. A computer program product, comprising:

a computer readable medium, the computer readable medium comprising:

code for causing at least one computer to monitor messages sent by at least one base station on a Physical Downlink Control Channel (PDCCH) to request reduced interference; and

code for causing the at least one computer to exchange data on resources having reduced interference due to the message sent on the PDCCH by the at least one base station.