HK1177842B - Evolved node b channel quality indicator (cqi) processing for heterogeneous networks - Google Patents

Description

Evolved node-B Channel Quality Indicator (CQI) processing for heterogeneous networks

Cross Reference to Related Applications

This application claims the benefit of U.S. provisional patent application S/n.61/323,813, filed on 13/4/2010, which is incorporated herein by reference.

Background

I. Field of the invention

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

II. background

Wireless communication networks are widely deployed to provide various communication services 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 a number of base stations capable of supporting communication for a number of 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 and control information to a UE on the downlink and/or may receive data and control information from a UE on the uplink. On the downlink, transmissions from a base station may observe interference due to transmissions from neighbor base stations. On the uplink, transmissions from a UE may cause interference to transmissions from other UEs communicating with neighbor base stations. Interference may degrade performance on both the downlink and uplink.

SUMMARY

Certain aspects of the present disclosure generally relate to processing Channel Quality Information (CQI) and scheduling resources subject to cooperative resource allocation based on the CQI. To convey the CQI for protected/unprotected subframes in a single report, a new vector CQI format may be utilized. Two alternatives for CQI processing of the vector and their respective advantages are described. In a first alternative, a single entry is selected from the CQI vector to be processed by a downlink scheduler and/or other Medium Access Control (MAC) block (e.g., PHICH, DCI power control, and/or PDCCH scheduler). In a second alternative, selection is made from the CQI vector on a per-subframe basis, and both the subframe and the selected CQI element are processed by the downlink scheduler and/or the other MAC blocks.

In an aspect of the disclosure, a method for wireless communication is provided. The apparatus generally includes means for receiving at least one report on subframes, the report including Channel Quality Information (CQI) on subframes subject to different levels of protection due to a cooperative resource allocation scheme between a serving base station and at least one non-serving base station; and scheduling transmission resources based on the report.

In an aspect of the disclosure, an apparatus for wireless communication is provided. The apparatus generally includes means for receiving at least one report for a subframe, the report including CQIs for subframes subject to different levels of protection due to a cooperative resource allocation scheme between the apparatus and at least one base station; and means for scheduling transmission resources based on the report. For certain aspects, the apparatus may be a serving base station.

In an aspect of the disclosure, an apparatus for wireless communication is provided. The apparatus generally includes a receiver and a processing system. The receiver is generally adapted to receive at least one report on subframes including CQIs for subframes subject to different levels of protection due to a cooperative resource allocation scheme between the apparatus and at least one base station. The processing system is generally configured to schedule transmission resources based on the report.

In an aspect of the disclosure, a computer program product for wireless communication is provided. The computer-program product generally includes a computer-readable medium having code for receiving at least one report for a subframe, the report including CQI for subframes subject to different levels of protection due to a cooperative resource allocation scheme between a serving base station and at least one non-serving base station; and code for scheduling transmission resources based on the report.

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

Brief description of the drawings

Fig. 1 is a block diagram conceptually illustrating an example of a wireless communication network, in accordance with certain aspects of the present disclosure.

Fig. 2 is a block diagram conceptually illustrating an example of a frame structure in a wireless communication network, in accordance with certain aspects of the present disclosure.

Fig. 2A is a block diagram conceptually illustrating an example of uplink resource allocation, in accordance with certain aspects of the present disclosure.

Fig. 3 is a block diagram conceptually illustrating an example of a node B in communication with a user equipment device (UE) in a wireless communication network, in accordance with certain aspects of the present disclosure.

Fig. 4 illustrates an example heterogeneous network in accordance with certain aspects of the present disclosure.

Fig. 5 illustrates example resource partitioning in a heterogeneous network, in accordance with certain aspects of the present disclosure.

Fig. 6 illustrates an example cooperative partitioning of subframes in a heterogeneous network, in accordance with certain aspects of the present disclosure.

Fig. 7 is a functional block diagram conceptually illustrating a first architecture for Channel Quality Indicator (CQI) processing, in accordance with certain aspects of the present disclosure.

Fig. 8 is a functional block diagram conceptually illustrating a second architecture for CQI processing, in accordance with certain aspects of the present disclosure.

Fig. 9 illustrates example operations for scheduling transmission resources based on received CQI reports, in accordance with certain aspects of the present disclosure.

DETAILED DESCRIPTIONS

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 often used interchangeably. A CDMA network may implement radio technologies such as Universal Terrestrial Radio Access (UTRA), CDMA2000, and so on. UTRA includes wideband CDMA (wcdma) and other CDMA variants. cdma2000 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), IEEE802.16 (WiMAX), IEEE802.20, and,And so on. UTRA and E-UTRA are Universal Mobile Telecommunications systems ((R))UMTS). 3GPP Long Term Evolution (LTE) and LTE-advanced (LTE-A) are new UMTS releases that use E-UTRA. UTRA, E-UTRA, UMTS, LTE-A, and GSM are described in literature from an organization named "third Generation partnership project" (3 GPP). cdma2000 and UMB are described in documents from an organization named "third generation partnership project 2" (3 GPP 2). The techniques described herein may be used for the above-mentioned wireless networks and radio technologies as well as other wireless networks and radio technologies. For clarity, certain aspects of the techniques are described below for LTE, and LTE terminology is used in much of the description below.

Example Wireless network

Fig. 1 shows a wireless communication network 100, which may be an LTE network. Wireless network 100 may include several evolved node bs (enbs) 110 and other network entities. An eNB may be a station that communicates with user equipment devices (UEs) and may also be referred to as a base station, a node B, an access point, etc. Each eNB110 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 context in which the term is used.

An eNB may provide communication coverage for a macro cell, a pico cell, a femto cell, and/or other types of cells. A macro cell may cover a relatively large geographic area (e.g., an area with a radius of several kilometers) and may allow unrestricted access by UEs with service subscriptions. Picocells may cover a relatively small geographic area and may allow unrestricted access by UEs with service subscriptions. A femtocell may cover a relatively small geographic area (e.g., a residence) and may be restrictively accessible by UEs associated with the femtocell (e.g., UEs in a Closed Subscriber Group (CSG), UEs of users in the residence, etc.). The eNB of a macro cell may be referred to as a macro eNB. An eNB for a picocell may be referred to as a pico eNB. An eNB for a femtocell may be referred to as a femto eNB or a home eNB. In the example shown in fig. 1, enbs 110a, 110b, and 110c may be macro enbs for macro cells 102a, 102b, and 102c, respectively. eNB110x may be a pico eNB for pico cell 102 x. enbs 110y and 110z may be femto enbs for femto cells 102y and 102z, respectively. An eNB may support one or more (e.g., three) cells.

Wireless network 100 may also include relay stations. A relay station is a station that receives a transmission of data and/or other information from an upstream station (e.g., an eNB or UE) and sends a transmission of the data and/or other information to a downstream station (e.g., a UE or eNB). A relay station may also be a UE that relays transmissions for other UEs. In the example shown in fig. 1, relay 110r may communicate with eNB110a and UE120r to facilitate communication between eNB110a and UE120 r. A relay station may also be referred to as a relay eNB, relay, etc.

Wireless network 100 may be a heterogeneous network (HetNet) including different types of enbs, e.g., macro eNB, pico eNB, femto eNB, relay, etc. 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., 20 watts), while pico enbs, femto enbs, and relays may have a lower transmit power level (e.g., 1 watt).

Wireless network 100 may support synchronous or asynchronous operation. For synchronous operation, each eNB may have similar frame timing, and transmissions from different enbs may be approximately aligned in time. For asynchronous operation, each eNB may have different frame timing, and transmissions from different enbs may not be aligned in time. The techniques described herein may be used for both synchronous and asynchronous operations.

Network controller 130 may couple to a set of enbs and provide coordination and control for these enbs. Network controller 130 may communicate with each eNB110 via a backhaul. The enbs 110 may also communicate with one another, 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 stationary or mobile. A UE may also be referred to as a terminal, mobile station, 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 tablet, and so forth. The UE may be capable of communicating with macro enbs, pico enbs, femto enbs, relays, and/or the like. In fig. 1, a solid line with double arrows indicates the desired transmission between a UE and a serving eNB, which is an eNB designated to serve the UE on the downlink and/or uplink. The dashed line with double arrows indicates interfering transmissions between the UE and the eNB.

LTE utilizes Orthogonal Frequency Division Multiplexing (OFDM) on the downlink and single carrier frequency division multiplexing (SC-FDM) on the uplink. OFDM and SC-FDM partition the system bandwidth into multiple (K) orthogonal subcarriers, which are also collectively referred to as tones, bins, and the like. Each subcarrier may be modulated with data. In general, modulation symbols are sent in the frequency domain under OFDM and in the time domain under SC-FDM. The spacing between adjacent subcarriers may be fixed, and the total number of subcarriers (K) may depend on the system bandwidth. For example, K may be equal to 128, 256, 512, 1024, or 2048 for a system bandwidth of 1.25, 2.5, 5, 10, or 20 megahertz (MHz), respectively. The system bandwidth may also be divided into sub-bands. For example, a sub-band may cover 1.08MHz, and for a system bandwidth of 1.25, 2.5, 5, 10, or 20MHz, there may be 1, 2, 4, 8, or 16 sub-bands, respectively.

Fig. 2 shows a frame structure used in LTE. The transmission timeline for the downlink may be partitioned 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 with indices of 0 through 9. Each subframe may include two slots. Each radio frame may thus comprise 20 time slots with indices 0 to 19. Each slot may include L symbol periods, e.g., L =7 symbol periods for a normal cyclic prefix (as shown in fig. 2) or L =6 symbol periods for an extended cyclic prefix. The 2L symbol periods in each subframe may be assigned indices 0 through 2L-1. The available time-frequency resources may be divided into resource blocks. Each resource block may cover N subcarriers (e.g., 12 subcarriers) in one slot

In LTE, an eNB may transmit a Primary Synchronization Signal (PSS) and a Secondary Synchronization Signal (SSS) for each cell in the eNB. As shown in fig. 2, these primary and secondary synchronization signals may be sent in symbol periods 6 and 5, respectively, in each of subframes 0 and 5 of each radio frame with a normal cyclic prefix. These synchronization signals may be used by the UE for cell detection and acquisition. The eNB may send a Physical Broadcast Channel (PBCH) in symbol periods 0 through 3 in slot 1 of subframe 0. The PBCH may carry certain system information.

The eNB may transmit a Physical Control Format Indicator Channel (PCFICH) in the first symbol period of each subframe, as shown in fig. 2. The PCFICH may convey the number of symbol periods (M) used for the control channel, where M may be equal to 1, 2, or 3 and may vary from subframe to subframe. For small system bandwidths (e.g., having less than 10 resource blocks), M may also be equal to 4. The eNB may send a Physical HARQ Indicator Channel (PHICH) and a Physical Downlink Control Channel (PDCCH) (not shown in fig. 2) in the first M symbol periods of each subframe. The PHICH may carry information for supporting hybrid automatic repeat request (HARQ). The PDCCH may carry information on resource allocation to the UE and control information for a downlink channel. The eNB may send a Physical Downlink Shared Channel (PDSCH) in the remaining symbol periods of each subframe. The PDSCH may carry data intended for UEs scheduled for data transmission on the downlink. The various signals and channels in LTE are described in the publicly available 3GPPTS36.211 entitled "evolved Universal terrestrial radio Access (E-UTRA); physical channels and modulation.

The eNB may transmit the PSS, SSS, and PBCH in the center 1.08MHz of the system bandwidth used by the eNB. The eNB may transmit these channels across the entire system bandwidth in each symbol period in which the PCFICH and PHICH are transmitted. The eNB may send the PDCCH to the UE group at certain portions of the system bandwidth. The eNB may transmit the PDSCH to a particular UE in a particular portion of the system bandwidth. The eNB may transmit PSS, SSS, PBCH, PCFICH, and PHICH to all UEs in a broadcast manner, may transmit PDCCH to a specific UE in a unicast manner, and may also transmit PDSCH to a specific UE in a unicast manner.

There may be several resource elements available in each symbol period. Each resource element may cover one subcarrier in one symbol period and may be used to transmit one modulation symbol, which may be a real or complex value. Resource elements not used for reference signals in each symbol period may be arranged into Resource Element Groups (REGs). Each REG may include four resource elements in one symbol period. The PCFICH may occupy four REGs, which may be approximately equally spaced across frequency in symbol period 0. The PHICH may occupy three REGs, which may be spread across frequency in one or more configurable symbol periods. For example, the three REGs for the PHICH may all belong to symbol period 0 or may be spread in symbol periods 0, 1, and 2. The PDCCH may occupy 9, 18, 32, or 64 REGs, which may be selected from the available REGs, in the first M symbol periods. Only certain REG combinations may be allowed for PDCCH.

The UE may know the specific REGs for the PHICH and PCFICH. The UE may search for different REG combinations for the PDCCH. The number of combinations to search is generally less than the number of allowed combinations for PDCCH. The eNB may send the PDCCH to the UE in any combination that the UE will search for.

Fig. 2A is a block diagram conceptually illustrating an example of an uplink resource allocation 200A corresponding to, for example, the uplink in LTE, in accordance with certain aspects of the present disclosure. The available resource blocks for the uplink may be divided into a data section and a control section. The control section may be formed at both edges of the system bandwidth and may have a configurable size. Resource blocks in the control section may be assigned to the UE to transmit control information. The data section may include all resource blocks not included in the control section. The design in fig. 2A results in the data section including contiguous subcarriers, which may allow a single UE to be assigned all of the contiguous subcarriers in the data section.

The UE may be assigned resource blocks in the control section to transmit control information to the eNB. The UE may also be assigned resource blocks in the data section to transmit data to the eNB. The UE may transmit control information in a Physical Uplink Control Channel (PUCCH) 210 on the assigned resource blocks in the control section. The UE may transmit only data or both data and control information in a Physical Uplink Shared Channel (PUSCH) 220 on the assigned resource blocks in the data section. The uplink transmission may span both slots of a subframe and may hop across frequency, as shown in fig. 2A.

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 be selected based on various criteria such as received power, path loss, signal-to-noise ratio (SNR), and so on.

The UE may operate in a dominant interference scenario where the UE may observe high interference from one or more interfering enbs. A strong interference scenario may occur due to constrained association. For example, in fig. 1, UE120y may be close to femto eNB110y and may have high received power for eNB110 y. However, UE120y may not be able to access femto eNB110y due to restricted association and may then connect to macro eNB110c with lower received power (as shown in fig. 1) or to femto eNB110z also with lower received power (not shown in fig. 1). UE120y may then observe high interference from femto eNB110y on the downlink and may also cause high interference to eNB110y on the uplink.

A dominant interference scenario may also occur due to range extension, which is a scenario where a UE is connected to an eNB with lower path loss and lower SNR among all enbs detected by the UE. For example, in fig. 1, UE120x may detect macro eNB110b and pico eNB110x and may have lower received power for eNB110x than eNB110 b. However, if the pathloss of eNB110x is lower than that of macro eNB110b, it may be desirable for UE120x to connect to pico eNB110 x. This may cause less interference to the wireless network for a given data rate of UE120 x.

In an aspect, communication in a dominant interference scenario may be supported by having different enbs operate on different frequency bands. A frequency band is a range of frequencies that may be used for communication and may be given by (i) a center frequency and a bandwidth or (ii) a lower frequency and an upper frequency. A frequency band may also be referred to as a band, a channel, etc. The frequency bands of the different enbs may be selected to enable a UE to communicate with a weaker eNB in a strong interference scenario while allowing a strong eNB to communicate with its UEs. An eNB may be classified as a "weak" eNB or a "strong" eNB based on the received power of a signal received at the UE from the eNB (rather than based on the transmit power level of the eNB).

Fig. 3 shows a block diagram of a design of a base station or eNB110 and UE120, which may be one of the base stations/enbs and one of the UEs in fig. 1. For the constrained association scenario, eNB110 may be macro eNB110c in fig. 1, and UE120 may be UE120 y. The eNB110 may also be some other type of base station. The eNB110 may be equipped with T antennas 334a through 334T and the UE120 may be equipped with R antennas 352a through 352R, where generally T ≧ 1 and R ≧ 1.

At eNB110, a transmit processor 320 may receive data from a data source 312 and control information from a controller/processor 340. The control information may be for PBCH, PCFICH, PHICH, PDCCH, etc. The data may be for PDSCH, etc. Transmit processor 320 may process (e.g., encode and symbol map) the data and control information to obtain data symbols and control symbols, respectively. Transmit processor 320 may also generate reference symbols (e.g., for PSS, SSS, and cell-specific reference signals). A Transmit (TX) multiple-input multiple-output (MIMO) processor 330 may perform spatial processing (e.g., precoding) on the data symbols, the control symbols, and/or the reference symbols, if applicable, and may provide T output symbol streams to T Modulators (MODs) 332a through 332T. Each modulator 332 may process a respective output symbol stream (e.g., for OFDM, etc.) to obtain an output sample stream. Each modulator 332 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 332a through 332T may be transmitted via T antennas 334a through 334T, respectively.

At UE120, antennas 352a through 352r may receive downlink signals from eNB110 and may provide received signals to demodulators (DEMODs) 354a through 354r, respectively. Each demodulator 354 may condition (e.g., filter, amplify, downconvert, and digitize) a respective received signal to obtain input samples. Each demodulator 354 may further process the input samples (e.g., for OFDM, etc.) to obtain received symbols. A MIMO detector 356 may obtain received symbols from all R demodulators 354a through 354R, perform MIMO detection on the received symbols if applicable, and provide detected symbols. A receive processor 358 may process (e.g., demodulate, deinterleave, and decode) the detected symbols, provide decoded data for UE120 to a data sink 360, and provide decoded control information to a controller/processor 380.

On the uplink, at UE120, a transmit processor 364 may receive and process data (e.g., for the PUSCH) from a data source 362 and control information (e.g., for the PUCCH) from a controller/processor 380. The transmit processor 364 may also generate reference symbols for a reference signal. The symbols from the transmit processor 364 may be precoded by a TXMIMO processor 366 if applicable, further processed by the modulators 354a through 354r (e.g., for SC-FDM, etc.), and transmitted to the eNB 110. At the eNB110, the uplink signals from the UE120 may be received by antennas 334, processed by demodulators 332, detected by a MIMO detector 336 if applicable, and further processed by a receive processor 338 to obtain decoded data and control information sent by the UE 120. Receive processor 338 may provide decoded data to a data sink 339 and decoded control information to controller/processor 340.

Controllers/processors 340, 380 may direct the operation at eNB110 and UE120, respectively. According to certain aspects of the disclosure, receive processor 358, controller/processor 380, and/or transmit processor 364 of UE120 may create a Channel Quality Information (CQI) vector to be transmitted to eNB 110. Memories 342, 382 may store data and program codes for eNB110 and UE120, respectively. A scheduler 344 may schedule UEs for data transmission on the downlink and/or uplink.

Example resource partitioning

According to certain aspects of the present disclosure, when a network supports enhanced inter-cell interference coordination (eICIC), base stations may negotiate with each other to coordinate resources to reduce/eliminate interference by giving up part of their resources by interfering cells. By doing so, the UE may be able to access the serving cell by using resources yielded by the interfering cell, even with severe interference.

For example, a femtocell with a closed access mode (i.e., only member femtocells can access the cell) in the coverage of an open macrocell may cause a coverage hole for the macrocell. By having a femtocell relinquish some of its resources to effectively remove interference, a macro UE under the femtocell coverage area may be able to access the UE's serving macro cell by using the resources yielded by the femtocell.

In radio access systems using OFDM, such as evolved universal terrestrial radio access network (E-UTRAN), the resources yielded by the interfering cells may be time-based, frequency-based, or a combination of both. When the yielded resources are time based, the interfering cell does not use some subframes in the time domain. When the yielded resources (i.e., coordinated resource partitioning or coordinated resource allocation) are frequency based, the interfering cell does not use some subcarriers in the frequency domain. When the yielded resources are a combination of both frequency and time, the interfering cell does not use certain resources defined by frequency and time.

Fig. 4 illustrates an example scenario in which eICIC may allow a UE (i.e., macro UE120 y) that has registered with a macro cell that supports eICIC (e.g., a 10 th release (Rel-10) macro UE as shown in fig. 4) to access macro cell 110c (as illustrated by solid-line radio link 402) even if the macro UE120y is experiencing severe interference from femtocell 110 y. A legacy macro UE120u (e.g., a release 8 (Rel-8) macro UE as shown in fig. 4) may not be able to access the macro cell 110c under severe interference from the femtocell 110y, as illustrated by the broken radio link 404. A UE (also referred to as femto UE120 v) that has registered with a femto cell (e.g., an 8 th release (Rel-8) femto UE as shown in fig. 4) may access femto cell 110y without any interference problems from macro cell 110 c.

According to certain aspects, a network may support eICIC, where different sets of partitioning information are possible. The first of these sets may be referred to as semi-Static Resource Partitioning Information (SRPI). The second of these sets may be referred to as Adaptive Resource Partitioning Information (ARPI). As the name implies, the SPRI typically does not change frequently and an SRPI may be sent to the UE to enable the UE to use this resource partitioning information for its own operation.

As an example, resource partitioning may be implemented in an 8ms period (8 subframes) or a 40ms period (40 subframes). According to certain aspects, it may be assumed that Frequency Division Duplexing (FDD) may also be applied such that frequency resources may also be partitioned. For communication via the downlink (e.g., from eNB to UE), the partition pattern may be mapped to known subframes (e.g., the first subframe of each radio frame having a System Frame Number (SFN) value that is a multiple of an integer N, such as 4). Such mapping may be applied to determine Resource Partitioning Information (RPI) for a particular subframe. By way of example, subframes (e.g., yielded by an interfering cell) subject to downlink coordinated resource partitioning may be identified by an index:

indexing_{SRPI_DL}= (SFN x 10+ subframe number) mod8

For the uplink, the SRPI map may be shifted by, for example, 4 ms. Thus, an example of an uplink may be

Indexing_{SRPI_UL}= (SFN x 10+ subframe number +4) mod8

SRPI may use the following three values for each entry:

u (use): the value indicates that this subframe has been cleared from strong interference for use by the cell (i.e., the main interfering cell does not use the subframe);

n (not used): the value indicates that this subframe should not be used; and

x (unknown): this value indicates that this subframe is not statically partitioned. The UE does not know the details of the resource usage negotiation between the base stations.

Another possible set of parameters for SRPI may be as follows:

u (use): the value indicates that this subframe has been cleared from strong interference for use by the cell (i.e., the main interfering cell does not use the subframe);

n (not used): the value indicates that this subframe should not be used;

x (unknown): the value indicates that this subframe is not statically partitioned (and the UE is not aware of the details of resource usage negotiation between base stations); and

c (common): the value may indicate that all cells may use the subframe without resource partitioning. The subframe may be subject to interference so that the base station may choose to use the subframe only for UEs that are not experiencing severe interference.

The SRPI of the serving cell may be broadcast over the air. In the E-UTRAN, the SRPI of the serving cell may be sent in a Master Information Block (MIB), or in one of the System Information Blocks (SIBs). The predefined SRPI may be defined based on characteristics of the cell (e.g., macro cell, pico cell (with open access), and femto cell (with closed access)). In this case, encoding the SRPI in the overhead message may result in a more efficient over-the-air broadcast.

The base station may also broadcast the SRPI of the neighbor cell in one of the SIBs. To do so, the SRPI may be sent with its respective range of Physical Cell Identities (PCIs).

The ARPI may represent further resource partitioning information with detailed information about "X" subframes in the SRPI. As mentioned above, the detailed information about the "X" subframe is typically known only to the base station, and not to the UE.

Fig. 5 and 6 illustrate examples of SRPI assignments in scenarios with macro cells and femto cells as described above.

Example CQI processing for heterogeneous networks

As described above, a key mechanism of heterogeneous networks (hetnets) may be resource partitioning. As an example, a cell may be muted in a particular subframe, allowing users from neighbor cells under its coverage to be served. From the perspective of users experiencing significant interference, Time Division Multiplexing (TDM) partitioning between cells can broadly create two types of subframes: clean (protected) subframes and unclean (unprotected) subframes. Clean subframes may refer to subframes without interference from a dominant non-serving cell, and unclean subframes may refer to subframes with interference from a non-serving cell.

According to certain aspects of the present disclosure, a new Channel Quality Indicator (CQI) vector format may allow channel quality information for clean subframes and unclean subframes to be captured in a single report. According to certain aspects, the report may be communicated to a scheduler (e.g., of the eNB) which, in turn, makes a decision on how to use the CQI information to schedule UEs reporting the CQI. The UE may report CQI by transmitting a CQI vector 390 according to the new format to the eNB, as depicted in fig. 3. According to certain aspects, various options may be provided for CQI processing of CQI vectors by an eNB. These CQI processing options are not limited to circumstances in which CQI vector reporting is used; CQI information may also be reported with a single CQI (i.e., legacy) report.

Fig. 7 illustrates a first example architecture 700 for CQI processing. According to certain aspects, a vector CQI report may be received by the PUSCH/PUCCH reception module 720 and sent to the CQI selector module 704. As illustrated, a single CQI entry may be selected by CQI selector module 704. For certain aspects, the selection may be made on a relatively long time scale (rate of change in Radio Resource Management (RRM) measurement reports) of a few hundred milliseconds. CQI selection 705 may then be fed as input to Downlink (DL) scheduler 710 and other blocks 708 (e.g., Media Access Control (MAC) layer blocks). For certain aspects, block 708 may include a PHICH, Downlink Control Information (DCI) power control, and/or PDCCH scheduler. DL scheduler 710 or any other suitable processor may determine a CQI backoff for a Contention Window (CW) based on CQI selection 705. Once determined, a CQI backoff value (CQI backoff VAL) may also be provided to block 708. Upper layer process 706 can provide input to and/or control CQI selector module 704 and DL scheduler 710. For example, the upper layer processing may include Radio Resource Management (RRM) and/or resource partitioning.

An advantage of architecture 700 shown in fig. 7 may be that all CQI processing loops may be performed for a single CQI selection (the one provided by CQI selector module 704). However, this architecture may result in a suboptimal CQI being selected for each subframe based on whether the subframe is a clean subframe or an unclean subframe.

Fig. 8 illustrates a second example architecture 800 for CQI processing. According to certain aspects, the vector CQI report may be received via the PUSCH/PUCCH reception module 802. At each given subframe t, CQI selection may be made by the CQI selector module 804 to output a first or second CQI output (e.g., corresponding to a clean subframe or an unclean subframe). Both CQI selection and subframe t may be propagated to modules in architecture 800, such as DL scheduler 810 and other modules 808 (e.g., MAC layer blocks similar to block 708 in fig. 7). A scheduler 810 or any other suitable processor may determine a CQI backoff for a Contention Window (CW) based on the CQI selection. Once determined, a CQI backoff value (CQI backoff VAL [0] or CQI backoff VAL [1 ]) may also be provided to module 808. The upper layer processing 806 can provide input to and/or control the CQI selector module 804 and the scheduler 810.

An advantage of the architecture 800 shown in fig. 8 may be that it allows each block/module to run an individual CQI adjustment loop for each subframe type (clean or unclean). As a result, relatively fast CQI selection may be possible for a given UE, which may lead to better scheduling decisions. However, architecture 800 may involve a higher complexity relative to architecture 700 depicted in fig. 7 to maintain a desired CQI state at each block.

Fig. 9 illustrates example operations 900 for scheduling transmission resources based on received CQI reports, in accordance with certain aspects of the present disclosure. Operations 900 may be performed, for example, by eNB110 to schedule downlink transmissions to a UE. At 902, an eNB may receive at least one report on subframes including channel quality information (e.g., CQIs that may be received as vectors) for subframes subject to different levels of protection due to a cooperative resource allocation scheme between a serving base station and at least one non-serving base station. At 904, the eNB (which may be a serving base station) may schedule transmission resources based on the report received at 902.

For certain aspects, the scheduling is for transmission resources subject to a cooperative resource allocation scheme. For certain aspects, the report comprises a vector CQI report. Reports of different subframe types may be sent together in a newly defined report (e.g., a vector CQI report) or separately in a legacy report (i.e., a single CQI report). In the latter case, for certain aspects, the eNB may configure the UE such that single CQI reporting alternates between reported subframes and unprotected subframes.

For certain aspects, the scheduling includes assigning different time and/or frequency resources to respective subframes based on the corresponding levels of protection due to the respective subframes. For certain aspects, the scheduling includes assigning different Modulation and Coding Schemes (MCSs) to respective subframes based on corresponding levels of protection due to the respective subframes.

For certain aspects, the scheduling is performed based on a first loop corresponding to CQI reported for a first subframe type. For certain aspects, the scheduling is performed based on a second loop corresponding to CQI reported for a second subframe type. For certain aspects, the first subframe type is a protected subframe and the second subframe type is an unprotected subframe shared between the serving base stations and between the at least one non-serving base station. For certain aspects, the scheduling includes selecting a CQI entry based on the report.

For some aspects, the selection is performed on a per-subframe basis, while for other aspects, the selection is performed on a per-subframe type basis (e.g., protected subframes versus unprotected subframes). For certain aspects, the selecting includes selecting between an output of a CQI ring corresponding to a protected subframe and an output of a CQI ring corresponding to an unprotected subframe, as described above.

For certain aspects, the report is received via an uplink, such as an uplink control channel (e.g., PUCCH), an uplink data channel, or a shared uplink channel (i.e., an uplink channel in which either or both of control information or data traffic may be communicated, such as PUSCH). For certain aspects, subframes subject to different levels of protection include one or more subframes that are protected from interference from transmissions in other cells and one or more subframes that are not protected from interference from transmissions in other cells. For certain aspects, the scheduling is performed based on CQI values (e.g., an average of CQI values) that are filtered or otherwise statistically processed from multiple reports.

The various operations of the methods described above may be performed by any suitable means capable of performing the corresponding functions. These means may include various hardware and/or software components and/or modules, including but not limited to, circuits, Application Specific Integrated Circuits (ASICs), or processors. For example, the means for receiving may include the receiver, the demodulator 332, and/or the antenna 334 of the eNB110 shown in fig. 3. The means for scheduling may include the scheduler 344 of the eNB110 illustrated in fig. 3, the schedulers 710, 810 in fig. 7 and 8, respectively, or any suitable means for processing as described below. The means for processing and/or the means for determining may include a processing system that may include at least one processor, such as the transmit processor 320 or the controller/processor 340 of the eNB110 illustrated in fig. 3.

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 (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 aspects, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored or encoded 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 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 web site, 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 (disk) and disc (disc), as used herein, includes Compact Disc (CD), laser disc, optical disc, Digital Versatile Disc (DVD), floppy disk and blu-ray disc where disks (disks) usually reproduce data magnetically, while discs (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 (39)

1. A method for wireless communication, comprising:

receiving at least one report comprising Channel Quality Information (CQI) for subframes subject to different levels of protection due to a cooperative resource allocation scheme between a serving base station and at least one non-serving base station; and

scheduling transmission resources based on the report,

wherein the scheduling comprises assigning different time or frequency resources to respective subframes based on the corresponding levels of protection due to the respective subframes.

2. The method of claim 1, wherein the scheduling is for transmission resources subject to the cooperative resource allocation scheme between the serving base station and the at least one non-serving base station.

3. The method of claim 1, wherein the report comprises a vector CQI report.

4. The method of claim 1, wherein the scheduling comprises assigning different Modulation and Coding Schemes (MCSs) to respective subframes based on corresponding protection levels due to the respective subframes.

5. The method of claim 1, wherein the scheduling is performed based on a first loop corresponding to CQI reported for a first subframe type.

6. The method of claim 5, wherein the scheduling is performed based on a second loop corresponding to CQI reported for a second subframe type.

7. The method of claim 6, wherein the first subframe type is a protected subframe and the second subframe type is an unprotected subframe shared between the serving base station and the at least one non-serving base station.

8. The method of claim 1, wherein the scheduling comprises selecting a CQI entry based on the report.

9. The method of claim 8, wherein the selecting is performed on a per-subframe basis.

10. The method of claim 8, wherein the selecting comprises selecting between an output corresponding to a protected subframe and an output corresponding to an unprotected subframe.

11. The method of claim 1, wherein the report is received via an uplink control channel.

12. The method of claim 1, wherein the subframes subject to different protection levels comprise one or more subframes that are protected from interference from transmissions in other cells and one or more subframes that are not protected from interference from transmissions in other cells.

13. The method of claim 1, wherein the scheduling is performed based on filtered CQI values from a plurality of reports.

14. An apparatus for wireless communication, comprising:

means for receiving at least one report comprising Channel Quality Information (CQI) for subframes subject to different levels of protection due to a cooperative resource allocation scheme between the apparatus and at least one base station; and

means for scheduling transmission resources based on the report,

wherein the means for scheduling is configured to assign different time or frequency resources to respective subframes based on the corresponding levels of protection due to the respective subframes.

15. The apparatus of claim 14, wherein the means for scheduling is configured to schedule transmission resources subject to the cooperative resource allocation scheme.

16. The apparatus of claim 14, wherein the report comprises a vector CQI report.

17. The apparatus of claim 14, wherein the means for scheduling is configured to assign different Modulation and Coding Schemes (MCSs) to respective subframes based on corresponding protection levels due to the respective subframes.

18. The apparatus of claim 14, wherein the means for scheduling is configured to schedule the transmission resources based on a first loop corresponding to CQI reported for a first subframe type.

19. The apparatus of claim 18, wherein the means for scheduling is configured to schedule the transmission resources based on a second loop corresponding to CQI reported for a second subframe type.

20. The apparatus of claim 19, wherein the first subframe type is a protected subframe and the second subframe type is an unprotected subframe shared between the apparatus and the at least one base station.

21. The apparatus of claim 14, wherein the means for scheduling is configured to select a CQI entry based on the report.

22. The apparatus of claim 21, wherein the selecting is performed on a per-subframe basis.

23. The apparatus of claim 21, wherein the selecting comprises selecting between an output corresponding to a protected subframe and an output corresponding to an unprotected subframe.

24. The apparatus of claim 14, wherein the report is received via an uplink control channel.

25. The apparatus of claim 14, wherein the subframes subject to different protection levels comprise one or more subframes that are protected from interference from transmissions in other cells and one or more subframes that are not protected from interference from transmissions in other cells.

26. The apparatus of claim 14, wherein the means for scheduling is performed based on filtered CQI values from a plurality of reports.

27. An apparatus for wireless communication, comprising:

a receiver configured to receive at least one report comprising Channel Quality Information (CQI) for subframes subject to different levels of protection due to a cooperative resource allocation scheme between the apparatus and at least one base station; and

a processing system configured to schedule transmission resources based on the report,

wherein the processing system is configured to schedule the transmission resources by assigning different time and frequency resources to respective subframes based on the corresponding levels of protection due to the respective subframes.

28. The apparatus of claim 27, wherein the processing system is configured to schedule transmission resources subject to the cooperative resource allocation scheme.

29. The apparatus of claim 27, wherein the report comprises a vector CQI report.

30. The apparatus of claim 27, wherein the processing system is configured to schedule the transmission resources by assigning different Modulation and Coding Schemes (MCSs) to respective subframes based on corresponding protection levels due to the respective subframes.

31. The apparatus of claim 27, wherein the processing system is configured to schedule the transmission resources based on a first loop corresponding to CQI reported for a first subframe type.

32. The apparatus of claim 31, wherein the processing system is configured to schedule the transmission resources based on a second loop corresponding to CQI reported for a second subframe type.

33. The apparatus of claim 32, wherein the first subframe type is a protected subframe and the second subframe type is an unprotected subframe shared between the apparatus and the at least one base station.

34. The apparatus of claim 27, wherein the processing system is configured to schedule the transmission resources by selecting a CQI entry based on the report.

35. The apparatus of claim 34, wherein the selection is performed on a per-subframe basis.

36. The apparatus of claim 34, wherein the selecting comprises selecting between an output corresponding to a protected subframe and an output corresponding to an unprotected subframe.

37. The apparatus of claim 27, wherein the report is received via an uplink control channel.

38. The apparatus of claim 27, wherein the subframes subject to different protection levels comprise one or more subframes that are protected from interference from transmissions in other cells and one or more subframes that are not protected from interference from transmissions in other cells.

39. The apparatus of claim 27, wherein the processing system is configured to schedule the transmission resources based on filtered CQI values from a plurality of reports.