HK1221083B - Coordinated interference mitigation and cancelation - Google Patents

Abstract

A method includes receiving at user equipment an indication of a subset of scheduling constraints for interference mitigation and cancelation and performing interference mitigation and cancelation utilizing the subset of scheduling constraints.

Description

Coordinated interference mitigation and cancellation

RELATED APPLICATIONS

This application claims priority to U.S. application serial No. 14/135,296 filed on 19.12.2013 and U.S. provisional application serial No. 61/843,826 filed on 8.7.2013, both of which are incorporated herein by reference in their entirety.

Drawings

Fig. 1A is a block diagram illustrating intra-cell interference, according to an example embodiment.

Fig. 1B is a block diagram illustrating inter-cell interference, according to an example embodiment.

Fig. 2 is a block diagram illustrating limitations on jointly scheduled UEs, according to an example embodiment.

Fig. 3 is a flow diagram illustrating a method for performing interference mitigation and cancellation, according to an example embodiment.

FIG. 4 is a table of coordination combinations using a two-bit index, according to an example embodiment.

FIG. 5 is an alternative table using two-bit indexed coordinated combinations according to an example embodiment.

FIG. 6 is a table of coordination combinations using a three-bit index, according to an example embodiment.

Fig. 7A and 7B are block diagrams illustrating inter-cell coordination according to example embodiments.

Fig. 8 is a block diagram of an example cell station, according to an example embodiment.

Background

Interference is a serious problem in wireless cellular communications, especially as cell sizes become smaller and User Equipment (UE) densities become higher. It has been shown that Interference Mitigation and Cancellation (IMC) techniques can be implemented at the UE side for better throughput and quality of service (QoS). Due to signals from intra-cell or inter-cell, the UE is typically controlled and coded using private scrambling (scrambling) or allocation, especially in existing versions the UE can actually only mask (blind) IMCs by exhaustive search or by linear processing based on statistics. This causes high complexity or poor performance for IMC.

Detailed Description

The following detailed description refers to the accompanying drawings. The same reference numbers may be used in different drawings to identify the same or similar elements. In the following detailed description, for purposes of explanation and not limitation, specific details are set forth such as particular structures, architectures, interfaces, techniques, etc. in order to provide a thorough understanding of the various aspects of the claimed invention. However, it will be apparent to those skilled in the art that the benefits of the present disclosure, as claimed in various aspects of the present invention, may be practiced in other examples that depart from these specific details. In certain instances, descriptions of well-known devices, circuits, and methods are omitted so as not to obscure the description of the present invention with unnecessary detail.

Interference is a serious problem in wireless cellular communications, especially as cell sizes become smaller and User Equipment (UE) densities become higher. It has been shown that Interference Mitigation and Cancellation (IMC) techniques can be implemented at the UE side for better throughput and quality of service (QoS). The UE is typically controlled and coded using a private scrambling or allocation due to signals from within or between cells, and the UE can only mask IMC by exhaustive search or by linear processing based on statistics. This causes high complexity or poor performance for IMC. This is because the number of possible combinations between resource allocation, PMI (precoding matrix indicator), and MCS (modulation coding scheme), etc. is a large number. By sending the UE some side information (side information) about co-scheduled UE(s) or even UEs across cells, better IMC results are expected to be achieved. Thus, example embodiments enable network-assisted interference cancellation and mitigation.

In various examples, intra-cell and inter-cell transmissions at MCS/resource allocation levels are coordinated. Associated side information transmission and coding methods are provided for informing the UE, thereby enabling more efficient and effective IMC.

In one example embodiment, scheduling coordination is performed between MU-MIMO (multi-user multiple input multiple output) UEs in one cell and coordination across neighboring cells. When a base station (eNB-evolved node B) schedules one or more pairs of UEs in a cell for MU-MIMO, the combination between MCS, precoding (PMI-precoding matrix indicator) and frequency-time resources is limited to a smaller number of possibilities. The combining uses fewer bits to be narrowed and indexed, which will be sent to the UE as a new type of DCI (downlink control indicator) for better IMC. In some example embodiments, there may be more than MCS, PMI, and frequency-time resources. One example is power.

In cross-cell coordination, slow coordination between cells determining a set of frequency-time resources is presented so that neighboring cells can allocate UEs in the area that suffer interference. In this so-called "interference coordination area" (IC-area), a limited number of combinations of MCS/resource scheduling/PMI and the like are allowed. A UE scheduled in such a region may assume that the interfering signal has a limited possible allocation on resource allocation and/or MCS, etc. This allows for better IMC and better interference situations. Several specific options in coding are also provided.

Fig. 1A and 1B show two interference scenarios. Intra-cell interference is shown at 100 in fig. 1A and relates to interference between different UEs indicated at 102 and 104 in a single base station (eNB) indicated at 106. Inter-cell interference is shown at 110 in fig. 1B and relates to interference between two base stations 112, 114 at one or more UEs indicated at 116. The size of the arrow indicates the relative signal strength between the UE and the cell station. The design of intra-cell coordination can be seen as a special case of inter-cell coordination in various examples. It is noted that the limited combinations will generally benefit in terms of system throughput, especially at cell edge UEs. This is because these UEs will not perform well with high MCS orders, expensive scheduling, or complex combinations.

The example mechanisms provide intra-cell and inter-cell coordination without excessive overhead. By carefully selecting a limited number of combinations, a good trade-off is achieved between the performance of interference cancellation for cell-edge UEs and the overall system throughput.

In LTE, the scheduling of transmissions by a UE has many parameters, such as modulation order (QPSK/16QAM/64QAM), MCS (index of modulation/coding combination), PMI, resource allocation, transmission mode, layer/rank (rank), etc. We refer to this set of parameters as "scheduling parameters". This creates a large search space for any UE that attempts to accomplish interference cancellation or mitigation in a good way.

In one example, the scheduling method of the eNB limits the number of possible combinations between co-scheduled UEs (e.g., MU-MIMO UEs or cross-cell UEs). This may be referred to as a subset of scheduling constraints, which by definition contains fewer constraints than are normally available for use in performing interference cancellation mitigation. In one embodiment, the scheduling constraint is for modulation/TM (transmission mode)/MCS/PMI. The parameters of the coordination may be within a limited boundary of each other (compared to the number of possibilities without such coordination).

The UE may be informed by its eNB through special signaling that it is under such co-scheduling coordination. A new DCI format with dedicated K bits (e.g., 2 or 3 bits) is used by the eNB to indicate the coordination mode, i.e., which restrictions are to be enforced. The new DCI may be changed at a subframe level.

At a high level, e.g. RRC (radio resource control) with a slower time period, the mapping between these bits and the coordination mode may be changed. Neighboring cells may be coordinated through the backhaul (e.g., X2) at a slower frequency for coordinated scheduling towards better IMC performance. Neighboring cells may agree on a special resource region (IC-region) on a resource grid (e.g., a set of RBs across a particular subframe). UEs scheduled in this area may have a very limited number of possible combinations of scheduling parameters. In another example, in an intra-cell coordination case, the eNB may provide more information to UEs in the IC-region by using new DCI.

Regarding possible combinations, once a UE (e.g., UE0) is informed that it is scheduled by interference coordination, the following restrictions on jointly scheduled UEs as shown at 200 in fig. 2 are enforced:

1) the resource allocation of any co-scheduled UEs 210, 215 has only a limited number of starting points and scheduling patterns. For example, one option would assume that the co-scheduled UE RBs (radio bands) may only overlap completely or in the case of UEs 220, 225 start from the midpoint 230 of the RB allocation from UE0, and that the RBs must be contiguous;

2) the modulation order of the co-scheduled UEs is within a limited range (e.g., 0 (equal order) or 1). The MCS order may be assumed to be within a specific range, which may be inferred based on the new DCI message.

3) The transmission modes are within a limited number of combinations.

4) The number of co-schedules should be limited. The new DCI may also specify a limit on the number, e.g., not to exceed 2 or 4. This also applies to the number of co-scheduled UEs.

In intra-cell design, the eNB has a set of coordination modes, e.g., mode 1, …, mode J. Each pattern corresponds to a table of K entries, each entry represented by an index. Each entry restricts scheduling options for jointly scheduled UEs. The coordinated characteristics include: RB allocation, modulation order, TM, number of co-scheduled UEs, number of layers, etc.

A method 300 of performing interference mitigation and cancellation with various resource allocation patterns is shown in fig. 3. At 310, RRC signaling may be used to specify which mode is active. At 315, coordination is indicated to the UE by letting the UE know the index of the entry in the control instruction (PDCCH). At 320, based on the "mode" and the "item index," the UE restricts the common scheduling options, which facilitates interference mitigation in its decoding. At 325, the UE may generally assume that all of its co-scheduled UEs do not use 64 QAM. (since 64QAM is already the best modulation order and resembles random gaussian noise).

DCI can be used in two different options. In a first option, the private DCI is sent to a co-scheduled UE identified by the eNB. This option allows legacy UEs (not understanding the new DCI) to be co-scheduled. In a second option, the common DCI is multicast to all co-scheduled UEs. The control channel may be scrambled and encoded using a sequence known to all of the UEs.

Several design options may utilize at least 2 or 3 bits (indicating a coordination combination). In one example, two bits of information are transmitted. Each such information indicates a specific limitation on the possible combinations. The emphasis is on the case where co-scheduled UEs have similar scheduling settings.

In one specific example, shown in tabular form at 400 in fig. 4, it is assumed that UE0 is the UE that receives the new DCI. M (0) is the modulation order of UE0, and M (k) is for coordinated UE (k). The index column 410 shows four entries, 0, 1, 2, and 3, corresponding to a two-bit index. RB allocation is shown at 415. In this example, the RB allocation may change in the middle or switch once at a midpoint. The modulation order is shown at 420, and as shown, the modulation order may be the same or may vary between M (0) -1 and M (0) + 1. For each UE, TM (transmission mode) 425 is shown to be the same as UE0, as is the RS port location at 430. The number of co-scheduled UEs in column 435 varies between 1 and less than or equal to 4. The number of co-scheduled ranks at 440 may also vary between 1 and less than or equal to 4.

In another option, shown in tabular form at 550 in fig. 5, the UE may assume that 64QAM is not used. Table 500 uses the same reference numerals as table 400 (which are the same as the columns of table 500). Further, the x dB power difference is shown at 510 and is a threshold number. If 64QAM is utilized, the side information is not used much.

In a further option, coordination between rank/RB/modulation/TM # UEs is utilized, as shown in fig. 6 at table 600. The index 610 in this example is a three-bit index with corresponding arabic numerals 0 through 7, for a total of up to 8 entries. RB allocation is shown at 615. The modulation order is shown at 620, and in various examples may be the same as the modulation order of UE0, the same as the modulation order of UE0 on all layers, varying between M (0) -1 and M (0) +1, equal to M (0) -1 or M (0) +1, M (k) ═ M (0) -1 or M (0), M (k) less than or equal to M (0) + 1. In this example, the only difference between index 0 and index 1 is that index 1 allows for two co-scheduled ranks. The term "all layers" means that the schedules of both layers are subject to the same constraints. The TM is shown at 625 and may be the same as UE0 or a legacy TM, on all layers, as UE0 or a legacy TM. The PR port location is shown at 630 and may be the same as the PR port location of UE0 or the same as the PR port location of UE0 on all layers. The number of co-scheduled UEs is shown at 635 and may vary between 1 and 4, with specific examples shown as 1, 2, and less than or equal to 4. Finally, the number of co-scheduled ranks at 640 may also vary from 1 to 4, with specific examples shown as 1, 2, and less than or equal to 4.

A further option is that the UE may assume that 64QAM is not used. In addition to the above combination, the lower side information may be transmitted for better information compression. Side information 1: total number of scheduled UEs/ranks. Side information 2: maximum variation of certain parameters between UEs. For example, | modulation order (i) | < ═ 1, excluding 64 QAM; or | mcs (i) -mcs (j) | < ═ 3.

Inter-cell coordination may also be performed. The basic structure and steps are shown at 700 in fig. 7 and in fig. 7B. The neighboring cells indicated at 710 and 715 are exchanged via X2 (or other backhaul channel) for coordination of IMC. In X2, the dedicated resource region a (frequency + time) at 720 is referred to as an "interference coordination region (IC-region)". In this IC-area 720, the scheduling of each cell may be implicitly or easily derived by the neighbors. At a fixed time period (e.g., 200ms), the neighboring cells 710, 715 are synchronized again on IC-area a 720 and the derived mechanism for scheduling in a (i.e., the scheduling constraint).

Scheduling alignment in IC-region 720: for UEs scheduled in the IC-region, the UE may infer that scheduling coordination is in effect. The parameters under coordination are similar to those in the intra-cell MU-MIMO case.

There are many options to limit the possible coordination combinations within the IC-area. The text presents several options, including that all UEs in area a can only use QPSK (phase shift keying). In further options, the RB allocation for the UE starts from a specified set of RBs (e.g., contiguous) and/or has a fixed length (e.g., 3/6/9 RBs). This helps neighbor UEs to mask interference cancellation and mitigation. In another option, its transmission is fixed to a very limited number of combinations, e.g., rank 1, 16QAM, for each RB block.

Figure 8 is a block diagram of a specially programmed computer system for use as one or more different types of cell stations, including user equipment, small cell stations, and macro stations. The system may be used to implement one or more methods in accordance with examples described herein. In the embodiment shown in FIG. 8, a hardware and operating environment is provided that enables a computer system to perform one or more of the methods and functions described herein. In some embodiments, the system may be a small cell station, a macro cell station, a smartphone, a tablet, or other networked device that may provide access and wireless networking functionality to one or more devices. Such a device need not have all of the elements included in fig. 8.

Fig. 8 illustrates a functional block diagram of a cell station 800 according to some embodiments. Cell station 800 may be adapted to function as a small cell station, a macro cell station, or user equipment (e.g., a wireless cellular telephone, tablet or other computer). Cell station 800 may include physical layer circuitry 802 to transmit signals to eNB and receive signals from eNB 104 using one or more antennas 801. Cell station 800 may also include processing circuitry 804, and processing circuitry 804 may include a channel estimator, and/or the like. Cell station 800 can also include memory 806. The processing circuitry may be configured to determine a number of different feedback values, discussed below, for transmission to the eNB. The processing circuit may also include a Media Access Control (MAC) layer.

In some embodiments, cell station 800 may include one or more of the following: a keyboard, a display, a non-volatile memory port, multiple antennas, a graphics processor, an application processor, speakers, and other mobile device elements. The display may be an LCD screen including a touch screen.

The one or more antennas 801 utilized by cell station 800 may include one or more directional or omnidirectional antennas, including, for example, dipole antennas, monopole antennas, patch antennas (patch antennas), loop antennas (loopantennas), microstrip antennas or other types of antennas suitable for transmission of RF signals. In some embodiments, instead of two or more antennas, a single antenna with multiple apertures may be used. In these embodiments, each aperture may be considered a separate antenna. In some multiple-input multiple-output (MIMO) embodiments, antennas may be effectively separated to take advantage of spatial diversity and different channel characteristics that may result between each antenna and the antennas of a transmitting station. In some MIMO embodiments, the antennas may be separated by up to 1/10 wavelengths or more.

Although cell station 800 is illustrated as having several separate functional elements, one or more of the functional elements may be combined and may be implemented by combinations of software-configured elements, such as processing elements including Digital Signal Processors (DSPs), and/or other hardware elements. For example, some elements may comprise one or more microprocessors, DSPs, Application Specific Integrated Circuits (ASICs), Radio Frequency Integrated Circuits (RFICs), and combinations of various hardware and logic circuitry for performing at least the functions described herein. In some embodiments, a functional element may refer to one or more processing elements operating on one or more processing elements.

Embodiments may be implemented in one or a combination of hardware, firmware, and software. Embodiments may also be implemented as instructions stored on a computer-readable storage medium, which may be read and executed by at least one processor to perform the operations described herein. A computer-readable storage medium may include any non-transitory mechanism for storing information in a form readable by a machine (e.g., a computer). For example, a computer-readable storage medium may include Read Only Memory (ROM), Random Access Memory (RAM), magnetic disk storage media, optical storage media, flash memory devices, and other storage devices and media. In these embodiments, one or more processors of cell station 800 may be configured with instructions to perform the operations described herein.

In some embodiments, cell station 800 may be configured to receive OFDM communication signals over a multicarrier communication channel in accordance with an OFDMA communication technique. The OFDM signal may include a plurality of orthogonal subcarriers. In some broadband multicarrier embodiments, the evolved node b (nb) may be part of a Broadband Wireless Access (BWA) network communication network: such as a Worldwide Interoperability for Microwave Access (WiMAX) communication network or a third generation partnership project (3GPP) Universal Terrestrial Radio Access Network (UTRAN) Long Term Evolution (LTE) or Long Term Evolution (LTE) communication network, although the scope of the invention is not limited in this respect. In these wideband multicarrier embodiments, cell station 800 and eNB may be configured to communicate in accordance with Orthogonal Frequency Division Multiple Access (OFDMA) techniques. The UTRAN LTE standard includes the third generation partnership project (3GPP) standards for UTRAN-LTE, release 8 of month 3 2008 and release 10 of month 12 2010 (including variants and evolutions thereof).

In some LTE embodiments, the basic unit of radio resources is a Physical Resource Block (PRB). A PRB may include 12 subcarriers in the frequency domain x 0.5ms in the time domain. PRBs may be allocated in pairs (in the time domain). In these embodiments, the PRB may include a plurality of Resource Elements (REs). The RE may include one subcarrier × one symbol.

The eNB may transmit two types of reference signals including demodulation reference signals (DM-RS), channel state information reference signals (CIS-RS), and/or Common Reference Signals (CRS). The DM-RS may be used by the UE for data demodulation. The reference signal may be transmitted in a predetermined PRB. In some embodiments, the OFDMA technique may be one of a Frequency Domain Duplexing (FDD) technique using different uplink and downlink frequency spectrums or a Time Domain Duplexing (TDD) technique using the same frequency spectrum for uplink and downlink.

In some other embodiments, cell station 800 and an eNB may be configured to transmit signals transmitted using one or more other modulation techniques, such as spread spectrum modulation (e.g., direct sequence code division multiple access (DS-CDMA) and/or frequency hopping code division multiple access (FH-CDMA)), Time Division Multiplexing (TDM) modulation, and/or Frequency Division Multiplexing (FDM) modulation, although the scope of the embodiments is not limited in this respect.

In some embodiments, cell station 800 may be part of a portable wireless communication device: for example, a Personal Digital Assistant (PDA), a laptop or portable computer with wireless communication capability, a web tablet, a wireless telephone, a wireless headset, a pager, an instant messaging device, a digital camera, an access point, a television, a medical device (e.g., a heart rate monitor, a blood pressure monitor, etc.), or other device that may receive and/or transmit information wirelessly.

In some LTE embodiments, cell station 800 may calculate several different feedback values that may be used to perform channel adaptation for the closed-loop spatial multiplexing transmission mode. These feedback values may include a Channel Quality Indicator (CQI), a Rank Indicator (RI), and a Precoding Matrix Indicator (PMI). With the CQI, the transmitter selects one of several modulation symbol sets and coding rate combinations. The RI informs the transmitter about the number of useful transport layers of the current MIMO channel, and the PMI indicates a codebook index of a precoding matrix applied at the transmitter (depending on the number of transmit antennas). The coding rate used by the eNB may be based on the CQI. The PMI may be a vector calculated by the cell station and reported to the eNB. In some embodiments, the cell station may transmit a Physical Uplink Control Channel (PUCCH) containing CQI/PMI or RI formats 2, 2a, or 2 b.

In these embodiments, the CQI may be an indication of the downlink mobile radio channel quality experienced by cell station 800. The CQI allows the cell station 800 to propose to the eNB the best modulation scheme and coding rate to use for a given radio link quality so that the resulting transport block error rate will not exceed a certain value (e.g., 10%). In some embodiments, the cell station may report a wideband CQI value, which refers to the channel quality of the system bandwidth. The cell station may also report a subband CQI value for each subband of a particular number of resource blocks that may be configured by higher layers. The complete set of sub-bands may cover the system bandwidth. In the case of spatial multiplexing, the CQI for each codeword may be reported.

In some embodiments, the PMI may indicate an optimal precoding matrix to be used by the eNB for given radio conditions. The PMI value refers to a codebook table. The network configures the number of resource blocks represented by the PMI report. In some embodiments, to cover system bandwidth, multiple PMI reports may be provided. PMI reports may also be provided for closed-loop spatial multiplexing, multi-user MIMO, and closed-loop rank 1 precoding MIMO modes.

In some coordinated multipoint (CoMP) embodiments, a network may be configured for joint transmission to cell stations, where two or more cooperating/cooperating points (e.g., Remote Radio Heads (RRHs)) transmit jointly. In these embodiments, the joint transmission may be a MIMO transmission and the cooperating points are configured to perform joint beamforming.

LTE channel estimation

To assist in the estimation of channel characteristics, LTE uses cell-specific interference signals (i.e., pilot symbols) inserted in both time and frequency. These pilot symbols provide an estimate of the channel at a given position within the subframe. By interpolation, the channel can be estimated across any number of subframes. The pilot symbols in LTE are allocated positions within a subframe according to the eNodeB cell identification number and which transmission antenna is being used, as shown in the following figure. The unique positioning of the pilots ensures that they do not interfere with each other and can be used to provide a reliable estimate of the complex gain imparted on each resource element within the grid transmitted by the propagation channel.

To minimize the effect of noise on the pilot estimate, the least squares estimate is averaged using an averaging window. This simple approach causes a substantial reduction in the level of noise present on the pilot. There are two available pilot symbol averaging methods.

Time averaging is performed across each pilot symbol carrying a subcarrier such that the column vector contains an average amplitude and phase for each interfering signal carrying a subcarrier.

All pilot symbols present in the subcarriers are time-averaged across all OFDM symbols such that the column vector contains an average for each interfering signal subcarrier. The average of the pilot symbol subcarriers is then frequency averaged using a moving window of maximum size.

In some embodiments, the PSS and SSS provide the cell stations their physical layer identity within the cell. The signal may also provide frequency and time synchronization within the cell. The PSS may be constructed from a Zadoff-chu (zc) sequence and the length of the sequence may be predetermined in the frequency domain (e.g., 62). The SSS uses two interleaved sequences (i.e., Maximum Length Sequences (MLS), SRG sequences, or m-sequences) of a predetermined length (e.g., 31). The SSS may be scrambled with the PSS sequence that determines the physical layer ID. One purpose of the SSS is to provide cell stations with information about cell ID, frame timing characteristics, and Cyclic Prefix (CP) length. The cell station may also be informed whether to use TDD or FD. In FDD, the PSS may be located in the last OFDM symbol in the first and eleventh slots of a frame, followed by the SSS in the next symbol. In TDD, PSS may be transmitted in the third symbol of the third and thirteenth slots, and SSS may be transmitted three symbols earlier. The PSS provides the cell station with information about which of three sets of physical layers (3 sets of 168 physical layers) the cell belongs to. One of the 168 SSS sequences can be decoded immediately after PSS and directly define the cell group identity.

In some embodiments, a cell station may be configured in one of 8 "transmission modes" for PDSCH reception: mode 1: single antenna port, port 0; mode 2: transmit diversity; mode 3: a large delay CDD; mode 4: closed-loop spatial multiplexing; mode 5: MU-MIMO; mode 6: closed-loop spatial multiplexing, single-layer; mode 7: single antenna port, cell site specific RS (port 5); mode 8 (new mode in Re 1-9): single or dual layer transmission with cell site specific RS (ports 7 and/or 8). The CSI-RS is used by the cell station for channel estimation (i.e., CQI measurement). In some embodiments, CSI-RS are periodically transmitted at different subcarrier frequencies (allocated to cell stations) in particular antenna ports (up to eight antenna ports) for use in estimating MIMO channels. In some embodiments, the cell-station specific demodulation reference signals (e.g., DM-RS) may be precoded in the same manner as the data if non-codebook based precoding is applied.

Examples of the invention

1. An example apparatus, comprising:

a transceiver;

a processor; and

a memory having instructions for execution by the processor to:

receiving an indication of a subset of scheduling constraints for interference mitigation and cancellation; and

performing interference mitigation and cancellation using the subset of scheduling constraints.

2. The example apparatus of example 1, wherein the indication includes an index corresponding to a subset of available scheduling parameters to be used for performance of interference mitigation and cancellation.

3. The example apparatus of example 2, wherein the processor further accesses a table using the index, the table having a plurality of index sets of modulation coding scheme/resource combinations.

4. The example apparatus of example 3, wherein the subset of modulation coding scheme/resource combinations comprises at least two modulation coding schemes/resources selected from the group consisting of MCS (modulation coding scheme), precoding (PMI-precoding matrix indicator), and frequency-time resources.

5. The example apparatus of example 1, wherein the scheduling constraint specifies that co-scheduled user equipment radio bands are completely overlapping.

6. The example apparatus of example 5, wherein the scheduling constraint specifies that co-scheduled user equipment radio bands are allowed to start from a midpoint of a radio band allocation and the radio bands are contiguous.

7. The example apparatus of example 1, wherein the scheduling constraint specifies that a modulation order of co-scheduled user equipments is within a limited range.

8. The example apparatus of example 1, wherein the scheduling constraint specifies that transmission modes are within a limited number of combinations.

9. The example apparatus of example 1, wherein the scheduling constraint specifies that a number of co-scheduled user equipments is limited.

10. An example method, comprising:

receiving, at a user equipment, an indication of a subset of scheduling constraints for interference mitigation and cancellation; and

performing interference mitigation and cancellation using the subset of scheduling constraints.

11. The example method of example 10, wherein the indication includes an index corresponding to a subset of available scheduling parameters to be used for performance of interference mitigation and cancellation.

12. The example method of example 11, further comprising: a table is accessed using the indices, the table having a plurality of index sets of modulation coding scheme/resource combinations.

13. The example method of example 12, wherein the subset of modulation coding scheme/resource combinations comprises at least two modulation coding schemes/resources selected from the group consisting of MCS (modulation coding scheme), precoding (PMI-precoding matrix indicator), and frequency-time resources.

14. The example method of example 10, wherein the scheduling constraints for interference mitigation and cancellation are received by the user equipment in an interference coordination area between neighboring cells.

15. The example method of example 10, further comprising:

exchanging information identifying interfering cooperation areas between neighboring cells; and

synchronizing scheduling constraints to communicate to user equipments in the interfering cooperation area.

16. The example method of example 15, wherein one scheduling constraint comprises a radio band allocation starting from a specified set of radio bands.

17. The example method of example 15, wherein one scheduling constraint comprises use of phase shift keying by all user equipments within the interfering cooperation area.

18. An example base station, comprising:

a transceiver;

a processor; and

a memory having instructions for execution by the processor to:

identifying a subset of scheduling constraints for interference mitigation and cancellation; and

transmitting an indication of the subset of scheduling constraints to a plurality of user equipments within a cell of a base station to enable the user equipments to perform interference mitigation and cancellation with the subset of scheduling constraints.

19. The example base station of example 18, wherein the processor further performs the following:

exchanging information identifying interfering cooperation areas between neighboring cells; and

synchronizing scheduling constraints to communicate to user equipments in the interfering cooperation area.

20. The example base station of example 18, wherein a subset of scheduling constraints comprises radio band allocation starting from a specified set of radio bands and all user equipments within the interference coordination area use phase shift keying.

In various examples, the scheduling constraints are for modulation/TM/MCS/PMI. In one example, the parameters of the coordination are within limited boundaries of each other (as compared to the number of possibilities without such coordination).

The 2-3 bits may be used to index into a table to limit the differences between co-scheduled UEs. The table may be used to select combinations to limit possible combinations between co-scheduled UEs (or UEs scheduled on similar resources in neighboring cells). So that the UE can easily indicate the scheduling combination of the interfering signals. The set of tables may be used to limit combining, with emphasis on modulation order, transmission mode, and power difference, etc. Note that the tables themselves have a particular flexibility to accommodate changes. For example, in fig. 5, "xddb" is used. Coordination may also be accomplished across cells on the interference coordination area.

The foregoing description of one or more implementations provides illustration and description, but is not intended to be exhaustive or to limit the scope of the invention to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practice of various implementations of the invention.

Claims (20)

1. An apparatus for performing interference mitigation and cancellation, comprising:

a transceiver;

a processor; and

a memory having instructions for execution by the processor to:

receiving an indication of a subset of scheduling constraints for interference mitigation and cancellation, the indication being common to at least one other user equipment receiver and the indication being in the form of a Downlink Control Indicator (DCI) with an index corresponding to the subset of scheduling constraints in a locally stored table having a plurality of sets of indices of the subset of scheduling constraints corresponding to modulation/transmission mode/modulation coding scheme/precoding matrix indicators;

using the index to recover the subset of scheduling constraints from the local storage table; and

performing interference mitigation and cancellation using the subset of scheduling constraints.

2. The apparatus of claim 1, wherein the indication comprises an index corresponding to a subset of available scheduling parameters to be used for performance of interference mitigation and cancellation.

3. The device of claim 2, wherein the processor further uses the index to access a table having a plurality of index sets of subsets of scheduling constraints corresponding to modulation/transmission mode/modulation coding scheme/precoding matrix indicators.

4. The apparatus of claim 3, wherein the subset of modulation coding scheme/resource combinations comprises at least two modulation coding schemes/resources selected from the group consisting of MCS (modulation coding scheme), precoding (PMI-precoding matrix indicator) and frequency-time resources.

5. The apparatus of claim 1, wherein the scheduling constraint specifies that co-scheduled user equipment radio bands are completely overlapping.

6. The apparatus of claim 5, wherein the scheduling constraint specifies that co-scheduled user equipment radio bands are allowed to start from a midpoint of a radio band allocation and the radio bands are contiguous.

7. The apparatus of claim 1, wherein the scheduling constraint specifies that a modulation order of co-scheduled user equipments is within a limited range.

8. The apparatus of claim 1, wherein the scheduling constraint specifies that a transmission mode is within a limited number of combinations.

9. The apparatus of claim 1, wherein the scheduling constraint specifies that a number of co-scheduled user equipments is limited.

10. A method for performing interference mitigation and cancellation, comprising:

receiving, at a user equipment, an indication of a subset of scheduling constraints for interference mitigation and cancellation, the indication being common to at least one other user equipment receiver and the indication being in the form of a Downlink Control Indicator (DCI) with indices corresponding to the subset of scheduling constraints in a local storage table having a plurality of sets of indices for the subset of scheduling constraints corresponding to modulation/transmission mode/modulation coding scheme/precoding matrix indicators;

using the index to recover the subset of scheduling constraints from the local storage table; and

performing interference mitigation and cancellation using the subset of scheduling constraints.

11. The method of claim 10, wherein the indication comprises an index corresponding to a subset of available scheduling parameters to be used for performance of interference mitigation and cancellation.

12. The method of claim 11, further comprising: a table is accessed using the indices, the table having a plurality of index sets of modulation coding scheme/resource combinations.

13. The method of claim 12, wherein the subset of modulation coding scheme/resource combinations comprises at least two modulation coding schemes/resources selected from the group consisting of MCS (modulation coding scheme), precoding (PMI-precoding matrix indicator) and frequency-time resources.

14. The method of claim 10, wherein the scheduling constraints for interference mitigation and cancellation are received by the user equipment in an interference coordination area between neighboring cells.

15. The method of claim 10, further comprising:

exchanging information identifying interfering cooperation areas between neighboring cells; and

synchronizing scheduling constraints to communicate to user equipments in the interfering cooperation area.

16. The method of claim 15, wherein one scheduling constraint comprises: the radio band allocation starts from a specified set of radio bands.

17. The method of claim 15, wherein one scheduling constraint comprises: all user equipments within the interfering cooperation area use phase shift keying.

18. A base station, comprising:

a transceiver;

a processor; and

a memory having instructions for execution by the processor to:

identifying a subset of scheduling constraints for interference mitigation and cancellation, the subset of scheduling constraints reducing a search space for a user equipment to: searching for uses of scheduling constraints to cancel interference resulting from the uses; and

transmitting an indication of the subset of scheduling constraints to a plurality of user equipments within a cell of a base station to enable the user equipments to perform interference mitigation and cancellation with the subset of scheduling constraints, the indication being in the form of a Downlink Control Indicator (DCI) having an index corresponding to the subset of scheduling constraints in a table stored on the plurality of user equipments, the table having a plurality of sets of indices of the subset of scheduling constraints corresponding to modulation/transmission mode/modulation coding scheme/precoding matrix indicators.

19. The base station of claim 18, wherein the processor further performs the following:

exchanging information identifying interfering cooperation areas between neighboring cells; and

synchronizing scheduling constraints to communicate to user equipments in the interfering cooperation area.

20. The base station of claim 18, wherein a subset of scheduling constraints comprises: the radio band allocation starts from a specified set of radio bands and all user equipments within the interference coordination area use phase shift keying.