WO2015116070A1

WO2015116070A1 - Enhanced control channel interference coordination and avoidance

Info

Publication number: WO2015116070A1
Application number: PCT/US2014/013678
Authority: WO
Inventors: Amitav Mukherjee; Long GAO; Sudhanshu Gaur
Original assignee: Hitachi, Ltd.
Priority date: 2014-01-29
Filing date: 2014-01-29
Publication date: 2015-08-06

Abstract

Reliable decoding of control channels can be important in Long Term Evolution/Long Term Evolution Advanced (LTE/LTE-A) networks. Methods are provided for intercell interference coordination of control channels in LTE networks. Dense deployments of heterogeneous and small cell networks can increase interference and further degrade control channel (CC) reception. With coordination between base stations, interference to legacy or enhanced control channels can be mitigated. However, the overhead and periodicity of coordination can be dependent on the inter-eNB backhaul link quality. Implementations are provided for CC ICIC, under various backhaul quality assumptions.

Description

Field

[0001] The present application generally directed to communication networks, and more specifically, to control channel interference.

Related Art

[0002] In the related art, a Long Term Evolution (LTE) radio frame may contain ten subframes, which are indexed between 0 and 9 as shown in FIG. 1. Each subframe can be further divided into two slots, each of which may include seven orthogonal frequency-division multiplexing (OFDM) symbols for normal Cyclic Prefix (CP) length, or six OFDM symbols for extended CP length. In the frequency domain, the LTE signal can be divided into units of twelve subcarriers, each of which can span 180 kilohertz (kHz) of bandwidth with a subcarrier spacing of 15 kHz. Such a subcarrier unit for the duration of one slot is defined as a Resource Block (RB). A RB is further divided into Resource Elements (REs). One RE is one OFDM subcarrier for the duration of one OFDM symbol, and is the smallest unit in the LTE time- frequency resource grid. The REs can be allocated for control channels such as Enhanced Physical Downlink Control Channels (EPDCCH) and data channels such as Physical Downlink Shared Channel (PDSC!I).

[0003] Related ait methods for control channel (CC) inter-cell interference coordination (ICIC) may be divided into two broad categories, those that need regular inter-enhanced node B (eNB) coordination, and those that require very infrequent or no coordination.

[0004] For related art implementations where regular inter-eNB coordination is utilized, the eNBs can conduct signaling exchange of planned transmit powers. Thus, the eNBs

. l . indicate to neighboring eNBs their tentative TX powers on physical RBs (PRBs), e.g., using enhanced Relative Narrowband Transmit Power (RNT'P). In another example, the eNBs can conduct a signaling exchange of interference preferences, wherein the eNBs indicate to neighboring eNBs which frequency resources they can tolerate high, medium, and low interference, respectively.

[0005] In related art implementations where minimal or no coordination is conducted by eNBs, the eNBs can be configured to statically partition the four enhanced resource element groups (EREGs) among small cells. A small cell selects one of the first three EREGs as its first priority group and uses the selected EREG for EPDCCH transmission with the first priority. In another example, the eNBs can dynamically reconfigure search spaces via explicit signaling to the User Equipment (IJE). In yet another example, resources for the EPDCCH, enhanced physical control format indicator channel (EPCFICH) and enhanced physical hybrid automatic repeat request indicator channel (EPHICH) from different cells may be shifted based on the cell ID or other throughput (TP)-related parameters (e.g., TP ID) to avoid collisions and mitigate interference.

SUMMARY

[0006] Aspects of the present disclosure may include a base station, which may involve a memory configured to store at least one first report associated with at least one neighboring base station, and a second report associated with the base station, and a processor, configured to compute, from the at least one first report and the second report, an Enhanced Physical Downlink Control Channel (EPDCCH) allocation for one or more subframes for each of the at least one neighboring base station. [0007] Aspects of the present disclosure may further include a method for a base station, which may involve storing at least one first report associated with at least one neighboring base station, and a second report associated with the base station; and computing, from the at least one first report and the second report, an Enhanced Physical Downlink Control Channel (EPDCCH) allocation for one or more subframes for each of the at least one neighboring base station.

[0008] Aspects of the present disclosure may further include a computer program storing instructions for a base station. The instructions may include storing at least one first report associated with at least one neighboring base station, and a second report associated with the base station; and computing, from the at least one first report and the second report, an Enhanced Physical Downlink Control Channel (EPDCCH) allocation for one or more subframes for each of the at least one neighboring base station. The computer program may be stored on a computer readable storage medium or a computer readable signal medium which can be executed by a hardware system such as a computer or a processor.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIG. I illustrates an example LTE frame structure.

[0010] FIG. 2 illustrates a small cell deployment scenario with CC ICiC over backhaul links, in accordance with an example implementation.

[0011] FIG. 3 illustrates an example of logical eNB modules showing communication between eNB entities over an interface during CC ICIC, in accordance with an example implementation.

[0012] FIG. 4 is an example of CS computation module located at a designated eNB and interactions with neighbor e-NBs, in accordance with an example implementation. [0013] FIG. 5(a) illustrates candidate EREGs for EPDCCH placement locations within a subframe, in accordance with an example implementation.

[0014] FIG. 5(b) illustrates an example output based on an EPDCCH allocation for an arbitrary eNB showing occupied EREGs, in accordance with an example implementation.

[0015] FIGS. 6(a) and 6(b) illustrate an overview of CC interference cancellation, in accordance with an example implementation.

[0016] FIG. 7 illustrates a low-interference indicator bitmap with P entries for system bandwidth of P RBs, in accordance with an example implementation.

[0017] FIGS. 8(a) and 8(b) illustrate an example overview of low interference indicator signaling, in accordance with an example implementation.

DETAILED DESCRIPTION

[0018] The following detailed description provides further details of the figures and example implementations of the present application. Reference numerals and descriptions of redundant elements between figures are omitted for clarity. Terms used throughout the description are provided as examples and are not intended to be limiting. For example, the use of the term "automatic" may involve fully automatic or semi-automatic implementations involving user or administrator control over certain aspects of the implementation, depending on the desired implementation of one of ordinary skill in the art practicing implementations of the present application. The terms enhanced node B (eNodeB), small cell (SC), base station (BS) and pico cell may be utilized interchangeably throughout the example implementations. The implementations described herein are also not intended to be limiting, and can be implemented in various ways, depending on the desired implementation. [0019] Example implementations of the present disclosure are proposed based on the type of backhaul utilized, each of which have different levels of coordination overhead, suitable for three broad categories of backhaul links.

[0020] In a first example implementation involving a high-rate low-latency backhaul, an algorithm for two-stage coordinated scheduling (CS) of control (EPDCCH) and data (PDSCH) channels is employed, with potentially joint allocation of UE EPDCCH sets.

[0021] In a second example implementation for a medium-rate low-latency backhaul, the base stations are configured to exchange parameters to assist control channel interference cancellation at UEs with advanced receivers. This second example implementation may involve less coordination overhead than the first example implementation.

[0022] in a third example implementation for low-rate medium -latency backhaul, the base stations are configured to conduct signaling of frequency resources which currently experience low interference to neighboring base stations by using a bitmap. Neighboring base stations can voluntarily transmit with low power on the respective PRBs, which thus continue to experience low interference and are suitable for EPDCCH. The third example implementation may involve less coordination overhead than the second example implementation.

[0023] The coordination may take place between base stations managing macro cells, small cells, or combination of both in a heterogeneous deployment. Each of the example implementations can be implemented in LIE Release 12 or beyond in terms of signaling, and may be deployed in conjunction or separately. Furthermore, the two-stage CS algorithm of the first example implementation can be utilized for EPDCCH whereas the related art CS has generally focused only on PDSCH. Application scenarios

[0024] FIG. 2 illustrates a small cell deployment scenario with CC ICIC over backhaul links, in accordance with an example implementation.

[0025] The application scenarios of example implementations include both homogeneous and heterogeneous eNB deployments, and can also be applied to small cell scenarios that may be densely deployed in LTE Rel-12 implementat ons and beyond. An example small cell network with CC ICIC is illustrated in FIG. 2, where it is assumed that the macro eNBs operate on a different carrier frequency and are not shown explicitly. To alleviate CC interference for cell-edge UEs, adjacent small cell eNBs 200, 201, 202 exchange CC-specific parameters and possibly Channel State Information (CS1) and interference levels in order to perform CC ICIC. The results of the CC ICIC are utilized to allocate CCs for associated UEs 210, 220, 230, and 240.

[0026] FIG. 3 illustrates an example of logical eNB modules showing communication between eNB entities 300 and 301 over X2/Xn interface 350 during CC ICIC, in accordance with an example implementation.

[0027] An adjacent eNB initiates CC ICIC by sending requests over X2/Xn logical interfaces 350 on backhaul links to communicate with other eNBs. The example eNB modules involved in the CC ICIC process are shown in FIG. 3, and generally involve a processor 310, 320, memory module 315, 325, and I/O interfaces 335, 345. The processor 310, 320 may be configured to perform one or more example implementations as described herein in conjunction with the main memory 315, 325 and I/O interface 335, 345. The elements within an eNB may be communicatively coupled to each other via a communication bus 305. eNBs may also have transmit and receiver antennas to communicate with their associated UEs. [0028] Specific details of the signaling between eNBs and proposed CC ICIC algorithms are provided below.

First Example Implementation - Two-stage control and data channel CS algorithm

[0029] The first example implementation addresses the high-rate low-latency backhaul scenario. High ICIC overhead and frequent inter -eNB signaling can be supported for a high- rate low-latency backhauL A two-stage CC/PDSCH CS algorithm is implemented. Here, a pre-designated eNB accumulates reports that include CC-specific information and CSI from eNBs within the coordination set (e.g. a set of neighboring eNBs that work in coordination with each other), computes the CS allocation, and communicates the result back to other members of the coordination set. For example, the CS may be performed at eNB 201 in FIG. 2, with entities 200, 201 , and 202 forming a coordination set. While the resource allocation is done jointly, each UE is ultimately served only by a single eNB.

[0030] in the first stage, joint scheduling of CCs is performed using an algorithm. EPDCCIl is generally more suitable for CS since frequency-selective scheduling within PDSCH region is possible, unlike legacy PDCCH which is always located in first three slots of a subframe. in the second stage, joint scheduling of PDSCH is performed. The same algorithm should not be applied for both stages, since for CCs the performance criterion is reliability, whereas for PDSCH, the performance criterion is throughput or proportional fairness. In variations of the first example implementation, only the first stage of CC CS is performed, followed by individual decisions for PDSCH scheduling. A high-level overview of the two-stage process is illustrated in FIG. 4. [0031] FIG. 4 is an example of CS computation module located at a designated eNB 401 and required interactions with neighbor eNBs 400 and 402, in accordance with an example implementati on.

[0032] In an example implementation, the designated eNB 401 may declare initiation of CS 4010 to the neighboring eNBs 400, 402. The eNBs 400, 402 may submit reports 4000, 4020 to the designated eNB 401 , which may also generate an additional report on its own based on associated UE. Based on the reports, the designated eNB 401 may then compute EPDCCH joint allocation 401 1. After the EPDCCIl allocation is computed, the designated eNB 401 may then compute PDSCH allocation 4012 based on the EPDCCIl allocation and the reports. The allocation can then be communicated to the eNBS 400, 402, which may then use the provided allocation for local transmission 4001 , 4021 .

[0033] In the first stage of CC CS, a performance criterion related to reliability is adopted. The performance criterion can be any criterion to facilitate the desired implementation. A non-limiting example signaling and algorithm is described next.

[0034] Let B be the coordination set with h eNBs that participate in CS for a set U with u total UEs, with u, UEs served by eNB j, j = \,...,h, T _.« = u . The system bandwidth spans P

PRB pairs that in turn contain a total of R EREGs. For each UE, the EPDCCH is made up of multiple linhanced Control Channel Elements (ECCEs); let r be the number of . R I . per ECCE. Assume an EPDCCH of aggregation level L includes rh EREGs, where r is generally 4 or 8. Aggregation level L can be I , 2, 4, 8, 16, or 32. Define a binary decision variable z, , _t , such that it is set to 1 if UE ?^' is allocated EREG k by its serving eNB j, and 0 otherwise, for i = Ι , , , , ,Μ,-, j = l,...,b, and Ic = I,...JR.. A particular EREG of an eNB can be allocated only to a single UE at a time. [0035] The signal to interference plus noise ratio (SINR) for UE i with thermal noise variance N_{0 i} on a particular EREG k can be expressed as:

where p is the transmit power of eNB j and _%. is the channel gain. For EPDCCH decoding, let a minimum SINR threshold of γ be required to achieve a maximum allowable CC block or symbol error rate for reliability assurance,

[0036] Signaling: each eNB within the coordination set sends a report which can include the minimum desired control channel size or aggregation level, UE information such as which UEs are cell-edge and historical throughputs, interference levels on their frequency resources, and/or UE CSI. The transmission of desired control channel size can utilize customized information elements outside the LTE Release 12 specification, depending on the desired implementation. The designated eNB may also generate its own report based on associated UEs which can include similar parameters. This report may also be used with the reports received from other eNRs in the coordination set to compute the EPDCCH allocation.

[0037] Stage I EPDCCH CS: As an example, assume distributed EPDCCH allocation for all UEs with constituent EREGs placed in different PRB pairs. FIG. 5(a) illustrates candidate EREGs for EPDCCH placement locations within a subtrame, in accordance with an example implementation. A subtrame includes a total of R eligible EREGs 515. This allows for flexibility of the CC IOC. Then in stage 1, the following example optimization may be performed:

where the objective function seeks to minimize the size of the resources allocated for EPDCCH, subject to constraints that EREGs cannot be shared by UEs, a minimum SINR is maintained for EREGs allocated for CCs, and that each UE gets its minimum desired aggregation level L,-, Variations of the objective function are not precluded, such as maximizing the minimum SINR on any EREG subject to the constraints. Modified or additional EREG based constraints may be used to ensure EREGs belong to particular EREG groups, or for localized EPDCCH scheduling depending on the desired implementation. Thus, the objective function can be utilized for for a distributed EPDCCH allocation where any EREG within the subframe can be used for a UE. In some example implementations, there is the possibility of localized EPDCCH allocation where all the EREGs assigned to a particular UE lie within the same Resource Block pair. In such an example, an additional EREG constraint can be utilized for the localized scenario.

[0038] Stage 2 PDSCH CS: FIG. 5(b) illustrates an example output based on an EPDCCH allocation for an arbitrary eNB showing occupied EREGs, in accordance with an example implementation. Once the EPDCCH allocation is performed as illustrated in FIG. 5(b), it is known which PRB pairs contain CCs and thus cannot be used for PDSCH. The remaining unused PRB pairs are then allocated to PDSCH using any desired PDSCH CS algorithm depending on the desired implementation. [0039] After the conclusion of the second stage, the overall CS allocation is communicated to eNBs within the coordination set B. The coordination process may he repeated every subframe or every few subframes.

Second Example Implementation - Control channel interference cancellation

[0040] The second example implementation can be directed to the medium-rate low- latency backhaul situation where CS from, the first example implementation may not be feasible. Here, the EPDCCH scheduling is done individually though messages are still exchanged between eNBs. For legacy PDCCH which always lies within first three slots of each subframe, CC regions of neighboring eNBs will overlap with high probability and the CC interference can be relatively predictable. In the case of EPDCCH, depending upon the CC placement different levels of frequency resource overlap may occur for neighboring eNBs. This example implementation can also be applicable to higher-rate backhaul link scenarios, possibly in conjunction with the first and third example implementations described herein.

[0041] in either scenario, neighboring eNBs can exchange CC side information to facilitate better CC interference cancelation at UEs operating advanced receivers. Examples of such side information include but are not limited to PDCCH control region size, EPDCCH placement information, aggregation levels used for cell-edge UEs, DCI formats used and RNT'I information. Exchanging these parameters can involve customized messages outside the LTE Release 12 specification. Serving eNBs then explicitly signal the obtained CC information of adjacent eNBs to their associated UEs, who may first decode the interfering CC signal and subtract it from the original received signal, or suppress it with advanced MIMO receiver processing algorithms. An overview of the process is depicted in the flowchart in FIG. 6.

[0042] FIGS. 6(a) and 6(b) illustrate an overview of CC interference cancellation, in accordance with an example implementation. The flow elements of FIG. 6(a) are described below with respect to elements from FIG. 6(b).

[0043] At 605, the eNBs 6000, 6010 and 6020 initiate and exchange CC side information over backhaul. At 610, the eNBs 6000, 6010, 6020 receive CSI from, associated UEs 6100, 6200, 6300, 6400. At 615, the serving eNBs signals adjacent CC information to cell-edge UEs with advanced receivers, in this example, the cell edge UE 6300 would receive the adjacent CC information from serving e-NB 6010. At 620, the cell edge UE 6300 utilize CC side- information for interference cancelati n/suppression of interference being received from neighboring eNB 6000.

Third example implementation - Low-interference indicator bitmap sig aling

[0044] The third example implementation is directed to the low-rate medium-latency backhaul situation where frequent inter-eNB signaling may not be feasible. In this example implementation, eNBs indicate frequency resources of one or more cell-edge UEs which currently experience low interference to neighbor eNBs using a bitmap. Neighbor eNBs can voluntarily transmit with low power on these PRBs, which thus continue to experience low interference and are suitable for EPDCCH. Here, eNBs perform individual EPDCCF1 scheduling and CC interference mitigation is best-effort.

[0045] FIG. 7 illustrates a low-interference indicator bitmap with P entries for system bandwidth of P RBs, in accordance with an example implementation. The example of FIG. 7 illustrates a system bandwidth of P PRBs for an arbitrary UE. RBs 715 that, experience interference levels higher than some threshold I (indicated in shade) are reported using bit 0 in the bitmap 725. Other PRBs experience interference levels lower than threshold I and are reported using bit 1 in the bitmap 725. The resulting bitmap 725 is of size P. The reporting granularity may be larger than a bit per every RB depending on the desired implementation. For example, RBG or subband granularity may be used, in which case the bitmap may have- less than P elements. The signaling message may utilize a new downlink information element outside of the LTE Release 12 specification, depending on the desired implementation. The information may be similar to an uplink overload indicator (OI) message, while the signaling frequency may be similar to RNTP or OI messages.

[0046] FIGS. 8(a) and 8(b) illustrate an example overview of low interference indicator signaling, in accordance with an example implementation. The flow elements of FIG. 8(a) are described below with respect to elements from FIG. 8(b).

[0047] At 805, the eNBs 8000, 8010, 8020 configure interference management resources (JMRs) and receives CSI from respective UEs 8100, 8200, 8300, 8400. At 810, the low- interference frequency resources of cell-edge UEs are signaled to interfering eNBs. In this example, cell edge UE 8300 receives interference from eNB 8000. eNB 8010 therefore transmits bitmap information to eNB 8000 to indicate which UEs are undergoing interference. At 815, neighboring eNBs acknowledge message and may send their own bitmaps as needed. In this example, neighboring eNB 8000 may acknowledge the bitmap received from eNB 8010. At 820, each of the eNBs may perform individual EPDCCH scheduling based on the received bitmaps.

[0048] Finally, some portions of the detailed description are presented in terms of algorithms and symbolic representations of operations within a computer. These algorithmic descriptions and symbolic representations are the means used by those skilled in the data processing arts to most effectively convey the essence of their innovations to others skilled in the art. An algorithm is a series of defined steps leading to a desired end state or result. In example implementations, the steps carried out require physical manipulations of tangible quantities for achieving a tangible result.

[0049] Unless specifically stated otherwise, as apparent from the discussion, it is appreciated that throughout the description, discussions utilizing terms such as "processing," "computing," "calculating," "determining," "displaying," or the like, can include the actions and processes of a computer system or other information processing device that manipulates and transforms data represented as physical (electronic) quantities within the computer system's registers and memories into other data similarly represented as physical quantities within the computer system's memories or registers or other information storage, transmission or display devices.

[0050] Example implementations may also relate to an apparatus for performing the operations herein. This apparatus may be specially constructed for the required purposes, or it may include one or more general-purpose computers selectively activated or reconfigured by one or more computer programs. Such computer programs may be stored in a computer readable medium, such as a computer-readable storage medium or a computer-readable signal medium. A computer-readable storage medium may involve tangible or non-transitory mediums such as, but not limited to optical disks, magnetic disks, read-only memories, random access memories, solid state devices and drives, or any other types of tangible media suitable for storing electronic information. A computer readable signal medium may include mediums such as carrier waves. The algorithms and displays presented herein are not inherently related to any particular computer or other apparatus. Computer programs can involve pure software implementations that involve instructions that perform the operations of the desired implementation,

[0051] Various general-purpose systems may be used with programs and modules in accordance with the examples herein, or it may prove convenient to construct a more specialized apparatus to perform desired method steps. In addition, the example implementations are not described with reference to any particular programming language. It will be appreciated that a variety of programming languages may be used to implement the teachings of the example implementations as described herein. The instructions of the programming language(s) may be executed by one or more processing devices, e.g., central processing units (CPUs), processors, or controllers.

[0052] As is known in the art, the operations described above can be performed by hardware, software, or some combination of^* software and hardware. Various aspects of the example implementations may be implemented using circuits and logic devices (hardware), while other aspects may be implemented using instructions stored on a machine-readable medium (software), which if executed by a processor, would cause the processor to perform a method to carry out implementations of the present application. Further, some example implementations of the present application may be performed solely in hardware, whereas other example implementations may be performed solely in software. Moreover, the various functions described can be performed in a single unit, or can be spread across a number of components in any number of ways. When performed by software, the methods may be executed by a processor, such as a general purpose computer, based on instructions stored on a computer-readable medium. If desired, the instructions can be stored on the medium in a compressed and/or encrypted format. [0053] Moreover, other implementations of the present application will be apparent to those skilled in the art from consideration of the specification and practice of the teachings of the present application. Various aspects and/or components of the described example implementations may be used singly or in any combination. It is intended that the specification and example implementations be considered as examples only, with the true scope and spirit of the present application being indicated by the following claims.

Claims

CLAIMS What is claimed is:

1. A base station, comprising: a memory configured to store at least one first report associated with at least one neighboring base station, and a second report associated with the base station; and a processor, configured to: compute, from the at least one first report and the second report, an Enhanced Physical Downlink Control Channel (EPDCCH) allocation for one or more subirames for each of the at least one neighboring base station.

2. The base station of claim 1, wherein the processor is configured to compute the EPDCCH allocation based on one or more enhanced resource element group (EREG) based constraints.

3. The base station of claim 1, wherein the processor is configured to compute the EPDCCH allocation based on a comparison of a signal to interference plus noise ratio ( SINK · of one or more enhanced resource element groups (EREGs) to a threshold.

4. The base station of claim 1 , wherein the processor is configured to compute the EPDCCH allocation based on a computation to minimize a size of resources allocated for EPDCCH based on an objective function.

5. The base station of claim 3 , wherein the at least one report comprises a desired control channel size of the at least one neighboring base station, and wherein the computation of the EPDCCH allocation is based on the desired control channel size.

6. The base station of claim 1, wherein the processor is further configured to compute a Physical Downlink Shared Channel (PDSCH) allocation for one or more subframes for each of the at least one neighboring base station, based on the computed EPDCCH allocation.

7. A method for a base station, comprising: storing at least one first report associated with at least one neighboring base station, and a second report associated with the base station; and computing, from the at least one first report and the second report, an Enhanced Physical Downlink Control Channel (EPDCCH) allocation for one or more subframes for each of the at least one neighboring base station.

8. The method of claim 7, wherein the computing the EPDCCH allocation is based on one or more enhanced resource element group (EREG) based constraints.

9. The method of claim 7, wherein the computing the EPDCCH allocation is based on a comparison of a signal to interference plus noise ratio (SINR) of one or more enhanced resource element groups (EREGs) to a threshold.

10. The method of claim 7, wherein the computing the EPDCCH allocation is based on a computation to minimize a size of resources allocated for EPDCCH based on an objective function.

11. The method of claim 7, wherein the at least one report comprises a desired control channel size of the at least one neighboring base station, and wherein the computing the EPDCCH allocation is based on the desired control channel size.

12. The method of claim 7, further comprising computing a Physical Downlink Shared Channel (PDSCH) allocation for one or more subframes for each of the at least one neighboring base station, based on the computed EPDCCH allocation.

13. A computer program storing instructions for a base station, the instructions comprising: storing at least one first report associated with at least one neighboring base station, and a second report associated with the base station; and computing, from the at least one first report and the second report, an Enhanced Physical Downlink Control Channel (EPDCCH) allocation for one or more subtrames for each of the at least one neighboring base station.

14. The computer program of claim 13, wherein the computing the EPDCCH allocation is based on a computation to minimize a size of resources allocated for EPDCCH based on an objective function.

15. The computer program of claim 13, wherein the instructions further comprise computing a Physical Downlink Shared Channel (PDSCH) allocation for one or more subtrames for each of the at least one neighboring base station, based on the computed EPDCCH allocation.