Patent Publication Number: US-2013235783-A1

Title: Evolved multimedia broadcast multicast service capacity enhancements

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S)  
     This application claims the benefit of U.S. Provisional Application Ser. No. 61/609,098 entitled “Evolved Multimedia Broadcast Multicast Service Capacity Enhancements” and filed on Mar. 9, 2012, which is expressly incorporated by reference herein in its entirety. 
    
    
     BACKGROUND  
     1. Field 
     The present disclosure relates generally to communication systems, and more particularly, to wireless communication systems with evolved multimedia broadcast multicast service. 
     2. Background 
     Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power). Examples of such multiple-access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency divisional multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems. 
     These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. An example of an emerging telecommunication standard is Long Term Evolution (LTE). LTE is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) mobile standard promulgated by Third Generation Partnership Project (3GPP). It is designed to better support mobile broadband Internet access by improving spectral efficiency, lower costs, improve services, make use of new spectrum, and better integrate with other open standards using OFDMA on the downlink (DL), SC-FDMA on the uplink (UL), and multiple-input multiple-output (MIMO) antenna technology. However, as the demand for mobile broadband access continues to increase, there exists a need for further improvements in LTE technology. Preferably, these improvements should be applicable to other multi-access technologies and the telecommunication standards that employ these technologies. 
     SUMMARY  
     In an aspect of the disclosure, a first cell receives a configuration identifying a plurality of transmission layers in a multi-layer spatial multiplexing scheme of a Multi-Media Broadcast over a Single Frequency Network (MBSFN). The configuration may identify resource block allocations to transmission layers, seed values for pattern generation, and timing information used for resource block allocation to transmission layers. In an aspect of the disclosure, the first cell transmits a first set of resource blocks during a first period of time using a first transmission layer to one or more user equipments (UE) located in the MBSFN. Another cell located in the MBSFN may concurrently transmit a second set of resource blocks to the UE in a second transmission layer. 
     In an aspect of the disclosure, the first and second sets of resource blocks may comprise the same resource blocks. In some embodiments, a plurality of cells transmit the first set of resource blocks to the UE in the first transmission layer during the first period of time. Signals from the plurality of cells may arrive at the UE at different times. A cyclic prefix may be defined for the MBSFN that has a duration selected to enable the UE to coherently combine the signals that arrive from the plurality of cells. 
     In an aspect of the disclosure, the first cell transmits the first set of resource blocks in the first transmission layer in accordance with an assignment of the first cell to the first transmission layer, the assignment being provided by the configuration. The first transmission layer may be assigned to the first cell based on a physical cell identifier (PCI) associated with the first cell and/or the first transmission layer may be assigned to the first cell based on an MBSFN area identifier. 
     In an aspect of the disclosure, the first cell may be reassigned to the second transmission layer during a second period of time and the first cell may transmit resource blocks only in its currently assigned transmission layer. Reassignment of the first cell to the second transmission layer may be initiated based on a function of time. 
     In an aspect of the disclosure, the first set of resource blocks is different from the second set of resource blocks. The first cell also transmits the second set of resource blocks to the UE in the second transmission layer during the first period of time. In some embodiments, the configuration defines an allocation of resource blocks or groups of resource blocks to each of the first and second sets of resource blocks. In some embodiments, the first cell transmits the first set of resource blocks in the first transmission layer and the second set of resource blocks in the second transmission layer based on a layer pattern provided by the configuration. In some embodiments, the first cell uses a combination of transmission layers and sets of resource blocks during a second period of time that is different from the combination of transmission layers and sets of resource blocks used during the first period of time. 
     In an aspect of the disclosure, during the first period of time another cell transmits at least one resource block to the UE in the first transmission layer that is not also transmitted by the first cell in the first transmission layer during the first period of time. The first cell transmits at least one resource block in the first transmission layer that is also transmitted by the another cell in the first transmission layer during the first period of time. The first set of resource blocks may include a minimum number of adjacent resource blocks. 
     In an aspect of the disclosure, transmitting a first set of resource blocks includes randomly selecting one or more resource blocks to be transmitted in the first transmission layer and one or more resource blocks to be transmitted in the second transmission layer. The first cell may transmit a selection of resource blocks in the first and second transmission layers during a second period of time that is different than the selection of resource blocks that is transmitted in the first and second transmission layers during the first period of time. 
     In an aspect of the disclosure, resource blocks are allocated to the first and second sets of resource blocks and the first and second sets of resource blocks are assigned to the first and second transmission layers by an operation and maintenance (OAM) provider of the MBSFN. 
     In an aspect of the disclosure, resource blocks are allocated to the first and second sets of resource blocks and the first and second sets of resource blocks are assigned to the first and second transmission layers by a Multi-Cell/Multicast Coordination Entity (MCE) service provider of the MBSFN. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         FIG. 1  is a diagram illustrating an example of a network architecture. 
         FIG. 2  is a diagram illustrating an example of an access network. 
         FIG. 3  is a diagram illustrating an example of a DL frame structure in LTE. 
         FIG. 4  is a diagram illustrating an example of an UL frame structure in LTE. 
         FIG. 5  is a diagram illustrating an example of a radio protocol architecture for the user and control planes. 
         FIG. 6  is a diagram illustrating an example of an evolved Node B and user equipment in an access network. 
         FIG. 7A  is a diagram illustrating an example of an evolved Multimedia Broadcast Multicast Service channel configuration in a Multicast Broadcast Single Frequency Network. 
         FIG. 7B  is a diagram illustrating a format of a Multicast Channel Scheduling Information Media Access Control control element. 
         FIG. 8  illustrates an access network that employs eMBMS. 
         FIG. 9  illustrates resource block mapping to transmission layers. 
         FIG. 10  is a flow chart of a method of wireless communication. 
         FIG. 11  is a conceptual data flow diagram illustrating the data flow between different modules/means/components in an exemplary apparatus. 
         FIG. 12  is a diagram illustrating an example of a hardware implementation for an apparatus employing a processing system. 
     
    
    
     DETAILED DESCRIPTION  
     The detailed description set forth below in connection with the appended drawings is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well known structures and components are shown in block diagram form in order to avoid obscuring such concepts. 
     Several aspects of telecommunication systems will now be presented with reference to various apparatus and methods. These apparatus and methods will be described in the following detailed description and illustrated in the accompanying drawings by various blocks, modules, components, circuits, steps, processes, algorithms, etc. (collectively referred to as “elements”). These elements may be implemented using electronic hardware, computer software, or any combination thereof. Whether such elements are implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. 
     By way of example, an element, or any portion of an element, or any combination of elements may be implemented with a “processing system” that includes one or more processors. Examples of processors include microprocessors, microcontrollers, digital signal processors (DSPs), field programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functionality described throughout this disclosure. One or more processors in the processing system may execute software. Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. 
     Accordingly, in one or more exemplary embodiments, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or encoded as one or more instructions or code on a computer-readable medium. Computer-readable media includes computer storage media. Storage media may be any available media that can be accessed by a 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 that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray™ disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media. 
       FIG. 1  is a diagram illustrating an LTE network architecture  100 . The LTE network architecture  100  may be referred to as an Evolved Packet System (EPS)  100 . The EPS  100  may include one or more user equipment (UE)  102 , an Evolved UMTS Terrestrial Radio Access Network (E-UTRAN)  104 , an Evolved Packet Core (EPC)  110 , a Home Subscriber Server (HSS)  120 , and an Operator&#39;s Internet Protocol (IP) Services  122 . The EPS can interconnect with other access networks, but for simplicity those entities/interfaces are not shown. As shown, the EPS provides packet-switched services, however, as those skilled in the art will readily appreciate, the various concepts presented throughout this disclosure may be extended to networks providing circuit-switched services. 
     The E-UTRAN includes the evolved Node B (eNB)  106  and other eNBs  108 . The eNB  106  provides user and control planes protocol terminations toward the UE  102 . The eNB  106  may be connected to the other eNBs  108  via a backhaul (e.g., an X2 interface). The eNB  106  may also be referred to as a base station, a Node B, an access point, a base transceiver station, a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS), an extended service set (ESS), or some other suitable terminology. The eNB  106  provides an access point to the EPC  110  for a UE  102 . Examples of UEs  102  include a cellular phone, a smart phone, a session initiation protocol (SIP) phone, a laptop, a personal digital assistant (PDA), a satellite radio, a global positioning system, a multimedia device, a video device, a digital audio player (e.g., MP3 player), a camera, a game console, a tablet, or any other similar functioning device. The UE  102  may also be referred to by those skilled in the art as a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a user agent, a mobile client, a client, or some other suitable terminology. 
     The eNB  106  is connected to the EPC  110 . The EPC  110  includes a Mobility Management Entity (MME)  112 , other MMEs  114 , a Serving Gateway  116 , a Multimedia Broadcast Multicast Service (MBMS) Gateway  124 , a Broadcast Multicast Service Center (BM-SC)  126 , and a Packet Data Network (PDN) Gateway  118 . The MME  112  is the control node that processes the signaling between the UE  102  and the EPC  110 . Generally, the MME  112  provides bearer and connection management. All user IP packets are transferred through the Serving Gateway  116 , which itself is connected to the PDN Gateway  118 . The PDN Gateway  118  provides UE IP address allocation as well as other functions. The PDN Gateway  118  is connected to the Operator&#39;s IP Services  122 . The Operator&#39;s IP Services  122  may include the Internet, an intranet, an IP Multimedia Subsystem (IMS), and a PS Streaming Service (PSS). The BM-SC  126  may provide functions for MBMS user service provisioning and delivery. The BM-SC  126  may serve as an entry point for content provider MBMS transmission, may be used to authorize and initiate MBMS Bearer Services within a PLMN, and may be used to schedule and deliver MBMS transmissions. The MBMS Gateway  124  may be used to distribute MBMS traffic to the eNBs (e.g.,  106 ,  108 ) belonging to a Multicast Broadcast Single Frequency Network (MBSFN) area broadcasting a particular service, and may be responsible for session management (start/stop) and for collecting eMBMS related charging information. 
       FIG. 2  is a diagram illustrating an example of an access network  200  in an LTE network architecture. In this example, the access network  200  is divided into a number of cellular regions (cells)  202 . In 3GPP, the term “cell” can refer to the smallest coverage area of an eNB and/or an eNB subsystem serving this coverage area, depending on the context in which the term is used. One or more lower power class eNBs  208  may have cellular regions  210  that overlap with one or more of the cells  202 . A lower power class eNB  208  may be referred to as a remote radio head (RRH). The lower power class eNB  208  may be a femto cell (e.g., home eNB (HeNB)), pico cell, or micro cell. The macro eNBs  204  are each assigned to a respective cell  202  and are configured to provide an access point to the EPC  110  for all the UEs  206  in the cells  202 . There is no centralized controller in this example of an access network  200 , but a centralized controller may be used in alternative configurations. The eNBs  204  are responsible for all radio related functions including radio bearer control, admission control, mobility control, scheduling, security, and connectivity to the serving gateway  116 . Although each eNB  204  in  FIG. 2  is illustrated within a single cell  202 , an eNB  204  may support one or multiple (e.g., three) cells. Accordingly, the terms “eNB”, “base station”, and “cell” may be used interchangeably herein. 
     The modulation and multiple access scheme employed by the access network  200  may vary depending on the particular telecommunications standard being deployed. In LTE applications, OFDM is used on the DL and SC-FDMA is used on the UL to support both frequency division duplex (FDD) and time division duplex (TDD). As those skilled in the art will readily appreciate from the detailed description to follow, the various concepts presented herein are well suited for LTE applications. However, these concepts may be readily extended to other telecommunication standards employing other modulation and multiple access techniques. By way of example, these concepts may be extended to Evolution-Data Optimized (EV-DO) or Ultra Mobile Broadband (UMB). EV-DO and UMB are air interface standards promulgated by the 3rd Generation Partnership Project 2 (3GPP2) as part of the CDMA2000 family of standards and employs CDMA to provide broadband Internet access to mobile stations. These concepts may also be extended to Universal Terrestrial Radio Access (UTRA) employing Wideband-CDMA (W-CDMA) and other variants of CDMA, such as TD-SCDMA; Global System for Mobile Communications (GSM) employing TDMA; and Evolved UTRA (E-UTRA), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, and Flash-OFDM employing OFDMA. UTRA, E-UTRA, UMTS, LTE and GSM are described in documents from the 3GPP organization. CDMA2000 and UMB are described in documents from the 3GPP2 organization. The actual wireless communication standard and the multiple access technology employed will depend on the specific application and the overall design constraints imposed on the system. 
     The eNBs  204  may have multiple antennas supporting MIMO technology. The use of MIMO technology enables the eNBs  204  to exploit the spatial domain to support spatial multiplexing, beamforming, and transmit diversity. Spatial multiplexing may be used to transmit different streams of data simultaneously on the same frequency. The data steams may be transmitted to a single UE  206  to increase the data rate or to multiple UEs  206  to increase the overall system capacity. This is achieved by spatially precoding each data stream (i.e., applying a scaling of an amplitude and a phase) and then transmitting each spatially precoded stream through multiple transmit antennas on the DL. The spatially precoded data streams arrive at the UE(s)  206  with different spatial signatures, which enables each of the UE(s)  206  to recover the one or more data streams destined for that UE  206 . On the UL, each UE  206  transmits a spatially precoded data stream, which enables the eNB  204  to identify the source of each spatially precoded data stream. 
     Spatial multiplexing is generally used when channel conditions are good. When channel conditions are less favorable, beamforming may be used to focus the transmission energy in one or more directions. This may be achieved by spatially precoding the data for transmission through multiple antennas. To achieve good coverage at the edges of the cell, a single stream beamforming transmission may be used in combination with transmit diversity. 
     In the detailed description that follows, various aspects of an access network will be described with reference to a MIMO system supporting OFDM on the DL. OFDM is a spread-spectrum technique that modulates data over a number of subcarriers within an OFDM symbol. The subcarriers are spaced apart at precise frequencies. The spacing provides “orthogonality” that enables a receiver to recover the data from the subcarriers. In the time domain, a guard interval (e.g., cyclic prefix) may be added to each OFDM symbol to combat inter-OFDM-symbol interference. The UL may use SC-FDMA in the form of a DFT-spread OFDM signal to compensate for high peak-to-average power ratio (PAPR). 
       FIG. 3  is a diagram  300  illustrating an example of a DL frame structure in LTE. A frame (10 ms) may be divided into 10 equally sized sub-frames. Each sub-frame may include two consecutive time slots. A resource grid may be used to represent two time slots, each time slot including a resource block. The resource grid is divided into multiple resource elements. In LTE, a resource block contains 12 consecutive subcarriers in the frequency domain and, for a normal cyclic prefix in each OFDM symbol, 7 consecutive OFDM symbols in the time domain, or 84 resource elements. For an extended cyclic prefix, a resource block contains 6 consecutive OFDM symbols in the time domain and has 72 resource elements. Some of the resource elements, as indicated as R  302 ,  304 , include DL reference signals (DL-RS). The DL-RS include Cell-specific RS (CRS) (also sometimes called common RS)  302  and UE-specific RS (UE-RS)  304 . UE-RS  304  are transmitted only on the resource blocks upon which the corresponding physical DL shared channel (PDSCH) is mapped. The number of bits carried by each resource element depends on the modulation scheme. Thus, the more resource blocks that a UE receives and the higher the modulation scheme, the higher the data rate for the UE. 
       FIG. 4  is a diagram  400  illustrating an example of an UL frame structure in LTE. The available resource blocks for the UL may be partitioned into a data section and a control section. The control section may be formed at the two edges of the system bandwidth and may have a configurable size. The resource blocks in the control section may be assigned to UEs for transmission of control information. The data section may include all resource blocks not included in the control section. The UL frame structure 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. 
     A UE may be assigned resource blocks  410   a,    410   b  in the control section to transmit control information to an eNB. The UE may also be assigned resource blocks  420   a,    420   b  in the data section to transmit data to the eNB. The UE may transmit control information in a physical UL control channel (PUCCH) on the assigned resource blocks in the control section. The UE may transmit only data or both data and control information in a physical UL shared channel (PUSCH) on the assigned resource blocks in the data section. A UL transmission may span both slots of a subframe and may hop across frequency. 
     A set of resource blocks may be used to perform initial system access and achieve UL synchronization in a physical random access channel (PRACH)  430 . The PRACH  430  carries a random sequence and cannot carry any UL data/signaling. Each random access preamble occupies a bandwidth corresponding to six consecutive resource blocks. The starting frequency is specified by the network. That is, the transmission of the random access preamble is restricted to certain time and frequency resources. There is no frequency hopping for the PRACH. The PRACH attempt is carried in a single subframe (1 ms) or in a sequence of few contiguous subframes and a UE can make only a single PRACH attempt per frame (10 ms). 
       FIG. 5  is a diagram  500  illustrating an example of a radio protocol architecture for the user and control planes in LTE. The radio protocol architecture for the UE and the eNB is shown with three layers: Layer 1, Layer 2, and Layer 3. Layer 1 (L1 layer) is the lowest layer and implements various physical layer signal processing functions. The L1 layer will be referred to herein as the physical layer  506 . Layer 2 (L2 layer)  508  is above the physical layer  506  and is responsible for the link between the UE and eNB over the physical layer  506 . 
     In the user plane, the L2 layer  508  includes a media access control (MAC) sublayer  510 , a radio link control (RLC) sublayer  512 , and a packet data convergence protocol (PDCP)  514  sublayer, which are terminated at the eNB on the network side. Although not shown, the UE may have several upper layers above the L2 layer  508  including a network layer (e.g., IP layer) that is terminated at the PDN gateway  118  on the network side, and an application layer that is terminated at the other end of the connection (e.g., far end UE, server, etc.). 
     The PDCP sublayer  514  provides multiplexing between different radio bearers and logical channels. The PDCP sublayer  514  also provides header compression for upper layer data packets to reduce radio transmission overhead, security by ciphering the data packets, and handover support for UEs between eNBs. The RLC sublayer  512  provides segmentation and reassembly of upper layer data packets, retransmission of lost data packets, and reordering of data packets to compensate for out-of-order reception due to hybrid automatic repeat request (HARQ). The MAC sublayer  510  provides multiplexing between logical and transport channels. The MAC sublayer  510  is also responsible for allocating the various radio resources (e.g., resource blocks) in one cell among the UEs. The MAC sublayer  510  is also responsible for HARQ operations. 
     In the control plane, the radio protocol architecture for the UE and eNB is substantially the same for the physical layer  506  and the L2 layer  508  with the exception that there is no header compression function for the control plane. The control plane also includes a radio resource control (RRC) sublayer  516  in Layer 3 (L3 layer). The RRC sublayer  516  is responsible for obtaining radio resources (i.e., radio bearers) and for configuring the lower layers using RRC signaling between the eNB and the UE. 
       FIG. 6  is a block diagram of an eNB  610  in communication with a UE  650  in an access network. In the DL, upper layer packets from the core network are provided to a controller/processor  675 . The controller/processor  675  implements the functionality of the L2 layer. In the DL, the controller/processor  675  provides header compression, ciphering, packet segmentation and reordering, multiplexing between logical and transport channels, and radio resource allocations to the UE  650  based on various priority metrics. The controller/processor  675  is also responsible for HARQ operations, retransmission of lost packets, and signaling to the UE  650 . 
     The transmit (TX) processor  616  implements various signal processing functions for the L1 layer (i.e., physical layer). The signal processing functions includes coding and interleaving to facilitate forward error correction (FEC) at the UE  650  and mapping to signal constellations based on various modulation schemes (e.g., binary phase-shift keying (BPSK), quadrature phase-shift keying (QPSK), M-phase-shift keying (M-PSK), M-quadrature amplitude modulation (M-QAM)). The coded and modulated symbols are then split into parallel streams. Each stream is then mapped to an OFDM subcarrier, multiplexed with a reference signal (e.g., pilot) in the time and/or frequency domain, and then combined together using an Inverse Fast Fourier Transform (IFFT) to produce a physical channel carrying a time domain OFDM symbol stream. The OFDM stream is spatially precoded to produce multiple spatial streams. Channel estimates from a channel estimator  674  may be used to determine the coding and modulation scheme, as well as for spatial processing. The channel estimate may be derived from a reference signal and/or channel condition feedback transmitted by the UE  650 . Each spatial stream is then provided to a different antenna  620  via a separate transmitter  618 TX. Each transmitter  618 TX modulates an RF carrier with a respective spatial stream for transmission. 
     At the UE  650 , each receiver  654 RX receives a signal through its respective antenna  652 . Each receiver  654 RX recovers information modulated onto an RF carrier and provides the information to the receive (RX) processor  656 . The RX processor  656  implements various signal processing functions of the L1 layer. The RX processor  656  performs spatial processing on the information to recover any spatial streams destined for the UE  650 . If multiple spatial streams are destined for the UE  650 , they may be combined by the RX processor  656  into a single OFDM symbol stream. The RX processor  656  then converts the OFDM symbol stream from the time-domain to the frequency domain using a Fast Fourier Transform (FFT). The frequency domain signal comprises a separate OFDM symbol stream for each subcarrier of the OFDM signal. The symbols on each subcarrier, and the reference signal, is recovered and demodulated by determining the most likely signal constellation points transmitted by the eNB  610 . These soft decisions may be based on channel estimates computed by the channel estimator  658 . The soft decisions are then decoded and deinterleaved to recover the data and control signals that were originally transmitted by the eNB  610  on the physical channel. The data and control signals are then provided to the controller/processor  659 . 
     The controller/processor  659  implements the L2 layer. The controller/processor can be associated with a memory  660  that stores program codes and data. The memory  660  may be referred to as a computer-readable medium. In the UL, the control/processor  659  provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing to recover upper layer packets from the core network. The upper layer packets are then provided to a data sink  662 , which represents all the protocol layers above the L2 layer. Various control signals may also be provided to the data sink  662  for L3 processing. The controller/processor  659  is also responsible for error detection using an acknowledgement (ACK) and/or negative acknowledgement (NACK) protocol to support HARQ operations. 
     In the UL, a data source  667  is used to provide upper layer packets to the controller/processor  659 . The data source  667  represents all protocol layers above the L2 layer. Similar to the functionality described in connection with the DL transmission by the eNB  610 , the controller/processor  659  implements the L2 layer for the user plane and the control plane by providing header compression, ciphering, packet segmentation and reordering, and multiplexing between logical and transport channels based on radio resource allocations by the eNB  610 . The controller/processor  659  is also responsible for HARQ operations, retransmission of lost packets, and signaling to the eNB  610 . 
     Channel estimates derived by a channel estimator  658  from a reference signal or feedback transmitted by the eNB  610  may be used by the TX processor  668  to select the appropriate coding and modulation schemes, and to facilitate spatial processing. The spatial streams generated by the TX processor  668  are provided to different antenna  652  via separate transmitters  654 TX. Each transmitter  654 TX modulates an RF carrier with a respective spatial stream for transmission. 
     The UL transmission is processed at the eNB  610  in a manner similar to that described in connection with the receiver function at the UE  650 . Each receiver  618 RX receives a signal through its respective antenna  620 . Each receiver  618 RX recovers information modulated onto an RF carrier and provides the information to a RX processor  670 . The RX processor  670  may implement the L1 layer. 
     The controller/processor  675  implements the L2 layer. The controller/processor  675  can be associated with a memory  676  that stores program codes and data. The memory  676  may be referred to as a computer-readable medium. In the UL, the control/processor  675  provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing to recover upper layer packets from the UE  650 . Upper layer packets from the controller/processor  675  may be provided to the core network. The controller/processor  675  is also responsible for error detection using an ACK and/or NACK protocol to support HARQ operations. 
       FIG. 7A  is a diagram  750  illustrating an example of an evolved MBMS (eMBMS) channel configuration in an MBSFN. The eNBs  752  in cells  752 ′ may form a first MBSFN area and the eNBs  754  in cells  754 ′ may form a second MBSFN area. The eNBs  752 ,  754  may each be associated with other MBSFN areas, for example, up to a total of eight MBSFN areas. A cell within an MBSFN area may be designated a reserved cell. Reserved cells do not provide multicast/broadcast content, but are time-synchronized to the cells  752 ′,  754 ′ and have restricted power on MBSFN resources in order to limit interference to the MBSFN areas. Each eNB in an MBSFN area synchronously transmits the same eMBMS control information and data. Each area may support broadcast, multicast, and unicast services. A unicast service is a service intended for a specific user, e.g., a voice call. A multicast service is a service that may be received by a group of users, e.g., a subscription video service. A broadcast service is a service that may be received by all users, e.g., a news broadcast. Referring to  FIG. 7A , the first MBSFN area may support a first eMBMS broadcast service, such as by providing a particular news broadcast to UE  770 . The second MBSFN area may support a second eMBMS broadcast service, such as by providing a different news broadcast to UE  760 . Each MBSFN area supports a plurality of physical multicast channels (PMCH) (e.g., 15 PMCHs). Each PMCH corresponds to a multicast channel (MCH). Each MCH can multiplex a plurality (e.g., 29) of multicast logical channels. Each MBSFN area may have one multicast control channel (MCCH). As such, one MCH may multiplex one MCCH and a plurality of multicast traffic channels (MTCHs) and the remaining MCHs may multiplex a plurality of MTCHs. 
     A UE can camp on an LTE cell to discover the availability of eMBMS service access and a corresponding access stratum configuration. In a first step, the UE acquires a system information block (SIB) (SIB13). In a second step, based on the SIB, the UE acquires an MBSFN Area Configuration message on an MCCH. In a third step, based on the MBSFN Area Configuration message, the UE acquires an MCH scheduling information (MSI) MAC control element. The SIB, e.g., SB13 include (1) an MBSFN area identifier of each MBSFN area supported by the cell; (2) information for acquiring the MCCH such as an MCCH repetition period (e.g., 32, 64, . . . , 256 frames), an MCCH offset (e.g., 0, 1, . . . , 10 frames), an MCCH modification period (e.g., 512, 1024 frames), a signaling modulation and coding scheme (MCS), subframe allocation information indicating which subframes of the radio frame as indicated by repetition period and offset can transmit MCCH; and (3) an MCCH change notification configuration. There may be one MBSFN Area Configuration message for each MBSFN area. The MBSFN Area Configuration message include (1) a temporary mobile group identity (TMGI) and an optional session identifier of each MTCH identified by a logical channel identifier within the PMCH, (2) allocated resources (i.e., radio frames and subframes) for transmitting each PMCH of the MBSFN area and the allocation period (e.g., 4, 8, . . . , 256 frames) of the allocated resources for all the PMCHs in the area, and (3) an MCH scheduling period (MSP) (e.g., 8, 16, 32, . . . , or 1024 radio frames) over which the MSI MAC control element is transmitted. 
       FIG. 7B  is a diagram  790  illustrating the format of an MSI MAC control element. The MSI MAC control element may be sent once each MSP. The MSI MAC control element may be sent in the first subframe of each scheduling period of the PMCH. The MSI MAC control element can indicate the stop frame and subframe of each MTCH within the PMCH. There is one MSI per PMCH per MBSFN area. 
       FIG. 8  is a diagram illustrating an access network  800  that employs eMBMS. In this example, the access network  800  is divided into a number of cells  802  and  812 , where cells  812  belong to an MBSFN. In the cells  812  of an MBSFN area  814 , an eNB  804   a  or  804   b  or group of eNBs  804   a  or  804   b  may transmit a data stream using one or more transmission layers (represented by lines  808  and  810 ). Although each eNB  804   a,    804   b  in  FIG. 8  is illustrated within a single MBSFN cell  812 , an eNB may support one or multiple (e.g., three) cells. Accordingly, the terms “eNB” and “cell” may be used interchangeably herein. In other words, when an eNB is described herein as transmitting a signal, such transmission may encompass—in some cases—a transmission of the same signal by all cells supported by that eNB, and in other cases, a transmission by one or more, but not necessarily all, of the cells supported by that eNB. Likewise, when a cell is described herein as transmitting a signal, such transmission may encompass—in some cases—a transmission of the same signal by all cells supported by an eNB, and in other cases, a transmission by one or more, but not necessarily all, of the cells supported by that eNB. The eNBs  804   a  and  804   b  may have multiple antennas and may employ MIMO technology to exploit the spatial domain to obtain signal diversity and to support spatial multiplexing. Signal diversity may be obtained by transmitting a data stream in identical signals emitted from a plurality of transmit antennas. Intra-site MIMO can be used in a particular cell  812  when both eNB  804   a  and the UE  806  are equipped with a plurality of antennas. In inter-site MIMO, spatial diversity may also be obtained by virtue of the geographical separation of eNBs  804   a  and  804   b.  Signals from eNBs  804   a  and  804   b  may be combined at the UE  806  to benefit from multiplexing gain. Aspects of this disclosure will be described with respect to the inter-site MIMO example, but certain underlying principles relate equally to intra-site MIMO. 
     Certain embodiments employ spatial multiplexing to split a signal, such as a high data rate signal, into multiple lower rate data streams. The lower rate data streams may then be transmitted with different spatial coding in different transmission layers using the same frequency channel. In  FIG. 8 , different transmission layers are depicted as solid line  808  and dotted line  810 , respectively. In the example, two transmission layers  808  and  810  are available when the UE  806  has at least two receive antennas. Some embodiments use more than two transmission layers and the spatial coding may take advantage of the multiple antennas employed by eNBs  804   a  and  804   b.  UE  806  may recover the data streams when the signals arrive at the antenna array of the UE  806  with sufficiently different spatial signatures. A spatial signature may characterize certain aspects of a signal arriving at an antenna array at a certain location, such as the direction of arrival of the signal, etc. 
     In some embodiments, all eNBs  804   a  and  804   b  in the MBSFN area  814  transmit the same eMBMS control information and data stream in a synchronous manner, whereby the eNBs  804   a  and  804   b  transmit the same signal at the same time. In some embodiments, each eNB  804   a  or  804   b  within the MBSFN area  814  may be configured to use one or more transmission layers  808  and  810  to carry the data stream. In one example, each eNB  804   a  or  804   b  may be assigned to a single transmission layer  808  or  810  and may transmit the entire data stream over the assigned transmission layer  808  or  810 . In another example, eNB  804   a  and  804   b  may spatially multiplex the data stream, transmitting portions of the data stream in two or more transmission layers  808  and  810 . For example, the data stream may be divided by allocating different sets of resource blocks in the data stream to sets of resource blocks assigned to two or more transmission layers  808  and  810 . 
     In some embodiments, one or more eNBs  804   a  transmit a data stream in one transmission layer  808  while at least one other eNB  804   b  transmits a different data stream concurrently in another transmission layer  810 . The transmission of different waveforms in different layers by different cells, available through MIMO, is distinct over conventional eMBMS where each cell transmits the same waveform. The assignment of a transmission layer  808  or  810  to a cell  812  may be based on a configuration provided to the eNBs  804   a  and  804   b.  In one example, the assignment of transmission layer  808  or  810  may be based on the PCI assigned to each eNB  804   a  or  804   b  during network planning. For example, eNBs with an even PCI may be assigned to one transmission layer while eNBs with an odd PCI may be assigned to another transmission layer. 
     The assignment of a transmission layer  808  or  810  may change after a period of time, or after a reconfiguration of eNBs  804   a  and  804   b.  Changes in assignment may be periodic and the frequency of change may be provided to the eNBs through a configuration provided by a management function of the MBSFN. In some embodiments, eNBs  804   a  and  804   b  may be reassigned between transmission layers  808  and  810  according to a function of time, typically defined by a configuration. The assignment of transmission layers  808  and  810  to eNBs  804   a  and  804   b  may also be based on an MBSFN area identifier or some combination of PCI, a specified time, a function of time, and MBSFN area identifier. 
     In some embodiments, the assignment of transmission layers  808  and  810  may be controlled or configured by an OAM service of the network or MBSFN, by an MCE service of the network or MBSFN, or by some other management or control function. The OAM may provide backhaul configuration services related to the MBSFN in an LTE system. An MCE may be provided in an MBSFN to allocate radio resources used by eNBs  804   a  and  804   b  for eMBMS transmissions in the MBSFN area. An OAM or MCE may implement changes by providing updated configuration information to the eNBs  804   a  and  804   b  that causes the eNBs  804   a  and  804   b  to select one or more transmission layers  808  and  810  for transmitting the data stream. 
     In some embodiments, spatial multiplexing is used in an MBSFN to transmit data streams using two or more transmission layers  808  and  810 , whereby resource blocks are grouped into a plurality of sets or groups of resource blocks. Each group of resource blocks may comprise a plurality of consecutive resource blocks. For example, 25 resource blocks may be assigned to 5 groups where each group comprises 5 consecutive resource blocks. In some embodiments, the 25 resource blocks may be assigned to a different number of groups, each group having a minimum number of consecutive resource blocks. For example, 5 groups of four consecutive resource blocks and one group of five resource blocks. In certain embodiments, a common grouping structure for resource blocks is shared by all eNBs  804   a  and  804   b.    
     Each group of resource blocks may be assigned to at least one transmission layer  808  or  810  by each eNB  804   a  and  804   b.  For example, an eNB  804   a  or  804   b  may randomly select one or more resource block groups for transmission in a first transmission layer  808  or  810  and may additionally select one or more groups of resource for transmission in a second transmission layer  810  or  808 . Each eNB  804   a  and  804   b  transmits on all of the resource block groups. In one example, the eNB  804   a  or  804   b  may use a random seed value to select the resource block groups for transmission in each available transmission layer  808  and  810 . The random seed may be generated using, for example, one or more of a PCI, an MBSFN area ID, and a time value. 
     The assignment of transmission layers  808  and  810  and the allocation of resource block groups among transmission layers  808  and  810  may be defined in a layer pattern. In some embodiments different random layer patterns are used by an eNB  804   a  and  804   b  to determine which resource block groups to transmit in transmission layers  808  and  810 . The randomness of the layer pattern may be limited by policies that restrict allocation of resource blocks between transmission layers  808  and  810 . In one example, the layer pattern policies may limit the granularity of the sets of resource blocks, where granularity may describe a minimum number of resource blocks allocated to a set of resource blocks, and/or the minimum number of adjacent resource blocks to be provided in a set of resource blocks. Limits on the granularity of the layer pattern may be defined to obtain a balance between subframe diversity and quality of channel estimation by controlling the degree to which resource blocks can be allocated between two or more transmission layers  808  and  810 . 
       FIG. 9  illustrates a simple example  900  of resource block allocation using a portion of the resource blocks  902  in a subframe for the purpose of illustration. The resource blocks  902  may be assigned to resource block groups  904 ,  906 ,  908  and  910 . Each group  904 ,  906 ,  908  and  910  comprises a plurality of the resource blocks  902 . The resource blocks  902  assigned to each group  904 ,  906 ,  908  and  910  are consecutive and a minimum number of consecutive resource blocks  902  are typically assigned to each group  904 ,  906 ,  908  and  910 . The resource block mapping is typically shared by all eNBs  912 ,  914 , and  916  in an MBSFN. 
     Each of the groups  904 ,  906 ,  908  and  910  is transmitted by each eNB  912 ,  914 , and  916 . Each eNB  912 ,  914 , and  916  may allocate some or all of the groups  904 ,  906 ,  908  and  910  for transmission on one or more of the available transmission layers  918  and  920 . In the depicted example, one eNB  912  transmits two groups  904  and  908  in transmission layer  918  and transmits two groups  906  and  910  in transmission layer  920 . Two other eNBs  914  and  916  transmit three groups  906 ,  908 , and  910  in transmission layer  918  and transmit one group  904  in transmission layer  920 . The transmission layer patterns for each eNB  912 ,  914  and  916  may be randomly generated by each eNB  912 ,  914  and  916 . In some embodiments, transmission layer patterns are provided to each eNB  912 ,  914  and  916  in an MBSFN configuration provided, for example, by an MBSFN service provider. 
     Referring back to  FIG. 8 , a transmission layer pattern may change periodically or according to a function of time. Changes in the random layer pattern may be made for operational and other considerations, including operational characteristics of eNBs  804   a  and  804   b,  the nature of the information carried in the transmission layers  808  and  810 , and other factors such as changes to the physical configuration of the MBSFN area. 
     The MBSFN may include cells  812  that are geographically distant from one another, and the UE  806  may receive transmissions from eNBs  804   a  and  804   b  through propagation paths that have significantly different path lengths. Differences in propagation path lengths may result in a relative delay between signals received by the UE  806  from different eNBs  804   a  and  804   b.  In order to enable a UE  806  to combine signals received with this relative delay, the MBSFN may define a cyclic prefix that accommodates differences in arrival times of signals transmitted by the eNBs  804   a  and  804   b  of the MBSFN. The cyclic prefix is typically selected to exceed the difference time between receipt of a first symbol in a transmission from an eNB  804   a  or  804   b  that has the shortest propagation path to the UE  806  and the receipt of the same first symbol from an eNB  804   a  or  804   b  that has the longest propagation path to the UE  806 . When the cyclic prefix is a sufficiently long duration, data streams from all eNBs  804   a  and  804   b  may be coherently combined (herein referred to as “MBSFN gain”) and signals from eNB  804   a  or  804   b  can be received with minimal interference from the transmission from another eNB  804   a  or  804   b.    
     A longer cyclic prefix may increase the number of eNBs  804   a  and  804   b  available to contributed to MBSFN gain at the UE  806  because high-powered, geographically remote eNBs  804   a  and  804   b  may contribute to MBSFN gain as seen by the UE  806 . The high-powered eNBs  804   a  and  804   b  may also use omni-directional antennas for better MBSFN coverage rather than sectorized antennas, which are used in other systems to reduce interference between neighboring sectors. In eMBMS, signals from neighboring sectors of the MBSFN do not typically interfere, and may be combined to increase MBSFN gain. 
     UE  806  performance may be improved when the same data stream is received from a large number of eNBs  804   a  or  804   b  located in the MBSFN. Greater transmitter power and omni-directional antennas can increase the number of eNBs  804   a  and  804   b  that contribute to MBSFN gain at the UE  806  because signals from all cells can be combined coherently, and without interference, when a suitable cyclic prefix is used. In particular, the MBSFN gain at the UE  806  may be optimized when eNBs  840   a  and  804   b  use inter-site MIMO with multiple transmission layers. 
       FIG. 10  is a flow chart  1000  of a method of wireless communication. The method may be performed by a first cell, e.g., eNB  804   a.  At step  1002 , the first cell receives a configuration comprising information identifying a plurality of transmission layers (e.g., first and second transmission layers  808  and  810 ) in a multi-layer spatial multiplexing scheme of an MBSFN. In some embodiments, the configuration may identify groups or sets of resource blocks and assignments of resource blocks to the transmission layers  808  and  810 . In some embodiments, the configuration may identify seed values for pattern generation and timing information used to change resource block allocations and assignments. In some embodiments, the configuration may define an allocation of resource blocks to each of a first set and a second set of resource blocks. In some embodiments, resource blocks are allocated to the first and second sets of resource blocks and the first and second sets of resource blocks are assigned to the first and second transmission layers  808  and  810  by an operation and maintenance service provider of the MBSFN. In some embodiments, resource blocks are allocated to the first and second sets of resource blocks and the first and second sets of resource blocks are assigned to first and second transmission layers  808  and  810  by an OAM or an MCE service provider of the MBSFN. 
     At step  1004 , the first cell may transmit a first set of resource blocks from the first cell during a first period of time, the transmission using a first transmission layer  808  to a UE  806  located in the MBSFN. In some embodiments, at least one other cell (e.g. a second eNB  804   a  or  804   b ) located in the MBSFN concurrently transmits a second set of resource blocks to the UE  806  in a second transmission layer  810 . In some embodiments, the first and second sets of resource blocks comprise the same resource blocks. In some embodiments, a plurality of cells transmit the first set of resource blocks to the UE  806  in the first transmission layer  808  during the first period of time. In some embodiments, signals from the plurality of cells arrive at the UE  806  at different times, and a cyclic prefix is defined for the MBSFN that has a duration selected to enable the UE to coherently combine the signals that arrive from the plurality of cells. 
     In some embodiments, the first eNB  804   a  transmits the first set of resource blocks in the first transmission layer  808  in accordance with an assignment of the first eNB  804   a  to the first transmission layer  808 . In some embodiments, the assignment may be provided in the configuration. In some embodiments, the first transmission layer  808  is assigned to the first eNB  804   a  based on a PCI associated with the first eNB  804   a.  In some embodiments, the first transmission layer  808  is assigned to the first eNB  804   a  based on an MBSFN area identifier. 
     In some embodiments, the first set of resource blocks is different from the second set of resource blocks. In some embodiments, the first eNB  804   a  also transmits the second set of resource blocks to the UE  806  in the second transmission layer during the first period of time. 
     At step  1006 , the first cell may determine whether to change the allocation of resource blocks to sets of resource blocks and/or to change the assignment of sets of resource blocks to transmission layers. Such determinations may be based on a current configuration or new configuration received in step  1002 . In some embodiments, the first cell is reassigned to the second transmission layer  810  during a second period of time. In some embodiments, the first eNB  804   a  transmits resource blocks only in its currently assigned transmission layer  808  or  810 . It may also be determined that the first cell is to be reassigned to a different transmission layer  810  or  808 . The first eNB  804   a  may initiate the reassignments based on a function of time. 
     At step  1008 , if it is determined that resource blocks do not need to reallocated and transmission layers do not require reassignment, the process returns to step  1004 . If, however, resource blocks are to be reallocated or transmission layers are to be reassigned, the process proceeds to step  1010 , where the first eNB  804   a  may perform a reconfiguration such that a data stream is transmitted during a second period time using a different combination of transmission layers and sets of resource blocks that differs from the combination used in the first period of time. For example, the first eNB may determine that resource blocks should be transmitted in the second transmission layer  810 . The decision may be based on a configuration whereby the first eNB  804   a  transmits some resource blocks in both the first and second transmission layers  808  and  810  or based on a change in configuration that results in first eNB  804   a  selecting a different transmission layer  808  or  810 . 
     In some embodiments, at least two eNBs  804   a  and  804   b  transmit the first set of resource blocks to the UE  806  in the first transmission layer during the first period of time. In some embodiments, an eNB  804   a  or  804   b  selects at least one transmission layer from a plurality of transmission layers for transmitting. One or more sets of resource blocks are transmitted in each of the plurality of transmission layers  808  and  810 . 
     In some embodiments, the first cell transmits the first set of resource blocks in a first transmission layer  808  or  810  and a second set of resource blocks in the second transmission layer  810  or  808  based on a layer pattern provided by the configuration. In some embodiments, the first eNB  804   a  uses a combination of transmission layers  808  and  810  and sets of resource blocks during a second period of time that is different from the combination of transmission layers  810  and  808  and sets of resource blocks used during a first period of time. 
     In an aspect of the disclosure, another cell different from the first cell, such as eNB  804   b,  transmits at least one resource block to the UE  806  in the first transmission layer  808  during the first period of time, where the at least one resource block is not also transmitted by the first eNB  804   a  in the first transmission layer  808  during the first period of time. The first eNB  804   a  may transmit at least one resource block in the first transmission layer  808  that is also transmitted by the another eNB  804   b  in the first transmission layer  808  during the first period of time. The first set of resource blocks may include a group comprising minimum number of adjacent or consecutive resource blocks. The resource blocks may be grouped according to a pattern defined for the MBSFN. Transmitting a first set of resource blocks may include randomly selecting one or more resource block to be transmitted in the first transmission layer  808  and one or more resource blocks to be transmitted in the second transmission layer  810 . The first cell may transmit a selection of resource blocks in the first and second transmission layers  808  and  810  during a second period of time that is different than the selection of resource blocks that is transmitted in the first and second transmission layers  808  and  810  during the first period of time. 
     In some embodiments, the first eNB  804   a  is configured to randomly select one or more sets of resource blocks for transmission. In some embodiments, the first eNB  804   a  transmits each randomly selected set of resource blocks in a first or second transmission layer  808  or  810  assigned by the configuration. In some embodiments, the one or more sets of resource blocks comprise resource blocks selected using a random layer pattern. In some embodiments, the random layer pattern defines a minimum number of resource blocks included in each set of resource blocks. In some embodiments, the random layer pattern defines a minimum number of adjacent resource blocks included in each set of resource blocks. In some embodiments, the random layer pattern used during the first period of time is different from a random layer pattern used during a second period of time. 
       FIG. 11  is a conceptual data flow diagram  1100  illustrating the data flow between different modules/means/components in an exemplary apparatus  1102 . The apparatus  1102  may be a first cell, e.g., eNB  804   a,  located within an MBSFN having a second cell, e.g., eNB  804   b,  therein. The first eNB  1102  includes a configuration receiving module  1104  that receives a signal  1110  including a configuration from, for example, a MBSFN service provider  1108 . The configuration includes information identifying a plurality of transmission layers in a multi-layer spatial multiplexing scheme. The first eNB  1102  also includes a transmission module  1106  that transmits a signal  1112  including a first set of resource blocks from the first eNB during a first period of time concurrent with transmission of a signal  1114  including a second set of resource blocks from a second eNB  1116  during the first period of time. The first set of resource blocks is transmitted in a first transmission layer to an UE  1118  located in the MBSFN, and the second set of resource blocks is transmitted in a second transmission layer to the UE. The transmission module  1106  transmits resource blocks in accordance with configuration information  1120  from the configuration receiving module  1104 . 
     The apparatus may include additional modules that perform each of the steps of the algorithm in the aforementioned flow chart of  FIG. 10 . As such, each step in the aforementioned flow chart of  FIG. 10  may be performed by a module and the apparatus may include one or more of those modules. The modules may be one or more hardware components specifically configured to carry out the stated processes/algorithm, implemented by a processor configured to perform the stated processes/algorithm, stored within a computer-readable medium for implementation by a processor, or some combination thereof. 
       FIG. 12  is a diagram  1200  illustrating an example of a hardware implementation for an eNB  1102 ′ employing a processing system  1214 . The processing system  1214  may be implemented with a bus architecture, represented generally by the bus  1224 . The bus  1224  may include any number of interconnecting buses and bridges depending on the specific application of the processing system  1214  and the overall design constraints. The bus  1224  links together various circuits including one or more processors and/or hardware modules, represented by the processor  1204 , the modules  1104 ,  1106  and the computer-readable medium  1206 . The bus  1224  may also link various other circuits such as timing sources, peripherals, voltage regulators, and power management circuits, which are well known in the art, and therefore, will not be described any further. 
     The processing system  1214  may be coupled to a transceiver  1210 . The transceiver  1210  is coupled to one or more antennas  1220 . The transceiver  1210  provides a means for communicating with various other apparatus over a transmission medium. The transceiver  1210  receives a signal from the one or more antennas  1220 , extracts information from the received signal, and provides the extracted information to the processing system  1214 , specifically the configuration receiving module  1104 . In addition, the transceiver  1210  receives information from the processing system  1214 , specifically the transmission module  1106 , and based on the received information, generates a signal to be applied to the one or more antennas  1220 . The processing system  1214  includes a processor  1204  coupled to a computer-readable medium  1206 . The processor  1204  is responsible for general processing, including the execution of software stored on the computer-readable medium  1206 . The software, when executed by the processor  1204 , causes the processing system  1214  to perform the various functions described supra for any particular apparatus. The computer-readable medium  1206  may also be used for storing data that is manipulated by the processor  1204  when executing software. The processing system further includes at least one of the modules  1104  and  1106 . The modules may be software modules running in the processor  1204 , resident/stored in the computer readable medium  1206 , one or more hardware modules coupled to the processor  1204 , or some combination thereof. The processing system  1214  may be a component of the eNB  610  and may include the memory  676  and/or at least one of the TX processor  616 , the RX processor  670 , and the controller/processor  675 . 
     In one configuration, the eNB  1102 / 1102 ′ includes means for receiving a configuration at a first eNB  804   a  or  804   b  in a MBSFN. The configuration identifies a plurality of transmission layers  808  and  810  in a multi-layer spatial multiplexing scheme. In some embodiments, the configuration may identify resource block allocations to sets of resource blocks and assignments of sets to transmission layers  808  and  810 , seed values for pattern generation, and timing information used to resource block allocation to transmission layers  808  and  810 . In some embodiments, the configuration may define an allocation of resource blocks to each of a first set and a second set of resource blocks. In some embodiments, resource blocks are allocated to the first and second sets of resource blocks and the first and second sets of resource blocks are assigned to the first and second transmission layers  808  and  810  by an operation and maintenance service provider of the MBSFN. In some embodiments, resource blocks are allocated to the first and second sets of resource blocks and the first and second sets of resource blocks are assigned to first and second transmission layers  808  and  810  by an OAM or an MCE service provider of the MBSFN. 
     In one configuration, the eNB  1102 / 1102 ′ includes means for transmitting a first set of resource blocks from the first eNB  804   a  during a first period of time, the transmission using a first transmission layer  808  to a UE  806  located in the MBSFN. The means for transmitting may comprise a plurality of antennas  620 , corresponding transceivers  618  and one or more TX processor  616 . In some embodiments, at least one other cell, e.g., eNB  804   b,  located in the MBSFN concurrently transmits a second set of resource blocks to the UE  806  in a second transmission layer  810 . In some embodiments, the first and second sets of resource blocks comprise the same resource blocks. In some embodiments, a plurality of first cells transmit the first set of resource blocks to the UE  806  in the first transmission layer  808  during the first period of time. In some embodiments, signals from the plurality of first cells arrive at the UE  806  at different times, and a cyclic prefix is defined for the MBSFN that has a duration selected to enable the UE to coherently combine the signals that arrive from the plurality of eNBs  804   a.    
     In some embodiments, the first cell may transmit the first set of resource blocks in the first transmission layer  808  using the means for transmitting and in accordance with an assignment of the first cell to the first transmission layer  808 , the assignment being provided by the configuration. In some embodiments, the first transmission layer  808  is assigned to the first cell based on a PCI associated with the first cell. In some embodiments, the first transmission layer  808  is assigned to the first cell based on an MBSFN area identifier. In some embodiments, the first set of resource blocks is different from the second set of resource blocks. In one configuration, the means for transmitting is configured to transmit the second set of resource blocks to the UE  806  in the second transmission layer during the first period of time. 
     The means for receiving a configuration may determine whether to change configuration or adopt a new configuration that changes the allocation of resource blocks to sets of resource blocks and/or changes the assignment of sets of resource blocks to transmission layers. In some embodiments, the first cell is reassigned to the second transmission layer  810  during a second period of time. In some embodiments, the first cell transmits resource blocks only in its currently assigned transmission layer  808  or  810 . In some embodiments, the means for receiving a configuration determines that the first cell should be reassigned to the second transmission layer  810 . The reassignment may be initiated based on a function of time. The first and second eNBs  804   a  and  804   b  may be reconfigured to transmit a data stream in a second period time using a different combination of transmission layers and sets of resource blocks that is different than the combination used in the first period of time. Reassignment of the first and second transmission layers  808  and  810  may include changing assigning certain antenna of the plurality of antennas  620  to obtain a desired spatial coding of the signals transmitted by the first cell and/or the second cell  804   b.    
     Optionally, the means for receiving a configuration may determine whether the first eNB  804   a  is to transmit resource blocks in the second transmission layer  810 . The decision may be based on a configuration whereby the first eNB  804   a  transmits some resource blocks in both the first and second transmission layers  808  and  810  or based on a change in configuration that results in first eNB  804   a  selecting a different transmission layer  808  or  810 . 
     In some embodiments, the first cell transmits the first set of resource blocks in a first transmission layer  808  and a second set of resource blocks in the second transmission layer  810  based on a layer pattern provided by the configuration. In some embodiments, the first cell uses a combination of first and second transmission layers  808  and  810  and sets of resource blocks during a second period of time that is different from the combination of first and second transmission layers  810  and  808  and sets of resource blocks used during a first period of time. 
     Referring again to  FIG. 9 , in some embodiments, a first eNB  912  is configured to randomly select between one or more transmission layers  918  and  920  for transmitting each of one or more resource block groups  904 ,  906 ,  908 , and  910 . Other eNBs  914  and  916  may transmit different combinations of groups  904 ,  906 ,  908 , and  910  in the one or more transmission layers  918  and  920 . In some embodiments, each eNB  912 ,  914 , and  916  transmits all resource block groups  904 ,  906 ,  908 , and  910 . In some embodiments, resource block groups  904 ,  906 ,  908 , and  910  are assigned to transmission layers  918  and  920  by the configuration. In some embodiments, the resource block groups  904 ,  906 ,  908 , and  910  are allocated for transmission in the one or more transmission layers  918  and  920  using a random layer pattern. The random layer patter may be defined by the MNSFN and may be common to all  912 ,  914 , and  916  in the MBSFN. In some embodiments, the random layer pattern defines a minimum number of resource blocks included in each set of resource blocks. In some embodiments, the random layer pattern defines a minimum number of adjacent or consecutive resource blocks included in each set of resource blocks. In some embodiments, the random layer pattern used during the first period of time is different from a random layer pattern used during a second period of time. 
     Referring again to  FIG. 8 , in some embodiments, the means for transmitting may cause another cell, e.g.,  804   b,  to transmit at least one resource block to the UE  806  in the first transmission layer  808  during the first period of time, where the at least one resource block is not also transmitted by the first eNB  804   a  in the first transmission layer  808  during the first period of time. Alternatively, the first eNB  804   a  may transmit at least one resource block in the first transmission layer  808  that is also transmitted by the another eNB  804   b  in the first transmission layer  808  during the first period of time. The first set of resource blocks may include a minimum number of adjacent resource blocks. Transmitting a first set of resource blocks may include randomly selecting one or more resource block to be transmitted in the first transmission layer  808  and one or more resource blocks to be transmitted in the second transmission layer  810 . The first eNB  804   a  may transmit a selection of resource blocks in the first and second transmission layers  808  and  810  during a second period of time that is different than the selection of resource blocks that is transmitted in the first and second transmission layers  808  and  810  during the first period of time. 
     Each of the aforementioned means may be one or more of the aforementioned modules  1104  and  1106  of the apparatus  1102  and/or the processing system  1214  of the apparatus  1102  configured to perform the functions recited by the aforementioned means. As described supra, the processing system  1214  may include the TX Processor  616 , the RX Processor  670 , and the controller/processor  675 . As such, in one configuration, the aforementioned means may be the TX Processor  616 , the RX Processor  670 , and the controller/processor  675  configured to perform the functions recited by the aforementioned means. 
     It is understood that the specific order or hierarchy of steps in the processes disclosed is an illustration of exemplary approaches. Based upon design preferences, it is understood that the specific order or hierarchy of steps in the processes may be rearranged. Further, some steps may be combined or omitted. The accompanying method claims present elements of the various steps in a sample order, and are not meant to be limited to the specific order or hierarchy presented. 
     The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more.” Unless specifically stated otherwise, the term “some” refers to one or more. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed as a means plus function unless the element is expressly recited using the phrase “means for.”