Abstract:
Methods, systems, apparatus and computer program products are provided for generating a shared initialization code for physical channel data scrambling in an LTE Advanced coordinated multipoint transmission network. This Abstract is provided for the sole purpose of complying with the Abstract requirement rules that allow a reader to quickly ascertain the disclosed subject matter. Therefore, it is to be understood that it should not be used to interpret or limit the scope or the meaning of the claims.

Description:
[0001]    The present application claims priority to U.S. Provisional Patent Application Ser. No. 61/247,114, entitled “PDSCH Scrambling Sequence Initialization for LTE-A,” filed Sep. 30, 2009, the entirety of which is hereby incorporated by reference. 
     
    
     FIELD OF INVENTION 
       [0002]    The present invention relates generally to the field of wireless communications and, more particularly to the initialization of scrambling sequences used in physical channels in wireless communication systems. 
       BACKGROUND 
       [0003]    This section is intended to provide a background or context to the disclosed embodiments. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section. 
         [0004]    Wireless communication systems are widely deployed to provide various types of communication content such as voice, data, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., bandwidth and transmit power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, 3GPP Long Term Evolution (LTE) systems, and orthogonal frequency division multiple access (OFDMA) systems. 
         [0005]    An orthogonal frequency division multiplex (OFDM) communication system effectively partitions the overall system bandwidth into multiple subcarriers, which may also be referred to as frequency sub-channels, tones or frequency bins. For an OFDM system, the data to be transmitted (i.e., the information bits) is first encoded with a particular coding scheme to generate coded bits, and the coded bits are further grouped into multi-bit symbols that are then mapped to modulation symbols. Each modulation symbol corresponds to a point in a signal constellation defined by a particular modulation scheme (e.g., M-PSK or M-QAM) used for data transmission. At each time interval that may be dependent on the bandwidth of each frequency subcarrier, a modulation symbol may be transmitted on each of the frequency subcarriers. Thus, OFDM may be used to combat inter-symbol interference (ISI) caused by frequency selective fading, which is characterized by different amounts of attenuation across the system bandwidth. 
         [0006]    Generally, a wireless multiple-access communication system can concurrently support communication for multiple wireless terminals that communicate with one or more base stations via transmissions on forward and reverse links. The forward link (or downlink) refers to the communication link from the base stations to the terminals, and the reverse link (or uplink) refers to the communication link from the terminals to the base stations. This communication link may be established via a single-in-single-out, multiple-in-signal-out or a multiple-in-multiple-out (MIMO) system. 
         [0007]    A MIMO system employs multiple (N T ) transmit antennas and multiple (N R ) receive antennas for data transmission. A MIMO channel formed by the N T  transmit and N R  receive antennas may be decomposed into N S  independent channels, which are also referred to as spatial channels. Generally, each of the N S  independent channels corresponds to a dimension. The MIMO system can provide improved performance (e.g., higher throughput and/or greater reliability) if the additional dimensionalities created by the multiple transmit and receive antennas are utilized. A MIMO system also supports time division duplex (TDD) and frequency division duplex (FDD) systems. In a TDD system, the forward and reverse link transmissions are on the same frequency region so that the reciprocity principle allows estimation of the forward link channel from the reverse link channel. This enables an access point to extract transmit beam-forming gain on the forward link when multiple antennas are available at the access point. 
         [0008]    Coordinated multi-point (CoMP) communication that provides the possibility that two or more cells can serve the same user equipment (UE) concurrently to increase the signal to noise ration at the UE. With CoMP, two or more cells may transmit PDSCH resources to the same UE at substantially the same time, while one cell (the serving cell) manages control signaling on a physical downlink control channel (PDCCH). 
       SUMMARY 
       [0009]    The disclosed embodiments relate to systems, methods, apparatus and computer program products to generate a shared initialization code for generating a common scrambling sequence for PDSCH scrambling codes in coordinated multi-point (CoMP) transmission networks in advanced wireless communication systems 
         [0010]    In one embodiment, a method includes generating a shared initialization code in a serving cell of a coordinated multi-point (CoMP) transmission network, where the shared initialization code includes a virtual serving cell identifier, initializing a scrambling sequence generator with the shared initialization code, generating a scrambling sequence from the shared initialization code and generating scrambled data with the scrambling sequence. 
         [0011]    In one embodiment, the method includes sending the shared initialization code to another cell of the CoMP transmission network through a system controller coupled to the serving cell and the other cell of the CoMP transmission network. 
         [0012]    In another embodiment, the method includes transmitting the shared initialization code from the serving cell to a user equipment (UE) on a physical downlink control channel (PDCCH) and transmitting the scrambled data to the UE on a first physical downlink shared data channel (PSDCH). 
         [0013]    In one embodiment, the initialization code includes a user equipment (UE) identifier, a codeword index and a transmission slot index, where in one embodiment the UE identifier includes a virtual UE identifier, the codeword index includes one of a serving cell codeword index and a virtual codeword index, and the transmission slot index comprises one of a serving cell transmission slot index and a virtual transmission slot index. In another embodiment, the initialization code includes a codeword index, a transmission slot index and the virtual serving cell identifier. 
         [0014]    In one embodiment, the CoMP transmission network includes a plurality of cells. In another embodiment, the CoMP transmission network includes a single cell. 
         [0015]    In one embodiment, the method includes receiving the shared initialization code at the other CoMP cell and initializing a scrambling sequence generator in the other CoMP cell with the shared initialization code, generating the scrambling sequence with the shared initialization code, generating scrambled data with the scrambling sequence and transmitting the scrambled data to the UE on a second PDSCH. 
         [0016]    In one embodiment, the method includes receiving the shared initialization code at the UE, initializing a scrambling sequence generator in the UE with the shared initialization code, generating the scrambling sequence with the shared initialization code, receiving scrambled data on at least one of the first PDSCH and the second PDSCH and descrambling the scrambled data with the scrambling sequence. 
         [0017]    In one embodiment, another method includes generating a shared initialization code in a serving cell of a coordinated multi-point (CoMP) transmission network where the shared initialization code includes a serving cell identifier, sending the initialization code to another cell in the CoMP transmission network through a system controller coupled to the serving cell and the other cell of the CoMP transmission network and transmitting the shared initialization code from the serving cell to a user equipment (UE) on a physical downlink control channel (PDCCH). 
         [0018]    In one embodiment, the method also includes initializing a scrambling sequence generator with the shared initialization code, generating a scrambling sequence from the shared initialization code, generating scrambled data with the scrambling sequence and transmitting the scrambled data to a user equipment (UE) on a first physical downlink shared channel (PDSCH). 
         [0019]    In one embodiment, the method includes receiving the shared initialization code at the other CoMP cell, initializing a scrambling sequence generator in the other CoMP cell with the shared initialization code, generating the scrambling sequence with the shared initialization code, generating scrambled data with the scrambling sequence and transmitting the scrambled data to the UE on a second PDSCH. 
         [0020]    In one embodiment, the serving cell identifier includes a virtual serving cell identifier, a UE identifier, a codeword index and a transmission slot index, where in one aspect the UE identifier includes a virtual UE identifier. 
         [0021]    In one embodiment, the codeword index includes one of a serving cell codeword index and a virtual codeword index and the transmission slot index includes one of a serving cell slot index and a virtual transmission slot index. 
         [0022]    In one embodiment, the initialization code consists of the serving cell identifier, the codeword index and the transmission slot index. 
         [0023]    In one embodiment, the method includes receiving the shared initialization code at the UE, initializing a scrambling sequence generator in the UE with the shared initialization code, generating the scrambling sequence with the shared initialization code, receiving scrambled data on at least one of the first PDSCH and the second PDSCH, and descrambling the scrambled data with the scrambling sequence. 
         [0024]    In one embodiment, a method includes receiving components of a shared initialization code from a CoMP serving cell at a user equipment, where the components of the shared initialization code are configured to generate an uplink scrambling sequence for a CoMP transmission network, generating the shared initialization code to initialize a scrambling sequence generator for a physical uplink shared channel, transmitting the shared initialization code to a cell in the CoMP transmission network on a physical uplink control channel, wherein the cell in the CoMP transmission network is configured to descramble data on a physical uplink shared channel from the UE with a scrambling sequence generated from the shared initialization code, and transmitting the scrambled data to the cell in the CoMP transmission network on a physical uplink shared channel. 
         [0025]    In one embodiment, another method includes receiving at a user equipment (UE), a shared initialization code from a CoMP serving cell, the shared initialization code configured to generate a common scrambling sequence for a coordinated multi-point (CoMP) transmission network, and transmitting the shared initialization code to another cell in the CoMP transmission network. 
         [0026]    In one embodiment, the other cell in the CoMP transmission network is configured to scramble data with a scrambling sequence generated with the shared initialization code, and to transmit the scrambled data to the UE. 
         [0027]    In one embodiment, the method includes receiving scrambled data at the UE from at least one of the CoMP serving cell on a first PDSCH and the other cell in the CoMP transmission network on a second PDSCH. 
         [0028]    In one embodiment, the initialization code comprises a codeword index, a transmission slot index and a cell identifier. In one embodiment, the initialization code further comprises a UE identifier. In one embodiment, the UE identifier includes a virtual UE identifier. 
         [0029]    In one embodiment, the codeword index includes one of a serving cell codeword index and a virtual codeword index, the transmission slot index includes one of a serving cell transmission slot index and a virtual transmission slot index, and the cell identifier includes one of a serving cell identifier and a virtual cell identifier. 
         [0030]    In one embodiment, a serving cell in a CoMP transmission network includes a processor and a memory, where the memory includes processor executable instructions that, when executed by the processor, configure the serving cell to generate a shared initialization code for the CoMP transmission network, where the shared initialization code includes a virtual serving cell identifier, to initialize a scrambling sequence generator with the shared initialization code, to generate a scrambling sequence from the shared initialization code, and to generate scrambled data with the scrambling sequence. 
         [0031]    In one embodiment, the memory includes additional processor executable instructions that, when executed by the processor, configure the serving cell to send the shared initialization code to an other cell of the CoMP transmission network through a system controller coupled to the serving cell and the other cell of the CoMP transmission network 
         [0032]    In one embodiment, the memory also includes processor executable instructions that, when executed by the processor, configure the serving cell to transmit the shared initialization code from the serving cell to a user equipment (UE) on a physical downlink control channel (PDCCH). 
         [0033]    In one embodiment, the memory includes processor executable instructions that, when executed by the processor, configure the serving cell to transmit the scrambled data to the UE on a first physical downlink shared data channel (PSDCH). 
         [0034]    In one embodiment, the initialization code includes a user equipment (UE) identifier, a codeword index and a transmission slot index. In one embodiment, the UE identifier includes a virtual UE identifier, the codeword index includes one of a serving cell codeword index and a virtual codeword index, and the transmission slot index includes one of a serving cell transmission slot index and a virtual transmission slot index. 
         [0035]    In one embodiment, the initialization code comprises a codeword index, a transmission slot index and the virtual serving cell identifier. 
         [0036]    In one embodiment, a serving cell in a CoMP transmission network includes a processor and a memory including processor executable instructions that, when executed by the processor, configure the serving cell to generate a shared initialization code for the CoMP transmission network, where the shared initialization code includes a serving cell identifier, to send the initialization code to another cell in the CoMP transmission network through a system controller coupled to the serving cell and the other cell of the CoMP transmission network, and to transmit the shared initialization code to a user equipment (UE) on a physical downlink control channel (PDCCH). In one embodiment, the serving cell identifier includes a virtual serving cell identifier. 
         [0037]    In one embodiment, the memory further includes processor executable instructions that, when executed by the processor, configure the serving cell to initialize a scrambling sequence generator with the shared initialization code, to generate a scrambling sequence from the shared initialization code, to generate scrambled data with the scrambling sequence, and to transmit the scrambled data to a user equipment (UE) on a physical downlink shared channel (PDSCH). 
         [0038]    In one embodiment, the initialization code includes a UE identifier, a codeword index, a transmission slot index. In one embodiment, the UE identifier includes a virtual UE identifier. In one embodiment, the codeword index includes one of a serving cell codeword index and a virtual codeword index and the transmission slot index includes one of a serving cell slot index and a virtual transmission slot index. In one embodiment, the initialization code comprises the serving cell identifier, the codeword index and the transmission slot index. 
         [0039]    In one embodiment, a communication device includes a processor and a memory comprising processor executable instructions that, when executed by the processor, configure the communication device to receive a shared initialization code from a CoMP serving cell, the shared initialization code configured to generate a common scrambling sequence for a coordinated multi-point (CoMP) transmission network, and to transmit the shared initialization code to another cell in the CoMP transmission network. In one embodiment, the other cell in the CoMP transmission network is configured to scramble data with a scrambling sequence generated with the shared initialization code. 
         [0040]    In one embodiment, the memory further includes processor executable instructions that, when executed by the processor, configure the communication device to receive scrambled data from at least one of the CoMP serving cell on a first PDSCH and the other cell in the CoMP transmission network on a second PDSCH. 
         [0041]    In one embodiment, the initialization code comprises a codeword index, a transmission slot index and a cell identifier. In one embodiment, the initialization code further comprises a UE identifier. In one embodiment, the codeword index includes one of a serving cell codeword index and a virtual codeword index, the transmission slot index includes one of a serving cell transmission slot index and a virtual transmission slot index, and the cell identifier includes one of a serving cell identifier and a virtual cell identifier. In one embodiment, the UE identifier includes a virtual UE identifier. 
         [0042]    These and other features of various embodiments, together with the organization and manner of operation thereof, will become apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which like reference numerals are used to refer to like parts throughout. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0043]    Provided embodiments are illustrated by way of example, and not of limitation, in the figures of the accompanying drawings in which: 
           [0044]      FIG. 1  illustrates a wireless communication system; 
           [0045]      FIG. 2  illustrates a block diagram of a communication system; 
           [0046]      FIG. 3  illustrates a scrambling sequence generator in one embodiment; 
           [0047]      FIG. 4  illustrates a wireless communication system configured for coordinated multipoint transmission/reception in one embodiment; 
           [0048]      FIG. 5  is a block diagram illustrating a system configured to employ shared initialization codes for scrambling in one embodiment; 
           [0049]      FIG. 6  is a flowchart illustrating a method in an evolved node base station (eNodeB) in one embodiment; 
           [0050]      FIG. 7A  is a flowchart illustrating a method in a user equipment in one embodiment; 
           [0051]      FIG. 7B  is a flowchart illustrating another method in a user equipment in one embodiment; 
           [0052]      FIG. 8  illustrates a system in one embodiment; and 
           [0053]      FIG. 9  illustrates an exemplary apparatus for processing data in a wireless communication system. 
       
    
    
     DETAILED DESCRIPTION 
       [0054]    In the following description, for purposes of explanation and not limitation, details and descriptions are set forth in order to provide a thorough understanding of the various disclosed embodiments. However, it will be apparent to those skilled in the art that the various embodiments may be practiced in other embodiments that depart from these details and descriptions. 
         [0055]    As used herein, the terms “component,” “module,” “system” and the like are intended to refer to a computer-related entity, either hardware, firmware, a combination of hardware and software, software, or software in execution. For example, a component may be, but is not limited to being, a process running on a processor, a processor, an object, an executable, a thread of execution, a program and/or a computer. By way of illustration, both an application running on a computing device and the computing device can be a component. One or more components can reside within a process and/or thread of execution and a component may be localized on one computer and/or distributed between two or more computers. In addition, these components can execute from various computer readable media having various data structures stored thereon. The components may communicate by way of local and/or remote processes such as in accordance with a signal having one or more data packets (e.g., data from one component interacting with another component in a local system, distributed system, and/or across a network such as the Internet with other systems by way of the signal). 
         [0056]    Furthermore, certain embodiments are described herein in connection with a user equipment. A user equipment can also be called a user terminal, and may contain some or all of the functionality of a system, subscriber unit, subscriber station, mobile station, mobile wireless terminal, mobile device, node, device, remote station, remote terminal, terminal, wireless communication device, wireless communication apparatus or user agent. A user equipment can be a cellular telephone, a cordless telephone, a Session Initiation Protocol (SIP) phone, a smart phone, a wireless local loop (WLL) station, a personal digital assistant (PDA), a laptop, a handheld communication device, a handheld computing device, a satellite radio, a wireless modem card and/or another processing device for communicating over a wireless system. Moreover, various aspects are described herein in connection with a base station. A base station may be utilized for communicating with one or more wireless terminals and can also be called, and may contain some or all of the functionality of, an access point, node, Node B, evolved NodeB (eNB) or some other network entity. A base station communicates over the air-interface with wireless terminals. The communication may take place through one or more sectors. The base station can act as a router between the wireless terminal and the rest of the access network, which can include an Internet Protocol (IP) network, by converting received air-interface frames to IP packets. The base station can also coordinate management of attributes for the air interface, and may also be the gateway between a wired network and the wireless network. 
         [0057]    Various aspects, embodiments or features will be presented in terms of systems that may include a number of devices, components, modules, and the like. It is to be understood and appreciated that the various systems may include additional devices, components, modules, and so on, and/or may not include all of the devices, components, modules and so on, discussed in connection with the figures. A combination of these approaches may also be used. 
         [0058]    Additionally, in the subject description, the word “exemplary” is used to mean serving as an example, instance or illustration. Any embodiment or design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments or designs. Rather, use of the word exemplary is intended to present concepts in a concrete manner. 
         [0059]    The various disclosed embodiments may be incorporated into a communication system. In one example, such communication system utilizes an orthogonal frequency division multiplex (OFDM) that effectively partitions the overall system bandwidth into multiple (N F ) subcarriers, which may also be referred to as frequency sub-channels, tones or frequency bins. For an OFDM system, the data to be transmitted (i.e., the information bits) is first encoded with a particular coding scheme to generate coded bits, and the coded bits are further grouped into multi-bit symbols that are then mapped to modulation symbols. Each modulation symbol corresponds to a point in a signal constellation defined by a particular modulation scheme (e.g., M-PSK or M-QAM) used for data transmission. At each time interval, which may be dependent on the bandwidth of each frequency subcarrier, a modulation symbol may be transmitted on each of the N F  frequency subcarriers. Thus, OFDM may be used to combat inter-symbol interference (ISI) caused by frequency selective fading, which is characterized by different amounts of attenuation across the system bandwidth. 
         [0060]    Generally, a wireless multiple-access communication system can simultaneously support communication for multiple wireless terminals. Each terminal communicates with one or more base stations through transmissions on the forward and reverse links. The forward link (or downlink) refers to the communication link from the base stations to the terminals, and the reverse link (or uplink) refers to the communication link from the terminals to the base stations. This communication link can be established through a single-in-single-out, multiple-in-single-out or a multiple-in-multiple-out (MIMO) system. 
         [0061]    A MIMO system employs multiple (N T ) transmit antennas and multiple (N R ) receive antennas for data transmission. A MIMO channel formed by the N T  transmit and N R  receive antennas may be decomposed into N S  independent channels, which are also referred to as spatial channels, where N S ≦min{N T , N R }. Each of the N S  independent channels corresponds to a dimension. The MIMO system can provide improved performance (e.g., higher throughput and/or greater reliability) if the additional dimensionalities created by the multiple transmit and receive antennas are utilized. A MIMO system also supports time division duplex (TDD) and frequency division duplex (FDD) systems. In a TDD system, the forward and reverse link transmissions are on the same frequency region so that the reciprocity principle allows the estimation of the forward link channel from the reverse link channel. This enables the base station to extract transmit beamforming gain on the forward link when multiple antennas are available at the base station. 
         [0062]      FIG. 1  illustrates a wireless communication system within which the various disclosed embodiments may be implemented. A base station  100  may include multiple antenna groups, and each antenna group may comprise one or more antennas. For example, if the base station  100  comprises six antennas, one antenna group may comprise a first antenna  104  and a second antenna  106 , another antenna group may comprise a third antenna  108  and a fourth antenna  110 , while a third group may comprise a fifth antenna  112  and a sixth antenna  114 . It should be noted that while each of the above-noted antenna groups were identified as having two antennas, more or fewer antennas may be utilized in each antenna group. 
         [0063]    Referring back to  FIG. 1 , a first user equipment  116  is illustrated to be in communication with, for example, the fifth antenna  112  and the sixth antenna  114  to enable the transmission of information to the first user equipment  116  over a first forward link  120 , and the reception of information from the first user equipment  116  over a first reverse link  118 .  FIG. 1  also illustrates a second user equipment  122  that is in communication with, for example, the third antenna  108  and the fourth antenna  110  to enable the transmission of information to the second user equipment  122  over a second forward link  126 , and the reception of information from the second user equipment  122  over a second reverse link  124 . In a Frequency Division Duplex (FDD) system, the communication links  118 ,  120 ,  124   126  that are shown in  FIG. 1  may use different frequencies for communication. For example, the first forward link  120  may use a different frequency than that used by the first reverse link  118 . 
         [0064]    In some embodiments, each group of antennas and/or the area in which they are designed to communicate is often referred to as a sector of the base station. For example, the different antenna groups that are depicted in  FIG. 1  may be designed to communicate to the user equipment in a sector of the base station  100 . In communication over the forward links  120  and  126 , the transmitting antennas of the base station  100  utilize beamforming in order to improve the signal-to-noise ratio of the forward links for the different user equipment  116  and  122 . Also, a base station that uses beamforming to transmit to user equipment scattered randomly throughout its coverage area causes less interference to user equipment in the neighboring cells than a base station that transmits omni-directionally through a single antenna to all its user equipment. 
         [0065]    The communication networks that may accommodate some of the various disclosed embodiments may include logical channels that are classified into Control Channels and Traffic Channels. Logical control channels may include a broadcast control channel (BCCH), which is the downlink channel for broadcasting system control information, a paging control channel (PCCH), which is the downlink channel that transfers paging information, a multicast control channel (MCCH), which is a point-to-multipoint downlink channel used for transmitting multimedia broadcast and multicast service (MBMS) scheduling and control information for one or several multicast traffic channels (MTCHs). Generally, after establishing radio resource control (RRC) connection, MCCH is only used by the user equipments that receive MBMS. Dedicated control channel (DCCH) is another logical control channel that is a point-to-point bi-directional channel transmitting dedicated control information, such as user-specific control information used by the user equipment having an RRC connection. Common control channel (CCCH) is also a logical control channel that may be used for random access information. Logical traffic channels may comprise a dedicated traffic channel (DTCH), which is a point-to-point bi-directional channel dedicated to one user equipment for the transfer of user information. Also, a multicast traffic channel (MTCH) may be used for point-to-multipoint downlink transmission of traffic data. 
         [0066]    The communication networks that accommodate some of the various embodiments may additionally include logical transport channels that are classified into downlink (DL) and uplink (UL). The DL transport channels may include a broadcast channel (BCH), a downlink shared data channel (DL-SDCH), a multicast channel (MCH) and a Paging Channel (PCH). The UL transport channels may include a random access channel (RACH), a request channel (REQCH), an uplink shared data channel (UL-SDCH) and a plurality of physical channels. The physical channels may also include a set of downlink and uplink channels. 
         [0067]    In some disclosed embodiments, the downlink physical channels may include at least one of a common pilot channel (CPICH), a synchronization channel (SCH), a common control channel (CCCH), a shared downlink control channel (SDCCH), a multicast control channel (MCCH), a shared uplink assignment channel (SUACH), an acknowledgement channel (ACKCH), a downlink physical shared data channel (DL-PSDCH), an uplink power control channel (UPCCH), a paging indicator channel (PICH), a load indicator channel (LICH), a physical broadcast channel (PBCH), a physical control format indicator channel (PCFICH), a physical downlink control channel (PDCCH), a physical hybrid ARQ indicator channel (PHICH), a physical downlink shared channel (PDSCH) and a physical multicast channel (PMCH). The uplink physical channels may include at least one of a physical random access channel (PRACH), a channel quality indicator channel (CQICH), an acknowledgement channel (ACKCH), an antenna subset indicator channel (ASICH), a shared request channel (SREQCH), an uplink physical shared data channel (UL-PSDCH), a broadband pilot channel (BPICH), a physical uplink control channel (PUCCH) and a physical uplink shared channel (PUSCH). 
         [0068]    Further, the following terminology and features may be used in describing the various disclosed embodiments:
       3G 3rd Generation   3GPP 3rd Generation Partnership Project   ACLR Adjacent channel leakage ratio   ACPR Adjacent channel power ratio   ACS Adjacent channel selectivity   ADS Advanced Design System   AMC Adaptive modulation and coding   A-MPR Additional maximum power reduction   ARQ Automatic repeat request   BCCH Broadcast control channel   BTS Base transceiver station   CDD Cyclic delay diversity   CCDF Complementary cumulative distribution function   CDMA Code division multiple access   CFI Control format indicator   Co-MIMO Cooperative MIMO   CP Cyclic prefix   CPICH Common pilot channel   CPRI Common public radio interface   CQI Channel quality indicator   CRC Cyclic redundancy check   DCI Downlink control indicator   DFT Discrete Fourier transform   DFT-SOFDM Discrete Fourier transform spread OFDM   DL Downlink (base station to subscriber transmission)   DL-SCH Downlink shared channel   DSP Digital signal processing   DT Development toolset   DVSA Digital vector signal analysis   EDA Electronic design automation   E-DCH Enhanced dedicated channel   E-UTRAN Evolved UMTS terrestrial radio access network   eMBMS Evolved multimedia broadcast multicast service   eNB Evolved Node B   EPC Evolved packet core   EPRE Energy per resource element   ETSI European Telecommunications Standards Institute   E-UTRA Evolved UTRA   E-UTRAN Evolved UTRAN   EVM Error vector magnitude   FDD Frequency division duplex   FFT Fast Fourier transform   FRC Fixed reference channel   FS 1  Frame structure type  1     FS 2  Frame structure type  2     GSM Global system for mobile communication   HARQ Hybrid automatic repeat request   HDL Hardware description language   HI HARQ indicator   HSDPA High speed downlink packet access   HSPA High speed packet access   HSUPA High speed uplink packet access   IFFT Inverse FFT   IOT Interoperability test   IP Internet protocol   LO Local oscillator   LTE Long term evolution   MAC Medium access control   MBMS Multimedia broadcast multicast service   MBSFN Multicast/broadcast over single-frequency network   MCH Multicast channel   MIMO Multiple input multiple output   MISO Multiple input single output   MME Mobility management entity   MOP Maximum output power   MPR Maximum power reduction   MU-MIMO Multiple user MIMO   NAS Non-access stratum   OBSAI Open base station architecture interface   OFDM Orthogonal frequency division multiplexing   OFDMA Orthogonal frequency division multiple access   PAPR Peak-to-average power ratio   PAR Peak-to-average ratio   PBCH Physical broadcast channel   P-CCPCH Primary common control physical channel   PCFICH Physical control format indicator channel   PCH Paging channel   PDCCH Physical downlink control channel   PDCP Packet data convergence protocol   PDSCH Physical downlink shared channel   PHICH Physical hybrid ARQ indicator channel   PHY Physical layer   PRACH Physical random access channel   PMCH Physical multicast channel   PMI Pre-coding matrix indicator   P-SCH Primary synchronization signal   PUCCH Physical uplink control channel   PUSCH Physical uplink shared channel.       
 
         [0157]      FIG. 2  illustrates a block diagram of an exemplary communication system that may accommodate the various embodiments. The MIMO communication system  200  that is depicted in  FIG. 2  comprises a transmitter system  210  (e.g., a base station or access point) and a receiver system  250  (e.g., an access terminal or user equipment) in a MIMO communication system  200 . It will be appreciated by one of ordinary skill that even though the base station is referred to as a transmitter system  210  and a user equipment is referred to as a receiver system  250 , as illustrated, embodiments of these systems are capable of bi-directional communications. In that regard, the terms “transmitter system  210 ” and “receiver system  250 ” should not be used to imply single directional communications from either system. It should also be noted the transmitter system  210  and the receiver system  250  of  FIG. 2  are each capable of communicating with a plurality of other receiver and transmitter systems that are not explicitly depicted in  FIG. 2 . At the transmitter system  210 , traffic data for a number of data streams is provided from a data source  212  to a transmit (TX) data processor  214 . Each data stream may be transmitted over a respective transmitter system. The TX data processor  214  formats, codes and interleaves the traffic data for each data stream, based on a particular coding scheme selected for that data stream, to provide the coded data. 
         [0158]    The coded data for each data stream may be multiplexed with pilot data using, for example, OFDM techniques. The pilot data is typically a known data pattern that is processed in a known manner and may be used at the receiver system to estimate the channel response. The multiplexed pilot and coded data for each data stream is then modulated (symbol mapped) based on a particular modulation scheme (e.g., BPSK, QSPK, M-PSK or M-QAM) selected for that data stream to provide modulation symbols. The data rate, coding and modulation for each data stream may be determined by instructions performed by a processor  230  of the transmitter system  210 . 
         [0159]    In the exemplary block diagram of  FIG. 2 , the modulation symbols for all data streams may be provided to a TX MIMO processor  220 , which can further process the modulation symbols (e.g., for OFDM). The TX MIMO processor  220  then provides N T  modulation symbol streams to N T  transmitter system transceivers (TMTR)  222   a  through  222   t . In one embodiment, the TX MIMO processor  220  may further apply beamforming weights to the symbols of the data streams and to the antenna from which the symbol is being transmitted. 
         [0160]    Each transmitter system transceiver  222   a  through  222   t  receives and processes a respective symbol stream to provide one or more analog signals, and further condition the analog signals to provide a modulated signal suitable for transmission over the MIMO channel. In some embodiments, the conditioning may include, but is not limited to, operations such as amplification, filtering, up-conversion and the like. The modulated signals produced by the transmitter system transceivers  222   a  through  222   t  are then transmitted from the transmitter system antennas  224   a  through  224   t  that are shown in  FIG. 2 . 
         [0161]    At the receiver system  250 , the transmitted modulated signals may be received by the receiver system antennas  252   a  through  252   r , and the received signal from each of the receiver system antennas  252   a  through  252   r  is provided to a respective receiver system transceiver (RCVR)  254   a  through  254   r . Each receiver system transceiver  254   a  through  254   r  conditions a respective received signal, digitizes the conditioned signal to provide samples and may further processes the samples to provide a corresponding “received” symbol stream. In some embodiments, the conditioning may include, but is not limited to, operations such as amplification, filtering, down-conversion and the like. 
         [0162]    An RX data processor  260  then receives and processes the symbol streams from the receiver system transceivers  254   a  through  254   r  based on a particular receiver processing technique to provide a plurality of “detected” symbol streams. In one example, each detected symbol stream can include symbols that are estimates of the symbols transmitted for the corresponding data stream. The RX data processor  260  then, at least in part, demodulates, de-interleaves and decodes each detected symbol stream to recover the traffic data for the corresponding data stream. The processing by the RX data processor  260  may be complementary to that performed by the TX MIMO processor  220  and the TX data processor  214  at the transmitter system  210 . The RX data processor  260  can additionally provide processed symbol streams to a data sink  264 . 
         [0163]    In some embodiments, a channel response estimate is generated by the RX data processor  260  and can be used to perform space/time processing at the receiver system  250 , adjust power levels, change modulation rates or schemes, and/or other appropriate actions. Additionally, the RX data processor  260  can further estimate channel characteristics such as signal-to-noise (SNR) and signal-to-interference ratio (SIR) of the detected symbol streams. The RX data processor  260  can then provide estimated channel characteristics to a processor  270 . In one example, the RX data processor  260  and/or the processor  270  of the receiver system  250  can further derive an estimate of the “operating” SNR for the system. The processor  270  of the receiver system  250  can also provide channel state information (CSI), which may include information regarding the communication link and/or the received data stream. This information, which may contain, for example, the operating SNR and other channel information, may be used by the transmitter system  210  (e.g., base station or eNodeB) to make proper decisions regarding, for example, the user equipment scheduling, MIMO settings, modulation and coding choices and the like. At the receiver system  250 , the CSI that is produced by the processor  270  is processed by a TX data processor  238 , modulated by a modulator  280 , conditioned by the receiver system transceivers  254   a  through  254   r  and transmitted back to the transmitter system  210 . In addition, a data source  236  at the receiver system  250  can provide additional data to be processed by the TX data processor  238 . 
         [0164]    In some embodiments, the processor  270  at the receiver system  250  may also periodically determine which pre-coding matrix to use. The processor  270  formulates a reverse link message comprising a matrix index portion and a rank value portion. The reverse link message may comprise various types of information regarding the communication link and/or the received data stream. The reverse link message is then processed by the TX data processor  238  at the receiver system  250 , which may also receive traffic data for a number of data streams from the data source  236 . The processed information is then modulated by a modulator  280 , conditioned by one or more of the receiver system transceivers  254   a  through  254   r , and transmitted back to the transmitter system  210 . 
         [0165]    In some embodiments of the MIMO communication system  200 , the receiver system  250  is capable of receiving and processing spatially multiplexed signals. In these systems, spatial multiplexing occurs at the transmitter system  210  by multiplexing and transmitting different data streams on the transmitter system antennas  224   a  through  224   t . This is in contrast to the use of transmit diversity schemes, where the same data stream is sent from multiple transmitter systems antennas  224   a  through  224   t . In a MIMO communication system  200  capable of receiving and processing spatially multiplexed signals, a precode matrix is typically used at the transmitter system  210  to ensure the signals transmitted from each of the transmitter system antennas  224   a  through  224   t  are sufficiently decorrelated from each other. This decorrelation ensures that the composite signal arriving at any particular receiver system antenna  252   a  through  252   r  can be received and the individual data streams can be determined in the presence of signals carrying other data streams from other transmitter system antennas  224   a  through  224   t.    
         [0166]    Since the amount of cross-correlation between streams can be influenced by the environment, it is advantageous for the receiver system  250  to feed back information to the transmitter system  210  about the received signals. In these systems, both the transmitter system  210  and the receiver system  250  contain a codebook with a number of precoding matrices. Each of these precoding matrices can, in some instances, be related to an amount of cross-correlation experienced in the received signal. Since it is advantageous to send the index of a particular matrix rather than the values in the matrix, the feedback control signal sent from the receiver system  250  to the transmitter system  210  typically contains the index of a particular precoding matrix. In some instances the feedback control signal also includes a rank index which indicates to the transmitter system  210  how many independent data streams to use in spatial multiplexing. 
         [0167]    Other embodiments of MIMO communication system  200  are configured to utilize transmit diversity schemes instead of the spatially multiplexed scheme described above. In these embodiments, the same data stream is transmitted across the transmitter system antennas  224   a  through  224   t . In these embodiments, the data rate delivered to receiver system  250  is typically lower than spatially multiplexed MIMO communication systems  200 . These embodiments provide robustness and reliability of the communication channel. In transmit diversity systems each of the signals transmitted from the transmitter system antennas  224   a  through  224   t  will experience a different interference environment (e.g., fading, reflection, multi-path phase shifts). In these embodiments, the different signal characteristics received at the receiver system antennas  252   a  through  254   r  are useful in determining the appropriate data stream. In these embodiments, the rank indicator is typically set to 1, telling the transmitter system  210  not to use spatial multiplexing. 
         [0168]    Other embodiments may utilize a combination of spatial multiplexing and transmit diversity. For example in a MIMO communication system  200  utilizing four transmitter system antennas  224   a  through  224   t , a first data stream may be transmitted on two of the transmitter system antennas  224   a  through  224   t  and a second data stream transmitted on remaining two transmitter system antennas  224   a  through  224   t . In these embodiments, the rank index is set to an integer lower than the full rank of the precode matrix, indicating to the transmitter system  210  to employ a combination of spatial multiplexing and transmit diversity. 
         [0169]    At the transmitter system  210 , the modulated signals from the receiver system  250  are received by the transmitter system antennas  224   a  through  224   t , are conditioned by the transmitter system transceivers  222   a  through  222   t , are demodulated by a transmitter system demodulator  240 , and are processed by the RX data processor  242  to extract the reserve link message transmitted by the receiver system  250 . In some embodiments, the processor  230  of the transmitter system  210  then determines which pre-coding matrix to use for future forward link transmissions, and then processes the extracted message. In other embodiments, the processor  230  uses the received signal to adjust the beamforming weights for future forward link transmissions. 
         [0170]    In other embodiments, a reported CSI can be provided to the processor  230  of the transmitter system  210  and used to determine, for example, data rates as well as coding and modulation schemes to be used for one or more data streams. The determined coding and modulation schemes can then be provided to one or more transmitter system transceivers  222   a  through  222   t  at the transmitter system  210  for quantization and/or use in later transmissions to the receiver system  250 . Additionally and/or alternatively, the reported CSI can be used by the processor  230  of the transmitter system  210  to generate various controls for the TX data processor  214  and the TX MIMO processor  220 . In one example, the CSI and/or other information processed by the RX data processor  242  of the transmitter system  210  can be provided to a data sink  244 . 
         [0171]    In some embodiments, the processor  230  at the transmitter system  210  and the processor  270  at the receiver system  250  may direct operations at their respective systems. Additionally, a memory  232  at the transmitter system  210  and a memory  272  at the receiver system  250  can provide storage for program codes and data used by the transmitter system processor  230  and the receiver system processor  270 , respectively. Further, at the receiver system  250 , various processing techniques can be used to process the N R  received signals to detect the N T  transmitted symbol streams. These receiver processing techniques can include spatial and space-time receiver processing techniques, which can include equalization techniques, “successive nulling/equalization and interference cancellation” receiver processing techniques, and/or “successive interference cancellation” or “successive cancellation” receiver processing techniques. 
         [0172]    In LTE Rel-8, the role of the physical downlink layer is primarily to translate data into a reliable signal for transmission across the radio interface between the eNodeB and the User Equipment (UE). Each block of data is first protected against transmission errors with channel coding. In LTE Rel-8, a codeword is an independently coded data block, corresponding to a single transport block (TB) delivered from the Medium Access Control (MAC) layer to the physical layer and protected by a CRC. 
         [0173]    There can be one or two codewords depending on the rank of the transmission, where the rank is equal to the number of spatial layers. A spatial layer is the term used in LTE for the different streams generated by spatial multiplexing, and can be described as a mapping of symbols onto the transmit antenna ports. For ranks greater than 1, two codewords can be transmitted. The number of codewords is always less than or equal to the number of layers, which in turn is always less than or equal to the number of antenna ports. 
         [0174]    After channel coding, the formation of the downlink LTE signal are illustrated in  FIG. 3 . The codewords  301  are scrambled in scrambling stages  302 . Following the scrambling stages  302 , the data bits from each channel are mapped to complex valued modulation symbols in modulation mappers  304 , then mapped to layers in layer mappers  306 . Each layer  307  is precoded in a precoder  308 , where it is identified by a precoding vector of size equal to the number of transmit antenna ports. The data in each layer is then mapped to resource elements (REs) in RE mapper  310 . A resource element is the smallest unit of resource in LTE, and comprises one OFDM subcarrier for a duration of one OFDM symbol. Finally, the REs are translated into a complex-valued OFDM signal by means of an IFFT in OFDM signal generators  312 , and output to antenna ports  313 . 
         [0175]    Scrambling is applied to all downlink physical channels, and serves the purpose of interference rejection. The scrambling sequence in all cases uses an order 31 Gold code, which can provide 2 31  sequences that are not cyclic shifts of each other. Gold codes also possess the attractive feature that they can be generated with very low implementation complexity, as they can be derived from the modulo-2 addition of two maximum-length sequences (known as M-sequences), which can be generated from a simple shift register. An exemplary shift-register implementation of the LTE Rel-8 scrambling sequence generator is illustrated in  FIG. 4 . 
         [0176]    As illustrated in  FIG. 4 , the scrambling sequence generator  400  includes two 31-bit maximal length linear feedback shift registers  401  and  402 , with characteristic polynomials of (x 31 +x 28 +1) and (x 31 +x 30 +x 29 +x 28 +1), respectively, whose outputs are added modulo-2 in adder  403 . 
         [0177]    For LTE Rel-8, PDSCH transmissions, the scrambling sequence generator (e.g., generator  400 ) is initialized at the start of each subframe with a block of coded bits c init  based on the identity of the cell (9 bits), the transmission slot index (5 bits), a codeword index (1 bit) and the UE identifier (16 bits), according to: 
         [0000]        c   init   =n   RNTI ·2 14   +q· 2 13   +└n   s /2┘·2 9   +N   ID   cell   (1)
 
         [0000]    where n RNTI  corresponds to the Radio Network Temporary Identifier (RNTI) associated with the PDSCH transmission, q is the codeword index (0 or 1), n s  is the slot index (0 to 19), and N ID   cell  is the ID of the given cell. This is illustrated in  FIG. 4 . Additionally, after each initialization, a fast forward of 1600 places is applied in order to ensure low cross-correlation between sequences used in adjacent cells. 
         [0178]    A similar process occurs in the case of the physical uplink shared channel (PUSCH) transmissions, where a scrambling sequence generator in the UE is initialized. However, in the case of the uplink, the scrambling initialization code is given by: 
         [0000]        c   init   =n   RNTI ·2 14   +└n   s /2┘·2 9   +N   ID   cell   (2)
 
         [0000]    where n RNTI  and N ID   cell  are as defined above, and n s  is the transmission slot index of the uplink transmission frame. The structure of the initialization code for the uplink differs from the downlink in that there is no codeword index, q, associated with the uplink initialization code. 
         [0179]    While this approach randomizes interference between cells and between UEs, it would also result in additional operations and overhead in the management of coordinated multi-point transmission. Downlink coordinated multi-point (DL-CoMP) transmission makes it possible to have two or more cells serving the same UE concurrently. That is, two or more cells may transmit PDSCH to the same UE at about the same time. In some aspects, the control signaling (PDSCH) is only transmitted from one cell (denoted as the serving cell). It is thus desirable to have identical PDSCH scrambling sequences for all the cells involved in DL-CoMP. This is particularly relevant for dynamic switching between single point and multi point (CoMP) transmissions—UE transparent single-point/multi-point transmission. For transparent operation, the scrambling of reference signals (RS) and data from different cells participating in the joint transmission to a given UE should be the same. However, it will be recognized that the initialization code given in equation (1) is cell-specific, where its current form will result in different PDSCH scrambling sequences for different cells. Note also that a UE specific ID (n RNTI ) is implicated in the aforementioned PDSCH scrambling sequence initialization. 
         [0180]      FIG. 5  illustrates a cluster of cells ( 501 ,  503 ,  505 ) in a wireless network having respective base stations  502 ,  504  and  506 . To maintain communication, for example, with base stations  502  in sector  507  and base station  504  in sector  508  in a DL-CoMP mode, a UE  510  may generate two different scrambling sequences based on two different initialization codes. One scrambling sequence will be generated from an initialization code based on the cell ID of base station  502 , the RNTI of UE  510 , the codeword index for base station  502  and the transmission slot index of base station  502 . The other scrambling sequence will be generated from an initialization code based on the cell ID of base station  504 , the RNTI of the UE  510 , the codeword index for base station  504  and the transmission slot index of base station  504 . Additionally, if the UE  510  is mobile and moves into range of base station  506  in cell  505 , UE  510  may need to generate a third scrambling sequence based on parameters associated with base station  506  during the transition. All of this complexity creates a significant amount of control channel signaling overhead. 
         [0181]    Such additional complexity may be avoided for DL-CoMP in accordance with aspects of the present disclosure. To address the issue of cell-specific scrambling, a method in one embodiment is to provide for all the cells involved in the DL-CoMP operation to use the cell ID of a pre-designated serving cell. That is, 
         [0000]        c   init   =n   RNTI ·2 14   +q· 2 13   +└n   s /2┘·2 9   +N   ID   ServingCell  
 
         [0000]    where N ID   ServingCell  is the ID of the designated serving cell, regardless of whether the given cell is the actual serving cell or not. Another possibility is to assign a virtual ID associated with a cluster of cells such as cells  501 ,  505  and  505 . Such a virtual ID may be semi-statically configured and indicated to the UE. In this case, the initialization code given by: 
         [0000]        c   init   =n   RNTI ·2 14   +q· 2 13   +└n   s /2┘· 9   +N   ID   Virtual  
 
         [0000]    Note that the cluster ID or the virtual ID may or may not be linked to cell IDs serving the UE. 
         [0182]    It may be desirable to omit the UE ID from the initialization code used for the scrambling operation for the sake of reducing complexity in the cells involved in the DL-CoMP operation. In this case, then, the initialization code simplifies to: 
         [0000]        c   init   =q· 2 13   +└n   s /2┘·2 9   +N   ID  
 
         [0000]    where N ID  is a serving cell ID or virtual ID representing the cluster. In this case, the bits in the scrambling sequence generator can be padded with zeros to maintain compatibility with LTE Rel-8 requirements. Alternatively, a virtual UE ID n virtual  can be used, just like the virtual cell ID described above, such that the initialization code is defined as: 
         [0000]        c   init   =n   virtual ·2 14   +q· 2 13   +└n   s /2┘·2 9   +N   ID  
 
         [0183]    It is expected that for cells involved in the CoMP operation, these cells should be aligned at least on the subframe boundaries. However, it is possible that different cells may have different subframe indices. For instance, cell  501  may be aligned on subframes  0 ,  1 ,  2 ,  3 , etc., while cell  503  is aligned on subframes  1 ,  2 ,  3 ,  4 , etc. That is, the two cells are subframe boundary aligned but not necessarily subframe index aligned (i.e., not completely synchronized, or non-radio-frame aligned). In this case, the n s  value used in the above scrambling should be the same for all the cells involved and could be based on the subframe index of the serving cell, or based on a virtual subframe/slot indices, where all cells involved exchange and share common values. 
         [0184]    Similarly, the transmission slot index may be replaced with the slot index of the serving cell or a virtual slot index assigned to the cluster, for example. The same approach may be applied to the codeword index, assigning the serving cell&#39;s codeword index or a virtual codeword. It should be noted that these changes to the parameters for the scrambling sequence initialization code will not affect the normal operation of other UEs in the cluster. It should also be noted that using virtual parameters in the initialization code will not affect the randomness of the CoMP scrambling sequence with respect to other UEs in the CoMP cells. 
         [0185]    As noted above, the initialization code used in the UE for the physical uplink shared channel (PUSCH) has the same structure as the initialization code for the PDCCH except for the absence of a codeword index (which is not relevant to the uplink). Accordingly, all of the configurations discussed for the downlink scrambling initialization code may be applied to the uplink, with the exception of the codeword options. That is, in accordance with the present disclosure, the uplink scrambling initialization code may use a serving cell identifier or a virtual serving cell identifier, a UE identifier or a virtual UE identifier, a UE transmission slot index or a virtual UE transmission slot index. Similarly, the uplink scrambling initialization code may omit the UE identifier. 
         [0186]    A similar approach may be used to generate the scrambling sequence for scrambling the UE reference signals (UE-RS) for all the cells involved in the CoMP transmission 
         [0187]    One approach for initializing the UE-RS sequence is given by 
         [0000]        c   init =(└ n   s /2┘+1)·(2 N   ID   cell +1)·2 16  
 
         [0000]    where all the parameters are defined above. In order to generate the same UE-RS random sequence for all the cells involved, the same design principle discussed above is applicable as well, in particular, c init  may be defined as: 
         [0000]        c   init =(└ n   s /2┘+1)·(2 N   ID +1)·2 16  
 
         [0000]    where N ID  is a designated serving cell ID or a virtual cell ID. 
         [0188]    Communicating these common initialization parameter values, virtual or otherwise, between CoMP cells, may be accomplished through a backhaul controller such as system controller  520  in  FIG. 5 , and descried in greater detail below. 
         [0189]    With respect to the uplink, the UE may receive the relevant parameters (i.e., serving cell identifier and UE identifier) and may then transmit the uplink initialization code parameters (serving cell identifier, UE identifier and UE transmission slot index) to other cells participating in the UL-CoMP (i.e., point-to-multipoint) transmission network via the physical uplink control channel (PUCCH) to enable scrambled transmissions on the physical uplink shared channel (PUSCH). 
         [0190]      FIG. 8  illustrates a system  800  according to one exemplary embodiment. In  FIG. 8 , a base station  810  is designated as a CoMP serving cell, base station  820  is a CoMP cell in a CoMP transmission network, and user equipment (UE)  830  is the UE to be configured for DL-CoMP. System  800  employs an initialization code generator  801  and a scrambling sequence generator  802  in each of the base stations and UE&#39;s involved in the DL-CoMP transmissions. Base station  810  communicates with UE  830  via downlink  803 , which supports physical downlink control channel PDCCH  804  and physical downlink shared channel  805 . Base station  820  communicates with UE  830  via downlink  806 , which supports PDCCH  807  and PDSCH  809 . In turn, UE  830  communicates with base station  820  via uplink  810 , which supports physical uplink control channel (PUCCH)  811  and physical uplink shared channel (PUSCH)  812 . Communication between base station  810  and base station  820  is managed by system controller  840 . While  FIG. 8  illustrates only two base stations and one UE, it will be appreciated that provided embodiments are not so limited, and may include more than two base stations and more than one UE. 
         [0191]    In general, system  800  generates a shared initialization code for scrambling sequence generation in each base station and UE (jointly, the CoMP participants) involved in a CoMP transmission network, and each CoMP participant includes a scrambling sequence generator  802 , which may be implemented in hardware, software, firmware or some combination thereof, such as is known in the art, and an initialization code generator,  801 , which may be implemented in hardware, software, firmware or some combination thereof, such as is known in the art. 
         [0192]    In general, the system  800  generates identical, shared scrambling initialization codes for PDSCHs between CoMP base stations and UEs, such that identical (i.e., common) sequences are generated by all cells involved in a downlink (DL) coordinated multi-point transmissions/receptions (CoMP) operation in order to optimize switchover operations between single-point and multi-point CoMP transmissions. Similarly, system  800  generates identical, shared scrambling initialization codes for PUSCH transmissions between a UE configured for CoMP operation and CoMP base stations, such that the scrambling sequences used for scrambling data transmissions on the PUSCH are the same as the scrambling sequences used in the CoMP base stations to descramble the data transmissions on the PUSCH. 
         [0193]    In one aspect, all cells involved in DL-CoMP can employ the same serving cell identifier (ID) whether a given cell is the serving cell or not. The cell ID can be passed between cells as a parameter where each of the cells then employs the same cell ID during initialization. In another aspect, a virtual ID is generated and employed by each of the cells involved in the DL-CoMP operation or communication. Again, by requiring all cells in addition to the serving cell to utilize the same cell ID, switchover between single-point and multi-point CoMP transmissions can be facilitated. 
         [0194]    In the system  800  of  FIG. 8 , base station  810  (CoMP serving cell) is configured to generate a shared initialization code with initialization code generator  801  based on a real or virtual cell identifier, a real or virtual codeword index, a real or virtual transmission slot index, and optionally, a real or virtual identifier of UE  830 . Base station  810  is configured to transmit the shared initialization code to UE  830  on downlink  803  using PDCCH  804 . 
         [0195]    Base station  810  is also configured to send the shared initialization code parameters to base station  820  (CoMP cell) via system controller  840 . Base station  820  is configured to generate the shared initialization code locally, to initialize a local scrambling sequence generator  802 , and to scramble data to be sent to UE  830  on downlink  806  via PDCCH  807 . 
         [0196]    UE  830  is configured to receive the shared initialization code or code parameters on PDCCH  804 , and generate the shared initialization code locally in generator  801 , to initialize its local sequence generator  802 , and to generate a descrambling sequence based on the initialization code. UE  830  is further configured receive scrambled data from base station  810  on PDSCH  803  and from base station  820  on PDSCH  809 , and to descramble the scrambled data using the descrambling code. 
         [0197]    In other embodiment, base station  810  does not send the initialization code to base station  820 . Instead, after receiving the initialization code from base station  810  on PDCCH  804 , the UE  830  transmits the initialization code to base station  820  on uplink  810  via physical uplink control channel  811 . After receiving the initialization code from UE  830 , base station  820  processes the code, scrambles data and transmits date to UE  830  as described above. 
         [0198]    In another embodiment, UE  830  receives, from base station  810 , a serving cell identifier or virtual serving cell identifier, and a UE identifier or virtual UE identifier. UE  830  may then generate an UL-CoMP initialization code for PUSCH CoMP transmissions, using the serving cell identifier (actual or virtual), the UE identifier (actual or virtual) and a PUSCH transmission slot index associated with the UE (actual or virtual), and transmit the initialization code, or the parameters thereof, to base station  820  on PUCCH  811  (and to base station  810  on another PUCCH, not shown). UE  830  may then transmit scrambled UL-CoMP data to base stations  810  and  820  on the respective PUSCHs and base stations  810  and  820  may descramble the scrambled PUSCH data using descrambling sequences generated from the UL-CoMP scrambling initialization code received from UE  830 . 
         [0199]      FIG. 6  is a flowchart illustrating a method  600  according to one provided embodiment. For purposes of simplicity of explanation, the method is shown and described as a series of operations. It is to be understood that the method is not limited by the order of operations, as some operations can, in accordance with one or more embodiments, occur in different orders and/or concurrently with other operations from that shown and described herein. For example, those skilled in the art will understand and appreciate that a method could alternatively be represented as a series of interrelated states or events, such as in a state diagram. Moreover, not all illustrated operations may be required to implement a method in accordance with one or more of the disclosed embodiment. 
         [0200]    In  FIG. 6 , and with reference to exemplary system  800 , the method begins at operation  602 , where a shared initialization code is generated in a serving cell  810  of a CoMP transmission network, where the shared initialization code includes at least a virtual serving cell ID and a virtual UE identifier. In operation  604 , the shared initialization code sent to another cell  820  of the CoMP transmission network. The other cell  820  may be coupled to the serving cell  810  through a system controller  840 . In operation  606 , the shared initialization code is transmitted from the serving cell  810  to a UE  830  on a physical downlink control channel (PDCCH)  804 . The scrambling sequence generator  802  in the serving cell  810  is initialized with the initialization code in operation  608 . A scrambling sequence is generated by sequence generator  802  in the serving cell  810  in operation  610 , and scrambled data is generated with the scrambling sequence in operation  612 . As described above the initialization code may include the serving cell ID or a virtual serving cell ID, a UE ID, virtual UE ID or no UE ID, a codeword index or a virtual codeword index, and a transmission slot index or a virtual transmission slot index. 
         [0201]      FIG. 7A  is flowchart illustrating a method  700  according to one provided embodiment. In  FIG. 7A , and with reference to exemplary system  800 , the method  700  begins at operation  702 , where a UE  830  receives a shared initialization code from a CoMP serving cell  810 , where the shared initialization code is configured to generate a common scrambling sequence for a coordinated multi-point (CoMP) transmission network. At operation  704 , the UE  830  transmits the shared initialization code to another cell  820  in the CoMP transmission network, where the other cell in the CoMP transmission network scrambles data with a scrambling sequence generated with the shared initialization code, and transmits the scrambled data to the UE. In operation  706 , the UE  830  receives scrambled data from at least one of the CoMP serving cell  810  on a first PDSCH  805  and from another cell  820  in the CoMP transmission network on a second PDSCH  809 . 
         [0202]      FIG. 7B  is a flowchart illustrating a method  750  according to one provided embodiment. In  FIG. 7B , and with reference to exemplary system  800 , the method  750  begins at operation  752 , where a UE  830  receives components of a shared initialization code from a CoMP serving cell  810 , where the components of the shared initialization code are configured to generate an uplink scrambling sequence for a CoMP transmission network. At operation  754 , the UE  830  generates the shared initialization code to initialize a scrambling sequence generator for a physical uplink shared channel (PUSCH). In operation  756 , the UE  830  transmits the shared initialization code to a cell (e.g.,  810  or  820 ) in the CoMP transmission network on a physical uplink control channel (PUCCH), where the cell in the CoMP transmission network is configured to descramble data on a PUSCH from the UE with a scrambling sequence generated from the shared initialization code. In operation  758 , the UE transmits scrambled data to the cell(s) in the CoMP transmission network on a PUSCH. 
         [0203]      FIG. 9  illustrates an apparatus  900  within which various disclosed embodiments may be implemented. In particular, the apparatus  900  that is shown in  FIG. 9  may comprise at least a portion of an access point (such as base stations  810  and  820  depicted in  FIG. 8 ), at least a portion of a user equipment (such as the user equipment  830  depicted in  FIG. 8 ), at least a portion of a system controller (such as system controller  840  depicted in  FIG. 8 ) and/or at least a portion of a transmitter system or a receiver system (such as the transmitter system  210  and the receiver system  250  that are depicted in  FIG. 2 ). The apparatus  900  that is depicted in  FIG. 9  can be resident within a wireless network and receive incoming data via, for example, one or more receivers and/or the appropriate reception and decoding circuitry (e.g., antennas, transceivers, demodulators and the like). The apparatus  900  that is depicted in  FIG. 9  can also transmit outgoing data via, for example, one or more transmitters and/or the appropriate encoding and transmission circuitry (e.g., antennas, transceivers, modulators and the like). Additionally, or alternatively, the apparatus  900  that is depicted in  FIG. 9  may be resident within a wired network. 
         [0204]      FIG. 9  further illustrates that the apparatus  900  can include a memory  902  that can retain instructions for performing one or more operations, such as signal conditioning, analysis and the like. Additionally, the apparatus  900  of  FIG. 9  may include a processor  904  that can execute instructions that are stored in the memory  902  and/or instructions that are received from another device. The instructions can relate to, for example, configuring or operating the apparatus  900  or a related communications apparatus. It should be noted that while the memory  902  that is depicted in  FIG. 9  is shown as a single block, it may comprise two or more separate memories that constitute separate physical and/or logical units. In addition, the memory while being communicatively connected to the processor  904 , may reside fully or partially outside of the apparatus  900  that is depicted in  FIG. 9 . It is also to be understood that one or more components or modules, such as the initialization code generators  801  and the sequence generators  802  that are shown in  FIG. 8 , can exist within a memory such as memory  902 . 
         [0205]    It will be appreciated that the memories that are described in connection with the disclosed embodiments can be either volatile memory or nonvolatile memory, or can include both volatile and nonvolatile memory. By way of illustration, and not limitation, nonvolatile memory can include read only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable ROM (EEPROM) or flash memory. Volatile memory can include random access memory (RAM), which acts as external cache memory. By way of illustration and not limitation, RAM is available in many forms such as synchronous RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), enhanced SDRAM (ESDRAM), Synchlink DRAM (SLDRAM) and direct Rambus RAM (DRRAM). 
         [0206]    It should also be noted that the apparatus  900  of  FIG. 9  can be employed with a user equipment or mobile device, and can be, for instance, a module such as an SD card, a network card, a wireless network card, a computer (including laptops, desktops, personal digital assistants PDAs), mobile phones, smart phones or any other suitable terminal that can be utilized to access a network. The user equipment accesses the network by way of an access component (not shown). In one example, a connection between the user equipment and the access components may be wireless in nature, in which access components may be the base station and the user equipment is a wireless terminal. For instance, the terminal and base stations may communicate by way of any suitable wireless protocol, including but not limited to Time Divisional Multiple Access (TDMA), Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiplexing (OFDM), FLASH OFDM, Orthogonal Frequency Division Multiple Access (OFDMA) or any other suitable protocol. 
         [0207]    Access components can be an access node associated with a wired network or a wireless network. To that end, access components can be, for instance, a router, a switch and the like. The access component can include one or more interfaces, e.g., communication modules, for communicating with other network nodes. Additionally, the access component can be a base station (or wireless access point) in a cellular type network, wherein base stations (or wireless access points) are utilized to provide wireless coverage areas to a plurality of subscribers. Such base stations (or wireless access points) can be arranged to provide contiguous areas of coverage to one or more cellular phones and/or other wireless terminals. 
         [0208]    It is to be understood that the embodiments and features that are described herein may be implemented by hardware, software, firmware or any combination thereof. Various embodiments described herein are described in the general context of methods or processes, which may be implemented in one embodiment by a computer program product, embodied in a computer-readable medium, including computer-executable instructions, such as program code, executed by computers in networked environments. As noted above, a memory and/or a computer-readable medium may include removable and non-removable storage devices including, but not limited to, Read Only Memory (ROM), Random Access Memory (RAM), compact discs (CDs), digital versatile discs (DVD) and the like. When implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A storage media may be any available media that can be accessed by a general purpose or special purpose computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code means in the form of instructions or data structures and that can be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. 
         [0209]    Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), then the coaxial cable, fiber optic cable, twisted pair, or DSL are included in the definition of medium. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media. 
         [0210]    Generally, program modules may include routines, programs, objects, components, data structures, etc., that perform particular tasks or implement particular abstract data types. Computer-executable instructions, associated data structures and program modules represent examples of program code for executing the methods disclosed herein. The particular sequence of such executable instructions or associated data structures represents examples of corresponding acts for implementing the functions described in such steps or processes. 
         [0211]    The various illustrative logics, logical blocks, modules, and circuits described in connection with the aspects disclosed herein may be implemented or performed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but, in the alternative, the processor may be any conventional processor, controller, microcontroller or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. Additionally, at least one processor may comprise one or more modules operable to perform one or more of the steps and/or actions described above. 
         [0212]    For a software implementation, the techniques described herein may be implemented with modules (e.g., procedures, functions and so on) that perform the functions described herein. The software codes may be stored in memory units and executed by processors. The memory unit may be implemented within the processor and/or external to the processor, in which case it can be communicatively coupled to the processor through various means as is known in the art. Further, at least one processor may include one or more modules operable to perform the functions described herein. 
         [0213]    The techniques described herein may be used for various wireless communication systems such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA and other systems. The terms “system” and “network” are often used interchangeably. A CDMA system may implement a radio technology such as Universal Terrestrial Radio Access (UTRA), cdma2000, etc. UTRA includes Wideband-CDMA (W-CDMA) and other variants of CDMA. Further, cdma2000 covers IS-2000, IS-95 and IS-856 standards. A TDMA system may implement a radio technology such as Global System for Mobile Communications (GSM). An OFDMA system may implement a radio technology such as Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDM®, etc. UTRA and E-UTRA are part of Universal Mobile Telecommunication System (UMTS). 3GPP Long Term Evolution (LTE) is a release of UMTS that uses E-UTRA, which employs OFDMA on the downlink and SC-FDMA on the uplink. UTRA, E-UTRA, UMTS, LTE and GSM are described in documents from an organization named “3rd Generation Partnership Project” (3GPP). Additionally, cdma2000 and UMB are described in documents from an organization named “3rd Generation Partnership Project 2” (3GPP2). Further, such wireless communication systems may additionally include peer-to-peer (e.g., user equipment-to-user equipment) ad hoc network systems often using unpaired unlicensed spectrums, 802.xx wireless LAN, BLUETOOTH and any other short- or long-range, wireless communication techniques. 
         [0214]    Single carrier frequency division multiple access (SC-FDMA), which utilizes single carrier modulation and frequency domain equalization is a technique that can be utilized with the disclosed embodiments. SC-FDMA has similar performance and essentially a similar overall complexity as those of OFDMA systems. SC-FDMA signal has lower peak-to-average power ratio (PAPR) because of its inherent single carrier structure. SC-FDMA can be utilized in uplink communications where lower PAPR can benefit a user equipment in terms of transmit power efficiency. 
         [0215]    Moreover, various aspects or features described herein may be implemented as a method, apparatus or article of manufacture using standard programming and/or engineering techniques. The term “article of manufacture” as used herein is intended to encompass a computer program accessible from any computer-readable device, carrier or media. For example, computer-readable media can include but are not limited to magnetic storage devices (e.g., hard disk, floppy disk, magnetic strips, etc.), optical disks (e.g., compact disk (CD), digital versatile disk (DVD), etc.), smart cards, and flash memory devices (e.g., EPROM, card, stick, key drive, etc.). Additionally, various storage media described herein can represent one or more devices and/or other machine-readable media for storing information. The term “machine-readable medium” can include, without being limited to, wireless channels and various other media capable of storing, containing, and/or carrying instruction(s) and/or data. Additionally, a computer program product may include a computer readable medium having one or more instructions or codes operable to cause a computer to perform the functions described herein. 
         [0216]    Further, the steps and/or actions of a method or algorithm described in connection with the aspects disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, a hard disk, a removable disk, a CD-ROM or any other form of storage medium known in the art. An exemplary storage medium may be coupled to the processor, such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. Further, in some embodiments, the processor and the storage medium may reside in an ASIC. Additionally, the ASIC may reside in a user equipment (e.g. UE  830  in  FIG. 8 ). In the alternative, the processor and the storage medium may reside as discrete components in a base station (e.g., base station  810  in  FIG. 8 ). Additionally, in some embodiments, the steps and/or actions of a method or algorithm may reside as one or any combination or set of codes and/or instructions on a machine readable medium and/or computer readable medium, which may be incorporated into a computer program product. 
         [0217]    While the foregoing disclosure discusses illustrative embodiments, it should be noted that various changes and modifications could be made herein without departing from the scope of the described embodiments as defined by the appended claims. Accordingly, the described embodiments are intended to embrace all such alterations, modifications and variations that fall within scope of the appended claims. Furthermore, although elements of the described embodiments may be described or claimed in the singular, the plural is contemplated unless limitation to the singular is explicitly stated. Additionally, all or a portion of any embodiment may be utilized with all or a portion of any other embodiments, unless stated otherwise. 
         [0218]    To the extent that the term “includes” is used in either the detailed description or the claims, such term is intended to be inclusive in a manner similar to the term “comprising” as “comprising” is interpreted when employed as a transitional word in a claim. Furthermore, the term “or” as used in either the detailed description or the claims is intended to mean an inclusive “or” rather than an exclusive “or.” That is, unless specified otherwise, or clear from the context, the phrase “X employs A or B” is intended to mean any of the natural inclusive permutations. That is, the phrase “X employs A or B” is satisfied by any of the following instances: X employs A; X employs B; or X employs both A and B. In addition, the articles “a” and “an” as used in this application and the appended claims should generally be construed to mean “one or more” unless specified otherwise or clear from the context to be directed to a singular form.