Patent Publication Number: US-RE47463-E

Title: System and method for dynamic cell selection and resource mapping for CoMP joint transmission

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) AND CLAIM OF PRIORITY 
     The present application is related to an application for reissue of U.S. Pat. No. 8,274,951 issued Sep. 25, 2012 on U.S. Non-Provisional patent application Ser. No. 12/716,144 filed Mar. 2, 2010, and claims the priority to and the benefit under 35 U.S.C. § 119(e) of the filing date of U.S. Provisional Patent Application No. 61/210,291, filed Mar. 17, 2009, entitled “DYNAMIC CELL SELECTION FOR CoMP REPORTING SET AND TRANSPARENT RESOURCE MAPPING FOR CoMP JP”. Provisional Patent Application No. 61/210,291 is assigned to the assignee of the present application and The content of the above-identified patent documents is hereby incorporated by reference into the present application as if fully set forth herein. The present application hereby claims priority under 35 U.S.C.§119(e) to U.S. Provisional Patent Application No. 61/210,291. 
     TECHNICAL FIELD OF THE INVENTION 
     The present application relates generally to wireless communications and, more specifically, to dynamic cell selection and resource mapping in wireless communications networks. 
     BACKGROUND OF THE INVENTION 
     In a wireless communications network, multiple cells or base stations (also referred to as “eNBs”) use frequency bands and standardized codebooks for precoding transmission to their respective user equipments (UEs), using multiple transmit antennas. A typical problem of this procedure occurs where several cells or base stations are serving their intended UEs while interfering with each other&#39;s signal. This scenario is called “inter-cell interference.” Inter-cell interference constrains the throughput of the wireless network. 
     SUMMARY OF THE INVENTION 
     A base station capable of communicating with a plurality of subscriber stations is provided. The base station includes a plurality of antenna configured to transmit data and control information and a transmitter coupled to the plurality of antenna. The transmitter is configured to transmit a plurality of symbols in a sub-frame to a subscriber station. The base station also includes a controller configured to include a bitmap in a downlink control information (DCI). The bitmap is configured to inform the subscriber station regarding a subset of cells within a CoMP measurement set for channel quality information reporting. 
     A subscriber station capable of communicating with a plurality of base stations is provided. The subscriber station includes a plurality of antenna configured to receive data and control information and a receiver coupled to the plurality of antenna. The receiver is configured to receive a plurality of symbols in a sub-frame from a base station. The subscriber station also includes a controller configured to interpret a bitmap in a downlink control information (DCI). The bitmap is configured to identify a subset of cells within a CoMP measurement set for channel quality information reporting. 
     A method for communicating with a plurality of subscriber stations is provided. The method includes transmitting, to a subscriber station, a plurality of symbols in a sub-frame and including a bitmap in a downlink control information (DCI). The bitmap is configured to inform the subscriber station regarding a subset of cells within a CoMP measurement set for channel quality information reporting. 
     A base station capable of communicating with a plurality of subscriber stations is provided. The base station includes a plurality of antenna configured to transmit data and control information. The base station also includes a transmitter coupled to the plurality of antenna. The transmitter is configured to transmit a first resource block to a subscriber station. The base station further includes a controller configured to coordinate transmission of the first resource block with a transmission of at least one additional resource block that is transmitted from at least one additional base station to the subscriber station. The transmissions of the first and at least one additional resource blocks are coordinated such that the subscriber station receives single resource block that comprises at least one of the first and the at least one additional resource block. The first and at least one additional resource blocks include at least one reference signal (RS) pattern. The controller is configured to puncture a plurality of resource elements in the first resource block that might overlap with one of the RS patterns in one or more of the additional resource block(s) such that no data is transmitted in the plurality of punctured resource elements. 
     A subscriber station capable of communicating with a plurality of base stations is provided. The subscriber station includes a plurality of antenna configured to receive data and control information and a receiver coupled to the plurality of antenna. The receiver is configured to receive a single resource block. The single resource block includes at least one of: a first resource block received from a first base station; and at least one additional resource block received from at least one additional base station. The first and at least one additional resource blocks include at least one reference signal (RS) pattern. The receiver is configured to not expect data in a plurality of punctured resource elements in the first resource block that might overlap with one of the at least one RS pattern in one or more of the at least one additional resource block. 
     A method for communicating with a plurality of subscriber stations is provided. The method includes transmitting a first resource block to a subscriber station and coordinating the transmission of the first resource block with a transmission of at least one additional resource block from at least one additional base station to the subscriber station such that the subscriber station receives single resource block that includes at least one of the first and the at least one additional resource block. The first and at least one additional resource blocks comprise at least one reference signal (RS) patterns. The method also includes puncturing a plurality of resource elements in the first resource block that might overlap with one of the at least one RS patterns in the at least one additional resource block such that no data is transmitted in the plurality of resource elements in the first resource block that might overlap with one of the at least one RS patterns in the at least one additional resource block. 
     Before undertaking the DETAILED DESCRIPTION OF THE INVENTION below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document: the terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation; the term “or,” is inclusive, meaning and/or; the phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like; and the term “controller” means any device, system or part thereof that controls at least one operation, such a device may be implemented in hardware, firmware or software, or some combination of at least two of the same. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined words and phrases. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which like reference numerals represent like parts: 
         FIG. 1A  illustrates exemplary wireless network  100  that is capable of decoding data streams according to an exemplary embodiment of the disclosure; 
         FIG. 1B  illustrates a joint transmission in a wireless network according embodiments of the present disclosure; 
         FIG. 1C  illustrates CMCS, CRCS and Active CoMP Sets according to embodiments of the present disclosure; 
         FIG. 2  illustrates exemplary base station in greater detail according to embodiments of the present disclosure; 
         FIG. 3  illustrates an exemplary wireless mobile station according to embodiments of the present disclosure; 
         FIGS. 4 and 6  illustrate an uplink scheduling grant for CoMP transmissions according to embodiments of the present disclosure; 
         FIG. 5  illustrates a process for network configuration of CoMP sets according to embodiments of the present disclosure; 
         FIGS. 7 through 11  illustrate CoMP PDSCH resource mapping according to embodiments of the present disclosure; 
         FIGS. 12 and 14  illustrate frequency shifts for CRS according to embodiments of the present disclosure; and 
         FIGS. 13 and 15  illustrate a resource element mapping of CoMP PDSCH based on overlapping patterns according to embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIGS. 1 through 15 , discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged wireless communication system. 
     With regard to the following description, it is noted that the LTE term “node B” is another term for “base station” used below. Further, the term “cell” is a logic concept that can represent a “base station” or a “sector” belongs to a “base station”. In the present disclosure, “cell” and “base station” are used interchangeably to indicate the actual transmission units (may be “sector” or “base station” and the like) in the wireless system. Also, the LTE term “user equipment” or “UE” is another term for “subscriber station” used below. 
     With regard to the following description, it is noted that the discussion is focused on reference signals (RS) including common reference signals (CRS), channel state information reference signals (CSI-RS), and the like. The collision between CRS and PDSCH discussed in the document is for illustration purpose, however, the collision between reference signal resource elements and PDSCH resource elements will occur for any type of reference signals. 
       FIG. 1A  illustrates exemplary wireless network  100  that is capable of decoding data streams according to one embodiment of the present disclosure. In the illustrated embodiment, wireless network  100  includes base station (BS)  101 , base station (BS)  102 , and base station (BS)  103 . Base station  101  communicates with base station  102  and base station  103 . Base station  101  also communicates with Internet protocol (IP) network  130 , such as the Internet, a proprietary IP network, or other data network. 
     Base station  102  provides wireless broadband access to network  130 , via base station  101 , to a first plurality of subscriber stations within coverage area  120  of base station  102 . The first plurality of subscriber stations includes subscriber station (SS)  111 , subscriber station (SS)  112 , subscriber station (SS)  113 , subscriber station (SS)  114 , subscriber station (SS)  115  and subscriber station (SS)  116 . Subscriber station (SS) may be any wireless communication device, such as, but not limited to, a mobile phone, mobile PDA and any mobile station (MS). In an exemplary embodiment, SS  111  may be located in a small business (SB), SS  112  may be located in an enterprise (E), SS  113  may be located in a WiFi hotspot (HS), SS  114  may be located in a residence, SS  115  may be a mobile (M) device, and SS  116  may be a mobile (M) device. 
     Base station  103  provides wireless broadband access to network  130 , via base station  101 , to a second plurality of subscriber stations within coverage area  125  of base station  103 . The second plurality of subscriber stations includes subscriber station  115  and subscriber station  116 . In alternate embodiments, base stations  102  and  103  may be connected directly to the Internet or other controller unit by means of a wired broadband connection, such as an optical fiber, DSL, cable or T1/E1 line, rather than indirectly through base station  101 . 
     In other embodiments, base station  101  may be in communication with either fewer or more base stations. Furthermore, while only six subscriber stations are shown in  FIG. 1A , it is understood that wireless network  100  may provide wireless broadband access to more than six subscriber stations. It is noted that subscriber station  115  and subscriber station  116  are on the edge of both coverage area  120  and coverage area  125 . Subscriber station  115  and subscriber station  116  each communicate with both base station  102  and base station  103  and may be said to be cell-edge devices interfering with each other. For example, the communications between BS  102  and SS  116  may be interfering with the communications between BS  103  and SS  115 . Additionally, the communications between BS  103  and SS  115  may be interfering with the communications between BS  102  and SS  116 . 
     In an exemplary embodiment, base stations  101 - 103  may communicate with each other and with subscriber stations  111 - 116  using an IEEE-802.16 wireless metropolitan area network standard, such as, for example, an IEEE-802.16e standard. In another embodiment, however, a different wireless protocol may be employed, such as, for example, a HIPERMAN wireless metropolitan area network standard. Base station  101  may communicate through direct line-of-sight or non-line-of-sight with base station  102  and base station  103 , depending on the technology used for the wireless backhaul. Base station  102  and base station  103  may each communicate through non-line-of-sight with subscriber stations  111 - 116  using OFDM and/or OFDMA techniques. 
     Base station  102  may provide a T1 level service to subscriber station  112  associated with the enterprise and a fractional T1 level service to subscriber station  111  associated with the small business. Base station  102  may provide wireless backhaul for subscriber station  113  associated with the WiFi hotspot, which may be located in an airport, café, hotel, or college campus. Base station  102  may provide digital subscriber line (DSL) level service to subscriber stations  114 ,  115  and  116 . 
     Subscriber stations  111 - 116  may use the broadband access to network  130  to access voice, data, video, video teleconferencing, and/or other broadband services. In an exemplary embodiment, one or more of subscriber stations  111 - 116  may be associated with an access point (AP) of a WiFi WLAN. Subscriber station  116  may be any of a number of mobile devices, including a wireless-enabled laptop computer, personal data assistant, notebook, handheld device, or other wireless-enabled device. Subscriber station  114  may be, for example, a wireless-enabled personal computer, a laptop computer, a gateway, or another device. 
     Dotted lines show the approximate extents of coverage areas  120  and  125 , which are shown as approximately circular for the purposes of illustration and explanation only. It should be clearly understood that the coverage areas associated with base stations, for example, coverage areas  120  and  125 , may have other shapes, including irregular shapes, depending upon the configuration of the base stations and variations in the radio environment associated with natural and man-made obstructions. 
     Also, the coverage areas associated with base stations are not constant over time and may be dynamic (expanding or contracting or changing shape) based on changing transmission power levels of the base station and/or the subscriber stations, weather conditions, and other factors. In an embodiment, the radius of the coverage areas of the base stations, for example, coverage areas  120  and  125  of base stations  102  and  103 , may extend in the range from less than 2 kilometers to about fifty kilometers from the base stations. 
     As is well known in the art, a base station, such as base station  101 ,  102 , or  103 , may employ directional antennas to support a plurality of sectors within the coverage area. In  FIG. 1 , base stations  102  and  103  are depicted approximately in the center of coverage areas  120  and  125 , respectively. In other embodiments, the use of directional antennas may locate the base station near the edge of the coverage area, for example, at the point of a cone-shaped or pear-shaped coverage area. 
     The connection to network  130  from base station  101  may comprise a broadband connection, for example, a fiber optic line, to servers located in a central office or another operating company point-of-presence. The servers may provide communication to an Internet gateway for internet protocol-based communications and to a public switched telephone network gateway for voice-based communications. In the case of voice-based communications in the form of voice-over-IP (VoIP), the traffic may be forwarded directly to the Internet gateway instead of the PSTN gateway. The servers, Internet gateway, and public switched telephone network gateway are not shown in  FIG. 1A . In another embodiment, the connection to network  130  may be provided by different network nodes and equipment. 
     In accordance with an embodiment of the present disclosure, one or more of base stations  101 - 103  and/or one or more of subscriber stations  111 - 116  comprises a receiver that is operable to decode a plurality of data streams received as a combined data stream from a plurality of transmit antennas using an MMSE-SIC algorithm. As described in more detail below, the receiver is operable to determine a decoding order for the data streams based on a decoding prediction metric for each data stream that is calculated based on a strength-related characteristic of the data stream. Thus, in general, the receiver is able to decode the strongest data stream first, followed by the next strongest data stream, and so on. As a result, the decoding performance of the receiver is improved as compared to a receiver that decodes streams in a random or pre-determined order without being as complex as a receiver that searches all possible decoding orders to find the optimum order. 
       FIG. 1B  illustrates a joint transmission in a wireless network  100  according embodiments of the present disclosure. Base station (BS)  102  (e.g., “Cell 1”) and BS  103  (e.g., “Cell 2”) are performing a coordinated multipoint (CoMP) transmission to the subscriber station (SS)  116 , that is, communications to and from SS  116  are conducted through BS  102  and BS  103 . H i1  corresponds to the wireless channel from “Cell i” to SS  116 . Accordingly, H 11    135  corresponds to the wireless channel from BS  102  to SS  116 ; and H 21    140  corresponds to the wireless channel from BS  103  to SS  116 . When in the joint processing mode, BS  102  and BS  103  jointly process SS  116 &#39;s information together. BS  102  and BS  103  send SS  116 &#39;s information over the air to SS  116  substantially simultaneously through the wireless channels. By doing this, the interference is greatly reduced while the received power (sum from the two cells BS  102  and BS  103 ) is greatly improved. Illustration of two cells, BS  102  and BS  103  is for example purposes only and other embodiments including more than two cells could be used without departing from the scope of this disclosure. 
     CoMP transmission can be classified into two categories: coordinated scheduling and/or beam-forming, and CoMP joint transmission. In coordinated scheduling and/or beam-forming, data to SS  116  is transmitted from BS  102  while the scheduling decisions are coordinated to control the interference generated in a set of coordinated cells. In other words, the data intended for SS  116  is not shared while some information related to the channels and the controls are shared among different cells. The signals received from other cells or base stations are treated as inter-cell interference and are avoided in the spatial, frequency or time domain. Alternatively, in the class of joint processing and joint transmission, data to SS  116  is substantially simultaneously transmitted from multiple transmission points to improve the received signal quality and/or cancel activity interference for other subscriber stations. Data intended for a particular SS  116  is shared among different cells, such as between BS  102  and BS  103 , and is jointly processed at these cells. As a result of this joint processing, the received signals at SS  116  will be coherently or non-coherently added up together. The signals received from other cells or base stations are treated as useful signals that contribute to a much higher received SNR at SS  116 . Within this mode of operation, the two classes of transmission schemes are: CoMP SU-MIMO and CoMP For CoMP SU-MIMO, the CoMP joint transmission can increase both the average cell throughput together with the cell-edge user throughput. 
     SS  116  can receive signals H 11    135  from BS  102  and signals H 21    140  from BS  103  respectively. SS  116  superimposes the signals with each other instead of treating one of the signals as interfering. For example, BS  102  includes a number, N T1 , of transmit antenna. Additionally, SS  116  includes a number, N R , of receive antennas. The received signal at SS  116  can be represented by Equation 1:
 
Y 1 =H 11 w 1 X 1 +H 21 w 2 X 1 +N 1    [Eqn. 1].
 
     In Equation 1, H 11    135  and H 21    140  represent the respective channel gains from BS  102  and BS  103  to SS  116 . Additionally, Y 1  is the N R ×1 vector of received signal at SS  116 , X 1  is the intended message for SS  116 , w i  is the N T1 ×v precoding vector of transmitted signal at BS  102 , and N i  is the N R ×1 AWGN noise vector. Further, v is the number of transmission layers of signal X 1 . 
       FIG. 1C  illustrates CMCS, CRCS and Active CoMP Sets according to embodiments of the present disclosure. The embodiment shown in  FIG. 1C  is for illustration only. Other embodiments could be used without departing from the scope of this disclosure. 
     In order to perform the CoMP joint processing operation, the network decides which set of cells will be transmitting to a particular CoMP UE (e.g., CoMP subscriber station) and what the related channel information is. In some embodiments, there exist several CoMP sets. The network first configures a set of cells (“CoMP measurement cell set (CMCS)”) to be measured by CoMP subscriber stations. The CMCS  145  is a set of cells monitored, measured, and reported by the CoMP UE. The CMCS  145  is configured semi-statically and can be completely determined by the network or be determined by the network with the assistant from CoMP UEs. Based on the measurements on the “CMCS”  145 , the network will then configure another set of cells (“CoMP reporting cell set (CRCS)  150 ”) to be the set of cells that CoMP UEs should report the information related to channel knowledge (channel coefficients, precoding matrix indices, channel quality indices and so forth). This CRCS  150  can be configured by the network with the assistance of the CoMP UEs. In some embodiments, to enable this procedure SS  116  can feedback a received SINR or an indication of preference. After obtaining the channel related information, the network decides the “Active CoMP set”  155  (the set of cells which send CoMP PDSCH to the CoMP UE) and performs the CoMP joint processing. That is, the network determines which set of cells, referred to as the Active CoMP set  155 , will transmit to the CoMP UE. 
     The configuration of the CRCS  150  can be semi-statistic and subscriber station-specific. The configuration of the CRCS  150  and can be important for the uplink overhead since the UL channel quality reporting of SS  116 , when a CoMP subscriber station, is tied to this set. In some embodiments, the reporting within the CRCS  150  is dynamic. Since the CRCS  150  can be relatively large, such as three (3) cells or more, if SS  116  reports channel related information for all the cells within the CRCS  150  all the time, the overhead can be very large. Furthermore, since demodulation of CoMP PDSCH will be based on DRS, R1-091066, “Way forward on downlink reference signals for LTE-A”, the contents of which hereby are incorporated by reference, the network can be free to decide the active CoMP set  155 . Therefore, if the network decides to use fewer transmission points within the CRCS  150 , the network only needs to know channel related information for a subset of the CRCS  150 . The dynamic channel feedback reporting will then significantly reduce the feedback overhead. 
     In CoMP joint processing, a collision between CoMP PDSCH and reference signals (RS) including common reference signals (CRS) from different cells may occur. This problem can occur where cell-specific frequency/time shifts are used for the reference signals in the cells involved in the joint transmission and, at the same time, the PDSCH mapping is assumed to be the same in all the cells. In general, this issue exists for non-CoMP subscriber stations when their PDSCH collides with reference signals from other cells. However, CoMP subscriber stations can be more susceptible to this type of PDSCH-to-RS interference because the PDSCH received is assumed to be coherently combined over the air. 
     The demodulation of CoMP PDSCH can be based on DRS to enable transparent transmission between SS  116  and the active CoMP set. That is, SS  116 , as a CoMP subscriber station, should not be aware of the active CoMP set. 
       FIG. 2  illustrates an exemplary base station in greater detail according to one embodiment of the present disclosure. The embodiment of base station  102  illustrated in  FIG. 2  is for illustration only. Other embodiments of the base station  102  could be used without departing from the scope of this disclosure. 
     Base station  102  comprises base station controller (BSC)  210  and base transceiver subsystem (BTS)  220 . A base station controller is a device that manages wireless communications resources, including the base transceiver subsystems, for specified cells within a wireless communications network. A base transceiver subsystem comprises the RF transceivers, antennas, and other electrical equipment located in each cell site. This equipment may include air conditioning units, heating units, electrical supplies, telephone line interfaces and RF transmitters and RF receivers. For the purpose of simplicity and clarity in explaining the operation of the present disclosure, the base transceiver subsystems in each of cells  121 ,  122  and  123  and the base station controller associated with each base transceiver subsystem are collectively represented by BS  101 , BS  102  and BS  103 , respectively. 
     BSC  210  manages the resources in cell site  121 , including BTS  220 . BTS  220  comprises BTS controller  225 , channel controller  235 , transceiver interface (IF)  245 , RF transceiver unit  250 , and antenna array  255 . Channel controller  235  comprises a plurality of channel elements, including exemplary channel element  240 . BTS  220  also comprises a memory  260 . The embodiment memory  260  included within BTS  220  is for illustration only. Memory  260  can be located in other portions of BS  102  without departing from the scope of this disclosure. 
     BTS controller  225  comprises processing circuitry and memory capable of executing an operating program that communicates with BSC  210  and controls the overall operation of BTS  220 . Under normal conditions, BTS controller  225  directs the operation of channel controller  235 , which contains a number of channel elements, including channel element  240 , that perform bi-directional communications in the forward channels and the reverse channels. A forward channel refers to a channel in which signals are transmitted from the base station to the mobile station (also referred to as DOWNLINK communications). A reverse channel refers to a channel in which signals are transmitted from the mobile station to the base station (also referred to as UPLINK communications). In an advantageous embodiment of the present disclosure, the channel elements communicate according to an OFDMA protocol with the mobile stations in cell  120 . Transceiver IF  245  transfers the bi-directional channel signals between channel controller  240  and RF transceiver unit  250 . The embodiment of RF transceiver unit  250  as a single device is for illustration only. RF transceiver unit  250  can separate transmitter and receiver devices without departing from the scope of this disclosure. 
     Antenna array  255  transmits forward channel signals received from RF transceiver unit  250  to mobile stations in the coverage area of BS  102 . Antenna array  255  also sends to transceiver  250  reverse channel signals received from mobile stations in the coverage area of BS  102 . In some embodiments of the present disclosure, antenna array  255  is a multi-sector antenna, such as a three-sector antenna in which each antenna sector is responsible for transmitting and receiving in a 120° arc of coverage area. Additionally, RF transceiver  250  may contain an antenna selection unit to select among different antennas in antenna array  255  during transmit and receive operations. 
     According to some embodiments of the present disclosure, BTS controller  225  is operable to execute programs, such as an operating system (OS) and processes for CoMP reporting and transparent resource mapping, stored in a memory  260 . Memory  260  can be any computer readable medium, for example, the memory  260  can be any electronic, magnetic, electromagnetic, optical, electro-optical, electro-mechanical, and/or other physical device that can contain, store, communicate, propagate, or transmit a computer program, software, firmware, or data for use by the microprocessor or other computer-related system or method. Memory  260  comprises a random access memory (RAM) and another part of memory  260  comprises a Flash memory, which acts as a read-only memory (ROM). 
     BSC  210  is operable to maintain communications between BS  102  and BS  101  and BS  103 . BS  102  communicates to BS  101  and BS  103  via the wireless connection  131 . In some embodiments, the wireless connection  131  is wire-line connection. 
       FIG. 3  illustrates an exemplary wireless subscriber station according to embodiments of the present disclosure. The embodiment of wireless subscriber station  116  illustrated in  FIG. 3  is for illustration only. Other embodiments of the wireless subscriber station  116  could be used without departing from the scope of this disclosure. 
     Wireless subscriber station  116  comprises antenna  305 , radio frequency (RF) transceiver  310 , transmit (TX) processing circuitry  315 , microphone  320 , and receive (RX) processing circuitry  325 . SS  116  also comprises speaker  330 , main processor  340 , input/output (I/O) interface (IF)  345 , keypad  350 , display  355 , and memory  360 . Memory  360  further comprises basic operating system (OS) program  361  and applications for CoMP reporting and transparent resource mapping  362 . 
     Radio frequency (RF) transceiver  310  receives from antenna  305  an incoming RF signal transmitted by a base station of wireless network  100 . Radio frequency (RF) transceiver  310  down-converts the incoming RF signal to produce an intermediate frequency (IF) or a baseband signal. The IF or baseband signal is sent to receiver (RX) processing circuitry  325  that produces a processed baseband signal by filtering, decoding, and/or digitizing the baseband or IF signal. Receiver (RX) processing circuitry  325  transmits the processed baseband signal to speaker  330  (i.e., voice data) or to main processor  340  for further processing (e.g., web browsing). 
     Transmitter (TX) processing circuitry  315  receives analog or digital voice data from microphone  320  or other outgoing baseband data (e.g., web data, e-mail, interactive video game data) from main processor  340 . Transmitter (TX) processing circuitry  315  encodes, multiplexes, and/or digitizes the outgoing baseband data to produce a processed baseband or IF signal. Radio frequency (RF) transceiver  310  receives the outgoing processed baseband or IF signal from transmitter (TX) processing circuitry  315 . Radio frequency (RF) transceiver  310  up-converts the baseband or IF signal to a radio frequency (RF) signal that is transmitted via antenna  305 . 
     In some embodiments of the present disclosure, main processor  340  is a microprocessor or microcontroller. Memory  360  is coupled to main processor  340 . According to some embodiments of the present disclosure, part of memory  360  comprises a random access memory (RAM) and another part of memory  360  comprises a Flash memory, which acts as a read-only memory (ROM). 
     Main processor  340  executes basic operating system (OS) program  361  stored in memory  360  in order to control the overall operation of wireless subscriber station  116 . In one such operation, main processor  340  controls the reception of forward channel signals and the transmission of reverse channel signals by radio frequency (RF) transceiver  310 , receiver (RX) processing circuitry  325 , and transmitter (TX) processing circuitry  315 , in accordance with well-known principles. 
     Main processor  340  is capable of executing other processes and programs resident in memory  360 . Main processor  340  can move data into or out of memory  360 , as required by an executing process. In some embodiments, the main processor  340  is configured execute programs, such as OS  361  and processes for CoMP reporting and transparent resource mapping  362 . The main processor  340  can execute the CoMP reporting and transparent resource mapping  362  based on OS program  361  or in response to a signal received from BS  102 . Main processor  340  is also coupled to I/O interface  345 . I/O interface  345  provides subscriber station  116  with the ability to connect to other devices such as laptop computers and handheld computers. I/O interface  345  is the communication path between these accessories and main controller  340 . 
     Main processor  340  is also coupled to keypad  350  and display unit  355 . The operator of subscriber station  116  uses keypad  350  to enter data into subscriber station  116 . Display  355  may be a liquid crystal display capable of rendering text and/or at least limited graphics from web sites. Alternate embodiments may use other types of displays. 
     In some embodiments, the network first configures, via higher layer signaling, a set of cells, i.e., the CMCS  145 , to be measured by CoMP UEs, i.e., SS  116 . After obtaining a feedback from SS  116 , the network semi-statistically configures, via higher layer signaling, a second set of cells, i.e., the CRCS  150 , to be the set of cells to which SS  116  reports information related to the channel. 
       FIG. 4  illustrates an uplink scheduling grant for CoMP transmissions according to embodiments of the present disclosure. The embodiment of the scheduling grant  400  shown in  FIG. 4  is for illustration only. Other embodiments could be used without departing from the scope of this disclosure. 
     In some embodiments, the network dynamically assigns channel information related reports, such as a channel quality index (CQI) report, within the CRCS  150 . Additionally, the reporting set, CRCS  150 , may not be used since the measurement set, CMCS  145 , can be used to serve as the reporting set (that is, the measurement set and the reporting set can be merged into the measurement set). The uplink scheduling grant  400  includes a bitmap  408  included in a new downlink control information (DCI) format. The bits  410 ,  412 ,  414  indicate the cells to be reported by SS  116  on the channel related information through the CQI report. The cell IDs of these cells are available at SS  116 . For example, the first bit  410  corresponds to BS  102 , the second bit  412  corresponds to BS  103  and the third bit  414  corresponds to BS  101 . The default ordering of the cells within the CRCS  150  can be in increasing order of the cell IDs or in decreasing order of the cell IDs. For each bit  410 ,  412 ,  414 , “0” can indicate that the corresponding cell, such as BS  102 , is needed for channel information related feedback report, such as the CQI report and vice versa. 
     For example, using the uplink scheduling grant  400  with the new DCI format shown in  FIG. 4 , it is indicated to SS  116  that SS  116  needs to feedback channel related information concerning BS  102  (Cell 0) and BS  101  (Cell 2) during the CQI report process. The ordering of the cells in the bitmap  408  can be in the increasing order of the cell IDs, decreasing order or any other predetermined order. In the bitmap  408  all the cells or base stations within the CRCS  150  will be indicated by the bitmap  408 . The overall process can be illustrated with respect to  FIG. 5 . 
       FIG. 5  illustrates a process for network configuration of CoMP sets according to embodiments of the present disclosure. The embodiment shown in  FIG. 5  is for illustration only. Other embodiments could be used without departing from the scope of this disclosure. 
     The network  505  configures  510  the CMCS  145  for SS  116  via higher layer signaling. The network  505  can configure  510  the CMCS  145  to SS  116  through a radio resource control (RRC) configuration. Then, SS  116  knows which cells are included in the CMCS  145 . Thereafter, SS  116  transmits a measurement report  515  regarding each of the cells included in the CMCS  145 . The network  505  configures  520  the CRCS  150 . The CRCS  150  can be configured as a periodic CQI. The network  505  then configures  525  a subset of the CRCS  150  to be the set of cells regarding which SS  116  should report the information related to channel knowledge. The subset of the CRCS  150  can be an aperiodic CQI report. Accordingly, SS  116  can down-select, from the CMCS  145  and CRCS  150 , the cells under review. For example, SS  116  can perform aperiodic CQI reporting of the subset of the cells included in the CRCS  150 . 
       FIG. 6  illustrates another uplink scheduling grant for CoMP transmissions according to embodiments of the present disclosure. The embodiment of the scheduling grant  600  shown in  FIG. 6  is for illustration only. Other embodiments could be used without departing from the scope of this disclosure. 
     In some embodiments, the bitmap  608  only indicates the cells or base stations, other than the anchor cell, within the CRCS. In this setup, SS  116  always reports channel related information concerning BS  102  (the anchor cell) during the CQI report process. For example, when BS  102  (Cell 0) is the anchor cell, only two (2) bits of the bitmap  608  are needed to indicate the other cells, BS  101  and BS  103 , within the CoMP set. The mapping can be in increasing order of the cell ID, in decreasing order of the cell ID or another predetermined order as configured by higher layer. For example, SS  116  can include a bitmap table, such as Table 1 below, stored in memory  360 . SS  116  can interpret the bitmap  608  according to Table 1. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Bitmap of Cell Selection for CQI reporting 
               
            
           
           
               
               
               
            
               
                   
                   
                 Reporting Cells of the CQI 
               
               
                   
                 Bit in the field 
                 Report Process 
               
               
                   
               
               
                   
                 [0 0] 
                 Cell 0 
               
               
                   
                 [0 1] 
                 Cell 0 and Cell 2 
               
               
                   
                 [1 0] 
                 Cell 0 and Cell 1 
               
               
                   
                 [1 1] 
                 Cell 0, Cell 1, and Cell 2 
               
               
                   
               
            
           
         
       
     
     For example, when the bitmap is “1 0”, SS  116  reports channel related information for BS  102  (the anchor cell, cell 0) and BS  103  (cell 1). 
     In some embodiments, the PDSCH is transmitted only in the resource elements that will not overlap with any of the possible reference signals, such as one or more CRSs. In this way, the PDSCH transmission of CoMP joint processing can be transparent in the sense that the SS  116  does not need to know the actual “active CoMP set”. SS  116  may not expect to receive a CoMP PDSCH from the resource elements that have the possibility of colliding with CRS from other cells. 
       FIG. 7  illustrates CoMP PDSCH resource mapping according to embodiments of the present disclosure. The embodiment of the CoMP PDSCH resource maps  700 ,  701  shown in  FIG. 7  is for illustration only. Other embodiments could be used without departing from the scope of this disclosure. 
     For example, for the case where four CRSs are configured for each cell within the active CoMP set  155 , the control region  705  for the CoMP joint processing is sent in the first three OFDM symbols  721 ,  722 ,  723  while the CoMP PDSCH region starts from the fourth OFDM symbol  724  in one subframe. The CoMP PDSCH Mapping includes a CoMP PDSCH Map  700  for BS  102  (the anchor cell, i.e., cell 0) and a CoMP PDSCH Map  701  for BS  103  (cell 1). In each CoMP PDSCH resource map  700 ,  701 , R denotes a downlink reference signal such that R 0 , R 1 , R 2  and R 3  are the common reference symbols. It will be understood that R is not limited to a common reference signal and that R can refer to any reference signal without departing from the scope of this disclosure. The shaded resource elements (REs)  710  are the REs where a CRS-PDSCH collision can occur. Therefore, the shaded REs  710  are punctured and, thus, not used for transmitting CoMP PDSCH (data)  715 . As such, SS  116  is not expecting to receive data from the second  722 , fifth  725 , eighth  728 , ninth  729  and twelfth  732  OFDM symbols in a normal CP subframe. When an RE is punctured, such as by the BS, no data or reference symbol is transmitted in that RE. Puncturing the shaded REs  710  enables a reference symbol, such as the CRS, to be received stronger than if data  715  is transmitted in the shaded REs  710 . 
     In another example, illustrated in  FIG. 8 , two CRSs, R 0  and R 1 , are configured for each cell within the active CoMP set  155 . In the CoMP PDSCH resource map  800  for BS  102  (the anchor cell, cell 0) and the CoMP PDSCH resource amp  801  for BS  103  (cell 1), the CoMP PDSCH region starts from the fourth OFDM symbols  824  in one subframe. The shaded resource elements (REs)  810  are the REs where a CRS-PDSCH collision can occur. Accordingly, the shaded REs  810  are punctured such that SS  116  is not expecting to receive data  815  from the fifth  825 , eighth  828  and twelfth  832  OFDM symbols. 
     In some embodiments, the CoMP PDSCH resource mapping is performed according to the cell-specific shifts of the cell IDs of the CRCS. As shown in  FIG. 1C , SS  116  (i.e., the CoMP UE) will be required to report channel related information to the cells in the CRCS  150  during the CQI report process; therefore, the Cell IDs of the cells within CRCS  150  will be available at the CoMP UEs, such as SS  116 . Under this situation, SS  116  does not expect to receive data from resource elements that will overlap with any of the possible CRSs within the CRCS  150 . 
     In 3GPP TS36.211. v8.5.0. “EUTRA: Physical Channels and Modulation”, the contents of which are incorporated by reference, the cell-specific frequency shift is given by 
               v   shift     =       N   ID   cell     ⁢   mod   ⁢           ⁢   6.           
Assume the cell IDs of the cells in the CRCS are
 
               N     ID   ⁢           ⁢   1     cell     ,     N     ID   ⁢           ⁢   2     cell           
and
 
               N     ID   ⁢           ⁢   3     cell     ,         
the set of possible cell-specific frequency shift can be illustrated by Equation 2:
 
                     v   shift     =     {       v   i     ,     i   =   1     ,   2   ,     3   ⁢              v   i     =       N     ID   ⁢           ⁢   i     cell     ⁢   mod   ⁢           ⁢   6       }     .                   [     Eqn   .           ⁢   2     ]               
Then, SS  116  does not expect to receive CoMP PDSCH from the positions of the CRS resource elements of the described frequency shifts.
 
       FIG. 9  illustrates CoMP PDSCH Resource Mapping Based on CRCS 1  according to embodiments of the present disclosure. For example, if the CRCS 1  includes three cells, in which the cells IDs are ‘0’ for BS  102 , ‘2’ for BS  101  and ‘6’ for another BS. Then the CoMP PDSCH resource mapping can be as shown in  FIG. 9  for the case of two CRSs, R 0  and R 1 , configuration. The CoMP PDSCH Mapping includes a CoMP PDSCH Map  900  for BS  102  (the anchor cell, i.e., cell 0), a CoMP PDSCH Map  901  for BS  103  (cell 1), and a CoMP PDSCH Map  902  for the cell  6  BS. In each of the CoMP PDSCH Maps  900 ,  901 ,  902 , the control region  905  for the CoMP joint processing is sent in the first three OFDM symbols  921 ,  922 , and  923  while the CoMP PDSCH region starts from the fourth OFDM symbol  924 . The shaded resource elements (REs)  910  are the REs in which a CRS-PDSCH collision can occur. Therefore the shaded REs  910  are punctured and are the REs in which SS  116  does not expect to receive data  915 . 
       FIG. 10  illustrates another example of CoMP PDSCH resource mapping according to this disclosure. In  FIG. 10 , a CRCS 2  is utilized for the case of two CRSs, R 0  and R 1 , configuration. The CRCS 2  includes three cells in which the cells IDs are ‘0’ for BS  102 , ‘2’ for BS  101  and ‘6’ for another BS. The CoMP PDSCH Mapping includes a CoMP PDSCH Map  1000  for BS  102  (the anchor cell, i.e., cell 0), a CoMP PDSCH Map  1002  for BS  101  (cell 2), and a CoMP PDSCH Map  1003  for the cell  6  BS. In each of the CoMP PDSCH Maps  1000 ,  1002 ,  1003 , the control region  1005  for the CoMP joint processing is sent in the first three OFDM symbols  1021 ,  1022 , and  1023  while the CoMP PDSCH region starts from the fourth OFDM symbol  1024 . The shaded resource elements (REs)  1010  are the REs in which a CRS-PDSCH collision can occur. Therefore the shaded REs  1010  that are punctured and are the REs in which SS  116  does not expect to receive data  1015 . 
       FIG. 11  illustrates another example of CoMP PDSCH resource mapping according to this disclosure. In  FIG. 11 , a CRCS 3  is utilized for the case of two CRSs, R 0  and R 1 , configuration. The CRCS 3  includes three cells in which the cells IDs are ‘0’ for BS  102 , ‘6’ for another BS and ‘12’ for yet another BS. The CoMP PDSCH Mapping includes a CoMP PDSCH Map  1100  for BS  102  (the anchor cell, i.e., cell 0), a CoMP PDSCH Map  1103  for cell  6  BS, and a CoMP PDSCH Map  1104  for the cell  12  BS. In each of the CoMP PDSCH Maps  1100 ,  1102 ,  1103 , the control region  1105  for the CoMP joint processing is sent in the first three OFDM symbols  1121 ,  1122 , and  1123  while the CoMP PDSCH region starts from the fourth OFDM symbol  1124 . In CRCS 3 , no REs exist in which a CRS-PDSCH collision can occur since the CRSs, R 0  and R 1 , are transmitted in the same REs (also referred to as CSREs). 
     The resource elements mapping for CoMP PDSCH illustrated in  FIGS. 7 through 11  are transparent schemes where SS  116  does not need to receive additional information regarding the CoMP PDSCH resource mapping in the downlink grant. However, in some embodiments an indication is included in the downlink grant (such as in possible new DCI formats) to indicate the possible CRS-PDSCH overlapping pattern of the active CoMP set; and SS  116  can expect to avoid performing demodulation on those overlapped resource elements. 
       FIG. 12  illustrates frequency shifts for CRS according to embodiments of the present disclosure. The embodiment of the frequency shifts shown in  FIG. 12  is for illustration only. Other embodiments could be used without departing from the scope of this disclosure. 
     The CoMP UE, such as SS  116 , can receive an explicit indication regarding which RE&#39;s to avoid. The indicator, included in the downlink grant, can indicate the possible CRS-PDSCH overlapping patterns and, as such, expressly indicate which REs to avoid. 
     For example, for the two CRS and four CRS configurations, for each OFDM symbol containing a CRS, only two other cell-specific frequency shifts can exist in that symbol. BS  102  (e.g., the anchor cell) transmits the CRS, R 0  and R 1 , in a symbol  1205  as shown. The CRS, R 0  and R 1 , are transmitted by BS  103  in the symbol  1205  using the next corresponding frequency, shift_ 1   1210 . That is, BS  103  shifts the frequency for the CRS by one frequency unit in the resource map from the anchor cell, BS  102 . The CRS, R 0  and R 1 , are transmitted by BS  101  in the symbol  1205  using the next corresponding frequency, shift_ 2   1215 . That is, BS  103  shifts the frequency for the CRS by two from the anchor cell, BS  102 . 
     Therefore, from the active CoMP set  155 , four possible CRS-PDSCH overlapping patterns exist: none of the other frequency shifts, possible frequency shift_ 1   1210 , possible frequency shift_ 2   1215 , and both of the other possible frequency shifts. Two bits can be used to indicate the overlapping pattern in the downlink grant. SS  116  can store a possible bitmap that can be summarized according to Table 2. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Bitmap of CRS Possible Positions for 2 CRS and 4 
               
               
                 CRS Configuration 
               
            
           
           
               
               
               
            
               
                   
                 Bit in the field 
                 CRS Position 
               
               
                   
               
               
                   
                 [0 0] 
                 Only anchor cell 
               
               
                   
                 [0 1] 
                 Anchor Cell, and Possible 
               
               
                   
                   
                 frequency shift 2 
               
               
                   
                 [1 0] 
                 Anchor Cell and Possible 
               
               
                   
                   
                 frequency shift 1 
               
               
                   
                 [1 1] 
                 Anchor Cell, Possible frequency 
               
               
                   
                   
                 shift 1 and Possible frequency 
               
               
                   
                   
                 shift 2 
               
               
                   
               
            
           
         
       
     
     In Table 2, the possible frequency shift_ 1   1210  can be defined as the smallest frequency shift value other than anchor cell frequency shift and possible frequency shift_ 2   1215  can be defined as the other frequency shift value and vice versa. After receiving the downlink grant, SS  116  can expect to receive CoMP PDSCH, that is, data  1315 , from the PDSCH resource elements region, except for the REs  1310  indicated from the bitmap. For example, assume the cell ID of the anchor cell, BS  102  is ‘0,’ the expected RE mapping of CoMP PDSCH can be illustrated in  FIG. 13  for the case where the CoMP PDSCH region starts from the fourth OFDM symbol  1305 . 
     For the case where only one CRS is configured at each cell, five other possible frequency shifts exist. Therefore five bits are used to indicate the possible CRS-PDSCH overlapping patterns as illustrated in  FIG. 14 . 
     The bitmap can be formed the same way as the two CRS and four CRS cases, while the ordering of the other possible frequency shifts can be in the increasing order or decreasing order of mod 6, other than the anchor cell. In this case, the i th  bit in the bit field indicates whether the possible frequency shift ‘i’ is on or not (‘1’ stands for on and ‘0’ stands for off, and vice versa). For example, a ‘1’ in the i th  bit in the bitmap indicates that the SS  116  will not expect to receive CoMP PDSCH (e.g., data) from resource element (k, L) as shown in Equation 3:
 
k=6m+(v+v shift +i)mod6   [Eqn. 3]
 
     
       
         
           
             
               L 
               = 
               0 
             
             , 
             
               
                 N 
                 symb 
                 DL 
               
               - 
               3 
             
           
         
       
       
         
           
             
               m 
               = 
               0 
             
             , 
             1 
             , 
             … 
             ⁢ 
             
                 
             
             , 
             
               
                 2 
                 · 
                 
                   N 
                   RB 
                   DL 
                 
               
               - 
               1. 
             
           
         
       
     
     The variables v and v shift  define the position in the frequency domain for the different reference signals where v is given by Equation 4: 
     
       
         
           
             
               
                 
                   v 
                   = 
                   
                     { 
                     
                       
                         
                           
                             0 
                           
                           
                             
                               
                                 if 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 L 
                               
                               = 
                               0 
                             
                           
                         
                         
                           
                             1 
                           
                           
                             
                               
                                 if 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 L 
                               
                               ≠ 
                               0 
                             
                           
                         
                       
                       . 
                     
                   
                 
               
               
                 
                   [ 
                   
                     Eqn 
                     . 
                     
                         
                     
                     ⁢ 
                     4 
                   
                   ] 
                 
               
             
           
         
       
     
     The cell-specific frequency shift is given by 
               v   shift     =       N   ID   cell     ⁢   mod   ⁢           ⁢   6           
where
 
             N   ID   cell         
is the anchor cell ID.
 
       FIG. 15  illustrates a resource element mapping of CoMP PDSCH based on overlapping patterns according to embodiments of the present disclosure. The embodiment shown in  FIG. 15  is for illustration only. Other embodiments could be used without departing from the scope of this disclosure. 
     For example, when the cell ID of BS  102 , e.g., the anchor cell, is ‘0,’ the expected RE mapping of CoMP PDSCH can be as illustrated in  FIG. 15 . In the CoMP PDSCH resource map  1500  for BS  102  (the anchor cell, cell 0) and the CoMP PDSCH resource amp  1501  for BS  103  (cell 1), the CoMP PDSCH region starts from the fourth OFDM symbols  1524  in one subframe. Further, the bitmap in the DL grant for CoMP PDSCH resource map  1500  is “1 0 1 0 1” and the bitmap for CoMP PDSCH resource map  1501  is “1 1 0 0 0.” The shaded resource elements (REs)  1510  are the REs where a CRS-PDSCH collision can occur. Accordingly, the shaded REs  1510  are punctured such that SS  116  is not expecting to receive data  1515  in the shaded REs  1510 . 
     In some embodiments, the CRS-PDSCH overlapping pattern is configured semi-statistically. The bitmap of the overlapping pattern can be sent to SS  116  through higher layer signaling semi-statistically. Once SS  116  receives the indication, SS  116  will assume certain type of CoMP PDSCH resource mapping for the downlink transmission. 
     Although the present disclosure has been described with an exemplary embodiment, various changes and modifications may be suggested to one skilled in the art. It is intended that the present disclosure encompass such changes and modifications as fall within the scope of the appended claims.