Patent Publication Number: US-10320451-B2

Title: Downlink channel parameters determination for a multiple-input-multiple-output (MIMO) system

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. patent application Ser. No. 14/108,207, filed Dec. 16, 2013, entitled “Downlink Channel Parameters Determination For A Multiple-Input-Multiple-Output (Mimo) System,” which is a continuation of U.S. patent application Ser. No. 13/543,371, filed Jul. 6, 2012, entitled “Downlink Channel Parameters Determination For A Multiple-Input-Multiple-Output (Mimo) System,” which is a continuation of U.S. patent application Ser. No. 12/882,957, filed Sep. 15, 2010, entitled “Downlink Channel Parameters Determination For A Multiple-Input-Multiple-Output (Mimo) System,” which is a continuation of U.S. patent application Ser. No. 11/617,313, filed Dec. 28, 2006, entitled “Downlink Channel Parameters Determination For A Multiple-Input-Multiple-Output (MIMO) System,” which claims priority to U.S. Patent Application No. 60/797,042, filed May 1, 2006, entitled “Methods and Apparatus for Providing A Power Loading and Modulation Selection System Associated with A Multiple-Input-Multiple-Output (MIMO) System,” and to U.S. Patent Application No. 60/784,418, filed Mar. 20, 2006, entitled “System, Apparatus, Associated Methods and Protocols to Support Next Generation Wireless Communications,” the entire disclosures of which are hereby incorporated by reference in their entireties for all purposes, except for those sections, if any, that are inconsistent with this specification. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to wireless communication systems, and more particularly, to methods and apparatus for providing downlink channel parameters, such as bit or power loading and modulation or coding scheme selection for downlink channels in a multiple-input-multiple-output system. 
     BACKGROUND 
     As wireless communication becomes more and more popular at offices, homes, schools, etc., different wireless technologies and applications may work in tandem to meet the demand for computing and communications at anytime and/or anywhere. For example, a variety of wireless communication networks may co-exist to provide a wireless environment with more computing and/or communication capability, greater mobility, and/or eventually seamless roaming. 
     In particular, wireless personal area networks (WPANs) may offer fast, short-distance connectivity within a relatively small space such as an office workspace or a room within a home. Wireless local area networks (WLANs) may provide broader range than WPANs within office buildings, homes, schools, etc. Wireless metropolitan area networks (WMANs) may cover a greater distance than WLANs by connecting, for example, buildings to one another over a broader geographic area. Wireless wide area networks (WWANs) may provide the broadest range as such networks are widely deployed in cellular infrastructure. Although each of the above-mentioned wireless communication networks may support different usages, co-existence among these networks may provide a more robust environment with anytime and anywhere connectivity. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present invention will be readily understood by the following detailed description in conjunction with the accompanying drawings. To facilitate this description, like reference numerals designate like structural elements. Embodiments of the invention are illustrated by way of example and not by way of limitation in the figures of the accompanying drawings. 
         FIG. 1  is a schematic diagram representation of an example wireless communication system according to an embodiment of the methods and apparatus disclosed herein; 
         FIG. 2  is a block diagram representation of an example multiple-input-multiple-output (MIMO) system of the example wireless communication system of  FIG. 1 ; 
         FIG. 3  is a block diagram representation of an example base station of the example MIMO system of  FIG. 2 ; 
         FIG. 4  depicts an example chart associated with throughput; 
         FIG. 5  depicts another example chart associated with throughput; 
         FIG. 6  depicts an example chart associated with probability density functions (PDFs); 
         FIG. 7  depicts yet another example chart associated with throughput; 
         FIG. 8  is a flow diagram representation of one manner in which the example base station of  FIG. 3  may be configured; and 
         FIG. 9  is a block diagram representation of an example processor system that may be used to implement the example base station of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION 
     In the following detailed description, reference is made to the accompanying drawings which form a part hereof wherein like numerals designate like parts throughout, and in which is shown by way of illustration embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present invention. Therefore, the following detailed description is not to be taken in a limiting sense, and the scope of embodiments in accordance with the present invention is defined by the appended claims and their equivalents. 
     Various operations may be described as multiple discrete operations in turn, in a manner that may be helpful in understanding embodiments of the present invention; however, the order of description should not be construed to imply that these operations are order dependent. 
     For the purposes of the present invention, the phrase “A/B” means A or B. For the purposes of the present invention, the phrase “A and/or B” means “(A), (B), or (A and B)”. For the purposes of the present invention, the phrase at least one of A, B, and C″ means “(A), (B), (C), (A and B), (A and C), (B and C), or (A, B and C)”. For the purposes of the present invention, the phrase “(A)B” means “(B) or (AB)” that is, A is an optional element. 
     The description may use the phrases “in an embodiment,” or “in embodiments,” which may each refer to one or more of the same or different embodiments. Furthermore, the terms “comprising,” “including,” “having,” and the like, as used with respect to embodiments of the present invention, are synonymous. 
     Embodiments of the present invention provide power loading and modulation selection systems and methods for a multiple-input-multiple-output (MIMO) system. 
     Referring to  FIG. 1 , an example wireless communication system  100 , in accordance with various embodiments of the present invention, may include one or more wireless communication networks, generally shown as  110 ,  120 , and  130 . In particular, the wireless communication system  100  may include a wireless personal area network (WPAN)  110 , a wireless local area network (WLAN)  120 , and a wireless metropolitan area network (WMAN)  130 . Although  FIG. 1  depicts three wireless communication networks, the wireless communication system  100  may include additional or fewer wireless communication networks. For example, the wireless communication networks  100  may include additional WPANs, WLANs, and/or WMANs. The methods and apparatus described herein are not limited in this regard. 
     The wireless communication system  100  may also include one or more subscriber stations, generally shown as  140 ,  142 ,  144 ,  146 , and  148 . For example, the subscriber stations  140 ,  142 ,  144 ,  146 , and  148  may include wireless electronic devices such as a desktop computer, a laptop computer, a handheld computer, a tablet computer, a cellular telephone, a pager, an audio and/or video player (e.g., an MP3 player or a DVD player), a gaming device, a video camera, a digital camera, a navigation device (e.g., a GPS device), a wireless peripheral (e.g., a printer, a scanner, a headset, a keyboard, a mouse, etc.), a medical device (e.g., a heart rate monitor, a blood pressure monitor, etc.), and/or other suitable fixed, portable, or mobile electronic devices. Although  FIG. 1  depicts five subscriber stations, the wireless communication system  100  may include more or less subscriber stations. 
     The subscriber stations  140 ,  142 ,  144 ,  146 , and  148  may use a variety of modulation techniques such as spread spectrum modulation (e.g., direct sequence code division multiple access (DS-CDMA) and/or frequency hopping code division multiple access (FH-CDMA)), time-division multiplexing (TDM) modulation, frequency-division multiplexing (FDM) modulation, orthogonal frequency-division multiplexing (OFDM) modulation, multi-carrier modulation (MDM), and/or other suitable modulation techniques to communicate via wireless links. In one example, the laptop computer  140  may operate in accordance with suitable wireless communication protocols that require very low power such as Bluetooth®, ultra-wide band (UWB), and/or radio frequency identification (RFID) to implement the WPAN  110 . In particular, the laptop computer  140  may communicate with devices associated with the WPAN  110  such as the video camera  142  and/or the printer  144  via wireless links. 
     In another example, the laptop computer  140  may use direct sequence spread spectrum (DSSS) modulation and/or frequency hopping spread spectrum (FHSS) modulation to implement the WLAN  120  (e.g., the 802.11 family of standards developed by the Institute of Electrical and Electronic Engineers (IEEE) and/or variations and evolutions of these standards). For example, the laptop computer  140  may communicate with devices associated with the WLAN  120  such as the printer  144 , the handheld computer  146  and/or the smart phone  148  via wireless links. The laptop computer  140  may also communicate with an access point (AP)  150  via a wireless link. The AP  150  may be operatively coupled to a router  152  as described in further detail below. Alternatively, the AP  150  and the router  152  may be integrated into a single device (e.g., a wireless router). 
     The laptop computer  140  may use OFDM modulation to transmit large amounts of digital data by splitting a radio frequency signal into multiple small sub-signals, which in turn, are transmitted simultaneously at different frequencies. In particular, the laptop computer  140  may use OFDM modulation to implement the WMAN  130 . For example, the laptop computer  140  may operate in accordance with the 802.16 family of standards developed by IEEE to provide for fixed, portable, and/or mobile broadband wireless access (BWA) networks (e.g., the IEEE std. 802.16-2004 (published Sep. 18, 2004), the IEEE std. 802.16e (published Feb. 28, 2006), the IEEE std. 802.16f (published Dec. 1, 2005), etc.) to communicate with base stations, generally shown as  160 ,  162 , and  164 , via wireless link(s). 
     Although some of the above examples are described above with respect to standards developed by IEEE, the methods and apparatus disclosed herein are readily applicable to many specifications and/or standards developed by other special interest groups and/or standard development organizations (e.g., Wireless Fidelity (Wi-Fi) Alliance, Worldwide Interoperability for Microwave Access (WiMAX) Forum, Infrared Data Association (IrDA), Third Generation Partnership Project (3GPP), etc.). The methods and apparatus described herein are not limited in this regard. 
     The WLAN  120  and WMAN  130  may be operatively coupled to a common public or private network  170  such as the Internet, a telephone network (e.g., public switched telephone network (PSTN)), a local area network (LAN), a cable network, and/or another wireless network via connection to an Ethernet, a digital subscriber line (DSL), a telephone line, a coaxial cable, and/or any wireless connection, etc. In one example, the WLAN  120  may be operatively coupled to the common public or private network  170  via the AP  150  and/or the router  152 . In another example, the WMAN  130  may be operatively coupled to the common public or private network  170  via the base station(s)  160 ,  162 , and/or  164 . 
     The wireless communication system  100  may include other suitable wireless communication networks. For example, the wireless communication system  100  may include a wireless wide area network (WWAN) (not shown). The laptop computer  140  may operate in accordance with other wireless communication protocols to support a WWAN. In particular, these wireless communication protocols may be based on analog, digital, and/or dual-mode communication system technologies such as Global System for Mobile Communications (GSM) technology, Wideband Code Division Multiple Access (WCDMA) technology, General Packet Radio Services (GPRS) technology, Enhanced Data GSM Environment (EDGE) technology, Universal Mobile Telecommunications System (UMTS) technology, Third Generation Partnership Project (3GPP) technology, standards based on these technologies, variations and evolutions of these standards, and/or other suitable wireless communication standards. Although  FIG. 1  depicts a WPAN, a WLAN, and a WMAN, the wireless communication system  100  may include other combinations of WPANs, WLANs, WMANs, and/or WWANs. The methods and apparatus described herein are not limited in this regard. 
     The wireless communication system  100  may include other WPAN, WLAN, WMAN, and/or WWAN devices (not shown) such as network interface devices and peripherals (e.g., network interface cards (NICs)), access points (APs), redistribution points, end points, gateways, bridges, hubs, etc. to implement a cellular telephone system, a satellite system, a personal communication system (PCS), a two-way radio system, a one-way pager system, a two-way pager system, a personal computer (PC) system, a personal data assistant (PDA) system, a personal computing accessory (PCA) system, and/or any other suitable communication system. Although certain examples have been described above, the scope of coverage of this disclosure is not limited thereto. 
     Referring to  FIG. 2 , an example wireless MIMO system  200 , in accordance with various embodiments of the present invention, may include a base station  210  and one or more subscriber stations, generally shown as  220  and  225 . The wireless MIMO system  200  may include a point-to-point MIMO system and/or a point-to-multiple point MIMO system. For example, a point-to-point MIMO system may include the base station  210  and the subscriber station  220 . A point-to-multiple point MIMO system may include the base station  210  and the subscriber station  225 . The base station  210  may transmit data streams to the subscriber stations  220 ,  225  simultaneously. For example, the base station  310  may transmit two data streams to the subscriber station  220  and one data stream to the subscriber station  225 . Although  FIG. 2  may depict one subscriber station, the wireless MIMO system  200  may include additional subscriber stations. 
     The base station  210  may transmit two or more data streams over four transmit antennas  250 , generally shown as  252 ,  254 ,  256 , and  258 . Although  FIG. 2  depicts four transmit antennas, the base station  210  may include additional or fewer transmit antennas. The methods and apparatus described herein are not limited in this regard. 
     In the example of  FIG. 3 , the base station  300  may include a network interface device (NID)  340 , a processor  350 , and a memory  360 . The NID  340 , the processor  350 , and the memory  360  may be operatively coupled to each other via a bus  370 . While  FIG. 3  depicts components of the base station  300  coupling to each other via the bus  370 , these components may be operatively coupled to each other via other suitable direct or indirect connections (e.g., a point-to-point connection or a point-to-multiple point connection). 
     The NID  340  may include a receiver  342 , a transmitter  344 , and an antenna  346 . The base station  300  may receive and/or transmit data via the receiver  342  and the transmitter  344 , respectively. The antenna  346  may include one or more directional or omni-directional antennas such as dipole antennas, monopole antennas, patch antennas, loop antennas, microstrip antennas, and/or other types of antennas suitable for transmission of radio frequency (RF) signals. Although  FIG. 3  depicts a single antenna, the base station  300  may include additional antennas. For example, the base station  300  may include a plurality of antennas to implement a multiple-input-multiple-output (MIMO) system. 
     Although the components shown in  FIG. 3  are depicted as separate blocks within the base station  300 , the functions performed by some of these blocks may be integrated within a single semiconductor circuit or may be implemented using two or more separate integrated circuits. For example, although the receiver  342  and the transmitter  344  are depicted as separate blocks within the NID  340 , the receiver  342  may be integrated into the transmitter  344  (e.g., a transceiver). The methods and apparatus described herein are not limited in this regard. 
     In general,  FIG. 4  depicts an example of throughput of a MIMO system with hybrid automatic repeat request (H-ARQ), in accordance with various embodiments. Solid black curves are for open-loop. The other solid curves are for closed-loop with adaptive bit loading (ABL). Dashed curves are for closed-loop without adaptive bit loading, i.e. uniform bit loading (UBL). The numbers in the brackets is the number of bits loaded on the stream per subcarrier. 
     In general,  FIG. 5  depicts another example of throughput of a MIMO system with H-ARQ, in accordance with various embodiments. Solid curves are for closed-loop with adaptive bit loading (ABL) and adaptive power loading. Dashed curves are for closed-loop with adaptive bit loading, but without adaptive power loading. The numbers in the brackets is the number of bits loaded on the stream per subcarrier. 
     Adaptive bit loading and adaptive power loading (or power water filling) across beamformed spatial channels may improve the performance of MIMO systems as shown in  FIGS. 4 and 5 . The bit and power loadings may be determined by the channel gains of the channels and the noise plus interference level on each channel. In singular value decomposition (SVD) beamformed MIMO, the interference across spatial channels is generally mitigated and may be ignored. The thermal noise level may be estimated using the KTB equation (where K is Boltzman&#39;s constant, T is temperature in Kelvin and B is signal bandwidth in Hz) and noise figure, e.g. 1-5 dB. The gain of each channel (or equivalently signal to noise plus interference ratio (SINR)) usually requires feedback. However, the feedback channel is generally costly in WMAN. Thus, it is desirable to reduce the feedback overhead. In a time division duplex (TDD) system, the feedback channel is generally reciprocal between downlink and uplink. A base station may use the uplink traffic or channel training to estimate the downlink channel. This saves the channel feedback. However, the channel reciprocity doesn&#39;t exist for a frequency division duplex (FDD) system. 
     In general,  FIG. 6  depicts PDFs of the singular values of MIMO channel matrix with 4×1, 4×2, 4×3, and 4×4 antenna configurations for IEEE 802.11n model B LOS (Line Of Sight). 
     In accordance with various embodiments of the present invention, although the channel matrix of MIMO is generally random, the singular values of the channel matrix, i.e. the gains of the beamformed channels, generally have narrower probability density functions (PDFs) than that of the channel matrix entry. The PDF gets narrower as the number of antennas increases, as may be seen in  FIG. 6 . The narrower the PDF, the more easily the random variable may be estimated. The stronger singular value generally has a narrower PDF than that of the weaker singular value. The strong singular values usually correspond to usable spatial channels. In other words, the singular values are easier to estimate than the matrix entry and the gain of usable channel is easier to estimate than the unusable channel. Furthermore, the correlation between antennas also narrows the PDF of the singular value, and makes the estimation relatively easier. Because the channel statistics (e.g. power level of channel matrix entry and antenna correlation) are the same or likely to be the same for uplink and downlink, the base station may use the mean of singular value in the uplink as the estimation of the instantaneous singular value in the downlink. The mean may be computed over frequency and/or time. In accordance with various embodiments, after the channel gain of the beamformed channel is estimated, the base station may select the usable channels to send data and may determine the modulation and power level for the selected channel. The performance of such a scheme, in accordance with various embodiments, is illustrated in  FIGS. 4 and 5 . 
     In accordance with various embodiments of the present invention, the estimation of noise plus interference level may be improved by the conventional channel quality (CQI) feedback. CQI feed back is commonly used in 3G and WiMAX. The collection of channel samples, which are used to estimate the mean, should follow the operation in the system. In accordance with various embodiments, when multi-user diversity is employed in an orthogonal frequency division multiple access (OFDMA) system, a subscriber station sorts the channel quality across frequency (and time) and requests that a base station uses the best channels to send data. For example, the whole frequency band is partitioned into chunks of contiguous subcarriers, and the subscriber station feeds back the indexes for the best three chunks and their beamforming matrixes. In accordance with various embodiments, the base station may use some of the fed back chunks to send data. Since the fed back channel is sorted, the base station may also sort the uplink channels with the same parameters, e.g. chunk size and the total bandwidth. The estimation may then be conducted on the sorted channel samples. In sum, the collection of the matrix samples in the base station from the uplink should be as close as possible to the matrix finally used in the downlink. The collected matrix may be transposed before use. The transpose reflects the asymmetry between downlink and uplink channels. 
     In accordance with various embodiments of the present invention, the idea of using the uplink channel to estimate downlink channel parameters may be extended for non-beamformed MIMO. For example, the per antenna rate control (PARC) mode may not employ transmit beamforming, but it may employ bit (and power) loading on each transmit antenna. In a conventional PARC mode, it requires the subscriber station to feed back the channel quality of each data stream or bit loading information for each transmit antenna, where one transmit antenna sends one data stream. In a modified PARC mode, a data stream may be sent by a spatial channel formed by multiple transmit antennas. The demodulation scheme is usually minimum mean-square error (MMSE) plus successive cancellation. If the demodulation scheme is known at the base station, the base station may collect channel matrixes in the uplink with the same or similar statistics as those used in the downlink for PARC, and it may estimate the channel quality of each data stream seen at the receiver using the same demodulation scheme. After the estimation is completed, the base station may decide how many streams are used and what the modulation and coding scheme for each stream should be. Although the estimation is generally not accurate, it still provides information about the instantaneous, random downlink channel. This may reduce the feedback overhead needed from the subscriber station. For example, the subscriber station may only need to provide differential information to refine the estimation using the mean. 
     In addition to PARC mode, the idea may be used by open loop modes, in accordance with various embodiments. For example, the base station may estimate the channel quality from the uplink to decide the number of data streams and modulation/coding scheme for the downlink. The number of data streams is generally dependent on the antenna correlations and SINR of each stream. SINR is generally dependent on received signal power (or path loss) and demodulation scheme. Once the demodulation scheme is known or estimated, the SINR may be estimated using the uplink channel samples. After the SINR is estimated, the number of usable streams and the modulation, coding scheme, and power level of the streams may be determined. 
     In addition to the mean of channel quality or singular value, other statistics such as, for example, variance may also be useful and may be estimated, in accordance with various embodiments. The information may be used to set margin for the selected power and bit loading. For example, a base station may use a lower bit loading scheme on the selected channel than that computed from the mean because the variance is large and the estimation is not reliable. There may be multiple ways to compute the mean, e.g. 
     
       
         
           
             
               
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     Once the number of usable channels K is estimated, the base station may dynamically ask a subscriber station to feed back information (such as beamforming matrix or SINR) only for the strongest K channels instead of all channels, in accordance with various embodiments of the present invention. This generally reduces the feedback overhead of (closed-loop) MIMO. In addition, putting transmission power in the strongest few channels instead of all channels may significantly improve performance in low SNR region. This may be seen in  FIG. 7 . Therefore, the selection of the channel number is an important application of the estimation by itself. 
     In accordance with various embodiments, the estimation from the uplink for the subscriber stations may also help the base station to schedule the downlink transmission. For example, the base station may pick subscriber stations with good channel quality to serve first and wait for the poor ones to change to be good (e.g. move out from a shadow fading). This type of scheduling is generally referred to as multiuser diversity. The uplink estimation may facilitate multiuser diversity scheduling. 
     In general,  FIG. 7  illustrates rank control that determines the number of usable channels, in accordance with various embodiments. The curves in legend 1 and 3 have the same maximum throughput while they use two and three channels respectively. Legend 1 performs better than legend 3. Similarly, legend 2 outperforms legend 4. 
     Exemplary pseudo code, in accordance with various embodiments of the present invention, may be as follows: 
     1. Base station collects uplink channels according the mode used in the downlink. The collected channels are transposed and treated as channels collected from the downlink; 
     2. Compute the mean and variance of the channel quality for each spatial channel or data stream; 
     3. Determine the number of usable streams or spatial channels, bit loading, power loading, and coding scheme on the usable channels or streams jointly; 
     4. Select subscriber station(s) to which to transmit; and 
     5. Conduct downlink transmission using determined parameters. 
     At a subscriber station, it generally needs to know the power of each power loaded channel for demodulation, in accordance with various embodiments. The base station may signal the power loading to a subscriber station using channel training symbols. The training symbols may be dedicated to the user in OFDMA system. Because the loading generally is on the dedicated pilots, it doesn&#39;t affect the channel estimation of other users. The dedicated pilot may be sent over the beamformed spatial channel. In addition to dedicated pilot, the power level may be specified in a control channel or a broadcast channel so that the receiver knows about the power level difference between the power loaded data symbol and the channel training symbols (e.g. pilots) that are not power loaded. 
     In accordance with various embodiments of the present invention,  FIG. 8  depicts one manner in which base station  300  may be configured to provide a power loading and modulation selection system. The example process  800  of  FIG. 8  may be implemented as machine-accessible instructions utilizing any of many different programming codes stored on any combination of machine-accessible media such as a volatile or non-volatile memory or other mass storage device (e.g., a floppy disk, a CD, and a DVD). For example, the machine-accessible instructions may be embodied in a machine-accessible medium such as a programmable gate array, an application specific integrated circuit (ASIC), an erasable programmable read only memory (EPROM), a read only memory (ROM), a random access memory (RAM), a magnetic media, an optical media, and/or any other suitable type of medium. 
     Further, although a particular order of actions is illustrated in  FIG. 8 , these actions may be performed in other temporal sequences. Again, the example process  800  is merely provided and described in conjunction with the system and apparatus of  FIGS. 2 and 3  as an example of one way to provide a power loading and modulation selection system. 
     In the example of  FIG. 8 , the process  800  may begin with base station  300  ( FIG. 3 ) collecting uplink channel information according to the mode used in the downlink (block  810 ). Based at least in part on the collected uplink channel information, the base station  300  may compute channel quality information of each spatial channel and/or data stream (block  820 ). For example, the base station may compute the mean and/or the variance of the channel quality for each spatial channel and/or data stream. The channel quality information may be computed by estimating a usable number of channels. Based at least in part on the channel quality information, the base station  300  may determine one or more downlink channel parameters (block  830 ). Downlink channel parameters may include the number of usable data streams, the number of usable spatial channels, bit loading, power loading, coding scheme, and/or other suitable parameters. The base station  300  may receive feedback information only for a subset of relatively stronger channels of the estimated usable channels (block  835 ). The base station  300  may select one or more subscriber stations to which to transmit (block  840 ) based at least in part on one or more downlink channel parameters. Accordingly, the base station  300  may communicate with one or more subscriber stations (e.g., the subscriber stations  220  and/or  225 ) based on the downlink channel parameters (block  850 ). The methods and apparatus described herein are not limited in this regard. 
     In general, the methods and apparatus described herein may use uplink channel to estimate parameters in the downlink channel. It reduces the feedback overhead for power and bit loading in MIMO system. The methods and apparatus described herein are not limited in this regard. 
     Although the methods and apparatus described herein may be associated with the Third Generation Partnership Project (3GPP) for the Long Term Evolution (LTE), the methods and apparatus described herein may be readily applicable with other suitable wireless technologies, protocols, and/or standards. The methods and apparatus described herein are not limited in this regard. 
       FIG. 9  is a block diagram of an example processor system  2000  adapted to implement methods and apparatus disclosed herein. The processor system  2000  may be a desktop computer, a laptop computer, a handheld computer, a tablet computer, a PDA, a server, an Internet appliance, a base station, an access point and/or any other type of computing device. 
     The processor system  2000  illustrated in  FIG. 9  includes a chipset  2010 , which includes a memory controller  2012  and an input/output (I/O) controller  2014 . The chipset  2010  may provide memory and I/O management functions as well as a plurality of general purpose and/or special purpose registers, timers, etc. that are accessible or used by a processor  2020 . In various embodiments, I/O controller  2014  of chipset  2010  may be endowed with all or portions of the teachings of the present invention described above. The processor  2020  may be implemented using one or more processors, WLAN components, WMAN components, WWAN components, and/or other suitable processing components. For example, the processor  2020  may be implemented using one or more of the Intel® Pentium® technology, the Intel® Itanium® technology, the Intel® Centrino™ technology, the Intel® Xeon™ technology, and/or the Intel® XScale® technology. In the alternative, other processing technology may be used to implement the processor  2020 . The processor  2020  may include a cache  2022 , which may be implemented using a first-level unified cache (L1), a second-level unified cache (L2), a third-level unified cache (L3), and/or any other suitable structures to store data. 
     The memory controller  2012  may perform functions that enable the processor  2020  to access and communicate with a main memory  2030  including a volatile memory  2032  and a non-volatile memory  2034  via a bus  2040 . The volatile memory  2032  may be implemented by Synchronous Dynamic Random Access Memory (SDRAM), Dynamic Random Access Memory (DRAM), RAMBUS Dynamic Random Access Memory (RDRAM), and/or any other type of random access memory device. The non-volatile memory  2034  may be implemented using flash memory, Read Only Memory (ROM), Electrically Erasable Programmable Read Only Memory (EEPROM), and/or any other desired type of memory device. 
     The processor system  2000  may also include an interface circuit  2050  that is coupled to the bus  2040 . The interface circuit  2050  may be implemented using any type of interface standard such as an Ethernet interface, a universal serial bus (USB), a third generation input/output interface (3GIO) interface, and/or any other suitable type of interface. In various embodiments, interface circuit  2050  may be endowed with all or portions of the teachings of the present invention described above. 
     One or more input devices  2060  may be connected to the interface circuit  2050 . The input device(s)  2060  permit an individual to enter data and commands into the processor  2020 . For example, the input device(s)  2060  may be implemented by a keyboard, a mouse, a touch-sensitive display, a track pad, a track ball, an isopoint, and/or a voice recognition system. 
     One or more output devices  2070  may also be connected to the interface circuit  2050 . For example, the output device(s)  2070  may be implemented by display devices (e.g., a light emitting display (LED), a liquid crystal display (LCD), a cathode ray tube (CRT) display, a printer and/or speakers). The interface circuit  2050  may include, among other things, a graphics driver card. 
     The processor system  2000  may also include one or more mass storage devices  2080  to store software and data. Examples of such mass storage device(s)  2080  include floppy disks and drives, hard disk drives, compact disks and drives, and digital versatile disks (DVD) and drives. 
     The interface circuit  2050  may also include a communication device such as a modem or a network interface card to facilitate exchange of data with external computers via a network. The communication link between the processor system  2000  and the network may be any type of network connection such as an Ethernet connection, a digital subscriber line (DSL), a telephone line, a cellular telephone system, a coaxial cable, etc. 
     Access to the input device(s)  2060 , the output device(s)  2070 , the mass storage device(s)  2080  and/or the network may be controlled by the I/O controller  2014 . In particular, the I/O controller  2014  may perform functions that enable the processor  2020  to communicate with the input device(s)  2060 , the output device(s)  2070 , the mass storage device(s)  2080  and/or the network via the bus  2040  and the interface circuit  2050 . 
     While the components shown in  FIG. 9  are depicted as separate blocks within the processor system  2000 , the functions performed by some of these blocks may be integrated within a single semiconductor circuit or may be implemented using two or more separate integrated circuits. For example, although the memory controller  2012  and the I/O controller  2014  are depicted as separate blocks within the chipset  2010 , the memory controller  2012  and the I/O controller  2014  may be integrated within a single semiconductor circuit. 
     Although certain embodiments have been illustrated and described herein for purposes of description of the preferred embodiment, it will be appreciated by those of ordinary skill in the art that a wide variety of alternate and/or equivalent embodiments or implementations calculated to achieve the same purposes may be substituted for the embodiments shown and described without departing from the scope of the present invention. Those with skill in the art will readily appreciate that embodiments in accordance with the present invention may be implemented in a very wide variety of ways. This application is intended to cover any adaptations or variations of the embodiments discussed herein. Therefore, it is manifestly intended that embodiments in accordance with the present invention be limited only by the claims and the equivalents thereof.