Patent Publication Number: US-7917116-B2

Title: Method and system for antenna selection diversity with prediction

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS/INCORPORATION BY REFERENCE 
     This application is a continuation of U.S. application Ser. No. 10/810,433 filed Mar. 26, 2004. 
     This application makes reference to, claims priority to, and claims the benefit of U.S. Provisional Application Ser. No. 60/547,362 filed Feb. 24, 2004. 
     This application makes reference to: 
     U.S. patent application Ser. No. 10/810,462 filed Mar. 26, 2004; 
     U.S. patent application Ser. No. 10/810,186 filed Mar. 26, 2004; and 
     U.S. patent application Ser. No. 10/810,408 filed Mar. 26, 2004. 
     The above stated applications are hereby incorporated herein by reference in their entirety. 
    
    
     FIELD OF THE INVENTION 
     Certain embodiments of the invention relate to wireless communication. More specifically, certain embodiments of the invention relate to a method and system for antenna selection diversity with prediction. 
     BACKGROUND OF THE INVENTION 
     In a wireless communication system, a data stream will most likely experience multiple reflections (multipath) while propagating between the transmitter and the receiver. Multipath fading implies that multiple copies of the transmitted signal follow different paths and reach the receiving antenna with different time delays. In such cases the received signal strength at a given time is the result of destructive and constructive interference of the multiple paths arriving from different directions. Destructive interference degrades the performance of the detector and hence adversely affects the system capacity. However, by using multiple antennas at the receiver and with appropriate digital signal processing methods, multipath can be exploited to enhance the performance and robustness of the receiver and to increase the reliability of the communications link. The receiving antennas generally must be spaced sufficiently far apart that the signal each antenna sees is not correlated with the signals seen by the other antennas. One such method of mitigating multipath fading is called selection diversity. 
     Selection diversity is based on selecting the best signal among plurality of signals detected at the receiver antennas. Let P i  denote the power estimated at antenna i at the receiver. Then, the selection diversity scheme will select antenna j as the receive antenna if P j &gt;P i , i≠j. Higher accuracy in estimating the powers P i  results in higher probability of the right receive antenna being selected and better performance of the selection diversity scheme. Two main factors that affect the accuracy of the power estimates P i  may include a dwell time on all antennas other than the starting antenna and presence of impairments such as noise, transients and offsets. 
     With regard to dwell time on all antennas other than the starting antenna, in practical wireless communications systems, time constraints are imposed to keep the transmission overhead low. As a result, the dwell time on all antennas other than the starting antenna is insufficient to allow for automatic gain control (AGC) to run its full course during the dwell time on each antenna. Without automatic gain control, the visibility of the signal strength of all antennas other than the starting antenna is limited and generally leads to inaccurate power estimates P i . 
     With regard to the presence of impairments such as noise, transients and offsets, impairments corrupt the power estimates P i  and may result in mis-estimations of the received power. Such mis-estimations of power may result in the selection of antenna j as the receive antenna even if P j &lt;P i  for some other antenna i. Because dwell time on all antennas other than the starting antenna is limited, a predetermined gain may be generally applied to all antennas other than the starting antenna. When the signal in antenna j, where antenna j is not the starting antenna, is very strong, the predetermined gain applied to antenna j may be too high for that signal and the signal may be clipped. If the clipped signal in antenna j was in fact the best received signal available to the receiver, the receiver may end up selecting a signal from antenna i, where P i &lt;P j , because it may not be able to estimate accurately the power of a signal when it is clipped. 
     In general, the power estimate of the starting antenna is generally more reliable than those of the other antennas because carrier detection and full AGC are performed on the starting antenna. This leaves insufficient time for running a full AGC on the other antennas. Although there are ways to improve the accuracy of the power estimates of antennas other than the starting antenna, the selection diversity scheme will perform considerably better and more effectively if the starting antenna happens to be the antenna with the highest signal power. 
     Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present invention as set forth in the remainder of the present application with reference to the drawings. 
     BRIEF SUMMARY OF THE INVENTION 
     Certain embodiments of the invention may be found in a method and system for antenna selection diversity with prediction. Selection diversity in systems with multiple antennas works best when the set of starting antennas may be the best antennas for signal detection and signal decoding. Certain aspects of the method for antenna selection diversity with prediction may comprise collecting information that may be associated with at least one of the previous received frames and determining at least one starting receiving antenna for the next frame based on the collected information. The collected information may correspond to the performance of at least one of the antennas in the receiver system. The collected information may be one of several selection metrics that measure the performance of the antennas during a frame. The selection metrics may be, for example, a power estimation, a signal-to-noise ratio, a packet error rate or bit error rate, a propagation channel characteristic, and/or a channel interference level. Selection of the starting receiving antenna may be based on at least one of these selection metrics. The number of collected frames that may be utilized for antenna prediction may be predetermined or may be updated after each new starting antenna is selected. 
     Antenna prediction may be based on collected information regarding or pertaining to which antennas may have been selected in previous frames as the best antenna for signal detection and decoding. A majority polling scheme may be used to predict the next starting antenna by selecting at least one antenna that has been previously the best antenna for signal detection and signal decoding in a specified number of frames. A threshold regarding or pertaining to what constitutes majority in majority polling may be predetermined or may be varied based on the number of previous frames under consideration. The threshold for what constitutes majority in majority polling may be updated if the number of antennas in a determined number of frames does not meet the specified threshold. 
     Antenna prediction may be based on collected information regarding or pertaining which antennas may have had a better overall performance in at least one selection metric over a predetermined number of frames. Determining the best overall performance may be based on a weighted sum scheme of at least a portion of the stored information. The weighted sum scheme may correspond to a filtering approach, where the overall performance of an antenna may be based on an estimated selection metric or on an received selection metric in the antenna over a predetermined number of frames. The response of the weighted sum scheme may also correspond to the response of a first-order infinite impulse response (IIR) filter or to that of a finite impulse response (FIR) filter depending on the constraints 
     Antenna selection diversity with prediction may also comprise selecting at least one starting transmit antenna from a set of transmitter antennas. Selection may be based on selection metrics, for example, a power estimation, a signal-to-noise ratio, a packet error rate or bit error rate, a propagation channel characteristic, and/or a channel interference level. Transmission antenna prediction may provide efficiency and speed improvements by reducing transmission processing overhead and by improving signal detection which in turn improves receiving antenna prediction. 
     Another embodiment of the invention may provide a machine-readable storage, having stored thereon, a computer program having at least one code section executable by a machine, thereby causing the machine to perform the steps as described above for antenna selection diversity with prediction. 
     Aspects of the system for antenna selection diversity with prediction may comprise a processor that collects information that may be associated with at least one of the previous transmission frames and that determines at least one starting receive antenna for the next frame based on the collected information. The collected information may be stored in memory and may correspond to the performance of at least one of the antennas in the receiver system. The collected information may be one of several selection metrics that measure the performance of the antennas during a frame. The selection metrics may be, for example, a power estimation, a signal-to-noise ratio, a packet error rate or bit error rate, a propagation channel characteristic, and/or a channel interference. The processor may select the starting receiving antenna based on at least one of these selection metrics. The processor may determine the number of collected frames that may be utilized for antenna prediction or may update the number after each new starting antenna is selected. 
     The processor may base antenna prediction on collected information of which set of antennas may have been selected in previous frames as the best set of antennas for signal detection and decoding. The processor may use a majority polling scheme to predict the next starting antenna by selecting at least one antenna that has been the best antenna for signal detection and signal decoding in a specified number of frames. A threshold may be predetermined regarding or pertaining to what constitutes majority in majority polling or it may vary the threshold based on the number of previous frames under consideration. The threshold for what constitutes majority in majority polling if the number of antennas in a determined number of frames does not meet the specified threshold. 
     Antenna prediction may be based on collected information of which antennas may have had a better overall performance in at least one selection metric over a predetermined number of frames. The best overall performance may be determined by the processor based on a weighted sum scheme of at least a portion of the stored information. The processor may select a filtering approach that corresponds to a weighted sum scheme, where the overall performance of an antenna may be based on an estimated selection metric and/or a received selection metric over a predetermined number of frames. The response of the weighted sum scheme may correspond to the response of a first-order infinite impulse response (IIR) filter or to that of a finite impulse response (FIR) filter depending on the constraints. 
     The processor may also select at least one starting transmit antenna from a set of transmitter antennas. Selection may be based on selection metrics, for example, a power estimation, a signal-to-noise ratio, a packet error rate or bit error rate, a propagation channel characteristic, and/or a channel interference. Transmission antenna prediction may provide efficiency and speed improvements by reducing transmission processing overhead and by improving signal detection which in turn improves receiving antenna prediction. 
     These and other advantages, aspects and novel features of the present invention, as well as details of an illustrated embodiment thereof, will be more fully understood from the following description and drawings. 
    
    
     
       BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1A  is a diagram of an exemplary receiver system that may be utilized in connection with selection diversity with prediction, in accordance with an embodiment of the invention. 
         FIG. 1B  is a diagram of an exemplary transmitter system and receiver system that may be utilized in connection with selection diversity with prediction, in accordance with an embodiment of the invention. 
         FIG. 2  is a flow diagram that illustrates exemplary steps that may be used by a receiver system to predict the next starting antenna based on a majority polling scheme, in accordance with an embodiment of the invention. 
         FIG. 3  illustrates an example of threshold levels that may be used by a receiver system to arbitrarily or adaptively predict the next starting antenna, in accordance with an embodiment of the invention. 
         FIG. 4  is a flow diagram that illustrates exemplary steps that may be used by a receiver system to predict the next starting antenna based on a weighted sum scheme, in accordance with an embodiment of the invention. 
         FIG. 5  is a flow diagram that illustrates exemplary steps that may be used by a receiver system to predict the next transmission antenna, in accordance with an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Certain embodiments of the invention may be found in a method and system for antenna selection diversity with prediction. Wireless communication systems may utilize receivers with multiple antennas to enhance the performance and robustness of the receiver and to increase the reliability of the communications link. Selection diversity in systems with multiple antennas works best when the set of starting antennas may be the best antennas for signal detection and signal decoding. Certain aspects of the method for antenna selection diversity with prediction may comprise collecting information that may be associated with at least one of the previous received frames and determining at least one starting receiving antenna for the next frame based on the collected information. The collected information may correspond to the performance of at least one of the antennas in the receiver system. The collected information may be one of several selection metrics that measure the performance of the antennas during a frame. The selection metrics may be, for example, a power estimation, a signal-to-noise ratio, a packet error rate or bit error rate, a propagation channel characteristic, and/or a channel interference level. Selection of the starting receiving antenna may be based on at least one of these selection metrics. The number of collected frames that may be utilized for antenna prediction may be predetermined or may be updated after each new starting antenna is selected. 
       FIG. 1  is a diagram of an exemplary receiver system that may be utilized in connection with selection diversity with prediction, in accordance with an embodiment of the invention. Referring to  FIG. 1 , the receiver system  100  may comprise at least one antenna  102 , an antenna switch  104 , a processor  106 , and a memory  108 . There may be as many as M antennas  102  coupled to the antenna switch  104 . The antenna  102  may be part of an independent antenna array of antennas coupled to the antenna switch  104 , may be one of several individual antennas coupled to the antenna switch  104 , and/or may be one of several integrated individual antennas and/or may be part of an integrated array of antennas coupled to the antenna switch  104 . The antenna switch  104  may be a mechanical, electronic, electromechanical, and/or micro-electromechanical (MEM) switch. The processor  102  may be, for example, a hardware resource, a core processor, a coprocessor, a digital signal processor, or a microcontroller. The memory  108  may be an external memory, an embedded memory, a shared memory, or a main memory. The memory  108  may be, for example, an SRAM and/or DRAM type memory. 
     The incoming wireless signal may be received by at least one antenna  102  in receiver system  100 . The antenna switch  104  may select the antenna channel of any antenna  102 . The processor  106  may notify the antenna switch  104  regarding which antenna channel corresponding to a particular antenna  102  to select. The processor  106  may be utilized to determine which antenna  102  may be the starting antenna, to determine which antenna  102  to select next, to determine the dwell time in each selected antenna, to detect and decode the incoming signal, and to amplify or apply a gain to the signal. The processor  106  may be adapted to apply gain to the signal from an antenna channel by utilizing an automatic gain control (AGC) or by determining a specific gain to apply. The processor  106  may be used to determine the estimated power of the signal, to determine a signal-to-noise ratio, to determine a packet-error-rate or bit-error-rate, to transfer information to and from memory  108 , and to determine statistics based on information collected from several transmitted frames stored in memory  108 . The memory  108  may be utilized to store information collected and processed by the processor  106  that may be associated with any antenna  102  in any number of transmitted frames. 
     In operation, the processor  106  may notify the antenna switch  104  which antenna  102  may be used as the starting antenna. The processor  106  may determine which antenna  102  to use for the starting antenna based on information from preceding frames that may be stored in memory  108 . The antenna switch  104  may select the antenna channel that corresponds to the selected antenna  102 . The processor  106  may dwell on the starting antenna until it detects an incoming signal. Once the signal is detected, an AGC may be applied to obtain a sufficiently strong signal for decoding. The processor  106  may determine the estimated received power for the starting antenna and may store the value in memory  108 . The processor  106  may then notify the antenna switch  104  to select the next antenna  102  for detection. The processor  106  may determine which antenna  102  to use as the next antenna based on information from preceding frames that may be stored in memory  108 . The antenna switch  104  may select the antenna channel that corresponds to the next antenna. The processor  106  may dwell on the next antenna and apply a predetermined gain because the dwell time may be insufficient for an AGC to run its full operation. The processor  106  may determine the estimated received power for the next antenna and may store the value in memory  108 . A similar procedure may be carried out with the remaining antennas in receiver system  100 . With the exception of the starting antenna, a predetermined gain may be applied to all the other antennas because dwell time in all but the starting antenna may be limited. The processor  106  may determine an estimated received power for all antennas in receiver system  100  and store the values in memory  108 . The processor  106  may select the best antenna for decoding by selecting the highest estimated received power to determine which of the antenna  102  which has the strongest signal. The processor  106  may then notify the antenna switch  104  to select the antenna channel that corresponds to the antenna with the strongest signal for decoding. The processor  106  may then detect and decode the signal from the selected best antenna and may store information associated with the antenna it selected as the best antenna for the current frame. 
       FIG. 1B  is a diagram of an exemplary transmitter system and receiver system that may be utilized in connection with selection diversity with prediction, in accordance with an embodiment of the invention. Referring to  FIG. 1B , a general transmission (TX) system  120  and a general receiver (RX) system  110  may be used for communicating between two locations. The TX system  120  may have as many as N TX antennas  112  coupled to it and the RX system  110  may have as many of M antennas  102  coupled to it. The TX antennas  112  may be part of an independent antenna array of antennas, may be one of several individual antennas, and/or may be one of several integrated individual antennas and/or may be part of an integrated array of antennas. The TX antennas  112  may be broadcasting antennas or may be directional antennas. 
     In operation, the TX system  120  may select one of the TX antennas  112  to send the first frame of information. The TX antenna  112  selected for the first frame may then transmit the frame for the RX system  110  to receive. The RX system  110  may select the best antenna  102  for receiving the first frame from the TX system  120 . The TX system  120  may select a new TX antenna  112  to send the second frame of information. The RX system  110  may detect the second frame by selecting a different best antenna  102  than it did for the first frame. After several frames of information are sent and received, the RX system  110  may have collected sufficient information to determine that when a frame of information is sent from a particular TX antenna  112 , the RX system  110  receives the best metric from at least one of the selection metrics. The RX system  110  may also determine when a frame is sent from a particular TX antenna  112 , the selection diversity may take less time to carry out because the best selection metric is concentrated among a group of antennas  102 . In these instances, the RX system  110  may provide the TX system with this frame so that the TX system  120  may select only the TX antennas  112  that provide the best selection metric or provide the most rapid and efficient detection in RX system  110 . This also has the effect of increasing the speed of transmission since the TX system  120  may not need to spend the processing overhead to determine the next antenna for transmission and the RX system  110  may be able to predict the best antenna for signal detection. 
       FIG. 2  is a flow diagram that illustrates exemplary steps that may be used by a receiver system to predict the next starting antenna based on a majority polling scheme, in accordance with an embodiment of the invention. Referring to  FIG. 2 , the flow chart  200  starts by selecting a set of at least one starting antenna in step  202 . If more than one receive path is available then the processor  106  may select more than one starting antenna in step  202 . In step  204 , the processor  106  may select the number N of preceding frames to utilize for determining the next starting antenna. The information on the preceding frames may have been collected by processor  106  and stored in memory  108 . In step  206 , the processor  106  may transfer from memory  108  information associated with the antennas which may have been chosen as the best antenna for signal detection and signal decoding over the N previous frames. The selection of best antenna for signal detection and signal decoding may be based on the antenna with the highest estimated received power in a particular frame. In step  208 , the processor  106  may count the number of times in the previous N frames that an antenna may have been selected as the best antenna. In step  210 , the processor  106  may determine the threshold level K that may be needed to select an antenna as the starting antenna for the next frame. The threshold level K may be predetermined based on the number N of frames that may be utilized in determining the next starting antenna. The threshold level K may be dynamically updated based on collected information. 
     In step  212 , the processor  106  may determine whether any of the antennas selected as best antenna over the previous N frames meets or exceeds the threshold level K. If one antenna meets or exceeds the threshold level K, then the processor  106  may proceed to step  214 . If more than one antenna meets or exceeds the threshold level K, then the processor  106  may return to step  210  and update the threshold level K to provide a majority result. If no antenna meets or exceeds the threshold level K, then the processor  106  may return to step  210  and update the threshold level K to provide a majority result. If at least one antenna meets or exceeds the threshold in step  212 , then the processor may proceed to step  214 . In step  214 , the processor  106  may select as the next starting antenna one of the antennas which may have either met or exceeded the threshold level in step  212 . The processor  106  may select several of the antennas which may have either met or exceeded the threshold level in step  212  and use a selection metric to determine which one to use. The selection metric may be, for example, an estimated received power, a received power, a signal-to-noise ratio, a bit error rate, a packet error rate, a propagation channel characteristic, and/or a channel interference. 
     For example, a receiver system  100  may have antenna prediction based on a majority polling scheme and may select antenna j as the starting antenna of the next frame if antenna j is chosen as the best receive antenna K times in the N previous frames. This may be denoted as K-out-of-N starting antenna selection scheme. For example, if N is odd and K=(N+1)/2, then the K-out-of-N starting antenna selection scheme is that of an absolute majority polling. The number of N previous frames may be even or odd. The choices of N and K may be predetermined or they may be updated by the processor  106  based on the number of frames N and the count of selected antennas in step  208 . 
     The greater the value of parameter N, the greater the number of previous frames used and the less likely that the chosen starting antenna will change from frame to frame. However, the greater the value of parameter N, the longer it will take to activate the selection scheme. A K-out-of-N starting antenna selection scheme generally comes into effect on frame N+1 even though it may start as early as frame K+1. Before the K-out-of-N starting antenna selection scheme kicks in, the starting antenna may be chosen arbitrarily or adaptively. 
       FIG. 3  illustrates an example of threshold levels that may be used by a receiver system to arbitrarily or adaptively predict the next starting antenna, in accordance with an embodiment of the invention. Referring to  FIG. 3 , in this exemplary illustration the receiver system  100  may implement a majority polling scheme where N=7 and K=4 for the case when K=(N+1)/2. A possible adaptive scheme that may used before reaching the eighth frame is a K n -out-of-n selection scheme, where n is the frame number and K n  is arbitrarily or adaptively chosen. In this example, the receiver system  100  may have two antennas and the starting antenna may be arbitrarily chosen. In the second frame and third frames, the selection scheme may be a 1-out-of-1 scheme. In the fourth and fifth frames, a 2-out-of-3 selection scheme may be used. In the sixth and seventh frames, a 3-out-of-5 selection scheme may be used. By the eighth frame there may be sufficient previous frames to implement a K-out-of-N scheme where N=7 and K=4. 
       FIG. 4  is a flow diagram that illustrates exemplary steps that may be used by a receiver system to predict the next starting antenna based on a weighted sum scheme, in accordance with an embodiment of the invention. Referring to  FIG. 4 , the flow chart  400  in step  402  may determine a set of starting antennas. If more than one receive path exists the processor  106  may select more than one starting antenna in step  402 . In step  404  the processor  106  may select the number of frames N that may be used for prediction. The information on the preceding frames may have been collected by processor  106  and stored in memory  108 . Once the number of frames for prediction is determined, the processor  106  may determine in step  406  which selection metric it may use in predicting the next starting antenna. The selection metrics may be, for example, the received power, the signal-to-noise ratio, and/or the packet error rate or bit error rate. In step  408 , the processor  106  may determine whether the selection metric is the received power or a different selection metric. In step  408 , the processor may also be configured to select more than one selection metric for antenna selection. If one of the selected selection metrics is a selection metric other than the received power, then the processor  106  may proceed to step  418 . In step  418 , the processor  106  may select an appropriate filtering format that may be used to determine the best overall antenna over the previous N frames based on the selection metric chosen. In step  420 , the processor  106  may determine the appropriate weighting factors for that filtering format chosen in step  418 . In step  422 , the processor  106  may determine the filtered value for the selection metric chosen and in step  424  the processor  106  may select the next starting antenna based on the results from the filtering in step  422 . Filtering may be applied to any selection metric. 
     If the selection metric chosen in step  408  was the received power, the processor  106  may select a received power filtering format that may be used for determining the next starting antenna. For example, when the selection metrics used may correspond to the estimated and the received power, a sample filtering format that may be used is a first-order infinite impulse response (IIR) filter Q i (n)=P i (n)+a 1 Q i (n−1), where P i (n) represent the power estimate of antenna i for frame n and Q i (n) is the filtered version of P i (n). Another filtering format that may be used is a 3-tap moving average or finite impulse response (FIR) filter 
                 Q   i     ⁡     (   n   )       =       ∑     k   =   0     2     ⁢       1   3     ⁢         P   i     ⁡     (     n   -   k     )       .               
A general expression of a filtering format may be
 
                     Q   i     ⁡     (   n   )       -         ∑   N       k   =   1       ⁢       a   k     ⁢       Q   i     ⁡     (     n   -   k     )             =       ∑     k   =   0     M     ⁢       b   k     ⁢       P   i     ⁡     (     n   -   k     )             ,         
where the weighting factors a k , b k , N, and M may be chosen to provide the desired filtering.
 
     In step  412 , the processor  106  may chose the he weighting factors a k , b k , N, and M based on the filtering format selected in step  410 . In step  412 , the processor  106  may determine the filtered received power based on the filtering format and the number of preceding frames being used for prediction. In step  416 , the processor  106  may select the next starting antenna or a group of possible next starting antennas based on the antenna with the maximum Q i (n). 
     To boost the performance and robustness of the selection diversity scheme, the starting antenna may be the antenna that may most likely be chosen for processing. In a stationary environment, the starting antenna for the current frame may often be correctly predicted by using collected information from previous frames. This collected information may be either the selection metrics such as power estimates of all antennas or they may be which antennas were chosen for reception over the last N frames. 
       FIG. 5  is a flow diagram that illustrates exemplary steps that may be used by a receiver system to predict the next transmission antenna, in accordance with an embodiment of the invention. Referring to  FIG. 5 , in flow diagram  500  after start step  502 , the TX system  120  may be used in step  504  to transmit a frame of information to the RX system  110 . The TX system  120  may have a schedule where it sends consecutive frames of information from different TX antennas  112  in a predetermined manner. In step  506 , the RX system  110  receives the signal and may perform antenna selection diversity to determine the antenna  102  or group of antennas  102  that it may use for signal detection. In step  508 , the RX system  110  may collect information on the selection metrics of antennas  102  and the TX antenna  112  that may be the source of the transmitted frame. The collected information may correspond to a specified number of frames and may be stored in memory  108 . 
     In step  510 , the RX system  110  may use the collected information to determine whether antenna selection diversity may be used in either the TX system  120  and/or the RX system  110 . If antenna selection diversity may be used, the RX system  110  may predict in step  512  which antenna  102  or group of antennas  102  to use for frame detection in the next transmitted frame. The antenna selection diversity may be based on selection metrics, for example, an estimated received power, a received power, a signal-to-noise ration, a bit error rate, a packet error rate, a propagation channel characteristic, an/or a channel interference. The RX system  110  may also use selection diversity to predict which TX antenna  112  or group of TX antennas  112  to use for frame transmission because their reception is stronger than that of other TX antennas  112 . The RX system  110  may recommend the TX system  120  as to the best TX antenna  112  or group of TX antennas  112  to use for transmission of the next frame. The RX system  110  may transfer the collected information or a portion of the collected information to the TX system  120  in order for it to determine which TX antenna or group of TX antennas  112  to use for transmission of the next frame. If antenna selection diversity may not be used in step  510 , then the RX system  110  and the TX system  120  may select in step  514  their next scheduled starting receive and transmit antennas respectively. After steps  512  and  514  the TX system  120  prepares a new frame for transmission from either a predicted TX antenna  112  or from the next scheduled TX antenna  112  respectively. 
     Accordingly, the present invention may be realized in hardware, software, or a combination of hardware and software. The present invention may be realized in a centralized fashion in at least one computer system, or in a distributed fashion where different elements are spread across several interconnected computer systems. Any kind of computer system or other apparatus adapted for carrying out the methods described herein is suited. A typical combination of hardware and software may be a general-purpose computer system with a computer program that, when being loaded and executed, controls the computer system such that it carries out the methods described herein. 
     The present invention may also be embedded in a computer program product, which comprises all the features enabling the implementation of the methods described herein, and which when loaded in a computer system is able to carry out these methods. Computer program in the present context means any expression, in any language, code or notation, of a set of instructions intended to cause a system having an information processing capability to perform a particular function either directly or after either or both of the following: a) conversion to another language, code or notation; b) reproduction in a different material form. 
     While the present invention has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the present invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present invention without departing from its scope. Therefore, it is intended that the present invention not be limited to the particular embodiment disclosed, but that the present invention will include all embodiments falling within the scope of the appended claims.