Abstract:
A wireless network device comprises at least two antennas that transmit and receive data packets. An antenna diversity module measures at least one of an average signal to noise ratio (SNR) and an error rate of said data packets during at least one of transmitting and receiving N packets, where N is an integer greater than one, and selects one of said at least two antennas based on said at least one of said average SNR and said error rate.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 60/724,972, filed on Oct. 7, 2005. The disclosure of the above application is incorporated herein by reference in its entirety. 
    
    
     FIELD 
     The present invention relates to antenna diversity systems, and more particularly to an antenna utilization control method for use in diversity antenna systems. 
     BACKGROUND 
     Wireless network devices with antenna diversity are employed to reduce signal fading in wireless communication applications. These wireless network device include two or more antennas. One of the antennas is employed to transmit and receive packets at a time. Signal to noise ratio (SNR) of each antenna is measured during a preamble of a packet and the antenna is selected. 
     Referring now to  FIG. 1 , a wireless network device  10  including hardware-based antenna diversity is shown. The wireless network device  10  typically includes a host device  12  such as a laptop, personal digital assistant, desktop computer or other computing device. The host device  12  includes a wireless network interface  13 . The wireless network interface  13  communicates with another wireless network device  14  having an antenna system  16 . The wireless network interface  13  may include a physical layer (PHY) module  20  that provides an interface between a medium access control (MAC) module  24  and a wireless medium. A host interface module  26  may provide an interface between the MAC module  24  and the host device  12 . A hardware-based antenna diversity module  28  selects between a first antenna A 1  and a second antenna A 2  based on measurements made when packets are received. 
     Referring now to  FIG. 2 , the wireless network device  14  exchanges packets  50  with the wireless network interface  13 . The packets  50  may include a preamble portion  54 , a header portion  56 , a variable length user data portion  58  and an error checking portion  60 . The hardware-based antenna diversity module  28  samples a SNR of the preamble portion  54  and selects one of the antennas A 1  or A 2 . More particularly, the hardware-based antenna diversity module  28  samples SNR of the first antenna during a first half of the preamble portion  54  of the packet  50 . During a second half of the preamble portion  54 , the hardware-based antenna diversity module  28  samples SNR of the second antenna. Based on the SNR sampling, the hardware-based antenna diversity module selects one of the antennas to be used for the packet. 
     SUMMARY 
     A wireless network device comprises at least two antennas that transmit and receive data packets. An antenna diversity module measures at least one of an average signal to noise ratio (SNR) and an error rate of said data packets during at least one of transmitting and receiving N packets, where N is an integer greater than one, and selects one of said at least two antennas based on said at least one of said average SNR and said error rate. 
     In still other features, the systems and methods described above are implemented by a computer program executed by one or more processors. The computer program can reside on a computer readable medium such as but not limited to memory, non-volatile data storage and/or other suitable tangible storage mediums. 
     Further areas of applicability of the present disclosure will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the disclosure, are intended for purposes of illustration only and are not intended to limit the scope of the disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a functional block diagram of a wireless network device including a hardware based antenna diversity module according to the prior art; 
         FIG. 2  illustrates sampling of SNR of the preamble to determine antenna selection according to the prior art; 
         FIG. 3A  is a functional block diagram of an exemplary wireless network device including an antenna diversity module according to the present disclosure; 
         FIG. 3B  is a functional block diagram of an exemplary wireless network device including an antenna diversity module according to the present disclosure; 
         FIG. 3C  is a more detailed functional block diagram of an exemplary antenna diversity module; 
         FIGS. 4A and 4B  are flowcharts illustrating operation of the diversity modules of  FIGS. 3A and 3B ; 
         FIG. 5A  is a functional block diagram of a high definition television; 
         FIG. 5B  is a functional block diagram of a vehicle control system; 
         FIG. 5C  is a functional block diagram of a cellular phone; 
         FIG. 5D  is a functional block diagram of a set top box; and 
         FIG. 5E  is a functional block diagram of a media player. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is in no way intended to limit the disclosure, its application, or uses. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. As used herein, the term module, circuit and/or device refers to an Application Specific Integrated Circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A or B or C), using a non-exclusive logical or. It should be understood that steps within a method may be executed in different order without altering the principles of the present disclosure. 
     The approach used by the hardware-based antenna diversity module  28  in  FIG. 1  has several drawbacks. The approach is based upon sampling during the receipt of packets. In other words, there is no information as to whether the selected antenna is the best antenna for transmitting packets. In addition, sampling during one half of the preamble portion may be an interval this is too short to make an informed decision when particular signals such as orthogonal frequency division multiplexing (OFDM) signals are received. 
     Referring now to  FIGS. 3A and 3B , wireless network devices including an antenna diversity module according to the present disclosure are shown. In  FIG. 3A , a wireless network device  110  typically includes a host device  112  such as a laptop, personal digital assistant, desktop or other computing device. The host device  112  includes a wireless network interface  113 . The wireless network interface  113  communicates with another wireless network device  14  having an antenna system  16 . 
     The wireless network device  113  includes a physical layer (PHY) module  120  that provides an interface between a medium access control (MAC) module  124  and a wireless medium. A host interface module  126  provides an interface between the MAC module  124  and the host device  112 . An antenna diversity module  128  may be associated with the physical layer device  120  and may select between two or more antennas. In  FIG. 3A , the antenna diversity module  128  selects between a first antenna A 1  and a second antenna A 2 . In  FIG. 3B , the antenna diversity module  128  may be associated with the MAC module  120  and may select between a first antenna A 1  and a second antenna A 2 . The antenna diversity module  128  may be associated with other components of the wireless network interface  113 . 
     Referring now to  FIG. 3C , the antenna diversity module  128  is shown. The antenna diversity module  128  includes an error rate module  150  that determines an error rate during transmission of packets from the wireless network interface  113  to the wireless network device  14 . The error rate may be a packet error rate (PER), a bit error rate (BER), a symbol error rate (SER), and/or any other suitable error rate. A signal-to-noise ratio (SNR) module  152  determines a SNR of signals received by the wireless network interface  113 . A timing module  156  generates timing signals to identify one or more predetermined periods. An antenna selection module  160  receives the error rate estimate, the SNR estimate and the predetermined periods and selects an antenna to be used. The antenna diversity module  122  bases the antenna selection decision on the error rate estimate and/or the SNR of multiple packets as will be described further below. 
     Referring now to  FIGS. 4A and 4B , operation of the antenna diversity module of  FIGS. 3A and 3B  is illustrated. Control begins with step  200  and proceeds to step  204  where a timer is started. When the timer is up as determined in step  206 , a packet is received in step  210 . In step  212 , control determines whether the antenna state is equal to steady. If true, control continues with step  218  determines whether a first timer (Timer 1 ) is greater than a first period T 1  or |SNR avg −SNR past |≧SNR abs . SNR avg  is an average SNR. SNR past  is a prior stored value. SNR abs  is an SNR difference threshold. If step  218  is false, control returns to step  204 . If step  218  is true, control continues with step  220  and sets AntState=Tx_Ant_Eval — 1, RSSI Avg =0 and Timer 1 =0. RSSI is a received signal strength indicator. After step  220 , control returns to step  204 . 
     When step  212  is false, control continues with step  224  and determines whether the antenna state is equal to Tx_Ant_Eval — 1. If step  224  is true, control continues with step  228  and determines whether (Tx mode is true and tx&gt;P 1  (a predetermined number of packets have been sent)) or (Rx mode is true and recvd&gt;P 2  (received number of packets) and time spent&lt;T 2 ). If step  228  is false, control sets the antenna state is equal to Tx_Ant_Eval — 1 and control returns to step  204 . 
     When step  228  is true, control swaps antennas, sets AntState=Tx_Ant_Eval — 2, PER past =PER, SNR past =SNR avg , SNR avg =0 and resets PER parameters. After step  228 , control returns to step  212 . When step  224  is false, control continues with step  240  and determines whether the antenna state is equal to Tx_Ant_Eval — 2. If false, an error occurs, the antenna state is set equal to steady and control returns to step  204 . When step  240  is true, control continues with step  248  and determines whether (Tx mode and tx&gt;P 1 ) or (Rx mode and recvd&gt;P 2  and time spent&lt;T 2 ). If step  248  is false, control continues with step  252  and sets the antenna state equal to Tx_Ant_Eval — 2. Control continues from step  252  with step  204 . 
     When step  248  is true, control determines whether data is available to calculate the SNR and PER. If step  256  is true, control continues with step  260  and determines whether SNR avg &gt;SNR past +SNR th . If step  260  is true, control continues with step  264  and sets PER past =PER and RSSI past =SNR avg . Control continues from step  264  with step  268  where the antenna state is set equal to steady and control returns to step  204 . 
     When step  256  is false, control continues with step  276  and swaps back antennas. When step  260  is false, control determines whether PER past &gt;PER+PER th  in step  272 . If true, control continues with step  264  described above. If step  272  is false, control swaps back antennas in step  276 . Control continues from steps  264  and  276  with step  268 . 
     As an example, the timer may have a period of 5 seconds. The value of P 1  can be set equal to 100 packets. The value of P 2  may be set equal to 15 packets. The value of T 2  may be set equal to 200 milliseconds. The SNR th  may be set equal to 4 dB. The SNR abs  may be set equal to 4 dB. 
     The wireless network device can be compliant with IEEE standards 802.11, 802.11a, 802.11b, 802.11g, 802.11h, 802.11n, 802.16, 802.20, Bluetooth, and/or other suitable standards. 
     Referring now to  FIG. 5A , the device can be implemented in a wireless network interface of a high definition television (HDTV)  420 . The HDTV  420  receives HDTV input signals in either a wired or wireless format and generates HDTV output signals for a display  426 . In some implementations, signal processing circuit and/or control circuit  422  and/or other circuits (not shown) of the HDTV  420  may process data, perform coding and/or encryption, perform calculations, format data and/or perform any other type of HDTV processing that may be required. 
     The HDTV  420  may communicate with mass data storage  427  that stores data in a nonvolatile manner such as optical and/or magnetic storage devices for example hard disk drives HDD and/or DVDs. The HDD may be a mini HDD that includes one or more planters having a diameter that is smaller than approximately 1.8″. The HDTV  420  may be connected to memory  428  such as RAM, ROM, low latency nonvolatile memory such as flash memory and/or other suitable electronic data storage. The HDTV  420  also may support connections with a WLAN via a WLAN network interface  429 . 
     Referring now to  FIG. 5B , the device may implement and/or be implemented in a WLAN interface of a vehicle. In some implementations, the device implement a powertrain control system  432  that receives inputs from one or more sensors such as temperature sensors, pressure sensors, rotational sensors, airflow sensors and/or any other suitable sensors and/or that generates one or more output control signals such as engine operating parameters, transmission operating parameters, and/or other control signals. 
     The device may also be implemented in other control systems  440  of the vehicle  430 . The control system  440  may likewise receive signals from input sensors  442  and/or output control signals to one or more output devices  444 . In some implementations, the control system  440  may be part of an anti-lock braking system (ABS), a navigation system, a telematics system, a vehicle telematics system, a lane departure system, an adaptive cruise control system, a vehicle entertainment system such as a stereo, DVD, compact disc and the like. Still other implementations are contemplated. 
     The powertrain control system  432  may communicate with mass data storage  446  that stores data in a nonvolatile manner. The mass data storage  446  may include optical and/or magnetic storage devices for example hard disk drives HDD and/or DVDs. The HDD may be a mini HDD that includes one or more platters having a diameter that is smaller than approximately 1.8″. The powertrain control system  432  may be connected to memory  447  such as RAM, ROM, low latency nonvolatile memory such as flash memory and/or other suitable electronic data storage. The powertrain control system  432  also may support connections with a WLAN via a WLAN network interface  448 . The control system  440  may also include mass data storage, memory and/or a WLAN interface (all not shown). 
     Referring now to  FIG. 5C , the device can be implemented in a WLAN interface of cellular phone  450  that may include a cellular antenna  451 . In some implementations, the cellular phone  450  includes a microphone  456 , an audio output  458  such as a speaker and/or audio output jack, a display  460  and/or an input device  462  such as a keypad, pointing device, voice actuation and/or other input device. The signal processing and/or control circuits  452  and/or other circuits (not shown) in the cellular phone  450  may process data, perform coding and/or encryption, perform calculations, format data and/or perform other cellular phone functions. 
     The cellular phone  450  may communicate with mass data storage  464  that stores data in a nonvolatile manner such as optical and/or magnetic storage devices for example hard disk drives HDD and/or DVDs. The HDD may be a mini HDD that includes one or more platters having a diameter that is smaller than approximately 1.8″. The cellular phone  450  may be connected to memory  466  such as RAM, ROM, low latency nonvolatile memory such as flash memory and/or other suitable electronic data storage. The cellular phone  450  also may support connections with a WLAN via a WLAN network interface  468 . 
     Referring now to  FIG. 5D , the device can be implemented in a WLAN interface of a set top box  480 . The set top box  480  receives signals from a source such as a broadband source and outputs standard and/or high definition audio/video signals suitable for a display  488  such as a television and/or monitor and/or other video and/or audio output devices. The signal processing and/or control circuits  484  and/or other circuits (not shown) of the set top box  480  may process data, perform coding and/or encryption, perform calculations, format data and/or perform any other set top box function. 
     The set top box  480  may communicate with mass data storage  490  that stores data in a nonvolatile manner. The mass data storage  490  may include optical and/or magnetic storage devices for example hard disk drives HDD and/or DVDs. The HDD may be a mini HDD that includes one or more platters having a diameter that is smaller than approximately 1.8″. The set top box  480  may be connected to memory  494  such as RAM, ROM, low latency nonvolatile memory such as flash memory and/or other suitable electronic data storage. The set top box  480  also may support connections with a WLAN via a WLAN network interface  496 . 
     Referring now to  FIG. 5E , the device can be implemented in a WLAN interface of a media player  500 . The device may implement and/or be implemented in a WLAN interface. In some implementations, the media player  500  includes a display  507  and/or a user input  508  such as a keypad, touchpad and the like. In some implementations, the media player  500  may employ a graphical user interface (GUI) that typically employs menus, drop down menus, icons and/or a point-and-click interface via the display  507  and/or user input  508 . The media player  500  further includes an audio output  509  such as a speaker and/or audio output jack. The signal processing and/or control circuits  504  and/or other circuits (not shown) of the media player  500  may process data, perform coding and/or encryption, perform calculations, format data and/or perform any other media player function. 
     The media player  500  may communicate with mass data storage  510  that stores data such as compressed audio and/or video content in a nonvolatile manner. In some implementations, the compressed audio files include files that are compliant with MP3 format or other suitable compressed audio and/or video formats. The mass data storage may include optical and/or magnetic storage devices for example hard disk drives HDD and/or DVDs. The HDD may be a mini HDD that includes one or more platters having a diameter that is smaller than approximately 1.8″. The media player  500  may be connected to memory  514  such as RAM, ROM, low latency nonvolatile memory such as flash memory and/or other suitable electronic data storage. The media player  500  also may support connections with a WLAN via a WLAN network interface  516 . Still other implementations in addition to those described above are contemplated. 
     Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification and the following claims.