Abstract:
A relay may partially decode a frame to get enough information to know when to amplify and transmit the frame to a user. By limiting transmission in this way, less interference may be generated in some cases. By using only limited decoding, the relay overhead may be reduced in some embodiments.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of Provisional Application No. 60/986,775, filed Nov. 9, 2007. 
     
    
     BACKGROUND 
       [0002]    This relates generally to relays or repeaters that forward information from a transmitter to a remote receiver. 
         [0003]    Relays or repeaters allow a transmitter to send a wireless signal to a receiver that is beyond the range normally accessible by the transmitter. It allows wireless networks to be extended with less cost. 
         [0004]    Metropolitan area networks may provide broadband access to subscribers in remote locations. For example, IEEE 802.16e, also known as Mobile WiMAX, integrates relays from multi-hop communications. See Broadband Wireless Access, WirelessMan, 802-16e-2005, IEEE Standards Association, Piscataway, N.J. 08855, U.S.A. A relay enhanced IEEE 802.16j,m network can provide large area radio coverage, achieve a high quality of service, and can be economically deployed and operated. See Multihop Relay and Advanced Air Interface, available from IEEE Standards Association. 
         [0005]    Similarly, in IEEE 802.15.3c (Millimeter Wave, WPAN/WLAN) relay stations provide radio coverage for large buildings, corridors, and reliably throughput communication between rooms, floors, and spaced areas in residential and office environments. See IEEE 802.15c-2003 WPAN Task Group, draft text DF3. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a depiction of a relay in accordance with one embodiment of the present invention; 
           [0007]      FIG. 2  is a network topology for one embodiment of the present invention; 
           [0008]      FIG. 3  shows a downlink and uplink subframe in accordance with one embodiment of the present invention; 
           [0009]      FIG. 4  is a schematic depiction of a relay in accordance with another embodiment of the present invention; 
           [0010]      FIG. 5  is a system depiction for one embodiment of the relay shown in  FIG. 4 ; and 
           [0011]      FIG. 6  is a depiction of a downlink subframe for the embodiment shown in  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    Referring to  FIG. 1 , a relay may include a receive antenna  14  coupled to a relay chain  10 . The relay chain  10  is coupled to a controller  32 . Thus, the antenna  14  may receive a signal from a base station in a wireless network. It may forward a signal through a transmit antenna  30  to a subscriber station in that network. Operation of relay chain  10  may be controlled by the controller  32 . 
         [0013]    The relay chain  10  includes a band-pass filter  12 , an amplifier  16 , a mixer  18 , a low-pass filter  20 , a switch  22 , a mixer  24 , an amplifier  26 , and a band-pass filter  28 , coupled to the antenna  30 . 
         [0014]    The controller  32  may include a synthesizer  34  that provides a signal for the mixer  18 . A down converter (DC)  36  may receive a signal from the relay chain to be selectively decoded. The DC  36  is coupled to an analog-to-digital converter  38  which couples to a baseband unit  40 . The baseband unit  40  is coupled to a decoder  42 . The decoder  42  output is provided to a timer  44 . The timer  44  provides an output control signal to control the on or off state of the switch  22 . In addition, a signal indicated at B may be provided from the low-pass filter  20  to the DC  36 . The synthesizer  34  also issues a signal D to the mixer  24 . 
         [0015]    In some embodiments, the controller  32  enables selective decoding of a signal received by the relay chain  14 . For example, in an IEEE 802.16j,m system, the relay chain  10  and controller  32  may decode a map field from a downlink subframe. The map field describes allocation of data within downlink and uplink subframes. The map field may always be located in a readily locatable subframe address in some systems. Thus, rather than decode the entire uplink and downlink subframe, only the map field may be decoded in the signal received via the link B in  FIG. 1 . This reduces the overhead on the relay chain  10 . In addition, it is not necessary for the relay chain  10  to re-encode any data. 
         [0016]    The map field information may be used to determine which subscriber stations, in what time frames, will be receiving information. This may be used by the timer  44  to then turn the switch  22  on and off so that the relay chain  10  only operates during those time frames when pertinent subscriber stations, serviced by the relay chain  10 , are to receive signals. 
         [0017]    Since it is not necessary to re-encode any information, the system, shown in  FIG. 1 , operates as an amplify and forward relay and does not need to decode the entire set of information that is received and then re-encode it for subsequent transmission. An amplify and forward relay merely amplifies and retransmits the received signal. 
         [0018]    On the other hand, the amount of interference and the likelihood of collisions may be reduced, in some embodiments, because of the reduced information that gets relayed by the relay chain  10 , compared to a system that does not do selective decoding and selective relaying. That is, retransmission only occurs for pertinent subscriber stations in pertinent time frames in some embodiments. 
         [0019]    As another example, service information contained in the beacon fields of an 802.15.3 superframe may be used in the same way to enable selective decoding and selective relaying of only information pertinent to subscriber stations served by the relay. 
         [0020]    Thus, referring to  FIG. 2 , the base station to relay station link extends from the base station BS to the relay station RS. The relay station then selectively forwards information on the RS to SS link to the subscriber station SS, as indicated in  FIG. 2 . 
         [0021]    The downlink subframe  54  may then include a preamble  46 , the downlink and uplink map  48 , data  50  for the base station to each subscriber station, and the relay station identifying information  52 . The base station to subscriber station data  50  may effectively be transmitted in an amplify and forward fashion only to the correct subscriber station in the correct time frames so that it is simply forwarded without decoding, other than the limited decoding described above, directly to the pertinent subscriber station. 
         [0022]    The uplink subframe  56  includes the subscriber station to base station data  58  for each subscriber station and the relay station identifying information  62 . 
         [0023]    Referring to  FIG. 4 , in accordance with another embodiment, a sectorized antenna chain  30   a,    30   b,  and  30   c  may be connected to a sectorized switcher  46 . Thus, as shown in  FIG. 5 , a sectorized antenna may transmit a signal that is directed to a particular subscriber station SS 1 , SS 2 , SS 3 , each subscriber station located in a different pie-shaped sector relative to the antenna chain  30 . By appropriate positioning of the relay station RS, relative to the subscriber stations, a sectorized antenna can transmit, in only a particular sector direction, for the appropriate subscriber station at the appropriate times and with the appropriate signals. In contrast to the embodiment shown in  FIG. 2 , which may use omni-directional broadcasting, sectorized or directional broadcast transmission may be utilized to reduce interference and collisions. 
         [0024]    Returning to  FIG. 4 , the signal from the timer  44  is used not only to control the switch  22 , but it also provides a signal to the sector switcher  46  to indicate which antenna should be used, depending on the location of the subscriber station that is to receive the signal at a particular time. Thus, the correct sectorized antenna  30   a,    30   b,  or  30   c  is selected by the sector switcher  46  to transmit to the subscriber station that is supposed to receive the signal during the pertinent time period identified by the timer  44 . Information may be provided in the map field information  48  that gives the subscriber station location. Of course, more or less antennas  30  may be used. 
         [0025]    By using high antenna gain and narrow beamwidths, the quality of service may be improved. For relay station to subscriber station links, the sectorized directional transmit antennas  30   a - 30   c  may be used for the downlink. For uplink retransmission, the same antenna system may be used with another relay chain that amplifies and retransmits signals in opposite directions. 
         [0026]    A downlink frame, shown in  FIG. 6 , includes individual relay station fields  64  for each of the three sectors illustrated in  FIG. 5 . Of course, more sectors or less sectors may be utilized in some embodiments. In addition, other types of directional antennas may be utilized. 
         [0027]    References throughout this specification to “one embodiment” or “an embodiment” mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one implementation encompassed within the present invention. Thus, appearances of the phrase “one embodiment” or “in an embodiment” are not necessarily referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be instituted in other suitable forms other than the particular embodiment illustrated and all such forms may be encompassed within the claims of the present application. 
         [0028]    While the present invention has been described with respect to a limited number of embodiments, those skilled in the art will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of this present invention.