Abstract:
In general, in one aspect, the disclosure describes an apparatus that includes a first radio to communicate with a first wireless network and a second radio to communicate with a second wireless network. The first wireless network transmits a map defining locations within an assigned spectrum data is to be communicated therebetween. An earliest possible location defined in map is such that the map can be parsed within the time it would take to get to the earliest possible location so that the radio can be turned off after receiving the map until the location defined in the map, and the second radio is active when the first radio is not.

Description:
BACKGROUND 
       [0001]    The desire for wireless communications continues to increase and accordingly the number and type of wireless networks (e.g., wireless local area network (WLAN), wireless metropolitan area networks (WMAN), wireless personal area networks (WPAN)) available for wireless communications continues to increase. In order for mobile devices (e.g., laptop computers, handheld devices) to provide wireless communications there is a need for the devices to accommodate several different wireless network types (network models). In order to support multiple wireless networks, the mobile devices may include a cluster of different radios for communicating over the various network types (referred to as the Multi-Radio coexistence Platforms (MRP)). 
         [0002]    The various radios may operate in overlapping or adjacent frequency bands and possibly suffer from interference when they operate at overlapping time instants due to, for example, physical proximity and radio power leakage. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0003]    The features and advantages of the various embodiments will become apparent from the following detailed description in which: 
           [0004]      FIG. 1  illustrates a conceptual WiMAX frame structure, according to one embodiment; 
           [0005]      FIG. 2  illustrates an example WiMAX superframe with WiFi and WiMAX time-division multiplexed, according to one embodiment; 
           [0006]      FIG. 3  illustrates example relations between DL-MAP/UL-MAP and DL-bursts and UL bursts defined thereby, according to one embodiment; 
           [0007]      FIG. 4  illustrates example relations between DL-MAP/UL-MAP and DL-bursts and UL bursts defined thereby, according to one embodiment; and 
           [0008]      FIG. 5  illustrates example relations between DL-MAP/UL-MAP and DL-bursts and UL bursts defined thereby, according to one embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0009]    A Multi-Radio coexistence Platforms (MRP) mobile device, such as a cellular phone, may include multiple wireless interfaces for communicating with multiple different wireless networks. For example, the MRP may include some combination of wireless local area network (WLAN) radio, wireless metropolitan area network (WMAN) radio, and wireless personal area network (WPAN) radio. The WMAN network may be compliant with the IEEE standard 802.16.x (WiMAX) and the WLAN network may be compliant with IEEE standard 802.11.x (WiFi). In order to reduce MRP interference between the radios for the various wireless networks, a time-division multiplexing (TDM) based mechanism can be used to make different radios active at different times. 
         [0010]      FIG. 1  illustrates the conceptual WiMAX frame structure based on random tone permutation, for which the WiMAX radio physically occupies a set of tones randomly selected from the whole band. The header includes a preamble, frame control (FC), downlink map (DL-MAP) and uplink map (UL-MAP). The DL-MAP and UL-MAP define the portions of the frame utilized for receiving data from base station (DL bursts) and transmitting data to the base station (UL burst) respectively. 
         [0011]      FIG. 2  illustrates an example of how WiFi and WiMAX may co-exist on an MRP based on time-division multiplexing. The MRP WiMAX radio at the MRP listens to WiMAX base station during each header duration. Once the WiMAX radio processes the DL-MAP and UL-MAP and understands the DL-burst and UL-burst timing it only needs to be active during these durations. The WiFi radio can be active during the rest of the time. 
         [0012]      FIG. 3  illustrates example relations between DL-MAP/UL-MAP and DL-bursts and UL bursts defined thereby for a typical WiMAX frame. The WiMAX frame includes a DL portion followed by an UL portion as defined by the FC. The DL-MAP describes DL-bursts in a current frame (frame in which DL-map is received) and DL sub-frame immediately follows the MAP info. The DL-MAP is in effect describing what immediately follows. The UL-MAP describes UL-bursts in a next frame (frame after UL-map is received) and the UL sub-frame follows the DL sub-frame. The UL-MAP is in effect describing what happens in 1½ frame (this complete frame plus next DL sub-frame). 
         [0013]    Since the DL sub-frame with which the DL burst will occur immediately follows the WiMAX header (DL-MAP), ideally the WiMAX radio can understand its scheduled DL-burst durations as soon as the WiMAX header ends. However, in reality a delay (possibly substantial) is often associated with the WiMAX MAP parsing and, consequently, the WiMAX radio cannot know the locations of its scheduled DL-burst immediately at the end of WiMAX header. Therefore, the WiMAX radio has to listen to all DL-bursts until the MAP parsing is completed. If the MAP parsing delay is significant the WiMAX radio may remain active for an excessive amount of time leaving little time left for other co-located radios to operate. 
         [0014]    Reversing the sequence of DL sub-frame and UL sub-frame within the WiMAX superframe (the UL sub-frame follows the WiMAX header and the DL sub-frame follows UL sub-frame) would provide a time gap with which map parsing could occur. The time gap would be equal to the length of UL sub-frame between the DL-MAP and the start of the DL sub-frame. When such time gap is longer than the MAP parsing delay, the MRP WiMAX radio will know exactly when its DL-burst is scheduled before the DL sub-frame starts. Accordingly, the WiMAX radio does not need to listen to other DL-bursts other than its own, and the negative impact of large MAP parsing delay on MRP is eliminated. 
         [0015]      FIG. 4  illustrates example relations between DL-MAP/UL-MAP and DL-bursts and UL bursts defined thereby. The WiMAX frame includes an UL portion followed by a DL portion as defined by the FC (UL/DL sub-frames are reversed from  FIG. 3 ). The DL-MAP still defines DL bursts in the current frame and the UL-MAP still defines UL-burst in the next frame. The DL-MAP is in effect describing what happens in the second half of the current frame (after UL sub-frame) and the UL-MAP is in effect describing what happens in the next frame (immediately after next frames header). 
         [0016]    This method requires the structure of the WiMAX frame to be modified and introduces a delay in the receipt of DL bursts equal to the gap (length of the UL-subframe). For example, if the WiMAX superframe size is 5 ms and the DL/UL ratio is 1:1 then the delay would be 2.5 ms. 
         [0017]    Rather than modifying the WiMAX frame to provide a gap for map parsing to occur the DL map can be modified to define the DL burst in the next frame instead of the current frame. The time gap would be fixed at a length equal to the length of a WiMAX superframe (e.g., 5 ms). Since the time gap is longer than the MAP parsing delay, the MRP WiMAX radio will know exactly when its DL-burst is scheduled before the DL sub-frame starts. Accordingly, the WiMAX radio does not need to listen to other DL-bursts other than its own, and the negative impact of large MAP parsing delay on MRP is eliminated. 
         [0018]      FIG. 5  illustrates example relations between DL-MAP/UL-MAP and DL-bursts and UL bursts defined thereby. Both the DL-MAP and the UL-MAP describe the DL bursts and the UL bursts respectively that occur in the next frame. The DL-MAP is in effect describing what happens in the next frame (in the DL sub frame immediately after next frames header). The UL-MAP describes UL-bursts that happen in the UL sub-frame after the next DL sub-frame. The UL-MAP still is in effect describing what happens in 1½ frame. 
         [0019]    The implementations defined in  FIGS. 4 and 5  delayed expected receipt of WiMAX data to account for map parsing delays in order to avoid the WiMAX radio from hogging radio time from the WiFi radio during the map parsing time. The implementations result in a delay in receipt of communications from the WiMAX base station so that throughput degradation might result. However, without using the proposed methods, WiMAX may not be able to efficiently operate concurrently with the WiFi radios on the MRP, in the presence of large MAP parsing delay. The proposed methods can be implemented as supplemental features of WiMAX radios and the features may be turned on only when there is need for multi-radio co-existence. 
         [0020]    The implementations discussed above were discussed with specific reference to eliminating the effect of map parsing delay on a WiMAX radio to provide a coexisting WiFi radio additional bandwidth. The implementation is not limited to coexisting WiFi radios but may be any type of coexisting radio (e.g., WLAN, WPAN). In addition, the techniques for handling map parsing delays made specific reference to WiMAX radios but are not limited thereto. Rather, the techniques could be applicable to other radios where the header includes a map defining where within an assigned spectrum data is to be communicated (received and/or transmitted). 
         [0021]    Although the disclosure has been illustrated by reference to specific embodiments, it will be apparent that the disclosure is not limited thereto as various changes and modifications may be made thereto without departing from the scope. Reference to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described therein is included in at least one embodiment. Thus, the appearances of the phrase “in one embodiment” or “in an embodiment” appearing in various places throughout the specification are not necessarily all referring to the same embodiment. 
         [0022]    The various embodiments are intended to be protected broadly within the spirit and scope of the appended claims.