Systems and methods for reducing communication unit scan time in wireless networks

Abstract

A communication unit operates in a wireless-networking environment and maintains a mapping for active channels and associated network identifiers. The communication unit may associate with a wireless network using the mapping for one or more of the active channels having a selected network identifier. For associations and reassociations with wireless networks, the communication unit may selectively scan the channels having mapping stored in a table to more quickly identify active channels and thereby reduce scan time. In some embodiments, an access point may perform channel-width measurements and radar detection using the bitmap.

1 . A method for reducing scan time by a mobile communication unit comprising: 
 maintaining a single mapping within the mobile communication unit for one or more active channels associated with a single network identifier; and    tuning to one of the active channels using the single mapping to allow the mobile communication unit to either associate or reassociate with a wireless network having the associated network identifier.    
   
   
       2 . The method of  claim 1  further comprising scanning to determine network identifiers associated with the one or more active channels, and 
 wherein the maintaining comprises:    generating one or more single bitmaps for the one or more active channels associated with single network identifiers; and    storing the bitmaps in a bitmap table, and    wherein to either associate or reassociate, the method comprises:    scanning the one or more active channels identified in the bitmap table; and    refraining from scanning for channels not identified in the bitmap table to reduce scan time.    
   
   
       3 . The method of  claim 1  further comprising: 
 scanning predetermined channels to identify network identifiers associated with active of the predetermined channels; and    generating a bitmap for the active channels and their associated network identifiers,    wherein the predetermined channels are predetermined for a geographic location.    
   
   
       4 . The method of  claim 2  wherein associating comprises sending an association request on a channel associated with a selected network identifier through an access point, wherein a network associated with the selected network identifier authenticates the communication unit in response to the association request.  
   
   
       5 . The method of  claim 4  wherein the associating further comprises: 
 sending the selected network identifier to the network-interface circuitry;    retrieving the bitmap associated with the selected network identifier by the driver circuitry;    tuning, in response to the bitmap, to a channel for sending the association request; and    sending the association request to the access point over a wireless link using an antenna.    
   
   
       6 . The method of  claim 1  further comprising passively scanning channels, and waiting for receipt of a beacon frame, the beacon frame including the network identifier associated with one of the scanned channels.  
   
   
       7 . The method of  claim 6  wherein passively scanning channels further comprises receiving a probe response directed to another communication unit on one of the channels, the probe response including the network identifier associated with an active channel.  
   
   
       8 . The method of  claim 7  wherein the scanning further comprises active scanning for predetermined channels by: 
 transmitting a probe request on at least one of the predetermined channels; and    waiting to receive a probe response from an access point, the probe response including the network identifier associated with an active channel.    
   
   
       9 . A mobile system that scans channels of wireless networks with a reduced scan time comprising: 
 network-interface circuitry to maintain a mapping for active channels and associated network identifiers; and    transceiver circuitry to tune to one of the active channels using the mapping for the active channel to allow either an association or a reassociation with a wireless network having a selected network identifier,    wherein the mapping comprises one of a bitmap, an array, a linked list, or a hash table.    
   
   
       10 . A method comprising: 
 identifying valid channels for a geographic region in which a communication unit is located;    transmitting a probe request on a predetermined subset of the identified valid channels; and    waiting for receipt of either a beacon frame or a probe-response frame on channels of the identified valid channels other than the channels of the predetermined subset, the probe-response frame being directed to another communication unit.    
   
   
       11 . The method of  claim 10  wherein the transmitting the probe request is performed for channels of the predetermined subset identified a channel mapping stored in the communication unit, the mapping comprising one of either a bitmap, an array, a linked list, or a hash table.  
   
   
       12 . The method of  claim 11  wherein for channels of the predetermined subset, the method comprises waiting, in response to transmission of the probe request, for a probe-response frame directed to the communication unit, the probe-response frame including a network identifier.  
   
   
       13 . The method of  claim 12  further comprising: 
 generating bitmaps valid channels for which a probe-response frame or beacon-frame is received; and    re-associating with a network using at least one of the bitmaps.    
   
   
       14 . The method of  claim 9  wherein at least one of the transmitting and the waiting is performed sequentially for each of the identified valid channels.