Handover in a wireless local area network (wlan)

Abstract

In triggering a handoff by a wireless transmit/receive unit (WTRU) from a current basic service set (BSS) in a wireless local area network (WLAN), the following are performed. A highest class of traffic service and quality of service (QoS) is determined for the highest class from a basic service set (BSS) beacon. Handoff is terminated and communication is retained with a current BSS when the signal to noise ratio (SNR) or received signal strength (RSS) is greater than a high threshold of the highest class. Other criteria are evaluated to determine whether a handoff is desired when the SNR or RSS is less than the high threshold.

1 . A method of performing handover in wireless communications operating in a plurality of basic service sets (BSSs), the method comprising:
 establishing a high and a low threshold for at least one of either a signal to noise ratio (SNR) or a received signal strength (RSS) for a BSS currently serving a wireless transmit/receive unit (WTRU);   initiating a handover procedure when the at least one of SNR or RSS of the serving BSS falls below the high threshold;   determining a quality of service (QoS) index for each of a plurality of neighboring BSSs and the serving BSS;   establishing a link between the WTRU and a BSS associated with a largest of the determined QoS indexes.   
     
     
         2 . The method of  claim 1 , further comprising:
 establishing a link between the WTRU and a different BSS than the serving BSS when the at least one of SNR and RSS of the serving BSS falls below the low threshold without determining the QoS index for each neighboring BSS.   
     
     
         3 . The method of  claim 1 , further comprising:
 halting the handover procedure when the at least one of SNR and RSS increases to greater than the high threshold and maintaining a link between the WTRU and the serving BSS.   
     
     
         4 . The method of  claim 1 , wherein determining a QoS index for each of a plurality of neighboring BSSs further comprises:
 determining a list of neighboring BSSs;   for each of a plurality of traffic classes (TCs), establishing a list of QoS parameters;   for each QoS parameter for each TC, defining a high QoS threshold and a low QoS threshold;   for each TC for each neighboring BSS:
 initializing a QoS index to zero; 
 determining a value of each QoS parameter; 
 comparing the value of each QoS parameter to the high QoS threshold and low QoS threshold associated with the QoS parameter; and 
 incrementing the QoS index by one when the value of the QoS parameter is higher than the high QoS threshold, do not change the QoS index when the value of QoS parameter is between the high QoS threshold and the low QoS threshold, and subtracting (n−1) from the QoS index when the value of the QoS parameter is less than the low QoS threshold, where n is the number of QoS parameters in the list. 
   
     
     
         5 . The method of  claim 4 , wherein the list of QoS parameters includes SNR. 
     
     
         6 . The method of  claim 5 , wherein the list of QoS parameters includes at least one of frame error rate, data rate, and delay bounds. 
     
     
         7 . The method of  claim 4 , wherein the value of the QoS parameter is read from a BSS service load element.