Handover in wireless communications

Abstract

Systems and methodologies are described that facilitate handing over mobile device communications in a wireless network from a source base station to a target base station without using a random access channel (RACH). In this regard, the mobile device can monitor multiple base stations determining timing information related thereto and access scheduling request channels for the base stations. When ready for handover, the mobile device can request data resources over the scheduling request channel using the appropriate timing information.

1 . A method for handing over communications in a wireless network, comprising:
 receiving wireless communications service from a source base station;   receiving multiple assigned uplink control channels for transmitting schedule request signals to a plurality of target base stations; and   transmitting a scheduling request to a selected target base station of the plurality of target base stations over at least one of the assigned uplink control channels.   
   
   
       2 . The method of  claim 1 , further comprising receiving timing advance (TA) information from the plurality of target base stations, the TA information is utilized to transmit the scheduling request. 
   
   
       3 . The method of  claim 2 , the TA information is received in response to sounding reference signals sent to the plurality of target base stations. 
   
   
       4 . The method of  claim 2 , the TA information is derived from additional channels of the plurality of base stations in an asynchronous wireless communications network. 
   
   
       5 . The method of  claim 2 , further comprising maintaining synchronization with the one or more assigned uplink control channels, using the trimming advance, to facilitate subsequent handing over of communication to the selected target base station. 
   
   
       6 . The method of  claim 5 , the scheduling request transmitted to the selected target base station based at least in part on a small timing difference between the target base station and the source base station as compared to the other target base stations. 
   
   
       7 . The method of  claim 1 , the source base station and the target base station are synchronized in time, the timing for the source base station is utilized to transmit the scheduling request. 
   
   
       8 . The method of  claim 1 , further comprising selecting a transmission time interval (TTI) having a longer cyclic prefix with respect to the selected target base station for transmitting the handover communication. 
   
   
       9 . The method of  claim 1 , further comprising receiving wireless communication service from the selected target base station following transmitting the initial handover communication. 
   
   
       10 . A wireless communications apparatus, comprising:
 at least one processor configured to:
 monitor timing of a plurality of base stations; and 
 select a target base station in the plurality of base stations for handover of communications based at least in part on the monitored timing; and 
   a memory coupled to the at least one processor.   
   
   
       11 . The wireless communications apparatus of  claim 10 , the timing is monitored based at least in part on transmitting sounding reference signals to the base stations. 
   
   
       12 . The wireless communications apparatus of  claim 11 , a timing advance for the base stations is received in reference to the sounding reference signals. 
   
   
       13 . The wireless communications apparatus of  claim 12 , the at least one processor further configured to transmit an initial handover message to the target base station based at least in part on the timing advance. 
   
   
       14 . The wireless communications apparatus of  claim 13 , the at least one processor further configured to select a transmission time interval (TTI) having a longer cyclic prefix with respect to the target base station for transmitting the initial handover message. 
   
   
       15 . The wireless communications apparatus of  claim 10 , the at least one processor further configured to establish an uplink schedule request channel with the plurality of base stations, the established uplink schedule request channel is utilized to handover communications. 
   
   
       16 . The wireless communications apparatus of  claim 10 , the at least one processor further configured to determine a timing advance for the base stations based at least in part on a difference between timing of the target base station and a source base station in a wireless communications network. 
   
   
       17 . The wireless communications apparatus of  claim 10 , the monitoring of the uplink scheduling resources is performed during communications gaps requested from a source base station to which the wireless communications apparatus is currently communicating. 
   
   
       18 . A wireless communications apparatus for handing over communications in a wireless network, comprising:
 means for receiving wireless communications service from a source base station;   means for receiving multiple assigned uplink control channels for transmitting schedule request signals to a plurality of target base stations; and   means for transmitting a scheduling request to a selected target base station of the plurality of target base stations over at least one of the assigned uplink control channels.   
   
   
       19 . The wireless communications apparatus of  claim 18 , further comprising means for receiving timing advance (TA) information from the plurality of target base stations, the TA information is utilized to transmit the scheduling request. 
   
   
       20 . The wireless communications apparatus of  claim 19 , the TA information is received in response to sounding reference signals sent to the plurality of target base stations. 
   
   
       21 . The wireless communications apparatus of  claim 19 , the TA information is derived from additional channels of the plurality of base stations in an asynchronous wireless communications network. 
   
   
       22 . The wireless communications apparatus of  claim 19 , further comprising means for maintaining synchronization with the one or more assigned uplink control channels, using the trimming advance, to facilitate subsequent handing over of communication to the selected target base station. 
   
   
       23 . The wireless communications apparatus of  claim 22 , the scheduling request transmitted to the selected target base station based at least in part on a small timing difference between the target base station and the source base station as compared to the other target base stations. 
   
   
       24 . The wireless communications apparatus of  claim 18 , the source base station and the target base station are synchronized in time, the timing for the source base station is utilized to transmit the scheduling request. 
   
   
       25 . The wireless communications apparatus of  claim 18 , further comprising selecting a transmission time interval (TTI) having a longer cyclic prefix with respect to the selected target base station for transmitting the handover communication. 
   
   
       26 . The wireless communications apparatus of  claim 18 , further comprising receiving wireless communication service from the selected target base station following transmitting the initial handover communication. 
   
   
       27 . A computer program product, comprising:
 a computer-readable medium comprising:
 code for causing at least one computer to receive wireless communications service from a source base station; 
 code for causing the at least one computer to receive multiple assigned uplink control channels for transmitting schedule request signals to a plurality of target base stations; and 
 code for causing the at least one computer to transmit a scheduling request to a selected target base station of the plurality of target base stations over at least one of the assigned uplink control channels.