Method and apparatus for seamless handover in a wireless communication network

Abstract

A mobile station is configured to support handover from a source base station to a target base station. The mobile station receives signaling from the target base station that indicates Packet Data Convergence Protocol (PDCP) protocol data units which have been successfully received at the target base station. In response, the mobile station generates further PDCP protocol data units for missing PDCP service data units from corresponding PDCP service data units buffered at the mobile station. The generating comprises using a different header compression state from that which was used for the missing PDCP service data units and ciphering specific to a connection with the target base station. The mobile station transmits the further PDCP protocol data units to the target base station.

What is claimed is: 
     
       1. A method in a mobile station configured to support handover from a source base station to a target base station, the method comprising:
 receiving signaling from the target base station that indicates Packet Data Convergence Protocol (PDCP) protocol data units which have been successfully received at the target base station; 
 responsive to the signaling, generating further PDCP protocol data units for missing PDCP service data units from corresponding PDCP service data units buffered at the mobile station, the generating comprising using a different header compression state from that which was used for the missing PDCP service data units and ciphering specific to a connection with the target base station; and 
 transmitting the further PDCP protocol data units to the target base station. 
 
     
     
       2. The method of  claim 1 , claim 21, further comprising forgoing transmission of PDCP service data units that are indicated by the target base station as having been successfully received. 
     
     
       3. The method of  claim 1 , claim 21, wherein generating the further PDCP protocol data units is further responsive to performing a handover from the source base station to the target base station. 
     
     
       4. The method of  claim 3 , wherein performing the handover is responsive to transmitting the missing PDCP service data units to the source base station. 
     
     
       5. The method of  claim 1 , claim 21, wherein the signaling from the target base station comprises Automatic Repeat request (ARQ) signaling. 
     
     
       6. The method of  claim 1 , claim 21, wherein the mobile station is comprised in a Long Term Evolution (LTE) communication network. 
     
     
       7. The method of  claim 1 , claim 21, further comprising transmitting a PDCP protocol data unit to a base station that transfers a corresponding PDCP service data unit to a core network. 
     
     
       8. The method of  claim 7 , wherein the PDCP protocol data unit is one of the PDCP protocol data units successfully received at the target base station or one of the further PDCP protocol data units. 
     
     
       9. A mobile station configured to support handover from a source base station to a target base station, the mobile station comprising:
 a wireless communication interface;   processing circuitry connected to the wireless communication interface, the processing circuitry being configured to:
 receive signaling from the target base station that indicates Packet Data Convergence Protocol (PDCP) protocol data units which have been successfully received at the target base station; 
 responsive to the signaling, generate further PDCP protocol data units for missing PDCP service data units from corresponding PDCP service data units buffered at the mobile station; and 
 transmit, via the wireless communication interface, the further PDCP protocol data units to the target base station; 
 wherein to generate the further PDCP protocol data units, the processing circuitry is configured to use a different header compression state from that which was used for the missing PDCP service data units and ciphering specific to a connection with the target base station. 
   
     
     
       10. The mobile station of  claim 9 , claim 23, wherein the processing circuitry is further configured to forgo transmission of PDCP service data units that are indicated by the target base station as having been successfully received. 
     
     
       11. The mobile station of  claim 9 , claim 23, wherein the processing circuitry is configured to generate the further PDCP protocol data units further responsive to performing a handover from the source base station to the target base station. 
     
     
       12. The mobile station of  claim 11 , wherein the processing circuitry is configured to perform the handover responsive to transmitting the missing PDCP service data units to the source base station via the wireless communication interface. 
     
     
       13. The mobile station of  claim 9 , claim 23, wherein the signaling from the target base station comprises Automatic Repeat request (ARQ) signaling. 
     
     
       14. The mobile station of  claim 9 , claim 23, wherein the mobile station is comprised in a Long Term Evolution (LTE) communication network. 
     
     
       15. The mobile station of  claim 9 , claim 23, wherein the processing circuitry is further configured to transmit, via the wireless communication interface, a PDCP protocol data unit to a base station that transfers a corresponding PDCP service data unit to a core network. 
     
     
       16. The mobile station of  claim 15 , wherein the PDCP protocol data unit is one of the PDCP protocol data units successfully received at the target base station or one of the further PDCP protocol data units. 
     
     
       17. A non-transitory computer readable medium storing a computer program product for controlling a programmable mobile station configured to support handover from a source base station to a target base station, the computer program product comprising software instructions that, when executed by processing circuitry of the programmable mobile station, cause the programmable mobile station to:
 receive signaling from the target base station that indicates Packet Data Convergence Protocol (PDCP) protocol data units which have been successfully received at the target base station;   responsive to the signaling, generate further PDCP protocol data units for missing PDCP service data units from corresponding PDCP service data units buffered at the mobile station, the generating comprising using a different header compression state from that which was used for the missing PDCP service data units and ciphering specific to a connection with the target base station; and   transmit the further PDCP protocol data units to the target base station.   
     
     
       18. The non-transitory computer readable medium of  claim 17 , wherein the software instructions further cause the programmable mobile station to forgo transmission of PDCP service data units that are indicated by the target base station as having been successfully received. 
     
     
       19. The non-transitory computer readable medium of  claim 17 , wherein the software instructions cause the programmable mobile station to generate the further PDCP protocol data units further responsive to performing a handover from the source base station to the target base station. 
     
     
       20. The non-transitory computer readable medium of  claim 11 , wherein the signaling from the target base station comprises Automatic Repeat request (ARQ) signaling. 
     
     
       21. A method in a mobile station configured to support handover from a source base station to a target base station, the method comprising:
 receiving signaling from the target base station that indicates successful receipt of Packet Data Convergence Protocol (PDCP) protocol data units or PDCP service data units;   responsive to the signaling, generating further PDCP protocol data units for missing PDCP service data units from corresponding PDCP service data units buffered at the mobile station, the generating comprising ciphering specific to a connection with the target base station; and   transmitting the further PDCP protocol data units to the target base station.    
     
     
       22. The method of claim 21, wherein the generating further comprises using a different header compression state from that which was used for the missing PDCP service data units.  
     
     
       23. A mobile station configured to support handover from a source base station to a target base station, the mobile station comprising:
 a wireless communication interface; and   processing circuitry connected to the wireless communication interface, the processing circuitry being configured to:
 receive signaling from the target base station that indicates successful receipt of Packet Data Convergence Protocol (PDCP) protocol data units or PDCP service data units; 
 responsive to the signaling, generate further PDCP protocol data units for missing PDCP service data units from corresponding PDCP service data units buffered at the mobile station; and 
 transmit, via the wireless communication interface, the further PDCP protocol data units to the target base station; 
 wherein to generate the further PDCP protocol data units, the processing circuitry is configured to cipher specific to a connection with the target base station.  
   
     
     
       24. The mobile station of claim 23, wherein to generate the further PDCP protocol data units, the processing circuitry is further configured to use a different header compression state from that which was used for the missing PDCP service data units.  
     
     
       25. A target base station supporting handover of a mobile station from a source base station to the target base station in a wireless communication network in which Packet Data Convergence Protocol (PDCP) protocol data units are received from the mobile station, the target base station comprising a processor and a memory, the memory comprising instructions executable by the processor configured to:
 transmit signaling from the target base station that indicates successful receipt of Packet Data Convergence Protocol (PDCP) protocol data units or PDCP service data units; and   receive further PDCP protocol data units generated for missing PDCP service data units from corresponding PDCP service units buffered at the mobile station responsive to the signaling, the further PDCP protocol data units regenerated from the missing PDCP service data units using ciphering specific to a connection with the target base station.    
     
     
       26. The target base station of claim 25, wherein the regenerating further comprises using a different header compression state from that which was used for the missing PDCP service data units.  
     
     
       27. The target base station of claim 25, wherein the signaling from the target base station comprises Automatic Repeat request (ARQ) signaling.  
     
     
       28. The target base station of claim 25, wherein the processor is further configured to transfer a PDCP service data unit to a core network.  
     
     
       29. The target base station of claim 25, wherein the target base station is comprised in a Long Term Evolution (LTE) communication network.  
     
     
       30. The target base station of claim 25, wherein the processor is further configured to transmit a PDCP protocol data unit to a base station that transfers a corresponding PDCP service data unit to a core network.