Method and system for base station change of packet switched communications in a mobile communications system

Abstract

The present disclosure relates to a method in a mobile station for base station change from a source base station to a target base station in a cellular radio network. The base station transfers packet switched communications between the mobile station and the network, and the method comprises receiving a handover command message from the source base station at the mobile station. The method further comprises transmitting in a target cell a message to the network providing a downlink sequence number status for a packet flow subject to lossless packet switched handover implicitly acknowledging downlink packets received by the mobile station.

1 . A method in a mobile station (MS) for base station change from a source base station to a target base station in a cellular radio network, wherein a base station transfers packet switched communications between the mobile station and the network, the method comprising:
 receiving a handover command message from the source base station at the mobile station; and   transmitting in a target cell a message to the network providing a downlink sequence number status for a packet flow subject to lossless packet switched handover implicitly acknowledging downlink packets received by the mobile station.   
     
     
         2 . The method according to  claim 1 , further comprising receiving a transfer of radio link control data blocks in an acknowledged mode. 
     
     
         3 . The method according to  claim 1 , wherein the downlink sequence number status message includes the next expected Protocol Data Unit (PDU) to be received. 
     
     
         4 . A method in a radio base station (Target BSS) acting as a target base station for base station change from a source base station to a target base station in a cellular radio network, wherein a source base station (Source BSS) transfers packet switched communications between a mobile station (MS) and the network, the method comprising:
 receiving a message from the mobile station providing, after reception of a handover command message from the source base station at the mobile station, a downlink sequence number status for a packet flow subject to lossless packet switched handover implicitly acknowledging downlink packets received by the mobile station; and   begin sending packets to the mobile station from the packet implicitly acknowledged by the mobile station.   
     
     
         5 . The method according to  claim 4 , further comprising transmitting radio link control data blocks in an acknowledged mode to the mobile station. 
     
     
         6 . The method according to  claim 4 , wherein the downlink sequence number status message includes the next expected Protocol Data Unit (PDU) to be received. 
     
     
         7 . A mobile station (MS) adapted for base station change from a source base station to a target base station in a cellular radio network, wherein a base station transfers packet switched communications between the mobile station and the network, the mobile station comprising:
 a receiver;   a transmitter; and   processing circuitry coupled to the receiver and the transmitter, whereby the processing circuitry is configured to:
 receive, using the receiver, a handover command message from the source base station at the mobile station; and 
 transmit in a target cell, using the transmitter, a message to the network providing a downlink sequence number status for a packet flow subject to lossless packet switched handover, implicitly acknowledging downlink packets received by the mobile station. 
   
     
     
         8 . The mobile station according to  claim 7 , wherein the mobile station is adapted to receive a transfer of radio link control data blocks in an acknowledged mode. 
     
     
         9 . The mobile station according to  claim 7 , wherein the mobile station is adapted to include the next expected Protocol Data Unit (PDU) to be received in the sequence number status message. 
     
     
         10 . A radio base station (target BSS) adapted to act as a target base station for base station change from a source base station to a target base station in a cellular radio network, wherein a source base station (Source BSS) transfers packet switched communications between a mobile station (MS) and the network, the radio base station comprising:
 a receiver;   a transmitter; and   processing circuitry coupled to the receiver and transmitter, whereby the processing circuitry is configured to:
 receive, using the receiver, a message from the mobile station providing, after reception of a handover command message from the source base station at the mobile station, a downlink sequence number status for a packet flow subject to lossless packet switched handover implicitly acknowledging downlink packets received by the mobile station; and 
 begin sending packets, using the transmitter, to the mobile station from the packet implicitly acknowledged by the mobile station. 
   
     
     
         11 . The radio base station according to  claim 10 , wherein the processing circuitry is further configured to transmit, using the transmitter, radio link control data blocks in an acknowledged mode to the mobile station. 
     
     
         12 . The radio base station according to  claim 10 , wherein the processing circuitry is further configured to include the next expected Protocol Data Unit (PDU) to be received in the sequence number status message.