Method for Performing Packet Switched Handover in a Mobile Communication System

Abstract

A method and system for performing packet switched handover in a mobile communication network. The system includes a mobile node, a first and a second packet switching node. The method enables the parallel sending of logical link layer frames from the first and the second packet switching node. This is achieved so that the mobile node does not reject incoming frames received from two logical link layer entities having different states. The benefits of the invention are related to improved quality of service and the avoiding of gaps in received data during handover.

What is claimed is: 
     
         1 . A method of performing packet switched handover in a mobile communication network, comprising a mobile node, a first and a second packet switching node, the method comprising:
 forming a first logical link layer entity in the mobile node; and   detecting a handover condition in the mobile node;   receiving at least one ciphering parameter from the first packet switching node to the second packet switching node when the first packet switching node requests handover preparation from the second packet switching node;   forming a second logical link layer entity in the mobile node;   sending logical link layer frames from the first and second packet switching nodes to the mobile node during handover;   detecting a handover completion; and   renegotiating logical link layer parameters between the mobile node and the second packet switching node after the detecting of the handover completion when the logical link layer parameters are not suitable.   
     
     
         2 . The method according to  claim 1 , further comprising:
 removing the first logical link layer entity in the mobile node after the detecting of the handover completion.   
     
     
         3 . The method according to  claim 1 , further comprising:
 utilizing a General Packet Radio Service (GPRS) network as the mobile communication network, serving GPRS Support Nodes (SGSN) as the first and second packet switching nodes, and GPRS Logical Link Control (LLC) as at least one of the first and the second the logical link layer.   
     
     
         4 . An apparatus comprising at least one processor and a memory including computer program code, the memory and the computer program code configured to, with the at least one processor, direct the apparatus at least to:
 cause communications with a remote packet switching node, prior to receiving a data packet stream that is routed from the remote packet switching node as a result of a handover to the remote packet switching node, to receive an indication of a packet-switched handover condition associated with a mobile node, to request packet-switched handover preparation, to send logical link layer information, and to receive logical link layer information;   form a first logical link layer control entity in response to connection establishment and a second logical link layer control entity in response to a packet-switched handover condition;   detect the packet-switched handover condition and a packet-switched handover completion; and   cause the second logical link layer control entity to be configured to renegotiate logical link layer parameters with a packet switched node after the packet-switched handover completion when the logical link layer parameters are not suitable.   
     
     
         5 . The apparatus according to  claim 4 , wherein being directed to form the second logical link layer control entity includes being directed to perform the logical link parameter renegotiation using exchange identification (XID) negotiation. 
     
     
         6 . A method of performing packet switched handover in a mobile communication network comprising a mobile node, a first and a second packet switching node, the method comprising:
 detecting a handover condition associated with the mobile node in the first packet switching node;   requesting handover preparation by the first packet switching node from the second packet switching node,   receiving at least one ciphering parameter from the first packet switching node to the second packet switching node when the first packet switching node requests handover preparation from the second packet switching node;   receiving a packet at the first packet switching node;   forming a logical link layer Protocol Data Unit (PDU) from data in the packet;   sending a first frame containing the logical link layer Protocol Data Unit (PDU) to the mobile node from the first packet switching node;   sending the logical link Protocol data Unit (PDU) from the first packet switching node to the second packet switching node; and   sending a second frame containing the logical link layer Protocol Data Unit (PDU) to the mobile node from the second packet switching node.   
     
     
         7 . The method according to  claim 6 , further comprising:
 utilizing a General Packet Radio Service (GPRS) network as the mobile communication network, Serving GPRS Support Nodes (SGSN) as the first and second packet switching nodes, and GPRS Logical Link Control (LLC) as a logical link layer.   
     
     
         8 . The method according to  claim 7 , further comprising:
 utilizing a General Packet Radio Service (GPRS) network as the mobile communication network, a Serving GPRS Support Node (SGSN) as the first packet switching node, a Base Station Subsystem (BSS) node as the second packet switching node, and GPRS Logical Link Control (LLC) as the logical link layer.