# US 2014/0153541 A1 · Method and system for base station change of packet switched communications in a mobile communications system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0153541 A1 - Document ID: US20140153541A1 - Status: Published application - Kind: A1 - Application number: 14/062,585 - Filed: 2013-10-24 - Published: 2014-06-05 - Earliest claimed: 2004-01-28 - Assignees: Telefonaktiebolaget L M Ericsson (publ) - Applicants: Telefonaktiebolaget L M Ericsson (Publ) - Inventors: Ingemar Backlund; Gunnar Mildh; John Diachina; Lars Tedenvall - Web page: https://patentgrep.com/patent/US20140153541A1 ## CPC - H04W 36/0016: {Hand-off preparation specially adapted for end-to-end data sessions} - H04W 36/02: Buffering or recovering information during reselection {; Modification of the traffic flow during hand-off} - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) ## Abstract A mobile station (MS) and method for base station handover from a source cell of a source base station to a target cell of a target base station in a packet-switched cellular radio network. While the MS is still in the source cell, the MS receives from the network, a handover command message and information regarding a next expected uplink packet for a packet flow subject to lossless packet-switched handover. Upon arrival of the MS in the target cell, the MS transmits an uplink sequence number status message to the target base station providing a downlink sequence number status for the packet flow, and starts uplink data transmission to the target base station beginning with the next expected uplink packet. ## Claims ### Claim at position 1 1-177. (canceled) ### Claim 178 A method in a mobile station (MS) for base station handover from a source cell of a source base station to a target cell of a target base station in a cellular radio network, wherein the base stations transfer packet switched communications between the mobile station and the network, the method comprising the steps of: while the MS is still in the source cell: receiving from the network, a handover command message ordering the MS to connect to the target cell; and receiving from the network, information regarding a next expected uplink packet for a packet flow subject to lossless packet switched handover; and upon arrival of the MS in the target cell, transmitting an uplink sequence number status message to the target base station providing a downlink sequence number status for the packet flow subject to lossless packet switched handover, and starting uplink data transmission to the target base station beginning with the next expected uplink packet. ### Claim 179 (depends on 178) The method according to claim 178, wherein the mobile station also receives a transfer of radio link control data blocks in an acknowledged mode. ### Claim 180 (depends on 178) The method according to claim 178, wherein the sequence number status message transmitted to the target base station includes a sequence number of the next expected Protocol Data Unit (PDU) to be received by the mobile station. ### Claim 181 (depends on 178) The method according to claim 178, wherein the mobile station receives lower layer packet acknowledgements, and the step of starting uplink data transmission includes starting uplink data transmission in the target cell beginning with the next uplink packet that was not acknowledged by lower layers in the source cell. ### Claim 182 A mobile station (MS) configured to be handed over from a source cell of a source base station to a target cell of a target base station in a cellular radio network, wherein the base stations transfer packet switched communications between the mobile station and the network, the mobile station comprising: a receiver configured to: receive, while the MS is still in the source cell, a handover command message from the network ordering the MS to connect to the target cell: and receive, while the MS is still in the source cell, information regarding a next expected uplink packet for a packet flow subject to lossless packet switched handover; and a transmitter configured to: transmit an uplink message to the target base station when the mobile station arrives in the target cell, the uplink message providing a downlink sequence number status for the packet flow subject to lossless packet switched handover; and start uplink data transmission to the target base station beginning with the next expected uplink packet. ### Claim 183 (depends on 182) The mobile station according to claim 182, wherein the mobile station is configured to receive a transfer of radio link control data blocks in an acknowledged mode. ### Claim 184 (depends on 182) The mobile station according to claim 182, wherein the mobile station is configured to include in the uplink message, the next expected Protocol Data Unit (PDU) to be received. ### Claim 185 A method in a mobile station (MS) for base station handover from a source cell of a source base station to a target cell of a target base station in a cellular radio network, wherein the base stations transfer packet switched communications between the mobile station and the network, the method comprising the steps of: while the MS is still in the source cell, receiving from the network, a handover command message ordering the MS to connect to the target cell; and upon arrival in the target cell, starting uplink data transmission to the target base station beginning with a next expected uplink packet. ### Claim 186 (depends on 185) The method according to claim 185, wherein the mobile station receives lower layer packet acknowledgements, and the step of starting uplink data transmission includes starting uplink data transmission in the target cell beginning with the next up-link packet that was not acknowledged by lower layers in the source cell. ### Claim 187 (depends on 185) The method according to claim 185, further comprising, after receiving the handover command message, the step of estimating by the MS, the next expected uplink packet for a packet flow subject to lossless packet switched handover, wherein the estimated next expected uplink packet is the first uplink packet sent by the MS in the source cell that was not acknowledged in the source cell. ### Claim 188 (depends on 185) The method according to claim 185, wherein the step of starling uplink data transmission includes starting the uplink data transmission before receiving any sequence number status message from the target base station. ### Claim 189 A mobile station (MS) configured to be handed over from a source cell of a source base station to a target cell of a target base station in a cellular radio network, wherein the base stations transfer packet switched communications between the mobile station and the network, the mobile station comprising: a receiver configured to receive a handover command message from the network ordering the MS to connect to the target cell; and a transmitter configured to transmit uplink packets to the target base station beginning with a next expected uplink packet. ### Claim 190 (depends on 189) The mobile station according to claim 189, wherein the mobile station receives lower layer packet acknowledgements, and the transmitter is configured to start uplink data transmission in the target cell beginning with the next up-link packet that was not acknowledged by lower layers in the source cell. ### Claim 191 (depends on 189) The mobile station according to claim 189, wherein the processor is further configured to estimate the next expected uplink packet for a packet flow subject to lossless packet switched handover, wherein the estimated next expected uplink packet is the first uplink packet sent by the MS in the source cell that was not acknowledged in the source cell. ### Claim 192 (depends on 189) The mobile station according to claim 189, wherein the transmitter is configured to start the uplink data transmission before receiving any sequence number status message from the target base station.