Handover handling

Abstract

A method performed in a telecommunication system. At a source node, receiving, a sequence of PDCP SDUs for transmission to a device, appending a sequence number to each PDCP SDU, storing and ciphering the PDCP SDUs, passing the ciphered PDCP SDUs to an Outer ARQ entity for segmentation, generating Outer ARQ segments, generating and appending a respective Outer ARQ header to each Outer ARQ segment to generate a corresponding Outer ARQ PDU, sending the generated Outer ARQ PDUs to the device, and sending a request to a target node. At the target node, receiving the request and sending a response to the source node. At the source node, receiving the response, sending a command to the device, and forwarding stored PDCP SDUs with their appended sequence number to the target node. At a target node, receiving PDCP SDUs, from the source node and sending to a device, Outer ARQ PDUs.

1 . A method performed in a telecommunication system, the method comprising:
 at a source node:
 receiving, a sequence of PDCP Service Data Units (SDUs), for transmission to a mobile communication device; 
 appending a sequence number to each PDCP SDU; 
 storing a copy of the PDCP SDUs; 
 ciphering the PDCP SDUs; 
 passing the ciphered PDCP SDUs with appended sequence numbers to an Outer ARQ entity for segmentation; 
 segmenting the ciphered PDCP SDUs with appended sequence numbers to generate Outer ARQ segments; 
 generating and appending a respective Outer ARQ header to each Outer ARQ segment to generate a corresponding Outer ARQ Protocol Data Unit (PDU) comprising a sequence number; 
 sending the generated Outer ARQ PDUs to the mobile communication device; and 
 sending a handover request to a target node; 
   at the target node:
 receiving the handover request from the source node and sending a handover response to the source node in response to the handover request; 
   at the source node:
 receiving the handover response from the target node; 
 sending a handover command to the mobile communication device; and 
 forwarding stored PDCP SDUs with their appended sequence number to the target node; and 
   at a target node:
 receiving PDCP SDUs, from the source node and sending from the target node to a mobile communication device, Outer ARQ PDUs corresponding to the PDCP SDUs received from the source node. 
   
     
     
         2 . A source node of a telecommunication system, the source node comprising:
 a PDCP entity that:
 receives a sequence of PDCP Service Data Units (SDUs) for transmission to a mobile communication device; 
 appends a sequence number to each PDCP SDU; 
   stores a copy of the PDCP SDUs;
 ciphers the PDCP SDUs; and 
 passes the ciphered PDCP SDUs with appended sequence numbers to an Outer ARQ entity for segmentation; 
   wherein the Outer ARQ entity is configured to:
 segment the ciphered PDCP SDUs with appended sequence numbers to generate Outer ARQ segments; and 
 generate and append a respective Outer ARQ header to each Outer ARQ segment to generate a corresponding Outer ARQ Protocol Data Unit (PDU) comprising a sequence number, and 
   wherein the source node further comprises:
 a transceiver that sends the generated Outer ARQ PDUs to the mobile communication device; and 
 a handover module that:
 sends a handover request to a target node; 
 receives a handover response from the target node; 
 sends a handover command to the mobile communication device; and 
 forwards stored PDCP SDUs with their appended sequence number to the target node. 
 
   
     
     
         3 . A source node according to  claim 2 , wherein the Outer ARQ entity is further configured to receive uplink Outer ARQ PDUs from the mobile communication device, to remove an Outer ARQ header from each received Outer ARQ PDU and to concatenate received ARQ PDUs to form PDCP SDUs with sequence number. 
     
     
         4 . A source node according to  claim 3 , wherein the PDCP entity is configured to buffer out-of-sequence PDCP SDUs received from the mobile communication device. 
     
     
         5 . A source node according to  claim 4 , wherein the handover module is configured to forward, in response to receiving the handover response from a target node, buffered out-of-sequence uplink PDCP SDUs to the target node. 
     
     
         6 . A target node of a telecommunication system, the target node comprising:
 a handover module that:
 receives a handover request from a source node; and 
 sends a handover response to the source node; 
   a PDCP entity that receives PDCP Service Data Units (SDUs) from a source communication node; and   a transceiver that sends, to a mobile communication device, Outer ARQ Protocol Data Units (PDUs) corresponding to the PDCP SDUs received from the source node.   
     
     
         7 . A target node according to  claim 6 , further comprising an Outer ARQ entity that receives uplink Outer ARQ PDUs from the mobile communication device, that removes an Outer ARQ header from each received Outer ARQ PDU and that concatenates received ARQ PDUs to form PDCP SDUs with sequence number. 
     
     
         8 . A target node according to  claim 7 , wherein the PDCP entity is configured to receive out-of-sequence uplink PDCP SDUs from the source node after the handover response is sent to the source node. 
     
     
         9 . A target node according to  claim 8 , wherein the PDCP entity is configured to reorder the uplink PDCP SDUs formed from the received uplink Outer ARQ PDUs, and the uplink out-of-sequence PDCP SDUs received from the source node, and to forward them in sequence to a telecommunication network. 
     
     
         10 . A target node according to  claim 9 , comprising a network interface that communicates the PDCP SDUs to the telecommunication network over an S1 interface. 
     
     
         11 . A mobile communication device comprising:
 a Outer ARQ entity that receives Outer ARQ PDUs from a source node; and   a handover module that receives a handover command from the source node,   wherein the source node comprises the source node according to  claim 2 ,   wherein the Outer ARQ entity is configured, after receiving said handover command, to receive Outer ARQ PDUs from the target node, and   wherein the target node comprises:
 a handover module that:
 receives a handover request from a source node; and 
 sends a handover response to the source node; 
 
 a PDCP entity that receives PDCP SDUs from a source communication node; and 
 a transceiver that sends, to a mobile communication device, Outer ARQ PDUs corresponding to the PDCP SDUs received from the source node. 
   
     
     
         12 . A telecommunication system comprising:
 a source node according to  claim 2 ;   a target node comprising:
 a handover module that: 
 receives a handover request from the source node; and 
 sends a handover response to the source node; 
   a PDCP entity that receives PDCP SDUs from a source communication node; and   a transceiver that sends, to a mobile communication device, Outer ARQ PDUs corresponding to the PDCP SDUs received from the source node; and   a mobile communication device comprising:   the Outer ARQ entity that receives Outer ARQ PDUs from the source node; and   a handover module that receives a handover command from the source node,   wherein the Outer ARQ entity is configured, after receiving the handover command, to received the Outer ARQ PDUs from the target node.   
     
     
         13 . A communication method performed by a source node of a telecommunication system, the method comprising:
 receiving a sequence of PDCP Service Data Units (SDUs) for transmission to a mobile communication device;   appending a sequence number to each PDCP SDU;   storing a copy of the PDCP SDUs;   ciphering the PDCP SDUs;   passing the ciphered PDCP SDUs with appended sequence numbers to an Outer ARQ entity for segmentation;   segmenting the ciphered PDCP SDUs with appended sequence numbers to generate Outer ARQ segments;   generating and appending a respective Outer ARQ header to each Outer ARQ segment to generate a corresponding Outer ARQ Protocol Data Unit (PDU) comprising a sequence number;   sending the generated Outer ARQ PDUs to the mobile communication device;   sending a handover request to a target node;   receiving a handover response from the target node;   sending a handover command to the mobile communication device; and   forwarding stored PDCP SDUs with their appended sequence number to the target node.   
     
     
         14 . A communication method performed by a target node of a telecommunication system, the method comprising:
 receiving a handover request from a source node;   sending a handover response to the source node;   receiving downlink PDCP Service Data Units (SDUs) from the source node; and   sending, to a mobile communication device, Outer ARQ Protocol Data Units (PDUs) corresponding to the PDCP SDUs received from the source node.   
     
     
         15 . A method performed by a mobile communication device, the method comprising:
 receiving Outer ARQ PDUs from the source node operating according to  claim 13 ;   receiving a handover command from the source node;   after receiving said handover command, receiving Outer ARQ PDUs from a target node,   wherein the receiving Outer ARQ PDUs from a target node comprises:
 sending a handover response to the source node; 
 receiving downlink PDCP SDUs from the source node; and 
 sending, to a mobile communication device, Outer ARQ PDUs corresponding to the PDCP SDUs received from the source node. 
   
     
     
         16 . A source node of a telecommunication system, the source node comprising:
 a receiver for receiving a sequence of PDCP Service Data Units (SDUs) for transmission to a mobile communication device;   a circuit for appending a sequence number to each PDCP SDU;   a memory for storing a copy of the PDCP SDUs;   a ciphering module for ciphering the PDCP SDUs;   a passing module for passing the ciphered PDCP SDUs with appended sequence numbers to an Outer ARQ entity for segmentation;   a segmenting module for segmenting the ciphered PDCP SDUs with appended sequence numbers to generate Outer ARQ segments;   a generating and appending module for generating and appending a respective Outer ARQ header to each Outer ARQ segment to generate a corresponding Outer ARQ Protocol Data Unit (PDU) comprising a sequence number;   a transmitter for sending the generated Outer ARQ PDUs to the mobile communication device;   a sending module for sending a handover request to a target node;   a receiving module for receiving a handover response from the target node;   a handover command sending module for sending a handover command to the mobile communication device; and   a forwarding module for forwarding stored PDCP SDUs with their appended sequence number to the target node.   
     
     
         17 . A target node of a telecommunication system, the target node comprising:
 a receiver for receiving a handover request from a source node;   a transmitter for sending a handover response to the source node;   a PDCP Service Data Units (SDUs) receiver for receiving PDCP SDUs from a source communication node; and   an Outer ARQ Protocol Data Units (PDUs) transmitter for sending, to a mobile communication device, Outer ARQ PDUs corresponding to the PDCP SDUs received from the source node.