Inter-Radio Access Technology Handover

Abstract

This document describes methods and devices for a handover of a user equipment (110) from a Fifth Generation (5G) New Radio (NR) base station (121) to an Evolved Universal Terrestrial Radio Access (E-UTRA) base station (122). The user equipment (110) may determine to release or keep a Packet Data Convergence Protocol (PDCP) entity (312) depending on the whether the E-UTRA base station (122) is connected to an Evolved Packet Core (160) network or a Fifth Generation Core (150) network. The user equipment (110) may determine to release or keep the PDCP entity (312) depending based on a received NR Radio Resource Control (RRC) message or E-UTRA RRC message.

What is claimed is: 
     
         1 . A method of performing a handover from a source base station of a first radio access technology to a target base station of a second radio access technology, the method comprising a user equipment:
 communicating with the source base station using a Medium Access Control entity, a Radio Link Control entity, a first Packet Data Convergence Protocol entity and a first Service Data Adaptation Protocol entity;   receiving a first Radio Resource Control message from the source base station, the first Radio Resource Control message including a second Radio Resource Control message for the handover to the target base station;   in response to the receiving the first Radio Resource Control message or the second Radio Resource Control message, releasing the Medium Access Control entity and the Radio Link Control entity;   determining a configuration type from an indication of a configuration type included in the second Radio Resource Control message;   determining that the configuration type is a full configuration; and   based on the determining that the configuration type is the full configuration, releasing the first Packet Data Convergence Protocol entity and the first Service Data Adaptation Protocol entity.   
     
     
         2 . The method of  claim 1 , wherein the target base station is connected to an Evolved Packet Core network, the method further comprising the user equipment:
 determining that the configuration type is a full configuration; and   based on the determining that the configuration type is the full configuration, releasing the first Packet Data Convergence Protocol entity.   
     
     
         3 . The method of  claim 2 , further comprising the user equipment:
 based on the second Radio Resource Control message, establishing a second Packet Data Convergence Protocol entity with the target base station;   transmitting an RRCConnectionConfigurationComplete message; and   communicating with the target base station using the second Packet Data Convergence Protocol entity.   
     
     
         4 . The method of  claim 3 , further comprising the user equipment:
 disconnecting from the source base station.   
     
     
         5 . The method of  claim 1 , wherein the target base station is connected to a fifth-generation core network, the method further comprising the user equipment:
 wherein the communicating with the source base station further comprises using a first Service Data Adaptation Protocol entity;   determining that the configuration type is a full configuration; and   based on the determining that the configuration type is the full configuration, releasing the first Packet Data Convergence Protocol entity and the first Service Data Adaptation Protocol entity.   
     
     
         6 . The method of  claim 5 , further comprising the user equipment:
 based on the second Radio Resource Control message:
 establishing a second a Packet Data Convergence Protocol entity with the target base station; 
 establishing a second Service Data Adaptation Protocol entity with the target base station; 
   transmitting an RRCConnectionConfigurationComplete message; and   communicating with the target base station using the second Packet Data Convergence Protocol entity and the second Service Data Adaptation Protocol entity.   
     
     
         7 . The method of  claim 6 , further comprising the user equipment:
 disconnecting from the source base station.   
     
     
         8 . The method of  claim 1 , wherein the first Radio Resource Control message is an RRCConnectionReconfiguration message. 
     
     
         9 . The method of  claim 8 , wherein the indication of a configuration type is a fullConfig field in the RRCConnectionReconfiguration message. 
     
     
         10 . The method of  claim 1 , wherein the source base station is a fifth-generation new radio base station, and wherein the target base station is an Evolved Universal Terrestrial Radio Access base station. 
     
     
         11 . A user equipment comprising:
 one or more wireless transceivers;   a processor; and   a memory comprising instructions for a handover manager executable by the processor to configure the user equipment to:
 communicate with a source base station using a Medium Access Control entity, a Radio Link Control entity, and a first Packet Data Convergence Protocol entity; 
 receive a first Radio Resource Control message from the source base station, the first Radio Resource Control message including a second Radio Resource Control message for a handover to a target base station; 
 in response to the reception of the first Radio Resource Control message or the second Radio Resource Control message, release the Medium Access Control entity and the Radio Link Control entity; and 
 determine a configuration type from an indication of a configuration type included in the second Radio Resource Control message. 
   
     
     
         12 . The user equipment of  claim 11 , wherein the target base station is connected to an Evolved Packet Core network, and wherein the instructions are executable to configure the user equipment to:
 determine that the configuration type is a full configuration;   based on the determination that the configuration type is the full configuration, release the first Packet Data Convergence Protocol entity;   based on the second Radio Resource Control message, establish a second Packet Data Convergence Protocol entity with the target base station;   transmit an RRCConnectionConfigurationComplete message; and   communicate with the target base station using the second Packet Data Convergence Protocol entity.   
     
     
         13 . The user equipment of  claim 11 , wherein the target base station is connected to a fifth-generation core network, and wherein the instructions are executable to configure the user equipment to:
 communicate with the source base station using the Medium Access Control entity, the Radio Link Control entity, the first Packet Data Convergence Protocol entity, and a first Service Data Adaptation Protocol entity;   determine that the configuration type is a full configuration; and   based on the determination that the configuration type is the full configuration, release the first Packet Data Convergence Protocol entity and the first Service Data Adaptation Protocol entity.   
     
     
         14 . The user equipment of  claim 13 , wherein the instructions are executable to configure the user equipment to:
 based on the second Radio Resource Control message:
 establish a second a Packet Data Convergence Protocol entity with the target base station; 
 establish a second Service Data Adaptation Protocol entity with the target base station; 
   transmit an RRCConnectionConfigurationComplete message; and   communicate with the target base station using the second Packet Data Convergence Protocol entity and the second Service Data Adaptation Protocol entity.   
     
     
         15 . The user equipment of  claim 14 , wherein the instructions are executable to configure the user equipment to:
 disconnect from the source base station.   
     
     
         16 . A method of performing a handover of a user equipment from a source base station of a first radio access technology to a target base station of a second radio access technology, the method comprising the source base station:
 receiving a first Radio Resource Control message indicating a handover of the user equipment to the target base station;   determining a configuration type to be applied to the user equipment during the handover, the configuration type being a full configuration;   generating a second Radio Resource Control message;   including an indication of the configuration type in the second Radio Resource Control message;   including the first Radio Resource Control message in the second Radio Resource Control message; and   transmitting the second Radio Resource Control message to the user equipment to direct the user equipment to modify a current user equipment configuration, based the configuration type during the handover.   
     
     
         17 . The method of  claim 16 , wherein the second Radio Resource Control message is an RRCConnectionReconfiguration message. 
     
     
         18 . The method of  claim 16 , wherein the first Radio Resource Control message is received from the target base station or an Access and Mobility Management Function in a core network. 
     
     
         19 . A base station comprising:
 a wireless transceiver;   a core network interface;   an inter-base station interface; and   a base station manager arranged to configure the base station to:
 receive a first Radio Resource Control message indicating a handover of a user equipment to a target base station; 
 determine a configuration type to be applied to the user equipment during the handover, the configuration type being a full configuration; 
 generate a second Radio Resource Control message; 
 include an indication of the configuration type in the second Radio Resource Control message; 
 include the first Radio Resource Control message in the second Radio Resource Control message; and 
 transmitting the second Radio Resource Control message to the user equipment to direct the user equipment to modify a current user equipment configuration, based the configuration type during the handover. 
   
     
     
         20 . The base station of  claim 19 , wherein the second Radio Resource Control message is an RRCConnectionReconfiguration message; and wherein the first Radio Resource Control message is received from the target base station or an Access and Mobility Management Function in a core network.