Radio communication system, base station apparatus, radio terminal and communication control method

Abstract

A radio communication system includes a first base station (11) that manages a first cell (110), a second base station (12) that manages a second cell (120), and a radio terminal (2). The radio terminal (2) supports dual connectivity involving a bearer split in which a first network bearer between the radio terminal (2) and a core network (3) is split over the first base station (11) and the second base station (12). The first base station (11) receives, from the second base station (12), bearer split status information about communication of the first network bearer in the second base station (12), and performs control of an access stratum related to the first network bearer. It is thus possible to contribute, for example, to an improvement in control of an access stratum when dual connectivity involving a bearer split is performed.

1 . A base station apparatus comprising:
 a memory; and   at least one hardware processer coupled to the memory and configured to execute modules comprising a communication controller configured to control dual connectivity involving a bearer split in which a first network bearer between a radio terminal and a core network is split over the base station apparatus and a neighbor base station,   wherein the communication controller is configured to receive, from the neighbor base station, bearer split status information about communication of the first network bearer in the neighbor base station, and to perform control of an access stratum related to the first network bearer.   
     
     
         2 . The base station apparatus according to  claim 1 , wherein the control of the access stratum includes control of a Logical Channel Prioritization (LCP) procedure for generating, in the radio terminal, at least one of a first Medium Access Control Protocol Data Unit (MAC PDU) for uplink transmission in a first cell managed by the base station apparatus and a second MAC PDU for uplink transmission in a second cell managed by the neighbor base station. 
     
     
         3 . The base station apparatus according to  claim 2 , wherein the control of the LCP procedure includes at least one of adjusting a Prioritized Bit Rate (PBR) applied to an uplink logical channel of the first network bearer and adjusting a PBR applied to an uplink logical channel of a second network bearer transmitted via the first cell without being subjected to the bearer split. 
     
     
         4 . The base station apparatus according to  claim 1 , wherein the control of the access stratum includes uplink transmission power control of at least one of a first cell managed by the base station apparatus and a second cell managed by the neighbor base station. 
     
     
         5 . The base station apparatus according to  claim 4 , wherein the uplink transmission power control includes at least one of adjusting maximum transmission power allowed for the radio terminal in the first cell and adjusting maximum transmission power allowed for the radio terminal in the second cell. 
     
     
         6 . The base station apparatus according to  claim 1 , wherein the control of the access stratum includes control of downlink scheduling in at least one of a first cell managed by the base station apparatus and a second cell managed by the neighbor base station. 
     
     
         7 . The base station apparatus according to  claim 6 , wherein the control of the downlink scheduling includes at least one of adjusting a Prioritized Bit Rate (PBR) applied to a downlink logical channel of the first network bearer and adjusting a PBR applied to a downlink logical channel of a second network bearer transmitted via the first cell without being subjected to the bearer split. 
     
     
         8 . The base station apparatus according to  claim 1 , wherein the bearer split status information includes at least one of communication status information, radio resource control information, and admission control information. 
     
     
         9 . The base station apparatus according to  claim 8 , wherein
 the bearer split status information includes the communication status information indicating a communication status of the first network bearer in the neighbor base station, and   the communication status information indicates at least one of statistics of throughput, statistics of allocated radio resources, statistics of packet losses, statistics of power headroom, and information about retransmission control in a Radio Link Control (RLC) sublayer.   
     
     
         10 . The base station apparatus according to  claim 8 , wherein
 the bearer split status information includes the radio resource control information relating to radio resources used in a cell managed by the neighbor base station for the first network bearer, and   the radio resource control information indicates at least one of information about an increase or decrease in radio resources, information about available radio resources, and information about surplus radio resources.   
     
     
         11 . The base station apparatus according to  claim 8 , wherein
 the bearer split status information includes the admission control information relating to admission, executed in a cell managed by the neighbor base station, on data of the first network bearer, and   the admission control information indicates at least one of information about whether or not to admit a new bearer split, information about a wait time until a new bearer split is acceptable, information about a wait time until a request for a new bearer split is made, information about expected throughput, and information about an expected amount of radio resources to be allocated.   
     
     
         12 . A base station apparatus comprising:
 a memory; and   at least one hardware processer coupled to the memory and configured to execute modules comprising a communication controller configured to control dual connectivity involving a bearer split in which a first network bearer between a radio terminal and a core network is split over the base station apparatus and a neighbor base station, wherein   the communication controller is configured to send, to the neighbor base station, bearer split status information about communication of the first network bearer in the base station apparatus, and   the bearer split status information triggers the neighbor base station to perform control of an access stratum related to the first network bearer.   
     
     
         13 . The base station apparatus according to  claim 12 , wherein the control of the access stratum includes control of a Logical Channel Prioritization (LCP) procedure for generating, in the radio terminal, at least one of a first Medium Access Control Protocol Data Unit (MAC PDU) for uplink transmission in a first cell managed by the neighbor base station and a second MAC PDU for uplink transmission in a second cell managed by the base station apparatus. 
     
     
         14 . The base station apparatus according to  claim 12 , wherein the control of the access stratum includes uplink transmission power control of at least one of a first cell managed by the neighbor base station and a second sell managed by the base station apparatus. 
     
     
         15 . The base station apparatus according to  claim 12 , wherein the control of the access stratum includes control of downlink scheduling in at least one of a first cell managed by the neighbor base station and a second cell managed by the base station apparatus. 
     
     
         16 . The base station apparatus according to  claim 12 , wherein the bearer split status information includes at least one of communication status information, radio resource control information, and admission control information. 
     
     
         17 . The base station apparatus according to  claim 16 , wherein
 the bearer split status information includes the communication status information indicating a communication status of the first network bearer in the base station apparatus, and   the communication status information indicates at least one of statistics of throughput, statistics of allocated radio resources, statistics of packet losses, statistics of power headroom, and information about retransmission control in a Radio Link Control (RLC) sublayer.   
     
     
         18 . The base station apparatus according to  claim 16 , wherein
 the bearer split status information includes the radio resource control information relating to radio resources used in a cell managed by the base station apparatus for the first network bearer, and   the radio resource control information indicates at least one of information about an increase or decrease in radio resources, information about available radio resources, and information about surplus radio resources.   
     
     
         19 . The base station apparatus according to  claim 16 , wherein
 the bearer split status information includes the admission control information relating to admission, executed in a cell managed by the base station apparatus, on data of the first network bearer, and   the admission control information indicates at least one of information about whether or not to admit a new bearer split, information about a wait time until a new bearer split is acceptable, information about a wait time until a request for a new bearer split is made, information about expected throughput, and information about an expected amount of radio resources to be allocated.   
     
     
         20 . A communication control method comprising:
 starting, by a first base station, communication of dual connectivity involving a bearer split in which a first network bearer between a radio terminal and a core network is split over the first base station and a second base station;   receiving, by the first base station from the second base station, bearer split status information about communication of the first network bearer in the second base station, and performing, by the first base station, control of an access stratum related to the first network bearer.