Mobile communication system

Abstract

A radio base station includes a mobile communication system, a first relay node and a radio base station connected via a radio bearer, a second relay node and a radio base station connected via a radio bearer, and a mobile station configured to conduct a handover process between a first and second state. In the first state a radio bearer is established with the first relay node in order to communicate via the first relay node and the radio base station. In the second state a radio bearer is established with the second relay node in order to communicate via the second relay node and the radio base station. The mobile station is configured such that control signals are transmitted and received via the radio bearer between the first relay node and the radio base station, via the radio bearer between the second relay node and the radio base station.

1 .- 3 . (canceled) 
     
     
         4 . A handover method in which when a first relay node and a radio base station are connected via a radio bear and a second relay node and the radio base station are connected via a radio bear, a mobile station is switched from a first state where the radio bearer is established with the first relay node in order to communicate via the first relay node and the radio base station to a second state where the radio bearer is established with the second relay node in order to communicate via the second relay node and the radio base station, the handover method comprising:
 a step in which the first relay node transmits a handover request signal to the radio base station;   a step in which the radio base station transmits the handover request signal to the second relay node;   a step in which the second relay node transmits a handover request confirmation signal to the radio base station;   a step in which the radio base station transmits a handover request confirmation signal to the first relay node; and   a step in which the first relay node transmits a handover instruction signal to instruct to hand over to the second relay node, to the mobile station.   
     
     
         5 . A mobile communication system in which a first relay node and a radio base station are connected via a radio bearer and a second relay node and the radio base station are connected via a radio bearer,
 wherein the first relay node and the second relay node comprise: as a radio bearer function of setting a Un interface with the second relay node, and the radio base station, a physical layer function; an MAC layer function provided as an upper layer function of the physical layer function; an RLC layer function provided as an upper layer function of the MAC layer function; a PDCP layer function provided as an upper layer function of the RLC layer function; and an RRC layer function provided as an upper layer function of the PDCP layer function,   wherein the first relay node and the second relay node comprise: an IP layer function as an upper layer function of the radio bearer function; an SCTP layer function provided as an upper layer function of the IP layer function; and an X2AP layer function provided as an upper layer function of the SCTP layer function,   wherein the radio base station comprises: as a radio bearer function of setting a Un interface with the first relay node and the second relay node, a physical layer function; an MAC layer function provided as an upper layer function of the physical layer function; an RLC layer function provided as an upper layer function of the MAC layer function; a PDCP layer function provided as an upper layer function of the RLC layer function; and an RRC layer function provided as an upper layer function of the PDCP layer function,   wherein the radio base station comprises: an IP layer function as an upper layer function of the radio bearer function; an SCTP layer function provided as an upper layer function of the IP layer function; and an X2AP layer function provided as an upper layer function of the SCTP layer function, and   wherein a control signal relating to a handover process is configured to terminate between the X2AP layer function of the first relay node and the second relay node, and the X2AP layer function of the radio base station.