Communication device and communication method

Abstract

[Solution] A communication device including: a communication unit configured to perform wireless communication; and a control unit configured to acquire information regarding a communication quality of one or more radio links including at least one of a direct first radio link or a second radio link via a relay terminal, which is configured to be movable, between a remote terminal and a base station, and to switch the radio link to be used in communication between the remote terminal and the base station on the basis of the acquired information regarding the communication quality.

1 . A remote terminal, comprising:
 circuitry configured to:   estimate a communication quality of a sidelink between the remote terminal and a relay terminal;   receive an estimation of a communication quality of a backhaul link between a relay terminal and a base station from the relay terminal;   decide whether a radio link failure condition is present or not based on the estimation of the communication quality of the sidelink and the estimation of the communication quality of the backhaul link; and   on condition that the radio link failure condition is present, conduct a relay reselection or a fallback procedure.   
     
     
         2 . The remote terminal according to  claim 1 , wherein the circuity is further configured to:
 receive a detected radio link failure of the backhaul link from the relay terminal; and   decide whether a radio link failure condition is present or not further based on the detected radio link failure of the backhaul link.   
     
     
         3 . The remote terminal according to  claim 1 , wherein the circuitry is configured to determine end to end radio link failure based on the estimation of the communication quality of the sidelink and the estimation of the communication quality of the backhaul link. 
     
     
         4 . The remote terminal according to  claim 1 , wherein the circuity is further configured to measure the communication quality of the sidelink using a threshold value. 
     
     
         5 . The remote terminal according to  claim 4 , wherein the threshold value is preconfigured in the remote terminal. 
     
     
         6 . The remote terminal according to  claim 4 , wherein the circuitry is configured to receive the threshold value from the relay terminal or the base station. 
     
     
         7 . The remote terminal according to  claim 1 , wherein the circuitry is configured to receive an event trigger from the relay terminal or the base station and send the estimation of the communication quality of the sidelink in response to the event trigger. 
     
     
         8 . The remote terminal according to  claim 1 , wherein the fallback procedure includes fallback handover or fallback reselection. 
     
     
         9 . A relay terminal, comprising:
 circuitry configured to:   estimate a communication quality of a backhaul link to a base station on the basis of a threshold value;   send the estimation of the communication quality of the backhaul link to a remote terminal;   decide whether a radio link failure condition is present or not based on the estimation of the communication quality of the backhaul link; and   on condition that the radio link failure condition is present, conduct a relay reselection or a fallback procedure.   
     
     
         10 . The relay terminal according to  claim 9 , wherein the circuitry is further configured to estimate a communication quality of a sidelink between the relay terminal and the remote terminal and decide whether a radio link failure condition is present or not further based on the communication quality of the sidelink. 
     
     
         11 . The relay terminal according to  claim 9 , wherein the circuitry is configured to quantize the communication quality of the backhaul link and send the quantized value to the remote terminal as the communication quality of the backhaul link. 
     
     
         12 . The relay terminal according to  claim 9 , wherein the circuitry is configured to send the estimation of the communication quality of the backhaul link only on condition that the estimation of the communication quality of the backhaul link exceeds the threshold value. 
     
     
         13 . The relay terminal according to  claim 9 , wherein the fallback procedure includes fallback handover or fallback reselection. 
     
     
         14 . The relay terminal according to  claim 9 , wherein the circuitry is configured to detect a radio link failure condition of the backhaul link using a timer. 
     
     
         15 . The relay terminal according to  claim 14 , wherein a value of the timer is different than that used to detect a radio link failure condition of a downlink. 
     
     
         16 . The relay terminal according to  claim 9 , wherein the threshold value is preconfigured in the relay terminal. 
     
     
         17 . The relay terminal according to  claim 9 , wherein the circuitry is configured to receive the threshold value from the base station. 
     
     
         18 . The relay terminal according to  claim 9 , wherein the circuitry is configured to serve as a switch source for the relay reselection. 
     
     
         19 . The relay terminal according to  claim 9 , wherein the circuitry is configured to receive a target relay from the base station for the relay reselection.