Overhead reduction in reconfigurable intelligent surface (RIS)-aided ultra-reliable and low latency (URLLC) systems
Methods and apparatuses for reducing the overhead in RIS-aided URLLC system are disclosed. A method comprises determining, by applying delay outage rate (DOR) metric, an active number of reflecting elements at an RIS between the base station and a UE in an RIS-aided URLLC system; and setting the active number of reflecting elements to the RIS.
1 . A method performed by a base station, the method comprising:
determining, by applying a delay outage rate (DOR) metric, an active number of reflecting elements at a reconfigurable intelligent surface (RIS) between the base station and a user equipment (UE) in an RIS-aided ultra-reliable low latency communications (URLLC) system;
receiving from the UE statistics of a received signal-to-noise ratio (SNR) over a cascaded channel, wherein, the statistics include a cumulative density function (CDF) of the received SNR; and
setting the active number of reflecting elements to the RIS,
wherein applying the DOR metric includes determining the active number of reflecting elements using the CDF of the received SNR.
2 . The method of claim 1 , wherein, a direct channel blocking or a deep fading is between the base station and the UE, and the cascaded channel exists between the base station and the UE via the RIS.
3 . The method of claim 1 , wherein, the active number of reflecting elements at the RIS is determined when the DOR metric is below a threshold DOR value.
4 . A base station, comprising:
at least one memory; and
at least one processor coupled with the at least one memory and configured to cause the base station to:
determine, by applying a delay outage rate (DOR) metric, an active number of reflecting elements at a reconfigurable intelligent surface (RIS) between the base station and a user equipment (UE) in an RIS-aided ultra-reliable low latency communications (URLLC) system;
receive, from the UE, statistics of a received signal-to-noise ratio (SNR) over a cascaded channel, wherein, the statistics include a cumulative density function (CDF) of the received SNR; and
set an active number of reflecting elements to the RIS,
wherein applying the DOR metric includes determining the active number of reflecting elements using the CDF of the received SNR.
5 . The base station of claim 4 , wherein, a direct channel blocking or a deep fading is between the base station and the UE, and the cascaded channel exists between the base station and the UE via the RIS.
6 . The base station of claim 4 , wherein, the active number of reflecting elements at the RIS is determined when the DOR metric is below a threshold DOR value.