Clustering of RIS elements

1 . An apparatus for wireless communication at a user equipment (UE), comprising:

a memory; and

at least one processor coupled to the memory and configured to:

receive, from a reconfigurable intelligent surface (RIS) controller, a cluster configuration of a RIS comprising a plurality of clusters,

wherein the cluster configuration further comprises activation of a random selection of one or more clusters based on a first probability p1,

wherein activation of one or more active elements within a respective one of the random selection of the one or more clusters is based on a second probability p2;

perform a beam training procedure on the plurality of clusters of the RIS, the beam training procedure including transmission of a sequence of a plurality of reference signals to each cluster of the plurality of clusters;

transmit, to a base station, a feedback indication indicating an optimal configuration for each cluster of the plurality of clusters based at least on the beam training procedure; and

receive a downlink signal reflected by a set or group of clusters of the RIS from the base station.

2 . The apparatus of claim 1 , further comprising a transceiver coupled to the at least one processor.

3 . The apparatus of claim 1 , wherein the at least one processor is further configured to:

select the set or group of clusters of the plurality of clusters; and

perform a second beam training procedure on the selected set or group of clusters using a sequence of reference signals.

4 . The apparatus of claim 1 , wherein the selected set or group of clusters is based on at least one of signal strength, signal to noise ratio (SNR), signal to interference plus noise ratio (SINR), modulation and coding scheme (MCS), channel quality indicator (CQI), reference signal received power (RSRP), reference signal received quality (RSRQ), or a combination thereof.

5 . The apparatus of claim 1 , wherein each cluster of the plurality of clusters comprises a plurality of active elements, wherein a weight is applied to each of the plurality of active elements of each cluster.

6 . The apparatus of claim 1 , wherein if two or more clusters of the plurality of clusters are simultaneously activated, the at least one processor is further configured to:

receive, from the RIS controller, a second plurality of reference signals corresponding to each of the two or more clusters of the plurality of clusters, wherein the second plurality of reference signals further refine corresponding weights for each of the two or more clusters of the plurality of clusters.

7 . The apparatus of claim 1 , wherein the at least one processor is further configured to:

transmit an indication of at least one selected set or group of clusters of the plurality of clusters based at least on the beam training procedure, wherein the at least one selected set or group of clusters of the plurality of clusters is configured via radio resource control (RRC), medium access control-control element (MAC-CE), or downlink control information (DCI).

8 . The apparatus of claim 1 , wherein a number of clusters within the plurality of clusters of the RIS is adjusted based on at least one of a link between the UE and the RIS, an application type, a bandwidth part, component carriers, frequency band and range, or a combination thereof.

9 . The apparatus of claim 1 , wherein the set or group of clusters of the plurality of clusters is activated for a period of time, wherein the cluster configuration indicates an amount of reference signals to perform the beam training procedure based at least on a number of active elements within each cluster.

10 . An apparatus for wireless communication at a base station, comprising:

a memory; and

at least one processor coupled to the memory and configured to:

receive, from a reconfigurable intelligent surface (RIS) controller, a cluster configuration of the RIS comprising a plurality of clusters,

wherein the cluster configuration further comprises activation of a random selection of one or more clusters based on a first probability p1,

wherein activation of one or more active elements within a respective one of the random selection of the one or more clusters is based on a second probability p2;

perform a beam training procedure on the plurality of clusters of the RIS, the beam training procedure including transmission of a sequence of a plurality of reference signals to each cluster of the plurality of clusters;

select a set or group of clusters of the plurality of clusters of the RIS based at least on the beam training procedure; and

transmit, to the selected set or group of clusters of the RIS, a downlink signal for reflection to a user equipment (UE).

11 . The apparatus of claim 10 , further comprising a transceiver coupled to the at least one processor.

12 . The apparatus of claim 10 , wherein the at least one processor is further configured to:

performing a second beam training procedure on the selected set or group of clusters using a sequence of reference signals.

13 . The apparatus of claim 10 , wherein the selected set or group of clusters is based on at least one of signal strength, signal to noise ratio (SNR), signal to interference plus noise ratio (SINR), modulation and coding scheme (MCS), channel quality indicator (CQI), reference signal received power (RSRP), reference signal received quality (RSRQ), or a combination thereof.

14 . The apparatus of claim 10 , wherein each cluster of the plurality of clusters comprises a plurality of active elements, wherein a weight is applied to each of the plurality of active elements of each cluster.

15 . The apparatus of claim 10 , wherein to select the set or group of clusters the at least one processor is further configured to:

receive a feedback indication from a UE indicating an optimal configuration for each cluster of the plurality of clusters, or

determine the set or group of clusters based on measurements of the plurality of reference signals of the beam training procedure.

16 . The apparatus of claim 10 , wherein if two or more clusters of the plurality of clusters are simultaneously activated, the at least one processor is further configured to:

receive, from the RIS controller, a second plurality of reference signals corresponding to each of the two or more clusters of the plurality of clusters, wherein the second plurality of reference signals further refine a corresponding weighted index of each of the two or more clusters of the plurality of clusters.

17 . The apparatus of claim 10 , wherein a number of clusters within the plurality of clusters of the RIS is adjusted based on a link between the base station and the RIS, an application type, a bandwidth part, component carriers, frequency band and range, or a combination thereof.

18 . The apparatus of claim 10 , wherein the set or group of clusters of the plurality of clusters is activated for a period of time, wherein the cluster configuration indicates an amount of reference signals to perform the beam training procedure based at least on a number of active elements within each cluster.

19 . An apparatus for wireless communication at a reconfigurable intelligent surface (RIS), comprising:

a memory; and

at least one processor coupled to the memory and configured to:

transmit, via a RIS controller, a cluster configuration of the RIS comprising a plurality of clusters,

wherein the cluster configuration further comprises activation of a random selection of one or more clusters based on a first probability p1,

wherein activation of one or more active elements within a respective one of the random selection of the one or more clusters is based on a second probability p2;

receive, from a base station or a user equipment (UE), a sequence of a plurality of reference signals as part of a beam training procedure at each cluster of the plurality of clusters;

receive, from the base station or the UE, an indication indicating a selected set or group of clusters of the plurality of clusters; and

reflect a signal from the base station or the UE using the selected set or group of clusters of the plurality of clusters.

20 . The apparatus of claim 19 , further comprising a transceiver coupled to the at least one processor.

21 . The apparatus of claim 19 , wherein each cluster of the plurality of clusters is activated individually to receive the sequence of the plurality of reference signals.

22 . The apparatus of claim 19 , wherein the at least one processor is further configured to:

receive a second sequence of reference signals to train the selected set or group of clusters.

23 . The apparatus of claim 19 , wherein the selected set or group of clusters is based on at least one of signal strength, signal to noise ratio (SNR), signal to interference plus noise ratio (SINR), modulation and coding scheme (MCS), channel quality indicator (CQI), reference signal received power (RSRP), reference signal received quality (RSRQ), or a combination thereof.

24 . The apparatus of claim 19 , wherein each cluster of the plurality of clusters comprises a plurality of active elements, the at least one processor further configured to:

apply a weight to each of the plurality of active elements of each cluster.

25 . The apparatus of claim 19 , wherein if two or more clusters of the plurality of clusters are simultaneously activated, the at least one processor is further configured to:

transmit, via the RIS controller, a second plurality of reference signals corresponding to each of the two or more clusters of the plurality of clusters, wherein the second plurality of reference signals further refine a corresponding weighted index of each of the two or more clusters of the plurality of clusters.

26 . The apparatus of claim 19 , wherein a number of clusters within the plurality of clusters of the RIS is adjusted based on a link type, an application type, a bandwidth part, component carriers, frequency band and range, or a combination thereof.

27 . The apparatus of claim 19 , wherein a cluster of the plurality of clusters is activated based on a probability Pk and a binary vector, wherein the selected set or group of clusters of the plurality of clusters is activated for a period of time, wherein the cluster configuration indicates an amount of reference signals to perform the beam training procedure based at least on a number of active elements within each cluster.