Joint communication and sensing aided random access channel
Systems, devices and methods for a backscatter measurement based multiple RACH preamble transmissions are disclosed. A WTRU may receive a JCS-RS configuration comprising a minimum RACH preamble retransmission interval. The JCS-RS configuration may comprise a JCS backscatter power fraction (λ) of the WTRU transmit power (P Tx ). The WTRU may transmit a RACH preamble in a RACH occasion corresponding to a preferred SS/PBCH Index using an initial WTRU transmit beam, having an associated first RA-RNTI value. The backscatter power (P BS ) may be measured using the WTRU receive beam corresponding to the WTRU transmit beam used for the RACH preamble transmission. On a condition that P BS >λP Tx , the WTRU may retransmit the RACH preamble after a retransmission interval, on resources associated with a second RA-RNTI value. The WTRU may be configured for monitoring the PDCCH common search space with the first RA-RNTI and the second RA-RNTI, for respective RAR window intervals.
1. A wireless transmit/receive unit (WTRU) comprising:
a receiver configured to receive configuration information, wherein the configuration information includes a backscatter power fraction of a WTRU transmit power and a minimum random access channel (RACH) preamble retransmission interval;
a transmitter configured to transmit a RACH preamble in a RACH occasion using an initial transmit beam;
circuitry configured to measure backscatter power using a receive beam corresponding to the initial transmit beam;
the transmitter configured to, on a condition that the measured backscatter power is greater than the backscatter power fraction of the WTRU transmit power, and no random access response (RAR) is received within the minimum RACH preamble retransmission interval, retransmit the RACH preamble using an alternate beam selected based on the backscatter power measurement; and
the receiver configured to monitor a physical downlink control channel (PDCCH) common search space during a first RAR window interval and during a second RAR window interval, wherein the second RAR window interval is determined based on a backscatter power threshold-based adaptive retransmission rule.
2. The WTRU of claim 1 , wherein the minimum RACH preamble retransmission interval is less than the first RAR window interval.
3. The WTRU of claim 2 , wherein the first RAR window interval and the second RAR window interval overlap.
4. The WTRU of claim 1 , wherein the transmitter is configured to retransmit the RACH preamble using a power ramp-up by N steps, where N is greater than one.
5. The WTRU of claim 1 , wherein the WTRU is configured with multiple backscatter power thresholds, each backscatter threshold having an associated minimum RACH preamble retransmission interval.
6. The WTRU of claim 1 , wherein the WTRU is configured with a RAR window reduction factor and the first RAR window interval for a RACH preamble transmission is reduced by the RAR window reduction factor when the measured backscatter power is greater than the backscatter power fraction of the WTRU transmit power.
7. The WTRU of claim 1 , wherein the condition of the measured backscatter power being greater than the backscatter power fraction of the WTRU transmit power indicates that a direction is blocked.
8. The WTRU of claim 1 , wherein the transmitter is further configure to, on a condition that the receiver receives a RAR within the first RAR window or the second RAR window, transmit a message using the configuration included in the RAR.
9. The WTRU of claim 1 , wherein the configuration information includes a joint communications and sensing (JCS) reference signal configuration.
10. The WTRU of claim 1 , wherein the RACH preamble corresponds to a synchronization signal block (SSB) index.
11. The WTRU of claim 1 , wherein the initial transmit beam is associated with a first random access radio network temporary identifier (RA-RNTI).
12. The WTRU of claim 11 , wherein the RACH preamble is retransmitted on resources associated with a second RA-RNTI.
13. The WTRU of claim 12 , wherein the receiver is configured to monitor the PDCCH common search space using the first RA-RNTI during the first RAR window interval and using the second RA-RNTI during the second RAR window interval.
14. A method performed by a wireless transmit/receive unit (WTRU) comprising:
receiving configuration information, wherein the configuration information includes a backscatter power fraction of a WTRU transmit power and a minimum random access channel (RACH) preamble retransmission interval;
transmitting a RACH preamble in a RACH occasion using an initial transmit beam;
measuring backscatter power using a receive beam corresponding to the initial transmit beam;
retransmitting using an alternate beam selected based on the backscatter power measurement, on a condition that the measured backscatter power is greater than the backscatter power fraction of the WTRU transmit power, and no random access response (RAR) is received within the minimum RACH preamble retransmission interval, the RACH preamble; and
monitoring a physical downlink control channel (PDCCH) common search space during a first RAR window interval and during a second RAR window interval, wherein the second RAR window interval is determined based on a backscatter power threshold-based retransmission rule.
15. The method of claim 14 , wherein the configuration information includes a joint communications and sensing (JCS) reference signal configuration.
16. The method of claim 14 , wherein the RACH preamble corresponds to a synchronization signal block (SSB) index.
17. The method of claim 14 , wherein the initial transmit beam is associated with a first random access radio network temporary identifier (RA-RNTI).
18. The method of claim 17 , wherein the RACH preamble is retransmitted on resources associated with a second RA-RNTI.
19. The method of claim 18 , wherein the receiver is configured to monitor the PDCCH common search space using the first RA-RNTI during the first RAR window interval and using the second RA-RNTI during the second RAR window interval.