Communications devices and methods
A communications device is provided. The communications device (which is a receiving communications device) comprises a transceiver configured to receive signals from and/or to transmit signals to one or more of a plurality of other communications devices within sidelink communications resources of a plurality of resource pool instances of a sidelink interface, each of the resource pool instances being arranged in time in accordance with a resource pool periodicity, the resource pool being formed of a plurality of time-divided slots and a plurality of frequency-divided regions, and a controller. The controller is configured in combination with the transceiver to exchange control signaling with a first transmitting communications device of the plurality of other communications devices. Here, the control signaling comprises an indication of a current power saving status of the receiving communications device.
1. A receiving communications device comprising:
a transceiver configured to receive signals from and/or to transmit signals to one or more of a plurality of other communications devices within sidelink communications resources of a plurality of resource pool instances of a sidelink interface, each of the resource pool instances being arranged in time in accordance with a resource pool periodicity, each of the resource pool instances being formed of a plurality of time-divided slots and a plurality of frequency-divided regions, and
a controller configured in combination with the transceiver
to exchange control signalling with a first transmitting communications device of the plurality of other communications devices,
wherein the control signalling comprises an indication of a current power saving status of the receiving communications device,
the power saving status comprises a restricted resource pool monitoring operation of the receiving communications device, wherein, when operating in accordance with the restricted resource pool monitoring operation, the receiving communications device is configured to monitor for one or more current signals transmitted by the first transmitting communications device to the receiving communications device in a subset of the time-divided slots and the frequency-divided regions of a resource pool instance during at least a first of the resource pool instances, and
the subset is dependent on in which of the time-divided slots and the frequency-divided regions of the resource pool instance one or more previous signals were received by the receiving communications device from the first transmitting communications device during a second of the resource pool instances, wherein the second resource pool instance is a preceding resource pool instance to the first resource pool instance.
2. The receiving communications device according to claim 1 , wherein the control signalling includes the indication of power saving status such that it is detectable by at least a second transmitting communications device of the plurality of other communications devices without a communications session between the second transmitting communications device and the receiving communications device, the second transmitting communications device having signals to transmit to the receiving communications device.
3. The receiving communications device according to claim 1 , wherein the control signalling is received by the receiving communications device from the first transmitting communications device.
4. The receiving communications device according to claim 3 , wherein the control signalling is received via one of a Physical Sidelink Control Channel (PSCCH) and a Physical Sidelink Shared Channel (PSSCH).
5. The receiving communications device according to claim 3 , wherein the power saving status had been previously indicated, as part of the control signalling, to the first transmitting communications device by the receiving communications device.
6. The receiving communications device according to claim 1 , wherein the control signalling is transmitted by the receiving communications device to the first transmitting communications device.
7. The receiving communications device according to claim 6 , wherein the control signalling is transmitted via a Physical Sidelink Feedback Channel (PSFCH).
8. The receiving communications device according to claim 1 , wherein the power saving status comprises a discontinuous reception (DRX) operation of the receiving communications device.
9. The receiving communications device according to claim 8 , wherein the receiving communications device is configured to receive the control signalling from the first transmitting communications device, wherein the control signalling comprises an indication of the DRX operation, the indication indicating to the receiving communications device to operate in accordance with the DRX operation.
10. The receiving communications device according to claim 8 , wherein the DRX operation comprises one or more of:
a primary DRX operation in which the receiving communications device is configured, in accordance with a first periodic rate, to switch between an active monitoring state in which the receiving communications device monitors for signals received by the one or more of the other communications devices and a reduced power state in which the receiving communications device does not monitor for signals received by the one or more of the other communications devices,
a secondary DRX operation in which the receiving communications device is configured, in accordance with a second periodic rate which is higher than the first periodic rate, to switch between the active monitoring state and the reduced power state, and
an inactivity timer operation in which the receiving communications device is configured, for the duration of an inactivity period defined by an inactivity timer started upon reception of a signal by the receiving communications device, to stay in the active operating state.
11. The receiving communications device according to claim 1 , wherein the time-divided slots and the frequency-divided regions of the subset are the same as the time-divided slots and the frequency-divided regions of the resource pool instance in which the one or more previous signals were received during the second resource pool instance.
12. The receiving communications device according to claim 1 , wherein if the receiving communications device does not receive any of the one or more current signals in the subset during the first resource pool instance, the receiving communications device is configured
to monitor a larger number of the time-divided slots of the resource pool instance than in the subset and/or a larger number of the frequency-divided regions of the resource pool instance than in the subset for one or more next signals during at least a third of the resource pool instances, wherein the third resource pool instance is a subsequent resource pool instance to the at least the first resource pool instance.
13. The receiving communications device according to claim 1 , wherein the subset comprises all of the plurality of time-divided slots of the resource pool instance and only the frequency-divided regions of the resource pool instance in which the one or more previous signals were received during the second resource pool instance.
14. The receiving communications device according to claim 1 , wherein the subset comprises all of the plurality of frequency-divided regions of the resource pool instance and only the time-divided slots of the resource pool instance in which the one or more previous signals were received during the second resource pool instance.
15. The receiving communications device according to claim 1 , wherein the receiving communications device is configured
to determine that it is to monitor for the one or more current signals in the subset during at least the first resource pool instance based on a predetermined condition being met, and
to transmit an indication to the first transmitting communications device that the receiving communications device is going to monitor for the one or more current signals in the subset during at least the first resource pool instance.
16. The receiving communications device according to claim 1 , wherein the receiving communications device is configured
to transmit, in response to receiving each of the one or more current signals, a feedback signal to the transmitting communications device indicating that the each of the one or more current signals has been successfully received.
17. A method of operating a receiving communications device, the method comprising:
receiving signals from and/or transmitting signals to one or more of a plurality of other communications devices within sidelink communications resources of a plurality of resource pool instances of a sidelink interface, each of the resource pool instances being arranged in time in accordance with a resource pool periodicity, each of the resource pool instances being formed of a plurality of time-divided slots and a plurality of frequency-divided regions, and
exchanging control signalling with a first transmitting communications device of the plurality of other communications devices,
wherein the control signalling comprises an indication of a current power saving status of the receiving communications device,
the power saving status comprises a restricted resource pool monitoring operation of the receiving communications device, wherein, when operating in accordance with the restricted resource pool monitoring operation, the receiving communications device is configured to monitor for one or more current signals transmitted by the first transmitting communications device to the receiving communications device in a subset of the time-divided slots and the frequency-divided regions of a resource pool instance during at least a first of the resource pool instances, and
the subset is dependent on in which of the time-divided slots and the frequency-divided regions of the resource pool instance one or more previous signals were received by the receiving communications device from the first transmitting communications device during a second of the resource pool instances, wherein the second resource pool instance is a preceding resource pool instance to the first resource pool instance.