Power saving for pedestrian user equipment in vehicular communications systems
Embodiments are presented herein for adjusting the conduct of routine communications of safety messages in V2X networks in order to conserve resources in participating power-limited devices while satisfying V2X system latency demands. Scheduling (e.g., timing and/or frequency) of safety message communications performed by certain UE devices participating in a V2X network may be dynamically adjusted according to various criteria, such as factors relating to the DRX cycle schedule, motion or mobility, traffic environment, and/or battery or power capabilities of the UE devices, which may conserve UE resources and power consumption. Certain UE devices may efficiently transmit safety messages to the V2X network using one of several proposed RACH-based procedures. In some embodiments, the size of safety message communications may be reduced through various compression techniques, and/or by reducing the amount of contained information, e.g., by omitting certain parameters, which may reduce the resources consumed by performing safety message communications.
1. A cellular base station, comprising:
at least one antenna for performing wireless communications;
a radio coupled to the at least one antenna; and
a processing element coupled to the radio;
wherein the cellular base station has an associated cellular coverage area;
wherein the base station is configured to:
provide uplink scheduling information to a plurality of UEs in the cellular coverage area specifying scheduling of transmission resources for safety messages in a time window proximate to UE wake-up times;
wherein the uplink scheduling information is transmitted to the plurality of UEs in a group downlink control channel utilizing a downlink control information (DCI) field reserved for vehicular communication safety application notifications, and
wherein, for each UE, the safety message comprises position information of the UE for use in avoiding collisions with vehicles.
2. The base station of claim 1 ,
wherein the uplink scheduling information specifying scheduling of transmission resources for safety messages in a time window proximate to a UE wake-up time operates to reduce power usage of the plurality of UEs by avoiding extra wake-ups for transmission of the safety messages.
3. The base station of claim 1 ,
wherein the uplink scheduling information specifies use of Physical Uplink Shared Channel (PUSCH) resources for periodic transmission of the safety messages.
4. The base station of claim 1 , wherein the uplink scheduling information is transmitted using downlink control information (DCI) and specifies aperiodic transmission of the safety messages.
5. The base station of claim 1 , wherein the UE wake-up times are Connected Mode Discontinuous Reception (CDRX) wake-up times.
6. The base station of claim 1 , wherein the base station is further configured to:
determine a first UE of the plurality of UEs that is in a low mobility state;
provide, in response to determining that the first UE is in the low mobility state, second uplink scheduling information to the first UE which reduces frequency of uplink transmission of the safety messages in order to save power of the first UE.
7. The base station of claim 6 , wherein the base station is further configured to:
determine that position information has not been received from the first UE in a current period;
provide prior position information of the first UE for use by other UEs in response to the determination that position information had not been received from the first UE in the current period.
8. The base station of claim 6 , wherein the base station is further configured to:
determine that the first UE has transitioned to a high mobility state;
provide, in response to determining that the first UE has transitioned to the high mobility state, third uplink scheduling information to the first UE which increases the frequency of uplink transmission of the safety messages.
9. The base station of claim 1 , wherein the base station is further configured to:
wherein, for at least one of the plurality of UEs, the uplink scheduling information specifies a frequency of uplink transmission of safety messages that is based on a mobility state of the at least one UE.
10. A user equipment (UE), comprising:
at least one antenna for performing wireless communications;
a radio coupled to the at least one antenna; and
a processing element coupled to the radio;
wherein the UE is configured to:
receive and store uplink scheduling information from a cellular base station, wherein the uplink scheduling information specifies scheduling of transmission resources for safety messages in a time window proximate to wake-up times of the UE, and
wherein the uplink scheduling information is received in a group downlink control channel utilizing a downlink control information (DCI) field reserved for vehicular communication safety application notifications;
transmit safety messages proximate to wake-up times of the UE based on the received uplink scheduling information, wherein the safety messages comprise position information of the UE for use in avoiding collisions with vehicles.
11. The UE of claim 10 , wherein the wake-up times of the UE are Connected Mode Discontinuous Reception (CDRX) wake-up times.
12. The UE of claim 10 , wherein the UE is configured to transmit the safety messages at a frequency that is based on a mobility state of the UE.
13. A cellular base station, comprising:
at least one antenna for performing wireless communications;
a radio coupled to the at least one antenna; and
a processing element coupled to the radio;
wherein the cellular base station has an associated cellular coverage area;
wherein the base station is configured to:
provide uplink scheduling information to a plurality of UEs in the cellular coverage area specifying scheduling of transmission resources for safety messages;
wherein the uplink scheduling information is transmitted to the plurality of UEs in a group downlink control channel utilizing a downlink control information (DCI) field reserved for vehicular communication safety application notifications, and
wherein, for at least one of the plurality of UEs, the uplink scheduling information specifies a frequency of uplink transmission of safety messages that is based on a mobility state of the at least one UE.
14. The base station of claim 13 , wherein the base station is further configured to:
determine a first UE of the plurality of UEs that is in a low mobility state;
provide, in response to determining that the first UE is in the low mobility state, second uplink scheduling information to the first UE which reduces frequency of uplink transmission of the safety messages in order to save power of the first UE.
15. The base station of claim 14 , wherein the base station is further configured to:
determine that position information has not been received from the first UE in a current period;
provide prior position information of the first UE for use by other UEs in response to the determination that position information had not been received from the first UE in the current period.
16. The base station of claim 14 , wherein the base station is further configured to:
determine that the first UE has transitioned to a high mobility state;
provide, in response to determining that the first UE has transitioned to the high mobility state, third uplink scheduling information to the first UE which increases the frequency of uplink transmission of the safety messages.
17. The base station of claim 13 , wherein the base station is further configured to:
determine a first UE of the plurality of UEs that is in a high mobility state;
provide, in response to determining that the first UE is in the high mobility state, second uplink scheduling information to the first UE which increases frequency of uplink transmission of the safety messages.
18. The base station of claim 13 ,
wherein for the at least one UE, the safety messages each comprises position, timestamp, and speed information of the UE for use in avoiding collisions with vehicles.
19. The base station of claim 13 ,
wherein the base station is further configured to:
receive mobility state information from the at least one UE indicating the mobility state of the at least one UE.
20. The base station of claim 13 , wherein the UE wake-up times are Connected Mode Discontinuous Reception (CDRX) wake-up times.