System and method for time-power frequency hopping for D2D discovery
Embodiments are provided to implement a time/power/frequency hopping scheme for device-to-device (D2D) discovery. The embodiments improve the UE detection of D2D discovery signals from neighboring UEs and account for large number of UEs' discovery signals. This is achieved by having neighboring UEs transmitting at different time instances and at different power levels. Further, neighboring UEs can be configured to transmit on different frequencies. This is achieved by assigning different time/power/frequency sequences to different UEs. An embodiment method includes transmitting, to a UE, parameters a hopping pattern of a first sequence of resources for transmitting a discovery signal by the UE and of a second sequence of resources for receiving a second discovery signal by the UE. The first sequence of resources comprises at least one of a sequence of time instances and a sequence of power levels. The second sequence of resources comprises time instances.
1. A method for assigning resources for a device-to-device (D2D) discovery signal, the method comprising:
receiving, by a user equipment (UE), first parameters from a base station indicating a set of discovery resources in a discovery cycle, wherein the discovery cycle comprises a plurality of subframes;
receiving, by the UE, second parameters from the base station indicating a first probability for transmitting a first discovery signal to a second UE on a subframe of the plurality of subframes;
generating, by the UE, a random number for the subframe; and
transmitting, by the UE, the first discovery signal to the second UE in the discovery cycle in accordance to a comparison of the random number and the first probability.
2. The method according to claim 1 , wherein the first probability is 0.25, 0.5 or 1.
3. The method according to claim 1 , wherein receiving the second parameters comprises receiving a second probability for transmitting a second discovery signal in a further discovery cycle, wherein the first probability is different from the second probability.
4. The method according to claim 1 , further comprising receiving, by the UE, a length of the discovery cycle.
5. The method according to claim 1 , wherein transmitting the first discovery signal in the discovery cycle comprises transmitting the first discovery signal at least once in the discovery cycle according to the comparison.
6. The method according to claim 1 , further comprising, when the UE is unable to send the first discovery signal according to the comparison for the subframe, receiving a further discovery signal sent by another UE during the subframe.
7. The method according to claim 1 , wherein the subframe comprises a set of resource blocks, and wherein, when the UE transmits the discovery signal on a selected resource block from the set of resource blocks, the UE is unable to receive a further discovery signal from another UE on other resource blocks from the set of resource blocks.
8. The method according to claim 1 , wherein the second parameters are assigned to the UE via Radio Resource Control (RRC) signaling.
9. A user device comprising:
at least one processor; and
a non-transitory computer readable storage medium storing programming for execution by the at least one processor, the programming including instructions to:
receive first parameters from a base station indicating a set of discovery resources in a discovery cycle, wherein the discovery cycle comprises a plurality of subframes;
receive second parameters from the base station indicating a first probability for transmitting a first discovery signal to a second user device on a subframe of the plurality of subframes;
generating a random number for the subframe; and
transmitting the first discovery signal to the second user device in the discovery cycle in accordance to a comparison of the random number and the first probability.
10. The user device according to claim 9 , wherein the first probability is 0.25, 0.5 or 1.
11. The user device according to claim 9 , wherein receiving the second parameters comprises receiving a second probability for transmitting a second discovery signal in a further discovery cycle, wherein the first probability is different from the second probability.
12. The user device according to claim 9 , further comprising receiving from the base station a length of the discovery cycle.
13. The user device according to claim 9 , wherein transmitting the first discovery signal in the discovery cycle comprises transmitting the first discovery signal at least once in the discovery cycle according to the comparison.
14. The user device according to claim 9 , further comprising, when the user device is unable to send the first discovery signal according to the comparison for the subframe, receiving a further discovery signal sent by another user device during the subframe.
15. The user device according to claim 9 , wherein the subframe comprises a set of resource blocks, and wherein, when the user device transmits the first discovery signal on a selected resource block from the set of resource blocks, the user device is unable to receive a further discovery signal from another user device on other resource blocks from the set of resource blocks.
16. The user device according to claim 9 , wherein the second parameters are assigned to the user device via Radio Resource Control (RRC) signaling.