Systems, methods, and devices for link quality based relay selection

1. A method of wireless communication of a remote user equipment (UE) composing:

determining a first link quality, the first link quality indicating a link quality of a first link between a first potential relay UE and the remote UE;

determining a second link quality, the second link quality indicating a link quality of a second link between the first potential relay UE and a first base station;

ranking the first potential relay UE relative to a second potential relay UE, the ranking of the first potential relay UE based on a combination of the first link quality and the second link quality, wherein the combination of the first link quality and the second link quality reduces total resource usage; and

selecting one of the first potential relay UE and the second potential relay UE for a relay connection based on the ranking of the first potential relay UE relative to the second potential relay UE.

2. The method of claim 1 , further comprising:

receiving a first PC5 message from the first potential relay UE, the first link quality being determined based on the received first PC5 message; and

receiving a second PC5 message from the first potential relay UE, the second PC5 message comprising information indicating the second link quality.

3. The method of claim 2 , wherein the first PC5 message and the second PC5 message are the same PC5 message.

4. The method of claim 2 , wherein the first link quality of the first link is determined by determining at least one of a reference signal received power (RSRP), a reference signal received quality (RSRQ), a signal-to-noise ratio (SNR), or signal-to-interference-plus noise ratio (SINR) of the first PC5 message.

5. The method of claim 2 , wherein the second link quality is a function of at least one of a reference signal received power (RSRP), a reference signal received quality (RSRQ), a signal-to-noise ratio (SNR), or a signal-to-interference-plus-noise ratio (SINR) of the second link.

6. The method of claim 1 , further comprising:

determining a third link quality, the third link quality indicating a link quality of a third link between the second potential relay UE and the remote UE; and

determining a fourth link quality, the fourth link quality indicating a link quality of a fourth link between the second potential relay UE and a second base station,

wherein the first potential relay UE is ranked relative to the second potential relay UE further based on a combination of the third link quality and the fourth link quality.

7. The method of claim 6 , further comprising:

receiving a third PC5 message from the second potential relay UE, the third link quality being determined based on the received third PC5 message; and

receiving a fourth PC5 message from the second potential relay UE, the fourth PC5 message comprising information indicating the fourth link quality.

8. The method of claim 6 , wherein the first base station and the second base station comprise a single base station.

9. The method of claim 1 , wherein one of the first potential relay UE and the second potential relay UE is selected based on a highest ranking of the first potential relay UE and the second potential relay UE.

10. The method of claim 1 , wherein the ranking comprises combining the first link quality and the second link quality by applying a first weighting factor to the first link quality and applying a second weighting factor to the second link quality.

11. The method of claim 10 , wherein the first weighting factor and the second weighting factor are fixed values.

12. The method of claim 10 , wherein the first weighting factor and the second weighting factor are preconfigured in the remote UE.

13. The method of claim 10 , further comprising receiving information indicating at least one of the first weighting factor or the second weighting factor from a serving base station.

14. The method of claim 13 , wherein the information indicating the at least one of the first weighting factor or the second weighting factor is received in a system information block (SIB) from the serving base station.

15. The method of claim 13 , wherein the information indicating the at least one of the first weighting factor or the second weighting factor is received as a dedicated radio resource control (RRC) signaling from the serving base station.

16. The method of claim 10 , further comprising receiving information indicating at least one of the first weighting factor or the second weighting factor from one of the first potential relay UE or the second potential relay UE as a part of a PC5 message.

17. The method of claim 10 , wherein the ranking further comprises selecting a minimum of the first link quality and the second link quality.

18. The method of claim 10 , wherein the ranking is based on a linear average of the first link quality and the second link quality.

19. The method of claim 1 , further comprising transmitting a measurement report to the first base station, the measurement report including at least one of the first link quality and the second link quality.

20. The method of claim 19 , further comprising receiving information from the first based station indicating at least one of the first potential relay UE or the second potential relay UE, the received information being based on the transmitted measurement report.

21. The method of claim 20 , further comprising:

connecting to one of the first potential relay UE or the second potential relay UE based on the received information; and

informing the first base station when at least one of the remote UE is successful at connecting to the one of the first potential relay UE or the second potential relay UE, or the remote UE has failed to connect to the relay UE.

22. The method of claim 20 , further comprising transitioning from a radio resource control (RRC) connected state to an RRC idle state with respect to a serving base station upon successfully connecting to one of the first potential relay UE or the second potential relay UE.

23. The method of claim 1 , wherein the first link quality and the second link quality do not include measures of signal power.

24. An apparatus for wireless communication, the apparatus being a remote user equipment (UE), comprising:

a memory; and

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

determine a first link quality, the first link quality indicating a link quality of a first link between a first potential relay UE and the remote UE;

determine a second link quality, the second link quality indicating a link quality of a second link between the first potential relay UE and a first base station;

rank the first potential relay UE relative to a second potential relay UE, the ranking of the first potential relay UE based on a combination of the first link quality and the second link quality, wherein the combination of the first link quality and the second link quality reduces total resource usage; and

select one of the first potential relay UE and the second potential relay UE for a relay connection based on the ranking of the first potential relay UE relative to the second potential relay UE.

25. The apparatus of claim 24 , wherein the at least one processor is further configured to:

receive a first PC5 message from the first potential relay UE, The first link quality being determined based on the received first PC5 message; and

receive a second PC5 message from the first potential relay UE, the second PC5 message comprising information indicating the second link quality.

26. The apparatus of claim 25 , wherein the first PC5 message and the second PC5 message are the same PC5 message.

27. The apparatus of claim 25 , wherein the first link quality of the first link is determined by determining at least one of a reference signal received power (RSRP), a reference signal received quality (RSRQ), a signal-to-noise ratio (SNR), or signal-to-interference-plus noise ratio (SNR) of the first PC5 message.

28. The apparatus of claim 25 , wherein the second link quality is a function of at least one of a reference signal received power (RSRP), a reference signal received quality (RSRQ), a signal-to-noise ratio (SNR), or a signal-to-interference-plus-noise ratio (SNR) of the second link.

29. The apparatus of claim 24 , wherein the at least one processor is further configured to:

determine a third link quality, the third link quality indicating a link quality of a third link between the second potential relay UE and the remote UE; and

determine a fourth link quality, the fourth link quality indicating a link quality of a fourth link between the second potential relay UE and a second base station,

wherein the first potential relay UE is ranked relative to the second potential relay UE further based on a combination of the third link quality and the fourth link quality.

30. The apparatus of claim 29 , wherein the at least one processor is further configured to:

receive a third PC5 message from the second potential relay UE, the third link quality being determined based on the received third PC5 message; and

receive a fourth PC5 message from the second potential relay UE, the fourth PC5 message comprising information indicating the fourth link quality.

31. The apparatus of claim 29 , wherein the first base station and the second base station comprise a single base station.

32. The apparatus of claim 24 , wherein one of the first potential relay UE and the second potential relay UE is selected based on a highest ranking of the first potential relay UE and the second potential relay UE.

33. The apparatus of claim 24 , wherein the at least one processor is further configured to rank by combining the first link quality and the second link quality by applying a first weighting factor to the first link quality and applying a second weighting factor to the second link quality.

34. The apparatus of claim 33 , wherein the first weighting factor and the second weighting factor are fixed values.

35. The apparatus of claim 33 , wherein the first weighting factor and the second weighting factor are preconfigured in the remote UE.

36. The apparatus of claim 33 , wherein the at least one processor is further configured to receive information indicating at least one of the first weighting factor or the second weighting factor from a serving base station.

37. The apparatus of claim 36 , wherein the information indicating the at least one of the first weighting factor or the second weighting factor is received in a system information block (SIB) from the serving base station.

38. The apparatus of claim 36 , wherein the information indicating the at least one of the first weighting factor or the second weighting factor is received as a dedicated radio resource control (RRC) signaling from the serving base station.

39. The apparatus of claim 33 , wherein the at least one processor is further configured to receive information indicating at least one of the first weighting factor or the second weighting factor from one of the first potential relay UE or the second potential relay UE as a part of a PC5 message.

40. An apparatus for wireless communication, the apparatus being a remote user equipment (UE), comprising:

means for determining a first link quality, the first link quality indicating a link quality of a first link between a first potential relay UE and the remote LTE;

means for determining a second link quality, the second link quality indicating a link quality of a second link between the first potential relay UE and a first base station;

means for ranking the first potential relay UE relative to a second potential relay UE, the ranking of the first potential relay UE based on a combination of the first link quality and the second link quality, wherein the combination of the first link quality and the second link quality reduces total resource usage; and

means for selecting one of the first potential relay UE and the second potential relay UE for a relay connection based on the ranking of the first potential relay UE relative to the second potential relay UE.

41. A non-transistory computer-readable medium storing computer-executable code for wireless communication in a remote user equipment (UE), comprising code to:

determine a first link quality, the first link quality indicating a link quality of a first link between a first potential relay UE and the remote UE;

determine a second link quality, the second link quality indicating a link quality of a second link between the first potential relay UE and a first base station;

rank the first potential relay UE relative to a second potential relay UE, the ranking of the first potential relay UE based on a combination of the first link quality and the second link quality, wherein the combination of the first link quality and the second link quality reduces total resource usage; and

select one of the first potential relay UE and the second potential relay UE for a relay connection based on the ranking of the first potential relay UE relative to the second potential relay UE.