Switching mode of operation in D2D communications

1. A method of device to device (D2D) wireless communication at a user equipment (UE), comprising:

receiving a connection response message from a base station comprising one or more mode switching parameters, the one or more switching parameters relating to an indication of an imminent radio link failure (RLF) with the base station;

establishing communications with one or more other UEs according to a first D2D mode, the first D2D mode based at least in part on a centralized transmission resource schedule received from the base station;

determining that the one or more mode switching parameters have been satisfied;

switching to a second D2D mode before the RLF occurs, the second D2D mode based at least in part on a distributed transmission scheduling using a first indication of a pool of resources allocated by the base station;

monitoring communications from the base station for a second indication of the pool of resources;

determining that a message from the base station indicating the pool of resources is not available; and

switching to a third D2D mode, the third D2D mode based at least in part on a distributed transmission utilizing a preconfigured resource pool.

2. The method of claim 1 , further comprising:

sending a connection setup request to the base station, the connection setup request comprising a D2D mode indication.

3. The method of claim 2 , further comprising:

receiving one or more mode switching parameters via a broadcasted system information block (SIB) message.

4. The method of claim 1 , wherein the one or more mode switching parameters comprise at least one of an out of sync indication related to a number of bad frames, an in sync indication related to a number of good frames, a time period, a path loss threshold and signal to noise (SINR) ratio threshold.

5. The method of claim 1 , wherein the one or more mode switching parameters comprise at least one of a threshold number of random access channel (RACH) requests, a time period following and unsuccessful RACH attempt, a time period following a status report (SR) a buffer status report (BSR) or a resource request, or an indication of a handover failure or an incomplete handover.

6. The method of claim 1 , wherein the one or more mode switching parameters are received from a system information broadcast.

7. The method of claim 1 , wherein the one or more mode switching parameters comprise a time period and at least one additional mode switching parameter; and

wherein determining that the one or more mode switching parameters have been satisfied comprises determining that the at least one additional mode switching parameter has been satisfied and waiting until the time period has elapsed before switching to a second D2D mode.

8. The method of claim 1 , further comprising:

sending a mode switching request to the base station.

9. The method of claim 8 , wherein the one or more mode switching parameters comprise an indication from a user application and the mode switching request comprises a user initiated mode switch indication.

10. The method of claim 8 , further comprising:

receiving a response from the base station indicating that a mode switch is allowed.

11. The method of claim 8 , wherein the switching to a second D2D mode is performed autonomously prior to receiving a response from the base station.

12. The method of claim 1 , wherein the one or more mode switching parameters comprise a modified RLF threshold.

13. The method of claim 12 , wherein the modified RLF threshold is configured to be satisfied prior to reaching an unmodified RLF threshold.

14. The method of claim 1 , further comprising:

storing a mode switch information log comprising one or more of a time stamp, a UE location, a radio interface condition, a UE velocity, a cell ID, and a carrier frequency.

15. The method of claim 1 , further comprising:

maintaining a media access control (MAC) or a radio link control (RLC) configuration after switching to the second D2D mode.

16. The method of claim 1 , further comprising:

reconfiguring a media access control (MAC) or a radio link control (RLC) configuration according to a predetermined state after switching to the second D2D mode.

17. The method of claim 1 , further comprising:

continuing communications based on distributed transmission scheduling until one or more hysteresis parameters are met.

18. The method of claim 17 , wherein the one or more hysteresis parameters include at least one of a time period, a path loss parameter, a number of good frames, and a signal to noise ratio (SINR).

19. The method of claim 1 , further comprising:

resetting a protocol layer configuration, the resetting based at least in part on the switching.

20. The method of claim 1 , further comprising:

utilizing the pool of resources associated with the second D2D mode until a connection is established with the base station; and

establishing the connection with the base station.

21. The method of claim 20 , further comprising:

switching to the first D2D mode, the first D2D mode based at least in part on the centralized transmission resource schedule received from the base station.

22. An apparatus for device to device (D2D) wireless communication at a user equipment (UE), comprising:

a processor;

memory in electronic communication with the processor; and

instructions stored in the memory, the instructions being executable by the processor to:

receive a connection response message from a base station comprising one or more mode switching parameters, the one or more switching parameters relating to an indication of an imminent radio link failure (RLF) with the base station;

establish communications with one or more other UEs according to a first D2D mode, the first D2D mode based at least in part on a centralized transmission resource schedule received from the base station;

determine that the one or more mode switching parameters have been satisfied, wherein the one or more mode switching parameters comprise an indication from a user application;

sending a mode switching request to the base station, wherein the mode switching request comprises a user initiated mode switch indication; and

switch to a second D2D mode before the RLF occurs, the second D2D mode based at least in part on a distributed transmission scheduling using a pool of resources allocated by the base station.

23. The apparatus of claim 22 , wherein the instructions are further executable by the processor to:

monitor communications from the base station for an indication of the pool of resources;

determine that a message from the base station indicating the pool of resources is not receivable; and

switch to a third D2D mode, the third D2D mode being based on distributed transmission utilizing a preconfigured resource pool.

24. The apparatus of claim 22 , wherein the instructions are further executable by the processor to:

send a connection setup request to the base station, the connection setup request comprising a D2D mode indication.

25. An apparatus for device to device (D2D) wireless communication at a user equipment (UE), comprising:

a processor;

memory in electronic communication with the processor; and

instructions stored in the memory, the instructions being executable by the processor to:

receive a connection response message from a base station comprising one or more mode switching parameters, the one or more switching parameters relating to an indication of an imminent radio link failure (RLF) with the base station;

establish communications with one or more other UEs according to a first D2D mode, the first D2D mode based at least in part on a centralized transmission resource schedule received from the base station;

determine that the one or more mode switching parameters have been satisfied;

switch to a second D2D mode before the RLF occurs, the second D2D mode based at least in part on a distributed transmission scheduling using a first indication of a pool of resources allocated by the base station;

monitor communications from the base station for a second indication of the pool of resources;

determine that a message from the base station indicating the pool of resources is not receivable; and

switch to a third D2D mode, the third D2D mode being based on distributed transmission utilizing a preconfigured resource pool.

26. A method of device to device (D2D) wireless communication, comprising:

establishing communications with one or more other UEs according to a first D2D mode, the first D2D mode based at least in part on a preconfigured pool of transmission resources;

receiving system information from a base station allocating a pool of resources for transmission;

sending a mode switching request to the base station, wherein the mode switching request comprises a user initiated mode switch indication;

switching to a second D2D mode based at least in part on one or more mode switching parameters, the second D2D mode being based on distributed transmission scheduling using the pool of resources allocated by the base station;

modifying the one or more mode switching parameters, wherein the one or more mode switching parameters comprise an indication from a user application; and continuing communications based on the distributed transmission scheduling until the one or more modified switching parameters are met.

27. The method of claim 26 , further comprising:

establishing a connected state with the base station; and

switching to a third D2D mode, the third D2D mode based at least in part on a centralized transmission resource schedule received from the base station subsequent to establishing the connected state.

28. The apparatus of claim 25 , wherein the instructions are further executable to:

send a connection setup request to the base station, the connection setup request comprising a D2D mode indication.

29. The apparatus of claim 25 , wherein the instructions are further executable to:

maintain a media access control (MAC) or a radio link control (RLC) configuration after switching to the second D2D mode.

30. The apparatus of claim 25 , wherein the instructions are further executable to:

continue communications based on distributed transmission scheduling until one or more hysteresis parameters are met.