D2D connection recovery schemes
View Patent ↗Schemes for recovering D2D connections between terminals (UEs) in an LTE network are described. The schemes may be applied in situations where a D2D connection is established between two UEs but is lost by, for example, one of the UEs entering a sleep state. The schemes may be applied to either centralized or distributed D2D systems. Some of the schemes are eNB-assisted while others are performed solely by the UEs.
1. A user equipment (UE) device, comprising:
a radio transceiver to provide an air interface for communicating with an eNB (evolved node B) and for D2D (device-to-device) communications; and
processing circuitry connected to the radio transceiver to:
establish a D2D communications session with a second UE,
if a message from the second UE indicates that the second UE is to be entering a sleep state and a wakeup time is received, transmit an acknowledgement message to the second UE and, at the indicated wakeup time, transmit a D2D recovery message to the second UE and wait for a response thereto to re-establish the D2D communications session;
if the D2D communications session with the second UE is lost but no message indicating the wakeup time is received from the second UE, transmit a D2D recovery request to the eNB;
if a response to the D2D recovery request is received from the eNB indicating the next paging time and if the second UE responds to a page at the paging time, transmit a D2D recovery message to the second UE at the paging time and wait for a response thereto to re-establish the D2D communications session.
2. The device of claim 1 wherein the processing circuitry is further to:
after re-establishment of the D2D communications session with the second UE, transmit a message to the eNB indicating that the D2D communications session has been re-stablished.
3. The device of claim 1 wherein the processing circuitry is further to:
if the D2D communications session with the second UE is lost but no message indicating the wakeup time is received from the second UE, transmit a D2D recovery request to the eNB;
if a response to the D2D recovery request is received from the eNB indicating a wakeup time previously transmitted to the eNB by the second UE, transmit a D2D recovery message to the second UE at the wakeup time and wait for a response thereto to re-establish the D2D communications session.
4. The device of claim 1 wherein the processing circuitry is further to:
if requested to do so by the eNB, measure the signal transmitted by the second UE when responding to the page over the physical random access channel (PRACH), and transmit a measurement report back to the eNB; and,
if authorized to do on by the eNB in response to the transmitted measurement report, transmit a D2D recovery message to the second UE at the paging time and wait for a response thereto to re-establish the D2D communications session.
5. The device of claim 1 wherein the processing circuitry is further to:
if requested to do so by the eNB, measure the signal transmitted by the second UE over an uplink control channel after responding to the page, and transmit a measurement report back to the eNB; and,
if authorized to do so by the eNB in response to the transmitted measurement report, transmit a D2D recovery message to the second UE at the paging time and wait for a response thereto to re-establish the D2D communications session.
6. A user equipment (UE) device, comprising:
a radio transceiver to provide an air interface for communicating with an eNB (evolved node B) and for D2D (device-to-device) communications; and
processing circuitry connected to the radio transceiver to:
establish a D2D communications session with a second UE;
if a message from the second UE indicates that the second UE is to be entering a sleep state and a wakeup time is received, transmit an acknowledgement message to the second UE and, at the indicated wakeup time, transmit a D2D recovery message to the second UE and wait for a response thereto to re-establish the D2D communications session;
if the D2D communications session with the second UE is lost but no message indicating the wakeup time is received from the second UE, transmit a D2D recovery request to the eNB;
if a response to the D2D recovery request is received from the eNB indicating a wakeup time previously transmitted to the eNB b the second UE, transmit a D2D recovery message to the second UE at the wakeup time and wait for a response thereto to re-establish the D2D communications session.
7. The device of claim 6 wherein the processing circuitry is further to, if a sleep state is to be entered after establishment of the D2D communications session, transmit a message to the eNB indicating a wakeup time.
8. The device of claim 6 wherein the processing circuitry is further to, after re-establishment of the D2D communications session with the second UE, transmit a message to the eNB indicating that the D2D communications session has been re-established.
9. A method for operating a user equipment (UE), comprising:
establishing a device-to device (D2D) communications session with a second UE;
if a message from the second UE indicating that the second UE is to be entering a sleep state is received, negotiating a wakeup time for the second UE to wake from the sleep state; and
transmitting a D2D recovery message to the second UE at the wakeup time and waiting for a response thereto to re-establish the D2D communications session;
if the D2D communications session with the second UE is lost but no message indicating the wakeup time is received from the second UE, transmitting a D2D recovers request to the eNB;
if a response to the D2D recovery request is received from the eNB indicating a wakeup time previously transmitted to the eNB by the second UE, transmitting a D2D recovery message to the second UE at the wakeup time and waiting for a response thereto to re-establish the D2D communications session.
10. The method of claim 9 further comprising: if a sleep state is to be entered after establishment of the D2D communications session, transmitting a message to the eNB indicating a wakeup time.
11. The method of claim 9 further comprising: after re-establishment of the D2D communications session with the second UE, transmitting a message to the eNB indicating that the D2D communications session has been re-established.
12. The method of claim 9 further comprising: measuring the signal transmitted by the second UE in responding to a page over the physical random access channel (PRACH) in response to a request from the eNB.
13. The method of claim 9 further comprising: measuring the signal transmitted by the second UE after responding to the page over an uplink control channel in response to a request from the eNB.
14. The method of claim 12 further comprising: receiving a D2D recovery authorization from the eNB if the measurement of the signal transmitted by the second UE is adequate.
15. A method for operating a user equipment (UE), comprising:
establishing a device-to device (D2D) communications session with a second UE;
if a message from the second UE indicating that the second UE is to be entering a sleep state is received, negotiating a wakeup time for the second UE to wake from the sleep state; and
transmitting a D2D recovery message to the second UE at the wakeup time and waiting for a response thereto to re-establish the D2D communications session;
if the D2D communications session with the second UE is lost but no message indicating the wakeup time is received from the second UE, transmitting a D2D recovery request to an eNB;
if a response to the D2D recovery request is received from the eNB indicating the next paging time and if the second UE responds to a page at the paging time, transmitting a D2D recovery message to the second UE at the paging time and waiting for a response thereto to re-establish the D2D communications session.
16. The method of claim 15 further comprising:
after re-establishment of the D2D communications session with the second UE, transmitting a message to the eNB indicating that the D2D communications session has been re-established.
17. The method of claim 15 further comprising:
if the D2D communications session with the second UE is lost but no message indicating the wakeup time is received from the second UE, transmitting a D2D recovery request to an eNB;
if a response to the D2D recovery request is received from the eNB indicating a wakeup time previously transmitted to the eNB by the second UE, transmitting a D2D recovery message to the second UE at the wakeup time and waiting for a response thereto to re-establish the D2D communications session.
18. The method of claim 16 further comprising:
if requested to do so by the eNB, measuring the signal transmitted by the second UE when responding to the page over the physical random access channel (PRACH), and transmitting a measurement report back to the eNB; and,
if authorized to do so by the eNB in response to the transmitted measurement report, transmitting a D2D recovery message to the second UE at the paging time and waiting for a response thereto to re-establish the D2D communications session.
19. The method of claim 16 further comprising:
if requested to do so by the eNB, measuring the signal transmitted by the second UE over an uplink control channel after responding to the page, and transmitting a measurement report back to the eNB; and,
if authorized to do so by the eNB in response to the transmitted measurement report, transmitting a D2D recovery message to the second UE at the paging time and waiting for a response thereto to re-establish the D2D communications session.
20. The method of claim 15 further comprising:
if a sleep state is to be entered after establishment of the D2D communications session with the second UE, transmitting a message to the second UE indicating a wakeup time;
if an acknowledgement message is received from the second UE in response to transmission of the wakeup time thereto and if a D2D recovery request is received from the second UE at the wakeup time, responding to the D2D recovery request to re-establish the D2D communications session.