Realizing Mobile Relays For Device-to-Device (D2D) Communications
Systems, methods, and instrumentalities are disclosed for a WTRU to act as a mobile relay, the method comprising the WTRU connecting to the network, the WTRU receiving a message from the network indicating that the WTRU is to act as a mobile relay for one or more devices outside of the coverage of the network, the WTRU discovering one or more devices outside of the coverage of the network, and the WTRU receiving a message from the out-of-coverage device that indicates that the out-of-coverage device has selected the WTRU to act as a mobile relay.
1 . A wireless transmit/receive unit (WTRU) comprising:
a memory; and
a processor configured to:
receive discovery transmissions from two or more mobile relays, the discovery transmissions comprising a first discovery transmission from a first mobile relay and a second discovery transmission from a second mobile relay;
determine a first reference signal received power (RSRP) based on the first discovery transmission from the first mobile relay and a second RSRP based on the second discovery transmission from the second mobile relay;
determine whether the first and second RSRPs exceed a configured threshold;
determine whether the first mobile relay and whether the second mobile relay support a temporary mobile group identity (TMGI) associated with the WTRU;
select a mobile relay that supports the TMGI associated with the WTRU and that has an RSRP exceeding the configured threshold, wherein the first mobile relay is selected based on the first mobile relay having a highest RSRP among the two or more mobile relays that support the TMGI associated with the WTRU;
send a request to connect with the first mobile relay; and
connect with the first mobile relay selected by the WTRU.
2 . The WTRU of claim 1 , wherein the WTRU periodically measures the first RSRP, and is further configured to:
determine the second RSRP exceeds the configured threshold during a subsequent measurement opportunity on a condition that the WTRU determines, based on the measurements, that the first RSRP is below the configured threshold;
determine the second mobile relay supports the TMGI associated with the WTRU;
send a request to connect with the second mobile relay, the second mobile relay being selected, wherein the second mobile relay has the highest RSRP among the two or more mobile relays that support the TMGI associated with the WTRU during the subsequent measurement opportunity; and
disconnect with the first mobile relay and connect with the second mobile relay selected by the WTRU.
3 . The WTRU of claim 1 , wherein the discovery transmissions comprise identifications for the two or more mobile relays.
4 . The WTRU of claim 3 , wherein the WTRU is further configured to report the received identifications for the two or more mobile relays to an evolved Node-B (eNB).
5 . The WTRU of claim 4 , wherein the identifications for the two or more mobile relays include mobile relay layer 2 identification (ID) or physical layer ID.
6 . The WTRU of claim 1 , wherein the WTRU is further configured to:
determine a connection with an evolved Node-B (eNB) is no longer available; and
send a discovery request to a mobile relay, wherein the discovery request comprises a proximity service (ProSe) code and an identifier of the WTRU.
7 . The WTRU of claim 6 , wherein the ProSe code is hard coded in the WTRU.
8 . The WTRU of claim 6 , wherein the identifier is part of an application code within the discovery request.
9 . The WTRU of claim 1 , wherein the WTRU is further configured to:
receive a notification from the first mobile relay over PC5, wherein the notification is associated with losing a connection with an evolved Node-B (eNB);
send a discovery request for the second mobile relay on PC5;
determine the second RSRP of the second mobile relay on PC5 is above the configured threshold;
determine the second mobile relay supports the TMGI associated with the WTRU;
send a request to connect with the second mobile relay, the second mobile relay being selected by the WTRU, wherein the second mobile relay is selected based on the second mobile relay having a highest RSRP among the two or more mobile relays that support the TMGI associated with the WTRU; and
disconnect with the first mobile relay and establish a one-to-one connection with the second mobile relay selected by the WTRU.
10 . The WTRU of claim 9 , wherein the notification is received via physical layer (PHY) signaling or radio resource control (RRC) layer control signaling.
11 . The WTRU of claim 9 , wherein the request is for a one-to-one connection with the second mobile relay and comprises a Proximity Service (ProSe) Identification (ID) of the WTRU.
12 - 13 . (canceled)
14 . The WTRU of claim 1 , wherein the selection of the first mobile relay is based on one or more types of the service of public land mobile network identification (PLMN ID) announced or mobile relay specific information.
15 . The WTRU of claim 1 , wherein the configured threshold is part of a radio resource control (RRC) configuration.
16 - 30 . (canceled)
31 . A method for device to device (D2D) communication, comprising:
receiving discovery transmissions from two or more mobile relays, the discovery transmissions comprising a first discovery transmission from a first mobile relay and a second discovery transmission from a second mobile relay;
determining a first reference signal received power (RSRP) based on the first discovery transmission from the first mobile relay and a second RSRP based on the second discovery transmission from the second mobile relay;
determining whether the first and second RSRPs exceed a configured threshold;
determining whether the first mobile relay and whether the second mobile relay support a temporary mobile group identity (TMGI) associated with the WTRU;
selecting a mobile relay that supports the TMGI associated with the WTRU and that has an RSRP exceeding the configured threshold, wherein the first mobile relay is selected based on the first mobile relay having a highest RSRP among the two or more mobile relays that support a TMGI associated with the WTRU;
sending a request to connect with the first mobile relay; and
connecting with the first mobile relay.
32 . The method of claim 31 , further comprising:
determining the second RSRP exceeds the configured threshold during a subsequent measurement opportunity on a condition that the first RSRP is below the configured threshold;
determining the second mobile relay supports the TMGI associated with the WTRU;
selecting the second mobile relay having the highest RSRP among the two or more mobile relays that support the TMGI associated with the WTRU during the subsequent measurement opportunity;
sending a request to connect with the second mobile relay; and
disconnecting with the first mobile relay and connecting with the second mobile relay.