Method for performing a change of mode in devices directly communicating with each other in a wireless connection system, and apparatus for same
The present invention relates to a method for determining whether a mode change condition for performing a hand-over to a cellular network through which devices communicate with each other is satisfied, transmitting a mode change instruction message to a base station when the mode change condition is satisfied, receiving a mode change command message for starting a mode change from the base station, transmitting a first data packet index with respect to a data packet transmitted to a second device at a final stage through the communication between the devices to the base station, ending the communication with the second device when the inter-device communication end request message is received from the base station, and transmitting data to the second device through the cellular network.
1. A method of performing a mode change, which is performed by a first device performing a device-to-device communication in a wireless access system, the method comprising:
determining whether a mode change condition for performing a handover to a cellular network is satisfied while performing the device-to-device communication;
transmitting a mode change indication message to a base station when the mode change condition is satisfied;
receiving a mode change command message from the base station to initiate the mode change;
transmitting a first data packet index for a data packet, which is lastly transmitted to a second device via the device-to-device communication, to the base station;
when a device-to-device communication termination request message is received from the base station, terminating the device-to-device communication with the second device; and
transmitting data to the second device via the cellular network,
wherein the device-to-device communication termination request message includes a third data packet index for a data packet firstly transmitted via the cellular network by comparing the first data packet index and a second data packet index, and
wherein the second data packet index indicates a data packet which is lastly received by the second device via the device-to-device communication.
2. The method of claim 1 , wherein the third data packet index corresponds to a smaller value among the first data packet index and the second data packet index.
3. The method of claim 1 , wherein the mode change indication message comprises quality information of a link between the first device and the second device.
4. A method of performing a mode change, which is performed by a first device performing a device-to-device communication in a wireless access system, comprising the steps of:
determining whether a mode change condition for performing a handover to a cellular network is satisfied while performing the device-to-device communication;
transmitting a RACH request message to a base station when the mode change condition is satisfied;
transmitting a mode change indication message to the base station via a resource obtained by transmitting the RACH request message;
receiving a mode change command message from the base station to initiate the mode change;
transmitting a first data packet index for a data packet, which is lastly transmitted to a second device via the device-to-device communication, to the base station,
when a device-to-device communication termination request message is received from the base station, terminating the device-to-device communication with the second device; and
transmitting data to the second device via the cellular network,
wherein the device-to-device communication termination request message includes a third data packet index for a data packet firstly transmitted via the cellular network by comparing the first data packet index and a second data packet index, and
wherein the second data packet index indicates a data packet which is lastly received by the second device via the device-to-device communication.
5. The method of claim 4 , wherein the third data packet index corresponds to a smaller value among the first data packet index and the second data packet index.
6. The method of claim 4 , wherein the mode change indication message comprises quality information of a link between the first device and the second device.
7. A device for performing a mode change while performing a device-to-device communication in a wireless access system, comprising:
a radio frequency (RF) unit configured to comprise a transmitter and a receiver; and
a processor configured to support the mode change,
the processor configured to:
determine whether a mode change condition for performing a handover to a cellular network is satisfied while performing the device-to-device communication,
transmit a mode change indication message to a base station via the RF unit when the mode change condition is satisfied,
receive a mode change command message from the base station via the RF unit to initiate the mode change,
transmit a first data packet index for a data packet, which is lastly transmitted by a second device via the device-to-device communication, to the base station via the RF unit, when a device-to-device communication termination request message is received from the base station,
terminate the device-to-device communication with the second device, and
transmit data to the second device via the cellular network using the RF module,
wherein the device-to-device communication termination request message includes a third data packet index for a data packet firstly transmitted via the cellular network by comparing the first data packet index and a second data packet index, and
wherein the second data packet index indicates a data packet which is lastly received by the second device via the device-to-device communication.
8. The device of claim 7 , wherein the mode change indication message comprises quality information of a link between the first device and the second device.
9. The device of claim 7 , wherein when the mode change condition is satisfied, the processor is configured to transmit a RACH request message to the base station via the RF unit and wherein the processor is configured to transmit the mode change indication message to the base station via a resource obtained by transmitting the RACH request message using the RF unit.