Method and apparatus for transmitting and receiving signal using device-to-device communication and superposition coding in wireless communication system
Disclosed herein is a method of transmitting a signal at a relay user equipment (UE) in a wireless communication system. The method includes receiving uplink data for relay from a first UE, performing superposition coding with respect to the uplink data and sidelink data to be transmitted to a second UE through a sidelink to generate an uplink relay signal, and transmitting the uplink relay signal to a base station and the second UE.
1. A method of transmitting a signal by a relay user equipment (UE) in a wireless communication system, the method comprising:
broadcasting a searching message to search for a first UE having uplink data for relaying among a plurality of primary UEs;
receiving, from the first UE, a request message to relay the uplink data of the first UE;
transmitting, to the first UE, a response message to accept the uplink data in response to the request message;
receiving, from the first UE, the uplink data;
generating an uplink relay signal by performing superposition coding between the uplink data and sidelink data to be transmitted to a second UE; and
transmitting the uplink relay signal to a base station and the second UE,
wherein data rate of the uplink relay signal is determined by <Equation A>:
R
D
=
log
(
1
+
h
i
(
1
-
x
i
2
)
p
i
N
)
,
〈
Equation
A
〉
where R D is a data rate of the uplink relay signal, h i is a link gain between the relay UE and the second UE, x i is a power ratio between the uplink data and the sidelink data, p i is a transmission power of the relay UE and N is additive noise of the second UE.
2. The method according to claim 1 , further comprising:
receiving, from the base station, downlink data for relaying;
generating an uplink relay signal by performing superposition coding between the downlink data and the sidelink data; and
transmitting the downlink relay signal to the first UE and the second UE.
3. The method according to claim 2 , wherein the uplink relay signal and the downlink relay signal are transmitted in resources for transmitting the sidelink data.
4. A relay user equipment (UE) in a wireless communication system, the relay UE comprising:
a transceiver; and
a processor connected to the transceiver,
wherein the processor is configured to:
broadcast a searching message to search for a first UE having uplink data for relaying among a plurality of primary UEs,
control the transceiver to receive, from the first UE, a request message to relay the uplink data of the first UE,
control the transceiver to transmit, to the first UE, a response message to accept the uplink data in response to the request message,
control the transceiver to receive, from the first UE, the uplink,
generate an uplink relay signal by performing superposition coding between the uplink data and sidelink data to be transmitted to a second UE, and
control the transceiver to transmit the uplink relay signal to a base station and the second UE, and
wherein data rate of the uplink relay signal is determined by <Equation A>:
R
D
=
log
(
1
+
h
i
(
1
-
x
i
2
)
p
i
N
)
,
〈
Equation
A
〉
where R D is a data rate of the uplink relay signal, h i is a link gain between the relay UE and the second UE, x i is a power ratio between the uplink data and the sidelink data, p i is a transmission power of the relay UE and N is additive noise of the second UE.
5. The relay UE according to claim 4 , wherein the processor is configured to:
receive, from the base station, downlink data for relaying,
generate a downlink relay signal by performing superposition coding between the downlink data and the sidelink data, and
transmit the downlink relay signal to the first UE and the second UE.
6. The relay UE according to claim 5 , wherein the uplink relay signal and the downlink relay signal are transmitted in resources for transmitting the sidelink data.