Method and wireless device for monitoring downlink control channel
Provided are a method and a wireless device for monitoring a downlink control channel in a wireless communication system. The wireless device monitors a first downlink control channel in a first search space, and monitors a second downlink control channel in a second search space. The first downlink control channel is modulated by a first reference signal, which is generated on the basis of an identifier of a first serving cell, and the second downlink control channel is modulated by a second reference signal, which is generated on the basis of an identifier of a second serving cell.
1. A method of monitoring an enhanced physical downlink control channel (EPDCCH) in a wireless communication system, the method comprising:
receiving, by a wireless device from a base station, a radio resource control (RRC) signal, the RRC signal including first information indicating at least one subframe on which at least one EPDCCH is monitored and second information on a first search space and a second search space;
monitoring, by the wireless device, a first EPDCCH in the first search space on the at least one subframe indicated by the first information; and
monitoring, by the wireless device, a second EPDCCH in the second search space on the at least one subframe indicated by the first information,
wherein the first EPDCCH is set to a local mode and is demodulated by a first demodulation reference signal (DMRS), and
wherein the second EPDCCH is set to a distributed mode and is demodulated by a second DMRS.
2. The method of claim 1 , wherein:
the subframe includes a plurality of physical resource block (PRB) pairs,
the first EPDCCH is allocated in at least one first PRB pair of the at least one subframe indicated by the first information, and
the second EPDCCH is allocated in at least one second PRB pair of the at least one subframe indicated by the first information.
3. The method of claim 2 , wherein each of the plurality of PRB pairs includes a plurality of enhanced control channel elements (ECCEs).
4. The method of claim 1 , wherein the first and second DMRS are generated by:
r
(
m
)
=
1
2
(
1
-
2
·
c
(
m
)
)
+
j
1
2
(
1
-
2
·
c
(
2
m
+
1
)
)
,
wherein a pseudo-random sequence c(m) is initialized as:
c
init
=
(
floor
(
ns
2
)
+
1
)
(
2
N
EPDCCH
,
ID
+
1
)
2
16
+
n
EPDCCH
,
SCID
,
where:
ns denotes a slot number in a radio frame,
N EPDCCH,ID denotes an identifier related to a EPDCCH, and
n EPDCCH,SCID denotes a parameter given from the higher layer.
5. The method of claim 1 , wherein the first and second EPDCCHs are decoded based on an identifier of the wireless device in the first and second search spaces.
6. The method of claim 1 ,
wherein the first DMRS is received within the first search space, and
wherein the second DMRS is received within the second search space.
7. A wireless device for monitoring an enhanced physical downlink control channel (EPDCCH) in a wireless communication system, the wireless device comprising:
a radio frequency (RF) unit configured to transmit and receive a radio signal; and
a processor operatively coupled to the RF unit and configured to:
receive, from a base station, a radio resource control (RRC) signal, the RRC signal including first information indicating at least one subframe on which at least one EPDCCH is monitored and second information on a first search space and a second search space;
monitor a first EPDCCH in the first search space on the at least one subframe indicated by the first information; and
monitor a second EPDCCH in the second search space on the at least one subframe indicated by the first information,
wherein the first EPDCCH is set to a local mode and is demodulated by a first demodulation reference signal (DMRS), and
wherein the second EPDCCH is set to a distributed mode and is demodulated by a second DMRS.
8. The wireless device of claim 7 , wherein:
the subframe includes a plurality of physical resource block (PRB) pairs,
the first EPDCCH is allocated in at least one first PRB pair of the at least one subframe indicated by the first information, and
the second EPDCCH is allocated in at least one second PRB pair of the at least one subframe indicated by the first information.
9. The wireless device of claim 8 , wherein each of the plurality of PRB pairs includes a plurality of enhanced control channel elements (ECCEs).
10. The wireless device of claim 7 , wherein the first and second DMRSs are generated by:
r
(
m
)
=
1
2
(
1
-
2
·
c
(
m
)
)
+
j
1
2
(
1
-
2
·
c
(
2
m
+
1
)
)
,
wherein a pseudo-random sequence c(m) is initialized as:
c
init
=
(
floor
(
ns
2
)
+
1
)
(
2
N
EPDCCH
,
ID
+
1
)
2
16
+
n
EPDCCH
,
SCID
,
where:
ns denotes a slot number in a radio frame,
N EPDCCH,ID denotes an identifier related to a EPDCCH, and
n EPDCCH,SCID denotes a parameter given from the higher layer.
11. The wireless device of claim 7 ,
wherein the first DMRS is received within the first search space, and
wherein the second DMRS is received within the second search space.