Method and apparatus for performing contention-based uplink transmission in a wireless communication system
The present invention provides a method and apparatus for performing contention-based uplink transmission in a wireless communication system. A terminal transmits a contention-based uplink signal to a base station. The base station detects a contention-based uplink signal that is transmitted from at least one terminal, and determines whether there exists a terminal corresponding to the detected contention-based uplink signal. The terminal receives an uplink (UL) grant from the base station. The terminal switches from a dormant station into an active state, based on the uplink grant. Here, the dormant state is a state where radio resource control connection is formed between the base station and the terminal but data is not actually transmitted, and the active state is a state where data transmission is actually performed.
1. A state transition method performed by a user equipment (UE) in a wireless communication system, the method comprising:
transmitting, to a base station, a contention-based uplink (UL) signal including at least one of a buffer status signal and UL data in a state where a scheduling request (SR) is not transmitted;
receiving a UL grant from the base station if the contention-based UL signal is successfully detected by the base station;
receiving an acknowledgment (ACK)/non-acknowledgement (NACK) from the base station in response to the contention-based UL signal, the ACK/NACK being received through a physical hybrid ARQ indicator channel (PHICH), the ACK/NACK being received by being included in the UL grant, a resource of the PHICH for the transmission of the ACK/NACK being allocated by using a cell specific radio resource control (RRC) signaling, a UE specific RRC signaling, or a dynamic PDCCH signaling, the resource of the PHICH being determined based on a lowest physical resource block (PRB) index in a resource allocation of a physical uplink shared channel (PUSCH) and a cyclic shift value of a reference signal (RS) that is transmitted using the UL grant, the resource of the PHICH being expressed by an index pair that is determined by:
n
PHICH
group
=
(
I
PRB_RA
lowest_index
+
n
DMRS
)
mod
N
PHICH
group
+
I
PHICH
N
PHICH
group
n
PHICH
seq
=
(
⌊
I
PRB_RA
lowest_index
/
N
PHICH
group
⌋
+
n
DMRS
)
mod
2
N
SF
PHICH
,
where n DMRS is determined based on a cyclic shift for DMRS field in a DCI format; and
transitioning from a dormant state to an active state on the basis of the UL grant,
wherein the dormant state is a state in which a radio resource control (RRC) connection is established between the base station and the user equipment, but data is not actually transmitted, and
wherein the active state is a state in which the RRC connection is established between the base station and the user equipment, and data can be transmitted or received between the base station and the user equipment.
2. The method of claim 1 , wherein the contention-based UL signal is transmitted through a physical uplink control channel (PUCCH).
3. The method of claim 2 , wherein the contention-based UL signal is transmitted through the PUCCH on a basis of a PUCCH format 2.
4. The method of claim 1 , wherein the contention-based UL signal is transmitted through the PUSCH.
5. The method of claim 1 , further comprising transmitting the RS to detect the contention-based UL signal of the base station.
6. The method of claim 1 , wherein the contention-based UL signal is transmitted through a resource reserved in a time domain or a frequency domain.
7. A user equipment (UE), comprising:
a radio frequency (RF) unit configured for transmitting or receiving a radio signal; and
a processor coupled to the RF unit, the processor being configured for:
transmitting, to a base station, a contention-based uplink (UL) signal including at least one of a buffer status signal and UL data in a state where a scheduling request (SR) is not transmitted;
receiving a UL grant from the base station if the contention-based UL signal is successfully detected by the base station;
receiving an acknowledgment (ACK)/non-acknowledgement (NACK) from the base station in response to the contention-based UL signal, the ACK/NACK being received through a physical hybrid ARQ indicator channel (PHICH), the ACK/NACK being received by being included in the UL grant, a resource of the PHICH for the transmission of the ACK/NACK being allocated by using a cell specific radio resource control (RRC) signaling, a UE specific RRC signaling, or a dynamic PDCCH signaling, the resource of the PHICH being determined based on a lowest physical resource block (PRB) index in a resource allocation of a physical uplink shared channel (PUSCH) and a cyclic shift value of a reference signal (RS) that is transmitted using the UL grant, the resource of the PHICH being expressed by an index pair that is determined by:
n
PHICH
group
=
(
I
PRB_RA
lowest_index
+
n
DMRS
)
mod
N
PHICH
group
+
I
PHICH
N
PHICH
group
n
PHICH
seq
=
(
⌊
I
PRB_RA
lowest_index
/
N
PHICH
group
⌋
+
n
DMRS
)
mod
2
N
SF
PHICH
,
where n DMRS is determined based on a cyclic shift for DMRS field in a DCI format; and
transitioning from a dormant state to an active state on the basis of the UL grant,
wherein the dormant state is a state in which a radio resource control (RRC) connection is established between the base station and the user equipment, but data is not actually transmitted, and
wherein the active state is a state in which the RRC connection is established between the base station and the user equipment, and data can be transmitted or received between the base station and the user equipment.