Method and apparatus for timing alignment based on scheduling request
An operation method of a terminal in a communication system may comprise: in response to occurrence of uplink (UL) data, transmitting a scheduling request (SR) for the UL data to a base station; performing a UL timing alignment procedure with the base station when a UL timing between the terminal and the base station is not synchronized; receiving a UL grant for the UL data from the base station; and transmitting the UL data to the base station using resources indicated by the UL grant.
1 . An operation method of a terminal in a communication system, the operation method comprising:
in response to occurrence of uplink (UL) data, transmitting a scheduling request (SR) for the UL data to a base station;
performing a UL timing alignment procedure with the base station when a UL timing between the terminal and the base station is not synchronized;
receiving a UL grant for the UL data from the base station; and
transmitting the UL data to the base station using resources indicated by the UL grant,
wherein a timing advance command (TAC) medium access control (MAC) control element (CE) including information for uplink timing synchronization is received in the UL timing alignment procedure, a SR-prohibit timer is started when the SR is transmitted, the SR-prohibit timer is terminated when the TAC MAC CE is received, and a transmission operation or a retransmission operation of the SR is not performed during a time corresponding to the SR-prohibit timer.
2 . The operation method according to claim 1 , wherein the performing of the UL timing alignment procedure comprises:
receiving downlink (DL) allocation information from the base station;
receiving the TAC MAC CE from the base station using resources indicated by the DL allocation information;
aligning the UL timing synchronization between the terminal and the base station based on a TAC included in the TAC MAC CE; and
transmitting a hybrid automatic repeat request (HARQ)-acknowledgement (ACK) for the TAC MAC CE to the base station.
3 . The operation method according to claim 2 , wherein the DL allocation information is included in downlink control information (DCI), and the DCI is scrambled by a radio temporary network identifier (RNTI) indicating transmission of the TAC MAC CE.
4 . The operation method according to claim 2 , wherein the SR is transmitted on a narrowband physical random access channel (NPRACH), and each of the DL allocation information and the UL grant is received on a narrowband physical downlink control channel (NPDCCH).
5 . The operation method according to claim 1 , further comprising performing a synchronization procedure with the base station before transmitting the SR to the base station, wherein the UL timing alignment procedure is performed before transmission of the UL data when a UL timing determined by the synchronization procedure needs to be adjusted.
6 . An operation method of a base station in a communication system, the operation method comprising:
configuring a scheduling request (SR)-prohibit timer;
transmitting SR configuration information including the SR-prohibit timer to a terminal;
receiving an SR for uplink (UL) data from the terminal;
performing a UL timing alignment procedure with the terminal when a UL timing between the terminal and the base station is not synchronized;
transmitting a UL grant for the UL data to the terminal; and
receiving the UL data from the terminal through resources indicated by the UL grant,
wherein the SR-prohibit timer is started when the terminal transmits the SR, and a transmission operation or a retransmission operation of the SR is not performed during a time corresponding to the SR-prohibit timer.
7 . The operation method according to claim 6 , wherein the performing of the UL timing alignment procedure comprises:
transmitting downlink (DL) allocation information to the terminal;
transmitting a timing advance command (TAC) medium access control (MAC) control element (CE) to the terminal using resources indicated by the DL allocation information; and
receiving a hybrid automatic repeat request (HARQ)-acknowledgement (ACK) for the TAC MAC CE from the terminal.
8 . The operation method according to claim 7 , wherein the SR is received on a narrowband physical random access channel (NPRACH), and each of the DL allocation information and the UL grant is transmitted on a narrowband physical downlink control channel (NPDCCH).
9 . The operation method according to claim 6 , further comprising performing a synchronization procedure with the terminal before receiving the SR, wherein the UL timing alignment procedure is performed before reception of the UL data when a UL timing determined by the synchronization procedure needs to be adjusted.
10 . An operation method of a terminal in a communication system, the operation method comprising:
in response to occurrence of uplink (UL) data, transmitting a scheduling request (SR) for the UL data to a base station;
receiving downlink (DL) allocation information from the base station;
receiving a medium access control (MAC) protocol data unit (PDU) from the base station using resources indicated by the DL allocation information, the MAC PDU including a timing advance command (TAC) for UL timing alignment between the terminal and the base station and a UL grant for the UL data;
aligning UL timing synchronization between the terminal and the base station based on the TAC; and
transmitting the UL data to the base station using resources indicated by the UL grant,
wherein a SR-prohibit timer is started when the SR is transmitted, the SR-prohibit timer is terminated when the TAC is received, and a transmission operation or a retransmission operation of the SR is not performed during a time corresponding to the SR-prohibit timer.
11 . The operation method according to claim 10 , further comprising performing a synchronization procedure with the base station before transmitting the SR to the base station, wherein the MAC PDU is received when a UL timing determined by the synchronization procedure needs to be adjusted.
12 . The operation method according to claim 10 , wherein the MAC PDU includes a MAC header and a MAC payload, the MAC payload is a scheduling request response (SRR) MAC control element (CE) including the TAC and the UL grant, and a logical channel identifier (LCID) included in the MAC header indicates that the MAC PDU includes the SRR MAC CE.
13 . The operation method according to claim 12 , wherein the DL allocation information is included in downlink control information (DCI), and the DCI is scrambled by a radio temporary network identifier (RNTI) indicating transmission of the SRR MAC CE.
14 . The operation method according to claim 10 , wherein a hybrid automatic repeat request (HARQ)-acknowledgment (ACK) for the MAC PDU is configured not to be transmitted.