Method for random access, user equipment and base station
The present disclosure relates to a communication method and system for converging a 5 th -Generation (5G) communication system for supporting higher data rates beyond a 4 th -Generation (4G) system with a technology for Internet of Things (IoT). The present disclosure may be applied to intelligent services based on the 5G communication technology and the IoT-related technology, such as smart home, smart building, smart city, smart car, connected car, health care, digital education, smart retail, security and safety services. Embodiments of the present invention provide a method for RACH re-attempt, a user equipment and a base station. The method comprises the steps of: by a base station, determining system configuration information and transmitting the system configuration information to a user equipment; and then, by the user equipment, transmitting a preamble sequence to perform random access, and if the random access is failed, performing RACH attempt according to the received RACH re-attempt configuration information to perform random access until a preset decision condition is satisfied. The embodiment of the present invention is used for RACH re-attempt when random access fails.
1. A method performed by a terminal in a wireless communication system, the method comprising:
setting a preamble transmission counter to 1;
setting a preamble power ramping counter to 1;
transmitting, to a base station, a random access preamble by using a first transmission power identified based on the preamble power ramping counter;
increasing the preamble transmission counter by 1, in case that a random access window expires and a random access response corresponding to the random access preamble is not received;
in case that a transmission beam for a retransmission of the random access preamble is not switched, increasing the preamble power ramping counter by 1 for the retransmission, based on the increased preamble transmission counter;
identifying a second transmission power based on the increased preamble power ramping counter; and
transmitting, to the base station, the random access preamble by using the second transmission power,
wherein the first transmission power and the second transmission power are identified based on an equation given by:
transmission power={initial received target power+delta preamble+(the preamble power ramping counter −1) * preamble power ramping step},
wherein the delta preamble is a preamble format based power offset value and the preamble power ramping step is a power ramping factor.
2. The method of claim 1 , wherein, in case that at least one of the transmission beam for the retransmission or a physical random access channel (PRACH) resource for the retransmission is changed, the preamble power ramping counter is not increased for the retransmission.
3. The method of claim 1 , wherein the preamble power ramping counter is increased by 1, in case that the transmission beam for the retransmission is not switched and a PRACH resource for the retransmission is not changed.
4. A method performed by a base station in a wireless communication system, the method comprising:
receiving, from a terminal, a transmission of a random access preamble by using a first transmission power; and
receiving, from the terminal, a retransmission of the random access preamble by using a second transmission power,
wherein a preamble transmission counter is increased by 1, in case that a random access window expires and a random access response reception fails,
wherein a preamble power ramping counter is increased by 1 for the retransmission, in case that a transmission beam for the retransmission is not switched, and
wherein the first transmission power and the second transmission power are identified based on an equation given by:
transmission power={initial received target power+delta preamble+(the preamble power ramping counter −1) * preamble power ramping step},
wherein the delta preamble is a preamble format based power offset value and the preamble power ramping step is a power ramping factor.
5. The method of claim 4 , wherein, in case that at least one of the transmission beam for the retransmission or a physical random access channel (PRACH) resource for the retransmission is changed, the preamble power ramping counter is not increased for the retransmission.
6. The method of claim 4 , wherein the preamble power ramping counter is increased by 1, in case that the transmission beam for the retransmission is not switched and a PRACH resource for the retransmission is not changed.
7. A terminal in a wireless communication system, the terminal comprising:
a transceiver configured to transmit and receive a signal; and
a controller configured to:
set a preamble transmission counter to 1,
set a preamble power ramping counter to 1,
transmit, to a base station, a random access preamble by using a first transmission power identified based on the preamble power ramping counter,
increase the preamble transmission counter by 1, in case that a random access window expires and a random access response corresponding to the random access preamble is not received,
in case that a transmission beam for a retransmission of the random access preamble is not switched, increase the preamble power ramping counter by 1 for the retransmission, based on the increased preamble transmission counter,
identify a second transmission power based on the increased preamble power ramping counter, and
transmit, to the base station, the random access preamble by using the second transmission power,
wherein the first transmission power and the second transmission power are identified based on an equation given by:
transmission power={initial received target power+delta preamble+(the preamble power ramping counter −1) * preamble power ramping step},
wherein the delta preamble is a preamble format based power offset value and the preamble power ramping step is a power ramping factor.
8. The terminal of claim 7 , wherein, in case that at least one of the transmission beam for the retransmission or a physical random access channel (PRACH) resource for the retransmission is changed, the preamble power ramping counter is not increased for the retransmission.
9. The terminal of claim 7 , wherein the preamble power ramping counter is increased by 1, in case that the transmission beam for the retransmission is not switched and a PRACH resource for the retransmission is not changed.
10. A base station in a wireless communication system, the base station comprising:
a transceiver configured to transmit and receive a signal; and
a controller configured to:
receive, from a terminal, a transmission of a random access preamble by using a first transmission power, and
receive, from the terminal, a retransmission of the random access preamble by using a second transmission power,
wherein a preamble transmission counter is increased by 1, in case that a random access window expires and a random access response reception fails,
wherein a preamble power ramping counter is increased by 1 for the retransmission, in case that a transmission beam for the retransmission is not switched, and
wherein the first transmission power and the second transmission power are identified based on an equation given by:
transmission power={initial received target power+delta preamble+(the preamble power ramping counter −1) * preamble power ramping step},
wherein the delta preamble is a preamble format based power offset value and the preamble power ramping step is a power ramping factor.
11. The base station of claim 10 , wherein, in case that at least one of the transmission beam for the retransmission or a physical random access channel (PRACH) resource for the retransmission is changed, the preamble power ramping counter is not increased for the retransmission.
12. The base station of claim 10 , wherein the preamble power ramping counter is increased by 1, in case that the transmission beam for the retransmission is not switched and a PRACH resource for the retransmission is not changed.