RANDOM ACCESS METHOD AND APPARATUS AND COMMUNICATION SYSTEM
A terminal apparatus includes: a transmitter configured to transmit a first message (MsgA) of a random access procedure according to two-step contention-free random access resource configuration, the first message (MsgA) including a two-step contention-free random access preamble and a physical uplink shared channel; and processor circuitry configured to determine, when the terminal apparatus receives a media access control layer protocol data unit (MAC PDU) including a timing advance command media access layer control element (TAC MAC CE) after transmitting the first message, and the MAC PDU is successfully demodulated, that consider the random access successfully completed.
1 . A terminal apparatus comprising:
a transmitter configured to transmit a first message (MsgA) of a random access procedure according to two-step contention-free random access resource configuration, the first message (MsgA) including a two-step contention-free random access preamble and a physical uplink shared channel; and
processor circuitry configured to determine, when the terminal apparatus receives a media access control layer protocol data unit (MAC PDU) including a timing advance command media access layer control element (TAC MAC CE) after transmitting the first message, and the MAC PDU is successfully demodulated, that consider the random access successfully completed.
2 . The terminal apparatus according to claim 1 , further comprising
a receiver is further configured to receive the two-step contention-free random access resource configuration via a physical downlink control channel (PDCCH) or radio resource control (RRC) signaling.
3 . The terminal apparatus according to claim 2 , wherein
the receiver is further configured to receive the two-step contention-free random access resource configuration via a physical downlink control channel (PDCCH) or radio resource control (RRC) signaling.
4 . The terminal apparatus according to claim 1 , wherein
the MAC PDU is scheduled by a physical downlink control channel addressed to a cell radio network temporary identifier (C-RNTI).
5 . The terminal apparatus according to claim 1 , wherein
the two-step contention-free random access resources includes dedicated two-step random access resources, the dedicated two-step random access resources including at least one synchronization signal block (SSB) or channel state information reference signal (CSI-RS) and a dedicated two-step random access preamble to which the synchronization signal block (SSB) or the channel state information reference signal (CSI-RS) corresponds.
6 . The terminal apparatus according to claim 1 , wherein
the processor circuitry is further configured to:
start a response window for a second message (MsgB) of the random access procedure, and
control to monitor a physical downlink control channel (PDCCH) addressed to a cell radio network temporary identifier (C-RNTI) and a PDCCH addressed to a second message radio network temporary identifier (MsgB-RNTI) while the response window for MsgB is running.
7 . A network device comprising:
a receiver configured to receive, from a terminal apparatus, a first message (MsgA) of a random access procedure according to two-step contention-free random access resource configuration, the first message (MsgA) including a two-step contention-free random access preamble and a physical uplink shared channel; and
a transmitter configured to transmit, to the terminal apparatus, a media access control layer protocol data unit (MAC PDU) including a timing advance command media access layer control element (TAC MAC CE) after receiving the first message, the MAC PDU is used for considering the random access successfully completed.
8 . The network device according to claim 7 , wherein
the transmitter is further configured to transmit the two-step contention-free random access resource configuration via a physical downlink control channel (PDCCH) or radio resource control (RRC) signaling.
9 . The network device according to claim 7 , wherein
the transmitter is further configured to transmit a physical downlink control channel addressed to a cell radio network temporary identifier (C-RNTI), the physical downlink control channel scheduling the MAC PDU.
10 . A terminal equipment comprising:
processor circuitry configured to:
measure downlink reference signal received power,
determine a random access type according to configuration information of a bandwidth part (BWP) and the downlink reference signal received power,
select a random access resource,
when the random access type is two-step random access and a selection condition of the two-step contention-free random access resources is satisfied, select two-step contention-free random access resource as the random access resource, and
when the random access type is two-step random access and a selection condition of the two-step contention-free random access resources is not satisfied, select two-step contention-based random access resource as the random access resource; and
a transmitter configured to transmit an initial message of random access on the random access resources.
11 . The terminal apparatus according to claim 10 , the to determine a random access type according to configuration information of a bandwidth part selected by the terminal equipment and downlink reference signal received power measured by the terminal equipment further comprising:
the processor circuitry is further configured to determine, when the bandwidth part selected by the terminal equipment is configured with two-step random access resource and the downlink reference signal received power is higher than a first threshold, that the random access type is two-step random access.