Random access method and apparatus and communication system
A random access apparatus, applicable to a terminal equipment, includes first processor circuitry, wherein the first processor circuitry is configured to determine a random access type according to configuration information of a bandwidth part (BWP) for random access selected by the terminal equipment and downlink reference signal received power measured by the terminal equipment, perform selection of random access resources, and transmit an initial message of random access on the random access resources.
1. A random access apparatus, applicable to a terminal equipment, the apparatus comprising first processor circuitry, wherein the first processor circuitry is configured to:
determine a random access type according to configuration information of a bandwidth part (BWP) for random access selected by the terminal equipment and downlink reference signal received power measured by the terminal equipment;
perform selection of random access resources; and
transmit an initial message of random access on the random access resources,
wherein the performing of the selection of the random access resources comprises:
performing two-step random access resource selection after determining that the random access type is two-step random access; and
performing four-step random access resource selection after determining that the random access type is four-step random access,
wherein the performing two-step random access resource selection comprises:
selecting two-step contention-free random access resources when a selection condition of the two-step contention-free random access resources is satisfied; and
selecting two-step contention-based random access resources when the selection condition of the two-step contention-free based random access resources in not satisfied.
2. The apparatus according to claim 1 , wherein the determining 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 comprises:
in a case where the bandwidth part selected by the terminal equipment is configured with two-step random access resources and the downlink reference signal received power measured by the terminal equipment is higher than a first threshold, determining that the random access type is two-step random access, or in a case where the bandwidth part selected by the terminal equipment is only configured with two-step random access resources, determining that the random access type is two-step random access; otherwise, determining that the random access type is four-step random access.
3. The apparatus according to claim 1 , wherein the selection condition of the two-step contention-free based random access resources being satisfied comprises:
that the terminal equipment is configured with dedicated two-step random access resources by a network device, and reference signal received power (RSRP) of at least one synchronization signal block (SSB) or channel state information reference signal (CSI-RS) in the dedicated two-step random access resources is higher than a second threshold;
wherein the dedicated two-step random access resources comprise 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 channel state information reference signal (CSI-RS) corresponds.
4. The apparatus according to claim 1 , wherein the selecting two-step contention-free random access resources comprises:
selecting a synchronization signal block (SSB) or channel state information reference signal (CSI-RS) used for transmitting a dedicated two-step random access preamble and a physical uplink shared channel (PUSCH);
setting a to-be-transmitted two-step random access preamble to be a dedicated two-step random access preamble to which the synchronization signal block (SSB) or the channel state information reference signal (CSI-RS) corresponds;
determining a preamble access occasion for two-step random access to which a next available synchronization signal block (SSB) or channel state information reference signal (CSI-RS) corresponds; and
determining an uplink grant according to a physical uplink shared channel (PUSCH) corresponding to the to-be-transmitted two-step random access preamble and the preamble access occasion.
5. The apparatus according to claim 4 , wherein the setting a to-be-transmitted two-step random access preamble to be a dedicated two-step random access preamble to which the synchronization signal block (SSB) or the channel state information reference signal (CSI-RS) corresponds comprises:
when the synchronization signal block (SSB) or the channel state information reference signal (CSI-RS) is configured with dedicated two-step random access preambles corresponding to group A and group B, selecting a dedicated two-step random access preamble of group A or group B according to a path loss and/or a transport block size (TB size) of a first message (MsgA) of a two-step contention-free random access procedure;
wherein modulation and coding schemes (MCSs) of the physical uplink shared channels (PUSCHs) to which the dedicated two-step random access preambles corresponding to group A and group B correspond are different.
6. The apparatus according to claim 1 , wherein,
when the terminal equipment selects the two-step random access resources, or when the random access type is two-step random access,
selection of random access resources is performed again in the case that a random access procedure is not successfully completed.
7. The apparatus according to claim 6 , wherein,
when the random access procedure is not successfully completed and a count value of transmitting random access preambles is greater than a threshold N,
the random access type is set to four-step random access, and selection of four-step random access resources is performed.
8. The apparatus according to claim 6 , wherein,
the selection of random access resources being performed again comprises:
when it is determined that there exist two-step contention-free random access resources satisfying the selection condition within backoff time, or that there exist contention-free random access resources satisfying the selection condition, selection of random access resources is performed again before the end of the backoff time; otherwise, after the end of the backoff time, selection of random access resources is performed again.
9. A random access apparatus, applicable to a terminal equipment, the apparatus comprising third processor circuitry, wherein the third processor circuitry is configured to:
receive two-step contention-free random access resource configuration transmitted by a network device for a first message (MsgA);
transmit to the network device the first message (MsgA) of a two-step contention-free random access procedure, the first message comprising a two-step contention-free random access preamble and a physical uplink shared channel; and
when receiving a second message (MsgB) transmitted by the network device, determine that the random access response is successfully received and consider this random access successfully completed,
wherein the receiving the second message (MsgB) transmitted by the network device comprises:
a media access control layer protocol data unit (MAC PDU) scheduled by a physical downlink control channel (PDCCH) addressed to the cell radio network temporary identifier (C-RNTI) is successfully demodulated, and the media access control layer protocol data unit contains a timing advance command media access layer control element (TAC MAC CE).
10. The apparatus according to claim 9 , wherein,
the third processor circuitry receives the two-step contention-free random access resource configuration via a physical downlink control channel (PDCCH) or radio resource control (RRC) signaling.
11. The apparatus according to claim 9 , wherein,
the two-step contention-free random access resources comprise dedicated two-step random access resources, and
the dedicated two-step random access resources comprising 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.
12. The apparatus according to claim 9 , wherein the third processor circuitry is further configured to:
start a response window for a second message (MsgB); and
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.
13. The apparatus according to claim 9 , wherein the third processor circuitry is further configured to:
receive uplink grant information in the physical downlink control channel (PDCCH) addressed to a cell radio network temporary identifier (C-RNTI), the uplink grant information being used to schedule a hybrid automatic repeat request (HARQ) process of the uplink shared channel to be retransmitted; and
perform HARQ retransmission of the uplink shared channel according to the uplink grant information.
14. A random access apparatus, applicable to a terminal equipment, the apparatus comprising third processor circuitry, wherein the third processor circuitry is configured to:
receive two-step contention-free random access resource configuration transmitted by a network device for a first message (MsgA);
transmit to the network device the first message (MsgA) of a two-step contention-free random access procedure, the first message comprising a two-step contention-free random access preamble and a physical uplink shared channel; and
when receiving a second message (MsgB) transmitted by the network device, determine that the random access response is successfully received and consider this random access successfully completed,
wherein the receiving the second message (MsgB) transmitted by the network device comprises:
a media access control layer protocol data unit (MAC PDU) scheduled by a physical downlink control channel addressed to the second message radio network temporary identifier (MsgB-RNTI) is successfully demodulated, and a random access preamble identifier (RAPID) in a sub-protocol data unit (subPDU) in the media access control layer protocol data unit (MAC PDU) matches the two-step contention-free random access preamble transmitted by the terminal equipment, and
wherein the sub-protocol data unit (subPDU) at least contains a timing advance command (TAC).
15. The apparatus according to claim 14 , wherein,
the subPDU further contains uplink grant information, and
the third processor circuitry further retransmits the uplink shared channel of the first message (MsgA) according to the uplink grant information.
16. The apparatus according to claim 13 , wherein the third processor circuitry is further configured to:
when the second message (msgB) is not received and when the uplink grant information used for scheduling the retransmission of the physical uplink shared channel (PUSCH) is received, not retransmitting the physical uplink shared channel (PUSCH) according to the uplink grant information.