Random access method and apparatus and communication system
Embodiments of this disclosure provide a random access method and apparatus and a system. The method includes: a terminal equipment selects (or determines) a first downlink reference signal and/or a second downlink reference signal, there existing a quasi co-location (QCL) relationship between the first downlink reference signal and the second downlink reference signal; and the terminal equipment determines a random access resource according to the first downlink reference signal and/or the second downlink reference signal.
1. A random access apparatus, configured in a terminal equipment for operation with shared spectrum, the apparatus comprising:
a memory; and
processor circuitry coupled with the memory, and configured to:
select a value associated with a first downlink reference signal and a second downlink reference signal, there existing a quasi co-location (QCL) relationship between the first downlink reference signal and the second downlink reference signal; and
determine a random access resource according to the value,
wherein there exists a QCL relationship between the first downlink reference signal and the second downlink reference signal refers to that the value of A modulo Q to which the first downlink reference signal corresponds is identical to the value of A modulo Q to which the second downlink reference signal corresponds, A being a sequence index of a physical broadcast channel downlink demodulation reference signal (PBCH DMRS), and Q being a parameter or a fixed value configured by a network device.
2. The apparatus according to claim 1 , wherein the processor circuitry is further configured to set a random access preamble according to the value associated with the first downlink reference signal and the second downlink reference signal.
3. The apparatus according to claim 2 , wherein, the processor circuitry is further configured to set an index of the random access preamble to be a random access preamble index (ra-PreambleIndex) to which the value correspond(s).
4. The apparatus according to claim 2 , wherein the processor circuitry is further configured to:
select a random access preamble according to the value associated with the first downlink reference signal and the second downlink reference signal; and
the set the index of the random access preamble to be an index of the random access preamble selected by the processor circuitry.
5. The apparatus according to claim 1 , wherein the processor circuitry is further configured to select a value associated with a first downlink reference signal and a second downlink reference signal, the first downlink reference signal and the second downlink reference signal satisfy at least one of the following conditions that:
RSRP of the first downlink reference signal is above a threshold;
RSRP of the second downlink reference signal is above a threshold;
the first downlink reference signal is included in a reference signal list used for configuring candidate beam for beam failure recovery;
the second downlink reference signal is included in a reference signal list used for configuring candidate beam for beam failure recovery;
the first downlink reference signal is indicated by a network device via a downlink control information;
the second downlink reference signal is indicated by a network device via a downlink control information;
a contention-free random access resource associated with the first downlink reference signal is indicated by random access channel dedicated configuration information;
a contention-free random access resource associated with the second downlink reference signal is indicated by random access channel dedicated configuration information;
the first downlink reference signal is not configured with a contention-free random access resource or the first downlink reference signal is used for a contention-based random access preamble selection procedure; and
the second downlink reference signal is not configured with a contention-free random access resource or the second downlink reference signal is used for a contention-based random access preamble selection procedure.
6. The apparatus according to claim 1 , wherein the random access resource is a PRACH occasion, and the processor circuitry determines a next available PRACH occasion from consecutive PRACH occasions, the consecutive PRACH occasions referring to PRACH occasions corresponding to the first downlink reference signal, or
PRACH occasions corresponding to the second downlink reference signal, or an intersection of PRACH occasions corresponding to the first downlink reference signal and PRACH occasions corresponding to the second downlink reference signal, or a union of PRACH occasions corresponding to the first downlink reference signal and PRACH occasions corresponding to the second downlink reference signal.
7. The apparatus according to claim 1 , wherein the processor circuitry is further configured to, if there exists a QCL relationship between a downlink reference signal selected by the processor circuitry and a third downlink reference signal, increment a counter related to power ramping by 1, the third downlink reference signal being a downlink reference signal selected in the last random access preamble transmission.
8. The apparatus according to claim 7 , wherein the downlink reference signal selected by the processor circuitry is an SSB, the third downlink reference signal is an SSB, and there exists a QCL relationship between the downlink reference signal SSB selected by the processor circuitry and the third downlink reference signal SSB.
9. A configuration apparatus, configured in a network device, the apparatus comprising:
a transmitter configured to transmit first configuration information and/or second configuration information and/or third configuration information to a terminal equipment;
wherein, the first configuration information comprises one or more pieces of the following information:
a first downlink reference signal and/or a second downlink reference signal, there existing a QCL relationship between the first downlink reference signal and the second downlink reference signal; and
a random access preamble index, a random access preamble to which the random access preamble index corresponds being used for the first downlink reference signal or the second downlink reference signal in determining candidate beams;
the second configuration information comprises one or more pieces of the following information:
random access channel dedicated configuration information, the random access channel dedicated configuration information indicating contention-free random access resource(s) associated with the first downlink reference signal and/or the second downlink reference signal;
identification of the first downlink reference signal or the second downlink reference signal, wherein the first downlink reference signal or the second downlink reference signal is a reference signal transmitted by a serving cell, and when the terminal equipment selects the first downlink reference signal and/or the second downlink reference signal, a random access preamble(s) to which the first downlink reference signal and/or the second downlink reference signal correspond(s) is/are available; and
a random access preamble index, a random access preamble to which the random access preamble index corresponds being used for the first downlink reference signal or the second downlink reference signal in determining candidate beams;
the third configuration information comprises one or more pieces of the following information:
a random access preamble index; and
an index of a synchronization signal or a broadcast channel.
10. The apparatus according to claim 9 , wherein the first configuration information is a beam failure recovery configuration information element, the second configuration information is a random access channel dedicated configuration information element, and the third configuration information is a downlink control information (DCI).
11. The apparatus according to claim 9 , wherein when the first configuration information comprises the first downlink reference signal, the first downlink reference signal or the second downlink reference signal identifies candidate beams used for beam failure recovery and random access parameters associated therewith.
12. The apparatus according to claim 9 , wherein the random access preamble index is a preamble index used by the terminal equipment in selecting the candidate beams identified by the first downlink reference signal or the second downlink reference signal to perform BFR.
13. The apparatus according to claim 9 , wherein the random access preamble index is a preamble index used by the terminal equipment in selecting the candidate beams identified by the first downlink reference signal or the second downlink reference signal to perform CFRA.
14. The apparatus according to claim 9 , wherein the contention-free random access resource is a RACH occasion, and if Q=1 or Q is not notified or the contention-free random access resource is in an unlicensed frequency band, the number of reference signals of each RACH occasion is ssb-perRACH-Occasion.