Random access in new radio (NR) and other beamforming systems
A wireless transmit/receive unit (WTRU) may receive, from a base station, a synchronization signal/physical broadcast channel (SS/PBCH) block transmission. The WTRU may transmit using a physical random access channel (PRACH) resource. Further, the PRACH resource may be determined based on an SS/PBCH block index. Also, the SS/PBCH block index may be determined based on information associated with the SS/PBCH block transmission. In a further example, the information associated with the PBCH block may be derived from a demodulation reference signal (DMRS) sequence. In another example, the DMRS sequence may be a PBCH DMRS sequence. Also, the information associated with the PBCH block may be derived from PBCH payload bits. Further, the SS/PBCH block index may be associated with a beam. In addition, SS/PBCH transmissions of different beams may be transmitted at different times. Further, the PRACH resource may include a preamble resource, a time resource and a frequency resource.
1. A wireless transmit/receive unit (WTRU) comprising:
a processor configured to:
receive a synchronization signal (SS)/physical broadcast channel (PBCH) block transmission;
determine an SS/PBCH block index based on information associated with the SS/PBCH block transmission;
determine a physical random access channel (PRACH) resource based on the determined SS/PBCH block index;
transmit a first message, the first message comprising a PRACH preamble and a grant-less physical uplink shared channel (PUSCH)), wherein the PRACH preamble is associated with a 2-step random access procedure and the PRACH preamble is transmitted using the determined PRACH resource; and
receive a second message in response to the first message, the second message comprising a contention resolution.
2. The WTRU of claim 1 , wherein the information associated with the SS/PBCH block transmission is derived from a demodulation reference signal (DMRS) sequence.
3. The WTRU of claim 2 , wherein the DMRS sequence is transmitted in the SS/PBCH block transmission.
4. The WTRU of claim 1 , wherein the information associated with the SS/PBCH block transmission is derived from one or more PBCH payload bits.
5. The WTRU of claim 1 , wherein the SS/PBCH block index corresponds to a subset of beams.
6. The WTRU of claim 5 , wherein the subset of beams comprises a single beam.
7. The WTRU of claim 6 , wherein one or more payload bits are used to indicate the single beam.
8. The WTRU of claim 1 , wherein the PRACH resource includes one or more of preamble resources, time resources and frequency resources.
9. The WTRU of claim 1 , wherein the PRACH resource is determined based on the SS/PBCH index using one or more of a time resource or a frequency resource.
10. A method comprising:
receiving a synchronization signal (SS)/physical broadcast channel (PBCH) block transmission;
determining an SS/PBCH block index based on information associated with the SS/PBCH block transmission;
determining a physical random access channel (PRACH) resource based on the determined SS/PBCH block index;
transmitting a first message, the first message comprising a PRACH preamble and a grant-less physical uplink shared channel (PUSCH), wherein the PRACH preamble is associated with a 2-step random access procedure that is transmitted using the determined PRACH resource; and
receiving a second message in response to the first message, the second message comprising a contention resolution.
11. The method of claim 10 , wherein the information associated with the SS/PBCH block transmission is derived from a demodulation reference signal (DMRS) sequence.
12. The method of claim 11 , wherein the DMRS sequence is transmitted in the SS/PBCH block transmission.
13. The method of claim 10 , wherein the information associated with the SS/PBCH block transmission is derived from one or more PBCH payload bits.
14. The method of claim 10 , wherein the SS/PBCH block index corresponds to a subset of beams.
15. The method of claim 14 , wherein the subset of beams comprises a single beam.
16. The method of claim 15 , wherein one or more payload bits are used to indicate the single beam.
17. The method of claim 10 , wherein the PRACH resource includes one or more of preamble resources, time resources and frequency resources.
18. The method of claim 10 , wherein the PRACH resource is determined based on the SS/PBCH index using one or more of a time resource or a frequency resource.
19. A base station comprising a processor configured to:
transmit a synchronization signal (SS)/physical broadcast channel (PBCH) block transmission;
receive a first message, the first message comprising a physical random access channel (PRACH) preamble and a grant-less physical uplink shared channel (PUSCH), wherein the PRACH preamble is associated with a 2-step random access procedure and the PRACH preamble is received using a PRACH resource, wherein:
the SS/PBCH block transmission is associated with a SS/PBCH block index, and
the SS/PBCH block index is associated with the PRACH resource; and
transmit a second message in response to the first message, the second message comprising an indication of contention resolution.