Performing a two-step random access channel procedure
Apparatuses, methods, and systems are disclosed for performing a two-step random access channel procedure. One method includes determining whether to perform a two-step random access channel procedure or a four-step random access channel procedure. The method includes, in response to determining to perform the two-step random access channel procedure: in a first step: transmitting a preamble in a first time slot; and transmitting an uplink data transmission via a physical uplink shared channel in a second time slot different from the first time slot; and, in a second step, receiving a response message corresponding to the first step, wherein the response message comprises a radio network temporary identifier.
1. A method comprising:
receiving configuration information from a network device indicating whether two-step random access resources are configured and whether four-step random access resources are configured;
determining whether to perform a two-step random access channel procedure or a four-step random access channel procedure based on a reference signal received power of a downlink pathloss reference and the configuration information, wherein the two-step random access channel procedure is determined to be performed in response to the reference signal received power being greater than a configured threshold and the configuration information indicating that two-step random access resources and four-step random access resources are configured; and
in response to determining to perform the two-step random access channel procedure:
in a first step:
transmitting a preamble in a first time instance; and
transmitting an uplink data transmission via a physical uplink shared channel in a second time instance different from the first time instance; and
in a second step, monitoring for a response message corresponding to the first step during a time window, wherein the response message is indicated by a radio network temporary identifier.
2. The method of claim 1 , wherein the radio network temporary identifier for the two-step random access channel procedure is calculated using a first formula, and a radio network temporary identifier for the four-step random access channel procedure is calculated using a second formula different from the first formula.
3. The method of claim 1 , wherein a physical uplink shared channel resource used for the uplink data transmission in the first step is linked to the preamble transmitted in the first step.
4. The method of claim 1 , wherein the uplink data transmission comprises a medium access control protocol data unit.
5. The method of claim 4 , further comprising storing the medium access control protocol data unit in a first buffer.
6. The method of claim 5 , wherein the medium access control protocol data unit is stored in a second buffer in response to switching from the two-step random access channel procedure to the four-step random access channel procedure.
7. The method of claim 6 , wherein the second buffer is a msg3 buffer.
8. The method of claim 1 , wherein the transmission of the preamble and the transmission of the uplink data transmission occur in different slots.
9. The method of claim 1 , wherein an offset between the transmission of the preamble and transmission of the uplink data transmission is configured by a network entity.
10. An apparatus comprising a user equipment, the apparatus further comprising:
a receiver that receives configuration information from a network device indicating whether two-step random access resources are configured and whether four-step random access resources are configured;
a processor that determines whether to perform a two-step random access channel procedure or a four-step random access channel procedure based on a reference signal received power of a downlink pathloss reference and the configuration information, wherein the two-step random access channel procedure is determined to be performed in response to the reference signal received power being greater than a configured threshold and the configuration information indicating that two-step random access resources and four-step random access resources are configured; and
a transmitter;
wherein in response to determining to perform the two-step random access channel procedure:
in a first step, the transmitter:
transmits a preamble in a first time instance; and
transmits an uplink data transmission via a physical uplink shared channel in a second time instance different from the first time instance; and
in a second step, the processor monitors for a response message corresponding to the first step during a time window, wherein the response message is indicated by a radio network temporary identifier.
11. The apparatus of claim 10 , wherein the radio network temporary identifier for the two-step random access channel procedure is calculated using a first formula, and a radio network temporary identifier for the four-step random access channel procedure is calculated using a second formula different from the first formula.
12. The apparatus of claim 10 , wherein a physical uplink shared channel resource used for the uplink data transmission in the first step is linked to the preamble transmitted in the first step.
13. The apparatus of claim 10 , wherein the receiver receives information configuring a requirement for performing the two-step random access channel procedure.
14. The apparatus of claim 13 , wherein the information indicates that the two-step random access channel procedure is allowed.
15. An apparatus comprising:
a transmitter that transmits configuration information from a network device indicating whether two-step random access resources are configured and whether four-step random access resources are configured; and
a receiver that receives a preamble in a first time instance and receives an uplink data transmission via a physical uplink shared channel in a second time instance different from the first time instance in response to a determination by a remote unit to perform a two-step random access channel procedure, wherein the determination by the remote unit to perform the two-step random access channel procedure is based on a reference signal received power of a downlink pathloss reference and the configuration information, and the two-step random access channel procedure is determined to be performed in response to the reference signal received power being greater than a configured threshold and the configuration information indicating that the two-step random access channel procedure and the four-step random access channel procedure are configured;
wherein the transmitter transmits a response message corresponding to the preamble, and the response message comprises a radio network temporary identifier.
16. The apparatus of claim 15 , wherein the transmitter transmits information configuring a requirement for performing the two-step random access channel procedure.
17. The apparatus of claim 16 , wherein the information indicates that the two-step random access channel procedure is allowed.
18. The apparatus of claim 16 , wherein the information indicates that the two-step random access channel procedure is required.
19. The apparatus of claim 15 , wherein the radio network temporary identifier for the two-step random access channel procedure is calculated using a first formula, and a radio network temporary identifier for the four-step random access channel procedure is calculated using a second formula different from the first formula.
20. The apparatus of claim 15 , wherein a physical uplink shared channel resource used for the uplink data transmission is linked to the preamble.