Multiplexing, addressing and HARQ for MsgB in two-step RACH in mobile communications

1. A method of a two-step random access (RA) procedure in New Radio (NR) mobile communications, comprising:

transmitting, by a processor of an apparatus implemented in a user equipment (UE), to a network node of a wireless network a first message containing data; and

receiving, by the processor responsive to transmitting the first message, from the network node a second message containing a random access response (RAR) and contention resolution information,

wherein the second message is addressed to a shared radio network temporary identifier (RNTI) responsive to a cell radio network temporary identifier (C-RNTI) being absent in the first message,

wherein the receiving of the second message comprises:

monitoring a physical downlink control channel (PDCCH) for the second message; and

stopping to monitor the PDCCH in an event of

the UE having received a retransmission request.

2. The method of claim 1 , wherein the receiving of the second message comprises receiving one or more partitions of a plurality of partitions of the second message that are addressed to the shared RNTI which comprises a random access RNTI (RA-RNTI).

3. The method of claim 2 , wherein the receiving of the one or more partitions of the plurality of partitions of the second message comprises:

monitoring a physical downlink control channel (PDCCH) for at least the one or more partitions of the plurality of partitions of the second message; and

stopping to monitor the PDCCH in an event that at least one of a plurality of conditions is met.

4. The method of claim 3 , wherein the plurality of conditions comprise:

the UE having completed the RA procedure;

the UE having received a retransmission request;

the UE having been addressed in the one or more partitions of the plurality of partitions of the second message with a random access preamble identifier (RAPID) or a radio network temporary identifier (RNTI) from the first message; and

expiration of a window of time for the monitoring.

5. The method of claim 1 , with the second message being addressed to the C-RNTI of the UE or another unique identifier (ID) of the UE, further comprising:

transmitting, by the processor, a hybrid automatic repeat request negative acknowledgement (HARQ-NACK) feedback to the network node to indicate failure in decoding the second message.

6. The method of claim 5 , with the transmitting of the HARQ-NACK feedback comprises transmitting the HARQ-NACK in a message part of a message formatted as the first message.

7. The method of claim 1 , with the second message being addressed to the C-RNTI of the UE or another unique identifier (ID) of the UE, further comprising:

transmitting, by the processor, a hybrid automatic repeat request acknowledgement (HARQ-ACK) feedback to the network node to indicate success in decoding the second message,

wherein no hybrid automatic repeat request negative acknowledgement (HARQ-NACK) feedback is transmitted to the network node responsive to failure in decoding the second message.

8. The method of claim 1 , with the second message being addressed to the shared RNTI, further comprising:

transmitting, by the processor, a hybrid automatic repeat request acknowledgement (HARQ-ACK) feedback to the network node to indicate success in completion of the contention resolution,

wherein no hybrid automatic repeat request negative acknowledgement (HARQ-NACK) feedback is transmitted to the network node responsive to failure in the completion of the contention resolution.

9. A method of a two-step random access (RA) procedure in New Radio (NR) mobile communications, comprising:

transmitting, by a processor of an apparatus implemented in a user equipment (UE), to a network node of a wireless network a first message containing data;

receiving, by the processor responsive to transmitting the first message, from the network node a second message containing a random access response (RAR) and contention resolution information; and

stopping, by the processor, monitoring a shared radio network temporary identifier (RNTI) responsive to receiving a retransmission request,

wherein the second message is addressed to a cell radio network temporary identifier (C-RNTI) of the UE responsive to:

the C-RNTI being indicated in the first message; and

the second message being transmitted to the UE and no other UE, and

wherein the second message is addressed to the shared RNTI responsive to the C-RNTI being absent in the first message,

wherein the receiving of the second message comprises receiving one or more partitions of a plurality of partitions of the second message that are addressed to the shared RNTI which comprises a random access radio network temporary identifier (RA-RNTI),

wherein the receiving of the one or more partitions of the plurality of partitions of the second message comprises:

monitoring a physical downlink control channel (PDCCH) for at least the one or more partitions of the plurality of partitions of the second message; and

stopping to monitor the PDCCH in an event that at least one of a plurality of conditions is met, and

wherein the plurality of conditions comprise:

the UE having received the retransmission request; and

the UE having been addressed in the one or more partitions of the plurality of partitions of the second message with a random access preamble identifier (RAPID) or a radio network temporary identifier (RNTI) from the first message.

10. The method of claim 9 , wherein the plurality of conditions further comprise:

the UE having completed the RA procedure; and

expiration of a window of time for the monitoring.

11. An apparatus implementable in a user equipment (UE), comprising:

a transceiver configured to wirelessly communicate with a network node of a wireless network;

a processor coupled to the transceiver and configured to perform operations comprising:

transmitting, via the transceiver, to the network node a first message containing data;

receiving, via the transceiver responsive to transmitting the first message, from the network node a second message containing a random access response (RAR) and contention resolution information; and

stopping monitoring a shared radio network temporary identifier (RNTI) responsive to receiving a retransmission request,

wherein the second message is addressed to the shared RNTI responsive to a cell radio network temporary identifier (C-RNTI) being absent in the first message,

wherein, in receiving the second message, the processor is configured to receive one or more partitions of a plurality of partitions of the second message that are addressed to the shared RNTI by:

monitoring a physical downlink control channel (PDCCH) for at least the one or more partitions of the plurality of partitions of the second message; and

stopping to monitor the PDCCH in an event that at least one of a plurality of conditions is met, and

wherein the plurality of conditions comprise:

the UE having received the retransmission request; and

the UE having been addressed in the one or more partitions of the plurality of partitions of the second message with a random access preamble identifier (RAPID) or a radio network temporary identifier (RNTI) from the first message.

12. The apparatus of claim 11 , wherein the second message is addressed to the C-RNTI of the UE responsive to both the C-RNTI being indicated in the first message and the second message being transmitted to the UE and no other UE, and wherein the second message is addressed to the shared RNTI responsive to either the C-RNTI being absent in the first message.

13. The apparatus of claim 11 , wherein the plurality of conditions further comprise:

the UE having completed the RA procedure; and

expiration of a window of time for the monitoring.

14. The apparatus of claim 11 , with the second message being addressed to the C-RNTI of the UE or another unique identifier (ID) of the UE, the processor is further configured to perform operations comprising:

transmitting, via the transceiver, a hybrid automatic repeat request negative acknowledgement (HARQ-NACK) feedback to the network node to indicate failure in decoding the second message.

15. The apparatus of claim 11 , with the second message being addressed to the C-RNTI of the UE or another unique identifier (ID) of the UE, the processor is further configured to perform operations comprising:

transmitting, via the transceiver, a hybrid automatic repeat request acknowledgement (HARQ-ACK) feedback to the network node to indicate success in decoding the second message,

wherein no hybrid automatic repeat request negative acknowledgement (HARQ-NACK) feedback is transmitted to the network node responsive to failure in decoding the second message.

16. The apparatus of claim 11 , with the second message being addressed to the shared RNTI, the processor is further configured to perform operations comprising:

transmitting, via the transceiver, a hybrid automatic repeat request acknowledgement (HARQ-ACK) feedback to the network node to indicate success in completion of the contention resolution,

wherein no hybrid automatic repeat request negative acknowledgement (HARQ-NACK) feedback is transmitted to the network node responsive to failure in the completion of the contention resolution.