Enhancements on random access for NR-unlicensed

1. An apparatus configured to be employed in a User Equipment (UE) for new radio (NR) communications comprising:

one or more processors configured to:

configure physical resource blocks (PRBs) in a physical random access channel (PRACH) based on an occupied channel bandwidth (OCB) of an unlicensed band in an NR unlicensed (NR-U) communication;

allocate an amount of power for a unit bandwidth on a single PRB, wherein adjacent PRBs to the single PRB in a same interlace are separated by the unit bandwidth; and

generate a random access channel transmission in the PRACH by interlacing the PRBs defining the PRACH;

a radio frequency (RF) interface, configured to provide, to RF circuitry, data for processing the PRACH in the NR-U communication based on the interlaced PRBs.

2. The apparatus of claim 1 , wherein the one or more processors are further configured to generate the PRACH based on a regulation of the OCB, wherein the regulation of the OCB comprises the random access channel transmission occupying more than eighty percent of a nominal channel bandwidth that is defined for the PRACH.

3. The apparatus of claim 1 , wherein the one or more processors are further configured to:

equally space the interlaced PRBs of the PRACH, or irregularly space the interlaced PRBs of the PRACH by allocating at least two interlaces comprising an equi-distance between PRBs and selecting randomly a number of PRBs from the at least two interlaces.

4. The apparatus of claim 1 , wherein the one or more processors are further configured to:

generate a random access preamble transmission in the PRACH based only on a short sequence of a short sequence length L-139 of subcarriers, and a subcarrier spacing being a same as a data channel.

5. The apparatus of claim 1 , wherein the one or more processors are further configured to:

generate a random access preamble transmission comprising an interlace for the PRACH that comprises twelve PRBs as a short sequence preamble transmission.

6. The apparatus of claim 1 , wherein the one or more processors are further configured to:

generate up to three random access channel transmissions in different PRACH occasions within a slot of the PRACH.

7. The apparatus of claim 6 , wherein the one or more processors are further configured to:

generate a gap between the different PRACH occasions based on one or more preamble formats wherein the gap comprising a longer gap than a defined gap of NR licensed band specified in Release 15 of 3GPP Technical Standards.

8. The apparatus of claim 1 , wherein the one or more processors are further configured to:

perform a single interval LBT procedure or a Cat-4 LBT procedure to transmit or receive the PRACH comprising at least one of: an MSG 1, a message 2 (MSG 2), a message 3 (MSG 3), or a message 4 (MSG 4).

9. The apparatus of claim 8 , wherein the one or more processors are further configured to:

perform the single interval LBT procedure or the Cat-4 LBT procedure to transmit or receive at least one of the MSG 2, the MSG 3, or the MSG 4, in response to the at least one of: the MSG 2, the MSG 3, or the MSG 4 not being multiplexed with other unicast data.

10. The apparatus of claim 1 , wherein the one or more processors are further configured to:

process an indication of a validity timer from a UL grant in a MSG 2 to schedule an MSG 3 transmission with a LBT procedure;

in response to an expiration of the validity timer, generate a MSG 1 transmission; and

within the validity timer, schedule the MSG 3 in one or more scheduled slots based on the UL grant.

11. The apparatus of claim 1 , wherein the one or more processors are further configured to not increase at least one of: an NR preamble_transmission_counter, or a preamble_power_ramping_counter, in response to an LBT procedure failing for an MSG 1 transmission.

12. The apparatus of claim 1 , wherein the one or more processors are further configured to:

process a plurality of PRACH resources in a frequency and a time domain based on corresponding LBT procedures; and

based on one or more successes of the LBT procedures, selecting a PRACH resource, and in response to a plurality of successes of the LBT procedure occurring, randomly selecting or selecting with a priority based on an order in frequency/time of the PRACH resource for transmission of the PRACH.

13. A computer readable storage device storing executable instructions that, in response to execution, cause one or more processors of a user equipment (UE) to perform operations, the operations comprising:

configuring a physical random access channel (PRACH) over physical resource blocks (PRBs) that are interlaced in an unlicensed band in an NR unlicensed (NR-U) communication;

allocating an amount of power for a unit bandwidth on a single PRB, wherein adjacent PRBs to the single PRB in a same interlace are separated by the unit bandwidth and

transmitting a random access channel transmission in the PRACH by interlacing the PRBs defining the PRACH in the unlicensed band.

14. The computer readable storage device of claim 13 , wherein the operations further comprise:

equally spacing the interlaced PRBs of the PRACH, or irregularly spacing the interlaced PRBs of the PRACH by allocating at least two interlaces comprising an equi-distance between PRBs and selecting randomly a number of PRBs from the at least two interlaces.

15. The computer readable storage device of claim 13 , wherein the operations further comprise:

configuring a distance between the adjacent PRBs of the interlaced PRBs for the PRACH by at least 1 MHz from one another.

16. The computer readable storage device of claim 13 , wherein the operations further comprise:

generating a random access preamble transmission in the PRACH based only on a short sequence of a short sequence length L-139 of subcarriers, and a subcarrier spacing being a same as a data channel.

17. The computer readable storage device of claim 13 , wherein the operations further comprise:

generating up to three random access channel transmissions in different PRACH occasions within a slot of the PRACH.

18. An apparatus configured to be employed in a next generation NodeB (gNB) for new radio (NR) communications comprising:

one or more processors configured to:

configure physical resource blocks (PRBs) in a physical random access channel (PRACH) based on an occupied channel bandwidth (OCB) of an unlicensed band in an NR unlicensed (NR-U) communication;

generate a gap between different PRACH occasions based on one or more preamble formats wherein the gap comprises a longer gap than a defined gap of NR licensed band specified in Release 15 of 3GPP Technical Standards; and

generate a random access channel transmission in the PRACH by interlacing the PRBs defining the PRACH;

a radio frequency (RF) interface, configured to provide, to RF circuitry, data for processing the PRACH in the NR-U communication based on the interlaced PRBs.