Beam frequency effective regions for initial access

1 . A base station for wireless communication, comprising:

at least one memory; and

at least one processor coupled with the at least one memory and configured to cause the base station to:

transmit a plurality of synchronization signal block (SSB) bursts within each beam frequency effective region of a plurality of beam frequency effective regions within a carrier frequency bandwidth (BW) and in accordance with a frequency region configuration, wherein each SSB burst comprises a plurality of SSBs, wherein a number of the plurality of beam frequency effective regions is based at least in part on a width of each beam frequency effective region;

associate a respective random access channel (RACH) occasion (RO) with each beam frequency effective region of an SSB transmission based at least in part on the frequency region configuration;

receive a physical RACH (PRACH) transmission from a user equipment (UE) during an RO;

determine a respective beam frequency effective region associated with the UE based on a PRACH configuration and the PRACH transmission; and

establish a connection with the UE using resources associated with the respective beam frequency effective region.

2 . The base station of claim 1 , wherein the frequency region configuration indicates:

a number of beam frequency effective regions;

a resource block (RB) length of one or more beam frequency effective regions;

an RB start of a lowest-indexed beam frequency effective region;

an RB start of a first beam frequency effective region;

an RB start of each beam frequency effective region;

a periodicity of the plurality of beam frequency effective regions;

a semi-static, periodic, or aperiodic pattern of the plurality of beam frequency effective regions;

or a combination thereof.

3 . The base station of claim 1 , wherein the plurality of beam frequency effective regions comprises non-overlapping frequency regions or one or more partially overlapping frequency regions.

4 . The base station of claim 1 , wherein the at least one processor is configured to cause the base station to transmit an SSB burst of the plurality of SSB bursts for each beam frequency effective region in the carrier frequency BW and based at least in part on a time shift from a reference SSB burst or a frequency shift from the reference SSB burst, or a combination thereof.

5 . The base station of claim 1 , wherein a respective SSB of an SSB burst is associated with a plurality of PRACH resource occasions within a corresponding RO, wherein each PRACH resource occasion comprises a PRACH preamble subset, and wherein each PRACH preamble subset is associated with a configured beam frequency effective region.

6 . The base station of claim 1 , wherein the at least one processor is configured to cause the base station to separately indicate a respective SSB-to-RO mapping for each SSB burst and RO within each beam frequency effective region.

7 . The base station of claim 1 , wherein the frequency region configuration indicates an SSB transmission pattern associated with one or more of:

a time periodicity;

a number of SSBs;

a number of simultaneously transmitted SSBs;

a time-frequency resources of one or more of SSBs;

a frequency offset of an SSB to a reference subcarrier, or reference resource block (RB), or a reference SSB;

a time gap between two adjacent SSBs;

a frequency domain bitmap indicator for transmitted SSBs, or muted SSBs, or both;

a time domain bitmap indicator for transmitted SSBs, or muted SSBs, or both;

or a combination thereof.

8 . The base station of claim 7 , wherein the at least one processor is configured to cause the base station to transmit the plurality of SSB bursts in accordance with a beam sweeping pattern for the plurality of beam frequency effective regions, wherein the beam sweeping pattern repeats the SSB transmission using a same spatial filter and within a group of ROs prior to different SSB transmissions during different groups of ROs.

9 . The base station of claim 8 , wherein the beam sweeping pattern comprises an interleaved pattern of the plurality of beam frequency effective regions and configured SSB bursts.

10 . The base station of claim 1 , wherein the frequency region configuration indicates a first set of cell-defining SSBs (CD-SSBs) and a second set of non-cell-defining SSBs (NCD-SSBs).

11 . The base station of claim 1 , wherein a respective beam frequency effective region corresponds to an antenna panel with an array of antenna elements, wherein the respective beam frequency effective region comprises a plurality of subcarriers having an array beam gain that satisfies a beam gain threshold.

12 . The base station of claim 11 , wherein a precoder of the base station comprises multiple radio frequency (RF) chains and a number of time delay (TD) units insufficient to satisfy the beam gain threshold over the carrier frequency BW.

13 . A method performed by a base station, the method comprising:

transmitting a plurality of synchronization signal block (SSB) bursts within each beam frequency effective region of a plurality of beam frequency effective regions within a carrier frequency bandwidth (BW) and in accordance with a frequency region configuration, wherein each SSB burst comprises a plurality of SSBs, wherein a number of the plurality of beam frequency effective regions is based at least in part on a width of each beam frequency effective region;

associating a respective random access channel (RACH) occasion (RO) with each beam frequency effective region of an SSB transmission based at least in part on the frequency region configuration;

receiving a physical RACH (PRACH) transmission from a user equipment (UE) during an RO;

determining a respective beam frequency effective region associated with the UE based on a PRACH configuration and the PRACH transmission; and

establishing a connection with the UE using resources associated with the respective beam frequency effective region.

14 . The method of claim 13 , wherein the frequency region configuration indicates one or more of:

a number of beam frequency effective regions;

a resource block (RB) length of one or more beam frequency effective regions;

an RB start of a lowest-indexed beam frequency effective region;

an RB start of a first beam frequency effective region;

an RB start of each beam frequency effective region;

a periodicity of the plurality of beam frequency effective regions;

a semi-static, periodic, or aperiodic pattern of the plurality of beam frequency effective regions;

or a combination thereof.

15 . The method of claim 13 , further comprising transmitting an SSB burst of the plurality of SSB bursts for each beam frequency effective region in the carrier frequency BW and based at least in part on a time shift from a reference SSB burst or a frequency shift from the reference SSB burst, or a combination thereof.

16 . The method of claim 13 , wherein a respective SSB of the SSB burst is associated with a plurality of PRACH resource occasions within a corresponding RO, wherein each PRACH resource occasion comprises a PRACH preamble subset, and wherein each PRACH preamble subset is associated with a configured beam frequency effective region.

17 . The method of claim 13 , further comprising separately indicating a respective SSB-to-RO mapping for each SSB burst and RO within each beam frequency effective region.

18 . The method of claim 13 , wherein the frequency region configuration indicates an SSB transmission pattern associated with one or more of:

a time periodicity;

a number of SSBs;

a number of simultaneously transmitted SSBs;

a time-frequency resources of one or more of SSBs;

a frequency offset of an SSB to a reference subcarrier, or reference resource block (RB), or a reference SSB;

a time gap between two adjacent SSBs;

a frequency domain bitmap indicator for transmitted SSBs, or muted SSBs, or both;

a time domain bitmap indicator for transmitted SSBs, or muted SSBs, or both;

or a combination thereof.

19 . The method of claim 18 , further comprising transmitting the plurality of SSB bursts in accordance with a beam sweeping pattern for the plurality of beam frequency effective regions, wherein the beam sweeping pattern repeats the SSB transmission using a same spatial filter and within one or more ROs prior to different SSB transmissions during different ROs.

20 . A processor for wireless communication, comprising:

at least one controller coupled with at least one memory and configured to cause the processor to:

transmit a plurality of synchronization signal block (SSB) bursts within each beam frequency effective region of a plurality of beam frequency effective regions within a carrier frequency bandwidth (BW) and in accordance with a frequency region configuration, wherein each SSB burst comprises a plurality of SSBs, wherein a number of the plurality of beam frequency effective regions is based at least in part on a width of each beam frequency effective region;

associate a respective random access channel (RACH) occasion (RO) with each beam frequency effective region of an SSB transmission based at least in part on the frequency region configuration;

receive a physical RACH (PRACH) transmission from a user equipment (UE) during an RO;

determine a respective beam frequency effective region associated with the UE based on a PRACH configuration and the PRACH transmission; and

establish a connection with the UE using resources associated with the respective beam frequency effective region.