Random access channel occasions

Abstract

A method, apparatus, and computer program are described comprising: obtaining a mapping between a first set of random access channel occasions, RACH occasions, and one or more synchronisation signal block, SSB, indices, the one or more SSB indices being associated with one or more respective SSB beams, and each RACH occasion of the first set corresponding to a set of resources for transmitting random access messages; obtaining a mapping between a second set of RACH occasions and the one or more SSB indices, each RACH occasion of the second set corresponding to a set of resources for transmitting random access messages, wherein the second set of RACH occasions comprises overlapping RACH occasions, wherein each of the overlapping RACH occasions corresponds to a set of resources that at least partially overlaps in time with resources corresponding to one or more RACH occasions of the first set; obtaining an indication of a maximum number of simultaneously active SSB beams supported by an access node; determining that the RACH occasions of the first and second set that correspond to sets of resources occupying a particular time or time period are mapped to a number of different SSB indices that exceeds the indicated maximum number of simultaneously active SSB beams supported by the access node; and responsive to making said determination, deprioritising at least one overlapping RACH occasion of the second set of RACH occasions such that, the RACH occasions of the first and second set that are not deprioritised, and that correspond to sets of resources occupying the particular time or time period, shall not be mapped to a number of different SSB indices that exceed the determined maximum number of simultaneously active SSB beams supported by the access node.

Description

[0001] Random Access Channel Occasions

[0002] Field

[0003] Example embodiments may relate to devices, access nodes, and methods for carrying out random-access procedures in radio access networks.

[0004] Background

[0005] There remains an interest in improving the performance and flexibility of random-access procedures in radio access networks.

[0006] Summary

[0007] The scope of protection sought for various embodiments of the invention is set out by the independent claims. The embodiments and features, if any, described in this specification that do not fall under the scope of the independent claims are to be interpreted as examples useful for understanding various embodiments of the invention.

[0008] A first aspect provides a device comprising: means for obtaining a mapping between a first set of random access channel occasions, RACH occasions, and one or more synchronisation signal block, SSB, indices, the one or more SSB indices being associated with one or more respective SSB beams, and each RACH occasion of the first set corresponding to a set of resources for transmitting random access messages; means for obtaining a mapping between a second set of RACH occasions and the one or more SSB indices, each RACH occasion of the second set corresponding to a set of resources for transmitting random access messages, wherein the second set of RACH occasions comprises overlapping RACH occasions, wherein each of the overlapping RACH occasions corresponds to a set of resources that at least partially overlaps in time with resources corresponding to one or more RACH occasions of the first set; means for obtaining an indication of a maximum number of simultaneously active SSB beams supported by an access node; means for determining that the RACH occasions of the first and second set that correspond to sets of resources occupying a particular time or time period are mapped to a number of different SSB indices that exceeds the indicated maximum number of simultaneously active SSB beams supported by the access node; and means for, responsive to making said determination, deprioritising at least one overlapping RACH occasion of the second set of RACH occasions such that the RACH occasions of the first and second set that are not deprioritised, and that correspond to sets of resources occupying the particular time or time period, shall not be mapped to a number of different SSB indices that exceeds the determined maximum number of simultaneously active SSB beams supported by the access node.

[0009] In some example embodiments, the device further comprises means for transmitting a random access message on the set of resources corresponding to at least one of the RACH occasions that is not deprioritised.

[0010] In some example embodiments, the means for obtaining an indication of a maximum number of simultaneously active beams supported by the access node are configured to: determine that the maximum number of simultaneously active beams supported by the access node has not been explicitly indicated to the device by the access node; and infer from said determination that the maximum number of simultaneously active beams supported by the access node is the maximum number of different SSB indices mapped to RACH occasions of the first set that correspond to resources occupying a particular time instant.

[0011] In some example embodiments, the means for obtaining an indication of a maximum number of simultaneously active beams supported by the access node are configured to: receive from the access node a message comprising an explicit indication of the maximum number of simultaneously active beams supported by the access node.

[0012] In some example embodiments, deprioritising overlapping RACH occasions comprises determining a number of SSB indices mapped to RACH occasions of the first set of RACH occasions corresponding to resources occupying the particular time or time period.

[0013] In some example embodiments, deprioritising overlapping RACH occasions comprises determining a number of SSB indices mapped to RACH occasions of the second set of RACH occasions corresponding to resources occupying the particular time or time period.

[0014] In some example embodiments, deprioritising overlapping RACH occasions comprises deprioritising RACH occasions of the second set of RACH occasions until the total number of SSB indices mapped to RACH occasions of the first and second sets of RACH occasions that correspond to resources occupying the particular time or time period does not exceed the determined maximum number of simultaneously active beams supported by the access node.

[0015] In some example embodiments, deprioritising RACH occasions of the second set of RACH occasions is performed in ascending order of SSB index mapped to each RACH occasion corresponding to resources occupying the period of overlap.

[0016] In some example embodiments, deprioritising RACH occasions of the second set of RACH occasions is performed in descending order of SSB index mapped to each RACH occasion corresponding to resources occupying the period of overlap.

[0017] In some example embodiments, the device further comprises means for reprioritising deprioritised RACH occasions of the second set of RACH occasions, wherein reprioritising a deprioritised RACH occasion comprises: selecting an SSB index mapped to a RACH occasion of the first or second set that is not deprioritised and that corresponds to a set of resources that overlaps in time with resources corresponding to the deprioritised RACH occasion; remapping the deprioritised RACH occasion to the selected SSB index; and reprioritising the remapped RACH occasion.

[0018] In some example embodiments, for each RACH occasion of the second set of RACH occasions, at least a portion of the set of resources corresponding to that RACH occasion are in a sub-band full duplex time slot.

[0019] In some example embodiments, for each RACH occasion of the first set of RACH occasions, the set of resources corresponding to that RACH occasion are within one or more uplink time slots.

[0020] In some example embodiments each overlapping RACH occasion of the second set of RACH occasions corresponds to a set of resources comprising resources in an uplink time slot and resources in a sub-band full duplex time slot, wherein at least a portion of the resources in an uplink time slot overlap with resources corresponding to one or more RACH occasions of the first set of RACH occasions.

[0021] A second aspect provides a method comprising : obtaining a mapping between a first set of random access channel occasions, RACH occasions, and one or more synchronisation signal block, SSB, indices, the one or more SSB indices being associated with one or more respective SSB beams, and each RACH occasion of the first set corresponding to a set of resources for transmitting random access messages; obtaining a mapping between a second set of RACH occasions and the one or more SSB indices, each RACH occasion of the second set corresponding to a set of resources for transmitting random access messages, wherein the second set of RACH occasions comprises overlapping RACH occasions, wherein each of the overlapping RACH occasions corresponds to a set of resources that at least partially overlaps in time with resources corresponding to one or more RACH occasions of the first set; obtaining an indication of a maximum number of simultaneously active SSB beams supported by an access node; determining that the RACH occasions of the first and second set that correspond to sets of resources occupying a particular time or time period are mapped to a number of different SSB indices that exceeds the indicated maximum number of simultaneously active SSB beams supported by the access node; and responsive to making said determination, deprioritising at least one overlapping RACH occasion of the second set of RACH occasions such that the RACH occasions of the first and second set that are not deprioritised, and that correspond to sets of resources occupying the particular time or time period, shall not be mapped to a number of different SSB indices that exceed the determined maximum number of simultaneously active SSB beams supported by the access node.

[0022] In some example embodiments, the method further comprises transmitting a random access message on the set of resources corresponding to at least one of the RACH occasions that is not deprioritised.

[0023] In some example embodiments, obtaining an indication of a maximum number of simultaneously active beams supported by the access node comprises: determining that the maximum number of simultaneously active beams supported by the access node has not been explicitly indicated to the device by the access node; and inferring from said determination that the maximum number of simultaneously active beams supported by the access node is the maximum number of different SSB indices mapped to RACH occasions of the first set that correspond to resources occupying a particular time instant.

[0024] In some example embodiments, obtaining an indication of a maximum number of simultaneously active beams supported by the access node comprises: receiving from the access node a message comprising an explicit indication of the maximum number of simultaneously active beams supported by the access node.

[0025] In some example embodiments, deprioritising overlapping RACH occasions comprises determining a number of SSB indices mapped to RACH occasions of the first set of RACH occasions corresponding to resources occupying the particular time or time period.

[0026] In some example embodiments, deprioritising overlapping RACH occasions comprises determining a number of SSB indices mapped to RACH occasions of the second set of RACH occasions corresponding to resources occupying the particular time or time period. In some example embodiments, deprioritising overlapping RACH occasions comprises deprioritising RACH occasions of the second set of RACH occasions until the total number of SSB indices mapped to RACH occasions of the first and second sets of RACH occasions that correspond to resources occupying the particular time or time period does not exceed the determined maximum number of simultaneously active beams supported by the access node.

[0027] In some example embodiments, deprioritising RACH occasions of the second set of RACH occasions is performed in ascending order of SSB index mapped to each RACH occasion corresponding to resources occupying the period of overlap.

[0028] In some example embodiments, deprioritising RACH occasions of the second set of RACH occasions is performed in descending order of SSB index mapped to each RACH occasion corresponding to resources occupying the period of overlap.

[0029] In some example embodiments, the method further comprises reprioritising deprioritised RACH occasions of the second set of RACH occasions, wherein reprioritising a deprioritised RACH occasion comprises: selecting an SSB index mapped to a RACH occasion of the first or second set that is not deprioritised and that corresponds to a set of resources that overlaps in time with resources corresponding to the deprioritised RACH occasion; remapping the deprioritised RACH occasion to the selected SSB index; and reprioritising the remapped RACH occasion.

[0030] In some example embodiments, for each RACH occasion of the second set of RACH occasions, at least a portion of the set of resources corresponding to that RACH occasion are in a sub-band full duplex time slot.

[0031] In some example embodiments, for each RACH occasion of the first set of RACH occasions, the set of resources corresponding to that RACH occasion are within one or more uplink time slots.

[0032] In some example embodiments each overlapping RACH occasion of the second set of RACH occasions corresponds to a set of resources comprising resources in an uplink time slot and resources in a sub-band full duplex time slot, wherein at least a portion of the resources in an uplink time slot overlap with resources corresponding to one or more RACH occasions of the first set of RACH occasions. A third aspect provides a computer program comprising a set of instructions which, when executed on an apparatus, is configured to cause the apparatus to carry out a method comprising: obtaining a mapping between a first set of random access channel occasions, RACH occasions, and one or more synchronisation signal block, SSB, indices, the one or more SSB indices being associated with one or more respective SSB beams, and each RACH occasion of the first set corresponding to a set of resources for transmitting random access messages; obtaining a mapping between a second set of RACH occasions and the one or more SSB indices, each RACH occasion of the second set corresponding to a set of resources for transmitting random access messages, wherein the second set of RACH occasions comprises overlapping RACH occasions, wherein each of the overlapping RACH occasions corresponds to a set of resources that at least partially overlaps in time with resources corresponding to one or more RACH occasions of the first set; obtaining an indication of a maximum number of simultaneously active SSB beams supported by an access node; determining that the RACH occasions of the first and second set that correspond to sets of resources occupying a particular time or time period are mapped to a number of different SSB indices that exceeds the indicated maximum number of simultaneously active SSB beams supported by the access node; and responsive to making said determination, deprioritising at least one overlapping RACH occasion of the second set of RACH occasions such that the RACH occasions of the first and second set that are not deprioritised, and that correspond to sets of resources occupying the particular time or time period, shall not be mapped to a number of different SSB indices that exceed the determined maximum number of simultaneously active SSB beams supported by the access node.

[0033] In some example embodiments, the third aspect may include any other feature mentioned with respect to the method of the second aspect.

[0034] A fourth aspect provides a non-transitory computer-readable medium having stored thereon computer-readable code, which, when executed by at least one processor, causes the at least one processor to perform a method comprising: obtaining a mapping between a first set of random access channel occasions, RACH occasions, and one or more synchronisation signal block, SSB, indices, the one or more SSB indices being associated with one or more respective SSB beams, and each RACH occasion of the first set corresponding to a set of resources for transmitting random access messages; obtaining a mapping between a second set of RACH occasions and the one or more SSB indices, each RACH occasion of the second set corresponding to a set of resources for transmitting random access messages, wherein the second set of RACH occasions comprises overlapping RACH occasions, wherein each of the overlapping RACH occasions corresponds to a set of resources that at least partially overlaps in time with resources corresponding to one or more RACH occasions of the first set; obtaining an indication of a maximum number of simultaneously active SSB beams supported by an access node; determining that the RACH occasions of the first and second set that correspond to sets of resources occupying a particular time or time period are mapped to a number of different SSB indices that exceeds the indicated maximum number of simultaneously active SSB beams supported by the access node; and responsive to making said determination, deprioritising at least one overlapping RACH occasion of the second set of RACH occasions such that the RACH occasions of the first and second set that are not deprioritised, and that correspond to sets of resources occupying the particular time or time period, shall not be mapped to a number of different SSB indices that exceed the determined maximum number of simultaneously active SSB beams supported by the access node.

[0035] The fourth aspect may include any other feature mentioned with respect to the method of the second aspect.

[0036] A fifth aspect provides an apparatus, the apparatus having at least one processor and at least one memory having computer-readable code stored thereon which when executed controls the at least one processor to perform a method comprising : obtaining a mapping between a first set of random access channel occasions, RACH occasions, and one or more synchronisation signal block, SSB, indices, the one or more SSB indices being associated with one or more respective SSB beams, and each RACH occasion of the first set corresponding to a set of resources for transmitting random access messages; obtaining a mapping between a second set of RACH occasions and the one or more SSB indices, each RACH occasion of the second set corresponding to a set of resources for transmitting random access messages, wherein the second set of RACH occasions comprises overlapping RACH occasions, wherein each of the overlapping RACH occasions corresponds to a set of resources that at least partially overlaps in time with resources corresponding to one or more RACH occasions of the first set; obtaining an indication of a maximum number of simultaneously active SSB beams supported by an access node; determining that the RACH occasions of the first and second set that correspond to sets of resources occupying a particular time or time period are mapped to a number of different SSB indices that exceeds the indicated maximum number of simultaneously active SSB beams supported by the access node; and responsive to making said determination, deprioritising at least one overlapping RACH occasion of the second set of RACH occasions such that the RACH occasions of the first and second set that are not deprioritised, and that correspond to sets of resources occupying the particular time or time period, shall not be mapped to a number of different SSB indices that exceed the determined maximum number of simultaneously active SSB beams supported by the access node.

[0037] The fifth aspect may include any other feature mentioned with respect to the method of the second aspect.

[0038] A sixth aspect provides an apparatus comprising: means for indicating to a device a mapping between a first set of random access channel occasions, RACH occasions, and one or more synchronisation signal block, SSB, indices, the one or more SSB indices being associated with one or more respective SSB beams, and each RACH occasion of the first set corresponding to a set of resources for transmitting random access messages; means for indicating to the device a mapping between a second set of RACH occasions and the one or more SSB indices, each RACH occasion of the second set corresponding to a set of resources for transmitting random access messages, wherein the second set of RACH occasions comprises overlapping RACH occasions, wherein each of the overlapping RACH occasions corresponds to a set of resources that at least partially overlaps in time with resources corresponding to one or more RACH occasions of the first set; and means for indicating to the device a maximum number of simultaneously active SSB beams supported by the access node.

[0039] A seventh aspect provides a method comprising: indicating to a device a mapping between a first set of random access channel occasions, RACH occasions, and one or more synchronisation signal block, SSB, indices, the one or more SSB indices being associated with one or more respective SSB beams, and each RACH occasion of the first set corresponding to a set of resources for transmitting random access messages; indicating to the device a mapping between a second set of RACH occasions and the one or more SSB indices, each RACH occasion of the second set corresponding to a set of resources for transmitting random access messages, wherein the second set of RACH occasions comprises overlapping RACH occasions, wherein each of the overlapping RACH occasions corresponds to a set of resources that at least partially overlaps in time with resources corresponding to one or more RACH occasions of the first set; and indicating to the device a maximum number of simultaneously active SSB beams supported by the access node.

[0040] An eighth aspect provides a computer program comprising a set of instructions which, when executed on an apparatus, is configured to cause the apparatus to carry out a method comprising: indicating to a device a mapping between a first set of random access channel occasions, RACH occasions, and one or more synchronisation signal block, SSB, indices, the one or more SSB indices being associated with one or more respective SSB beams, and each RACH occasion of the first set corresponding to a set of resources for transmitting random access messages; indicating to the device a mapping between a second set of RACH occasions and the one or more SSB indices, each RACH occasion of the second set corresponding to a set of resources for transmitting random access messages, wherein the second set of RACH occasions comprises overlapping RACH occasions, wherein each of the overlapping RACH occasions corresponds to a set of resources that at least partially overlaps in time with resources corresponding to one or more RACH occasions of the first set; and indicating to the device a maximum number of simultaneously active SSB beams supported by the access node.

[0041] A ninth aspect provides a non-transitory computer-readable medium having stored thereon computer-readable code, which, when executed by at least one processor, causes the at least one processor to perform a method comprising: indicating to a device a mapping between a first set of random access channel occasions, RACH occasions, and one or more synchronisation signal block, SSB, indices, the one or more SSB indices being associated with one or more respective SSB beams, and each RACH occasion of the first set corresponding to a set of resources for transmitting random access messages; indicating to the device a mapping between a second set of RACH occasions and the one or more SSB indices, each RACH occasion of the second set corresponding to a set of resources for transmitting random access messages, wherein the second set of RACH occasions comprises overlapping RACH occasions, wherein each of the overlapping RACH occasions corresponds to a set of resources that at least partially overlaps in time with resources corresponding to one or more RACH occasions of the first set; and indicating to the device a maximum number of simultaneously active SSB beams supported by the access node.

[0042] A tenth aspect provides an apparatus, the apparatus having at least one processor and at least one memory having computer-readable code stored thereon which when executed controls the at least one processor to perform a method comprising: indicating to a device a mapping between a first set of random access channel occasions, RACH occasions, and one or more synchronisation signal block, SSB, indices, the one or more SSB indices being associated with one or more respective SSB beams, and each RACH occasion of the first set corresponding to a set of resources for transmitting random access messages; indicating to the device a mapping between a second set of RACH occasions and the one or more SSB indices, each RACH occasion of the second set corresponding to a set of resources for transmitting random access messages, wherein the second set of RACH occasions comprises overlapping RACH occasions, wherein each of the overlapping RACH occasions corresponds to a set of resources that at least partially overlaps in time with resources corresponding to one or more RACH occasions of the first set; and indicating to the device a maximum number of simultaneously active SSB beams supported by the access node.

[0043] An eleventh aspect provides a device comprising: means for obtaining a mapping between a first set of random access channel occasions, RACH occasions, and one or more synchronisation signal block, SSB, indices, the one or more SSB indices being associated with one or more respective SSB beams, and each RACH occasion of the first set corresponding to a set of resources for transmitting random access messages; means for obtaining a mapping between a second set of RACH occasions and the one or more SSB indices, each RACH occasion of the second set corresponding to a set of resources for transmitting random access messages, wherein the second set of RACH occasions comprises overlapping RACH occasions, wherein each of the overlapping RACH occasions corresponds to a set of resources that at least partially overlaps in time with resources corresponding to one or more RACH occasions of the first set; means for obtaining an indication of one or more low-priority SSB indices; and means for, based at least in part on the obtained indication of one or more low-priority SSBs, deprioritising at least one overlapping RACH occasion of the second set of RACH occasions based at least in part on the RACH occasion being an overlapping RACH occasion and being mapped to an SSB index of the one or more low-priority SSB indices.

[0044] In some example embodiments, the device further comprises means for transmitting a random access message on the set of resources corresponding to at least one of the RACH occasions that is not deprioritised.

[0045] In some example embodiments, the means for deprioritising at least one overlapping RACH occasion of the second set of RACH occasions are configured to deprioritise a RACH occasion of the second set of RACH occasions based on the RACH occasion being an overlapping and low-priority RACH occasion.

[0046] In some example embodiments, the device further comprises: means for obtaining an indication of a maximum number of simultaneously active SSB beams supported by an access node; and means for determining that the RACH occasions of the first and second set that correspond to sets of resources occupying a particular time or time period are mapped to a number of different SSB indices that exceeds the indicated maximum number of simultaneously active SSB beams supported by the access node, wherein the means for deprioritising at least one overlapping RACH occasion of the second set of RACH occasions are configured to perform the deprioritising responsive to making said determination, and deprioritise one or more overlapping RACH occasions of the second set of RACH occasions mapped to SSB indices selected from the low-priority SSB indices such that the RACH occasions of the first and second set that are not deprioritised, and that correspond to sets of resources occupying the particular time or time period, shall not be mapped to a number of different SSB indices that exceed the determined maximum number of simultaneously active SSB beams supported by the access node.

[0047] In some example embodiments, the means for obtaining an indication of a maximum number of simultaneously active beams supported by the access node are configured to receive from the access node a message comprising an explicit indication of the maximum number of simultaneously active beams supported by the access node.

[0048] In some example embodiments, deprioritising overlapping RACH occasions comprises determining a number of SSB indices mapped to RACH occasions of the first set of RACH occasions corresponding to resources at least partially occupying the particular time or time period.

[0049] In some example embodiments, deprioritising overlapping RACH occasions comprises deprioritising RACH occasions of the second set of RACH occasions until the total number of SSB indices mapped to RACH occasions of the first and second sets of RACH occasions that correspond to resources at least partially occupying the particular time or time period does not exceed the determined maximum number of simultaneously active beams supported by the access node.

[0050] In some example embodiments, deprioritising RACH occasions of the second set of RACH occasions that are mapped to low-priority SSBs is performed in ascending order of SSB index mapped to each RACH occasion corresponding to resources occupying the period of overlap.

[0051] In some example embodiments, deprioritising RACH occasions of the second set of RACH occasions that are mapped to low-priority SSBs is performed in descending order of SSB index mapped to each RACH occasion corresponding to resources occupying the period of overlap.

[0052] In some example embodiments, the device further comprises means for reprioritising deprioritised RACH occasions of the second set of RACH occasions, wherein reprioritising a deprioritised RACH occasion comprises: selecting an SSB index mapped to a RACH occasion of the first and second set that is not deprioritised and that corresponds to a set of resources that overlaps in time with resources corresponding to the deprioritised RACH occasion; remapping the deprioritised RACH occasion to the selected SSB index; and reprioritising the remapped RACH occasion.

[0053] In some example embodiments, the means for reprioritising are configured to select the SSB index based at least in part on the SSB index not being a low-priority SSB index.

[0054] In some example embodiments, for each RACH occasion of the second set of RACH occasions, at least a portion of the set of resources corresponding to that RACH occasion are in a sub-band full duplex time slot.

[0055] In some example embodiments, for each RACH occasion of the first set of RACH occasions, the set of resources corresponding to that RACH occasion are within one or more uplink time slots.

[0056] In some example embodiments, each overlapping RACH occasion of the second set of RACH occasions corresponds to a set of resources comprising resources in an uplink time slot and resources in a sub-band full duplex time slot, wherein at least a portion of the resources in an uplink time slot overlap with resources corresponding to one or more RACH occasions of the first set of RACH occasions.

[0057] A twelfth aspect provides a method comprising: obtaining a mapping between a first set of random access channel occasions, RACH occasions, and one or more synchronisation signal block, SSB, indices, the one or more SSB indices being associated with one or more respective SSB beams, and each RACH occasion of the first set corresponding to a set of resources for transmitting random access messages; obtaining a mapping between a second set of RACH occasions and the one or more SSB indices, each RACH occasion of the second set corresponding to a set of resources for transmitting random access messages, wherein the second set of RACH occasions comprises overlapping RACH occasions, wherein each of the overlapping RACH occasions corresponds to a set of resources that at least partially overlaps in time with resources corresponding to one or more RACH occasions of the first set; obtaining an indication of one or more low-priority SSB indices; and based at least in part on the obtained indication of one or more low- priority SSBs, deprioritising at least one overlapping RACH occasion of the second set of RACH occasions based at least in part on the RACH occasion being an overlapping RACH occasion and being mapped to an SSB index of the one or more low-priority SSB indices.

[0058] In some example embodiments, the method further comprises transmitting a random access message on the set of resources corresponding to at least one of the RACH occasions that is not deprioritised.

[0059] In some example embodiments, deprioritising at least one overlapping RACH occasion of the second set of RACH occasions comprises deprioritising a RACH occasion of the second set of RACH occasions based on the RACH occasion being an overlapping and low-priority RACH occasion.

[0060] In some example embodiments, the method further comprises: obtaining an indication of a maximum number of simultaneously active SSB beams supported by an access node; and determining that the RACH occasions of the first and second set that correspond to sets of resources occupying a particular time or time period are mapped to a number of different SSB indices that exceeds the indicated maximum number of simultaneously active SSB beams supported by the access node, wherein deprioritising at least one overlapping RACH occasion of the second set of RACH occasions comprises performing the deprioritising responsive to making said determination, and deprioritising one or more overlapping RACH occasions of the second set of RACH occasions mapped to SSB indices selected from the low-priority SSB indices such that the RACH occasions of the first and second set that are not deprioritised, and that correspond to sets of resources occupying the particular time or time period, shall not be mapped to a number of different SSB indices that exceed the determined maximum number of simultaneously active SSB beams supported by the access node.

[0061] In some example embodiments, obtaining an indication of a maximum number of simultaneously active beams supported by the access node comprises receiving from the access node a message comprising an explicit indication of the maximum number of simultaneously active beams supported by the access node.

[0062] In some example embodiments, deprioritising overlapping RACH occasions comprises determining a number of SSB indices mapped to RACH occasions of the first set of RACH occasions corresponding to resources at least partially occupying the particular time or time period.

[0063] In some example embodiments, deprioritising overlapping RACH occasions comprises determining a number of SSB indices mapped to RACH occasions of the second set of RACH occasions corresponding to resources at least partially occupying the particular time or time period.

[0064] In some example embodiments, deprioritising overlapping RACH occasions comprises deprioritising RACH occasions of the second set of RACH occasions until the total number of SSB indices mapped to RACH occasions of the first and second sets of RACH occasions that correspond to resources at least partially occupying the particular time or time period does not exceed the determined maximum number of simultaneously active beams supported by the access node.

[0065] In some example embodiments, deprioritising RACH occasions of the second set of RACH occasions that are mapped to low-priority SSBs is performed in ascending order of SSB index mapped to each RACH occasion corresponding to resources occupying the period of overlap.

[0066] In some example embodiments, deprioritising RACH occasions of the second set of RACH occasions that are mapped to low-priority SSBs is performed in descending order of SSB index mapped to each RACH occasion corresponding to resources occupying the period of overlap.

[0067] In some example embodiments, the method further comprises reprioritising deprioritised RACH occasions of the second set of RACH occasions, wherein reprioritising a deprioritised RACH occasion comprises: selecting an SSB index mapped to a RACH occasion of the first and second set that is not deprioritised and that corresponds to a set of resources that overlaps in time with resources corresponding to the deprioritised RACH occasion; remapping the deprioritised RACH occasion to the selected SSB index; and reprioritising the remapped RACH occasion.

[0068] In some example embodiments, the reprioritising comprises selecting the SSB index based at least in part on the SSB index not being a low-priority SSB index.

[0069] In some example embodiments, for each RACH occasion of the second set of RACH occasions, at least a portion of the set of resources corresponding to that RACH occasion are in a sub-band full duplex time slot.

[0070] In some example embodiments, for each RACH occasion of the first set of RACH occasions, the set of resources corresponding to that RACH occasion are within one or more uplink time slots.

[0071] In some example embodiments, each overlapping RACH occasion of the second set of RACH occasions corresponds to a set of resources comprising resources in an uplink time slot and resources in a sub-band full duplex time slot, wherein at least a portion of the resources in an uplink time slot overlap with resources corresponding to one or more RACH occasions of the first set of RACH occasions.

[0072] A thirteenth aspect provides a computer program comprising a set of instructions which, when executed on an apparatus, is configured to cause the apparatus to carry out a method comprising: obtaining a mapping between a first set of random access channel occasions, RACH occasions, and one or more synchronisation signal block, SSB, indices, the one or more SSB indices being associated with one or more respective SSB beams, and each RACH occasion of the first set corresponding to a set of resources for transmitting random access messages; obtaining a mapping between a second set of RACH occasions and the one or more SSB indices, each RACH occasion of the second set corresponding to a set of resources for transmitting random access messages, wherein the second set of RACH occasions comprises overlapping RACH occasions, wherein each of the overlapping RACH occasions corresponds to a set of resources that at least partially overlaps in time with resources corresponding to one or more RACH occasions of the first set; obtaining an indication of one or more low-priority SSB indices; and based at least in part on the obtained indication of one or more low-priority SSBs, deprioritising at least one overlapping RACH occasion of the second set of RACH occasions based at least in part on the RACH occasion being an overlapping RACH occasion and being mapped to an SSB index of the one or more low-priority SSB indices.

[0073] In some example embodiments, the thirteenth aspect may include any other feature mentioned with respect to the method of the twelfth aspect.

[0074] A fourteenth aspect provides a non-transitory computer-readable medium having stored thereon computer-readable code, which, when executed by at least one processor, causes the at least one processor to perform a method comprising: obtaining a mapping between a first set of random access channel occasions, RACH occasions, and one or more synchronisation signal block, SSB, indices, the one or more SSB indices being associated with one or more respective SSB beams, and each RACH occasion of the first set corresponding to a set of resources for transmitting random access messages; obtaining a mapping between a second set of RACH occasions and the one or more SSB indices, each RACH occasion of the second set corresponding to a set of resources for transmitting random access messages, wherein the second set of RACH occasions comprises overlapping RACH occasions, wherein each of the overlapping RACH occasions corresponds to a set of resources that at least partially overlaps in time with resources corresponding to one or more RACH occasions of the first set; obtaining an indication of one or more low- priority SSB indices; and based at least in part on the obtained indication of one or more low-priority SSBs, deprioritising at least one overlapping RACH occasion of the second set of RACH occasions based at least in part on the RACH occasion being an overlapping RACH occasion and being mapped to an SSB index of the one or more low-priority SSB indices.

[0075] The fourteenth aspect may include any other feature mentioned with respect to the method of the twelfth aspect.

[0076] A fifteenth aspect provides an apparatus, the apparatus having at least one processor and at least one memory having computer-readable code stored thereon which when executed controls the at least one processor to perform a method comprising : obtaining a mapping between a first set of random access channel occasions, RACH occasions, and one or more synchronisation signal block, SSB, indices, the one or more SSB indices being associated with one or more respective SSB beams, and each RACH occasion of the first set corresponding to a set of resources for transmitting random access messages; obtaining a mapping between a second set of RACH occasions and the one or more SSB indices, each RACH occasion of the second set corresponding to a set of resources for transmitting random access messages, wherein the second set of RACH occasions comprises overlapping RACH occasions, wherein each of the overlapping RACH occasions corresponds to a set of resources that at least partially overlaps in time with resources corresponding to one or more RACH occasions of the first set; obtaining an indication of one or more low- priority SSB indices; and based at least in part on the obtained indication of one or more low-priority SSBs, deprioritising at least one overlapping RACH occasion of the second set of RACH occasions based at least in part on the RACH occasion being an overlapping RACH occasion and being mapped to an SSB index of the one or more low-priority SSB indices.

[0077] The fifteenth aspect may include any other feature mentioned with respect to the method of the twelfth aspect.

[0078] A sixteenth aspect provides an apparatus comprising: means for indicating to a device a mapping between a first set of random access channel occasions, RACH occasions, and one or more synchronisation signal block, SSB, indices, the one or more SSB indices being associated with one or more respective SSB beams, and each RACH occasion of the first set corresponding to a set of resources for transmitting random access messages; means for indicating to the device a mapping between a second set of RACH occasions and the one or more SSB indices, each RACH occasion of the second set corresponding to a set of resources for transmitting random access messages, wherein the second set of RACH occasions comprises overlapping RACH occasions, wherein each of the overlapping RACH occasions corresponds to a set of resources that at least partially overlaps in time with resources corresponding to one or more RACH occasions of the first set; and means for indicating to the device one or more low-priority SSB indices.

[0079] A seventeenth aspect provides a method comprising: indicating to a device a mapping between a first set of random access channel occasions, RACH occasions, and one or more synchronisation signal block, SSB, indices, the one or more SSB indices being associated with one or more respective SSB beams, and each RACH occasion of the first set corresponding to a set of resources for transmitting random access messages; indicating to the device a mapping between a second set of RACH occasions and the one or more SSB indices, each RACH occasion of the second set corresponding to a set of resources for transmitting random access messages, wherein the second set of RACH occasions comprises overlapping RACH occasions, wherein each of the overlapping RACH occasions corresponds to a set of resources that at least partially overlaps in time with resources corresponding to one or more RACH occasions of the first set; and indicating to the device one or more low-priority SSB indices.

[0080] An eighteenth aspect provides a computer program comprising a set of instructions which, when executed on an apparatus, is configured to cause the apparatus to carry out a method comprising: indicating to a device a mapping between a first set of random access channel occasions, RACH occasions, and one or more synchronisation signal block, SSB, indices, the one or more SSB indices being associated with one or more respective SSB beams, and each RACH occasion of the first set corresponding to a set of resources for transmitting random access messages; indicating to the device a mapping between a second set of RACH occasions and the one or more SSB indices, each RACH occasion of the second set corresponding to a set of resources for transmitting random access messages, wherein the second set of RACH occasions comprises overlapping RACH occasions, wherein each of the overlapping RACH occasions corresponds to a set of resources that at least partially overlaps in time with resources corresponding to one or more RACH occasions of the first set; and indicating to the device one or more low-priority SSB indices.

[0081] A nineteenth aspect provides a non-transitory computer-readable medium having stored thereon computer-readable code, which, when executed by at least one processor, causes the at least one processor to perform a method comprising: indicating to a device a mapping between a first set of random access channel occasions, RACH occasions, and one or more synchronisation signal block, SSB, indices, the one or more SSB indices being associated with one or more respective SSB beams, and each RACH occasion of the first set corresponding to a set of resources for transmitting random access messages; indicating to the device a mapping between a second set of RACH occasions and the one or more SSB indices, each RACH occasion of the second set corresponding to a set of resources for transmitting random access messages, wherein the second set of RACH occasions comprises overlapping RACH occasions, wherein each of the overlapping RACH occasions corresponds to a set of resources that at least partially overlaps in time with resources corresponding to one or more RACH occasions of the first set; and indicating to the device one or more low-priority SSB indices.

[0082] A twentieth aspect provides an apparatus, the apparatus having at least one processor and at least one memory having computer-readable code stored thereon which when executed controls the at least one processor to perform a method comprising: indicating to a device a mapping between a first set of random access channel occasions, RACH occasions, and one or more synchronisation signal block, SSB, indices, the one or more SSB indices being associated with one or more respective SSB beams, and each RACH occasion of the first set corresponding to a set of resources for transmitting random access messages; indicating to the device a mapping between a second set of RACH occasions and the one or more SSB indices, each RACH occasion of the second set corresponding to a set of resources for transmitting random access messages, wherein the second set of RACH occasions comprises overlapping RACH occasions, wherein each of the overlapping RACH occasions corresponds to a set of resources that at least partially overlaps in time with resources corresponding to one or more RACH occasions of the first set; and indicating to the device one or more low-priority SSB indices. Brief Description of the Drawings

[0083] Example embodiments will now be described by way of non-limiting example, with reference to the accompanying drawings, in which:

[0084] Fig. 1 is a flow diagram illustrating a message flow sequence of the 4-step random access channel, RACH, procedure;

[0085] Fig. 2 is a schematic diagram showing a user equipment, UE, and an antenna panel;

[0086] Fig. 3 is a diagram illustrating an example mapping of, synchronisation signal blocks, SSBs, to RACH occasions, ROs, in one frame;

[0087] Fig. 4 is a schematic diagram of a resource grid comprising subband non-overlapping full duplex, SBFD, slots and non-SBFD slots;

[0088] Fig. 5 is a diagram of an example mapping that maps uplink, UL, and SBFD ROs to SSBs using a single RACH configuration;

[0089] Fig. 6 is a diagram of an example mapping that maps UL and SBFD ROs to SSBs using two separate RACH configurations;

[0090] Fig. 7 is a diagram of an example mapping that uses separate configurations to map legacy ROs and SBFD ROs to SSBs;

[0091] Figs. 8 - 10 are a flow diagrams showing example methods;

[0092] Figs. 11 - 13 are diagrams of an example mapping;

[0093] Figs. 14 - 17 are flow diagrams showing example methods;

[0094] Fig. 18 is a block diagram of components of a system in accordance with an example embodiment; and

[0095] Fig. 19 shows an example of tangible media for storing computer-readable code which when run by a computer may perform methods according to example embodiments described above.

[0096] Detailed Description

[0097] The following embodiments are exemplary. Although the specification may refer to "an", "one", or "some" embodiment(s) in several locations of the text, this does not necessarily mean that each reference is made to the same embodiment(s), or that a particular feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments. Further, when a particular feature, structure, or characteristic is described in connection of an embodiment, it is within the knowledge of one skilled in the art to apply such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. It shall be understood that although the terms "first," "second" and the like may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another.

[0098] For the purposes of the present disclosure, the phrases "at least one of A or B", "at least one of A and B", and "A and / or B" means (A), (B), or (A and B). For the purposes of the present disclosure, the phrase "A, B, and / or C" means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B, and C).

[0099] Embodiments described may be implemented in a communication network, such as any of the following radio access technologies (RATs): Worldwide Interoperability for Microwave Access (WiMAX), Global System for Mobile communications (GSM, 2G), GSM EDGE radio access Network (GERAN), General Packet Radio Service (GRPS), Universal Mobile Telecommunication System (UMTS, 3G) based on basic wideband-code division multiple access (W-CDMA), high-speed packet access (HSPA), Long Term Evolution (LTE), LTE- Advanced, and enhanced LTE (eLTE), 5G (also called NR), or any future RAT such as 6G. Moreover, communication within the communication network may utilize any proper wireless communication technology, comprising but not limited to: Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Frequency Division Duplex (FDD), Time Division Duplex (TDD), Multiple-Input Multiple-Output (MIMO), Orthogonal Frequency Division Multiple (OFDM), and / or Discrete Fourier Transform spread OFDM (DFT-s-OFDM).

[0100] As used herein, the term "network device" or "network node" refers to a node in a communication network via which user equipment may access the network and / or which is capable of controlling radio communication and managing radio resources within a cell. The network node or network device may be referred to as a base station (BS), an access point (AP) or an access node. The network device may be, depending on the applied technology, for example, a node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), an NR NB (also referred to as a gNB), a Remote Radio Unit (RRU), a radio head (RH), a remote radio head (RRH), a relay, an Integrated Access and Backhaul (IAB) node, a low power node, a non-terrestrial network (NTN) or non-ground network device such as a satellite network device, a low earth orbit (LEO) satellite and a geosynchronous earth orbit (GEO) satellite, or an aircraft network device.

[0101] Moreover, in connection of split radio access network (RAN), the network device may refer to a centralised unit (CU) of a base station and / or a distributed unit (DU) of a base station. An interface between CU and DU may be referred to as an Fl interface in NR. In the split RAN architecture, node operations may be carried out, at least partly, in the centra l / centra I ized unit, CU, (e.g. server, host or node) operationally coupled to the DU, (e.g. a radio head / node). One CU may control one or more DUs, acting at least as transmit / receive (Tx / Rx) nodes. In some embodiments, the DUs may comprise e.g. a radio link control (RLC), medium access control (MAC) layer and a physical (PHY) layer, whereas the CU may comprise the layers above RLC layer, such as a packet data convergence protocol (PDCP) layer, a radio resource control (RRC) and an internet protocol (IP) layers. Other functional splits are possible too. In practice, any processing task may be performed in either the CU or the DU and the boundary where the responsibility is shifted between the CU and the DU may depend on the applied implementation.

[0102] The term "terminal device" refers to any end device that may be capable of wireless communication. By way of example, a terminal device may be referred to as a communication device, user equipment (UE), a Subscriber Station (SS), or a Mobile Station (MS). The terminal device may include a mobile phone, a cellular phone, a smart phone, voice over IP (VoIP) phones, wireless local loop phones a tablet, a wearable terminal device, a personal digital assistant (PDA), portable computers, desktop computer, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback appliances, vehicle-mounted wireless terminal devices, USB dongles, an Internet of Things (loT) device, a watch or other wearable, a head-mounted display (HMD), a vehicle, a drone, a medical device and applications (e.g., remote surgery), an industrial device and applications (e.g., a robot and / or other wireless devices operating in an industrial and / or an automated processing chain contexts), a consumer electronics device, a device operating on commercial and / or industrial wireless networks, and the like.

[0103] A term "resource", as used herein, may refer to radio resources in time domain, in frequency domain, in space domain, and / or in code domain. Some examples of resources include e.g. a physical resource block (PRB), a radio frame, a subframe, a time slot, a subband, a frequency region, a sub-carrier, a beam, etc. The term "transmission" and / or "reception" may refer to wirelessly transmitting and / or receiving via a wireless propagation channel on radio resources.

[0104] RACH procedure and SSB to RO mapping

[0105] Aspects of this disclosure relate to random access procedures for radio access networks. In the 5G NR specification, two contention based random access (CBRA) procedures are supported, namely 4-step RACH (Rel-15) and 2-step RACH (Rel-16) and one contention- free random-access procedure (CFRA). A step in all these procedures is the transmission of a suitable message by the user equipment (UE) to the network (NW) (the nature of the message changes depending on which procedure is executed, but the first action is taken by the UE).

[0106] Aspects of this disclosure are applicable to all three random-access procedures, but this disclosure will mostly refer to the 4-step RACH procedure, given that it has larger relevance in practical deployments and it is simpler and more suitable for illustrative purposes.

[0107] Fig. 1 is a flow diagram illustrating a message flow sequence 100 of the 4-step RACH procedure. In this diagram, the procedure takes place between UE 10 and gNodeB (gNB) 20.

[0108] The procedure starts at step 110 (Msgl / PRACH), at which UE 10 sends a specific preamble to gNB 20 via a physical random-access channel (PRACH) using a specific resource called RACH occasion (RO), mapped to one or more SSB beams according to a pattern / configuration.

[0109] At step 120, gNB 20 replies with a random-access response (RAR) message (Msg2), which includes the detected preamble ID, the time-advance command, an identifier (TC-RNTI), and uplink (UL) grant for the transmission of Msg3 on a physical uplink shared channel (PUSCH).

[0110] At step 130 (Msg3 / RRC request), UE 10 responds to Msg2 over the scheduled PUSCH with an ID for contention resolution.

[0111] At step 140 (Msg4 / RRC setup), gNB 20 transmits the contention resolution message with the contention-resolution ID.

[0112] Upon reception of Msg4, the UE sends an acknowledgement (ACK) on a physical uplink control channel (PUCCH) if its contention-resolution ID is carried by Msg4. This completes the 4-step RACH.

[0113] Prior to step 110, there is also a preliminary step of receiving the synchronization signal block (SSB) transmitted by the network (i.e., downlink (DL) beam sweeping), which is not formally part of the RACH procedure. As a result of this preliminary step, the UE selects the index of the preferred SSB beam (e.g., based on a signal strength associated with the SSB beam) and decodes the associated physical broadcast channel (PBCH) to obtain the master information block (MIB), system information block (SIB) and so on. This index is also used by UE 10 to identify a suitable RO for the preamble transmission (Msgl). UE 10 uses a SSB-to-RO mapping, which in this example is conveyed by a SIB (SIB1), to identify an RO for the preamble transmission. gNB 20 may be configured to perform beamforming in a number of directions (e.g., corresponding to the number of different SSB indices), but gNB 20 may only be capable of having a smaller number of beams "active" simultaneously. The SSB-to-RO mapping may indicate to the UE that a beam corresponding to a particular index will be active when using particular a particular RO, and that an antenna will therefore be configured to receive the preamble on the selected beam.

[0114] 2-step RACH is similar to 4-step RACH as presented above, but in 2-step RACH Msgl and Msg3 are effectively combined in "MsgA" and sent out without waiting for feedback (which would be part of Msg2 in the 4-step RACH procedure). Similarly, in 2-step RACH the gNB combines Msg2 and Msg4 into "MsgB". It is straightforward to apply the solutions disclosed herein for Msgl of 4-step RACH, to the preamble / Msgl part of MsgA of 2-step RACH.

[0115] In the RACH procedure, the mapping of SSB indices (also referred to as the beam indices of the SSBs, or the SSB beams, or simply SSBs) to ROs is used by UE to determine which ROs are associated with the SSB index selected during the preliminary step. The different SSB indices may correspond to different beamforming directions in a cell, so selection of the wrong SSB index may result in failure of the RACH procedure (e.g., because the gNB is not configured to receive a RACH transmission on the selected RO on the beam used by the UE / from the direction of the UE).

[0116] Fig. 2 is a schematic diagram showing UE 10 and antenna panel 30 of gNB 20. Antenna panel 30 is configured to beamform in two different directions, referred to as SSB 32 and SSB 33 and corresponding to two different SSB indices. UE 10 may determine at the preliminary stage that SSB 32 is preferred (e.g., because SSB 32 is associated with a stronger signal).

[0117] SSB 32 may be mapped to a first RO, corresponding to particular set of frequency and time resources, such that a UE transmitting a RACH message using these frequency and time resources can expect gNB 20 to be configured to receive the RACH transmission on beam SSB 32. However, if UE 10 incorrectly maps SSB 32 to a different RO (in disagreement with the gNB), antenna panel 30 may instead be configured to receive a RACH transmission using those frequency and time resources on a different beam, SSB 33, and the RACH procedure may fail. To allow UE 10 to correctly map SSBs to ROs, to improve the reliability of the RACH procedure, parameters defining the mapping between SSBs and ROs may be defined. These parameters (along with the ROs themselves) may be communicated to the UE in a SIB (i.e., in the SSB).

[0118] One parameter ssb-perRACH-OccasionAndCB-PreamblesPerSSB is indicates two pieces of information: (i) the number of SS / PBCH block indexes (or preamble sets) per RO and (ii) the number of contention-based preambles per SS / PBCH block index (or preamble set). A further parameter, msgl-FDM, may specify the number of ROs allocated in the frequency domain for one time instance.

[0119] For example, in the 4-step RACH, a UE may be provided with a number N of SS / PBCH block indexes associated with one PRACH occasion and a number R of contention-based preambles per SS / PBCH block index per valid PRACH occasion by ssb-perRACH- OccasionAndCB-PreamblesPerSSB. Once this information is available to a UE, the UE may map the SSB indexes to the time-frequency grid of ROs in increasing order of frequency resource indices, time resource indices of the ROs within a PRACH slots, and the PRACH slots, sequentially. In this disclosure, we focus on the information related to the number of SSBs per ROs, therefore we refer to ssb-perRACH-OccasionAndCB-PreamblesPerSSB as ssb-perRACH-Occasion for the sake of brevity.

[0120] Fig. 3 is a diagram illustrating an example mapping of SSBs to ROs in one frame, designated by the reference numeral 50. Frame 50 has a DDDSU slot structure. In this example Msgl-FDM = 2 and ssb-perRACH-Occasion is 1 / 2. Based on the configuration, two ROs are multiplexed in the frequency domain (as Msgl-FDM = 2, so there are two frequency indices DRA) and SSB indices are mapped to two ROs in the sequence before the next SSB index is mapped (as ssb-perRACH-Occasion = 1 / 2) in a frequency-first and time- second manner, until all SSB indices are mapped. In this example the total number of SSBs is 4.

[0121] In this example, it is assumed that the ROs that overlap with DL symbols are invalid (i.e., ROs 4-7). The mapping for ROs 4 - 7 is therefore shown to illustrate the mapping rules, but not would not be made in practice under this assumption.

[0122] Subband full duplex

[0123] 3GPP 5G NR currently supports two duplexing modes: frequency division duplexing (FDD) for paired (frequency) bands and time division duplexing (TDD) for unpaired bands. For both of these duplexing modes, uplink and downlink phases are separated in the time domain. This may create unnecessary latency, possibly reduce coverage and capacity depending on the considered layout. In TDD deployments, the situation is further exacerbated by the fact that the scheduling offers lower dynamism, i.e., the slot structure is fixed and does not change very often in practice. This may result in rather limited time duration for the uplink in TDD.

[0124] There is therefore an interest in enabling a gNB to perform simultaneous DL transmission and UL reception on different physical resource blocks (PRBs) / subbands within an unpaired wideband NR cell. In this disclosure, we refer to this as subband non-overlapping full duplex (SBFD). In other sources, this duplexing scheme may also be referred to as crossdivision duplexing (xDD) scheme or Flexible Duplexing (FDU).

[0125] There may therefore be two slot types for both DL and UL transmissions in a SBFD capable gNB: o SBFD slots, during which the non-overlapping DL subband(s) and UL subband(s) both exist; and o Non-SBFD slots, during which the entire band is used / reserved for either DL or UL (i.e., legacy / full DL / UL slots).

[0126] Fig. 4 is a schematic diagram of a resource grid comprising SBFD slots 90 and non-SBFD slots 80. As can be seen from figure 4, in SBFD slots 90, a guardband 70 may be placed between DL and UL resource blocks (RBs). This provides better isolation between UL and DL transmissions and may reduce the impact of self-interference (due to gNB's own DL transmissions and the gNB's own UL reception) as well as cross-link interference (CLI) between UE to UE links, and gNB to gNB links.

[0127] In this disclosure, we refer to a RO in UL symbol(s) as UL RO and a RO in SBFD symbol(s) as SBFD RO.

[0128] RACH procedure and SBFD symbols

[0129] If a gNB is configured to operate using SBFD slots, it may be advantageous to allow ROs of SBFD slots to be used in the RACH procedure. There may therefore be an interest in making use of ROs in UL sub-band of SBFD symbols (i.e., by considering them to be valid ROs for transmitting a RACH preamble), and these ROs may be referred to as SBFD ROs. ROs in UL symbols are referred to as UL ROs.

[0130] A gNB may be required to support "legacy" UEs that do not transmit in SBFD slots alongside UEs that transmit in non-SBFD UL slots. It may therefore be advantageous for the SSB to RO mapping for UL ROs to be unaffected by an SSB to RO mapping for SBFD ROs.

[0131] Fig. 5 is a diagram of example mapping 200, mapping UL and SBFD ROs to SSBs using a single RACH configuration. This first option for RACH configuration for SBFD-aware UEs reuses the configuration for UL ROs to SBFD ROs. This example considers 4 SSBs, with two ROs that are multiplexed in the frequency domain (msgl-FDM = 2) and one SSB is mapped to one RO (ssb-perRACH-occasion = 1). This example also assumes that 1 RO of every two ROs in the time domain is an SBFD RO (because these ROs are in a UL subband of SBFD symbols). Notably that the SBFD ROs are transparent to legacy UEs and valid for only SBFD-aware UEs. For this first option, SSBs are separately mapped to SBFD ROs and UL ROs.

[0132] Fig. 6 is a diagram of example mapping 300, mapping UL and SBFD ROs to SSBs using two separate RACH configurations. This second option uses two separate RACH configurations, wherein a first configuration is the legacy configuration which configures only legacy UL ROs (these UL ROs are usable by both legacy UEs and SBFD-aware UEs). The second configuration is an additional configuration for configuring SBFD ROs ("additional ROs"). This second option can support long length SBFD ROs, which can cross the SBFD slot to the UL slot. For simplicity we will refer to the long length SBFD RO with: SBFD LL-RO. In mapping 300 the first and the second configurations are configured with 4 SSBs, two ROs are multiplexed in the frequency domain (msgl-FDM = 2) and one SSB is mapped to one RO (ssb-perRACH-occasion = 1). In some cases, if corresponding parameters are configured with the same value in both configurations, those parameters may be configured only in one (e.g., the first) configuration. However, this example illustrates these parameters separately.

[0133] When using the second option (separate configurations), it may be desirable to consider ROs of the second configuration that are configured within (e.g., entirely within) non-SBFD symbols invalid. To ensure that non-SBFD UL resources are used effectively, it may be desirable to ensure that RACH occasions that do not rely on any SBFD symbols are not unusable by non-SBFD enabled UEs. The second configuration may be invisible to or ignored by non SBFD-aware UEs, so invalidating ROs of the second configuration that are configured within non-SBFD symbols may prevent non-SBFD UL resources being unnecessarily reserved for SBFD enabled UEs only.

[0134] The legacy SSB-to-RO mapping procedure allows SSBs to be mapped to ROs based on a relatively small number of parameters. It may therefore be desirable to apply the legacy SSB-to-RO mapping rules (e.g., assigning SSBs to ROs in an RO frequency index, RO time index order, etc.) to the additional ROs with minimal or limited modifications, even when using a different configuration for the additional ROs (e.g., when using a different ssb- perRACH-occasion, msgl-FDM, etc. for the additional ROs).

[0135] While ROs of the second configuration that are entirely within may be considered invalid It may still be possible for legacy ROs to overlap with additional ROs.

[0136] For example, additional ROs that extend from an SBFD symbol into a non-SBFD symbol may not be entirely within a non-SBFD slot, so may remain valid, but may overlap with a legacy RO in the non-SBFD slot. This occurs for LL-ROs which span over SBFD and non- SBFD symbols and partly overlap with the legacy ROs over the non-SBFD symbols. Other scenarios in which legacy ROs partly or fully overlap (in the time domain) with SBFD ROs may arise. For example, in flexible symbols, additional ROs (which are not necessarily in long length, or long, format) may overlap with legacy ROS.

[0137] Overlapping ROs and simultaneous active SSBs

[0138] Fig. 7 is a diagram of an example mapping 400 of SSBs, using separate configurations to map legacy ROs and SBFD ROs to SSBs. Notably, and unlike in the examples of previous figures, in mapping 400 additional ROs partly overlap in time with legacy ROs. According to this mapping, at (at least) one time, SSB#0, SSB#1, SSB#2 and SSB#3 are all enabled. This is in contrast to legacy behaviour, in which only 2 SSBs (SSB#0 and SSB#1) would have been enabled at any one time.

[0139] A network (or a particular access node) might not support more than a specific number of beams simultaneously. This capability issue may arise more frequently for frequency range FR2, as the network may employ analogue (rather than digital) beamforming in this frequency range, and accordingly, only a given number of beams (N) can be supported at a time. For example, when a gNB configures all antenna elements in the panel for analog beamforming N = 1 beam, or when a gNB splits the antenna elements in the panel for enabling 2 analog beams at a time N = 2 beams, and so on. A different N may be configured for FR1 and FR2, and N for FR1 may be greater than N for FR2.

[0140] It may not be possible to configure antenna elements (into groups of elements that can be beamformed independently) dynamically, and this configuration may be determined at the hardware level. Hence, in some cases only at maximum N active SSBs can be supported simultaneously.

[0141] If SBFD ROs follow the same SBFD-to-RO mapping rule as in the legacy ROs, accounting for this scenario may increase complexity and reduce flexibility at the network, as the network would need to carefully select a combination of configurations to avoid such a scenario. For example, to have exactly the same SSB indices mapped to legacy and SBFD ROs at each overlap, the network may need to configure msgl-FDM to be the same for the first and the second configuration, and configure the number of valid ROs within an association period to be the same for the legacy and SBFD ROs.

[0142] It may therefore be desirable to provide methods for avoiding (or reducing the risk of) a scenario in which SSB-to-RO mapping(s) correspond to a number of active SSBs at a particular time that exceeds network capabilities without modifying, or while minimally modifying mapping rules.

[0143] Network indication of capabilities

[0144] One option discussed in this disclosure is using network-initiated signalling to indicate the maximum number of SSBs that can be active / enabled at a time. The network would indicate that it supports a maximum of N beams to be simultaneously active / enabled. In an embodiment, a unique N is indicated per frequency range, e.g. Ni for FR1 and N2for FR2. For example, we can take "M" to correspond to the total number of SSBs mapped to ROs from the first and second configurations at a certain time instance (i.e. mapped to ROs using a particular time resource or range of time resources). For example, in the case of legacy UL ROs and SBFD ROs overlapping, M may be the sum of the number of different SSB indexes across both types of ROs at the time of overlap or during the period of overlap. The signalling indicating that a maximum of N simultaneously active beams are supported would indicate that N of the M beams can be simultaneously active / enabled (e.g., without exceeding network or access node capabilities).

[0145] Given this information provided by the network, UEs can prioritise which SSBs are enabled at a given set of ROs (i.e. the given set of ROs may be ROs corresponding to a particular time or period of overlap). ROs of the given set of ROs that are mapped to the SSBs that are not enabled could then be deprioritised. After this prioritization, the UE may use (or be expected to use) those ROs that have not been deprioritised to send the RACH preamble. The network shares the same understanding, and the number of SSBs mapped to ROs occupying any one time may therefore be limited based on the capabilities of the network.

[0146] This indication may provide a common understanding between the network and UE about which of the configured ROs can be actually used. For instance, considering mapping 400, if the network indicates N = 2, the UE may only use up to two ROs, e.g. the ROs whose SSB index is either SSB#0 or SSB#1, even if, at the overlapping time instance, the SSB- to-RO mapping indicates that SSB#0, SSB#1, SSB#2 and SSB#3 are in principle active. For ROs with higher SSB indexes (SSB#2 and SSB#3), the UE may determine that these indices are invalid or deprioritized, and the network may expect that the UE won't use them.

[0147] Therefore, by performing this prioritisation based on the indication, even if the SSB-to-RO mapping is unchanged, UEs and the network may have a common understanding regarding the enabled SSBs.

[0148] Fig. 8 is a flow diagram showing example method 500. Method 500 is a method in which a device deprioritises one or more ROs. This may allow a network (or in some examples a specific access node) and the device (which may in some examples be a UE) to have a common understanding of which ROs correspond to SSBs that are enabled (at a particular time).

[0149] At step 510, a device obtains a mapping between a first set of ROs and SSBs / SSB indices. In some examples the first set of ROs are legacy ROs (i.e., derived from a RACH configuration for legacy UL ROs, for use by both legacy UEs and SBFD aware UEs). The first set of ROs and the associated mapping may be derived from indications from the network (e.g., from a broadcast message generally, or an SIB of the SSB). At step 512, the device obtains a mapping between a second set of ROs and the SSBs / SSB indices. In some examples, the second set of ROs are additional ROs (i.e., derived from a RACH configuration for SBFD aware UEs). The second set of ROs and the associated mapping may also be derived from indications from the network (e.g., from a broadcast message generally, or an SIB of the SSB).

[0150] At step 514, the device obtains an indication of a maximum number of simultaneously active SSB beams supported by an access node. In some examples this indication may be configured based on properties of the hardware of the access node, or some other limitation. In some examples, this indication is obtained from the access node (e.g., from a broadcast message, or from the SSB specifically).

[0151] At step 516, the device determines that, at a particular time, or during a particular time period (e.g., a period during which the sets of resources associated with ROs of the first and second set overlap), the ROs of the first and second set that correspond to resources that occupy that time or time period are mapped to a number of different SSB indices that exceeds the indicated maximum number of simultaneously active SSB beams supported by the access node.

[0152] At step 518, in response to making the determination at step 516, and for the set of ROs that corresponds to resources occupying the time or time period under consideration (e.g., occupying all or part of the period of overlap) the device deprioritises one or more of the ROs of the second set so that the remaining ROs (i.e., that are not deprioritised) of the first and second sets are not mapped to a number of different SSB indices that exceeds the determined maximum. The remaining ROs (that are not deprioritised) map to a number of SSBs that does not exceed the network's capabilities, e.g. does not exceed N, so this way the device can select an RO having an SSB index that the network is configured to receive. Using the same information as the device, the network can derive a corresponding mapping and deprioritise corresponding ROs.

[0153] The deprioritising may be limited to the ROs of the second set. By deprioritising ROs of the second set rather than the first, the legacy ROs are unaffected by the new behaviour of the additional ROs, and devices not configured for SBFD may be unaffected.

[0154] While steps 510 - 514 are shown as occurring in a particular order in method 500, it is not essential that this order is followed. Fig. 9 is a flow diagram of example method 600. Method 600 comprises steps of method

[0155] 500 but includes further steps. Method 600 is carried out by a device (such as a UE).

[0156] At step 612, the device receives (e.g., from an access node, such as a gNB) one or more SSBs.

[0157] At step 614, the device selects a preferred SSB (i.e. the index of the preferred SSB). For example, the device may measure the signal strength (e.g. reference signal received power [RSRP]) of the one or more SSBs, and select a preferred SSB having the highest measured signal strength.

[0158] At step 616, the device obtains a mapping between a first set of ROs and a set of SSB indices (including the selected SSB index). The first set of ROs may be legacy ROs. The first set of ROs and the associated mapping may be derived from indications from the network (e.g., from the SSB received at step 612).

[0159] At step 618, the device obtains a mapping between a second set of ROs and a set of SSB indices (including the selected SSB index). The second set of ROs may be additional ROs. The second set of ROs and the associated mapping may also be derived from indications from the network (e.g., from the SSB received at step 612).

[0160] At step 620, the device obtains an indication of a maximum number of simultaneously active SSB beams supported by an access node. In some examples this indication may be configured based on properties of the hardware of the access node, or some other limitation. In some examples, this indication is obtained from the access node (e.g., from an SSB received at step 612). In some examples, the device may infer the maximum number of simultaneously active SSB beams supported by an access node from the number of different SSB indices mapped to ROs of the first set that overlap in the time domain (effectively indicating that only ROs of the second set that are mapped to SSBs that are also mapped to ROs of the first set should not be deprioritised in case of overlap). In some examples, a device may be configured to make this inference in the absence of an explicit indication from the network.

[0161] At step 622, similar to step 516, the device determines that at a particular time (which in some examples corresponds to a determined overlap or period of overlap in the time domain between resources corresponding to the first and second sets of ROs) the ROs of the first and second set that correspond to resources (at least partially) occupying that time or time period are mapped to a number of different SSB indices that exceeds the indicated maximum number of simultaneously active SSB beams supported by the access node.

[0162] At step 624, and in response to making the determination of step 622, for the ROs corresponding to resources occupying the time / period of overlap the device deprioritises one or more ROs of the second set, so that the remaining ROs (i.e., that are not deprioritised) of the first and second sets do not map to a number of different SSBs that is greater than the indicated maximum number of simultaneously active SSB beams. Deprioritisation may be carried out according to a certain scheme, and examples of deprioritisation schemes are described herein. In some examples the deprioritisation is carried out based on the indicated maximum number of simultaneously active SSB beams and a scheme known by the device and the access node by default (e.g., defined in system specifications. In other examples, the scheme to be used or certain parameters defining or indicating said scheme are signalled between the device and the access node (e.g., as part of the RACH configuration) such that both the device and the access node have a common understanding of the deprioritisation scheme.

[0163] Deprioritisation may be performed because the network (or a particular access node) is only capable of supporting a limited number of active beams simultaneously. There may therefore be no issue with using the deprioritised RO (and its associated resources) itself, and issues may instead be caused by using the mapped SSB in combination with the associated time resources. Therefore, in some examples the deprioritised ROs are remapped to different SSBs so that they may be used. The remapping pattern may follow a determined scheme, and some embodiments are described herein. The pattern may be either known by the device and the access node by default, e.g. defined in system specifications, or signalled between the device and the access node such that both the device and the access node have a common understanding of the remapping pattern.

[0164] In this example, at step 626, the deprioritised ROs are remapped. The remapping may use a remapping rule, and / or the remapping may be based on further indications from the network. For example, the deprioritised ROs may all be remapped to the lowest SSB index mapped to the remaining ROs (i.e., that have not been deprioritised) of the group of ROs of the period of overlap. In other examples, the deprioritised ROs may be remapped to the SSBs of the remaining ROs of the group in ascending order of SSB index (e.g., to achieve a more even spread of ROs). The remapping could be performed in descending order, or all deprioritised ROs could be remapped to the highest SSB index of the ROs of the group of remaining ROs. In some examples, the device may use a default remapping rule. In other examples, the network may indicate a remapping rule.

[0165] At step 628 the remapped ROs are made available for the random access. This may be understood as reprioritisation that overrules the deprioritisation.

[0166] Steps 626 and 628 may be omitted in some examples.

[0167] At step 630, the device selects an RO corresponding to the preferred SSB (i.e., from the first or second set of ROs). If remapping has not occurred, or not all ROs have been remapped, then the device may select the RO from the ROs of the first and second sets that are not deprioritised (i.e., that have been reprioritised, or that were never deprioritised).

[0168] At step 632, the device sends a RACH transmission using the selected RO. For example, the device may be a UE sending a RACH preamble at the first step of the two-step or four- step RACH procedure.

[0169] Fig. 10 is a flow diagram of example method 700. Method 700 corresponds to an example of performing the determinations and deprioritisations of steps 516, 518, 622, and 624, so may be performed by the device of methods 600 and 700. An access node may perform a corresponding method to deprioritise corresponding ROs.

[0170] At step 710, RACH occasions of the first and second set that overlap are identified. For example, based on the starting symbol and symbol length (in the time domain) of the resources of ROs of the first and second sets, it can be determined whether an RO of the first set overlaps in the time domain with an RO of the second set. The starting symbol and length may be indicated by the network, for example in the SIB.

[0171] At step 712, once a group of overlapping ROs of the first and second sets have been identified, the SSB indices mapped to the ROs of this group that are part of the first set are determined.

[0172] At step 714, similarly, the indices mapped to ROs of this group that are part of the second set, that are not also mapped to ROs of the first set, are determined.

[0173] At step 716, it is determined that the number of SSB indices mapped to ROs exceeds the indicated supported maximum number simultaneously active beams (e.g., by comparing the total number of indices determined at steps 712 and 714 to the indicated maximum).

[0174] At step 718, in response to making this determination, SSBs determined at step 714 are selected, and ROs of the group identified at step 710 that are mapped to these SSBs are deprioritised. The number of SSBs selected may be equal to the difference between the total number of different SSB indices at step 716 and the indicated maximum. The SSBs may be selected according to different rules. For example, SSBs may be selected (from the SSBs identified at step 714) in ascending or descending order of index. As a result, the remaining ROs of the group that have not been deprioritised may map to a number of SSBs that does not exceed the indicated maximum.

[0175] Steps 710 - 714 may be repeated to identify further groups of overlapping ROs in the RACH configurations. The steps may also be repeated until all groups of overlapping first and second sets of ROs have been identified and remaining (non-deprioritised) ROs for each group do not map to more SSB indices than the maximum.

[0176] Fig. 11 is a diagram illustrating mapping 400 following deprioritisation of an RO (e.g., as part of method 700. The resources of ROs 410 and 412 (of the first set) overlap in the time domain with the resources of ROs 414 and 416 (of the second set). In example method 700 this may be determined at step 710 (e.g., based on the starting symbol and length of the ROs). SSBs #1 and #2 are mapped to ROs 410 and 412, and an additional two SSBs (#2 and #3) are mapped to ROs 414 and 416.

[0177] In this case the indicated supported maximum number simultaneously active beams is three, so the total number of SSBs mapped to ROs 410 - 416 exceeds this maximum by one, and at step 718 RO 416 is deprioritised (i.e., all ROs corresponding to one of the SSBs determined at step 714). In this case, ROs corresponding to SSB#3 have been deprioritised (e.g., because the deprioritisation is performed in descending order of SSB index). In other examples, deprioritisation may be performed in ascending order of SSB index (so SSB#2 may instead be deprioritised).

[0178] Fig. 12 is a diagram illustrating mapping 400 following deprioritisation, remapping, and reprioritisation of an RO. In this case, RO 416 has been remapped to SSB#2, so that the number of SSBs mapped to overlapping ROs does not exceed 3. In this case RO 416 has been remapped to the SSB with the highest index, but other remapping rules may be used (such as remapping in ascending index order from the indices mapped to the overlapping ROs that have not been deprioritised).

[0179] Fig. 13 is a diagram illustrating mapping 400 following another example remapping. In this case, similar to above, RO 416 has been deprioritised. However, instead of remapping RO 416, the mapping of the following ROs (in frequency - time order) carries on from SSB#3 as though RO 416 were never mapped to SSB#3. This example remapping could also be combined with the above example remapping (e.g., by remapping RO 416 to SSB#2 and continuing the mapping from SSB#3).

[0180] The deprioritisation of ROs may additionally or alternatively be based on an indication of SSB priorities.

[0181] Fig. 14 is a flow diagram showing example method 800. Similar to method 500, method 800 is a method in which a device deprioritises one or more ROs. This may allow a network (or in some examples a specific access node) and the device (which may in some examples be a UE) to have a common understanding of which ROs correspond to SSBs that are enabled (at a particular time).

[0182] A device obtains mappings between first and second sets of ROs and SSBs / SSB indices at steps 810 and 812 respectively, in a similar manner to steps 510 and 512 of method 500.

[0183] At step 814, the device obtains an indication of a set of low-priority SSB indices. In some examples, this indication is obtained from the access node (e.g., from a broadcast message, or from the SIB specifically).

[0184] At step 816, the device deprioritises ROs of the second set that overlap in the time domain with ROs of the first set and that are mapped to low-priority SSB indices. In some embodiments this may include deprioritising all ROs that are mapped to low-priority SSB indices in any group of overlapping ROs (e.g., with the group being determined in a similar manner to step 710). By deprioritising ROs mapped to low-priority SSBs, the device can determine ROs corresponding to SSBs that may be active in the case of an overlap. For example, in example mapping 400, the network may indicate that SSB#3 is a low priority SSB, so that the device can deprioritise SSB#3 in the case of overlap, reducing the number of simultaneously mapped SSBs at any one time from 4 to 3. It is not essential that all ROs of the second set mapped to low-priority SSBs are deprioritised in a group of overlapping ROs. For example, the selection of SSBs (mapped to ROs to be deprioritised) may be based only in part on the indication of low-priority SSBs. Fig. 15 is a flow diagram of example method 900. Method 900 comprises steps of method

[0185] 800 but includes further steps. Method 900 is carried out by a device (such as a UE).

[0186] Steps 912 - 918 correspond to steps 612 - 618 of method 600. Steps 920 - 922 correspond to steps 814 and 816 of method 800. Step 922 is in some examples followed by remapping and reprioritising steps 924 and 926. Remapping and reprioritisation steps 924 and 926 may be similar to remapping and reprioritisation steps 626 and 628. Additionally or alternatively, the remapping may remap deprioritised ROs to SSBs that are not indicated as being low-priority.

[0187] Steps 928 and 930 may correspond to steps 630 and 632.

[0188] In some embodiments, an indication of priority may be used in combination with an indication of a maximum number of simultaneous SSB beams to determine which ROs to deprioritise.

[0189] Fig. 16 is a flow diagram of example method 1000. Example method 1000 comprises steps of 1012 - 1020 and 1024 corresponding to steps 612 - 622 of method 600. Example method 1000 also comprises step 1020, corresponding to step 920 of method 900.

[0190] At step 1026, in response to having determined that the indicated maximum number of active beams has been exceeded by some group of overlapping ROs of the first and second set (i.e., one or more ROs of the first set corresponding to resources that overlap in the time domain with resources corresponding to one or more ROs of the second set), the device deprioritises ROs of the second set. This deprioritisation is based on the indicated priority and the indicated maximum number of SSB beams. For example, deprioritised ROs may be mapped to low-priority SSBs, or the first ROs to be deprioritised in a group may be mapped to low-priority SSBs. Based on the indicated maximum number of simultaneous SSB beams, ROs may be deprioritised until the remaining ROs (i.e., that have not been deprioritised) of the group of overlapping ROs is not mapped to a number of SSB indices that exceeds the indicated maximum number of simultaneous SSB beams.

[0191] At step 1028, the deprioritised ROs may optionally be remapped. Similar to step 626, the remapping may follow a remapping rule to remap ROs to SSBs of the group of overlapping ROs that have not been deprioritised. Optionally, the remapping may also be based on the indication of low-priority SSBs. For example, ROs may always be remapped to SSBs that are not low-priority, or ROs may be remapped to SSBs that are low priority only after some or all eligible SSBs (i.e., SSBs mapped to non-deprioritised ROs of the group) that are not low priority have been remapped to ROs.

[0192] Steps 1030 - 1034 correspond to steps 628 - 632 of method 600.

[0193] Fig. 10 is a flow diagram of example method 1100. Method 1100 corresponds to an example of performing the determinations and deprioritisations of steps 1024 and 1026. An access node may perform a corresponding method to deprioritise corresponding ROs.

[0194] Method 1100 corresponds to method 700, except that at step 1118, SSBs that have low priority are preferentially selected so that the ROs mapped thereto will be deprioritised. In some examples, only low-priority SSBs are selected, while in other examples low-priority SSBs are selected first.

[0195] By selecting low-priority SSBs (of the SSBs mapped to a group of overlapping ROs) first, or by only selecting low priority SSBs, ROs mapped to low-priority SSBs will be deprioritised relatively more frequently than ROs mapped to SSBs that are not low priority. Deprioritising an RO mapped to an SSB may effectively reduce the number of ROs that a device (having selected a preferred SSB) may choose from to transmit a RACH message (e.g., a RACH preamble). Preferentially deprioritising ROs mapped to low-priority SSBs may reduce the number of ROs that a device that prefers a low-priority SSB may choose from, while avoiding or reducing a reduction in the number of ROs that a device that prefers a non-low-priority SSB may choose from. Having a larger of number of ROs (mapped to a particular SSB) to choose from may reduce the chance of contention in the RACH procedure, as two devices preferring the same SSB may be less likely to select the same RO.

[0196] In some examples, reducing the chance of contention between devices preferring a first SSB or set of SSBs may be more important than reducing the chance of contention between devices preferring a second SSB or set of SSBs. For example, the first set of SSBs may be preferred by devices more frequently than the second set (e.g., if devices generally, or devices performing the RACH procedure specifically, are less likely to prefer a particular set of beams, for example due to the geography of a cell).

[0197] By selecting indicated low-priority SSBs first, ROs corresponding to SSBs that are selected more regularly by devices are less likely to be deprioritised in cases of overlap, while ROs corresponding to SSBs that are selected less regularly by devices may be preferentially deprioritised in cases of overlap, preserving resources for more heavily used SSBs, and reducing the chance of contention in the RACH procedure.

[0198] In some examples the first set of ROs may be unaffected by the deprioritisation procedure. Further, in some examples all SSBs are mapped to at least one RO of the first set, so even if the overall number of (non-deprioritised) ROs mapped to low-priority SSBs may be reduced by the deprioritisation procedure, at least one RO mapped to each SSB may remain usable by a device.

[0199] For completeness, FIG. 18 is a schematic diagram of components of one or more of the example embodiments described previously, which hereafter are referred to generically as a processing system 1800. The processing system 1800 may, for example, be comprised by the device referred to in the claims below.

[0200] The processing system 1800 may have a processor 1802, a memory 1804 closely coupled to the processor and comprised of a Random Access Memory (RAM) 1814 and a Read Only Memory (ROM) 1812, and, optionally, a user input 1810 and a display 1818. The processing system 1800 may comprise one or more network / apparatus interfaces 1808 for connection to a network / apparatus, e.g., a modem which may be wired or wireless. The network / apparatus interface 1808 may also operate as a connection to other apparatus such as device / apparatus which is not network side apparatus. Thus, direct connection between devices / apparatus without network participation is possible.

[0201] The processor 1802 is connected to each of the other components in order to control operation thereof.

[0202] The memory 1804 may comprise a non-volatile memory, such as a hard disk drive (HDD) or a solid-state drive (SSD). The ROM 1812 of the memory 1804 stores, amongst other things, an operating system 1815 and may store software applications 1816. The RAM 1814 of the memory 1804 is used by the processor 1802 for the temporary storage of data. The operating system 1815 may contain code which, when executed by the processor implements aspects of the methods 500, 600, 700, 800, 900, 1000, and 1100 described above, along with aspects of the message flow sequence 100. Note that in the case of small device / apparatus the memory can be most suitable for small size usage i.e., not always a hard disk drive (HDD) or a solid state drive (SSD) is used. The processor 1802 may take any suitable form. For instance, it may be a microcontroller, a plurality of microcontrollers, a processor, or a plurality of processors.

[0203] The processing system 1800 may be a standalone computer, a server, a console, or a network thereof. The processing system 1800 and needed structural parts may be all inside device / apparatus such as loT device / apparatus i.e., embedded to very small size.

[0204] In some example embodiments, the processing system 1800 may also be associated with external software applications. These may be applications stored on a remote server device / apparatus and may run partly or exclusively on the remote server device / apparatus. These applications may be termed cloud-hosted applications. The processing system 1800 may be in communication with the remote server device / apparatus in order to utilize the software application stored there.

[0205] FIG. 19 shows a tangible media, in the form of a removable memory unit 1910, storing computer-readable code which when run by a computer may perform methods according to example embodiments described above. The removable memory unit 1910 may be a memory stick, e.g., a Universal Serial Bus (USB) memory stick, having internal memory 1930 storing the computer-readable code. The internal memory 1930 may be accessed by a computer system via a connector 1920. Of course, other forms of tangible storage media may be used, as will be readily apparent to those of ordinary skilled in the art. Tangible media can be any device / apparatus capable of storing data / information which data / information can be exchanged between devices / apparatus / network.

[0206] Embodiments of the present invention may be implemented in software, hardware, application logic or a combination of software, hardware and application logic. The software, application logic and / or hardware may reside on memory, or any computer media. In an example embodiment, the application logic, software or an instruction set is maintained on any one of various conventional computer-readable media. In the context of this document, a "memory" or "computer-readable medium" may be any non- transitory media or means that can contain, store, communicate, propagate or transport the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer.

[0207] Reference to, where relevant, "computer-readable medium", "computer program product", "tangibly embodied computer program" etc., or a "processor" or "processing circuitry" etc. should be understood to encompass not only computers having differing architectures such as single / multi-processor architectures and sequencers / parallel architectures, but also specialised circuits such as field programmable gate arrays (FPGA), application specific integrated circuits (ASIC), signal processing devices / apparatus and other devices / apparatus. References to computer program, instructions, code etc. should be understood to express software for a programmable processor firmware such as the programmable content of a hardware device / apparatus as instructions for a processor or configured or configuration settings for a fixed function device / apparatus, gate array, programmable logic device / apparatus, etc.

[0208] If desired, the different functions discussed herein may be performed in a different order and / or concurrently with each other. Furthermore, if desired, one or more of the abovedescribed functions may be optional or may be combined. Similarly, it will also be appreciated that the flow and signalling diagrams of Figures 1, 8 - 10, and 14 - 17 are examples only and that various operations depicted therein may be omitted, reordered and / or combined.

[0209] It will be appreciated that the above-described example embodiments are purely illustrative and are not limiting on the scope of the invention. Other variations and modifications will be apparent to persons skilled in the art upon reading the present specification.

[0210] Moreover, the disclosure of the present application should be understood to include any novel features or any novel combination of features either explicitly or implicitly disclosed herein or any generalization thereof and during the prosecution of the present application or of any application derived therefrom, new claims may be formulated to cover any such features and / or combination of such features.

[0211] Although various aspects of the invention are set out in the independent claims, other aspects of the invention comprise other combinations of features from the described example embodiments and / or the dependent claims with the features of the independent claims, and not solely the combinations explicitly set out in the claims.

[0212] It is also noted herein that while the above describes various examples, these descriptions should not be viewed in a limiting sense. Rather, there are several variations and modifications which may be made without departing from the scope of the present invention as defined in the appended claims. List of abbreviations

[0213] CORESET Control channel resource element

[0214] DL Downlink

[0215] FDRA Frequency Domain Resource Assignment gNB Next generation Node-B

[0216] NR New radio

[0217] PDCCH Physical downlink control channel

[0218] PDSCH Physical downlink shared channel

[0219] PRB Physical resource block

[0220] PUCCH Physical uplink control channel

[0221] PUSCH Physical uplink shared channel

[0222] PRACH Physical random access channel (Msgl)

[0223] RIV Resource indicator value

[0224] RRC Radio resource control

[0225] RO PRACH occasion

[0226] SBFD Sub-band full duplex

[0227] TDD Time division duplex

[0228] TDRA Time Domain Resource Assignment

[0229] TX Transmit

[0230] UE User Equipment

[0231] UL Uplink

[0232] SCS sub carrier spacing

[0233] CLI cross link interference

[0234] PCI physical cell id

[0235] FDU flexible full duplex

[0236] RNTI Radio Network Temporary Identifier

[0237] DCI Downlink control information

Claims

1. 42ClaimsWhat is claimed is:

1. A device comprising: means for obtaining a mapping between a first set of random access channel occasions, RACH occasions, and one or more synchronisation signal block, SSB, indices, the one or more SSB indices being associated with one or more respective SSB beams, and each RACH occasion of the first set corresponding to a set of resources for transmitting random access messages; means for obtaining a mapping between a second set of RACH occasions and the one or more SSB indices, each RACH occasion of the second set corresponding to a set of resources for transmitting random access messages, wherein the second set of RACH occasions comprises overlapping RACH occasions, wherein each of the overlapping RACH occasions corresponds to a set of resources that at least partially overlaps in time with resources corresponding to one or more RACH occasions of the first set; means for obtaining an indication of a maximum number of simultaneously active SSB beams supported by an access node; means for determining that the RACH occasions of the first and second set that correspond to sets of resources occupying a particular time or time period are mapped to a number of different SSB indices that exceeds the indicated maximum number of simultaneously active SSB beams supported by the access node; and means for, responsive to making said determination, deprioritising at least one overlapping RACH occasion of the second set of RACH occasions such that the RACH occasions of the first and second set that are not deprioritised, and that correspond to sets of resources occupying the particular time or time period, shall not be mapped to a number of different SSB indices that exceeds the determined maximum number of simultaneously active SSB beams supported by the access node.

2. The device of claim 1, further comprising means for transmitting a random access message on the set of resources corresponding to at least one of the RACH occasions that is not deprioritised.

3. The device of any preceding claim, wherein the means for obtaining an indication of a maximum number of simultaneously active beams supported by the access node are configured to: determine that the maximum number of simultaneously active beams supported43 by the access node has not been explicitly indicated to the device by the access node; and infer from said determination that the maximum number of simultaneously active beams supported by the access node is the maximum number of different SSB indices mapped to RACH occasions of the first set that correspond to resources occupying a particular time instant.

4. The device of any preceding claim, wherein the means for obtaining an indication of a maximum number of simultaneously active beams supported by the access node are configured to: receive from the access node a message comprising an explicit indication of the maximum number of simultaneously active beams supported by the access node.

5. The device of any preceding claim, wherein deprioritising overlapping RACH occasions comprises determining a number of SSB indices mapped to RACH occasions of the first set of RACH occasions corresponding to resources occupying the particular time or time period.

6. The device of claim 5, wherein deprioritising overlapping RACH occasions comprises determining a number of SSB indices mapped to RACH occasions of the second set of RACH occasions corresponding to resources occupying the particular time or time period.

7. The device of claim 6, wherein deprioritising overlapping RACH occasions comprises deprioritising RACH occasions of the second set of RACH occasions until the total number of SSB indices mapped to RACH occasions of the first and second sets of RACH occasions that correspond to resources occupying the particular time or time period does not exceed the determined maximum number of simultaneously active beams supported by the access node.

8. The device of any preceding claim, wherein deprioritising RACH occasions of the second set of RACH occasions is performed in ascending order of SSB index mapped to each RACH occasion corresponding to resources occupying the period of overlap.

9. The device of any preceding claim 1 to 7, wherein deprioritising RACH occasions of the second set of RACH occasions is performed in descending order of SSB index mapped to each RACH occasion corresponding to resources occupying the period of44 overlap.

10. The device of any preceding claim, further comprising means for reprioritising deprioritised RACH occasions of the second set of RACH occasions, wherein reprioritising a deprioritised RACH occasion comprises: selecting an SSB index mapped to a RACH occasion of the first or second set that is not deprioritised and that corresponds to a set of resources that overlaps in time with resources corresponding to the deprioritised RACH occasion; remapping the deprioritised RACH occasion to the selected SSB index; and reprioritising the remapped RACH occasion.

11. The device of any preceding claim, wherein, for each RACH occasion of the second set of RACH occasions, at least a portion of the set of resources corresponding to that RACH occasion are in a sub-band full duplex time slot.

12. The device of claim 11, wherein, for each RACH occasion of the first set of RACH occasions, the set of resources corresponding to that RACH occasion are within one or more uplink time slots.

13. The device of claim 12, wherein each overlapping RACH occasion of the second set of RACH occasions corresponds to a set of resources comprising resources in an uplink time slot and resources in a sub-band full duplex time slot, wherein at least a portion of the resources in an uplink time slot overlap with resources corresponding to one or more RACH occasions of the first set of RACH occasions.

14. An access node comprising: means for indicating to a device a mapping between a first set of random access channel occasions, RACH occasions, and one or more synchronisation signal block, SSB, indices, the one or more SSB indices being associated with one or more respective SSB beams, and each RACH occasion of the first set corresponding to a set of resources for transmitting random access messages; means for indicating to the device a mapping between a second set of RACH occasions and the one or more SSB indices, each RACH occasion of the second set corresponding to a set of resources for transmitting random access messages, wherein the second set of RACH occasions comprises overlapping RACH occasions, wherein each of the overlapping RACH occasions corresponds to a set of resources that at least partially overlaps in time with resources corresponding to one or more RACH occasionsof the first set; and means for indicating to the device a maximum number of simultaneously active SSB beams supported by the access node.

15. A method comprising: obtaining a mapping between a first set of random access channel occasions, RACH occasions, and one or more synchronisation signal block, SSB, indices, the one or more SSB indices being associated with one or more respective SSB beams, and each RACH occasion of the first set corresponding to a set of resources for transmitting random access messages; obtaining a mapping between a second set of RACH occasions and the one or more SSB indices, each RACH occasion of the second set corresponding to a set of resources for transmitting random access messages, wherein the second set of RACH occasions comprises overlapping RACH occasions, wherein each of the overlapping RACH occasions corresponds to a set of resources that at least partially overlaps in time with resources corresponding to one or more RACH occasions of the first set; obtaining an indication of a maximum number of simultaneously active SSB beams supported by an access node; determining that the RACH occasions of the first and second set that correspond to sets of resources occupying a particular time or time period are mapped to a number of different SSB indices that exceeds the indicated maximum number of simultaneously active SSB beams supported by the access node; and responsive to making said determination, deprioritising at least one overlapping RACH occasion of the second set of RACH occasions such that the RACH occasions of the first and second set that are not deprioritised, and that correspond to sets of resources occupying the particular time or time period, shall not be mapped to a number of different SSB indices that exceed the determined maximum number of simultaneously active SSB beams supported by the access node.

16. The method of claim 15, further comprising transmitting a random access message on the set of resources corresponding to at least one of the RACH occasions that is not deprioritised.

17. The method of claim 15 or 16, wherein said obtaining an indication of a maximum number of simultaneously active beams supported by the access node comprises: determining that the maximum number of simultaneously active beams supported by the access node has not been explicitly indicated to the device by theaccess node; and inferring from said determination that the maximum number of simultaneously active beams supported by the access node is the maximum number of different SSB indices mapped to RACH occasions of the first set that correspond to resources occupying a particular time instant.

18. The method of any preceding claim 15 to 17, wherein deprioritising RACH occasions of the second set of RACH occasions is performed in ascending order of SSB index mapped to each RACH occasion corresponding to resources occupying the period of overlap.

19. The method of any preceding claim 15 to 17, wherein deprioritising RACH occasions of the second set of RACH occasions is performed in descending order of SSB index mapped to each RACH occasion corresponding to resources occupying the period of overlap.

20. The method of any preceding claim, further comprising reprioritising deprioritised RACH occasions of the second set of RACH occasions, wherein said reprioritising a deprioritised RACH occasion comprises: selecting an SSB index mapped to a RACH occasion of the first or second set that is not deprioritised and that corresponds to a set of resources that overlaps in time with resources corresponding to the deprioritised RACH occasion; remapping the deprioritised RACH occasion to the selected SSB index; and reprioritising the remapped RACH occasion.

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