Accessing mobile communication systems

Abstract

A device, method and computer program is described comprising: receiving configuration information from an access node of the mobile communication system, the configuration information including time and frequency allocation of RACH Occasions for the device, wherein first and second symbol types, each having a bandwidth, are available for transmission from the device to the access node, wherein in the said first symbol types the bandwidth is used for either uplink transmission or downlink reception and in the said second symbol types the bandwidth includes uplink and downlink sub-bands that are non- overlapping in the frequency domain; and determining an association period for the device, wherein the association period is sufficient to allow all synchronization signal block indexes to be mapped to at least one RACH occasion, as defined by said configuration information.

Description

[0001] Accessing Mobile Communication Systems

[0002] Field

[0003] Example embodiments may relate to devices (e.g. user equipments, UEs), methods and computer programs for use with a mobile communication system.

[0004] Background

[0005] As part of a resource allocation procedure in some mobile communication systems, synchronization signal blocks indexes (SSB indexes) may be mapped to random access channel (RACH) Occasions. An association period may be defined as a period of time in which all SSB indexes are mapped to at least one RACH Occasion. The association period may be different in different embodiments. The embodiments described herein have been developed in this context.

[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] In a first aspect, this specification describes a device (e.g. a user device, such as a user equipment) of a mobile communication system, the device comprising means for receiving configuration information (e.g. a physical RACH (PRACH) Configuration Index, PCI) from an access node of the mobile communication system, the configuration information including time and frequency allocation of RACH Occasions for the device, wherein first and second symbol types (e.g. first slots and second slots), each having a bandwidth, are available for transmission from the device to the access node, wherein in the said first symbol types (e.g. non-SBFD slots) the bandwidth is used for either uplink transmission or downlink reception and in the said second symbol types (e.g. SBFD slots) the bandwidth includes uplink and downlink sub-bands that are non-overlapping in the frequency domain; and means for determining an association period for the device, wherein the association period is sufficient to allow all synchronization signal block indexes to be mapped to at least one RACH occasion, as defined by said configuration information.

[0009] The device may comprise means for initiating a random-access procedure with said access node using RACH Occasions configured in accordance with the configuration information. The means for initiating said random-access procedure may include transmitting a PRACH preamble (e.g. Msgl) on at least one of RACH Occasions associated with a selected synchronization signal block index.

[0010] The device may further comprise: means for determining a first nominal association period, wherein the first nominal association period is sufficient to allow a first set of synchronisation signal block indexes to be mapped at least once to RACH occasions allocated in the first symbol type, wherein the first set of synchronisation signal block indexes includes all synchronisation signal block indexes; means for determining a second nominal association period (for said second symbol type), wherein the second nominal association period is sufficient to allow a second set of synchronisation signal block indexes to be mapped at least once to additional RACH occasions allocated in the second symbol type, wherein the second set of synchronisation signal block indexes includes all synchronisation signal block indexes relevant to full-duplex transmission (e.g. a subset of all SSBs); and means for selecting one of the first and second nominal association periods as the association period. The device may further comprise selecting the longer of the first and second nominal association periods as the association period. The first and second sets of synchronization signal block indexes may be configured by the access node.

[0011] In some example embodiments, the association period is defined as the period of time in which all synchronization signal block indexes can be mapped at least once to RACH Occasions allocated in the said first symbol type and all synchronization signal block indexes relevant to full-duplex transmission can be mapped at least once to additional RACH Occasions allocated in the said second symbol type.

[0012] The association period may be a positive integer defining an integer multiple of a PRACH configuration period.

[0013] In a second aspect, this specification describes a device (e.g. a user device, such as a user equipment) of a mobile communication system, comprising means for receiving configuration information (e.g. a PRACH Configuration Index, PCI) from an access node of the mobile communication system, the configuration information including time and frequency allocation of RACH Occasions for the device, wherein first and second symbol types (e.g. first slots and second slots), each having a bandwidth, are available for transmission from the device to the access node, wherein in the said first symbol types (e.g. non-SBFD slots) the bandwidth is used for either uplink transmission or downlink reception and in the said second symbol types (e.g. SBFD slots) the bandwidth includes uplink and downlink sub-bands that are non-overlapping in the frequency domain; means for determining an association period (for the said first symbol types), wherein the association period is sufficient to allow all synchronization signal block indexes to be mapped at least once to RACH occasions allocated in the first symbol type; and means for determining a variable K, wherein K association periods are required for mapping all synchronization signal block indexes relevant to full-duplex transmission at least once to additional RACH Occasions allocated in the second symbol type.

[0014] The device may further comprise: means for determining said association period such that, each synchronization signal block is mapped to a RACH Occasion allocated in the first symbol type within the association period; and means for determining said association period and said variable K such that, each synchronization signal block relevant to full- duplex transmission is mapped to an additional RACH Occasion allocated in the second symbol type within K consecutive association periods.

[0015] The device may further comprise initiating a random-access procedure with said access node using RACH Occasions configured in accordance with the configuration information. Initiating said random-access procedure may comprise transmitting a PRACH preamble on RACH Occasions associated with a selected synchronization signal block.

[0016] The device may further comprise means for determining an offset value for synchronization signal block indexes relevant to full-duplex transmission to be mapped with additional RACH occasions allocated in the said second symbol type. In some example embodiments, within a group of K association periods, the offset for the first association period is 0 and the offset for a subsequent association period is an increment of the last beam index mapped to the last RACH Occasion allocated in the second symbol type in the previous association.

[0017] The association period may be a positive integer defining an integer multiple of a PRACH configuration period.

[0018] In a third aspect, this specification describes a method comprising: receiving configuration information (e.g. a PRACH Configuration Index, PCI) from an access node of the mobile communication system, the configuration information including time and frequency allocation of RACH Occasions for the device, wherein first and second symbol types (e.g. first slots and second slots), each having a bandwidth, are available for transmission from the device to the access node, wherein in the said first symbol types (e.g. non-SBFD slots) the bandwidth is used for either uplink transmission or downlink reception and in the said second symbol types (e.g. SBFD slots) the bandwidth includes uplink and downlink subbands that are non-overlapping in the frequency domain; and determining an association period for the device, wherein the association period is sufficient to allow all synchronization signal block indexes to be mapped to at least one RACH occasion, as defined by said configuration information.

[0019] The method may comprise initiating a random-access procedure with said access node using RACH Occasions configured in accordance with the configuration information, for example by transmitting a PRACH preamble (e.g. Msgl) on at least one of RACH Occasions associated with a selected synchronization signal block index.

[0020] The method may further comprise: determining a first nominal association period, wherein the first nominal association period is sufficient to allow a first set of synchronisation signal block indexes to be mapped at least once to RACH occasions allocated in the first symbol type, wherein the first set of synchronisation signal block indexes includes all synchronisation signal block indexes; determining a second nominal association period (for said second type), wherein the second nominal association period is sufficient to allow a second set of synchronisation signal block indexes to be mapped at least once to additional RACH occasions allocated in the second symbol type, wherein the second set of synchronisation signal block indexes includes all synchronisation signal block indexes relevant to full-duplex transmission (e.g. a subset of all SSBs); and selecting one of the first and second nominal association periods as the association period. The device may further comprise selecting the longer of the first and second nominal association periods as the association period. The first and second sets of synchronization signal block indexes may be configured by the access node, configuration period.

[0021] In a fourth aspect, this specification describes a method comprising: receiving configuration information (e.g. a PRACH Configuration Index, PCI) from an access node of the mobile communication system, the configuration information including time and frequency allocation of RACH Occasions for the device, wherein first and second symbol types (e.g. first slots and second slots), each having a bandwidth, are available for transmission from the device to the access node, wherein in the said first symbol types (e.g. non-SBFD slots) the bandwidth is used for either uplink transmission or downlink reception and in the said second symbol types (e.g. SBFD slots) the bandwidth includes uplink and downlink subbands that are non-overlapping in the frequency domain; determining an association period (for the said first symbol types), wherein the association period is sufficient to allow all synchronization signal block indexes to be mapped at least once to RACH occasions allocated in the first symbol type; and determining a variable K, wherein K association periods are required for mapping all synchronization signal block indexes relevant to full- duplex transmission at least once to additional RACH Occasions allocated in the second symbol type.

[0022] The method may further comprise: determining said association period such that, each synchronization signal block is mapped to a RACH Occasion allocated in the first symbol type within the association period; and determining said association period and said variable K such that, each synchronization signal block relevant to full-duplex transmission is mapped to an additional RACH Occasion allocated in the second symbol type within K consecutive association periods.

[0023] The method may further comprise initiating a random-access procedure with said access node using RACH Occasions configured in accordance with the configuration information, for example by transmitting a PRACH preamble on RACH Occasions associated with a selected synchronization signal block.

[0024] The method may further comprise determining an offset value for synchronization signal block indexes relevant to full-duplex transmission to be mapped with additional RACH occasions allocated in the said second symbol type. In some example embodiments, within a group of K association periods, the offset for the first association period is 0 and the offset for a subsequent association period is an increment of the last beam index mapped to the last RACH Occasion allocated in the second symbol type in the previous association.

[0025] In a fifth aspect, this specification describes computer-readable instructions which, when executed by a computing apparatus, cause the computing apparatus to perform (at least) any method as described herein (including the methods of the third and fourth aspects described above).

[0026] In a sixth aspect, this specification describes a computer-readable medium (such as a non- transitory computer-readable medium) comprising program instructions stored thereon for performing (at least) any method as described herein (including the methods of the third and fourth aspects described above).

[0027] In a seventh aspect, this specification describes an apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, causes the apparatus to perform (at least) any method as described herein (including the methods of the third and fourth aspects described above).

[0028] In an eighth aspect, this specification describes a computer program comprising instructions which, when executed by an apparatus (such as a UE), cause the apparatus to: receive configuration information from an access node of the mobile communication system, the configuration information including time and frequency allocation of RACH Occasions for the device, wherein first and second symbol types (e.g. first slots and second slots), each having a bandwidth, are available for transmission from the device to the access node, wherein in the said first symbol types (e.g. non-SBFD slots) the bandwidth is used for either uplink transmission or downlink reception and in the said second symbol types (e.g. SBFD slots) the bandwidth includes uplink and downlink sub-bands that are non-overlapping in the frequency domain; and determine an association period for the device, wherein the association period is sufficient to allow all synchronization signal block indexes to be mapped to at least one RACH occasion, as defined by said configuration information.

[0029] In a ninth aspect, this specification describes a computer program comprising instructions which, when executed by an apparatus (such as a UE), cause the apparatus to: receive configuration information from an access node of the mobile communication system, the configuration information including time and frequency allocation of RACH Occasions for the device, wherein first and second symbol types, each having a bandwidth, are available for transmission from the device to the access node, wherein in the said first symbol types the bandwidth is used for either uplink transmission or downlink reception and in the said second symbol types the bandwidth includes uplink and downlink sub-bands that are nonoverlapping in the frequency domain; determine an association period (for the said first symbol types), wherein the association period is sufficient to allow all synchronization signal block indexes to be mapped at least once to RACH occasions allocated in the first symbol type; and determine a variable K, wherein K association periods are required for mapping all synchronization signal block indexes relevant to full-duplex transmission at least once to additional RACH Occasions allocated in the second symbol type.

[0030] In a tenth aspect, this specification describes an apparatus (e.g. a device, such as a user device or user equipment) comprising: a first input (or some other means) for receiving configuration information from an access node of the mobile communication system, the configuration information including time and frequency allocation of RACH Occasions for the device, wherein first and second symbol types (e.g. first slots and second slots), each having a bandwidth, are available for transmission from the device to the access node, wherein in the said first symbol types (e.g. non-SBFD slots)the bandwidth is used for either uplink transmission or downlink reception and in the said second symbol types (e.g. SBFD slots) the bandwidth includes uplink and downlink sub-bands that are non-overlapping in the frequency domain; and a processor (or some other means) for determining an association period for the device, wherein the association period is sufficient to allow all synchronization signal block indexes to be mapped to at least one RACH occasion, as defined by said configuration information.

[0031] In an eleventh aspect, this specification describes an apparatus (e.g. a device, such as a user device or user equipment) comprising: a first input (or some other means) for receiving configuration information from an access node of the mobile communication system, the configuration information including time and frequency allocation of RACH Occasions for the device, wherein first and second symbol types (e.g. first slots and second slots), each having a bandwidth, are available for transmission from the device to the access node, wherein in the said first symbol types (e.g. non-SBFD slots) the bandwidth is used for either uplink transmission or downlink reception and in the said second symbol types (e.g. SBFD slots) the bandwidth includes uplink and downlink sub-bands that are nonoverlapping in the frequency domain; a first processor (or some other means) for determining an association period (for the said first symbol types), wherein the association period is sufficient to allow all synchronization signal block indexes to be mapped at least once to RACH occasions allocated in the first symbol type; and a second processor (or some other means) for determining a variable K, wherein K association periods are required for mapping all synchronization signal block indexes relevant to full-duplex transmission at least once to additional RACH Occasions allocated in the second symbol type. Brief Description of the Drawings

[0032] Example embodiments will now be described by way of non-limiting example, with reference to the accompanying drawings, in which :

[0033] FIG. 1 is a block diagram of a system in accordance with an example embodiment;

[0034] FIG. 2 is a message flow sequence in accordance with an example embodiment;

[0035] FIG. 3 is a flow chart in accordance with an example embodiment;

[0036] FIG. 4 is a data structure used in some example embodiments;

[0037] FIG. 5 shows an example of synchronisation signal block (SSB) to RACH occasion (RO) mapping;

[0038] FIG. 6 is a block diagram showing communication slots or symbols in accordance an example subband non-overlapping full duplex (SBFD) implementation;

[0039] FIG. 7 is a data structure in accordance with an example embodiment;

[0040] FIG. 8 is a block diagram showing communication slots and symbols in accordance an example subband non-overlapping full duplex (SBFD) implementation;

[0041] FIG. 9 is a message flow sequence in accordance with example embodiments;

[0042] FIG. 10 is a flow chart in accordance with an example embodiment;

[0043] FIG. 11 is a message flow sequence in accordance with example embodiments;

[0044] FIG. 12 is a flow chart in accordance with an example embodiment;

[0045] FIG. 13 is a message flow sequence in accordance with example embodiments;

[0046] FIG. 14 is a flow chart in accordance with an example embodiment;

[0047] FIG. 15 is a message flow sequence in accordance with example embodiments;

[0048] FIG. 16 is a data structure used in an example embodiment;

[0049] FIG. 17 is a schematic diagram of a system that may be used to implement one or more of the example embodiments; and

[0050] FIG. 18 shows tangible media for storing computer-readable code which when run by a computer may perform methods according to example embodiments described herein.

[0051] Detailed Description

[0052] FIG. 1 is a block diagram of a system, indicated generally by the reference numeral 10, in accordance with an example embodiment. The system 10 comprises a user equipment 12 (or some other mobile communication device) and a network node 14. The network node may be a gNB or similar node. Two-way communication between the UE 12 and the network node 14 is possible, as indicated in FIG. 1. In 5G New Radio (5G NR), a number of mechanisms to enable the UE 12 to access the network node 14 are provided. These include contention based random access (CBRA) procedures, including 4-step RACH (Rel-15) and 2-step RACH (Rel-16), and contention-free random-access procedure (CFRA). Such procedures are typically initiated by the transmission of a suitable message by the UE 12 to network node 14.

[0053] FIG. 2 is a message flow sequence, indicated generally by the reference numeral 20, in accordance with an example embodiment. The sequence 20 shows messages transmitted between the UE 12 and the network node 14 of the system 10. The message flow sequence 20 shows an example 4-step RACH process. Note that although a 4-step RACH procedure is discussed (given its relevance in practical deployments), the concepts described herein are applicable to other CBRA and CFRA procedures.

[0054] The sequence 20 starts with a first message 22 being sent from the UE 12 to the network node 14. The message 12 is a preamble, often referred to as Msgl or PRACH, that is sent via a physical random-access channel (PRACH). As discussed further below, the message 12 may be sent using a specific resource called RACH occasion (RO), mapped to one or more SSB beams according to a certain pattern.

[0055] The network node 14 responds to the first message 22 by sending a second message 23 to the UE 12. The second message is a random-access response (RAR) message, often referred to as Msg2. The second message 22 may include a detected preamble ID, a timeadvance command, a TC-RNTI, and uplink (UL) grant for the transmission of Msg3 on PUSCH.

[0056] The UE 12 response to the second message 23 by sending a third message 24 (often referred to as Msg3 or RRC request) to the network node 14. The third message 24 is sent over the scheduled PUSCH with an ID for contention resolution.

[0057] Finally, the network node 14 transmits a contention resolution message 25 (often referred to as Msg4 or RRC setup. The fourth message 25 may include the contention-resolution ID.

[0058] Upon reception of Msg4, the UE 12 may send an ACK (not shown in FIG. 2) on a PUCCH if its contention-resolution ID is carried by Msg4. This completes the 4-step RACH. FIG. 3 is a flow chart, indicated generally by the reference numeral 30, in accordance with an example embodiment. The flow chart 30 shows a preliminary process that may be carried out before the first message 22 of the message flow sequence 20 is sent. The flow chart 30 shows an example beam synchronization signal block (SSB) beam selection arrangement.

[0059] The flow chart 30 starts, at step 32, with a downlink beam sweeping process in which a plurality of SSB beams are received at the UE 12 from the network node 14. At step 34, the UE 12 selects the index of a preferred SSB beam (that may be the "best" beam according to some metric) and decodes the associated PBCH for MIB, SIB and so on.

[0060] At step 36, the index selected in step 34 is used by the UE 12 to identify a suitable RACH Occasion (RO) for the preamble transmission (e.g. in Msgl of the algorithm 20), according to the SSB-to-RO mapping conveyed by SIB1. By way of example, the algorithm 30 finishes with the transmission of Msgl using the identified RO (see step 38).

[0061] A 2-step RACH procedure that is similar to 4-step RACH procedure presented above could also be used in example embodiment. In the 2-step RACH, the first and third message (Msgl and Msg3) are combined in a MsgA and sent without waiting for feedback from the UE in between (such as Msg2). Similarly, the network node 14 combines the second and fourth messages (Msg2 and Msg4) into MsgB.

[0062] As part of frequency and time domain resource allocation, an Information Element (IE) called RACH-ConfigGeneric can be used to specify the random-access parameters both for regular random access as well as for beam failure recovery. An example RACH- ConfigGeneric Information Element is as follows:

[0063] - ASN1START

[0064] - TAG-RACH-CONFIGGENERIC-START

[0065] RACH-ConfigGeneric : : = SEQUENCE { prach-Configurationlndex INTEGER (0..255), msgl-FDM ENUMERATED {one, two, four, eight}, msgl-FrequencyStart INTEGER (0..maxNrofPhysicalResourceBlocks-l), zeroCorrelationZoneConfig INTEGER(0..15), preambleReceivedTargetPower INTEGER (-202..-60), preambleTransMax ENUMERATED {n3, n4, n5, n6, n7, n8, nlO, n20, n50, nlOO, n200}, powerRam pingStep ENUMERATED {dBO, dB2, dB4, dB6}, ra-Response Window ENUMERATED {sll, sl2, sl4, sl8, sIlO, sl20, sl4O, sl80},

[0066] [[ prach-ConfigurationPeriodScaling-IAB-rl6 ENUMERATED

[0067] {scfl,scf2,scf4,scf8,scfl6,scf32,scf64} OPTIONAL, - Need R prach-ConfigurationFrameOffset-IAB-rl6 INTEGER (0..63)

[0068] OPTIONAL, - Need R prach-ConfigurationSOffset-IAB-rl6 INTEGER (0..39)

[0069] OPTIONAL, - Need R ra-ResponseWindow-vl610 ENUMERATED { sl60, sll60}

[0070] OPTIONAL, - Need R prach-ConfigurationIndex-vl610 INTEGER (256..262)

[0071] OPTIONAL - Need R

[0072] ]],

[0073] [[ ra-ResponseWindow-vl700 ENUMERATED {sl240, sl320, sl640, sl960

[0074] SI1280, SI1920, SI2560} OPTIONAL — Need R

[0075] ]]

[0076] - TAG-RACH-CONFIGGENERIC-STOP

[0077] - ASN1STOP

[0078] The fields "prach-Configurationlndex", "msgl-FDM" and "msgl-Frequency start" in the RACH-CofigGeneric information element can be used to signal the time and frequency allocation of the RACH Occasions (ROs) to the UE. PRACH-Configurationlndex (PCI) maps, for example, to the tables in TS 38.211, which, among others, give the time domain resources and other important RACH parameters. The msgl-FDM shows how many ROs are frequency multiplexed in one instance, and msgl-FrequencyStart gives an offset of lowest PRACH transmission occasion in frequency domain with respective to PRBO.

[0079] With the parameters indicated by prach-Configurationlndex , a UE (such as the UE 12) can determine the preamble format for PRACH and apply the procedure specified in TS 38.211 (clause 5.3.2) to find the ROs in the time-domain.

[0080] FIG. 4 is a data structure, indicated generally by the reference numeral 40, used in some example embodiments. The data structure 40 illustrates an example of time-domain resource determination for RACH occasions, wherein the prach-Configurationlndex is 251. The prach-Configurationlndex (PCI) can be used to provide the information required for Msgl transmission (e.g. message 22 of the message sequence 20 described above).

[0081] With this index indicated, the UE can determine the following, based on the data structure 40 :

[0082] • Preamble format C2 should be used.

[0083] • ROs are allocated at the system frame numbers (nSFJV) that satisfy nSFNmod i = 0.

[0084] • Within each of the determined SFNs, ROs are allocated at subframe number 2 and 7.

[0085] • Within each of the determined subframes, the remaining parameters in the considered row indicate ROs will start at symbol number 0, 6, 14, 20. The symbol number is continuously counted regardless of the number of slots within the subframe, which depends on the sub-carrier spacing configured for PRACH.

[0086] • ROs duration is 6 symbols (although the actual duration of the preamble format can be less than that).

[0087] Thus, the data structure 40 is an example of the sort of time-domain resource indication used to define RO parameters.

[0088] The mapping of synchronization signal block (SSB) indexes to the determined RACH Occasion (ROs) may be required in order for a UE to understand which ROs are associated to the SSB index selected during the preliminary step before the start of the RACH procedure (e.g. as shown in the flow chart 30). The different SSB indexes are typically beamformed in different directions in the cell, hence selection of a wrong SSB index may result in a failure of the RACH procedure.

[0089] To this purpose, one parameter ssb-perRACH-OccasionAndCB-PreamblesPerSSB is configured in RACH-ConfigCommon and can be used to obtain the following information :

[0090] • the number of SS / PBCH block indexes (or preamble sets) per RO; and

[0091] • the number of contention-based preambles per SS / PBCH block index (or preamble set).

[0092] More precisely, for a Type-1 random access procedure, a UE (such as the UE 12) may be provided 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 can map the SSB indexes to the time-frequency grid of ROs (determined as described above) in increasing order of frequency resource indices, time resource indices of the ROs within a PRACH slots, and the PRACH slots, sequentially. FIG. 5 shows an example of SSB to RO mapping, indicated generally by the reference numeral 50, in accordance with legacy RO validation rules.

[0093] The mapping 50 shows an example of valid ROs in one frame, and further assumes the following additional configuration: DDDSU slot structure, Msgl-FDM = two; and ssb- perRACH-OccasionAndCB-PreamblesPerSSB is one-half. Based on the configuration, two ROs are multiplexed in the frequency domain (Msgl-FDM = two) and any two frequency- multiplexed ROs are mapped to the same SSB index (ssb-perRACH-OccasionAndCB- PreamblesPerSSB = 1 / 2).

[0094] In relation to the SSB-to-RO mapping, TS 38.213, for example, defines an association period, starting from frame 0, for mapping SSB indexes to PRACH occasions (i.e., ROs) as the smallest value in the set determined by the PRACH configuration period according to Table 1 below such that all of the SSB indexes are mapped at least once to the PRACH occasions within the association period. The PRACH configuration period referred to here may be determined at the UE based on the configured PRACH configuration index. In other words, an association period is a period of time wherein all SSB indexes are mapped to at least one RO.

[0095] TS 38.213 also defines an association pattern period as a period of time which includes one or more association periods and may be determined so that a pattern between PRACH occasions and SS / PBCH blocks repeats at most every 160 msec.

[0096] Note that an association period is one or multiple of PRACH configuration period following Table 1 below. Therefore, an association period may be referred to as a positive integer number, e.g., association period of 1 or association period of 2, meaning that association period of 1 or 2 PRACH configuration period, respectively. Table 1 : Mapping between PRACH configuration period and association period

[0097] 3GPP 5G NR currently supports two duplexing modes: frequency division (FDD) for paired bands and time division (TDD) for unpaired bands. Irrespective of the duplexing mode, uplink and downlink phases are typically separated in the time domain. This may create unnecessary latency, possibly reducing coverage and capacity depending on the considered layout. In TDD deployments, the situation can be further exacerbated by the fact that the scheduling offers lower dynamism, for example, the slot structure may be fixed and does not change very often in practice. This may result in rather limited time duration for the uplink in TDD.

[0098] Motivated by this, work is ongoing relating to the evolution of duplexing operations in NR that addresses these challenges. One of the objectives is to allow a network node to implement simultaneous DL transmission and UL reception on different physical resource blocks (PRBs) / subbands within an unpaired wideband NR cell. One approach, as discussed further below, is subband non-overlapping full duplex initial access (SBFD). (Note that SBFD as described herein is sometime know by other terms, such as cross-division duplexing (xDD) scheme or Flexible Duplexing (FDU).)

[0099] FIG. 6 is a block diagram, indicated generally by the reference numeral 60, showing communication slots or symbols in accordance an example subband non-overlapping full duplex initial access (SBFD) implementation.

[0100] In sub-band non-overlapping full duplex initial access (SBFD) operation, there are two slot or symbol types for both DL and UL transmissions, namely:

[0101] • SBFD slots or symbols, during which the non-overlapping DL subband(s) and UL subband(s) both exist, and

[0102] • Non-SBFD slots or symbols, during which the entire band is used for either DL or UL (i.e., legacy / full DL / UL slots).

[0103] By way of example, the SBFD implementation 60 includes first non-SBFD slots or symbols 62, SBFD slots or symbols 64 and second non-SBFD slots or symbols 66. The first non-SBFD slots or symbols 62 are downlink slots and the second non-SBDF slots or symbols 66 are uplink slots. The SBFD slots or symbols 64 include at least one downlink sub-band (e.g. upper and lower downlink sub-bands and an uplink sub-band).

[0104] As shown in FIG, 6, a guardband 65 is provided between downlink (DL) and uplink (UL) resource blocks (RBs) of the SBFD slots 64. The guardband 65 helps to provide isolation between UL and DL transmissions and may reduce the impact of self-interference (e.g. due to a network nodes own DL transmissions and UL reception) as well as cross-link interference (CLI) between UEs and between network nodes (e.g. gNBs).

[0105] FIG. 7 is a data structure, indicated generally by the reference numeral 70, in accordance with an example embodiment. The data structure 70 defines the following initial parameters:

[0106] • RACH configuration Option 1

[0107] • FR1 PCI : 99

[0108] • Msgl-FDM: 2

[0109] • msgl-FrequencyStart: 1

[0110] • SSB number : 6

[0111] • SSB per RO: 1 / 1

[0112] • PRACH configuration period (PCI: 99 SFN mod 1 = 0) : 10 msec.

[0113] Thus, the data structure 70 presents an RO configuration for legacy ROs (e.g. non-SBFD ROs) and additional ROs (e.g. SBFD ROs) in the time domain using PCI: 99 and in the frequency domain (Msgl-FDM : 2, msgl-FrequencyStart: 1). We consider the same parameters for legacy ROs and additional ROs since we consider RACH Configuration Option 1 for this example. However, as discussed further below, even though we are using the same parameters, the number of legacy / non-SBFD ROs (6) is higher than that of the additional / SBFD ROs (2) since the additional ROs overlapping with the guard band and the DL subband are dropped.

[0114] For this example, with a PCI: 99, the PRACH configuration period is 10ms. Therefore, to map all 6 SSBs to the available ROs, the best association pattern period for the legacy ROs will be association period of 1 (i.e., one PRACH configuration period). Since we have 6 ROs supported in a frame of 10ms, each frame can cover all 6 SSBs

[0115] Based on the legacy behaviour, a UE should determine only one association period based on the PRACH configuration period and the number of valid ROs. However, since SBFD introduces two different number of ROs based on the different RO types (additional / SBFD ROs and legacy / non-SBFD ROs), there exist two different association periods, namely, 1 (legacy ROs) or 4 (additional ROs) - see Table 2 below. This new UE behaviour is different compared to the legacy behaviour. Therefore, there is a need to define a new method for SBFD-aware UEs to determine an association period that considers both RO types (and also avoid any impact to the legacy association period determination of the legacy UEs).

[0116] Table 2: Mapping between PRACH configuration period and association period

[0117] A particular slot (such as the slots shown in FIG. 6) may comprise a plurality of symbols (e.g. 14 symbols). In the arrangement of FIG, 6, each of the symbols of a slot has the same type (e.g. all of the symbols have a SBFD type or a non-SBFD type). This is not essential to all example embodiments.

[0118] For example, FIG. 8 is a block diagram, indicated generally by the reference numeral 80, showing communication slots and symbols in accordance an example subband nonoverlapping full duplex (SBFD) implementation. The block diagram includes a first symbol type (a non-SBFD symbol, having uplink resources only in this example) and a second symbol type 83 (a SBFD symbol).

[0119] The block diagram 80 includes four slots (indicated by the reference numerals 85 to 88 respectively), which are not exactly matched to the symbols. The first slot 85 includes downlink resources as part of a non-SBFD symbol, the second slot 86 includes both uplink and downlink resources (as part of some, but not all of an SBFD symbol), the third slot 87 includes part of the SBFD symbol and also includes a non-SBFD symbol. Finally, the fourth slot 87 includes uplink resources as part of non-SBFD symbol. FIG. 9 is a message flow sequence, indicated generally by the reference numeral 90, in accordance with an example embodiment. The sequence 90 shows messages sent between, and actions taken at, the UE 12 and the network node 14 described above.

[0120] The sequence 90 starts with configuration information being sent (in message 91) from the access node 14 to the UE 12. The configuration information (which may be a PRACH Configuration Index, PCI) includes time and frequency allocation of RACH Occasions for the device, wherein first and second slots or symbols, each having a bandwidth, are available for transmission from the device to the access node. As discussed above, in the first slots or symbols (e.g. legacy / non-SBFD slots) the entire bandwidth can be used for either uplink transmission or downlink reception and in the said second slots or symbols (e.g. additional / SBFD slots), the bandwidth includes uplink and downlink sub-bands that a nonoverlapping in the frequency domain.

[0121] As shown in FIG. 9, the UE 12 determines an association period for the device at step 92 of the message sequence 90. The association period is sufficient to allow all synchronization signal block indexes to be mapped to at least one RACH occasion, as defined by said configuration information received in the message 91.

[0122] In the sequence 90, the UE 12 initiates a random-access procedure with said access node 14 using RACH Occasions configured in accordance with the configuration information. The random-access procedure includes sending an access message 93 from the UE 12 to the network node 14. The message 93 may be a PRACH preamble (e.g. Msg 1) sent on at least one of RACH Occasions associated with a selected synchronization signal block index.

[0123] FIG. 10 is a flow chart, indicated generally by the reference numeral 95, in accordance with an example embodiment. The steps of the flow chart may be carried out at the UE 12 and may be used to implement step 92 of the message sequence 80 described above.

[0124] The flow chart 95 starts at step 96, where configuration information is received at the UE. The configuration information may be that sent in the message 91 described above.

[0125] At step 96, first and second nominal association periods are determined by the UE. The first nominal association period is sufficient to allow a first set of synchronisation signal block indexes to be mapped to at least one RACH occasion of each first slot / symbol, wherein the first set of synchronisation signal block indexes includes all synchronisation signal block indexes. The second nominal association period is sufficient to allow a second set of synchronisation signal block indexes to be mapped to at least one additional RACH occasion of each second slot / symbol, wherein the second set of synchronisation signal block indexes includes all synchronisation signal block indexes relevant to full-duplex transmission. The first and second sets of synchronization signal block indexes may be configured by the access node.

[0126] At step 98, one of the first and second nominal association periods is selected as the association period. Thus, the association period determined in step 92 of the message sequence 90 may be that selected in step 98 of the flow chart 95. By way of example, the step 98 may comprise selecting the longer of the first and second nominal association periods as the association period.

[0127] FIG. 11 is a message flow sequence, indicated generally by the reference numeral 100, in accordance with an example embodiment. The sequence 100 shows messages sent between, and actions taken at, the UE 12 and the network node 14 described above. The sequence 100 provide details of an example implementation of the flow chart 95.

[0128] The flow chart 100 starts with the network node providing (and the SBFD aware UE 12 receiving) at least one RACH configuration 102 via SIB or RRC. The configuration 102 may comprise at least one PCI (PRACH configuration index).

[0129] The UE may additionally receive (in optional message 103), a subset of SSBs. The subset of SSBs is determined with respect to a condition that the SSBs in a sub-set of SSBs are all mapped at least once in the association period.

[0130] At step 104, the UE determines a nominal number for the association period of the additional ROs "nom - asso - SBFD" and a nominal number for the association period of the legacy ROs "nom - asso - legacy" using the legacy definition of association period (for example using the legacy PCI(s) indicated by the network in the message 102). Thus, step 104 is an implementation of step 97 of the flow chart 95.

[0131] In step 105, one of the association periods determined in step 104 is selected as the association period (thereby implementing operation 98 of the flow chart 95). Specifically, in the event that the nom - asso - SBFD > nom - asso - legacy, the UE 12 determines an actual number for the association period "act - asso" equal to the nom - asso - SBFD for the additional ROs. Otherwise, the UE determines act - asso equal to nom - asso - legacy for the additional ROs.

[0132] In some example embodiments, the nominal number for the association period of the additional ROs "nom - asso - SBFD" is based on subset of SSBs indicated by the network (in the optional message 103 described above) and the nominal number for the association period of the legacy ROs "nom - asso - legacy" uses the legacy definition of association period (e.g. using the legacy PCI(s) indicated by the network in the message 102).

[0133] The UE transmits a PRACH preamble 106 on at least one of the ROs associated with a SSB configured with respect to the new rule included in steps 104 and 105 outlined above.

[0134] Finally, the network monitors (in step 107) the reception of the PRACHs associated to SSBs with respect to the legacy and the new association period "nom - asso - SBFD" in case the nom - asso - SBFD is different from the legacy association period.

[0135] FIG. 12 is a flow chart, indicated generally by the reference numeral 110, in accordance with an example embodiment. The steps of the flow chart may be carried out at the UE 12 and may be used to implement step 92 of the message sequence 90 described above. Thus, the algorithm shown in the flow chart 110 is an alternative to that shown in the flow chart 95.

[0136] The flow chart 110 starts at step 112, where configuration information is received at the UE. The configuration information may be that sent in the message 91 described above or the step 96 of the flow chart 95.

[0137] At operation 114, an association period is determined based on first and second slots / symbols. Specifically, the association period is defined as the period of time in which all synchronization signal block indexes can be mapped to at least one RACH Occasion of said first slots / symbols and all synchronization signal block indexes relevant to full-duplex transmission can be mapped to at least one additional RACH Occasion of said second slots / symbols. FIG. 13 is a message flow sequence, indicated generally by the reference numeral 120, in accordance with an example embodiment. The sequence 120 shows messages sent between, and actions taken at, the UE 12 and the network node 14 described above. The sequence 120 provide details of an example implementation of the flow chart 110.

[0138] The flow chart 120 starts with the network node providing (and the SBFD aware UE 12 receiving) at least one RACH configuration 122 via SIB or RRC. The configuration 122 may comprise at least one PCI (PRACH configuration index).

[0139] The UE 12 also receives SSB subset information 123. The SSB subject information includes the variable N^BSBFDthat defines SS / PBCH block indexes to be covered by the additional / SBFD ROs. Optionally, the SS / PBCH block indexes may be a sub-set of the NyxBss / PBCH block indexes.

[0140] At step 124, the UE 12 determines a new association period (thereby implementing step 92 of the flow chart 90). The new association period may be determined in accordance with the following definition :

[0141] • For an SBFD-aware UE (such as the UE 12), an association period, starting from frame 0, for mapping SS / PBCH block indexes to PRACH occasions is the smallest integer number in the set determined by the PRACH configuration period such that N^SS / PBCH block indexes are mapped at least once to the UL PRACH occasions and N^BSBFDSS / PBCH block indexes are mapped at least once to the SBFD PRACH occasions, within the association period, where a UE obtains N^Bfrom the value of ssb-PositionsInBurst in SIB1 or in ServingCellConfigCommon or in SSB-MTC-AdditionalPCI, and N^BSBFDfroma nRRC parameter (e.g., number_SSBbeams_SBFD_RO) configured by the network.

[0142] The UE transmits a PRACH preamble 125 on at least one of the ROs associated with a SSB configured with respect to the association period definition outlined above.

[0143] Finally, at step 126, the network node 14 monitors the reception of the PRACHs associated to SSBs with respect to the legacy and the new association period for the legacy and for the SBFD-aware UEs respectively. FIG. 14 is a flow chart, indicated generally by the reference numeral 130, in accordance with an example embodiment. The steps of the flow chart may be carried out at the UE 12 and may be used to implement step 92 of the message sequence 90 described above. Thus, the algorithm shown in the flow chart 130 is an alternative to that shown in the flow charts 95 and 110.

[0144] The flow chart 130 starts at step 132, where configuration information is received at the UE. The configuration information may be that sent in the message 91 described above or the step 96 of the flow chart 95 or step 112 of the flow chart 110. The configuration information may including time and frequency allocation of RACH Occasions for the device, wherein first and second slots / symbols, each having a bandwidth, are available for transmission from the device to the access node, wherein in the said first slots / symbols (non-SBFD slots / symbols) the bandwidth is used for either uplink transmission or downlink reception and in the said second slots / symbols (SBFD slots / symbols) the bandwidth includes non-overlapping uplink and downlink sub-bands.

[0145] At step 134, an association period is determined by the UE. Specifically, the association period is sufficient to allow all synchronization signal block indexes to be mapped to at least one RACH occasion of each first slot / symbol.

[0146] At step 136, a variable K is determined. The variable K is defined such that K association periods are required for mapping all synchronization signal block indexes relevant to full- duplex transmission at least once to additional RACH Occasions of each second slot / symbol.

[0147] At step 138, an offset value is determined for synchronization signal block indexes to be mapped with additional RACH occasions of said second slots / symbols.

[0148] FIG. 15 is a message flow sequence, indicated generally by the reference numeral 140, in accordance with an example embodiment. The sequence 140 shows messages sent between, and actions taken at, the UE 12 and the network node 14 described above. The sequence 140 provide details of an example implementation of the flow chart 130.

[0149] The flow chart 140 starts with the network node providing (and the SBFD aware UE 12 receiving) at least one RACH configuration 142 via SIB or RRC. The configuration 142 may comprise at least one PCI (PRACH configuration index). At step 144, the UE 12 determines the legacy association period, the variable K and the offset described above.

[0150] The legacy association period may be determined using the PCI(s) obtained from the network node in the message 142.

[0151] The SSB-to-ROs mapping for additional ROs may be determined using the determined legacy association period, at least one offset and the determined value of K as follows:

[0152] • For each of the association period, the offset is applied such that all N^BSBFD SS / PBCH block indexes are mapped at least once to additional ROs across K consecutive association periods.

[0153] • The SSB-to-ROs mapping for additional ROs repeats for every K consecutive association periods.

[0154] • Within each group of K association periods: the offset for the first association period is 0 and the offset for a subsequent association period is the last beam index mapped to the last SBFD-RO in the previous association period plus 1.

[0155] At step 146, the UE 12 transmits a PRACH preamble on at least one of the ROs associated with a SSB configured with respect to the rule included in step 144.

[0156] At step 148, the network node 14 monitors:

[0157] • The reception of the PRACHs associated to SSBs with respect to the legacy association period obtained from the PCI indicated by the network node 14; and

[0158] • The reception of the PRACHs associated with SSBs with respect to the new SSB-to-ROs mapping for additional ROs following the same steps required for SBFD aware UE to determine such mapping.

[0159] FIG. 16 is a data structure, indicated generally by the reference numeral 150, used in an example embodiment. Specifically, the data structure 150 illustrates an example of association period SSB-to-ROs mapping for additional ROs (SBFD-ROs) using the method described above with reference to the flow chart 130 and the message sequence 140.

[0160] The data structure 150 considers a PRACH configuration with msgl-FDM = 2,NTXB=NTXBSBFD =8- For each frequency index, SBFD-RO happens once every 3 ROs. It is assumed that the association period (determined using legacy definition of association period) for legacy UL ROs is one PRACH configuration period and equal 10ms. Following the method 130, the UE 12 first determines the legacy association period and perform SSB-to- ROs mapping for legacy UL ROs as per legacy for each of the association period. Secondly,

[0161] • For the first association period, the UE determines that the offset of beam indices is 0.

[0162] The UE then maps SSB indices #0, #1, #2, and #3 to the Additional ROs.

[0163] • For the second association period, the UE determines that the offset of beam indices is 3 (the last beam index mapped to the last SBFD-RO in the previous association period) +

[0164] 1 = 4. UE then maps SSB indices #4, #5, #6, and #7 to the additional ROs in the second association period.

[0165] • Since all N^BSBFD =8 aremapped at least once to Additional ROs in K = 2 association period, the UE determines that K = 2, and repeat the SSB-to-ROs mapping for the next K = 2 association periods.

[0166] It should be noted that although a number of different approaches have been described for implementing the message sequence 90, they each seek to avoid ambiguity in the definition of association period when there are two RO types (as shown in FIGS. 6 and 8, for example).

[0167] FIG. 17 is a schematic diagram of a system, indicated generally by the reference numeral 300, that may be used to implement one or more of the example embodiments described herein. The apparatus 300 comprises, for example, at least one processor 312 and at least one memory 314 storing instructions 315 that, when executed by the at least one processor, cause the apparatus 300 at least to perform the method or methods as disclosed herein, and any of the embodiments thereof. In an example, the at least one memory and the instructions (e.g. a computer program code, software), are configured, with the at least one processor, to cause the apparatus 300 to perform the method or methods as disclosed herein, and any of the embodiments thereof.

[0168] The processor(s) 312 may comprise circuitry, or be constituted as circuitry or circuitries, the circuitry or circuitries being configured to perform phases of methods in accordance with example embodiments described herein. As used in this application, the term "circuitry" may refer to one or more or all of the following : (a) hardware-only circuit implementations, such as implementations in only analog and / or digital circuitry, and (b) combinations of hardware circuits and software, such as, as applicable: (i) a combination of analog and / or digital hardware circuit(s) with software / firmware and (ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a user equipment, to perform various functions) and (c) hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation. This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

[0169] The memory 314 may be implemented using any suitable data storage technology. The memory may comprise a database for storing data. The memory 314 may be at least in part external to apparatus 300 but accessible to apparatus 300.

[0170] The instructions 315 may be comprised in a computer readable medium or a non-transitory computer readable medium. A term non-transitory, as used herein, is a limitation of the medium itself (i.e. tangible, not a signal) as opposed to a limitation on data storage persistency (e.g. random access memory, RAM, vs. read only memory, ROM).

[0171] For example, the apparatus 300 may be a terminal device, such as the UE 12 described above. As another example, the apparatus is comprised in such a terminal device, e.g. as a chipset configured to control the terminal device. The apparatus 300 may be caused or configured to perform any of the methods or implement any of the message sequences described above (such as any of the methods 90, 110 and 130 and the message sequences 80, 100, 120 and 140).

[0172] As another example, the apparatus 300 may be a network node, e.g. the network node 14 described above. In another embodiment, the apparatus is comprised in such a network node, e.g. as a chipset configured to control the network node. The apparatus 300 may be caused or configured to perform any of the methods or implement any of the message sequences described above (such as any of the methods 95, 110 and 130 and the message sequences 90, 100, 120 and 140).

[0173] The apparatus may comprise one or more entities of any of protocol layers, such as a MAC entity, an R.RC entity, an RLC entity, a PDCP entity or a PHY entity.

[0174] The apparatus 300 may comprise a radio interface 316. The radio interface 316 may provide the apparatus 300 with communication capabilities. The radio interface 316 may comprise a receiver configured to receive information in accordance with at least one cellular or non- cellular standard. The radio interface 316 may comprise a transmitter configured to transmit information in accordance with at least one cellular or non-cellular standard. The receiver may comprise more than one receiver. The transmitter may comprise more than one transmitter. The radio interface 316 may comprise a transceiver configured to receive and transmit information in accordance with at least one cellular or non-cellular standard. The transceiver may comprise more than one transceiver.

[0175] The apparatus 300 may comprise a user interface 318 comprising, for example, at least one of a keypad, a microphone, a touch display, a display, a speaker, etc. The user interface 318 may be used to control the apparatus by the user. The user interface 318 may be external to the apparatus 300. For example, the apparatus 300 may be connected to another device, such as a computer, either via wireless or wired connection, and the apparatus 300 controlled by the user via the computer.

[0176] In an embodiment, at least some of the processes described herein may be carried out by an apparatus comprising means for carrying out at least some of the described processes. Means for performing method steps as disclosed herein may include software and / or hardware components of the apparatus 300. For example, the at least one processor 312, the memory 314, and the computer program code form means for carrying out the method or methods as disclosed herein, and any of the embodiments thereof. As used herein the term "means" is to be construed in singular form, i.e. referring to a single element, or in plural form, i.e. referring to a combination of single elements. Therefore, terminology "means for [performing A, B, C]", is to be interpreted to cover an apparatus in which there is only one means for performing A, B and C, or where there are separate means for performing A, B and C, or partially or fully overlapping means for performing A, B, C. Further, terminology "means for performing A, means for performing B, means for performing C" is to be interpreted to cover an apparatus in which there is only one means for performing A, B and C, or where there are separate means for performing A, B and C, or partially or fully overlapping means for performing A, B, C.

[0177] FIG. 18 shows tangible media 365 for storing computer-readable code which when run by a computer may perform methods according to example embodiments described herein. Tangible media 365 may be non-transitory media. The tangible media 365 could, for example, be a CD, a DVD, a USB stick, a blue ray disk, etc. The tangible media 365 stores computer program code, causing an apparatus to perform the method of any preceding process for example as disclosed in relation to the flow diagrams and related features thereof.

[0178] Names of network elements, protocols, and methods are based on current standards. In other versions or other technologies, the names of these network elements and / or protocols and / or methods may be different, as long as they provide a corresponding functionality. For example, embodiments may be deployed in 2G / 3G / 4G / 5G networks and further generations of 3GPP but also in non-3GPP radio networks such as WiFi.

[0179] A memory may be volatile or non-volatile. It may be e.g. a RAM, a SRAM, a flash memory, a FPGA block ram, a DCD, a CD, a USB stick, and a blue ray disk.

[0180] If not otherwise stated or otherwise made clear from the context, the statement that two entities are different means that they perform different functions. It does not necessarily mean that they are based on different hardware. That is, each of the entities described in the present description may be based on a different hardware, or some or all of the entities may be based on the same hardware. It does not necessarily mean that they are based on different software. That is, each of the entities described in the present description may be based on different software, or some or all of the entities may be based on the same software. Each of the entities described in the present description may be embodied in the cloud.

[0181] Implementations of any of the above described blocks, apparatuses, systems, techniques or methods include, as non-limiting examples, implementations as hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof. Some embodiments may be implemented in the cloud. It is to be understood that what is described above is what is presently considered the preferred embodiments. However, it should be noted that the description of the preferred embodiments is given by way of example only and that various modifications may be made without departing from the scope as defined by the appended claims.

Claims

28Claims1. A device of a mobile communication system, the device comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the device to: receive configuration information from an access node of the mobile communication system, the configuration information including time and frequency allocation of RACH Occasions for the device, wherein first and second symbol types, each having a bandwidth, are available for transmission from the device to the access node, wherein in the said first symbol types the bandwidth is used for either uplink transmission or downlink reception and in the said second symbol types the bandwidth includes uplink and downlink sub-bands that are non-overlapping in the frequency domain; and determine an association period for the device, wherein the association period is sufficient to allow all synchronization signal block indexes to be mapped to at least one RACH occasion, as defined by said configuration information.

2. The device of claim 1, wherein the instructions, when executed by the at least one processor, further cause the device to: initiate a random-access procedure with said access node using RACH Occasions configured in accordance with the configuration information.

3. The device of claim 2, wherein the instructions, when executed by the at least one processor, further cause the device to: initiate said random-access procedure by transmitting a PRACH preamble on at least one of RACH Occasions associated with a selected synchronization signal block index.

4. The device of any one of claims 1 to 3, wherein the instructions, when executed by the at least one processor, further cause the device to: determine a first nominal association period, wherein the first nominal association period is sufficient to allow a first set of synchronisation signal block indexes to be mapped at least once to RACH occasions allocated in the first symbol type, wherein the first set of synchronisation signal block indexes includes all synchronisation signal block indexes; determine a second nominal association period, wherein the second nominal association period is sufficient to allow a second set of synchronisation signal block indexesto be mapped at least once to additional RACH occasions allocated in the second symbol type, wherein the second set of synchronisation signal block indexes includes all synchronisation signal block indexes relevant to full-duplex transmission; and select one of the first and second nominal association periods as the association period.

5. The device of claim 4, wherein the instructions, when executed by the at least one processor, are further configured to select said association period by: selecting the longer of the first and second nominal association periods as the association period.

6. The device of claim 4 or claim 5, wherein the first and second sets of synchronization signal block indexes are configured by the access node.

7. The device of any one of claims 1 to 3, wherein the association period is defined as the period of time in which all synchronization signal block indexes can be mapped at least once to RACH Occasions allocated in the said first symbol type and all synchronization signal block indexes relevant to full-duplex transmission can be mapped at least once to additional RACH Occasions allocated in the said second symbol type.

8. The device as of one of the preceding claims, wherein the association period is a positive integer defining an integer multiple of a PRACH configuration period.

9. The device of any one of the preceding claims, wherein the device is a user equipment.

10. A method comprising: receiving configuration information from an access node of the mobile communication system, the configuration information including time and frequency allocation of RACH Occasions for the device, wherein first and second symbol types, each having a bandwidth, are available for transmission from the device to the access node, wherein in the said first symbol types the bandwidth is used for either uplink transmission or downlink reception and in the said second symbol types the bandwidth includes uplink and downlink sub-bands that are non-overlapping in the frequency domain; and determining an association period for the device, wherein the association period issufficient to allow all synchronization signal block indexes to be mapped to at least one RACH occasion, as defined by said configuration information.

11. The method of claim 10, further comprising: initiating a random-access procedure with said access node using RACH Occasions configured in accordance with the configuration information.

12. The method of claim 10 or claim 11, further comprising: determining a first nominal association period, wherein the first nominal association period is sufficient to allow a first set of synchronisation signal block indexes to be mapped at least once to RACH occasions allocated in the first symbol type, wherein the first set of synchronisation signal block indexes includes all synchronisation signal block indexes; determining a second nominal association period, wherein the second nominal association period is sufficient to allow a second set of synchronisation signal block indexes to be mapped at least once to additional RACH occasions allocated in the second symbol type, wherein the second set of synchronisation signal block indexes includes all synchronisation signal block indexes relevant to full-duplex transmission; and selecting one of the first and second nominal association periods as the association period.

13. The method of claim 10 or claim 11, wherein the association period is defined as the period of time in which all synchronization signal block indexes can be mapped at least once to RACH Occasions allocated in the said first symbol type and all synchronization signal block indexes relevant to full-duplex transmission can be mapped at least once to additional RACH Occasions allocated in the said second symbol type.

14. A computer product comprising program instruction which, when executed by an apparatus, cause the apparatus to: receive configuration information from an access node of the mobile communication system, the configuration information including time and frequency allocation of RACH Occasions for the device, wherein first and second symbol types, each having a bandwidth, are available for transmission from the device to the access node, wherein in the said first symbol types the bandwidth is used for either uplink transmission or downlink reception and in the said second symbol types the bandwidth includes uplink and downlink sub-bands that are non-overlapping in the frequency domain; anddetermine an association period for the device, wherein the association period is sufficient to allow all synchronization signal block indexes to be mapped to at least one RACH occasion, as defined by said configuration information.

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