GB2578682A - Method and apparatus for random access in an integrated access and backhaul communication system - Google Patents

Abstract

An integrated access and backhaul, IAB, wireless communication system, is coupled to a core network. The IAB system comprises a first base station (possible a donor node), a further base station (possibly a relay IAB node or child IAB node), and a plurality of remote wireless communication units (possibly UE). The remote units access the core network via at least the first base station. At least one of the base stations comprises a processor arranged to: read broadcast system information and obtain therefrom a physical random access channel (PRACH) index; determine whether the time and frequency location of the PRACH for communication with the core network overlaps with an associated remote unit PRACH to be used by remote units; and, in response thereto, configure and apply a PRACH offset to the time and frequency location of the PRACH. The system may avoid PRACH conflict under half-duplex operation.

Description

METHOD AND APPARATUS FOR RANDOM ACCESS IN AN INTEGRATED ACCESS

AND BACKHAUL COMMUNICATION SYSTEM

Technical Field

[0001] The field of this invention relates generally to implementing random access in an integrated access and backhaul communication system. In particular, the field of this invention relates to a random access preamble design and offset configuration for an integrated access and backhaul communication system.

Background

[0002] In recent years, third generation (3G) wireless communications have evolved to the long term evolution (LTE) cellular communication standard, sometimes referred to as 4th generation (4G) wireless communications. Both 3G and 4G technologies are compliant with third generation partnership project (3GPPTM) standards. 4G networks and phones were designed to support mobile internet and higher speeds for activities, such as video streaming and gaming. The 3GPPTM standards are now developing a fifth generation (SG) of mobile wireless communications, which is set to initiate a step change in the delivery of better communications, for example powering businesses, improving communications within homes and spearheading advances such as driverless cars.

[0003] One of the potential technologies targeted to enable future cellular network deployment scenarios and applications is the support for wireless backhaul and relay links enabling flexible and very dense deployment of SG-new radio (NR) cells without a need for densifying the transport network proportionately. Due to the expected larger bandwidth available for NR compared to long term evolved (LTETM) (e.g. mmWave spectrum) along with the native deployment of massive multiple-in/multiple-out (MIMO) or multi-beam systems in NR creates an opportunity to develop and deploy integrated access and backhaul (IAB) links. It is envisaged that this may allow easier deployment of a dense network of self-backhauled NR cells in a more integrated manner, by building upon many of the control and data channels/procedures defined for providing access to UEs. An example illustration of a network with such TAB links is shown in Figure 1, where TAB nodes (or relay nodes (rTRPs) or relay TAB nodes, as these terms are used interchangeably herein) are configured to multiplex access and backhaul links in time, frequency, or space (e.g. beam-based operation).

[0004] Referring to FIG. 1, a known simplified 5G architecture diagram 100 illustrates how an Integrated Access and Backhaul (TAB) network is deployed. Here, a first 5G base station 102 supporting communications within a coverage area 104, including communication support for a wireless communication unit, sometimes referred to as a terminal device, such as a user equipment UE 106. In 5G, the UE 106 is able to support traditional Human Type Communications (HTC) or the new emerging Machine Type Communications (MTC). The known simplified architecture diagram 100 includes a second 5G base station 112 supporting communications within a coverage area 114, including communication support for a UE 116 and a third 5G base station 122 supporting communications within a coverage area 124, including communication support for a UE 126. A wireless backhaul connection 132, 133, generally an Xn (based on X2) interface connects the third 5G base station 122 with the first 5G base station 102 and second 5G base station 112. The third 5G base station 122 is also connected to the core network via a more traditional wired connection, such as fibre 134.

[0005] In this regard, in an TAB scenario, node A (i.e. third 5G base station 122) is considered a donor TAB node and node B (i.e. first 5G base station 102) and node C (i.e. second 5G base station 112) are identified as relay TAB nodes.

[0006] One of the main objectives of TAB is to provide radio access network (RAN)-based mechanisms to support dynamic route selection to accommodate short-term blocking and transmission of latency-sensitive traffic across backhaul links. This objective is also relevant to resource allocation (RA) between access and backhaul links under half-duplexing constraints. In the NR standard, there are three RA modes defined, namely time division multiplex (TDM), frequency division multiplex (FDM) and space division multiplex SDM (e.g. beam-based operation). No matter which RA scheme is applied, the inventors have identified that there always exists a problem for inter-relay channel monitoring for topology management when a communication (backhaul) blockage occurs.

[0007] When nodes B and C conduct random access, they can follow the same procedure as the UEs within the coverage of node A, e.g. TIE 126. However, if the backhaul link 132 between node B and node A is blocked, node B might need to be connected to node C to form a multi-hop relay network. In such a case, the distance between node B and node C could be much larger than the distance between the node C UE 116 and node C (i.e. second 5G base station 112). Since the random access preamble format is decided by the cell radius, the preamble used for node C UE 116 might not be suitable for another TAB node, e.g., node B (i.e. first 5G base station 102). Hence, a first problem that the inventors have recognised and appreciated is the selection and use of preamble formats to achieve a particular coverage area in an lAB system.

[0008] Node A is the donor TAB node, node B and C are relay TAB nodes. When nodes B and C conduct random access, they can follow the same procedure as the TJEs within the coverage of node A. However, if the backhaul link between B and A is blocked, node B might need to be connected to node C to form a multi-hop relay network. Tn such a case, the distance between B and C could be much larger than the distance between node C UE and node C. Since the random access preamble format is decided by the cell radius, the preamble used for node C UE might not be suitable for another lAB node, e.g., node B. [0009] The timing for PRACH transmission can be configured by PRACH configuration index, as shown in Table 6.3.3.2-4 of TS 38.211, which is incorporated herein by reference. For example, if index '0' and index '2' are configured for TAB node and its associated UEs, for TAB node, slot 4, 9, 14, 19, 24, 29, 34, 39 will be used by TAB node to transmit PRACH and slot 9, 19, 29, 39 will be used by UEs to transmit PRACH. Tn slot 9, 19, 29 and 39, the TAB node needs to transmit PRACH and receive PRACH from UE at the same time, which violates the half-duplex constraint. Hence, a second problem that the inventors have recognised and appreciated is associated with the half-duplex constraint imposed in JAB system, whereby the TAB RACH occasions and UE RACH occasions should be configured to not overlap with each other.

100101 Thus, examples of the invention aim to address or alleviate one or more of the abovementioned problems with known 1AB systems.

Summary of the Invention

[0011] In a first aspect of the invention, an integrated access and backhaul, TAB, wireless communication system is described that includes a first base station (e.g. a donor TAB node), at least one further base station, and a plurality of remote wireless communication units, wherein the communication units obtain access to the core network via at least the first base station, and in some examples via the at least one further base station to the first base station and thereafter to the core network. The base stations include: a transceiver; and a processor, operably coupled to the transceiver and arranged to: read broadcast system information and obtain therefrom a time and frequency location of a physical random access channel (PRACH), sometimes herein referred to as a PRACH index' for a specific time and frequency location. The processor is also configured to determine whether the PRACH index for the base station itself (e.g., a relay IAB node) overlaps with an associated UE PRACH to be used by at least one of the communication units. If the processor determines that the PRACH index overlaps with a UE PRACH to be used by at least one of the communication units, the processor configures and applies a PRACH offset. The time and frequency location of the PRACH (e.g. PRACH index), with the offset, is then broadcast to the communication units, e.g. the UEs.

[0012] In this manner, by determining whether a PRACH overlap exists, and configuring an offset to be used with the PRACH in response to a positive determination, the IAB node is able to facilitate half-duplex operation of the IAB node and avoid PRACH conflicts.

100131 In some examples, the at least one further base station may include a second base station (e.g., a relay IAB node), a third base station (e.g. a child IAB node). In this example, the communication units may obtain access to the core network via the second base station to the first base station and thereafter to the core network, or in one example via the third base station to the second and then the first base station and thereafter to the core network.

[0014] In some optional examples, for example in a 5G system, the second base station (e.g. when configured as a relay IAB node), may be configured to derive a PRACH offset based on its own configuration index obtained from its parent (first) base station.

[0015] In some optional examples, the configuration of the time and frequency location of a PRACH offset may take into account resource allocations. For example, the configuration of the PRACH index offset may take into account whether communication links to UEs and any associated child IAB nodes and an offset UE PRACH should only be assigned to a child link (a link between the second base station and third base station).

[0016] In some optional examples, an offset may be based on a maximum configuration index. In some examples, the maximum configuration index may be '39'. In some examples, the binary maximum configuration index may be '64', thereby resulting in a range of -64 to 64.

100171 In some optional examples, the time and frequency location of the PRACH offset may include at least one resource from a group of: symbol, slot, subframe and system frame number, SFN. In some optional examples, a same resource may be fixed. In some optional examples the resource may traverse multiple resources from the group. In this manner, the granularity of the time and frequency location of PRACH offset (e.g. PRACH index offset) may vary.

[0018] In some optional examples, the PRACH configuration, e.g., periodicity, preamble formats, etc., may be different for the associated UEs and child JAB nodes. In this context, it is envisaged that in some scenarios it may be necessary to configure different offset values for the associated UEs and child IAB nodes separately.

[0019] In some optional examples, the system information includes at least one additional information element (IE) configured to support the time and frequency location of the PRACH offset (e.g. PRACH index offset). In some optional examples, the supported time and frequency location of the PRACH offset (e.g. PRACH index offset) may use an existing or modified IE. In some optional examples, at least one RACH information element, IE, parameter in radio resource control, RRC, state, from a group of multiple sets of RACH parameters may be configured, where the at least one RACH IE parameter comprises expansion of a RACH-ConfigGeneric. In some optional examples, the expansion of the at least one RACH LE parameter may include at least one from a group of: definition of a new RRC IEs; adding of a new parameter to configure different RACH settings; expansion of a value range of current parameters, to differentiate between RACH configurations. -5 -

[0020] In some optional examples, orthogonal time multiplexing configuration of the RACH may include at least one from a group of: time multiplexing of access link random access resources and backhaul link random access resources within a single time slot, time multiplexing of access link random access resources and backhaul link random access resources that are allocated different time slots, time multiplexing of access link random access resources and backhaul link random access resources that are allocated different bandwidth parts, BWP, of a carrier frequency.

[0021] In a second aspect of the invention, a second base station for an integrated access and backhaul, TAB, wireless communication system according to the first aspect is described.

[0022] In a third aspect of the invention, a remote wireless communication unit is described, such as a UE for an integrated access and backhaul, IAB, wireless communication system. The remote wireless communication unit comprises a receiver and according to the first aspect is described.

[0023] In a fourth aspect of the invention, a method for random access in an integrated access and backhaul, IAB, wireless communication system performed by the first base station according to the first aspect is described.

[0024] In a fifth aspect of the invention, a method for random access in an integrated access and backhaul, IAB, wireless communication system performed by the second base station according to the second aspect is described.

[0025] In a sixth aspect of the invention, a method for random access in an integrated access and backhaul, IAB, wireless communication system performed by the remote wireless communication unit, such as a UE, according to the third aspect is described.

[0026]

Brief Description of the Drawings

100271 Further details, aspects and embodiments of the invention will be described, by way of example only, with reference to the drawings. In the drawings, similar reference numbers are used to identify like or functionally similar elements. Elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale.

100281 FIG. 1 illustrates a known simplified 5G architecture configured to support IAB.

[0029] FIG. 2 illustrates a simplified 5G architecture configured to support TAB, according to examples of the invention.

[0030] FIG. 3 illustrates a block diagram of an UE, adapted in accordance with some example embodiments of the invention.

[0031] FIG. 4 illustrates a block diagram of an IAB base station (or node), adapted in accordance with some example embodiments of the invention.

[0032] FIG. 5 illustrates a representation of a Time multiplexing of access link and backhaul link random access resources, with a representation of a random access resource allocation with offset for access link, according to examples of the invention.

[0033] FIG. 6 illustrates a first example of a simplified flowchart of an TAB node procedure, in accordance with some example embodiments of the invention.

[0034] FIG. 7 illustrates a second example of a simplified flowchart of an IAB node procedure, in accordance with some example embodiments of the invention.

[0035] FIG. 8 illustrates an example of a simplified flowchart of a remote wireless communication unit operation when receiving a PRACH configuration from a serving IAB node, in accordance with some example embodiments of the invention.

100361 FIG. 9 illustrates a simplified flowchart of a selection or creation of a preamble format by a serving IAB node, and subsequent use by a remote wireless communication unit, in accordance with some example embodiments of the invention.

[0037] Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and/or relative positioning of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention. It will be further appreciated that certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. It will also be understood that the terms and expressions used herein have the ordinary technical meaning as is accorded to such terms and expressions by persons skilled in the technical field as set forth above except where different specific meanings have otherwise been set forth herein.

Detailed Description

[0038] Examples of the invention describe a wireless communication system that includes a mechanism for improved efficiency of random access for IAB nodes in an IAB architecture. In accordance with examples of the invention, an offset value is introduced to UE PRACH transmissions, when they are determined as conflicting with the TAB node PRACH, e.g., the UE PRACH is offset by, say, -1 slot. For example, if index '0' and index '2' are configured for lAB node and its associated UEs, for lAB node, slot 4, 9, 14, 19, 24, 29, 34, 39 will be used by lAB node to transmit PRACH. Also, slots 9, 19, 29, 39 will be used by UEs to transmit PRACH. However, in accordance with examples of the invention, and after applying a suitable offset by, say, -1 slot, the UE PRACH slots are now 8,18,28,38. In this manner, the UE PRACH slots no longer conflict with the IAB node PRACH slots, and the IAB node is now able to transmit PRACH and receive PRACH from UE at the same time in a manner that does not violate the half-duplex constraint.

[0039] Although examples of the invention are described with reference to introducing a -1 slot offset, it is envisaged that any suitable resource offset, e.g. a -2 slot offset, a -3 slot offset, a subframe offset, a symbol offset, etc. may be used.

[0040] Although example embodiments of the invention are described with reference to different random access configurations for lAB nodes and UEs in a 5G architecture, it is -8 -envisaged that some aspects of the invention are not so constrained/limited. For example, it is envisaged that the different random access configurations may be enacted for a long Term Evolved (L 1hTM) system, or other such communication systems that utilise random access techniques.

[0041] Example embodiments are described with respect to FR2, since the main focus of TAB is on above FR2, i.e., 24.25 GHz -52.6 GHz. However, it is envisaged that the examples described herein apply equally to FR1, i.e. 450 MHz -6 GHz.

100421 Example embodiments are described with reference to radio access networks, which term encompasses and is considered to be equivalent to and interchangeable with communication cells, namely the facilitation of communications within a cell that may access other parts of the communication system as a whole.

[0043] Referring now to FIG. 2, part of a wireless communication system 200 is shown in outline, in accordance with one example embodiment of the invention. The wireless communication system 200 illustrates how an Integrated Access and Backhaul (IAB) network may be deployed in accordance with one example embodiment of the invention, where separate RACH is provided for use by an TAB node, e.g. a relay IAB node requiring a backhaul link or RACH access, and UEs requiring RACH access. Here, a donor IAB node A (sometimes referred to as a parent IAB node) 222 is configured to receive first access control RACH requests 250 from wireless communication units, sometimes referred to as a terminal device, such as a user equipment UE 226. In the context of the present invention, a relay IAB node B (e.g. a 50 base station) 202 uses a separate second RACH to access the donor IAB node to form a backhaul link AB' 232. Such a backhaul link may also carry communications to/from a second UE B 206, which has used a RACH access 255 to connect to the relay IAB node B 202.

[0044] Similarly, a further relay IAB child node C (e.g. a 50 base station) 212 uses a separate RACH to access the relay IAB node B 202 to form a backhaul link 'BC' 235, and thereafter the donor TAB node by joining the backhaul link 'AB' 232. Such a backhaul link may also carry communications to/from a third UE C 216, which has used a RACH access 260 to connect to the further relay IAB child node C 212.

[0045] The number of UEs associated with one TAB node, e.g., TAB child node C 212 in FIG. 2, could be much larger than the number of TAB nodes connected to IAB child node C 212. In fact, in practice, there might be only a very limited number of IAB nodes expected to be connected to a parent IAB node (i.e. an IAB node that serves relay IAB nodes). In NR, some resources in terms of symbol, slot, subframe and system frame number (SFN) are allocated for physical random access channels (PRACH) as shown in FIG. 5 and the periodicity of such resources are short so that UEs are able to transmit their random access preambles as soon as possible without causing too many collisions.

[0046] In accordance with one example of the invention, the TAB nodes 202, 212 and UEs such as UE 226 are allocated different preamble formats within RACH, to identify to the recipient (donor) IAB node 222 whether the RACH emanated from another IAB node 202, for example due to a backhaul blockage, or whether the RACH emanated from a UE 226. In accordance with another example of the invention, the TAB nodes 202, 212 and UEs, such as UE 226, may be allocated different time and/or frequency configurations within RACH, to identify to the recipient (donor) IAB node 222 whether the RACH emanated from another IAB node 202, for example due to a backhaul blockage, or whether the RACH emanated from a UE 226. In some examples of the invention, it can be appreciated that, to the donor lAB node 222, the 'relay lAB node B' 202 is a child JAB node, and to the relay IAB node B 202, the child JAB node C 212 in FIG. 2 is a child IAB node and the donor IAB node A 222 is a parent IAB node.

[0047] In the context of the present invention, the selection of preamble formats to be divided between IAB use and UE use can be made from the known preamble formats. The preamble formats for FR2 are defined in the below table I from the 3GPP standard at 6.3.3.1-2: Table 1: Preamble formats for LRk =139 and 4f R° = 15 -2" kHz where p E {0,1.2,3} -10 -Format I R A Af RA ATRA Support for cp restricted sets Al 139 15.2 kHz 2 2048k 2 it 288K-2 t A2 139 15-2" kHz 4 2048 2 ' 576v-2 ' - A3 139 15 2PlcHz 6 2048k 2-,1 R64 2 ' - B1 139 15 2/ kHz 2 2048k 2 " 216k-2 " -B2 139 15 211 kHz 4 2048k 2 ' 360K-2 ' B3 139 15 2/ kHz 6 2048k 2-'1 504x*2-" -B4 139 15 211 kHz 12 2048k 2 t' 936x-2 II CO 139 15 2P kHz 2048x-2 l 1240A 2-7 -C2 139 15.2ii kHz 4.2048K*2 7' 2048K*2 i [0048] The coverage of a PRACH is determined by the length of CP (TCP) as shown below.

TCP >= 2*Tprop+Td [1] Where: Tprop is the propogation delay; and Td is the root mean square (rms) delay spread [0049] According to the above equation, the maximum inter-node distance for 120k SCS is around 1.2km only, which is clearly not enough for 1AB node deployment. Hence, in accordance with examples of the invention, new PRACH preambles are proposed.

[0050] In some examples of the invention, the new PRACH preambles are based on the current C2 andior B4 preamble formats, as these support the largest cell size and link budget in the existing formats, respectively. Thus, for example, it is envisaged that the C2 preamble format may be used as a baseline, as it supports the largest coverage area. However, in other examples, it is envisaged that other preamble formats may be adopted to utilise the concepts herein described, such as any of the other preamble formats illustrated in Table 1.

100511 Access link and backhaul link have different requirements on random access link budget and preamble cyclic prefix (CP) length. For example, the random access link budget is relevant to a repetition level of the random access signature, i.e., Nu. CP length, i.e., Nr,,A determines the cell size, and these parameters are defined in 3GPP TS38.213.

[0052] In some examples, the inventors have proposed a design that utilises the fact that 1AB nodes employ higher power and more antennas than the UEs that they support. Hence, examples of the invention may be used to reduce the length of the preamble Nu, which defines the Link budget L, whilst increasing the duration of the cyclic prefixes (CP), as a larger propagation delay and a longer delay spread can be tolerated.

[0053] In some examples, the inventors have proposed new preamble formats for C2, referred to below in Table 2 as C3, C4 and CS.

Table 2:

Format L RA Ai' RA Nu v R A Support for " CP restricted sets C3 139 15.211 kHz 4 -2048k-* 2 II 2* *3/4 2048K-2 i C4 139 15-2111(Hz 4 -2048x ' * 2 3* *72 2048K.2 i C5 139 15 -211 kHz * 2048K.2 i 4.2048k2 ' /4 4* [0054] In Table 2, for a C3 preamble format, it is noted that the coverage is doubled, but the link budget is reduced by around 1.2 dB. Alternatively, for C4 preamble format, the coverage is extended by 3 times, but the link budget is reduced by around 3 dB. For a CS preamble format, the coverage is extended by four times, but the link budget is reduced by around 6 dB. Since 1AB nodes comprise more antennas and higher transmission power, the link budget reduction can be advantageously compensated. Thus, in this manner and in some examples, a new preamble format may be employed.

[0055] For B4, according to some examples of the invention, the coverage can be further extended following the same design principle as above. Here, the length of the preamble (Nu) may be modified as 2048K-2-" *K and K=1, 2, ... 12 and the number of cyclic prefix samples (Ncp) may be modified accordingly to 20482 * 2-P (12-K)+ 936/c*2-uas indicated in Table 3 below. Table 3: -12 -Format I. AIRA " NT RA Support for CP restricted sets 2048K*2** BK 139 15.2* kHz 2048x2-" *K (12-I<)+ 936k-*2-1' [0056] The coverage can be extended to around 15km for 120k Hz SCS by adjustment of the value of 'le.

[0057] FIG. 3 illustrates a high level block diagram of a wireless communication unit such as a user equipment (UE) 300 contains an antenna 302, for receiving transmissions, coupled to an antenna switch or duplexer 304 that provides isolation between receive and transmit chains within the UE 300. One or more receiver chains, as known in the art, include receiver front-end circuitry 306 (effectively providing reception, filtering and intermediate or base-band frequency conversion). The receiver front-end circuitry 306 is coupled to a signal processing module 308 (generally realized by a digital signal processor (DSP)). A skilled artisan will appreciate that the level of integration of receiver circuits or components may be, in some instances, implementation-dependent.

[0058] The controller 314 maintains overall operational control of the wireless communication unit 300. The controller 314 is also coupled to the receiver front-end circuitry 306 and the signal processing module 308. In some examples, the controller 314 is also coupled to a frequency generation circuit 317 and a memory device 316 that selectively stores operating regimes, such as decoding/encoding functions, synchronization patterns, code sequences, and the like. A timer 318 is operably coupled to the controller 314 to control the timing of operations (e.g. transmission or reception of time-dependent signals) within the UE 300.

[0059] As regards the transmit chain, this essentially includes an input module 320, coupled in series through transmitter/modulation circuitry 322 and a power amplifier 324 to the antenna 302, antenna array, or plurality of antennas. The transmitter/ modulation circuitry 322 and the power amplifier 324 are operationally responsive to the controller 314.

100601 The signal processor module 308 in the transmit chain may be implemented as distinct from the signal processor in the receive chain. Alternatively, a single processor may be -13 -used to implement a processing of both transmit and receive signals, as shown in FIG. 3. Clearly, the various components within the wireless communication unit 325 can be realized in discrete or integrated component form, with an ultimate structure therefore being an application-specific or design selection.

[0061] In accordance with examples of the invention, the processor 308 and transceiver (e.g. transmitter/modulation circuitry 322) of the TAB node are configured to communicate with another TAB node (e.g. 5G gNB child node 212 in FIG. 2) in an TAB architecture by using a RACH that is configured with a UE-specific preamble format, in order to distinguish the UE RACH from another RACH received at the recipient TAB node from another TAB node. In particular examples of the invention, the UE-specific preamble format includes a PRACH offset that has been configured by the TAB node, (e.g. either donor TAB node A 222 or derived from the relay node 202 itself, based on its own configuration index obtained from its parent node, e.g. donor TAB node A 222). The processor 308 and receiver front-end circuitry 306 are also configured to receive an acknowledgement of a successful RACH attempt in response to the UEspecific preamble format. The two options can be applied in centralized and distributed IAB networks, respectively.

[0062] In accordance with examples of the invention, the processor 308 and transceiver (e.g. transmitter/modulation circuitry 322) of the UE are additionally or alternatively configured to communicate with an TAB node in an TAB architecture by using a PRACH that is configured with an offset, in order to avoid violation of the half-duplex constraint and avoid conflict with other UEs, in order to distinguish the UE PRACH from another TAB node RACH.

[0063] In some examples, at least one PRACH offset is described as it is envisaged that, say, a positive offset may be applied in one direction, say by an TAB node, and a negative offset may be applied in the other direction, say for a UE, thereby allowing half-duplex operation by assigning a PRACH offset between more than one entity in the communication chain.

[0064] Referring now to FIG. 4, high level block diagram of an TAB node (e.g. a 5G wireless base station) 400 is illustrated, where the IAB node 400 has been adapted in accordance with some example embodiments of the invention. The TAB node 400 contains an antenna 402, -14 -for receiving transmissions, coupled to an antenna switch or duplexer 404 that provides isolation between receive and transmit chains within the TAB node 400. One or more receiver chains, as known in the art, include receiver front-end circuitry 406 (effectively providing reception, filtering and intermediate or base-band frequency conversion). The receiver front-end circuitry 406 is coupled to a signal processing module 408 (generally realized by a digital signal processor (DSP)). A skilled artisan will appreciate that the level of integration of receiver circuits or components may be, in some instances, implementation-dependent.

[0065] The controller 414 maintains overall operational control of the IAB node 400. The controller 414 is also coupled to the receiver front-end circuitry 406 and the signal processing module 408. In some examples, the controller 414 is also coupled to a frequency generation circuit 417 and a memory device 416 that selectively stores operating regimes, such as decoding/encoding functions, synchronization patterns, code sequences, and the like. A timer 418 is operably coupled to the controller 414 to control the timing of operations (e.g. transmission or reception of time-dependent signals) within the TAB node 400.

[0066] As regards the transmit chain, this essentially includes an input module 420, coupled in series through transmitter/modulation circuitry 422 and a power amplifier 424 to the antenna 402, antenna array, or plurality of antennas. The transmitter/ modulation circuitry 422 and the power amplifier 424 are operationally responsive to the controller 414. The signal processor module 408 in the transmit chain may be implemented as distinct from the signal processor in the receive chain. Alternatively, a single processor may be used to implement a processing of both transmit and receive signals, as shown in FIG. 4. Clearly, the various components within the TAB node 400 can be realized in discrete or integrated component form, with an ultimate structure therefore being an application-specific or design selection.

[0067] In accordance with examples of the invention, the processor 408 and transceiver (e.g. transmitter/modulation circuitry 422) of the TAB, when configured as a donor TAB node (such as donor TAB node 222 in FIG. 2) are configured to generate a PRACH offset for broadcasting or routing to its child IAB node(s) and UEs associated with the child IAB node(s). In some examples, the processor 408 and transceiver (e.g. transmitter/modulation circuitry 422) of the TAB, when configured as a child TAB node (such as child TAB node 212 in FIG. 2) are configured to derive a PRACH offset based on its own configuration index obtained from its -15 -parent TAB node. This PRACH offset is then broadcast or routed to UEs associated with the child TAB node(s).

100681 In accordance with some examples of the invention, it is envisaged that the offset configuration may additionally take resource allocation constraint into consideration. For example in this context, the resources that are not available to child links may not be assigned to UE PRACH, because the UE PRACH can only use resources that are available to child links and the aforementioned offset configuration should avoid being used in such situations. Thus, in one example, an initial determination may be made as to whether the resources, e.g. the time slots, available to child links may not be assigned to LIE PRACH, and if they are available to be assigned, then the PRACH offset configuration procedure is adopted, if needed to avoid a conflict.

100691 It has been agreed in RANI of 3GPP for 5G that the resources will be categorized into two types: 1) 'hard' type, where the resource can always be used by child links and 2) 'soft' type, where the resources are not always available to the child links but can be configured to be available to the child links. Thus, in some examples, in one case, it is envisaged that some resources currently available to the child links may be configured to be not available in future and in this case, UE PRACH cannot use such resources.

[0070] In some examples, the range of the offset may be based on the based on maximum configuration index 39. In this context, basically, the offset can be configured from -39 to 39. If this offset is converted to a binary expression, its range can be -64 to 64. It is envisaged that in other examples, the offset range may vary and be more or less than this example. For example, the offset range may be different for the child TAB nodes because of different PRACH configurations. If the periodicity is extended by N times, the range can also be extended as from -N*64 to N*64.

[0071] In some examples, the granularity of the offset may be preset or dynamically changed. For example, the offset may be defined in terms of: a symbol, a slot/mini slot, a sub-frame, a radio frame indicated by system frame number, etc. In this manner, the system can adapt to the prevailing conditions, as it might not be feasible to avoid PRACH overlapping if only one -16 -granularity is used. In this manner, in some examples, the granularity of the offset may be configured in terms of a single resource or across a combination of multiple granularities.

[0072] For TAB node random access, the collision probability is much lower due to a limited number of lAB nodes. Hence, the periodicity of such resources, between successively used RACH slots, can be configured larger.

[0073] FIG. 5 illustrates an orthogonal multiplexing example representation 500, according to examples of the invention. The orthogonal multiplexing example representation 500 employs time multiplexing of access link and backhaul link random access resource allocation using different timeslots. For example, FIG. 5 illustrates a 5G subframe, with slot i 510 and slot i+2 514 and slot i+4 518 allocated for access PRACH 530, with fewer timeslots (e.g. slot i+1 512 and slot i+5 519) allocated for backhaul PRACH 520. As the number of UEs associated with one (parent) TAB node, e.g., is likely to be much larger than the number of IAB nodes, examples of the invention propose that the UE is allocated more of the PRACH opportunities in more frequent timeslots, as compared to RACH allocations for IAB nodes.

[0074] In this example, the same frequency is again used for both backhaul PRACH 520 by the IAB node and access PRACH 530, for example by the donor IAB node 222 or child IAB node 212 or UE node 216 in FIG. 2. As illustrated, in this example, the 'sharing' between access link random access resources 530 and backhaul link random access resources 520 may be limited to allocation of individual time slots for a particular use, such as slot i 510 and slot i+2 514 and slot i+4 518 being allocated for access link random access resources 530. In contrast, slot i+1 512 and slot i+5 519 are allocated for backhaul link random access resources 520, as shown. In this manner, time domain multiplexing can be achieved with no disruption to access PRACH.

[0075] Referring now to FIG. 6, a first example of a simplified flowchart 600 of an lAB node procedure (e.g. a 5G base station (gNB)) is illustrated in accordance with some example embodiments of the invention. The flowchart 600 starts at 602 with the lAB node reading broadcast system information blocks (SIBS) in order to obtain time and frequency location of the PRACH (e.g. PRACH index) information. It will be appreciated that there are many possible -17 -time and frequency locations for PRACH, and in 5G NR each location is associated with a single PRACH index. Therefore, an unique time and frequency location may be derived from the PEACH index. However, indexing those time and frequency locations is only one of the envisaged approaches to locate PEACH, within the context of determining the time and frequency location of PRACH. At 604, the TAB node obtains the PRACH configuration index for the lAB node itself, as well as each of the associated UEs. At 606, the lAB node configures a PRACH offset, if needed. At 608, following a configuration of a PRACH offset (if needed) at 606, the lAB node broadcasts the PEACH configuration index (including the offset, if appropriate) to the associated UEs. Thereafter, at 610, the lAB node performs a RACH operation using the RACH configurations, as and when needed.

100761 Referring now to FIG. 7 a second example of a simplified flowchart 700 of an IAB node procedure (e.g. a 5G base station (gNB)) is illustrated in accordance with some example embodiments of the invention. The flowchart 700 starts at 702 with the TAB node reading broadcast system information blocks (SIBS) in order to obtain time and frequency location of the PEACH (e.g. PEACH index) information. At 704, the TAB node determines whether (or not) a non-overlapping PRCH index has been found. If, at 704, the TAB node has not located a non-overlapping PRACH index, then the TAB node configures a PRACH offset at 706, as described previously. At 708, following a configuration of a PRACH offset at 706 or if the TAB node has located a non-overlapping PRACH index at 704, then the TAB node broadcasts the PRACH index (including the offset, if appropriate) to the UEs. Thereafter, at 710, the TAB node performs a EACH operation using the EACH configurations, as and when needed.

[0077] Referring now to FIG. 8, an example of a simplified flowchart 800 of a remote wireless communication unit operation, when receiving a PEACH configuration from a serving TAB node, is illustrated in accordance with some example embodiments of the invention. In this example, at 802, a remote wireless communication unit (such as TIE C 216 or UE B 206 in FIG. 2, receives broadcast PRACH configuration from TAB node, which includes a PRACH configuration index and offset according to examples of the invention. At 804, the remote -18 -wireless communication unit implements a PRACH operation using the received configuration index and offset.

[0078] Referring now to FIG. 9 a simplified flowchart 900 of a selection or creation of a preamble format by a serving lAB node, and subsequent use by a remote wireless communication unit, is illustrated in accordance with some example embodiments of the invention. At 902, the serving lAB node select from, say a FR2 (e.g. C2 and/or B4) preamble format, or creates a preamble format with an increased number of cyclic prefix samples. At 904, the serving IAB node selects a reduced length preamble to maintain a link budget for the preamble format. At 906 the serving IAB node broadcasts a RACH using the created preamble format to its associated UEs. At 908, one or more of the associated UEs receives and uses the broadcast RACH having the created preamble format with an increased number of cyclic prefix samples and a reduced length preamble to maintain a link budget.

[0079] In particular, it is envisaged that the aforementioned inventive concept can be applied by a semiconductor manufacturer to any integrated circuit comprising a signal processor configured to perform any of the aforementioned operations. Furthermore, the inventive concept can be applied to any circuit that is able to configure, process, encode and/or decode signals for wireless distribution. It is further envisaged that, for example, a semiconductor manufacturer may employ the inventive concept in a design of a stand-alone device, such as a digital signal processor, or application-specific integrated circuit (ASIC) and/or any other sub-system element.

[0080] It will be appreciated that, for clarity purposes, the above description has described embodiments of the invention with reference to different functional units and processors. However, it will be apparent that any suitable distribution of functionality between different functional units or processors, for example with respect to the signal processor may be used without detracting from the invention. For example, functionality illustrated to be performed by separate processors or controllers may be performed by the same processor or controller. Hence, references to specific functional units are only to be seen as references to suitable means for providing the described functionality, rather than indicative of a strict logical or physical structure or organization.

-19 - [0081] Aspects of the invention may be implemented in any suitable form including hardware, software, firmware or any combination of these. The invention may optionally be implemented, at least partly, as computer software running on one or more data processors and or digital signal processors or configurable module components such as FPGA devices. Thus, the elements and components of an embodiment of the invention may be physically, functionally and logically implemented in any suitable way. Indeed, the functionality may be implemented in a single unit, in a plurality of units or as part of other functional units.

[0082] Although the present invention has been described in connection with some embodiments, it is not intended to be limited to the specific form set forth herein. Rather, the scope of the present invention is limited only by the accompanying claims. Additionally, although a feature may appear to be described in connection with particular embodiments, one skilled in the art would recognize that various features of the described embodiments may be combined in accordance with the invention. In the claims, the term 'comprising' does not exclude the presence of other elements or steps.

[0083] Furthermore, although individually listed, a plurality of means, elements or method steps may be implemented by, for example, a single unit or processor. Additionally, although individual features may be included in different claims, these may possibly be advantageously combined, and the inclusion in different claims does not imply that a combination of features is not feasible and/or advantageous. Also, the inclusion of a feature in one category of claims does not imply a limitation to this category, but rather indicates that the feature is equally applicable to other claim categories, as appropriate.

[0084] Thus, communication units such as gNBs functioning as TAB nodes and terminal devices such as UEs, a communication system and methods relating to RACH use for access and backhaul have been described, wherein the aforementioned disadvantages with prior art arrangements have been substantially alleviated.

[0085] In some examples, the aforementioned concepts may be implemented within the system information blocks (SIBS) on 3GPPTM standards. For example, after an initial cell synchronization process is completed, a LIE will read the master information block. Then the UE can read SIB I and SIB2 in order to obtain useful information related to cell access, SIB -20 -scheduling and radio resource configuration. STB2 carries radio resource configuration information including Random Access CHannel (RACH) related parameters that are common for all UEs. In this regards, it is not possible that the IAB node is able to configure two different sets of RACH parameters to both the UE and one or more other IAB nodes, respectively, at the same time.

[0086] The main impacts of this invention on 3GPP standards are on system information.

After initial cell synchronization process is completed, the UE will read the master information block and RMSI to obtain the PRACH configuration. In order to be able to configure offset, the RACH configuration information elements (IEs) in radio resource control (RRC), such as RACH-ConfigGeneric have been expanded, as indicated below. In some examples, PRACH offset may be added to indicate that additional information elements (IEs) or parameters are defined for PRACH offset. In some examples of the invention, three ways are proposed in order to achieve this: (i) define new RRC IEs; and (ii) add new parameters to configure different PRACH settings.

[0087] In order to be able to configure the offset, the RACH configuration IEs in RRC, such as RACH-ConfigGeneric should be expanded. One example of this UE determination is illustrated below, where the new parameters are highlighted in italicised bold. If a different offset value is needed for child IAB nodes, it is envisaged that an additional IE can be added as well.

RA CH-ConfigGeneric information element - ASN1START

- TAG-RACH-CONFIG-GENERIC-START

RACH-ConfigGeneric * := SEQUENCE { prach-ConfigurationIndex INTEGER (0..255), prach-ConfigurationIndex offiet INTEGER (-64..64), -21 -prach-ConfigurationIndex IAB offset INTEGER (-N*64..N*64), msgl-FDM ENUMERATED {one, two, four, eight}, msgl-FrequencyStart INTEGER (0..maxNrofPhysicalResourceBlocks-1), zeroCorrelationZoneConfig INTEGER(0..15), preambleReceivedTargetPower INTEGER (-202..-60) preambleTransMax ENUMERATED {n3, n4, n5, n6, n7, n8, n10, n20, n50, n100, n200}, powerRampingStep ENUMERATED {dB0, dB2, dB4, dB6}, ra-ResponseWindow ENUMERATED f sll, s12, s14, s18, s110, s120, s140, s180},

- TAG-RACH-CONFIG-GENERIC-S TOP

- ASN I STOP

-22 -

Claims (28)

1. Claims: 1. An integrated access and backhaul, TAB, wireless communication system is coupled to a core network, wherein the TAB wireless communication system comprises a first base station, at least one further base station, and a plurality of remote wireless communication units, wherein the plurality of remote wireless communication units obtain access to the core network via at least the first base station, wherein at least one of the following: the first base station, the at least one further base station, comprises: a transceiver; a processor, operably coupled to the transceiver and arranged to: read broadcast system information and obtain therefrom a physical random access channel (PRACH) index; determine whether the time and frequency location of the PRACH for communication with the core network overlaps with an associated remote wireless communication unit PRACH to be used by at least one of the plurality of remote wireless communication units; and, in response thereto, configure and apply a PRACH offset to the time and frequency location of the PRACH.
2. 2. The TAB wireless communication system of Claim 1 wherein the transceiver broadcasts the time and frequency location of the PRACH with the offset to at least one of: at least one the plurality of remote wireless communication units, the at least one further base station.
3. 3. The TAB wireless communication system of Claim I or Claim 2 wherein the processor is configured to apply at least one PRACH offset to the time and frequency location of the PRACH for at least one of: a PRACH access to the core network, a PRACH access to at least one of the plurality of remote wireless communication units.
4. 4. The TAB wireless communication system of Claim 3 wherein the processor is configured to apply the at least one PRACH offset to the time and frequency location of the PRACH that -23 -avoids resource overlap and PRACH conflict between the PRACH access to the core network and the PRACH access by at least one of the plurality of remote wireless communication units.
5. 5. The TAB wireless communication system of Claims 3 or 4 wherein the first base station is configured to perform half-duplex operation for communications with the core network and communications with the at least one of the plurality of remote wireless communication units using the at least one PRACH offset.
6. 6. The TAB wireless communication system of any preceding Claim wherein configuration of the PRACH offset applied to the time and frequency location of the PRACH is derived by the processor of the first base station and applied to the at least one further base station and one or more remote wireless communication units associated with the at least one further base station.
7. 7. The TAB wireless communication system of any preceding Claim wherein configuration of the PRACH offset applied to the time and frequency location of the PRACH is derived from an existing PRACH configuration.
8. 8. The TAB wireless communication system of any preceding Claim wherein the at least one further base station is configured as a relay node that enables wireless remote communication units to obtain access to the core network via at least the second base station to the first base station and thereafter to the core network.
9. 9. The TAB wireless communication system of Claim 8 wherein the at least one further base station is configured to derive a PRACH offset from an existing PRACH configuration based on a configuration index of the at least one further base station obtained from the first base station.
10. 10. The TAB wireless communication system of any preceding Claim wherein the PRACH offset applied to the time and frequency location of the PRACH comprises applying an offset to at least one resource from a group of: a symbol, a slot, a subframe, a system frame number, SFN.
11. -24 - 11. The TAB wireless communication system of Claim 10 wherein a slot range of the PRACH offset is between a first configuration index of -39 and a second configuration index of +39, equating to a first slot binary value of -64 and a second slot binary value of +64.
12. 12. The TAB wireless communication system of Claims 10 or 11 wherein the at least one resource is a fixed single resource.
13. 13. The TAB wireless communication system of any of preceding Claims 10 to 11 wherein the processor configures the at least one resource for a PRACH offset to be applied from a group of resources to increase a granularity of the PRACH offset applied to the time and frequency location of the PRACH.
14. 14. The TAB wireless communication system of any preceding Claim wherein configuration of the PRACH offset applied to the time and frequency location of the PRACH is based on a resource allocation applied to at least one of: the at least one further base station, one or more of the plurality of remote wireless communication units.
15. 15. The TAB wireless communication system of Claim 14 wherein configuration of the PRACH offset applied to the time and frequency location of the PRACH is based on a PRACH that is only assigned to a communication link between a second base station and a third base station of the at least one further base station.
16. 16. The TAB wireless communication system of Claim 15 wherein the PRACH offset applied to the time and frequency location of the PRACH is different between a first PRACH offset applied to associated remote wireless communication units and a second PRACH offset applied to the second base station and the third base station of the at least one further base station.
17. 17. The TAB wireless communication system of any of preceding Claims 14 to 16 wherein the PRACH offset applied to the time and frequency location of the PRACH for one or more of the plurality of remote wireless communication units is additionally based on whether the -25 -resource allocation is to be used for communication access from one or more of the plurality of remote wireless communication units via the at least one further base station.
18. 18. The TAB wireless communication system of any preceding Claim wherein the PRACH offset applied to the time and frequency location of the PRACH is based on a maximum configuration index.
19. 19. The JAB wireless communication system of any preceding Claim wherein the first base station transceiver is configured to transmit system information that includes at least one information element, 1E, configured to support the PRACH offset applied to the time and frequency location of the PRACH.
20. 20. The JAB wireless communication system of Claim 19 wherein at least one PRACH offset applied to the time and frequency location of the PRACH is configured as a RACH information element, 1E, parameter in radio resource control, RRC, state, from a group of multiple sets of RACH parameters.
21. 21. The TAB wireless communication system of Claim 19 or Claim 20 wherein the RACH -FE parameter comprises at least one from a group of: expansion of a RACH-ConfigGenerie field in the system information a definition of a new radio resource control, RRC, 1E; adding of a new parameter to configure different RACH settings; expansion of a value range of current parameters that differentiates between RACH configurations.
22. 22. The JAB wireless communication system of any preceding Claim wherein configuration of the PRACH comprises an orthogonal time multiplexing configuration that includes at least one from a group of: time multiplexing of access link random access resources and backhaul link random access resources within a single time slot, -26 -time multiplexing of access link random access resources and backhaul link random access resources that are allocated different time slots, time multiplexing of access link random access resources, and backhaul link random access resources that are allocated different bandwidth parts, BWP, of a carrier frequency.
23. 23. The JAB wireless communication system of Claim 22 wherein configuration of the PRACH comprises the processor selecting at least one resource parameter to support backhaul RACH resources having longer RACH periodicities than access RACH resources.
24. 24. The 1AB wireless communication system of any preceding Claim wherein configuration of the PRACH comprises a preamble format that supports a largest cell size and associated link budget of the JAB wireless communication system.
25. 25. A base station for an integrated access and backhaul, lAB, wireless communication system coupled to a core network and comprising: at least one further base station, and a plurality of remote wireless communication units, wherein the plurality of remote wireless communication units obtain access to the core network via at least the base station, wherein the base station comprises: a transceiver; a processor, operably coupled to the transceiver and arranged to: read broadcast system information and obtain therefrom a time and frequency location of a physical random access channel (PRACH); determine whether the time and frequency location of the PRACH for communication with the core network overlaps with an associated remote wireless communication unit PRACH to be used by at least one of the remote wireless communication units; and, in response thereto, configure and apply a PRACH offset to the time and frequency location of the PRACH.
26. -27 - 26. A remote wireless communication unit for an integrated access and backhaul, TAB, wireless communication system coupled to a core network and comprising at least one base station, wherein the remote wireless communication unit comprises: a transceiver; a processor, operably coupled to the transceiver and arranged to: receive and read broadcast system information from the at least one base station and obtain therefrom a time and frequency location of a physical random access channel (PRACH) having a PRACH offset; and obtain access to the core network via the at least one base station using the PEACH offset.
27. 27. A method for random access to a core network in an integrated access and backhaul, TAB, wireless communication system that comprises at least one base station, and a plurality of remote wireless communication units, wherein the method performed at the at least one base station comprises: receiving and reading broadcast system information; obtaining from the broadcast system information a time and frequency location of a physical random access channel (PRACH); determining whether the time and frequency location of the PRACH for communication with the core network overlaps with an associated remote wireless communication unit PEACH to be used by at least one of the remote wireless communication units; and, in response thereto, configuring and applying a PRACH offset to the time and frequency location of the PEACH.
28. 28. A method for random access to a core network in an integrated access and backhaul, TAB, wireless communication system that comprises at least one base station, and a plurality of remote wireless communication units, wherein the method performed at a remote wireless communication unit comprises: receiving and reading broadcast system information from the at least one base station; obtaining, from the broadcast system information, a time and frequency location of a physical random access channel (PEACH) having a PEACH offset; and -28 -obtaining access to the core network via the at least one base station using the PRACH offset.-29 -