WO2025201768A1

WO2025201768A1 - Cell search

Info

Publication number: WO2025201768A1
Application number: PCT/EP2025/054846
Authority: WO
Inventors: Karim KASAN; Erika PORTELA LOPES DE ALMEIDA; Nhat-Quang NHAN; Juha Sakari Korhonen
Original assignee: Nokia Technologies Oy
Current assignee: Nokia Technologies Oy
Priority date: 2024-03-28
Filing date: 2025-02-24
Publication date: 2025-10-02
Anticipated expiration: 2026-09-28
Also published as: GB2639963A; GB202404580D0

Abstract

An apparatus comprising means for broadcasting across a limited portion of a duplex band, based on a reserved subset of global synchronization channel numbers, that have been reserved for cells supporting sub-band non-overlapping full duplex communication; and receiving, from a terminal apparatus, a random access message for the sub-band non-overlapping full duplex communication.

Description

TITLE

Cell search

TECHNOLOGICAL FIELD

Examples of the disclosure relate to cell search, and in particular a cell search for a cell supporting sub-band non-overlapping full duplex (SBFD ).

BACKGROUND

In Third Generation Partnership (3GPP) specifications, a user equipment (UE) is required to perform a cell search across frequencies defined by global synchronization channel numbers (GSCN).

The Global Synchronization Channel Number (GSCN) is a frequency-domain parameter that specifies the center frequency for a set of synchronization signal blocks (SSB) within a new radio (NR) band. Each NR band in a network is associated with a range of GSCN values, which indicate the frequency positions (SSREF) of the synchronization signal blocks (SSB).

The concept of GSCN or synchronization raster is employed in 5G NR to efficiently search for the SSB, reducing search time. There is a limited set of possible frequency positions (SSREF ) in each band for SSB. To efficiently search for the SSB, the UE performs sparse and specific searches at these possible frequency positions (SSREF )

The SSB is required for downlink synchronization and for conveying information via a Master Information Block (MIB).

It would be desirable to use sub-band non-overlapping full duplex (SBFD ). In SBFD, the uplink and downlink are simultaneous (share the same time domain resource) and share the same frequency domain resources but do not overlap.

BRIEF SUMMARY

According to various, but not necessarily all, examples there is provided an apparatus comprising means for performing a cell search across a reserved subset of global synchronization channel numbers , the reserved subset being reserved for cells supporting sub-band nonoverlapping full duplex communication; and in dependence upon detecting a cell in the performed cell search, performing a random access procedure with respect to the cell.

In some but not necessarily all examples, the means for performing a cell search across the reserved subset of global synchronization channel numbers comprises: means for attempting to receive a synchronization signal block at the reserved subset of global synchronization channel numbers.

In some but not necessarily all examples, the means for, in dependence upon detecting a cell in the performed cell search, performing a random access procedure with respect to the cell additionally comprises: means for performing, after not detecting a cell in the cell search across the reserved subset of global synchronization channel numbers, a cell search across global synchronization channel numbers other than the reserved subset of global synchronization channel numbers.

In some but not necessarily all examples, the means for enabling a cell search across global synchronization channel numbers other than the reserved subset of global synchronization channel numbers, is configured to: perform the cell search across global synchronization channel numbers other than the reserved subset of global synchronization channel numbers in dependence upon a determination of a run-out of the reserved subset of global synchronization channel numbers.

In some but not necessarily all examples, the means for enabling a cell search across global synchronization channel numbers other than the reserved subset of global synchronization channel numbers, is configured to: perform the cell search across global synchronization channel numbers other than the reserved subset of global synchronization channel numbers in dependence upon a counter configured to count unsuccessful attempts reaches a predetermined value. In some but not necessarily all examples, the counter is configured to increment a number unsuccessful attempts after receiving system information from a cell detected in the cell search, the system indicating no support for the sub-band nonoverlapping full duplex communication. In some but not necessarily all examples, the means for, in dependence upon detecting a cell in the performed cell search, performing a random-access procedure with respect to the cell is configured to perform the random-access procedure with respect to the cell only after receiving system information and validating, on the basis of the received system information that the cell supports the sub-band nonoverlapping full duplex communication.

In some but not necessarily all examples, the apparatus comprises means for using means other than the system information to validate that the cell supports sub-band non-overlapping full duplex communication.

In some but not necessarily all examples, the apparatus comprises means for using means other than the system information to validate resources for initial random access with respect to the cell.

In some but not necessarily all examples, the means for, in dependence upon detecting a cell in the performed cell search, performing a random-access procedure with respect to the cell is configured to: validate, without system information only based on detecting the cell in the reserved subset of global synchronization channel numbers, that the cell supports the subband non-overlapping full duplex communication.

In some but not necessarily all examples, the reserved subset of global synchronization channel numbers is hardcoded to a memory of the apparatus.

In some but not necessarily all examples, the reserved subset of global synchronization channel numbers is predetermined via specification in a telecommunication standard.

In some but not necessarily all examples, the means for, in dependence upon detecting a cell in the performed cell search, performing a random-access procedure with respect to the cell comprises: means for selecting a best candidate cell in dependence upon cell indications of support for sub-band non-overlapping full duplex communication via cell broadcast using the reserved subset of global synchronization channel numbers of a synchronization signal block.

In some but not necessarily all examples, the means for, in dependence upon detecting a cell in the performed cell search, performing a random-access procedure with respect to the cell comprises: means for performing initial random access comprising transmitting a preamble for the cell via a physical random-access channel on an initial random access channel occasion associated with a synchronization signal block, received from the cell, during the cell search across the reserved subset of global synchronization channel numbers, the reserved subset being reserved for cells supporting sub-band nonoverlapping full duplex communication.

In some but not necessarily all examples, the means for, in dependence upon detecting a cell in the performed cell search, performing a random-access procedure with respect to the cell comprises: means for transmitting a preamble for the cell via physical random-access channel on a random-access channel occasion that is within an uplink sub-band of a slot shared for simultaneous uplink and downlink in a duplex band.

According to various, but not necessarily all, examples there is provided a method comprising: performing a cell search across a reserved subset of global synchronization channel numbers, the reserved subset being reserved for cells supporting sub-band nonoverlapping full duplex communication; and in dependence upon detecting a cell in the performed cell search, performing a random access procedure with respect to the cell.

According to various, but not necessarily all, examples there is provided a computer program comprising instructions that when executed by one or more processors enables an apparatus to: perform a cell search across a reserved subset of global synchronization channel numbers, the reserved subset being reserved for cells supporting sub-band nonoverlapping full duplex communication; and in dependence upon detecting a cell in the performed cell search, perform a random access procedure with respect to the cell.

According to various, but not necessarily all, examples there is provided a (network) apparatus comprising means for: broadcasting across a limited portion of a duplex band, based on a reserved subset of global synchronization channel numbers, that have been reserved for cells supporting sub-band non-overlapping full duplex communication; and receiving, from a terminal apparatus, a random access message for the sub-band non-overlapping full duplex communication.

In some but not necessarily all examples, the means for broadcasting across a limited portion of a duplex band, based on a reserved subset of global synchronization channel numbers, comprises: means for broadcasting a synchronization signal block at frequencies based on the reserved subset of global synchronization channel numbers to indicate that the apparatus supports sub-band non-overlapping full duplex communication.

In some but not necessarily all examples, the (network) apparatus comprises means enabling initial random access comprising receiving a preamble for the cell via physical random-access channel on an initial random access channel occasion associated with a timing of a synchronization signal block, transmitted by the apparatus,

In some but not necessarily all examples, the (network) apparatus comprises means for receiving a preamble for the cell via a physical random-access channel on an initial random access channel occasion that is shared for simultaneous uplink and downlink in a band.

In some but not necessarily all examples, the (network) apparatus comprises means for transmitting in system information validation that the apparatus supports sub-band non-overlapping full duplex communication (SBFD).

In some but not necessarily all examples, the (network) apparatus comprises means for transmitting in system information validation of resources for initial random access with respect to the apparatus using SBFD.

In some but not necessarily all examples, the (network) apparatus comprises means for transmitting in CORESETO or DCI_0 validation that the apparatus supports subband non-overlapping full duplex communication (SBFD).

In some but not necessarily all examples, the (network) apparatus comprises means for transmitting in CORESETO or DCI_0 validation of resources for initial random access with respect to the apparatus using SBFD. In some but not necessarily all examples, the reserved subset of global synchronization channel numbers is predetermined via specification in a telecommunication standard.

According to various, but not necessarily all, examples there is provided a method comprising: broadcasting across a limited portion of a duplex band, based on a reserved subset of global synchronization channel numbers, that have been reserved for indicating that a cell supports sub-band non-overlapping full duplex communication to indicate that the apparatus supports sub-band non-overlapping full duplex communication.

According to various, but not necessarily all, examples there is provided a computer program comprising instructions that when executed by one or more processors enables an apparatus to: broadcast across a limited portion of a duplex band, based on a reserved subset of global synchronization channel numbers, that have been reserved for indicating that a cell supports sub-band non-overlapping full duplex communication to indicate that the apparatus supports sub-band non-overlapping full duplex communication.

According to various, but not necessarily all, embodiments there is provided examples as claimed in the appended claims.

While the above examples of the disclosure and optional features are described separately, it is to be understood that their provision in all possible combinations and permutations is contained within the disclosure. It is to be understood that various examples of the disclosure can comprise any or all the features described in respect of other examples of the disclosure, and vice versa. Also, it is to be appreciated that any one or more or all the features, in any combination, may be implemented by/comprised in/performable by an apparatus, a method, and/or computer program instructions as desired, and as appropriate. The description of a function should additionally be considered to also disclose any means suitable for performing that function BRIEF DESCRIPTION

Some examples will now be described with reference to the accompanying drawings in which:

FIG. 1 shows an example of the subject matter described herein;

FIGs. 2A, 2B, 2C, 2D show examples of the subject matter described herein;

FIG. 3 shows another example of the subject matter described herein;

FIG. 4A shows another example of the subject matter described herein;

FIG. 4B shows another example of the subject matter described herein;

FIG. 5 shows another example of the subject matter described herein;

FIG. 6 shows another example of the subject matter described herein;

FIG. 7 shows another example of the subject matter described herein;

FIG. 8 shows another example of the subject matter described herein; and FIG. 9 shows another example of the subject matter described herein.

The figures are not necessarily to scale. Certain features and views of the figures can be shown schematically or exaggerated in scale in the interest of clarity and conciseness. For example, the dimensions of some elements in the figures can be exaggerated relative to other elements to aid explication. Similar reference numerals are used in the figures to designate similar features. For clarity, all reference numerals are not necessarily displayed in all figures.

DETAILED DESCRIPTION

Fig. 1 illustrates an example of a network 100 comprising a plurality of network entities including terminal apparatus 110, node apparatus 120 and one or more network apparatus 130. The terminal apparatus 110 and node apparatus 120 communicate 124 with each other. The one or more network apparatus 130 communicate 128 with the node apparatus 120.

In some examples the one or more network apparatus 130 communicate with the terminal apparatus 110. The one or more network apparatus 130 can, in some examples, communicate with each other. The one or more node apparatus 120 can, in some examples, communicate 126 with each other. The network 100 can be a cellular network comprising a plurality of cells 122 each served by a node apparatus 120. In this example, the interface between the terminal apparatus 110 and a node apparatus 120 defining a cell 122 is a wireless interface 124.

The node apparatus 120 comprises one or more cellular radio transceivers. The terminal apparatus 110 comprises one or more cellular radio transceivers.

In the example illustrated the cellular network 100 is a third generation Partnership Project (3GPP) network in which the terminal apparatus 110 are user equipment (UE) and the node apparatus 120 can be access nodes such as base stations.

A user equipment comprises a mobile equipment. Where reference is made to user equipment that reference includes and encompasses, wherever possible, a reference to mobile equipment.

In some examples, during operation, a user equipment 110 comprises a mobile equipment comprising a smart card for authentication/encryption etc. such as a Subscriber Identity Module (SIM). In some examples, during operation, a user equipment 110 comprises mobile equipment comprising circuitry embedded as part of the user equipment 110 for authentication/ encryption such as software SIM.

The node apparatus 120 can be any suitable access node such as a base station or transmission reception point. The node apparatus 120 can be a network element responsible for radio transmission and reception in one or more cells 122, to or from the UE 110. The node apparatus 120 can be a network element in a Radio Access Network (RAN), an Open-Radio Access Network (O-RAN) or any other suitable type of network.

The network apparatus 130 can be part of a core network. The network apparatus 130 can be configured to manage functions relating to connectivity for the UEs 110. For example, the network apparatus 130 can be configured to manage functions such as connectivity, mobility, authentication, authorization and/or other suitable functions. In some examples the network apparatus 130 can comprise an Access and Mobility management Function (AMF) and/or a User Plane Function (UPF) or any other suitable entities.

In the example of Fig. 1 the network apparatus 130 is shown as a single entity. In some examples the network apparatus 130 could be distributed across a plurality of entities. For example, the network apparatus 130 could be cloud based or distributed in any other suitable manner. The network apparatus 130 can be a core network node.

The network 100 can be a 4G or 5G network, for example. It can for example be a New Radio (NR) network that uses gNB or eNB as access nodes 120. New Radio is the 3GPP name for 5G technology. In such cases the node apparatus 120 can comprise gNodeBs (gNBs) 120 configured to provide user plane and control plane protocol terminations towards the UE 110 and/or to perform any other suitable functions. The gNBs 120 are interconnected with each other by means of an X2/Xn interface 126. The gNBs are also connected by means of the N2 interface 128 to the network apparatus 130. The gNBs can be connected to an AMF or any other suitable network apparatus 130. Other types of networks and interfaces could be used in other examples. Other types of network could comprise next generation mobile and communication network, for example, a 6G network.

FIG 2A illustrates Frequency Division Duplex (FDD). The uplink and downlink are simultaneous (share the same time domain resource 2) and are separated in the frequency domain (use separated frequencydomain resources 4A, 4B) .

FIG 2B illustrates Time Division Duplex (TDD). The uplink and downlink are not simultaneous (use separated time domain resources 2A, 2B ) and share the same frequency domain resources 4.

FIG 2C illustrates an example of sub-band non-overlapping full duplex (SBFD ). The uplink and downlink are simultaneous (share the same time domain resource 2) and share the same frequency domain resource 4 but not overlap.

Sub-band non-overlapping full duplex (SBFD ) describes simultaneous DL and UL on different physical resource blocks (PRBs)/sub-bands within a spectrum supporting sub-band full duplex communication (e.g. unpaired TDD spectrum). A sub-band is simultaneous, contiguous PRBs within a band.

A SBFD slot 6, is a slot during which the non-overlapping downlink (DL) sub-bands and uplink (UL) sub-band(s) both exist simultaneously in different PRBs.

A non-SBFD slot, is a slot during which the entire band is used for either DL or UL (i.e., legacy/full DL/UL slots).

The sub-band non-overlapping full duplex (SBFD ) can also be referred to as crossdivision duplexing (xDD) or Flexible Duplexing (FDU).

FIG 2D illustrates an example of SBFD using guard bands in frequency domain and/or time domain.

A guard band within the sub-band separates simultaneous UL PRBs from DL PRBs in the same band. A guard band can provide separation in the time domain (for a limited frequency range) and separation in the frequency domain (for a limited time duration).

The following FIGs describe examples of an apparatus comprising means for performing a cell search across a reserved subset of global synchronization channel numbers (GSCN) channel numbers, the reserved subset being reserved for cells supporting sub-band non-overlapping full duplex communication; and in dependence upon detecting a cell in the performed cell search, performing a random access procedure with respect to the cell.

In at least some examples, being reserved may be understood as a system-specific limitation that only the cells supporting the SBFD communication are able to use the reserved set of GSCN channel numbers. Cells not supporting the SBFD communication may be bound to use other GSCN channel numbers. In this way, mere detection of a cell in the cell search across the reserved subset of GSCN channel numbers is an indication to the apparatus that the detected cell supports the SBFD communication. In at least some examples, being reserved may be understood as a system-specific limitation that cells supporting the SBFD communication must use the reserved set of GSCN channel numbers to indicate their capability. In this way, detection of a cell in the cell search across the reserved subset of GSCN channel numbers is indicative but not determinative that the detected cell supports the SBFD communication.

In at least some examples, the apparatus is a user equipment (UE) 110 for NR. In NR, when the UE 110 is in Radio Resource Control (RRC) Idle mode, the UE performs a cell search 200 across specific frequencies defined by global synchronization channel numbers (GSCN). Rather than use the full range of GSCN, only a reserved subset of GSCN (and a consequential reserved subset of search frequencies) are used. The reserved subset is reserved for cells supporting sub-band non-overlapping full duplex (SBFD) communication.

The concept of GSCN or synchronization raster is employed in 5G NR to efficiently search for the SSB, reducing search time. There is a limited set of possible frequency positions (SSREF ) in each band for SSB. To efficiently search for the SSB, the UE performs sparse and specific searches at these possible frequency positions (SSREF).

The SSB contain the primary and secondary synchronization signals and the physical broadcast channel (PBCH), which are used by a UE 110 to acquire downlink time and frequency synchronization with the cell and to obtain basic system information.

A sub-set of frequencies (GSCN) are reserved for SBFD-capable gNB(s) to implicitly indicate support for SBFD, by sending SSB at frequency positions indicated by the sub-set of reserved GSCN. The UE will have a prior knowledge about whether a gNB would potentially support SBFD or not by determining whether the SSB received at the UE was sent in the sub-set of frequency positions associated with the sub-set of reserved GSCN.

During initial random access, the UE sends a specific preamble to the gNB via physical random-access channel (PRACH) using a specific time-frequency resource called RACH occasion (RO). Contention based random access (CBRA) procedures are supported, including 4-step RACH (Rel-15) and 2-step RACH (Rel-16).

FIG 3 illustrates a user equipment 120 comprising means for performing a cell search 200 across a reserved subset of global synchronization channel numbers (GSCN) channel numbers, the reserved subset being reserved for cells supporting sub-band non-overlapping full duplex communication; and in dependence upon detecting a cell in the performed cell search, performing a random access procedure 210 with respect to the cell.

FIGs 4A and 4B illustrate an example of an apparatus, for example a UE 110, where the means for performing a cell search 200 across the reserved subset of global synchronization channel numbers comprises: means for attempting to receive a synchronization signal block (SSB) 201 at the reserved subset of global synchronization channel numbers.

Attempting to receive a synchronization signal block (SSB) 201 at the reserved subset of global synchronization channel numbers means attempting to receive a synchronization signal block (SSB) 201 at the reserved subset of frequencies indicated by the reserved subset of global synchronization channel numbers.

The UE 110 may be configured to start the cell search from the reserved subset of frequencies to search for a cell supporting the SBFD communication.

FIG 4A illustrates an example of an apparatus, for example a UE 110, configured to perform the random-access procedure 200 after receiving system information.

The means for, in dependence upon detecting a cell in the performed cell search, performing a random-access procedure 210 with respect to the cell is configured to perform the random-access procedure 210 with respect to the cell after receiving system information.

In at least some examples, the apparatus 120 is configured to use the system information to validate that the cell supports sub-band non-overlapping full duplex communication (SBFD). In this embodiment, the apparatus may require such validation before proceeding with the random access procedure 210. In other words, mere detection of the cell within the reserved subset of frequencies is not sufficient to verify the SBFD operation.

In at least some examples, the apparatus 120 is configured to use the system information to validate resources for the initial random access procedure 210 with respect to the cell. An example of the resources is a time-frequency resource of a random access channel (RACH) occasion.

In the example, the UE 110 measures SSB 201 to select the best SSB and reads the physical broadcast channel (PBCH) to obtain Master Information Block (MIB). The MIB contains information about the physical downlink control channel (PDCCH) with CORESET 0. CORESET 0 is an initial control resource set. Using the MIB, the UE 110 locates the CORESETO and receives the downlink control information (DCI) 203, which schedules the first system information block (SIBI).The UE 110 receives SIB1 205.

SIB1 contains the Serving Cell Configuration, which contains the Random Access Channel (RACH) configuration used for the Initial Random Access procedure 210. After receiving the SIB1 205, the UE 110 can use the RACH configuration to perform the initial random access procedure 210.

As illustrated in FIG 5, to start the Random Access procedure 210, the UE 110 sends a PRACH preamble 211 in the RACH Occasion (RO) 212 corresponding to the SSB 201 , and according to the RACH configuration.

The SIB 1 can explicitly or implicitly indicate (validate) that the cell supports sub-band non-overlapping full duplex communication (SBFD)._The SIB 1 can explicitly or implicitly indicate (validate) resources for initial random access with respect to the cell.

The UE has two indications that the cell supports SBFD. First, finding an SSB on the unique reserved subset of GSCN, reserved for SBFD indication. Second, from the indication provided by SIB1.

The UE 110 is thus certain that the cell supports SBFD operation. However, reception of SIB1 is required. If SIB1 is augmented to explicitly indicate (validate) that the cell supports sub-band non-overlapping full duplex communication (SBFD) and/or indicate (validate) resources for initial random access with respect to the cell then this potentially creates overhead for all UEs.

In some examples, the UE may validate SBFD availability by means other than SIB1

In at least some example, the apparatus is configured to use means other than the system information, for example, SIB1, to validate that the cell supports sub-band non-overlapping full duplex communication. In at least some examples, the apparatus is configured to use means other than the system information to validate resources for initial random access with respect to the cell.

In some examples, the UE 110 obtains implicit indication(s) (not in the SIB1), that validate UL SBFD availability and/or validates UL SBFD PRBs for initial random access (e.g. the ROs 212).

In this alternative the SBFD configuration could be hardcoded for the UEs or could be implicitly obtained from the legacy SIB1 or from the RACH configuration.

In some examples, the SBFD configuration is implicitly provided by the RACH configuration. In some examples, the ROs 212 for the PRACH preamble 211 of the random access procedure is configured by a new RACH configuration or an existing RACH configuration. CORESETO and/or DCI can be used to provide an implicit/expl icit indication of SBFD support or additional evidence of SBFD support

In some examples, CORESETO from the pdcch-ConfigSIB1 in the MIB can be used. The ConfigSIBI can have a number up to 255 and a reserved number can be used as an implicit indication.

In some examples, the DCI 1_0, comprises one or more fields that can be used to provide implicit indication. Examples of suitable fields include but are not necessarily limited to frequency domain resource assignment (FDRA), time domain resource assignment (TDRA) and the modulation and coding scheme (MCS).

FIG 4B illustrates an example of an apparatus, for example a UE 110, configured to perform the random-access procedure 200 before receiving system information.

The means for, in dependence upon detecting a cell in the performed cell search 200, performing a random-access procedure 210 with respect to the cell is configured to perform the random-access procedure with respect to the cell before receiving system information (not illustrated in FIG 4B, but illustrated in FIG 4A).

In at least some examples, the UE 110 does not require to receive system information to validate that the cell supports sub-band non-overlapping full duplex communication (SBFD). The UE 110 can, for example, assume validity based on detecting a cell within the reserved subset of frequencies.

Finding an SSB on the unique GSCN indexes will be the trigger to validate the ROs 212 for SBFD operation and proceed to the initial random access procedure 210

FIG 5 illustrates some details on an initial random access procedure. Contention based random access (CBRA) procedures are supported, including 4-step RACH using Msg1 (e.g. message 211), Msg 2 (e.g. message 213), Msg 3 (e.g. message 215), Msg 4 (e.g. message 217) and 2-step RACH using MsgA (e.g. message 211) and MsgB (e.g. message 213). In both procedures the initial message 211 (Msg 1 or MsgA) comprises a PRACH preamble sent using the RACH Occasion (RO) 212. The user equipment 110 comprises means for, in dependence upon detecting a cell in the performed cell search 200, performing a random-access procedure 210 with respect to the cell comprising: means for selecting a best candidate cell in dependence upon cell indications of support for sub-band non-overlapping full duplex communication via cell broadcast using the reserved subset of global synchronization channel numbers of a synchronization signal block (SSB).

The means for performing initial random access comprises means for transmitting a preamble 211 for the cell via a physical random-access channel on an initial random access channel occasion 212 associated with a synchronization signal block 201 (illustrated in FIGs 4A, 4B), received from the cell, during the cell search 200 (illustrated in FIGs 4A, 4B), across the reserved subset of global synchronization channel numbers, the reserved subset being reserved for cells supporting sub-band non-overlapping full duplex communication.

In at least some examples, the UE 110 is configured to transmit the preamble 211 for the cell via physical random-access channel on a random-access channel occasion 212 that is within an uplink sub-band of a slot shared for simultaneous uplink and downlink in a duplex band i.e. in a UL SBFD slot 6.

FIG 6 illustrates an example of a cell search 200. For example, cell search 200 performed by a UE 110 as illustrated and described with reference to FIG 4A. FIG 7 illustrates an example of a cell search 200. For example, cell search 200 performed by a UE 110 as illustrated and described with reference to FIG 4B.

The cell search 200 is across a reserved subset of global synchronization channel numbers (GSCN) channel numbers, the reserved subset being reserved for cells supporting sub-band non-overlapping full duplex communication.

In dependence upon detecting a SBFD cell in the performed cell search, a random access procedure 210 with respect to the SBFD cell is performed, for example as described with reference to FIG 5. If a SBFD cell is not detected, then a non-SBFD search 312 is performed for a non- SBFD cell. The non-SBFD search is a search across global synchronization channel numbers other than the reserved subset of global synchronization channel numbers.

In these examples, non-SBFD search 312 is performed in dependence upon a determination 330 of a run-out of the reserved subset of global synchronization channel numbers. That is all of the reserved subset of global synchronization channel numbers have been exhausted.

In both FIGs, the cell search starts at block 302. The first GSCN of the reserved subset of GSCN is selected 304. It is determined 306 whether or not a SSB 201 is found at the frequency indicated by the selected GSCN. If a reserved SSB is detected at the reserved frequency indicated by the selected reserved GSCN, then the method branches towards initial access procedure 210 for a cell supporting SBFD. If a reserved SSB is not detected at the reserved frequency indicated by the selected reserved GSCN, then the method branches towards block 330.

At block 330, if the current selected GSCN is the last one of the reserved subset of GSCN (run-out) then the method branches towards non-SBFD search 312. The non- SBFD search is a search across global synchronization channel numbers other than the reserved subset of GSCN.

If the current selected GSCN is not the last one of the reserved subset of GSCN then the current selected GSCN is dropped 333 and a next GSCN is selected from the sub-set of reserved GSCN. In this way each GSCN in the sub-set of reserved GSCN is selected once at block 304.

In FIG 7, if a reserved SSB is detected 306 at the reserved frequency indicated by the selected reserved GSCN, then the method assumes 340 that the cell is a whether valid SBFD cell and moves to the initial access procedure 210 for a cell supporting SBFD. In FIG 6, if a reserved SSB is detected 306 at the reserved frequency indicated by the selected reserved GSCN, then the method uses a test criteria 308 to test whether the cell is a valid SBFD cell.

One example of a test criteria has been described with reference to FIG 4A. For example, a received SIB1 can be used to implicitly or explicitly validate that the cell supports SBFD.

If it is validated using the test criteria that the cell supports SBFD, then the method moves to the initial access procedure 210 for a cell supporting SBFD.

If it is not validated using the test criteria that the cell supports SBFD, then the method moves towards block 330.

In the example illustrated, there is an option for the method to branch towards non- SBFD search 312 after a certain number of failed validations 308.

The UE 110 enable the non SBFD search (the cell search across global synchronization channel numbers other than the reserved subset of global synchronization channel numbers) in dependence upon a counter 322 configured to count unsuccessful attempts to pursue initial random access 310 for an SBFD cell. The counter 322 is configured to count, after receiving system information, unsuccessful attempts to pursue initial random access performed in dependence upon detecting 306 a cell in cell searches across the reserved subset of global synchronization channel numbers.

In FIG 6, if it is not validated using the test criteria 308 that the cell supports SBFD, then the method moves to block 320.

If the current counter value is greater than a maximum value, the method resets 324 the counter value to zero and the method moves to non-SBFD search 312.

If the current counter value is not greater than a maximum value, the method counter 322 increments by and the method moves to block 330. The counter 322 therefore counts the number of failed validations 308 and branches to non-SBFD search 312 after a programmable number of failed validations 308.

Reference will be made later to a memory 404 of the apparatus, for example, the UE 110. This memory or another memory can be used to permanently store (hardcode) the reserved subset of global synchronization channel numbers.

In some examples permanent read-only memory is used to permanently store reserved subset of global synchronization channel numbers. Any of the preceding examples can use such hardcoded GSCN.

The reserved subset of global synchronization channel numbers can be predetermined via specification in a telecommunication standard.

The preceding description has concentrated on describing features from the perspective of the UE 110. However, the network, for example the access node 120, also needs to cooperate.

In some examples, a network apparatus, for example a base station 120, comprises means for broadcasting across a limited portion of a duplex band, based on a reserved subset of global synchronization channel numbers that have been reserved for indicating that a cell supports sub-band non-overlapping full duplex communication, to indicate that the apparatus supports sub-band non-overlapping full duplex communication.

The base station 120 broadcasts SSB 201 across a limited portion of a duplex band (reserved frequencies), based on a reserved subset of global synchronization channel numbers. This indicates that the base station supports sub-band nonoverlapping full duplex (SBFD) communication. The reserved subset of global synchronization channel numbers are reserved for indicating that a cell supports subband non-overlapping full duplex communication.

Synchronization signal blocks (SSB) are broadcast at frequencies based on the reserved subset of global synchronization channel numbers to indicate that the apparatus supports sub-band non-overlapping full duplex communication. This are reserved SSB.

In at least some examples, the base station 120 is configured to enable initial random access comprising receiving a preamble for the cell via physical random-access channel on an initial random access channel occasion associated with a timing of the reserved SSB, transmitted by the apparatus,

In at least some examples, the base station 120 is configured to received the preamble for the cell via a physical random-access channel on an initial random access channel occasion that is shared for simultaneous uplink and downlink in a band (e.g. during an SFBD slot).

In at least some examples, the base station 120 is configured to transmit in system information validation that the base station 120 supports sub-band non-overlapping full duplex communication (SBFD).

In at least some examples, the base station 120 is configured to transmit in system information validation of resources for initial random access with respect to the base station 120.

Fig 8 illustrates an example of a controller 400 suitable for use in an apparatus. In some examples, the apparatus is part of a user equipment 110. In some examples, the apparatus is part of a base station 120.

Implementation of a controller 400 may be as controller circuitry. The controller 400 may be implemented in hardware alone, have certain aspects in software including firmware alone or can be a combination of hardware and software (including firmware).

As illustrated in Fig 8 the controller 400 may be implemented using instructions that enable hardware functionality, for example, by using executable instructions 406 in a general-purpose or special-purpose processor 402 that may be stored on a machine readable storage medium (disk, memory etc.) to be executed by such a processor 402.

The processor 402 is configured to read from and write to the memory 404. The processor 402 may also comprise an output interface via which data and/or commands are output by the processor 402 and an input interface via which data and/or commands are input to the processor 402.

The memory 404 stores instructions, program, or code 406 that controls the operation of the apparatus when loaded into the processor 402. The computer program instructions, program or code am 406, provide the logic and routines that enables the apparatus to perform the methods illustrated in the accompanying FIGs. The processor 402 by reading the memory 404 is configured to load and execute the instructions, program, or code 406.

In some examples, the apparatus 110 comprises: at least one processor 402; and at least one memory 404 storing instructions that, when executed by the at least one processor 402, cause the apparatus at least to: performing a cell search across a reserved subset of global synchronization channel numbers, the reserved subset being reserved for cells supporting sub-band nonoverlapping full duplex communication; and in dependence upon detecting a cell in the performed cell search, performing a random access procedure with respect to the cell.

In some examples, the apparatus 120 comprises: at least one processor 402; and at least one memory 404 storing instructions that, when executed by the at least one processor 402, cause the apparatus at least to: broadcasting across a limited portion of a duplex band, based on a reserved subset of global synchronization channel numbers, that have been reserved for indicating that a cell supports sub-band non-overlapping full duplex communication to indicate that the apparatus supports sub-band non-overlapping full duplex communication. As illustrated in Fig 9, the instructions, program, or code 406 may arrive at the apparatus via any suitable delivery mechanism 408. The delivery mechanism 408 may be, for example, a machine readable medium, a computer-readable medium, a non-transitory computer-readable storage medium, a computer program product, a memory device, a record medium such as a Compact Disc Read-Only Memory (CD- ROM) or a Digital Versatile Disc (DVD) or a solid-state memory, an article of manufacture that comprises or tangibly embodies the computer program 406. The delivery mechanism may be a signal configured to reliably transfer the computer program 406. The apparatus may propagate or transmit the computer program 406 as a computer data signal.

The 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., RAM vs. ROM).

In some examples the computer program 406 comprises computer program instructions for causing an apparatus 110 to perform at least the following or for performing at least the following: perform a cell search across a reserved subset of global synchronization channel numbers, the reserved subset being reserved for cells supporting sub-band nonoverlapping full duplex communication; and in dependence upon detecting a cell in the performed cell search, perform a random access procedure with respect to the cell.

In some examples the computer program 406 comprises computer program instructions for causing an apparatus 120 to perform at least the following or for performing at least the following: broadcast across a limited portion of a duplex band, based on a reserved subset of global synchronization channel numbers, that have been reserved for indicating that a cell supports sub-band non-overlapping full duplex communication to indicate that the apparatus supports sub-band non-overlapping full duplex communication. Computer program instructions may be comprised in a computer program, a non- transitory computer readable medium, a computer program product, a machine readable medium. In some but not necessarily all examples, the computer program instructions may be distributed over more than one computer program.

Although the memory 404 is illustrated as a single component/circuitry it may be implemented as one or more separate components/circuitry some or all of which may be integrated/removable and/or may provide permanent/semi-permanent/ dynamic/cached storage.

Although the processor 402 is illustrated as a single component/circuitry it may be implemented as one or more separate components/circuitry some or all of which may be integrated/removable. The processor 402 may be a single core or multi-core processor.

References to ‘computer-readable storage medium’, ‘computer program product’, ‘tangibly embodied computer program’ etc. or a ‘controller’, ‘computer’, ‘processor’ etc. should be understood to encompass not only computers having different architectures such as single /multi- processor architectures and sequential (Von Neumann)/parallel architectures but also specialized circuits such as field- programmable gate arrays (FPGA), application specific circuits (ASIC), signal processing devices and other processing circuitry. References to computer program, instructions, code etc. should be understood to encompass software for a programmable processor or firmware such as, for example, the programmable content of a hardware device whether instructions for a processor, or configuration settings for a fixed-function device, gate array or programmable logic device etc.

As used in this application, the term ‘circuitry’ may refer to one or more or all the following:

(a) hardware-only circuitry 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 any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory or memories that work together to cause an apparatus, such as a mobile phone or server, 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 (for example, 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 and its (or their) accompanying software and/or firmware. The term circuitry also covers, for example and if applicable to the claim element, a baseband integrated circuit for a mobile device or a similar integrated circuit in a server, a cellular network device, or other computing or network device.

The blocks illustrated in the accompanying Figs may represent steps in a method and/or sections of code in the computer program 406. The illustration of a particular order to the blocks does not necessarily imply that there is a required or preferred order for the blocks and the order and arrangement of the block may be varied. Furthermore, it may be possible for some blocks to be omitted.

As used here ‘module’ refers to a unit or apparatus that excludes certain parts/components that would be added by an end manufacturer or a user. The apparatus can, for example be a module. A controller 400 of the apparatus can, for example be a module.

Where a structural feature has been described, it may be replaced by means for performing one or more of the functions of the structural feature whether that function or those functions are explicitly or implicitly described.

The above-described examples find application as enabling components of: automotive systems; telecommunication systems; electronic systems including consumer electronic products; distributed computing systems; media systems for generating or rendering media content including audio, visual and audio visual content and mixed, mediated, virtual and/or augmented reality; personal systems including personal health systems or personal fitness systems; navigation systems; user interfaces also known as human machine interfaces; networks including cellular, non-cellular, and optical networks; ad-hoc networks; the internet; the internet of things; virtualized networks; and related software and services.

The apparatus can be provided in an electronic device, for example, a mobile terminal, according to an example of the present disclosure. It should be understood, however, that a mobile terminal is merely illustrative of an electronic device that would benefit from examples of implementations of the present disclosure and, therefore, should not be taken to limit the scope of the present disclosure to the same. While in certain implementation examples, the apparatus can be provided in a mobile terminal, other types of electronic devices, such as, but not limited to: mobile communication devices, hand portable electronic devices, wearable computing devices, portable digital assistants (PDAs), pagers, mobile computers, desktop computers, televisions, gaming devices, laptop computers, cameras, video recorders, GPS devices and other types of electronic systems, can readily employ examples of the present disclosure. Furthermore, devices can readily employ examples of the present disclosure regardless of their intent to provide mobility.

The term ‘comprise’ is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising Y indicates that X may comprise only one Y or may comprise more than one Y. If it is intended to use ‘comprise’ with an exclusive meaning then it will be made clear in the context by referring to ‘comprising only one...’ or by using ‘consisting.’

In this description, the wording ‘connect’, ‘couple’ and ‘communication’ and their derivatives mean operationally connected/coupled/in communication. It should be appreciated that any number or combination of intervening components can exist (including no intervening components), i.e. , to provide direct or indirect connection/coupling/communication. Any such intervening components can include hardware and/or software components.

As used herein, the term "determine/determining" (and grammatical variants thereof) can include, not least: calculating, computing, processing, deriving, measuring, investigating, identifying, looking up (for example, looking up in a table, a database, or another data structure), ascertaining and the like. Also, "determining" can include receiving (for example, receiving information), accessing (for example, accessing data in a memory), obtaining and the like. Also, " determine/determining" can include resolving, selecting, choosing, establishing, and the like.

In this description, reference has been made to various examples. The description of features or functions in relation to an example indicates that those features or functions are present in that example. The use of the term ‘example’ or ‘for example’ or ‘can’ or ‘may’ in the text denotes, whether explicitly stated or not, that such features or functions are present in at least the described example, whether described as an example or not, and that they can be, but are not necessarily, present in some of or all other examples. Thus ‘example’, ‘for example’, ‘can’, or ‘may’ refers to a particular instance in a class of examples. A property of the instance can be a property of only that instance or a property of the class or a property of a sub-class of the class that includes some but not all the instances in the class. It is therefore implicitly disclosed that a feature described with reference to one example but not with reference to another example, can where possible be used in that other example as part of a working combination but does not necessarily have to be used in that other example.

As used herein, “at least one of the following: ” and “at least one of ” and similar wording, where the list of two or more elements are joined by “and” or “or” mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements.

Although examples have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the claims.

Features described in the preceding description may be used in combinations other than the combinations explicitly described above.

Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not. The description of a feature, such as an apparatus or a component of an apparatus, configured to perform a function, or for performing a function, should additionally be considered to also disclose a method of performing that function. For example, description of an apparatus configured to perform one or more actions, or for performing one or more actions, should additionally be considered to disclose a method of performing those one or more actions with or without the apparatus.

Although features have been described with reference to certain examples, those features may also be present in other examples whether described or not.

The term ‘a’, ‘an’ or ‘the’ is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising a/an/the Y indicates that X may comprise only one Y or may comprise more than one Y unless the context clearly indicates the contrary. If it is intended to use ‘a’, ‘an’ or ‘the’ with an exclusive meaning then it will be made clear in the context. In some circumstances the use of ‘at least one’ or ‘one or more’ may be used to emphasis an inclusive meaning but the absence of these terms should not be taken to infer any exclusive meaning.

The presence of a feature (or combination of features) in a claim is a reference to that feature or (combination of features) itself and to features that achieve substantially the same technical effect (equivalent features). The equivalent features include, for example, features that are variants and achieve substantially the same result in substantially the same way. The equivalent features include, for example, features that perform substantially the same function, in substantially the same way to achieve substantially the same result.

In this description, reference has been made to various examples using adjectives or adjectival phrases to describe characteristics of the examples. Such a description of a characteristic in relation to an example indicates that the characteristic is present in some examples exactly as described and is present in other examples substantially as described. The above description describes some examples of the present disclosure however those of ordinary skill in the art will be aware of possible alternative structures and method features which offer equivalent functionality to the specific examples of such structures and features described herein above and which for the sake of brevity and clarity have been omitted from the above description. Nonetheless, the above description should be read as implicitly including reference to such alternative structures and method features which provide equivalent functionality unless such alternative structures or method features are explicitly excluded in the above description of the examples of the present disclosure.

Whilst endeavoring in the foregoing specification to draw attention to those features believed to be of importance the Applicant may seek protection via the claims in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not emphasis has been placed thereon. l/we claim:

Claims

1. An apparatus comprising means for broadcasting across a limited portion of a duplex band, based on a reserved subset of global synchronization channel numbers, that have been reserved for cells supporting sub-band non-overlapping full duplex communication; and receiving, from a terminal apparatus, a random access message for the sub-band non-overlapping full duplex communication.

2. An apparatus as claimed in claim 1 , comprising means for transmitting in system information validation that the apparatus supports sub-band non-overlapping full duplex communication (SBFD).

3. An apparatus as claimed in claim 1 or 2, comprising means for transmitting in system information validation of resources for initial random access with respect to the apparatus.

4. An apparatus as claimed in any preceding claim, wherein the reserved subset of global synchronization channel numbers is predetermined via specification in a telecommunication standard.

5. A method comprising: broadcasting across a limited portion of a duplex band, based on a reserved subset of global synchronization channel numbers, that have been reserved for indicating that a cell supports sub-band non-overlapping full duplex communication to indicate that the apparatus supports sub-band non-overlapping full duplex communication.

6. A computer program comprising instructions that when executed by one or more processors enables an apparatus to: broadcast across a limited portion of a duplex band, based on a reserved subset of global synchronization channel numbers, that have been reserved for indicating that a cell supports sub-band non-overlapping full duplex communication to indicate that the apparatus supports sub-band non-overlapping full duplex communication.