Methods, apparatus and computer programs

Abstract

Support may be provided for narrowband operation alongside wideband in 6G, using two (or more) different configurations for different synchronisation signals and associated physical broadcast channels

Description

TECHNICAL FIELD Various example embodiments relate generally to to methods, apparatus, system and computer programs and in particular, but not exclusively, methods, apparatus, system and computer programs relating to synchronization signals. BACKGROUND A communication network can be seen as a facility that enables communications between two or more communication devices, or provides communication devices access to a data network. A mobile or wireless communication network is one example of a communication network. Such communication networks operate in according with standards such as those provided by 3GPP (Third Generation Partnership Project) or ETSI (European Telecommunications Standards Institute). Examples of standards are the so-called 5G (5th Generation) standards provided by 3GPP and future standards such as 6G and beyond. BRIEF DESCRIPTION Some example embodiments of this disclosure will be described with respect to certain aspects. These aspects are not intended to indicate key or essential features of the embodiments of this disclosure, nor are they intended to be used to limit the scope of thereof. Other features, aspects, and elements will be readily apparent to a person skilled in the art in view of this disclosure. According to a first aspect, there is provided a user equipment comprising: means for detecting one or more synchronisation signals on a synchronisation raster point of a first synchronisation raster and when a synchronisation signal is not detected, searching for one or more synchronisation signals on another synchronisation raster point of the first synchronisation raster, the first synchronisation raster being associated with a first synchronisation signal and physical broadcast channel configuration having a relatively narrow bandwidth compared to a second synchronisation signal and physical broadcast channel configuration which is associated with a second different synchronization raster, one or more synchronisation signals of the first synchronisation signal and physical broadcast channel configuration being associated with a first sequence length and one or more synchronisation signals of the second synchronisation signal and physical broadcast channel configuration being associated with a second different sequence length; means for detecting one or more master information blocks of a first physical broadcast channel associated with the one or more synchronisation signals, when the one or more synchronisation signals are detected; and means for performing an initial access of a cell associated with the first physical broadcast channel. Other features may be seen from the claims dependent on claim 1. According to a second aspect, there is provided a method comprising: detecting one or more synchronisation signals on a synchronisation raster point of a first synchronisation raster and when a synchronisation signal is not detected, searching for one or more synchronisation signals on another synchronisation raster point of the first synchronisation raster, the first synchronisation raster being associated with a first synchronisation signal and physical broadcast channel configuration having a relatively narrow bandwidth compared to a second synchronisation signal and physical broadcast channel configuration which is associated with a second different synchronization raster, one or more synchronisation signals of the first synchronisation signal and physical broadcast channel configuration being associated with a first sequence length and one or more synchronisation signals of the second synchronisation signal and physical broadcast channel configuration being associated with a second different sequence length; detecting one or more master information blocks of a first physical broadcast channel associated with the one or more synchronisation signals, when the one or more synchronisation signals are detected; and performing an initial access of a cell associated with the first physical broadcast channel. The method may comprise searching, when a synchronisation signal is not detected on a plurality of synchronisation raster points of the first synchronisation raster, for one or more synchronisation signals on one or more synchronisation raster points of a second synchronisation raster. The method may comprise detecting one or more master information blocks of a second physical broadcast channel associated with the one or more synchronisation signals associated with the second synchronisation raster, when the one or more synchronisation signals associated with the second synchronisation raster are detected. The second synchronisation raster may be associated with a second synchronisation signal and physical broadcast channel configuration having a wider bandwidth than the first synchronisation signal and physical broadcast channel configuration. A user equipment may have a bandwidth capability which is less than the bandwidth associated with the second synchronisation signal and physical broadcast channel configuration. The method may comprise excluding from consideration one or more outermost resource blocks of the master information blocks of the second physical broadcast channel in dependence on the bandwidth capability of the user equipment. The method may comprise indicating to an access node of a cell associated with the physical broadcast channel associated with the second synchronisation raster, a bandwidth capability of the user equipment. For one or more of the first and second synchronisation signal and physical broadcast channel configurations, a number of resource blocks allocated to one or more respective synchronization signals may be the same as a number of resource blocks allocated to the physical broadcast channel. For one or more of the first and second synchronisation signal and physical broadcast channel configuration, a number of resource blocks allocated to one or more respective synchronization signals, maybe different to a number of resource blocks allocated to the physical broadcast channel. For one or more of the first and second synchronisation signal and physical broadcast channel configuration, a number of resource blocks allocated to one or more respective synchronization signals, may be half the number of resource blocks allocated to the physical broadcast channel. The bandwidth associated with the second synchronisation signal and physical broadcast channel configuration may comprise a bandwidth of approximately 5MHz with a subcarrier spacing of 15KHz and the bandwidth associated with the first synchronisation signal and physical broadcast channel configuration may comprise a bandwidth of approximately 3MHz with a subcarrier spacing of 15KHz. The first synchronisation signal and physical broadcast channel configuration may be associated with one or more of: a relatively low power wide area use; or a narrowband use. The second synchronisation signal and physical broadcast channel configuration may be associated with one or more of: a relatively low power wide area use; a multi radio access technology spectrum sharing use; or a relatively energy efficient use. The method may be performed by an apparatus. The apparatus may be a user equipment. The apparatus may comprise at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to provide one or more of the methods of the second aspect. According to a third aspect, there is provided a method comprising: determining which one of a plurality of different configuration options is to be used, wherein each of the plurality of different configuration options is for one or more synchronization signals and an associated physical broadcast channel, at least one configuration option being associated with a first sequence length for the one or more synchronization signals and a first bandwidth, and at least one configuration option being associated with a second, different sequence length for the one or more synchronization signals and a second different bandwidth; detecting the respective one or more synchronization signals in dependence on the determined configuration option; and detecting and decoding the associated physical broadcast channel associated with the determined configuration option. The determining which configuration option is to be used may be based on one or more of: a capability of the user equipment to supporta respective configuration option; an operating bandwidth of the user equipment; an operating frequency range of the user equipment; a predefined association between one or more of the configuration options and the operating bandwidth of the user equipment; a predefined association between one or more of the configuration options and the operating frequency range of the user equipment; a duplexing mode of the user equipment; a subcarrier spacing; a priority associated with one or more of the configuration options; or a use case. The use case may comprise: a relatively low power wide area use; a multi radio access technology spectrum sharing use; a relatively energy efficient use; or a narrowband use. The method may comprise determining which configuration option is associated with a respective synchronization signal and physical broadcast channel block transmitted by an access point in dependence on one or more properties of one or more detected synchronization signals. The one or more properties of the one or more detected synchronization signals may comprise one or more of: a content of the one or more detected synchronization signals; a frequency domain location of the one or more detected synchronization signals; or a synchronization raster point of the one or more detected synchronization signals. The first bandwidth may comprise a bandwidth of approximately 5MHz with a subcarrier spacing of 15KHz and the second bandwidth may comprise a bandwidth of approximately 3MHz with a subcarrier spacing of 15KHz. A plurality of different frequency bands may be available, at least one configuration option being associated with each frequency band. At least two configuration options may be associated with one or more of the frequency bands. Only one or two configuration options may be associated with a respective frequency band. For one or more of the configuration options, a number of resource blocks allocated to the one or more synchronization signals may be the same as a number of resource blocks allocated to the physical broadcast channel. For one or more of the configuration options, a number of resource blocks allocated to the one or more synchronization signals may be different to a number of resource blocks allocated to the physical broadcast channel. For one or more of the configuration options, the number of resource blocks allocated to the one or more synchronization signals may be half the number of resource blocks allocated to the physical broadcast channel. For one or more of the configuration options a frequency domain location of a center of the physical broadcast channel may be the same as a frequency domain location of a center of the one or more synchronization signals. For one or more of the configuration options a frequency domain location of a center of the physical broadcast channel may be different to a frequency domain location of the center of the one or more synchronization signals. The method searching for a synchronization raster point associated with the respective configuration option. Two or more of the configuration options may be associated with different synchronization raster points. One or more of the configuration options may be associated with first synchronization raster points and one or more of the configuration options may be associated with second synchronization raster points, the first synchronization raster points being offset from the second synchronization raster points. The method may be performed by an apparatus. The apparatus may comprise one or more means to perform the method. The apparatus may be a user equipment. The apparatus may comprise at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to provide one or more of the methods of the third aspect. According to another aspect, there is provided a computer readable medium comprising program instructions stored thereon for performing at least one of the above methods. According to an aspect, there is provided a non-transitory computer readable medium comprising program instructions stored thereon for performing at least one of the above methods. According to an aspect, there is provided a non-volatile tangible memory medium comprising program instructions stored thereon for performing at least one of the above methods. In the above, many different aspects have been described. It should be appreciated that further aspects may be provided by the combination of any two or more of the aspects described above. Various other aspects are also described in the following detailed description and in the attached claims. LIST OF THE DRAWINGS Some example embodiments will now be described, by way of non-limiting and illustrative example only, with reference to the accompanying Figures in which: Fig. 1 shows an example of a communication network to which examples disclosed herein may be applied; Fig. 2 shows an examples of different configuration options for synchronization signals and an associated physical broadcast channel; Fig. 3 shows an example of a method; Fig. 4 shows, an example of first and second default synchronization rasters; Fig. 5 shows another method of some embodiments; Fig. 6 shows another method of some embodiments and Fig. 7 shows an example of an apparatus. DESCRIPTION OF EMBODIMENTS The following embodiments are exemplary. Although the specification may refer to “an” "one”, or "some” embodiments] in several locations of the text, this does not necessarily mean that each reference is made to the same embodiment's], or that a particular feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments. Further, when a particular feature, structure, or characteristic is described in connection of an embodiment, it is within the knowledge of one skilled in the art to apply such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. It shall be understood that although the terms “first,” “second" and the like may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For the purposes of the present disclosure, the phrases “at least one of A or B", "at least one of A and B”, and “A and / or B” means (A), (B], or (A and B). For the purposes of the present disclosure, the phrase "A, B, and / or C" means [A], (B], (C), (A and B], (A and C), (B and C], or (A, B, and C). Embodiments described may be implemented in a communication network, such as 5G (also called NR], or any future RAT such as 6G and beyond. Moreover, communication within the communication network may utilize any wireless communication technology, comprising but not limited to: Code Division Multiple Access [CDMA], Frequency Division Multiple Access (FDMA], Time Division Multiple Access (TDMA], Frequency Division Duplex [FDD], Time Division Duplex (TDD], Multiple-Input Multiple-Output (MIMO], Orthogonal Frequency Division Multiple (OFDM], and / or Discrete Fourier Transform spread OFDM (DFT-s-OFDM], As used herein, the term "network device” or “network node” refers to a node in a communication network via which user equipment may access the network and / or which is capable of controlling radio communication and managing radio resources within a cell. The network node or network device may be referred to as a base station (BS], an access point (AP] or an access node. The network device may be, depending on the applied technology, for example, a node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), an NR NB (also referred to as a gNB), a Remote Radio Unit (RRU), a radio head (RH), a remote radio head (RRH), a relay, an Integrated Access and Backhaul (1AB) node, a low power node, a non-terrestrial network (NTN) or non-ground network device such as a satellite network device, a low earth orbit (LEO) satellite and a geosynchronous earth orbit (GEO) satellite, or an aircraft network device. Moreover, in connection of split radio access network (RAN), the network device may refer to a centralised unit (CU) of a base station and / or a distributed unit (DU) of a base station. An interface between CU and DU may be referred to as an Fl interface in NR. In the split RAN architecture, node operations may be carried out, at least partly, in the central / centralized unit, CU, (e.g. server, host or node) operationally coupled to the DU, (e.g. a radio head / node). One CU may control one or more DUs, acting at least as transmit / receive (Tx / Rx) nodes. In some embodiments, the DUs may comprise e.g. a radio link control (RLC), medium access control (MAC) layer and a physical (PHY) layer, whereas the CU may comprise the layers above RLC layer, such as a packet data convergence protocol (PDCP) layer, a radio resource control (RRC) and an internet protocol (IP) layers. Other functional splits are possible too. In practice, any processing task may be performed in either the CU or the DU and the boundary where the responsibility is shifted between the CU and the DU may depend on the applied implementation. The term "terminal device” refers to any end device that may be capable of wireless communication. By way of example, a terminal device may be referred to as a communication device, user equipment (UE), a Subscriber Station (SS), or a Mobile Station (MS). The terminal device may include a mobile phone, a cellular phone, a smart phone, voice over IP (VoIP) phones, wireless local loop phones a tablet, a wearable terminal device, a personal digital assistant (PDA), portable computers, desktop computer, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback appliances, vehicle-mounted wireless terminal devices, USB dongles, an Internet of Things (loT) device, a watch or other wearable, a head-mounted display (HMD), a vehicle, a drone, a medical device and applications (e.g., remote surgery), an industrial device and applications (e.g., a robot and / or other wireless devices operating in an industrial and / or an automated processing chain contexts), a consumer electronics device, a device operating on commercial and / or industrial wireless networks, and the like. A term "resource”, as used herein, may refer to radio resources in time domain, in frequency domain, in space domain, and / or in code domain. Some examples of resources include e.g. a physical resource block (PRE), a resource block (RB), a radio frame, a subframe, a time slot, a sub band, a frequency region, a sub-carrier, a beam, etc. The term "transmission” and / or "reception" may refer to wirelessly transmitting and / or receiving via a wireless propagation channel on radio resources. Fig. 1 illustrates an example of a communication network to which examples disclosed herein may be applied. The communication network or a cellular communication network may comprise a network node 110 providing one or more cells, such as cell 100, and a network node 112 providing one or more other cells, such as cell 102. Each cell may be, e.g., a macro cell, a micro cell, femto, or a pico cell, for example. The cell may define a coverage area or a service area of the corresponding access node. The network node 110 may provide a user equipment (UE) 120 (one or more UEs) with wireless access to the communication network. The wireless access may comprise downlink (DL) communication from the network node to the UE 120 and uplink (UL) communication from the UE 120 to the network node. Examples of uplink channels comprise physical uplink control channel (PUCCH) for transmitting control information and physical uplink shared channel (PUSCH) for transmitting data towards the network. Examples of downlink channels comprise physical downlink control channel (PDCCH) for transmitting control information and physical downlink shared channel (PDSCH) for transmitting data towards the user equipment. There may be a plurality of UEs 120, 122 in the system. Each of them may be served by the same or by different network nodes 110, 112. UE may be configured with dual connectivity (DC), wherein the UE, e.g. UE 120, may be connected to multiple network nodes 110, 112. The UEs 120, 122 may communicate with each other, in case de-vice-to-device (D2D) communication interface is established between them via a so-called sidelink (SL). Such D2D communications may be referred to as machine-to-ma-chine, peer-to-peer (P2P) communications, or vehicle-to-vehicle (V2V), for example. In the case of multiple network nodes in the communication network, the network nodes may be connected to each other via an interface. The network nodes 110 and 112 may be further connected via another interface to a core network 116 of the communication network. Some embodiments relate to a physical layer design. This may be for 6G or any other suitable standard. Some embodiments relate to providing support for narrowband operation in 6G. For example there may be a wider band available as well as a narrower band. This narrower band is referred to narrowband in this document. For example, use cases such as so-called low power wide area (LPWA), train control systems, radio interface between gNB and UE , and / or the like may be operating using narrow bandwidth. 3GPP NR originally defined a one synchronization signal block (SSB) structure and subcarrier spacing dependent bandwidth for the structure in Rell5. This was based on a minimum UE bandwidth capability of 5 MHz. This SSB has 4 OFDM symbols, and consists of a primary synchronization signal (PSS), a physical broadcast channel (PBCH), and a secondary synchronization signal (SSS). Rei 18 introduced support for narrowband NR operation (3 MHz) by puncturing the SSB structure set out in Rei 15. This approach may involve problems, e.g. reduce the initial access performance, and increase the UE complexity. This approach may be associated with a longer initial access latency and / or higher miss detection rate of system information reception. Some embodiments may provide support for use cases requiring narrow bandwidth. Some embodiments may provide support of narrowband uses without requiring the puncturing of signals and channels in frequency domain. Some use cases may benefit from a larger carrier bandwidth CBW size as compared to the current CBW of 5G. A larger minimum bandwidth size may benefit some eMBB (enhanced mobile broadband) scenarios. For example, initial access performance (and latency) and opportunities for improved energy efficiency may be improved by increasing the minimum bandwidth size. Some embodiments may provide two or more different configuration options. Each configuration option provides a configuration for one or more synchronisation signals and an associated physical broadcast channel PBCH. The one or more synchronisation signals may be PSS and SSS. The different configuration options may have different options for PSS / SSS and PBCH bandwidth. Some embodiments may provide at least two bandwidth options for synchronization signals (PSS / SSS). Some embodiments may provide at least two bandwidth options for PBCH. Some embodiments may provide at least two ratios between PBCH bandwidth and synchronization signal bandwidth. Reference is made to Table 1 below which shows four different example of configuration options and Figure 2 which shows the resource block configurations for each of the example configuration options. It should be appreciated, that due to the “guard subcarriers” provided for synchronization signals the actual transmission Tx BW of the PSS / SSS signals may be smaller than n (subcarriers / RB) x SS BW (RB), where n is the number of subcarriers per RB (e.g. 12) and SS BW (RBs) is the number of RBs of a respective configuration. Table 1 Config# 1 Config#2 Config# 3 Config#4 SS BW (RBs) 12 24 12 6 PBCHBW (RBs) 24 24 12 6 Ratio (PBCH / SS) 2 1 1 1 The first configuration option, Config #1, may be used for MRSS (Multi-RAT spectrum sharing). This may be similar or the same as that used in 5G. In some embodiments, a common SSB for 5G and 6G may be provided. That common SSB may be as defined by the first configuration option which is the current SSB configuration defined for 5G. The SSB signal of this option may at least partially be used both for a 5G cell and for a 6G cell. As can be seen from Figure 2, the RBs for the SS and the RBs of the PBCH are centred on a centre frequency of the associated bandwidth. The second configuration option, Config #2, may be used for energy efficiency use cases. The periodicity of PSS / SSS may be relaxed. A longer PSS / SSS sequence may reduce a missed detection rate, facilitating a longer PSS / SSS periodicity. The third configuration option, Config #3, may be used for LPWA. The fourth configuration option, Config #4, for may be used for the use case requiring the narrowest bandwidth operation. This maybe to support use cases requiring narrowband operation. There may be one or more frequency bands. For example 6G may have more than one frequency band. In some embodiments, for each frequency band, there may one or more predefined configuration options available to the UE. For example, in some embodiments, there may be up to two different configuration options available for a given frequency band. Some examples are set out below. For a frequency band of up to 1GHz, the available configurations options may be the first and the fourth configuration options -Config #1 or Config #4. For a frequency band between 1 and 2 GHz, the available configurations options may be the first and the third configuration options - Config #1 or Config#3. For a frequency band between 2 and 6 GHz, the available configurations options may be the first and the second configuration options - Config #1 or Config#2. For a frequency band between 6 and 24 GHz, the available configurations option may be the second configuration options - Config #2. For a frequency band between 24 and 52 GHz, the available configurations option may be the second configuration options - Config #2. The SSB options defined for the bandwidth as well as the associated subcarrier spacing(sj) may be defined based on the minimum UE channel bandwidth for the given band. For example, when the operator deploys a frequency band between 1 and 2 GHz band, the SSB configuration option may be selected according to a LPWA deployment scenario. For example, if narrowband UEs are deployed, the third configuration option, Config #3 may be selected. Otherwise, the first configuration option, Config #1, may be selected. It should be noted that the examples of the configuration options shown in table 1 and Figure 2 shows just one example of possible configuration options. For example, more than four configuration options may be provided in some embodiments. In other embodiments, two or more configuration options may be provided. The number of resource blocks provided for the SS and PBCH may differ from those shown in table 1 and Figure 2. As can be seen from the table, there are three RB size options which are used in the configurations: 6, 12 and 24 RBs. In some embodiments, there may only be 2 size options. In other embodiments, there may be more than 3 size options. The size of the resource block options may differ from these example sizes. In the examples shown in Figure 2 and the above table, there are two different ratios of PBCH RBs to SS RBs. In other embodiments, there may be only one ratio or more than two ratios. The available ratios may be the same or different to the example ratios of 1 and 2. In the examples shown in Figure 2 and the above Table 1, the SS and PBCH size are defined in terms of RBs. In other embodiments, one or more of the SS and PBCH may be defined in terms of resource elements (e.g. not corresponding to full RBs), or sub-PRBs. In the examples shown in Figure 2 and the above Table 1, the SS and PBCH are generally arranged symmetrically with respect to the centre frequency of the respective signal bandwidth. However, SS and PBCH may not be symmetrically centred on the channel bandwidth of the cell. This may be to reduce the number of sync raster points that UE may need to test). In other embodiments, the SS and PBCH may have different frequency domain location between SS and PBCH (i.e. not symmetrically arranged with respect to the centre frequency of the respective signal bandwidth). The frequency domain location for the SS and PBCH within a channel bandwidth of the cell may be separately controlled with e.g., resource block offset and / or subcarrier offset. In other embodiments, there may be different symbol allocations for SS and PBCH as compared to the examples shown in in Figure 2 and the table 1. For example, each SSB option could occupy a predefined number of SS and PBCH symbols. One option may be to have the PSS / SSS in the same OFDM symbol with PBCH. In some embodiments, there may be subcarrier spacing (SCS) dependency in the pre-defined symbol allocations. In some embodiments, there may be a SCS dependency for SS and PBCH size options. For example, 15 kHz SCS could operate according to 24 RBs (e.g. Config #2), while 30 kHz SCS could operate according to 12 RBs (e.g. Config #3), respectively, to maintain the same bandwidth. Some examples of minimum UE bandwidths as a function of SCS and SSB BW are set out in tables 2 and 3 below. The first of the tables, table 2, provides the SSB BW associated with each of the different numbers of RBs for different SCS. In this example, the number of RBs are 6,12, 20 and 24. In this example, the SCS are 15, 30,16 and 120 KHz. It may be appreciated that the number of RBs is by way of example and in other embodiments different numbers of RBs may be used. Likewise the SCS values in the table are by way of example only and in different embodiments, different SCS may be used. The second of the tables below. Table 3, provide the minimum UE channel bandwidth CBW for the same SS BW and SCS options in the first of the tables below. It should be noted that the UE minimum channel bandwidth may depend on one or other 5 issues and may thus be equal to or wider than the BWs shown in Tables 2 and 3 below. Min CBW (examples) in Table 3 are calculated based on 86.4% spectrum utilization (SSB Bandwidth / Min UE CBW = 0.864). SSB Bandwidth (MHz) SSB BW (RBs) SCS (kHz) 6 12 20 24 15 1.08 2.16 3.6 4.32 30 2.16 4.32 7.2 8.64 60 4.32 8.64 14.4 17.28 120 8.64 17.28 28.8 34.56 Table 2 Min UE CBW SSB BW (RBs) SCS (kHz) 6 12 20 24 15 1.25 2.5 3.75 5 30 2.5 5 7.5 10 60 5 10 15 20 120 10 20 30 40 Table 3 10 If the PBCH BW is not equal to the PSS / SS BW, then the SSB BW is equal to max(PBCH BW, PSS / SSS BW). One option (option 1) for determining the bandwidth assumption for the SSB may be as follows: Up-to n SSB configuration options per band, where n is an integer of 1 or more, 15 for example 2; The SSB configuration option may define the SSS / PSS BW and / or PBCH BW; and / or The SSB configuration options may define one or more of the maximum number of SSB beams, and / or OFDM symbols for PBCH. Another option (option 2) for determining the bandwidth assumption for the SSB may be as follows: Up-to n PSS / SSS size configurations per band, where n is an integer of 1 or more, for example 2; The PBCH configuration (for example BW, number of OFDM symbols, and / or number of beams) is derived based on the received PSS / SSS. Different SSB configurations may have different number of maximum SSBs (beams). For example, the first configuration, Config #1 has a maximum of 8 SSBs (beams) and the fourth configuration, Config #4 has a maximum of 1 or 2 SSBs (beams). The first configuration, Config #1 may have two PBCH symbols while the fourth configuration, Config #4 may have four PBCH symbols. Synchronization raster dependency will now be discussed. A SSB configuration may depend on the synchronization raster and / or synchronization raster point. Each SSB configuration option may have its own default synchronization raster design (for a specific SCS and frequency range). The default raster design can include synchronization raster points that are common with the default synchronization raster design of another SSB configuration option. A synchronization raster is predefined for all of the SSB configuration options supported on a specific band. The synchronization rasters may be predefined so that synchronization raster for one SSB configuration option does not have any common synchronization raster points with the synchronization raster for another SSB configuration option the within that band. If the default synchronization raster designs have common synchronization raster points, an offset is applied to one of the synchronization rasters in that band to obtain predefined synchronization rasters that are not overlapping. The UE may determine the SSB option to detect based on a synchronization raster point, or frequency, on which it may try to detect the SSB. One example of this is now described with reference to Figure 4. The same default synchronization raster A (referenced sync raster default A in Figure 4) is predefined for the first configuration option, Config#l and the second configuration option, Config#2, as the SSB BW (e.g.24 RBs) and minimum UE channel BW is the same for both options. The third configuration option, Config#3, is in this example, designed for a narrower UE channel BW, and requires a denser synchronization raster. The default synchronization raster B (referenced sync raster default B in Figure 4) for the third configuration, config#3 is designed so that it is well separated in frequency from raster A and does not have any common synchronization raster points with the raster A. When the first configuration option, Config# 1 and third configuration option, Config#3 are predefined for a band, the default synchronization rasters are applied. When first configuration option Config#l and the second configuration option, Config#2 are predefined for a band, the default synchronization raster for e.g. the second configuration option, Config#2 is offset in frequency, so that the synchronization rasters applied on the band are well separated in frequency and do not have any common synchronization raster points. This approach may allow for wider frequency separation between synchronization rasters per band when compared to alternatives where all configuration options would have their own synchronization raster designs applied in all bands and not overlapping in frequency with the synchronization raster design of any other configuration option. The design of a synchronization raster may depend on one or more of the selected minimum channel bandwidth supported by the synchronization raster, density of channel raster, and / or bandwidth of SSB. In some embodiments, the SSB reference frequency positions SSREF for synchronization raster A are as follows: N*1200 kHz + M*50 kHz, M = 1, 3 or 5 For the offset, an offset value is added. For example, the offset may be 600KHz or the like. In some embodiments, the SSB frequency positions SSREF for synchronization raster B are as: N*600 kHz + M*50 kHz + 300 kHz, M = 1, 3 or 5. It may be noted that 100 kHz minimum separation between synchronization rasters may be provided in some embodiments. It should be appreciated that one or more different synchronization rasters may alternatively or additionally be used. The examples shown above may be useful if compatibility with 5G is required In the table below. Table 4, different SSB configuration option combinations per frequency band are listed together with the predefined synchronization rasters per band. This is by way of example only. In this example, different synchronization rasters may be associated or predefined for a given configuration option depending on the band. For example, the second configuration 2, Config #2 has either the default synchronization raster A or the default synchronization raster A with 600 kHz offset depending on the SSB configuration combination predefined for that band. SSB configuration combinations per band Sync raster predefined for the band Config #1 &Config#2 Config 1: Default sync raster A Config 2: Default sync raster A with 600 kHz offset Config# 1 &Config#3 Config 1: Default sync raster A Config 3: Default sync raster B Config#2 &Config#3 Config 2: Default sync raster A Config 3: Default sync raster B TABLE 4 The SSB configuration may alternatively or additionally depend on the SCS used to convey the PSS / SSS. In some embodiments, the number of SCS options per frequency band is one or two. In other embodiments, the number of SCS options may be more than 2. In one option, structure of the SSB both in time and frequency domain and mapping of SSBs on the slots may be different for different configuration options. For example, a first configuration option, config #1 may be similar to NR or 5G-like and may have or more of the following characteristics; PSS / SSS: 12 RBs; PBCH: 24 RBs; Structure in time: One PSS symbol, one SSS symbol, two PBCH symbols; Mapping on the slots: Two SSBs in a slot Default periodicity: 20 ms; and / or Maximum number of SSBs below 6 GHz: 8. For example, a second configuration option, Config #2 may be for energy efficiency (for example, the periodicity of PSS / SSS may be relaxed) use cases for example and may have or more of the following characteristics; PSS / SSS / PBCH: 24 RBs; Structure in time: One PSS symbol, one SSS symbol, two PBCH symbols; Mapping on the slots: Two SSBs in a slot; Default periodicity: 40 ms; and / or Maximum number of SSBs between 7-24 GHz: 32. For example, a third configuration option, Config #3 may be for LPWA use cases for example and may have or more of the following characteristics: PSS / SSS / PBCH: 12 RBs; Structure in time: Two PSS symbols, two SSS symbols, four PBCH symbols; Mapping on the slots: One SSB in a slot; Default periodicity: 10 / 20 ms; and / or Maximum number of SSBs between 1-2 GHz: 2. For example, a fourth configuration option, Config #4 may be for NB-IOT (narrow band internet of things) or other narrow band use cases for example and may have or more of the following characteristics: PSS / SSS / PBCH: 6 RBs; Structure in time: Four PSS symbols, Four SSS symbols, four PBCH symbols; Mapping on the slots: One SSB in a slot; Default periodicity: 10 / 20 ms; and / or Maximum number of SSBs below 1 GHz: 1 Reference is made to Figure 3 which shows an example method. The method may be performed by a UE. In this example, acquisition of the SSB is being used for initial access. However, it should be appreciated that the SSB may need to be acquired for other purpose such for mobility measurements and / or the like. As referenced 1, the UE obtains or determines the frequency band specific predefined SSB configuration option. The determined configuration option may be based on one or more of: a capability of the user equipment to support a respective configuration option; an operating bandwidth of the user equipment (this may be the bandwidth in which the UE is capable of operating); an operating frequency range of the user equipment (this may be the frequency range in which the UE is capable of operating); a predefined association between one or more of the configuration options and the operating bandwidth of the user equipment; a predefined association between one or more of the configuration options and the operating frequency range of the user equipment; a duplexing mode of the user equipment; a subcarrier spacing; a priority associated with one or more of the configuration options; or a use case. For example, based on the searched frequency band and predefined, e.g. standardized, SSB configuration options associated with the frequency band, the UE may determines the SSB configuration options valid for the frequency band. The UE may determine the synchronization rasters associated with the SSB configuration options on that frequency band. For example, the UE may, based on UE capabilities, e.g., on supported channel bandwidths and / or prior information on the network, select one of the valid SSB configuration options. The UE may determine frequency and time domain locations of the SSs and PBCH of the selected SSB configuration option. In some embodiments, the UE may do a cell search assuming both configuration options are possible. In this case, it might be more flexible and up to the operator to decide which option is used in which part of the band. Based on that, 6G eMBB UEs may be able to operate according to narrowband SSB or wideband SSB. In the case that UE capabilities are suitable for both configuration options, the determination by the UE would be the selection of a prioritised SSB configuration, i.e., the configuration based on which UE performs a cell search first, before switching to the second configuration. As referenced 2, the UE detect the PSS. The UE thus searches for the PSS. based on the determination discussed previously. The UE performs a search for PSS on the determined synchronization raster. Based on detected PSS, the UE acquires time-frequency synchronization. As referenced 3, the UE detects the SSS for refined synchronization as well as for further information e.g. on cell identity and frame timing. As referenced 4, the UE detects and decodes the PBCH, containing necessary system information. As referenced 5, the UE determines, based on the detected SSB, whether to access the associated cell and perform initial access. In one embodiment a UE performs PSS / SSS detection looking only at a single bandwidth. By way of example, the UE may be detecting the PSS / SSS of configuration option for a narrow band use case. In this example, the UE is only detecting the PSS / SSS of the selected configuration option in a given frequency band. When the UE does not detect the PSS / SSS on a synchronization raster point, the UE continues to search on another synchronization raster point on the same synchronization raster for the selected configuration option. This continues until the PSS / SSS is detected on the synchronization raster for the selected configuration option. When the PSS / SSS is detected on a synchronization raster point, the UE detects associated MIB (master information block) and performs an initial access. In another embodiment a UE is capable of performing PSS / SSS detection with two bandwidths. By way of example, the UE may be supporting a LPWA use case. The UE may detect the PSS / SSS of a narrowband option of a frequency band on a synchronisation raster point. When the PSS / SSS is detected on a synchronization raster point, the UE detects associated MIB and performs an initial access. If the UE does not detect the PSS / SSS of the narrowband option of the frequency band on any synchronisation raster point on that specific raster for that narrow band option, the UE continues search on another synchronisation raster point of a different configuration option. The UE may need to continue the search with puncturing (i.e. uses the same or substantially same bandwidth as for narrowband option) if the different configuration option is associated with a larger bandwidth than can be used by the UE. For example, if the PSS / SSS of narrowband option on a band is not detected on a synchronization raster point (e.g. after testing one, more or all synchronization raster points of the first synchronization raster), the UE changes to a second different synchronisation raster. The UE will search for a synchronization raster point of the second raster. The UE may search the synchronisation raster points until the PSS / SSS is detected. This second raster may be associated with a configuration option with wider bandwidth frequency. This option may be advantageous when applied to cases where the PSS / SSS bandwidth is the same for two configuration options in a same frequency band, for example the first configuration, Config #1 and the third configuration, Config #3. If the UE detects PSS / SSS on a synchronisation raster point of the second synchronisation raster, the UE tries to detect the associated MIB. This is performed according to maximum bandwidth the UE supports. The UE may exclude from consideration the outermost RBs of the transmitted PBCH transmitted by base station which fall outside the bandwidth supported by the UE . The receiver of the UE may consider the corresponding resource elements of the outermost RBs as zeros when detecting the MIB. The UE may only use information in the inner RBs of the MIB. The UE may not use or detect information in the outer RBs of the MIB where the UE does not support a bandwidth. The UE detects the MIB successfully, and performs further initial access. As part of that, UE may indicate to the base station, the bandwidth capability of the UE. This may be the case when the UE has a more limited bandwidth capability than the detected configuration. Alternatively, if UE does not detect MIB, the UE may try again for the next PBCH transmission. Reference is made to FIG. 5 which show a method of some example embodiments. This method may be performed by an apparatus. The apparatus may comprise or be a user equipment. The apparatus may comprise suitable means, such as circuitry for providing the method. Alternatively or additionally, the apparatus may comprise at least one processor and at least one memory storing instructions that, when executed by the at least one processor cause the apparatus at least to provide the method below. Alternatively or additionally, the apparatus may be such as discussed in relation to FIG. 7. The method may be provided by computer program code or computer executable instructions. The method may comprise as referenced Al, determining which one of a plurality of different configuration options is to be used, wherein each of the plurality of different configuration options is for one or more synchronization signals and an associated physical broadcast channel, at least one configuration option being associated with a first sequence length for the one or more synchronization signals and a first bandwidth, and at least one configuration option being associated with a second, different sequence length for the one or more synchronization signals and a second different bandwidth. The method may comprise as referenced A2, detecting the respective one or more synchronization signals in dependence on the determined configuration option. The method may comprise as referenced A3, detecting and decoding the associated physical broadcast channel associated with the determined configuration option. Reference is made to FIG. 6 which show a method of some example embodiments. This method may be performed by an apparatus. The apparatus may comprise or be a user equipment. The apparatus may comprise suitable means, such as circuitry for providing the method. Alternatively or additionally, the apparatus may comprise at least one processor and at least one memory storing instructions that, when executed by the at least one processor cause the apparatus at least to provide the method below. Alternatively or additionally, the apparatus may be such as discussed in relation to FIG. 7. The method may be provided by computer program code or computer executable instructions. The method may comprise as referenced Bl, detecting one or more synchronization signals on a synchronization raster point of a first synchronization raster and when a synchronization signal is not detected, searching for one or more synchronization signals on another synchronization raster point of the first synchronization raster, the first synchronization raster being associated with a first synchronization signal and physical broadcast channel configuration having a relatively narrow bandwidth compared to a second synchronization signal and physical broadcast channel configuration which is associated with a second different synchronization raster, one or more synchronization signals of the first synchronization signal and physical broadcast channel configuration being associated with a first sequence length and one or more synchronization signals of the second synchronization signal and physical broadcast channel configuration being associated with a second different sequence length. The method may comprise as referenced B2, detecting one or more master information blocks of a first physical broadcast channel associated with the one or more synchronization signals, when the one or more synchronization signals are detected. The method may comprise as referenced B3, performing an initial access of a cell associated with the first physical broadcast channel. Fig. 7shows, by way of example, a block diagram of an apparatus 10. The apparatus 10 comprises, for example, at least one processor 12 and at least one memory 14 storing instructions 15 that, when executed by the at least one processor, cause the apparatus 10 at least to perform the method or methods as disclosed herein, and any of the embodiments thereof. In an example, the at least one memory and the instructions (e.g. a computer program code, software), are configured, with the at least one processor, to cause the apparatus 10 to perform the method or methods as disclosed herein, and any of the embodiments thereof. A processor 12 may comprise circuitry, or be constituted as circuitry or circuitries, the circuitry or circuitries being configured to perform phases of methods in accordance with example embodiments described herein. As used in this application, the term “circuitry” may refer to one or more or all of the following: (a) hardware-only circuit implementations, such as implementations in only analog and / or digital circuitry, and (b) combinations of hardware circuits and software, such as, as applicable: (i) a combination of analog and / or digital hardware circuit(s) with software / firmware and (ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a user equipment, to perform various functions) and (c) hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portion of a microprocessor's), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation. This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device. The memory 14 may be implemented using any suitable data storage technology. The memory may comprise a database for storing data. The memory 14 may be at least in part external to apparatus 10 but accessible to apparatus 10. The instructions 15 may be comprised in a computer readable medium or a non-transitory computer readable medium. A term non-transitory, as used herein, is a limitation of the medium itself (i.e. tangible, not a signal) as opposed to a limitation on data storage persistency (e.g. random access memory, RAM, vs. read only memory, ROM). For example, the apparatus 10 is a terminal device, such as the UE of Fig. 1. As another example, the apparatus is comprised in such a terminal device, e.g. as a chipset configured to control the terminal device. The apparatus 10 may be caused or configured to perform at least the method of Fig. 5 or 6 and / or any one or more of the embodiments described. The apparatus 10 comprises a radio interface 16. The radio interface 16 may provide the apparatus 10 with communication capabilities. The radio interface 16 may comprise a receiver configured to receive information in accordance with at least one cellular or non-cellular standard. The radio interface 16 may comprise a transmitter configured to transmit information in accordance with at least one cellular or non-cellular standard. The receiver may comprise more than one receiver. The transmitter may comprise more than one transmitter. The radio interface 16 may comprise a transceiver configured to receive and transmit information in accordance with at least one cellular or non-cellular standard. The transceiver may comprise more than one transceiver. The apparatus 10 may optionally comprise a user interface 18 comprising, for example, at least one of a keypad, a microphone, a touch display, a display, a speaker, etc. The user interface 18 may be used to control the apparatus by the user. The user interface 18 may be external to the apparatus 10. For example, the apparatus 10 may be connected to another device, such as a computer, either via wireless or wired connection, and the apparatus 10 is controlled by the user via the computer. In an embodiment, at least some of the processes described herein may be carried out by an apparatus comprising means for carrying out at least some of the described processes. Means for performing method steps as disclosed herein may include software and / or hardware components of the apparatus 10. For example, the at least one processor 12, the memory 14, and the computer program code form means for carrying out the method or methods as disclosed herein, and any of the embodiments thereof. As used herein the term “means” is to be construed in singular form, i.e., referring to a single element, or in plural form, i.e. referring to a combination of single elements. Therefore, terminology “means for [performing A, B, C]”, is to be interpreted to cover an apparatus in which there is only one means for performing A, B and C, or where there are separate means for performing A, B and C, or partially or fully overlapping means for performing A, B, C. Further, terminology “means for performing A, means for performing B, means for performing C" is to be interpreted to cover an apparatus in which there is only one means for performing A, B and C, or where there are separate means for performing A, B and C, or partially or fully overlapping means for performing A, B, C. Even though the invention has been described above with reference to various examples according to the accompanying drawings, it is clear that the invention is not restricted thereto but can be modified in several ways within the scope of the appended claims. Therefore, all words and expressions should be interpreted broadly and they are intended to illustrate, not to restrict, the embodiment. It will be obvious to a person skilled in the art that, as technology advances, the inventive concept can be implemented in various ways. Further, it is clear to a person skilled in the art that the described embodiments may, but are not required to, be combined with other embodiments in various ways.

Claims

1. A user equipment comprising:means for detecting one or more synchronisation signals on a synchronisation raster point of a first synchronisation raster and when a synchronisation signal is not detected, searching for one or more synchronisation signals on another synchronisation raster point of the first synchronisation raster, the first synchronisation raster being associated with a first synchronisation signal and physical broadcast channel configuration having a relatively narrow bandwidth compared to a second synchronisation signal and physical broadcast channel configuration which is associated with a second different synchronization raster, one or more synchronisation signals of the first synchronisation signal and physical broadcast channel configuration being associated with a first sequence length and one or more synchronisation signals of the second synchronisation signal and physical broadcast channel configuration being associated with a second different sequence length;means for detecting one or more master information blocks of a first physical broadcast channel associated with the one or more synchronisation signals, when the one or more synchronisation signals are detected; andmeans for performing an initial access of a cell associated with the first physical broadcast channel.

2. The user equipment as claimed in claim 1, wherein the meansfor searching for one or more synchronisation signals is further for searching, when a synchronisation signal is not detected on a plurality of synchronisation raster points of the first synchronisation raster, for one or more synchronisation signals on one or more synchronisation raster points of a second synchronisation raster.

3. The user equipment as claimed in claim 2, wherein the meansfor detecting one or more master information blocks is further for detecting one or more master information blocks of a second physical broadcast channel associated with the one or more synchronisation signals associated with the second synchronisation raster, when the one or more synchronisation signals associated with the second synchronisation raster are detected.

4. The user equipment as claimed in claim 2 or 3, wherein the second synchronisation raster is associated with a second synchronisation signal and physical broadcast channel configuration having a wider bandwidth than the first synchronisation signal and physical broadcast channel configuration.

5. The user equipment as claimed in claim 4, wherein the userequipment has a bandwidth capability which is less than the bandwidth associated with the second synchronisation signal and physical broadcast channel configuration6. The user equipment as claimed in claim 4, wherein the meansfor detecting one or more master information blocks of the second physical broadcast channel is for excluding from consideration one or more outermost resource blocks of the master information blocks in dependence on the bandwidth capability of the user equipment.

7. The user equipment as claimed in claim 3 or any claim dependent on claim 3, wherein the means for performing an initial access of a cell associated with the physical broadcast channel associated with the second synchronisation raster is further for indicating to an access node of the cell a bandwidth capability of the user equipment.

8. The user equipment as claimed in any preceding claim whereinfor one or more of the first and second synchronisation signal and physical broadcast channel configurations, a number of resource blocks allocated to one or more respective synchronization signals is the same as a number of resource blocks allocated to the physical broadcast channel.

9. The user equipment as claimed in any preceding claim whereinfor one or more of the first and second synchronisation signal and physical broadcast channel configuration, a number of resource blocks allocated to one or more respective synchronization signals, is different to a number of resource blocks allocated to the physical broadcast channel.

10. The user equipment as claimed in claim 9, wherein for one ormore of the first and second synchronisation signal and physical broadcast channel configuration, a number of resource blocks allocated to one or more respective synchronization signals, is half the number of resource blocks allocated to the physical broadcast channel.

11. The user equipment as claimed in any preceding claim, whereinthe bandwidth associated with the second synchronisation signal and physical broadcast channel configuration comprises a bandwidth of approximately 5MHz with a subcarrier spacing of 15KHz and the bandwidth associated with the first synchronisation signal and physical broadcast channel configuration comprises a bandwidth of approximately 3MHz with a subcarrier spacing of 15KHz.

12. The user equipment as claimed in any preceding claim, whereinthe first synchronisation signal and physical broadcast channel configuration is associated with one or more of:a relatively low power wide area use; ora narrowband use.

13. The user equipment as claimed in any preceding claim, whereinthe second synchronisation signal and physical broadcast channel configuration is associated with one or more of:a relatively low power wide area use;a multi radio access technology spectrum sharing use; ora relatively energy efficient use.

14. A method comprising:detecting one or more synchronisation signals on a synchronisation raster point of a first synchronisation raster and when a synchronisation signal is not detected, searching for one or more synchronisation signals on another synchronisation raster point of the first synchronisation raster, the first synchronisation raster being associated with a first synchronisation signal and physical broadcast channel configuration having arelatively narrow bandwidth compared to a second synchronisation signal and physical broadcast channel configuration which is associated with a second different synchronization raster, one or more synchronisation signals of the first synchronisation signal and physical broadcast channel configuration being associated with a first sequence length5 and one or more synchronisation signals of the second synchronisation signal and physical broadcast channel configuration being associated with a second different sequence length;detecting one or more master information blocks of a first physical broadcast channel associated with the one or more synchronisation signals, when the one or more10 synchronisation signals are detected; andperforming an initial access of a cell associated with the first physical broadcast channel.

15. A computer program comprising computer executable instruc-15 tions which when executed cause the method of claim 14 to be performed.

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