SSB periodicity extension in ntn

Abstract

Example embodiments of the present disclosure relate to SSB search in a NTN. A terminal device includes at least one processor; and at least one memory including computer program codes; wherein the at least one memory and the computer program codes are configured to, with the at least one processor, cause the terminal device to: select a synchronization raster point from a plurality of synchronization raster points to initiate cell search, determine whether the synchronization raster point is associated with an SSB periodicity among a set of Synchronization Signal Block (SSB) periodicities, and select another SSB periodicity from the set of SSB periodicities for SSB search if it is determined that the synchronization raster point is not associated with the SSB periodicity.

Description

SSB PERIODICITY EXTENSION IN NTNFIELD

[0001] Embodiments of the present disclosure generally relate to the field of telecommunication and, in particular, to a method, device, apparatus and computer readable storage medium for SSB search in a NTN.BACKGROUND

[0002] Wireless networking provides significant advantages for user mobility. To use the service of a wireless network, a user equipment (UE) should perform a cell search to identify a cell that is available for camping. For example, the UE may scan one or more frequency bands and monitor for synchronization information broadcast by a cell of the network. Once detected, the UE may acquire time and frequency synchronization with the cell using the synchronization information. The cell search procedure may precede the establishment of a connection between the UE and the cell. Therefore, the duration of the cell search procedure has a direct impact on the amount of time it takes the UE to access network services via the cell.

[0003] Nowadays, Non Terrestrial Networks (NTNs) have been proposed to enhance the mobile network services for UEs. NTNs are wireless communication systems that operate above the Earth’s surface, involving satellites at low Earth orbit (LEO), medium Earth orbit (MEO) and geostationary orbit (GEO), high-altitude platforms (HAPS) and drones. To support NTN services, some features should be updated for 5G New Radio (NR) specifications.SUMMARY

[0004] In general, example embodiments of the present disclosure provide a solution for Synchronization Signal Block (SSB) search in a NTN by introducing additional SSB periodicities.

[0005] In a first aspect, there is provided a terminal device for a NTN. The terminal device includes at least one processor; and at least one memory including computer program codes; wherein the at least one memory and the computer program codes are configured to, with theat least one processor, cause the terminal device to: select a synchronization raster point from a plurality of synchronization raster points to initiate cell search, determine whether the synchronization raster point is associated with an SSB periodicity among a set of Synchronization Signal Block (SSB) periodicities, and select another SSB periodicity from the set of SSB periodicities for SSB search if it is determined that the synchronization raster point is not associated with the SSB periodicity.

[0006] In a second aspect, there is provided a method for SSB search in a NTN. The method includes selecting a synchronization raster point from a plurality of synchronization raster points to initiate cell search, determining whether the synchronization raster point is associated with an SSB periodicity among a set of SSB periodicities, and selecting another SSB periodicity from the set of SSB periodicities for SSB search if it is determined that the synchronization raster point is not associated with the SSB periodicity.

[0007] In a third aspect, there is provided a terminal device for a NTN. The terminal device includes at least one processor; and at least one memory including computer program codes; wherein the at least one memory and the computer program codes are configured to, with the at least one processor, cause the terminal device to: select a synchronization raster point from a plurality of synchronization raster points to initiate cell search, determine whether the synchronization raster point is associated with a specific Synchronization Signal Block (SSB) periodicity, and select another synchronization raster point associated with another SSB periodicity from the plurality of synchronization raster points for SSB search if it is determined that the synchronization raster point is not associated with the specific SSB periodicity.

[0008] In a fourth aspect, there is provided a method for SSB search in a NTN. The method includes selecting a synchronization raster point from a plurality of synchronization raster points to initiate cell search, determining whether the synchronization raster point is associated with a specific Synchronization Signal Block (SSB) periodicity, and selecting another synchronization raster point associated with another SSB periodicity from the plurality of synchronization raster points for SSB search if it is determined that the synchronization raster point is not associated with the specific SSB periodicity.

[0009] In a fifth aspect, there is provided a non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least the method according to the above second or fourth aspect.

[0010] It is to be understood that the summary section is not intended to identify key or essential features of embodiments of the present disclosure, nor is it intended to be used to limit the scope of the present disclosure. Other features of the present disclosure will become easily comprehensible through the following description.BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Some example embodiments will now be described with reference to the accompanying drawings, where:

[0012] Fig. 1 illustrates an example communication system in which example embodiments of the present disclosure may be implemented;

[0013] Fig. 2 shows a process of SSB search in the communication system according to some example embodiments of the present disclosure;

[0014] Fig. 3 shows a process of SSB search in the communication system according to some other example embodiments of the present disclosure; and

[0015] Fig. 4 illustrates a block diagram of an example computer readable medium in accordance with some example embodiments of the present disclosure.

[0016] Throughout the drawings, the same or similar reference numerals represent the same or similar element.DETAILED DESCRIPTION

[0017] Principle of the present disclosure will now be described with reference to some example embodiments. It is to be understood that these embodiments are described only for the purpose of illustration and help those skilled in the art to understand and implement the present disclosure, without suggesting any limitation as to the scope of the disclosure. The disclosure described herein can be implemented in various manners other than the ones described below.

[0018] In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skills in the art to which this disclosure belongs.

[0019] References in the present disclosure to “one embodiment,” “an embodiment,” “some embodiments,” and the like indicate that the embodiment described may include a particularfeature, structure, or characteristic, but it is not necessary that every embodiment includes the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

[0020] It shall be understood that although the terms “first” and “second” etc. 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 example, a first element could be termed a second element, and similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term “and / or” includes any and all combinations of one or more of the listed terms.

[0021] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises”, “comprising”, “has”, “having”, “includes” and / or “including”, when used herein, specify the presence of stated features, elements, and / or components etc., but do not preclude the presence or addition of one or more other features, elements, components and / or combinations thereof.

[0022] 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 mobile phone or server, to perform various functions), and(c) hardware circuit(s) and or processor(s), such as a microprocessor s) or a portionof 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.

[0023] 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.

[0024] As used herein, the term “communication network” or “communication system” refers to a network following any suitable communication standards, such as New Radio (NR), Long Term Evolution (LTE), LTE-Advanced (LTE-A), Wideband Code Division Multiple Access (WCDMA), High-Speed Packet Access (HSPA), Narrow Band Internet of Things (NB-IoT) and so on. Furthermore, the communications between a terminal device and a network device in the communication system may be performed according to any suitable generation communication protocols, including, but not limited to, the first generation (1G), the second generation (2G), 2.5G, 2.75G, the third generation (3G), the fourth generation (4G), 4.5G, the fifth generation (5G) communication protocols, and / or any other protocols either currently known or to be developed in the future. Embodiments of the present disclosure may be applied in various communication systems. Given the rapid development in communications, there will of course also be future type communication technologies and systems with which the present disclosure may be embodied. It should not be seen as limiting the scope of the present disclosure to only the aforementioned system.

[0025] As used herein, the term “network device” refers to a node in a communication network via which a terminal device accesses the network and receives services therefrom. The network device may refer to a base station (BS) or an access point (AP), for example, a node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), a NR NB (also referred to as a gNB), a Remote Radio Unit (RRU), a radio header (RH), a remote radio head (RRH), a relay, a low power node such as a femto node, a pico node, and so forth, depending on the applied terminology and technology. In case of 5G NR over NTN of the present disclosure, the network device may also refer to a satellite or a HAPS, which provides NTN services for terminal devices being located in the coverage of the network device.

[0026] The term “terminal device” refers to any end device that may be capable of wireless communication. By way of example rather than limitation, a terminal device may also be referred to as a communication device, user equipment (UE), a Subscriber Station (SS), a Portable Subscriber Station, a Mobile Station (MS), or an Access Terminal (AT). The terminal device may include, but not limited to, 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, wireless endpoints, mobile stations, laptop-embedded equipment (LEE), laptop-mounted equipment (LME), USB dongles, smart devices, wireless customer-premises equipment (CPE), 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. In the following description, the terms “terminal device”, “communication device”, “terminal”, “user equipment” and “UE” may be used interchangeably. In case of 5G NR over NTN of the present disclosure, the terminal device may also be called a NR NTN device or a NTN UE.

[0027] Principle and embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. Reference is first made to Fig. 1, which illustrates an example communication system 100 in which example embodiments of the present disclosure may be implemented. The communication system 100 may include one or more terminal devices, such as a terminal device 110, and one or more network devices, such as a network device 120-1 and a network device 120-2 which serve an area 121 and an area 122, respectively (also called as a cell 121 and a cell 122). The network device 120-1 may be a gNB which provides 5G connection and communication for terminal devices being located in the cell 121. In this case, the network 120-1 and the terminal device 110 may form part of a general 5G NR network. The network device 120-2 may be a satellite such as at LEO, MEO or GEO, or a HAPS, which provides NTN services for terminal devices being located in the cell 122. In this case, the network device 120-2 and the terminal devices such as the terminal device 110 supporting NTN services may form part of a NTN and the terminal device 110 may also be called a NTN UE.

[0028] To support 5G NR over NTN, many aspects of the 3 GPP NR specification should be updated. For example, at 3 GPP RAN plenary meeting #104, the work item description (WID) for NR over NTN phase 3 has proposed that RANI should report on impact to backward compatibility, if any, for potential extension of the SSB periodicity at the latest by RAN#106, in conjunction with the targeted system-level enhancements, and RANI should further consider issues such as UE’s cell search complexity and impact to initial cell selection, latency and success rate, for the SSB periodicity extension.

[0029] To access a cell, such as the cell 122, the terminal device 110 should perform cell search to acquire time and frequency synchronization with the cell and to detect the physical layer Cell ID of the cell.

[0030] In one aspect, the terminal device 110 may know the carrier frequencies to be searched. In this regard, the terminal device 110 may receive synchronization signals (SS) such as the primary synchronization signal (PSS) and the secondary synchronization signal (SSS) in order to perform the cell search.

[0031] In another aspect, the terminal device 110 may be not aware of the carrier frequencies to be searched. For this, the terminal device 110 will know a number of carrier frequencies which the network device such as the network device 120-2 may potentially be transmitting the SSB. These carrier frequencies are denoted as synchronization raster points.

[0032] As stated in 3GPP TS 38.108, a global synchronization raster is defined for all frequencies. The frequency position of the SS block (SSB) is defined as SSREF with corresponding number GSCN (Global Synchronization Channel Number). Also, the specification defines the synchronization raster and the subcarrier spacing of the synchronization block separately for each band.

[0033] The below Table 1 in 3GPP TS 38.108 gives the correspondence between the SSB frequency positions (i.e., the synchronization raster points) and the GSCNs.Table 1

[0034] When performing a cell search, the terminal device 110 will investigate each carrier frequency defined by the synchronization raster points. One way to do this would be to monitor the signal reception at each candidate carrier frequency for a duration that exceeds the SSB periodicity. In case of not finding any signal within this period (no PSS and no SSS observed (potentially not even any power observed)), the terminal device 110 will retune to another candidate carrier frequency and perform a similar search in the time domain. To reduce the overall time required for performing a complete cell search, there is some sparsity in the synchronization raster points when operating below 3 GHz. Therefore, a synchronization raster as shown in Table 2 below may be deduced from above Table 1. It can be seen that, the separation between adjacent synchronization raster points is 100 kHz in clusters of 3, while each cluster is separated by 1 MHz.Table 2

[0035] Therefore, for NTN services, SSB periodicity extension may be applied to enhance DL coverages, while the terminal device may still assume a default SSB periodicity such as 20ms to perform the cell search, which may result in that the terminal device may not detect the SSB in the sweep of an candidate carrier frequency and retune to another candidate carrier frequency and thus cell search time may be increased or even no cell could be identified.

[0036] In view of this, the present disclosure proposes to introduce one or more additional default SSB periodicities for cell search by the terminal device to support enlargement of the cell coverage of NTNs.

[0037] In some embodiments, currently defined synchronization raster points may be used to associate with additional SSB periodicities. In some other embodiments, newsynchronization raster points may be introduced to associate with additional SSB periodicities. Hereinafter, these embodiments are described in detail in connection with Fig.2 and Fig. 3, respectively.

[0038] Reference is now made to Fig. 2, which shows a process 200 of SSB search in the communication system 100 according to some example embodiments of the present disclosure. For the purpose of discussion, the process 200 will be described with reference to Fig. 1. The process 200 may involve the terminal device 110 and the network device 120-2 as illustrated in Fig. 1. In the embodiments of Fig. 2, a synchronization raster point is associated with a set of SSB periodicities including newly introduced SSB periodicities. That is, the synchronization raster points may be prior synchronization raster points, while each synchronization raster point may be additionally associated with newly introduced SSB periodicities. The correspondence between each synchronization raster point and the set of SSB periodicities may be predefined by the specification, and may be hard-coded in the terminal device 110 in advance or deduced by the terminal device 110.

[0039] In the process 200, at block 210, the terminal device 110 may select a synchronization raster point from a plurality of synchronization raster points to initiate cell search.

[0040] As stated in 3GPP TS 38.108, a global synchronization raster is defined for all frequencies. The frequency position of the SS block (SSB) is defined as SSREF with corresponding number GSCN (Global Synchronization Channel Number). Also, the specification defines the synchronization raster and the subcarrier spacing of the synchronization block separately for each band. Therefore, the terminal device 110 may know all the synchronization rater points to be investigated for the cell search, and at block 210, the terminal device 110 may select any one of the synchronization rater points to start the cell search.

[0041] At block 220, the terminal device 110 may determine whether the synchronization raster point selected at block 210 is associated with a Synchronization Signal Block (SSB) periodicity among a set of SSB periodicities.

[0042] Herein, the set of SSB periodicities includes, in addition to the prior SSB periodicity such as 20ms, the newly introduced one or more SSB periodicities to extend the SSB periodicity. The newly introduced SSB periodicities may be at least one of 40ms, 80ms, 160ms, 320ms and 640ms, for example. Hereinafter, the newly introduced SSBperiodicities are 40ms and 160ms as examples, and thus the set includes 20ms, 40ms and 160ms. The thus constructed correspondence between the SSB periodicities and the SSB frequency positions (i.e., the synchronization raster points) may be amended to the Table 3 below from the Table 2 above.Table 3

[0043] In the above Table 3, M2=7 and M3=9 indicate the newly introduced SSB periodicities of 40ms and 160ms, respectively, which may be used in place of M in the above equation of Table 1.

[0044] In one embodiment, the SSB periodicity of block 220 may be the minimum one in the set, that is, the 20ms. In this way, by trying the SSB periodicities one by one in the increasing order, missing of SSB may be avoided.

[0045] If it is determined at block 220 that the synchronization raster point selected at block 210 is not associated with the SSB periodicity, the terminal device 110 may select, at block 230, another SSB periodicity from the set of SSB periodicities.

[0046] In particular, the terminal device 110 may select the next one SSB periodicity in the set, i.e., 40ms, to try the SSB search.

[0047] The terminal device 110 may repeat the determination at block 220 for the newly selected SSB periodicity. That is, at block 240, the terminal device 110 may determine whether the synchronization raster point selected at block 210 is associated with the another SSB periodicity selected at block 230.

[0048] If it is determined at block 240 that the synchronization raster point selected at block 210 is associated with the another SSB periodicity selected at block 230, the terminal device 110 may detect, at block 250, the SSB based on the another SSB periodicity.

[0049] Otherwise, if it is determined at block 220 that the synchronization raster point selected at block 210 is associated with the SSB periodicity selected at block 220, the terminal device 110 may detect the SSB, at block 260, the SSB based on the SSB periodicity selected at block 220.

[0050] Furthermore, after block 250 or block 260, the terminal device 110 may further determine, at block 270, whether any SSB is detected, and if it is determined that no SSB is detected at block 270, the terminal device 110 may turn to block 210 to select another synchronization raster point from the plurality of synchronization raster points.

[0051] Although not shown in Fig. 2, if it is determined at block 240 that the synchronization raster point selected at block 210 is not associated with the another SSB periodicity selected at block 230, the process 200 may further turn to block 230 to select a further another SSB periodicity from the set, until all candidate SSB periodicities in the set have been tried and the process 200 may proceed to block 210 to select another synchronization raster point.

[0052] At block 250 or 260, the terminal device 110 may detect the SSB by searching for an SSB search period, and the SSB search period may be equal to or larger than the corresponding SSB periodicity plus a buffer time. The buffer time is used to cover the risk of monitoring starting in the middle of a PSS / SSS transmission, which is roughly 1 ms.

[0053] In other words, in the process 200, the terminal device 110 may traverse each SSB periodicity of the set of SSB periodicities associated with each synchronization raster point to detect the SSB. With additional SSB periodicities being introduced in the set of SSB periodicities, the SSB search may be enhanced to facilitate the larger span of candidate SSB periodicities.

[0054] Reference is now made to Fig. 3, which shows a process 300 of SSB search in the communication system 100 according to some other example embodiments of the present disclosure. Similarly, the process 300 will be described with reference to Fig. 1, and the process 300 may involve the terminal device 110 and the network device 120-2 as illustrated in Fig. 1. In the embodiments of Fig. 3, new synchronization raster points are introduced in addition to prior synchronization raster points, while each newly introduced synchronization raster point may be associated with a new SSB periodicity. The correspondence between each synchronization raster point and the SSB periodicity may be predefined by the specification, and may be hard-coded in the terminal device 110 in advance or deduced by the terminal device 110.

[0055] In the process 300, at block 310, similar to block 210, the terminal device 110 may select a synchronization raster point from a plurality of synchronization raster points to initiate cell search.

[0056] As stated in 3GPP TS 38.108, a global synchronization raster is defined for all frequencies. The frequency position of the SS block (SSB) is defined as SSREF with corresponding number GSCN (Global Synchronization Channel Number). Also, the specification defines the synchronization raster and the subcarrier spacing of the synchronization block separately for each band. Therefore, the terminal device 110 may know all the synchronization rater points to be investigated for the cell search, including the newly introduced synchronization rater points, and at block 310, the terminal device 110 may select any one of the synchronization rater points to start the cell search.

[0057] The plurality of synchronization raster points in these embodiments of process 300 may be different from those of process 200 in that the plurality of synchronization raster points of process 300 may include newly introduced synchronization raster points in addition to those currently defined in the specification.

[0058] At block 320, the terminal device 110 may determine whether the synchronization raster point selected at block 310 is associated with a specific SSB periodicity.

[0059] In one embodiment, the specific SSB periodicity may be the prior SSB periodicity such as 20ms currently defined in the specification. However, those skilled in the art may appreciate that the specific SSB periodicity may be any other SSB periodicity in all the SSB periodicities including the extended SSB periodicities.

[0060] If it is determined at block 320 that the synchronization raster point selected at block 210 is not associated with the specific SSB periodicity, the terminal device 110 may select, at block 330, another synchronization raster point from the plurality of SSB periodicities.

[0061] In particular, the terminal device 110 may select the next synchronization raster point to try the SSB search.

[0062] The terminal device 110 may repeat the determination at block 320 for the newly selected synchronization raster point. That is, at block 340, the terminal device 110 may determine whether the another synchronization raster point selected at block 330 is associated with another SSB periodicity.

[0063] If it is determined at block 340 that the another synchronization raster point selected at block 330 is associated with the another SSB periodicity, the terminal device 110 may detect, at block 350, the SSB based on the another SSB periodicity.

[0064] Otherwise, if it is determined at block 320 that the synchronization raster pointselected at block 310 is associated with the specific SSB periodicity, the terminal device 110 may detect the SSB, at block 360, the SSB based on the specific SSB periodicity.

[0065] Furthermore, after block 350 or block 360, the terminal device 110 may further determine, at block 370, whether any SSB is detected, and if it is determined that no SSB is detected at block 370, the terminal device 110 may turn to block 330 to select a further another synchronization raster point from the plurality of synchronization raster points.

[0066] Although not shown in Fig. 3, if it is determined at block 340 that the another synchronization raster point selected at block 330 is not associated with the another SSB periodicity, the process 300 may further turn to block 330 to select a further another synchronization raster point from the plurality of synchronization raster points, until all candidate synchronization raster points have been traversed.

[0067] At block 350 or 360, the terminal device 110 may detect the SSB by searching for an SSB search period, and the SSB search period may be equal to or larger than the corresponding SSB periodicity plus a buffer time. The buffer time is used to cover the risk of monitoring starting in the middle of a PSS / SSS transmission, which is roughly 1 ms.

[0068] In other words, in the process 300, the terminal device 110 may traverse each synchronization raster point to see whether it is associated with an SSB periodicity until it finds such a synchronization raster point to detect the SSB with its associated SSB periodicity. With additional synchronization raster points being introduced each being associated with an extended SSB periodicity, the SSB search may be enhanced to larger coverages.

[0069] With the above embodiments, a new solution is provided to support SSB search in a NTN by introducing additional SSB periodicities, which may improve the NTN services with larger coverages.

[0070] In some example embodiments, an apparatus is provided capable of performing the above process 200. The apparatus may include means for selecting a synchronization raster point from a plurality of synchronization raster points to initiate cell search, means for determining whether the synchronization raster point is associated with an SSB periodicity among a set of SSB periodicities, and means for selecting another SSB periodicity from the set of SSB periodicities for SSB search if it is determined that the synchronization raster point is not associated with the SSB periodicity. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

[0071] In some example embodiments, an apparatus is provided capable of performing theabove process 300. The apparatus may include means for selecting a synchronization raster point from a plurality of synchronization raster points to initiate cell search, means for determining whether the synchronization raster point is associated with a specific Synchronization Signal Block (SSB) periodicity, and means for selecting another synchronization raster point associated with another SSB periodicity from the plurality of synchronization raster points for SSB search if it is determined that the synchronization raster point is not associated with the specific SSB periodicity. For example, the means may be implemented in a circuitry or software module.

[0001] Fig. 4 is a simplified block diagram of a device 400 that is suitable for implementing example embodiments of the present disclosure. The device 400 may be provided to implement the communication device, for example the terminal device 110 or the network device 120-1 or 120-2 as shown in Fig. 1. As shown, the device 400 includes one or more processors 410, one or more memories 420 coupled to the processor 410, and one or more communication modules 440 coupled to the processor 410.

[0002] The communication module 440 is for bidirectional communications. The communication module 440 has at least one antenna to facilitate communication. The communication module 440 may include any interface that is necessary for communication with other network elements.

[0003] The processor 410 may be of any type suitable to the local technical network and may include one or more of the following: general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multicore processor architecture, as non-limiting examples. The device 400 may have multiple processors, such as an application specific integrated circuit chip that is slaved in time to a clock which synchronizes the main processor.

[0004] The memory 420 may include one or more non-volatile memories and one or more volatile memories. Examples of the non-volatile memories include, but are not limited to, a Read Only Memory (ROM) 424, an electrically programmable read only memory (EPROM), a flash memory, a hard disk, a compact disc (CD), a digital video disk (DVD), and other magnetic storage and / or optical storage. Examples of the volatile memories include, but are not limited to, a random access memory (RAM) 422 and other volatile memories that will not last in the power-down duration.

[0005] A computer program 430 includes computer executable instructions that areexecuted by the associated processor 410. The program 430 may be stored in the memory, e.g., ROM 424. The processor 410 may perform any suitable actions and processing by loading the program 430 into the RAM 422.

[0006] The example embodiments of the present disclosure may be implemented by means of the program 430 so that the device 400 may perform any process of the disclosure as discussed with reference to Fig. 2 or Fig. 3. The example embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.

[0007] In some example embodiments, the program 430 may be tangibly contained in a computer readable medium which may be included in the device 400 (such as in the memory 420) or other storage devices that are accessible by the device 400. The device 400 may load the program 430 from the computer readable medium to the RAM 422 for execution. The computer readable medium may include any types of tangible non-volatile storage, such as ROM, EPROM, a flash memory, a hard disk, CD, DVD, and the like. Fig. 5 shows an example of the computer readable medium 500 in form of CD or DVD. The computer readable medium 500 has the program 430 stored thereon.

[0008] Generally, various embodiments of the present disclosure may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device. While various aspects of embodiments of the present disclosure are illustrated and described as block diagrams, flowcharts, or using some other pictorial representations, it is to be understood that the block, apparatus, system, technique or method described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

[0009] The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer readable storage medium. The computer program product includes computer-executable instructions, such as those included in program modules, being executed in a device on a target real or virtual processor, to carry out the process 200 or 300 as described above with reference to Figs. 2-3. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures,or the like that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or split between program modules as desired in various embodiments. Machine-executable instructions for program modules may be executed within a local or distributed device. In a distributed device, program modules may be located in both local and remote storage media.

[0010] Program code for carrying out methods of the present disclosure may be written in any combination of one or more programming languages. These program codes may be provided to a processor or controller of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the program codes, when executed by the processor or controller, cause the functions / operations specified in the flowcharts and / or block diagrams to be implemented. The program code may execute entirely on a machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.

[0011] In the context of the present disclosure, the computer program code or related data may be carried by any suitable carrier to enable the device, apparatus or processor to perform various processes and operations as described above. Examples of the carrier include a signal, computer readable medium, and the like.

[0012] The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable medium may include but not limited to an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of the computer readable storage medium would include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD- ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0013] Further, while operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Likewise, while several specific implementation details are contained in the abovediscussions, these should not be construed as limitations on the scope of the present disclosure, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable sub-combination.

[0014] Although the present disclosure has been described in languages specific to structural features and / or methodological acts, it is to be understood that the present disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

WHAT IS CLAIMED IS:

1. A terminal device for a Non Terrestrial Network (NTN), comprising: at least one processor; and at least one memory including computer program codes; wherein the at least one memory and the computer program codes are configured to, with the at least one processor, cause the terminal device to: select a synchronization raster point from a plurality of synchronization raster points to initiate cell search, determine whether the synchronization raster point is associated with an SSB periodicity among a set of Synchronization Signal Block (SSB) periodicities, and select another SSB periodicity from the set of SSB periodicities for SSB search if it is determined that the synchronization raster point is not associated with the SSB periodicity.

2. The terminal device of claim 1, wherein the terminal device is further caused to determine whether the synchronization raster point is associated with the another SSB periodicity, and detect an SSB based on the another SSB periodicity if it is determined that the synchronization raster point is associated with the another SSB periodicity.

3. The terminal device of claim 1, wherein the terminal device is further caused to detect an SSB based on the SSB periodicity if it is determined that the synchronization raster point is associated with the SSB periodicity.

4. The terminal device of claim 1 or 3, wherein the terminal device is further caused to determine whether any SSB is detected, and select another synchronization raster point from the plurality of synchronization raster points if it is determined that no SSB is detected.

5. The terminal device of claim 1, wherein the set of SSB periodicities includes 20ms and at least one of 40ms, 80ms, 160ms, 320ms and 640ms.

6. The terminal device of claim 1, wherein the SSB periodicity includes 20ms.

7. The terminal device of claim 1, wherein correspondence between each of the plurality of synchronization raster points and the set of SSB periodicities is predefined.

8. A method for Synchronization Signal Block (SSB) search in a Non Terrestrial Network (NTN), comprising: selecting a synchronization raster point from a plurality of synchronization raster points to initiate cell search, determining whether the synchronization raster point is associated with an SSB periodicity among a set of SSB periodicities, and selecting another SSB periodicity from the set of SSB periodicities for SSB search if it is determined that the synchronization raster point is not associated with the SSB periodicity.

9. The method of claim 8, further comprising determining whether the synchronization raster point is associated with the another SSB periodicity, and detecting an SSB based on the another SSB periodicity if it is determined that the synchronization raster point is associated with the another SSB periodicity.

10. The method of claim 8, further comprising detecting an SSB based on the SSB periodicity if it is determined that the synchronization raster point is associated with the SSB periodicity.

11. The method of claim 8 or 10, further comprising determining whether any SSB is detected, and selecting another synchronization raster point from the plurality of synchronization raster points if it is determined that no SSB is detected.

12. The method of claim 8, wherein the set of SSB periodicities includes 20ms and at least one of 40ms, 80ms, 160ms, 320ms and 640ms.

13. The method of claim 8, wherein the SSB periodicity includes 20ms.

14. The method of claim 8, wherein correspondence between each of the plurality of synchronization raster points and the set of SSB periodicities is predefined.

15. A non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least one of the method of claims 8 to 14.

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