Method, communication device and satellite transmitter for cell synchronization in non-geostationary orbit satellite mobile communication system

Abstract

In a non-geostationary orbit (NGSO) satellite mobile communication system, a communication device receives a synchronization signal block (SSB), which is subjected to partial pre-compensation, from an NGSO satellite transmitter through a downlink (DL) beam, and then transmits the received synchronization signal block (SSB) to the NGSO satellite transmitter through the downlink (DL) beam. And realizing cell synchronization with the NGSO satellite transmitter by using the SSB subjected to partial pre-compensation. A center frequency of a primary synchronization signal and a center frequency of a secondary synchronization signal within the partially pre-compensated SSB are pre-offset by the NGSO satellite transmitter by an integer number of subcarriers relative to a center frequency of the partially pre-compensated SSB to achieve a correlation with movement of the NGSO satellite transmitter relative to the coverage on the earth of the DL beam According to the method, partial pre-compensation of Doppler shift (DS) is carried out. Even if Doppler frequency offset is large due to high mobility of an NGSO satellite, cell synchronization can be simplified.

Description

Technical Field

[0001] This invention generally relates to the field of communication systems; more specifically, it relates to a method for cell synchronization in a non-Geostationary Orbit (NGSO) satellite mobile communication system, a communication device for cell synchronization in an NGSO satellite mobile communication system, and an NGSO satellite transmitter. Background Technology

[0002] Doppler shift (DS) is a well-known phenomenon characterized by a change in the nominal carrier frequency of a signal caused by the relative motion between the signal source and the observer. In the realm of non-terrestrial networks (NTNs), Doppler shift significantly impacts the performance of satellite-based communication systems. The magnitude of Doppler shift depends on several factors, including the satellite's orbital velocity, the location and velocity of the user equipment (UE), and the carrier frequency employed. Satellite velocity depends on orbital altitude, defined by Kepler's laws of planetary motion. Typically, Low Earth Orbit (LEO) satellites travel at approximately 28,000 km / h. In contrast, the UE's velocity depends on the Earth's rotational speed at a given latitude and the UE's own motion. Notably, the region of fastest Earth rotation is located at the equator, at approximately 1670 km / h. In an exemplary scenario, for an LEO satellite, considering altitudes of 400 km, 800 km, and 1200 km, a Doppler frequency offset of 3.7 GHz was observed at locations on Earth at a certain distance from the sub-satellite point. It was also observed that the Doppler frequency offset due to satellite motion exceeded ±70 kHz. Therefore, it can be said that the Doppler frequency offset is proportional to the carrier frequency, meaning that in high-frequency bands, the Doppler frequency offset can be much larger than the subcarrier spacing (SCS). In the context of NTN communication, the SCS value varies based on the frequency band used. For example, in the Sub-6 GHz band commonly used in 5G New Radio (5G NR), possible SCS values ​​are [15, 30, 60] kHz, while higher frequency bands may include SCS values ​​of [60, 120, 240] kHz. Currently, for direct access from NTN to UE, according to 3GPP technical report TR38.821, the SCS value is specified as [15, 30] kHz. In systems based on Orthogonal Frequency-Division Multiplexing (OFDM) (such as 5G NR), Doppler frequency offset, measured in Hertz (Hz), introduces a deviation between the carrier frequency of the received signal and the frequency grid of the OFDM system; this deviation is called Carrier Frequency Offset (CFO). For proper demodulation, CFO needs to be estimated and compensated at the receiver. For LEO NTN communication, the CFO caused by Doppler frequency offset can be a multiple of the SCS and may exceed a threshold.For cell search, the UE needs to perform hypothesis testing on different hypothetical subcarrier offsets to detect the synchronization signal, which is done not only in the time domain but also in the frequency domain. The UE can achieve this by offsetting a locally generated copy of the synchronization signal along the frequency axis by a multiple of the SCS, but this is computationally very expensive when the timing boundaries of the OFDM signal are unknown.

[0003] Currently, some attempts have been made to reduce the synchronization complexity at the UE end due to the large Doppler frequency offset in the NTN, such as full Doppler frequency offset compensation. In this case, the pre-compensated value corresponds to the Doppler frequency offset value at the beam center. Pre-compensation can be applied to all downlink (DL) channels or the complete Synchronization Signal Block (SSB). By offsetting the radio frequency (RF) in each beam to cancel the Doppler frequency offset, pre-compensation for the full Doppler frequency offset at the satellite end reveals the following technical problems. When pre-compensating for the full Doppler frequency offset at the transmitter, the parameter set (numerology) of the transmitted OFDM waveform does not conform to the current NR standard. This is because the subcarriers of the transmitted signal are offset by a non-integer multiple of the SCS, which disrupts the frequency grid structure of the transmitter's OFDM system. When applying pre-compensation to the complete SSB, the UE still needs to know the absolute Doppler frequency offset value pre-compensated at the satellite end to accurately determine the frequency allocation of other data channels, which increases control overhead. Applying pre-compensation to all DL channels introduces additional power consumption and computational complexity to the base station (BS) transmitter. Therefore, the following technical problem exists: due to the high mobility of LEO satellites leading to significant Doppler frequency offset, the computational load of the cell search mechanism is extremely high.

[0004] Therefore, in light of the above discussion, it is necessary to overcome the shortcomings associated with the aforementioned traditional methods used to reduce the computational complexity of cell synchronization in NTN due to large Doppler frequency offsets. Summary of the Invention

[0005] This application provides a method for cell synchronization in a non-Geostationary Orbit (NGSO) satellite mobile communication system, a communication device for cell synchronization in an NGSO satellite mobile communication system, and an NGSO satellite transmitter. This application provides a solution to the existing problem that the high mobility of LEO satellites leads to a large Doppler frequency offset, resulting in a very high computational load for cell search mechanisms. The purpose of this application is to provide an improved method for cell synchronization in a non-Geostationary Orbit (NGSO) satellite mobile communication system, a communication device for cell synchronization in an NGSO satellite mobile communication system, and an NGSO satellite transmitter, which at least partially solve the problems encountered in the prior art.

[0006] The objective of this application is achieved through the technical solutions provided in the appended independent claims. Advantageous implementations of this application are further defined in the dependent claims.

[0007] In one aspect, this application provides a method for cell synchronization in a non-Geostationary Orbit (NGSO) satellite mobile communication system. The method includes: a communication device receiving a partially pre-compensated synchronization signal block (SSB) from an NGSO satellite transmitter via a downlink (DL) beam; and achieving cell synchronization with the NGSO satellite transmitter using the partially pre-compensated SSB, wherein the center frequencies of the primary synchronization signal (PSS) and secondary synchronization signal (SSS) within the partially pre-compensated SSB are pre-offset by an integer number of subcarriers by the NGSO satellite transmitter relative to the center frequency of the partially pre-compensated SSB to achieve partial pre-compensation for Doppler frequency offset related to the movement of the NGSO satellite transmitter relative to the coverage area of ​​the DL beam on Earth.

[0008] The disclosed method achieves a simplified cell synchronization mechanism even with significant Doppler frequency offsets due to the high mobility of LEO satellites. The method achieves partial Doppler frequency offset pre-compensation by pre-offsetting the positions of the PSS and SSS subcarriers within the existing empty subcarrier region of the SSB. Therefore, since the PSS and SSS subcarriers remain on the predefined frequency grid, the New Radio (NR) parameter set in the transmitted signal is not disrupted. Furthermore, because the offset is performed within the existing empty subcarrier region, spectral efficiency is maintained.

[0009] In one implementation, the center frequencies of the PSS and the SSS are pre-offset by an integer number of subcarriers within the partially pre-compensated SSB based on the orbital altitude and speed of the NGSO satellite transmitter, the coverage area of ​​the DL beam, the carrier frequency of the DL channel, and the subcarrier spacing (SCS) of the partially pre-compensated SSB.

[0010] Using the above factors to determine the integer number of subcarriers for the center frequency pre-offset of the PSS and SSS within the partially pre-compensated SSB is beneficial for accurately and reliably achieving partial pre-compensation of Doppler frequency offset.

[0011] In another implementation, the center frequencies of the PSS and the SSS are pre-offset in the range of -9 to +9 subcarriers within the empty subcarrier region of the partially pre-compensated SSB.

[0012] By pre-offsetting the center frequencies of the PSS and SSS within the empty subcarrier area of ​​the partially pre-compensated SSB, the NR parameter set of the transmitted signal is maintained, and the computational complexity of the UE for cell synchronization is reduced.

[0013] In another implementation, the method further includes: in order to achieve the cell synchronization, the communication device correlates the received DL signal including the partially pre-compensated SSB with a locally generated set of PSS waveforms, wherein each PSS waveform has a possible value for a residual portion of the Doppler frequency offset in frequency, the residual portion of which is not compensated by the partial pre-compensation of the NGSO satellite transmitter; and determines the maximum correlation value.

[0014] Determining the maximum correlation value indicates that the NGSO satellite transmitter applies partial Doppler frequency offset precompensation to the PSS and SSS, thereby reducing explicit signaling between the NGSO satellite transmitter and communication equipment.

[0015] In another implementation, the method further includes: if the maximum correlation value is less than a predefined threshold, the communication device achieves cell synchronization by correlating the DL signal with a larger set of locally generated PSS waveforms, wherein each PSS waveform is offset in frequency by the maximum possible Doppler frequency offset related to the motion-dependent movement of the NGSO satellite transmitter relative to the coverage area of ​​the DL beam.

[0016] Determining that the maximum correlation value is less than a predefined threshold indicates that the NGSO satellite transmitter did not apply partial Doppler frequency offset precompensation to the PSS and SSS, thereby reducing explicit signaling between the NGSO satellite transmitter and communication equipment.

[0017] In another implementation, the method further includes: after achieving cell synchronization, the communication device detects the physical cell identity (PCI); and based on the received PSS and SSS, estimates the residual portion of the Doppler frequency offset.

[0018] Detecting PCI and estimating the residual part of Doppler frequency offset based on the received PSS and SSS helps to reduce computational complexity.

[0019] In another implementation, the method further includes: the communication device determining the value of the partial pre-compensation for the Doppler frequency offset performed by the NGSO satellite transmitter based on the difference between the center frequencies of the subcarriers of the received PSS and SSS and the received demodulation reference signal (DMRS) of the physical broadcast channel (PBCH) within the partially pre-compensated SSB.

[0020] The method described above determines the absolute Doppler frequency offset information by measuring the relative frequency interval between the partially Doppler frequency offset pre-compensated PSS and SSS and the uncompensated PBCH DMRS within the same SSB. Therefore, there is no need to introduce additional control signaling to the communication equipment to indicate the absolute Doppler frequency offset value.

[0021] In another implementation, the method further includes: the communication device determining a value of the Doppler frequency offset related to the movement of the NGSO satellite transmitter relative to the coverage area of ​​the DL beam, based on the estimated residual portion of the Doppler frequency offset and the determined value of the partial pre-compensation of the Doppler frequency offset.

[0022] The Doppler frequency offset value, determined based on the estimated residual portion of the Doppler frequency offset and the determined value of the partially pre-compensated Doppler frequency offset, can be used to compensate for other DL channels that have not undergone partial compensation, depending on the movement of the NGSO satellite transmitter relative to the coverage area of ​​the DL beam.

[0023] In another implementation, the method further includes: the communication device using the determined value of the Doppler frequency offset to compensate for the phase distortion of the DL data signal associated with the DL beam, wherein the DL data signal includes a Physical Downlink Control Channel (PDCCH) signal or a Physical Downlink Shared Channel (PDSCH) signal.

[0024] The disclosed method improves the spectral efficiency of various communication channels (including PDCCH, PDSCH, Physical Uplink Shared Control Channel (PUSCH), and Physical Uplink Control Channel (PUCCH)) while reducing the processing complexity and control overhead of these channels.

[0025] In another implementation, the method further includes: if the PCI detected based on the received PSS and SSS belongs to a predefined identifier set, the communication device determines that the partial pre-compensation for the Doppler frequency offset is applied to the DL signal by the NGSO satellite transmitter.

[0026] Instructing communication equipment whether the NGSO satellite transmitter should apply partial pre-compensation for Doppler frequency offset to the PSS and SSS can help reduce signaling overhead.

[0027] In another implementation, the method further includes: the communication device determining the SCS ratio between the Physical Random Access Channel (PRACH) signal and the SCS used in the partially pre-compensated SSB; pre-offsetting the PRACH subcarrier position in the PRACH signal by a value, wherein the value is defined by the determined value of the partially pre-compensated Doppler frequency offset and the determined SCS ratio; and transmitting the pre-offset PRACH signal to the NGSO satellite transmitter.

[0028] The above method includes partial Doppler frequency offset pre-compensation by pre-offsetting the PRACH subcarrier position based on the detected partial Doppler frequency offset of PSS and SSS, thereby keeping the NR parameter set of the transmitted signal unchanged. Furthermore, this method simplifies the PRACH signal detection at the base station.

[0029] In another aspect, this application provides a communication device for cell synchronization in a non-Geostationary Orbit (NGSO) satellite mobile communication system. The communication device is used to: receive a partially pre-compensated synchronization signal block (SSB) from an NGSO satellite transmitter via a downlink (DL) beam; and achieve cell synchronization with the NGSO satellite transmitter using the partially pre-compensated SSB, wherein the center frequencies of the primary synchronization signal (PSS) and secondary synchronization signal (SSS) within the partially pre-compensated SSB are pre-offset by an integer number of subcarriers by the NGSO satellite transmitter relative to the center frequency of the partially pre-compensated SSB to achieve partial pre-compensation for Doppler frequency offset related to the movement of the NGSO satellite transmitter relative to the coverage area of ​​the DL beam on Earth.

[0030] After executing the above method, the aforementioned communication device achieves all the advantages and technical effects of the above method.

[0031] In another aspect, this application provides a non-geostationary orbit (NGSO) satellite transmitter for determining a partially pre-compensated value for the Doppler frequency offset related to the movement of the NGSO satellite transmitter relative to the coverage area of ​​the downlink (DL) beam on Earth. The NGSO satellite transmitter is further configured to pre-offset the center frequencies of the primary synchronization signal (PSS) and secondary synchronization signal (SSS) within a synchronization signal block (SSB) relative to the center frequency of the SSB by an integer number of subcarriers corresponding to the determined value of the partially pre-compensated Doppler frequency offset, to obtain a partially pre-compensated SSB. The NGSO satellite transmitter is further configured to transmit the partially pre-compensated SSB within the coverage area of ​​the DL beam.

[0032] After implementing the above method, the NGSO satellite transmitter achieved all the advantages and technical effects of the above method.

[0033] In another aspect, this application provides a method for cell synchronization in a non-Geostationary Orbit (NGSO) satellite mobile communication system. The method includes: an NGSO satellite transmitter determining a partially pre-compensated value for the Doppler frequency offset related to the movement of the NGSO satellite transmitter relative to the coverage area of ​​a downlink (DL) beam on Earth; the NGSO satellite transmitter pre-offsetting the center frequencies of the primary synchronization signal (PSS) and secondary synchronization signal (SSS) within a synchronization signal block (SSB) relative to the center frequency of the SSB by an integer number of subcarriers corresponding to the determined value of the partially pre-compensated Doppler frequency offset, to obtain a partially pre-compensated SSB; and the NGSO satellite transmitter transmitting the partially pre-compensated SSB within the coverage area of ​​the DL beam.

[0034] It should be understood that all of the above implementation methods can be combined together.

[0035] It should be noted that all devices, elements, circuits, units, and modules described in this application can be implemented in software or hardware elements or any combination thereof. All steps performed by the various entities described in this application, and the functions described to be performed by the various entities, are intended to indicate that the respective entities are suitable for or used to perform the corresponding steps and functions. Although specific functions or steps performed by external entities are not reflected in the detailed description of the specific elements of the entities performing the specific steps or functions in the following description of specific embodiments, it will be apparent to those skilled in the art that these methods and functions can be implemented by corresponding software or hardware elements or any combination thereof. It is understood that the features of this application are readily combined in various ways without departing from the scope of this application as defined by the appended claims.

[0036] Other aspects, advantages, features, and objectives of this application will become apparent from the accompanying drawings and the detailed description of illustrative implementations as interpreted in conjunction with the following appended claims. Attached Figure Description

[0037] A better understanding of the above-described invention and the following detailed description of illustrative embodiments can be obtained by reading the accompanying drawings. Exemplary structures of this application are shown in the drawings to illustrate the present application. However, this application is not limited to the specific methods and tools disclosed herein. Furthermore, those skilled in the art will understand that the drawings are not drawn to scale. Where possible, the same elements are represented by the same numbers.

[0038] The embodiments of this application are described below by way of example only, with reference to the following accompanying drawings, in which: Figure 1 This is a flowchart of a cell synchronization method in a non-Geostationary Orbit (NGSO) satellite mobile communication system according to an embodiment of this application; Figure 2 A communication device for cell synchronization in an NGSO satellite mobile communication system according to one embodiment of this application is shown; Figure 3 An NGSO satellite transmitter according to one embodiment of this application is shown; Figure 4 This is a flowchart of a method for cell synchronization in an NGSO satellite mobile communication system according to another embodiment of this application; Figure 5 A synchronization signal block (SSB) comprising a primary synchronization signal (PSS) and a secondary synchronization signal (SSS) offset by frequency subcarriers is shown according to an embodiment of this application. Figure 6 This is a method for detecting absolute Doppler frequency offset using a SSB with partial Doppler frequency offset pre-compensation, according to one embodiment of the present application; Figure 7 This is a flowchart of a UE determining whether a base station (BS) applies partial Doppler frequency offset pre-compensation without explicit signaling, according to one embodiment of this application. Figure 8 This is a method for a UE to apply partial Doppler frequency offset precompensation to the Physical Random-Access Channel (PRACH) for uplink (UL) transmission, according to one embodiment of this application. Figure 9An exemplary scenario of partial Doppler frequency offset precompensation of PRACH according to an embodiment of this application is shown.

[0039] In the accompanying diagram, underlined numbers indicate the item containing the underlined number or the item adjacent to the underlined number, while ununderlined numbers refer to items identified by lines linking the ununderlined number to the item. When a number is ununderlined and has an associated arrow, the ununderlined number identifies the general item that the arrow points to. Detailed Implementation

[0040] The following detailed description illustrates embodiments of this application and ways in which these embodiments can be implemented. While some modes of implementing this application have been disclosed, those skilled in the art will recognize that other embodiments for implementing or practicing this application may also exist.

[0041] Figure 1 This is a flowchart illustrating a method for cell synchronization in a non-Geostationary Orbit (NGSO) satellite mobile communication system according to an embodiment of this application. (See reference...) Figure 1 This paper illustrates a method 100 for cell synchronization in a non-Geostationary Orbit (NGSO) satellite mobile communication system. Method 100 includes steps 102 and 104. Step 104 is optional.

[0042] A method 100 for cell synchronization in non-Geostationary Orbit (NGSO) satellite mobile communication systems is provided. Traditionally, direct access from a satellite (such as a Low Earth Orbit (LEO) satellite) to a User Equipment (UE) requires the UE to achieve time and frequency synchronization through a process called cell search. Cell search can be defined as an initial synchronization process initiated by the UE when it first attempts to connect to a network (such as a Non-Terrestrial Network (NTN)) or reconnects after a link interruption. Cell search includes identifying candidate cells, detecting synchronization signals to achieve time and frequency synchronization, and determining the Physical Cell Identity (PCI), which is necessary for decoding the Physical Broadcast Channel (PBCH). Due to the high mobility of LEO satellites resulting in large Doppler shifts (DS), the cell search process is computationally very demanding. Compared to traditional cell search procedures, Method 100 simplifies the two-dimensional (2D) search for the Primary Synchronization Signal (PSS) in both the time and frequency domains into a one-dimensional (1D) search in the time domain alone, achieving a simplified and efficient NTN cell search, thereby reducing UE power consumption. By reducing the search dimension, Method 100 can reduce the storage space required to store relevant results, thus saving memory on the UE. Furthermore, Method 100 accelerates cell search speed because the search space for the synchronization signal is significantly reduced, meaning the UE can connect to the network more quickly.

[0043] In step 102, method 100 includes: a communication device receiving a partially pre-compensated synchronization signal block (SSB) from an NGSO satellite transmitter via a downlink (DL) beam; and using the partially pre-compensated SSB to achieve cell synchronization with the NGSO satellite transmitter, wherein the center frequencies of the primary synchronization signal (PSS) and secondary synchronization signal (SSS) within the partially pre-compensated SSB are pre-offset by an integer number of subcarriers by the NGSO satellite transmitter relative to the center frequency of the partially pre-compensated SSB to partially pre-compensate the Doppler frequency offset related to the movement of the NGSO satellite transmitter relative to the coverage area of ​​the DL beam on Earth. For NTN, the Doppler frequency offsets of different satellite downlink beams are different; therefore, for each satellite beam, partial pre-compensation is performed on the PSS and SSS to accelerate cell search (also known as cell detection). The term "partial" has two meanings: First, pre-compensation is performed only for the PSS and SSS within the SSB, not for the entire SSB; second, pre-compensation is performed only for the integer portion of the Doppler frequency offset caused by satellite motion (or NGSO satellite transmitter motion), not for the entire Doppler frequency offset. Partial pre-compensation of the Doppler frequency offset is achieved by offsetting the PSS and SSS subcarriers within the existing empty subcarrier region within the SSB. Therefore, since the PSS and SSS subcarriers remain on the predefined frequency grid, the New Radio (NR) parameter set in the transmitted signal is unaffected. Furthermore, since the offset is performed within the existing empty subcarrier region, spectral efficiency is maintained. In method 100, after time / frequency synchronization is achieved using the pre-compensated PSS and SSS, the communication device (or UE) can easily detect the absolute value of the Doppler frequency offset. This is achieved by detecting the frequency spacing between the pre-compensated PSS and SSS within the same SSB and the uncompensated PBCH demodulation reference signal (DMRS). Therefore, there is no need to introduce additional control signaling to indicate the absolute Doppler frequency offset value to the communication device (i.e., UE). Furthermore, the partially pre-compensated SSB is not generated by the communication device but received from the NGSO satellite transmitter; therefore, the partially pre-compensated SSB can also be referred to as the received partially pre-compensated SSB.

[0044] In step 104, based on the NGSO satellite transmitter's orbital altitude and speed, the coverage area of ​​the DL beam, the carrier frequency of the DL channel, and the subcarrier spacing (SCS) of the partially pre-compensated SSB, an integer number of subcarriers are pre-offset of the center frequencies of the PSS and SSS within the partially pre-compensated SSB. In other words, the absolute value of the Doppler frequency offset of the DL beam within the satellite's (i.e., the NGSO satellite transmitter's) coverage area is based on multiple network components, including the NGSO satellite transmitter's orbital altitude and speed, the DL band, the carrier frequency, and the beam position within the satellite's coverage area.

[0045] For a satellite beam projected onto the Earth's surface (i.e., an NGSO satellite transmitter), the satellite determines the Doppler frequency offset on that beam caused by the satellite's motion of the communication equipment (i.e., the UE). The satellite can infer the Doppler frequency offset information of the beam using the position of the beam relative to the sub-satellite point, the satellite's velocity, and the carrier frequency. The Doppler frequency offset, expressed as SCS, consists of two parts: an integer part and a fractional part (the latter determined by the communication equipment or UE). The absolute Doppler frequency offset on the satellite is calculated according to equation (1): (1) in, It is the DL carrier frequency. It's the speed of light. It is the gravitational constant. It is the mass of the Earth. It is the Earth's radius. It is the orbital altitude. It is the angle between the direction of wave propagation of a specific beam and the direction of satellite motion. Typically, a subsatellite point refers to a point on Earth directly below the satellite, also known as the nadir.

[0046] According to one embodiment, the center frequencies of the PSS and SSS are pre-offset within the empty subcarrier region of the partially pre-compensated SSB by a range of -9 to +9 subcarriers. The center frequencies of the PSS and SSS are pre-offset within the empty subcarrier region based on the absolute value of the Doppler frequency offset. Typically, an NR SSB comprises the PSS, SSS, and PBCH. The SSB spans 240 subcarriers in the frequency domain and four Orthogonal Frequency Division Multiplexing (OFDM) symbols in the time domain. The first and third OFDM symbols within the SSB include unused subcarriers, which are defined as "zeroed" subcarriers. In the third OFDM symbol (where the SSS is located), there are 9 unused subcarriers above and 9 unused subcarriers below, for a total of 18 unused subcarriers. Therefore, for the Fifth Generation (5G) Frequency Range-1 (FR1) (including bands below 6 GHz), the maximum pre-compensable Doppler frequency offset by the satellite (i.e., the NGSO satellite transmitter) is ±135 kHz and ±270 kHz, respectively, when the sub-carrier spacing (SCS) is 15 kHz and 30 kHz. If the maximum pre-compensation value has been reached at the satellite end, the remaining portion is handled by the communication equipment (i.e., the UE).

[0047] For example, if the absolute value of the Doppler frequency offset for a specific beam is found to be +75 kHz, the NGSO satellite transmitter determines the PSS and SSS subcarrier offsets as follows: (a) Case 1: When the SCS is 15 kHz, the subcarrier offset = = →The subcarrier position needs to be offset by 5 subcarriers.

[0048] (b) Case 2: When the SCS is 30 kHz, the subcarrier shift = = =2 → The subcarrier position needs to be offset by 2 subcarriers. The decimal part is the residual Doppler frequency offset estimated by the communication device (i.e., UE).

[0049] According to one embodiment, method 100 further includes: to achieve cell synchronization, the communication device correlates the received DL signal, including partially pre-compensated SSBs, with a locally generated set of PSS waveforms, wherein each PSS waveform has a possible value for a residual portion of the Doppler frequency offset that is not compensated by the partial pre-compensation of the NGSO satellite transmitter; and determines the maximum correlation value. The PSS and SSS in the partially pre-compensated SSBs are compensated by the NGSO satellite transmitter to compensate for the integer portion of the Doppler frequency offset. This further enables the communication device (i.e., the UE) to determine the start and end points of the SSBs in the time domain solely by constructing locally generated and time-shifted versions of PSS and SSS templates, and correlates the received SSBs with the locally generated PSS and SSS in a computationally efficient manner, since no hypothesis testing is required in the frequency domain. The communication device (i.e., the UE) further determines the maximum correlation value by correlating the received DL signal with the locally generated set of PSS waveforms. If the communication device detects that the maximum correlation value is greater than a certain threshold, the communication device calculates the total Doppler frequency offset according to method 100.

[0050] According to one embodiment, method 100 further includes: if the maximum correlation value is less than a predefined threshold, the communication device achieves cell synchronization by correlating the DL signal with a locally generated set of larger PSS waveforms, wherein each PSS waveform is offset in frequency by a possible value of the maximum possible Doppler frequency offset related to the movement of the NGSO satellite transmitter relative to the coverage area of ​​the DL beam. In one case, if the maximum correlation value is less than the predefined threshold, the communication device needs to correlate the DL signal with a locally generated set of larger PSS waveforms offset in both time and frequency (i.e., a second set) to determine the total Doppler frequency offset.

[0051] According to one embodiment, method 100 further includes: after cell synchronization is achieved, the communication device detects the physical cell identity (PCI); and estimates the residual portion of the Doppler frequency offset based on the received PSS and SSS. After cell synchronization is achieved, the communication device (i.e., the UE) can use the same correlation technique to detect the timing boundary of the PSS and the residual portion of the Doppler frequency offset without much complex operation. In addition, the communication device (i.e., the UE) can detect the PCI by correlating the received PSS and SSS with three locally generated PSS sequences and 336 SSS sequences, respectively. Then, the communication device calculates the PCI according to equation (2): (2) in, It is the SSS ID. It is a PSS ID.

[0052] According to one embodiment, method 100 further includes: the communication device determining the value of partial pre-compensation for Doppler frequency offset performed by the NGSO satellite transmitter based on the difference between the center frequencies of the subcarriers of the received PSS and SSS and the received demodulation reference signal (DMRS) of the physical broadcast channel (PBCH) within the partially pre-compensated SSB. The communication device determines the set of all possible PBCH DMRS subcarrier positions within the received partially pre-compensated SSB based on the detected PCI and the maximum permissible pre-compensation value (e.g., ±9). No frequency offset is applied to the PBCH and all other physical channels. The DMRS of the PBCH can be used to detect the frequency pre-compensation applied to the PSS and SSS by the NGSO satellite transmitter. The DMRS of the PBCH can be combined with hypothesis testing to detect the actual PSS and SSS frequency offsets. Where –Nmax≤N≤Nmax, Nmax≤9 are network-specific parameters that the communication device (i.e., UE) can know in advance.

[0053] According to one embodiment, method 100 further includes: the communication device determining a value of Doppler frequency offset related to the movement of the NGSO satellite transmitter relative to the coverage area of ​​the DL beam, based on an estimated residual portion of the Doppler frequency offset and a determined value of partial pre-compensation for the Doppler frequency offset. The communication device (i.e., the UE) determines the value of the Doppler frequency offset (i.e., the total Doppler frequency offset) based on detected PSS and SSS subcarrier offsets and the estimated residual portion of the Doppler frequency offset. PBCH DMRS subcarrier offsets are also used to determine the value of the Doppler frequency offset.

[0054] According to one embodiment, method 100 further includes: the communication device compensating for phase distortion of a DL data signal associated with a DL beam using a determined value of the Doppler frequency offset, wherein the DL data signal includes a Physical Downlink Control Channel (PDCCH) signal or a Physical Downlink Shared Channel (PDSCH) signal. In addition to compensating for phase distortion of the DL data signal including the PDCCH or PDSCH signal, the determined value of the Doppler frequency offset is also used to improve the spectral efficiency of the DL data signal. In one implementation scenario, the determined value of the Doppler frequency offset can also be used to improve the spectral efficiency of other communication channels such as the Physical Uplink Shared Channel (PUSCH) or the Physical Uplink Control Channel (PUCCH).

[0055] According to one embodiment, method 100 further includes: if the PCI detected based on the received PSS and SSS belongs to a predefined identifier set, the communication device determines that partial pre-compensation for Doppler frequency offset is applied to the DL signal by the NGSO satellite transmitter. Based on the detected PCI, the communication device determines whether the NGSO satellite transmitter applies partial pre-compensation for Doppler frequency offset to the DL signal. Partial pre-compensation for Doppler frequency offset is applied to PCIs belonging to a certain ID set (such as a first set); otherwise, the PCI belongs to another ID set (such as a second set) where partial pre-compensation for Doppler frequency offset is not applied. For example, even-numbered PCIs correspond to the application of partial pre-compensation for Doppler frequency offset, and odd-numbered PCIs correspond to the non-application of partial pre-compensation for Doppler frequency offset.

[0056] According to one embodiment, method 100 further includes: the communication device determining the SCS ratio between the Physical Random-Access Channel (PRACH) signal and the SCS used in the partially pre-compensated SSB; pre-offsetting the PRACH subcarrier position in the PRACH signal by a value, wherein the value is defined by a determined value of the partially pre-compensated Doppler frequency offset and the determined SCS ratio; and transmitting the pre-offset PRACH signal to the NGSO satellite transmitter. In one implementation scenario, partial subcarrier offsets of the PSS and SSS applied by the NGSO satellite transmitter are detected, and the communication device uses these offsets to determine the SCS ratio between the PRACH signal and the SCS used in the partially pre-compensated SSB. Subsequently, the communication device pre-offsets the PRACH subcarrier position using the detected partially pre-compensated PSS and SSS Doppler frequency offsets and the SCS ratio between the partially pre-compensated SSB and the PRACH signal. Since the NGSO satellite transmitter is aware of the detected subcarriers after PSS and SSS Doppler frequency offset pre-compensation, the NGSO satellite transmitter is also aware of the PRACH subcarrier offset.

[0057] Therefore, Method 100 achieves partial Doppler frequency offset pre-compensation by pre-offsetting the positions of the PSS and SSS subcarriers within the existing empty subcarrier region within the SSB. Thus, the NR parameter set in the transmitted signal is preserved because the PSS and SSS subcarriers remain on the predefined frequency grid. Furthermore, spectral efficiency is maintained because the offset is performed within the existing empty subcarrier region. Moreover, Method 100 achieves a simplified cell synchronization mechanism even if the high mobility of LEO satellites leads to a large Doppler frequency offset. Furthermore, Method 100 can determine the absolute Doppler frequency offset information by measuring the relative frequency spacing between the partially Doppler frequency offset pre-compensated PSS and SSS within the same SSB and the uncompensated PBCH DMRS. Therefore, no additional control signaling is required to indicate the absolute Doppler frequency offset value to the communication device (i.e., the UE). In addition, method 100 includes partial Doppler frequency offset pre-compensation by means of the detected partial Doppler frequency offset pre-compensation based on PSS and SSS, offsetting the PRACH subcarrier position so that the NR parameter set of the transmitted signal remains unchanged.

[0058] Steps 102 and 104 are merely illustrative, and other alternatives may be provided without departing from the scope of the claims herein, such as adding one or more steps, deleting one or more steps, or providing one or more steps in a different order.

[0059] In one aspect, a computer program product including program instructions is provided. When executed by one or more processors in a system, the program instructions are used to perform method 100. In another aspect, this application provides a non-transitory computer-readable medium storing computer implementation instructions. When executed by a computer, the computer implementation instructions cause the computer to perform the operation of method 100.

[0060] Figure 2 A communication device for cell synchronization in a non-Geostationary Orbit (NGSO) satellite mobile communication system is shown according to one embodiment of this application. Figure 2 Combination Figure 1 The elements within are described. (See reference.) Figure 2 This diagram illustrates a communication device 202 for cell synchronization in a non-Geostationary Orbit (NGSO) satellite mobile communication system 200. The communication device 202 receives a partially pre-compensated synchronization signal block (SSB) 204 from an NGSO satellite transmitter 208 via a downlink (DL) beam 206. The partially pre-compensated SSB 204 includes a primary synchronization signal (PSS) 210, a secondary synchronization signal (SSS) 212, and a physical broadcast channel (PBCH) 213. Furthermore, the communication device 202 includes an antenna 214, a memory 216, and a processor 218. The communication device 202 is used to perform ( Figure 1 Method 100.

[0061] Communication device 202 is used to receive partially pre-compensated SSB 204 from NGSO satellite transmitter 208 via DL beam 206. Examples of communication device 202 may include, but are not limited to, smartphones with NTN direct access capability, smartphones suitable for high mobility scenarios, receiving devices, custom hardware for wireless communication, or any other portable or non-portable electronic devices, etc.

[0062] Antenna 214 may include suitable logic, circuitry, interfaces, and / or code for receiving partially pre-compensated SSB 204 from NGSO satellite transmitter 208 via DL beam 206. Examples of antenna 214 may include, but are not limited to, radio frequency transceivers, network interfaces, telematics units, or any antenna suitable for user equipment, repeaters, base stations, or other portable or non-portable communication devices.

[0063] Memory 216 may include suitable logic, circuitry, interfaces, and / or code for storing machine code and / or instructions executable by processor 218. Examples of implementations of memory 216 may include, but are not limited to, electrically erasable programmable read-only memory (EEPROM), random access memory (RAM), read-only memory (ROM), hard disk drive (HDD), flash memory, secure digital card (SD), solid-state drive (SSD), computer-readable storage media, and / or CPU cache memory. Memory 216 may store an operating system and / or computer program product for operating communication device 202. Computer-readable storage media used to provide non-transitory memory may include, but are not limited to, electronic storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any suitable combination of the foregoing.

[0064] Processor 218 may include suitable logic, circuitry, interfaces, and / or code for executing instructions stored in memory 216. Examples of processor 218 may include, but are not limited to, integrated circuits, coprocessors, microprocessors, microcontrollers, complex instruction set computing (CISC) processors, application-specific integrated circuit (ASIC) processors, reduced instruction set (RISC) processors, very long instruction word (VLIW) processors, central processing units (CPUs), state machines, data processing units, and other processors or circuits. Furthermore, processor 218 may refer to one or more separate processors, processing devices, or processing units as part of a machine.

[0065] During operation, communication equipment 202 is used to receive partially pre-compensated SSB 204 from NGSO satellite transmitter 208 via DL beam 206. Communication equipment 202 is also used to achieve cell synchronization with NGSO satellite transmitter 208 using the partially pre-compensated SSB 204, wherein the center frequencies of PSS 210 and SSS 212 within the partially pre-compensated SSB 204 are pre-offset by an integer number of subcarriers relative to the center frequencies of the partially pre-compensated SSB 204 by NGSO satellite transmitter 208 to achieve partial pre-compensation for Doppler frequency offset related to the movement of the coverage area of ​​NGSO satellite transmitter 208 relative to DL beam 206 on Earth. Communication equipment 202 is used to partially pre-compensate for the Doppler frequency offset by offsetting the subcarriers of PSS 210 and SSS 212 within existing empty subcarrier areas within the SSB, which has already been... Figure 1 This is described in detail elsewhere. Therefore, communication device 202 can easily detect PSS210 and SSS212 with low complexity. After detecting PSS210 and SSS212, communication device 202 can calculate PCI in a simplified manner. Furthermore, the transmitted signal conforms to the NR parameter set.

[0066] According to one embodiment, the center frequencies of PSS210 and SSS212 are pre-offset by an integer number of subcarriers within the partially pre-compensated SSB204 based on the orbital altitude and velocity of the NGSO satellite transmitter 208, the coverage area of ​​the DL beam 206, the carrier frequency of the DL channel, and the subcarrier spacing (SCS) of the partially pre-compensated SSB204. The absolute value of the Doppler frequency offset of the DL beam 206 within the coverage area of ​​the NGSO satellite transmitter 208 is based on the orbital altitude and velocity of the NGSO satellite transmitter 208, the DL band, the carrier frequency, and the beam position within the coverage area of ​​the NGSO satellite transmitter 208.

[0067] According to one embodiment, the center frequencies of PSS210 and SSS212 are pre-offset in the range of -9 to +9 subcarriers within the partially pre-compensated empty subcarrier region of SSB204. SSS212 has 9 unused subcarriers above and 9 unused subcarriers below, for a total of 18 unused subcarriers. Therefore, the center frequencies of PSS210 and SSS212 are pre-offset in the range of -9 to +9 within the partially pre-compensated empty subcarrier region of SSB204, which has already... Figure 1 This is described in detail in [etc.].

[0068] According to one embodiment, the communication device 202 is further configured to achieve cell synchronization by: correlating the received DL signal, including the partially pre-compensated SSB 204, with a locally generated set of PSS waveforms, wherein each PSS waveform represents a possible value of a residual portion of the Doppler frequency offset that has not been compensated for by the partial pre-compensation of the NGSO satellite transmitter 208; and determining the maximum correlation value. In one implementation scenario, the communication device 202 assumes that the NGSO satellite transmitter 208 applies partial pre-compensation for the Doppler frequency offset. Subsequently, the communication device 202 continues to determine the SSB timing boundary by correlating the received DL signal with the locally generated set of PSS waveforms (or local PSS templates). If the communication device 202 detects that the PSS peak value is greater than a certain threshold, the communication device 202 then determines the SSB timing boundary according to (…). Figure 1 Method 100 calculates the total Doppler frequency offset.

[0069] According to one embodiment, the communication device 202 is further configured to: if the maximum correlation value is less than a predefined threshold, achieve cell synchronization by correlating the DL signal with a locally generated set of larger PSS waveforms, wherein each PSS waveform is offset in frequency by a possible value of the maximum possible Doppler frequency offset related to the movement of the NGSO satellite transmitter 208 relative to the coverage area of ​​the DL beam 206. In one case, if the maximum correlation value is less than the predefined threshold, the communication device 202 needs to correlate the DL signal with a locally generated set of larger PSS waveforms offset in both time and frequency (i.e., a second set) to determine the total Doppler frequency offset.

[0070] According to one embodiment, the communication device 202 is further configured to: detect the physical cell identity (PCI) after cell synchronization is achieved; and estimate the residual portion of the Doppler frequency offset based on the received PSS and SSS. The communication device 202 is configured to detect the PCI and estimate the residual portion of the Doppler frequency offset based on PSS 210 and SSS 212, which has already been implemented... Figure 1 This is described in detail in [etc.].

[0071] According to one embodiment, communication device 202 is used to determine the value of partial pre-compensation for Doppler frequency offset performed by NGSO satellite transmitter 208 based on the difference between the center frequencies of the subcarriers of the received PSS and SSS and the received demodulation reference signal (DMRS) of the physical broadcast channel (PBCH) 213 within the partially pre-compensated SSB 204. Communication device 202 is also used to determine a set of all possible PBCH DMRS subcarrier positions within the partially pre-compensated SSB 204 based on the detected PCI and the maximum permissible pre-compensation value (e.g., ±9). Communication device 202 is further used to extract the PBCH DMRS subcarriers at each possible position within this set from the partially pre-compensated SSB 204 and correlate the extracted PBCH DMRS subcarriers with a locally generated DMRS sequence.

[0072] According to one embodiment, the communication device 202 is further configured to determine a value of Doppler frequency offset related to the movement of the coverage area of ​​the NGSO satellite transmitter 208 relative to the DL beam 206, based on an estimated residual portion of the Doppler frequency offset and a determined value of partial pre-compensation for the Doppler frequency offset. The communication device 202 is configured to determine the value of the Doppler frequency offset (i.e., the total Doppler frequency offset) based on detected PSS and SSS subcarrier offsets and an estimated residual portion of the Doppler frequency offset.

[0073] According to one embodiment, the communication device 202 is further configured to compensate for phase distortion of DL data signals associated with DL beam 206 using a determined value of Doppler frequency offset, wherein the DL data signals include Physical Downlink Control Channel (PDCCH) signals or Physical Downlink Shared Channel (PDSCH) signals. In one implementation scenario, the communication device 202 is configured to use the determined value of Doppler frequency offset to improve the spectral efficiency of other communication channels such as Physical Uplink Shared Channel (PUSCH) or Physical Uplink Control Channel (PUCCH).

[0074] According to one embodiment, the communication device 202 is further configured to: determine that partial pre-compensation for Doppler frequency offset is applied to the DL signal by the NGSO satellite transmitter 208 if the PCI detected based on the received PSS and SSS belongs to a predefined identifier set. The communication device 202 is configured to determine whether the NGSO satellite transmitter 208 applies partial pre-compensation for Doppler frequency offset to the DL signal based on the detected PCI, which has already been implemented. Figure 1 This is described in detail in [etc.].

[0075] According to one embodiment, the communication device 202 is further configured to: determine the SCS ratio between the Physical Random Access Channel (PRACH) signal and the SCS used in the partially pre-compensated SSB 204; pre-offset the PRACH subcarrier position in the PRACH signal by a value, wherein the value is defined by the determined value of the partially pre-compensated Doppler frequency offset and the determined SCS ratio; and transmit the pre-offset PRACH signal to the NGSO satellite transmitter 208. In one implementation scenario, the PSS and SSS partial subcarrier offsets applied by the NGSO satellite transmitter 208 are detected, and the communication device 202 uses this offset to determine the SCS ratio between the PRACH signal and the SCS used in the partially pre-compensated SSB 204, which has already been... Figure 1 This is described in detail in [etc.].

[0076] Therefore, communication device 202 achieves partial Doppler frequency offset precompensation by offsetting the positions of PSS210 and SSS212 subcarriers within the existing empty subcarrier region of the SSB, while maintaining the NR parameter set in the transmitted signal. This is because the PSS210 and SSS212 subcarriers still lie on a predefined frequency grid.

[0077] Figure 3 An NGSO satellite transmitter according to one embodiment of this application is shown. Figure 3 Combination Figure 1 and Figure 2 The elements within are described. (See reference.) Figure 3 The diagram 300 shows a block diagram of an NGSO satellite transmitter 302. The NGSO satellite transmitter 302 includes an antenna 304, a memory 306, and a processor 308.

[0078] NGSO satellite transmitter 302 corresponds to ( Figure 2 NGSO satellite transmitter 208. NGSO satellite transmitter 302 is used to perform ( Figure 1 Method 100. Examples of NGSO satellite transmitters 302 may include, but are not limited to, onboard base stations (such as gNodeB, gNB), base stations suitable for high mobility scenarios (such as gNB), transceivers, LEO satellites, etc.

[0079] Antenna 304 may include suitable logic, circuitry, interfaces, and / or code for transmitting partially pre-compensated SSBs within the coverage area of ​​the DL beam. Examples of antenna 304 may include, but are not limited to, radio frequency transceivers, network interfaces, telematics units, or any antenna suitable for base stations, repeaters, or other portable or non-portable communication devices.

[0080] Memory 306 may include suitable logic, circuitry, interfaces, and / or code for storing machine code and / or instructions executable by processor 308. Examples of implementations of memory 306 may include, but are not limited to, electrically erasable programmable read-only memory (EEPROM), random access memory (RAM), read-only memory (ROM), hard disk drive (HDD), flash memory, secure digital card (SD), solid-state drive (SSD), computer-readable storage media, and / or CPU cache memory. Memory 306 may store an operating system and / or computer program product for operating NGSO satellite transmitter 302. Computer-readable storage media used to provide non-transitory memory may include, but are not limited to, electronic storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any suitable combination of the foregoing.

[0081] Processor 308 may include suitable logic, circuitry, interfaces, and / or code for executing instructions stored in memory 306. Examples of processor 308 may include, but are not limited to, integrated circuits, coprocessors, microprocessors, microcontrollers, complex instruction set computing (CISC) processors, application-specific integrated circuit (ASIC) processors, reduced instruction set (RISC) processors, very long instruction word (VLIW) processors, central processing units (CPUs), state machines, data processing units, and other processors or circuitry. Furthermore, processor 308 may refer to one or more separate processors, processing devices, or processing units as part of a machine.

[0082] During operation, NGSO satellite transmitter 302 is used to determine a partially pre-compensated value for the Doppler frequency offset related to the movement of NGSO satellite transmitter 302 relative to the coverage area of ​​the downlink (DL) beam on Earth. NGSO satellite transmitter 302 determines the partially pre-compensated value for the Doppler frequency offset to achieve cell synchronization with communication equipment (such as communication equipment 202). The partially pre-compensated value for the Doppler frequency offset is related to the movement of NGSO satellite transmitter 302 relative to the DL beam (such as... Figure 2 The coverage range of the DL beam 206 on Earth is related to movement.

[0083] The NGSO satellite transmitter 302 is also used to pre-offset the center frequency of the primary synchronization signal (PSS) and the center frequency of the secondary synchronization signal (SSS) within the synchronization signal block (SSB) relative to the center frequency of the SSB by a predetermined value corresponding to the determined value of the partial pre-compensation for the Doppler frequency offset, to obtain a partially pre-compensated SSB. The NGSO satellite transmitter 302 will then pre-offset the PSS (such as...) to an integer number of subcarriers corresponding to a predetermined value of the pre-offset and partial pre-compensation for the Doppler frequency offset. Figure 2 PSS210) and SSS (such as Figure 2 The center frequency of the SSB (SSS212) is pre-shifted to the empty subcarrier region within the SSB to obtain a partially pre-compensated SSB (i.e., Figure 2 (SSB204 after partial pre-compensation).

[0084] NGSO satellite transmitter 302 is also used to transmit partially pre-compensated SSBs within the coverage area of ​​the DL beam. NGSO satellite transmitter 302 will also transmit partially pre-compensated SSBs to communication equipment on Earth (such as...). Figure 2 Communication equipment 202).

[0085] According to one embodiment, the center frequencies of the PSS and SSS are pre-offset by an integer number of subcarriers within the partially pre-compensated SSB based on the orbital altitude and velocity of the NGSO satellite transmitter 302, the coverage area of ​​the DL beam, the carrier frequency of the DL channel, and the subcarrier spacing (SCS) of the partially pre-compensated SSB. The pre-offset of the center frequencies of the PSS and SSS within the partially pre-compensated SSB depends on a variety of factors, which have already been... Figure 1 This is described in detail in [etc.].

[0086] According to one embodiment, the center frequencies of the PSS and SSS are pre-offset in the empty subcarrier region of the partially pre-compensated SSB by a range of -9 to +9 subcarriers.

[0087] According to one embodiment, the NGSO satellite transmitter 302 is further configured to select a physical cell identity (PCI) for the DL channel from a predefined set of identifiers to indicate the application of partial pre-compensation for Doppler frequency offset to the DL signal. The selection of a PCI for the DL channel from the predefined set of identifiers is already... Figure 1 This is described in detail in [etc.].

[0088] Figure 4 This is a flowchart of a method for cell synchronization in an NGSO satellite mobile communication system according to another embodiment of this application. Figure 4 Combination Figure 1 , Figure 2 and Figure 3 The elements within are described. (See reference.) Figure 4 This illustrates a method 400 for cell synchronization in an NGSO satellite mobile communication system. Method 400 includes steps 402 to 406. Method 400 is composed of ( Figure 3 The NGSO satellite transmitter 302 was used for execution.

[0089] In step 402, method 400 includes: the NGSO satellite transmitter determining a partially pre-compensated value for the Doppler frequency offset related to the movement of the NGSO satellite transmitter relative to the coverage area of ​​the DL beam on Earth. Based on the NGSO satellite transmitter (e.g., Figure 3The motion of the NGSO satellite transmitter 302 determines the value of partial pre-compensation for the Doppler frequency offset, which can be used in LEO satellite mobile communication systems (such as...). Figure 2 Fast cell synchronization in the NGSO satellite mobile communication system (200).

[0090] In step 404, method 400 further includes: the NGSO satellite transmitter pre-offsets the center frequency of the primary synchronization signal (PSS) and the center frequency of the secondary synchronization signal (SSS) within the synchronization signal block (SSB) relative to the center frequency of the SSB by an integer number of subcarriers corresponding to a determined value of partial pre-compensation for the Doppler frequency offset, to obtain a partially pre-compensated SSB. The PSS (e.g., Figure 2 PSS210) and SSS (such as Figure 2 The center frequency of the SSB (SSS212) is pre-shifted to the empty subcarrier region within the SSB to obtain a partially pre-compensated SSB (i.e., Figure 2 The partially pre-compensated SSB204 has already been Figure 1 and Figure 2 This is described in detail in [etc.].

[0091] In step 406, method 400 further includes: the NGSO satellite transmitter transmitting a partially pre-compensated SSB within the coverage area of ​​the DL beam. The partially pre-compensated SSB (i.e. Figure 2 The partially pre-compensated SSB204 was transmitted via the NGSO satellite transmitter (i.e. Figure 3 The NGSO satellite transmitter 302) in the DL beam (such as Figure 2 It is transmitted to Earth within the coverage area of ​​the DL beam 206.

[0092] According to one embodiment, method 400 further includes: the NGSO satellite transmitter selecting a physical cell identity (PCI) for the DL channel from a predefined set of identifiers to indicate the application of partial pre-compensation for Doppler frequency offset to the DL signal. Selecting a PCI for the DL channel from the predefined set of identifiers has already been implemented. Figure 1 This is described in detail in [etc.].

[0093] Steps 402 to 406 are merely illustrative, and other alternatives may be provided without departing from the scope of the claims herein, such as adding one or more steps, deleting one or more steps, or providing one or more steps in a different order.

[0094] In one aspect, a computer program product comprising program instructions is provided. When said program instructions are processed by one or more processors in a system (such as...) Figure 3 When executed by the processor 308 in the NGSO satellite transmitter 302, the program instructions are used to perform method 400. In another aspect, this application provides a non-transitory computer-readable medium storing computer-implemented instructions. When executed by a computer, the computer-implemented instructions cause the computer to perform the operation of method 400.

[0095] Figure 5 A synchronization signal block (SSB) comprising a primary synchronization signal (PSS) and a secondary synchronization signal (SSS) offset by frequency subcarriers is shown according to one embodiment of the present application. Figure 5 Combination Figure 1 , Figure 2 , Figure 3 and Figure 4 The elements within are described. (See reference.) Figure 5 The diagram illustrates an NR SSB500 comprising PSS502, SSS504, and a Physical Broadcast Channel (PBCH) 506. PBCH506 includes multiple reference subcarriers 507. These multiple reference subcarriers 507 may also be referred to as the PBCH demodulation reference signal (DMRS). Multiple unused subcarriers 508 above and below SSS504 are also shown. The NR SSB500 is described in conjunction with the X-axis 510 and Y-axis 512.

[0096] NR SSB500, PSS502 and SSS504 correspond to respectively Figure 2The SSB204, PSS210, and SSS212 are partially pre-compensated. The X-axis 510 represents the Orthogonal Frequency Division Multiplexing (OFDM) symbols, ranging from 0 to 4. The Y-axis 512 represents the 20 resource blocks (RBs) spanning PBCH506. PSS502 and SSS504 can also be referred to as PSS and SSS with Doppler frequency offset pre-compensation, respectively. For NTN, the Doppler frequency offset varies for different satellite downlink beams; therefore, beam-specific Doppler frequency offset pre-compensation is performed on PSS502 and SSS504 to accelerate cell detection. In Doppler frequency offset pre-compensation, only the integer portion of the Doppler frequency offset is pre-compensated for PSS502 and SSS504. This is equivalent to shifting multiple unused subcarriers 508 (i.e., PSS / SSS subcarriers) into the empty subcarrier region within the NR SSB500. Therefore, the transmitted signal still conforms to the NR parameter set. Furthermore, the UE can detect the PSS and SSS (i.e., PSS502 and SSS504) after frequency subcarrier offset with low computational complexity. After detecting PSS502 and SSS504, the UE can estimate the residual portion of the Doppler frequency offset and calculate the PCI. Based on the detected PCI, the UE calculates the position of the PBCH DMRS symbol in the PBCH506 block according to 3GPP TS38.211. However, due to partial pre-compensation for the Doppler frequency offset, PSS502 and SSS504 are no longer centered on NR SSB500, therefore the UE needs to perform hypothesis testing to determine the relative positions of the PBCH DMRS with PSS502 and SSS504 in the frequency domain. The steps of the hypothesis testing are described below: (a) The UE needs to estimate the residual Doppler frequency offset during the initial cell search process.

[0097] (b) The UE also needs to calculate the PCI based on the detection results of the frequency pre-compensated PSS and SSS (i.e., PSS502 and SSS504).

[0098] (c) Based on the calculated PCI, the UE needs to extract DMRS from PBCH506.

[0099] (d) Due to the value of absolute Doppler frequency offset precompensation (in, (Unknown, UE still needs to extract) 10 possible DMRS PBCH sequences, of which 100,0 ... These are network-specific parameters known to the UE. The upper limit is 9 subcarriers because a typical SSS in the third OFDM symbol has a total of 18 subcarriers (9 above and 9 below). This corresponds to the maximum pre-compensable Doppler frequency offset, which needs to be taken into account when designing satellite constellations and coverage areas.

[0100] (e) By Replace with Extract additional sequences.

[0101] (f) The UE needs to use predefined metrics. Received Signal Received Power (RSRP), related peak values, etc., for all possible Hypothesis testing was performed on DMRS PBCH sequences.

[0102] (g) The index of the highest DMRS PBCH sequence indicates the value estimated by equation (3) after residual Doppler frequency offset precompensation. .

[0103] (3) (h) Calculate the total Doppler frequency offset according to equation (4).

[0104] (4) Figure 6 This is a method for detecting absolute Doppler frequency offset using an SSB with partial Doppler frequency offset pre-compensation, according to one embodiment of the present application, in a user equipment (UE). Figure 6 Combination Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5 The elements within are described. (See reference.) Figure 6 The diagram illustrates a method 600 including steps 602 to 614. Method 600 is... Figure 2 The communication device 202 performs the method 600. The method 600 is performed by the UE (i.e., the communication device 202) to detect absolute Doppler frequency offset using a partially Doppler frequency offset pre-compensated SSB (i.e., a partially pre-compensated SSB 204).

[0105] In step 602, the UE receives and detects the OFDM timing boundary of the SSB by detecting the received PSS. Since the PSS (e.g., PSS210) and SSS (e.g., SSS212) within the SSB (i.e., the partially pre-compensated SSB204) are compensated for the integer part of the Doppler frequency offset, the UE can determine the timing boundary of the SSB simply by constructing locally generated and time-shifted versions of PSS and SSS templates, and then correlates the received SSB with the locally generated PSS and SSS waveforms in a computationally efficient manner. Furthermore, no hypothesis testing is required in the frequency domain.

[0106] In step 604, the UE determines the residual Doppler frequency offset based on the received PSS and SSS. The UE can employ correlation techniques to detect the timing boundary of the PSS and the residual Doppler frequency offset without requiring too many complex operations.

[0107] In step 606, the UE detects PCI based on the received PSS and SSS. The UE detects PCI by correlating the received PSS and SSS with locally generated 3-PSS and 336-SSS templates, respectively. Figure 1 This is described in detail in [etc.].

[0108] In step 608, the UE determines the set of all possible PBCH DMRS subcarrier locations within the received SSB based on the detected PCI and the maximum permissible pre-compensation value (i.e., ±9).

[0109] In step 610, the UE is configured to: extract the PBCH DMRS subcarriers at each possible location within the set determined in step 608 from the received SSB; and correlate the extracted PBCH DMRS subcarriers with a locally generated DMRS sequence. In this application, the UE is aware that the PSS and SSS have undergone partial Doppler frequency offset compensation, which means that the PBCH DMRS locations extracted based on the detected PCI may deviate from the original subcarrier locations. Therefore, the UE is configured to extract the original PBCH DMRS subcarriers using the determined PCI, and also extract the integer offset of the original subcarriers, where the offset is equal to the maximum possible offset allowed by the available empty subcarriers (±9). This results in a total of 2×9+1=19 hypothetical PBCH DMRS locations. For each hypothetical PBCH DMRS location, the UE extracts the PBCH DMRS and correlates it with the local DMRS sequence.

[0110] In step 612, the UE detects PSS and SSS subcarrier offsets by selecting one of the possible locations within the set determined in step 608 based on one or more indicators. Based on one or more indicators (such as correlation values, RSRP, etc.), the UE determines which possible extracted PBCH DMRS subcarrier locations have the correct PBCH DMRS. The difference between the subcarrier location in the received SSB and the subcarrier location specified in Table 7.4.3.1-1 of 3GPP TS38.211 corresponds to the difference in subcarrier location on the satellite (i.e.,...). Figure 2 The NGSO satellite transmitter (208) has a pre-compensated integer Doppler frequency offset. This allows the UE to independently calculate the pre-compensated value without requiring the satellite (i.e.,...). Figure 2 The NGSO satellite transmitter 208 sends explicit signaling to the UE.

[0111] In step 614, the UE determines the total absolute Doppler frequency offset based on the PSS and SSS subcarrier offsets detected in step 612 and the residual fractional Doppler frequency offset detected in step 604. The UE can determine the total Doppler frequency offset in a manner similar to equation (4) based on the residual Doppler frequency offset determined by the UE in step 604 and the PBCH DMRS subcarrier offset determined by the UE in step 612.

[0112] Figure 7 This is a flowchart illustrating a UE's method for determining whether a base station (BS) applies partial Doppler frequency offset pre-compensation without explicit signaling, according to one embodiment of this application. Figure 7 Combination Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 and Figure 6 The elements within are described. (See reference.) Figure 7 A flowchart 700 is shown, including operations 702 to 710. Flowchart 700 is composed of... Figure 2 The communication device 202 performs the operation. Flowchart 700 is used by the UE (i.e., the communication device 202) to determine whether the BS (i.e., the NGSO satellite transmitter 208 or network component or satellite) has applied partial Doppler frequency offset pre-compensation by performing operations 702 to 710.

[0113] In Operation 702, the UE assumes that the BS (or network component) is applying partial Doppler frequency offset pre-compensation. Subsequently, the UE continues to detect the PSS and SSS to determine the SSB timing boundary using a small set (or a first set) of local PSS templates.

[0114] In operation 704, the UE correlates the PSS and SSS subcarriers received within the partially pre-compensated SSB with a small set (or a first set) of local PSS templates by assuming that the frequency uncertainty corresponding to the maximum residual Doppler frequency offset value after partial pre-compensation is reduced.

[0115] In operation 706, the UE compares the relevant value (i.e., the PSS peak value) with a predefined threshold. If the relevant value is greater than the predefined threshold, operation 708 is executed. Otherwise, operation 710 is executed.

[0116] In operation 708, if the UE detects a relevant value greater than a predefined threshold, then the UE applies ( Figure 6 Method 600 is used to determine the total Doppler frequency offset.

[0117] In operation 710, if the UE fails to detect a correlation value greater than a predefined threshold, the UE assumes that the BS has not applied partial Doppler frequency offset pre-compensation. Therefore, the UE further correlates the PSS with a larger template set (or a second set) by assuming the frequency uncertainty corresponding to the maximum possible total Doppler frequency offset value in order to determine the total Doppler frequency offset.

[0118] In another embodiment, the BS can be used to indicate to the UE whether partial Doppler frequency offset pre-compensation is applied to the PSS and SSS. To enable the UE to decode the PBCH using the partially pre-compensated Doppler frequency offset PSS and SSS, the UE needs to be informed that the BS (such as a LEO BS or network component) has applied partial Doppler frequency offset pre-compensation. Since message passing between the network and the UE is not possible during the initial cell search phase, this can be achieved by embedding information into the PCI, which the UE detected by looking up the PSS and SSS IDs. Partial Doppler frequency offset pre-compensation is applied to PCIs belonging to a certain ID set (such as a first set); otherwise, the PCI belongs to a second set, which does not apply partial Doppler frequency offset pre-compensation. For example, even-numbered PCIs correspond to the application of partial Doppler frequency offset pre-compensation, and odd-numbered PCIs correspond to the non-application of partial Doppler frequency offset pre-compensation. For example: (a) First set: →If the detected PCI is within the set (i.e., even), then BS applies partial Doppler frequency offset precompensation.

[0119] (b) Second set: →If the detected PCI is within the set (i.e., odd), then BS does not apply partial Doppler frequency offset precompensation.

[0120] Figure 8This application describes a method for a UE to apply partial Doppler frequency offset precompensation to the Physical Random-Access Channel (PRACH) for uplink (UL) transmission, according to one embodiment of the present application. Figure 8 Combination Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 and Figure 7 The elements within are described. (See reference.) Figure 8 The diagram illustrates method 800, which includes steps 802 to 808. Method 800 is... Figure 2 The communication device 202 performs the method 800. The method 800 is used by the UE (i.e., the communication device 202) for partial Doppler frequency offset pre-compensation of the PRACH application.

[0121] In step 802, the UE is used to detect the PSS and SSS integer subcarrier offsets applied by the BS (i.e., NGSO satellite transmitter 208), such as Figure 1 and Figure 6 As stated above.

[0122] In step 804, the UE determines the SCS ratio between the PRACH format used and the SCS used by the received SSB.

[0123] In step 806, the UE uses the information obtained in steps 802 and 804 to offset the PRACH subcarrier position based on the detected pre-compensated PSS and SSS partial subcarrier offsets and the SCS ratio between the SSB and PRACH. Even with a large Doppler frequency offset, this operation makes it easier for the BS to detect the PRACH transmitted by the UE. Since the BS knows the detected pre-compensated PSS and SSS Doppler frequency offset partial subcarriers, it also knows the PRACH subcarrier offset. Therefore, even if the PRACH signal has undergone partial DS compensation, the BS can still determine the absolute DS value.

[0124] In step 808, the UE transmits the partially pre-compensated PRACH to the onboard BS.

[0125] Figure 9 An exemplary scenario of partial Doppler frequency offset precompensation of PRACH according to an embodiment of this application is shown. Figure 9 Combination Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 and Figure 8 The elements within are described. (See reference.) Figure 9 This illustrates an exemplary scenario 900 of PRACH partial Doppler frequency offset precompensation.

[0126] In exemplary scenario 900, assuming a Doppler frequency offset of +78 kHz, an SSB SCS of 30 kHz, and a PRACH SCS of 15 kHz, the UE needs to detect a subcarrier offset of –2 after PSS and SSS Doppler frequency offset pre-compensation. The UE also calculates a ratio of 2 between the SSB SCS and the PRACH SCS. Subsequently, the UE needs to offset the PRACH subcarrier position by –4 and transmit the partially pre-compensated PRACH to the BS.

[0127] Modifications to the embodiments of this application described above may be made without departing from the scope of the application as defined by the appended claims. Expressions such as “comprising,” “incorporated,” “having,” “is / are” used to describe and claim this application are intended to be interpreted in a non-exclusive manner, meaning that items, components, or elements not explicitly described may also be present. Singular references should also be interpreted to refer to the plural. The term “exemplary” as used herein means “as an example, instance, or illustration.” Any embodiment described as “exemplary” is not necessarily to be construed as more preferred or advantageous than other embodiments, and / or as excluding combinations of features of other embodiments. The term “optionally” as used herein means “provided in some embodiments and not in others.” It should be understood that certain features of this application described in the context of a single embodiment for clarity may also be provided in combination in a single embodiment. Conversely, various features of this application described in the context of a single embodiment for brevity may also be provided individually or in any suitable combination or, where appropriate, in any other described embodiment of this application.

Claims

1. A method (100) for cell synchronization in a non-Geostationary Orbit (NGSO) satellite mobile communication system (200), characterized in that, The method (100) includes: The communication equipment (202) receives a partially pre-compensated synchronization signal block (SSB) (204) from the NGSO satellite transmitter (208) via a downlink (DL) beam (206); and uses the partially pre-compensated SSB (204) to achieve cell synchronization with the NGSO satellite transmitter (208), wherein, The center frequencies of the primary synchronization signal (PSS) (210) and the secondary synchronization signal (SSS) (212) within the partially pre-compensated SSB (204) are pre-offset by an integer number of subcarriers relative to the center frequency of the partially pre-compensated SSB (204) by the NGSO satellite transmitter (208) to achieve partial pre-compensation of the Doppler frequency offset related to the movement of the NGSO satellite transmitter (208) relative to the coverage area of ​​the DL beam (206) on Earth.

2. The method (100) according to claim 1, characterized in that, The integer number of subcarriers whose center frequencies of the PSS (210) and SSS (212) are pre-offset within the partially pre-compensated SSB (204) are determined based on the orbital altitude and speed of the NGSO satellite transmitter (208), the coverage of the DL beam (206), the carrier frequency of the DL channel, and the subcarrier spacing (SCS) of the partially pre-compensated SSB (204).

3. The method (100) according to claim 1 or 2, characterized in that, The center frequencies of the PSS (210) and the SSS (212) are pre-offset in the range of -9 to +9 subcarriers within the empty subcarrier region of the partially pre-compensated SSB (204).

4. The method (100) according to any one of claims 1 to 3, characterized in that, Including: In order to achieve the cell synchronization, The communication device (202) correlates the received DL signal, including the partially pre-compensated SSB (204), with a locally generated set of PSS waveforms, wherein each PSS waveform is a possible value of a residual portion of the Doppler frequency offset that is not compensated by the partially pre-compensated portion of the NGSO satellite transmitter (208); and determines the maximum correlation value.

5. The method (100) according to claim 4, characterized in that, Also includes: If the maximum correlation value is less than a predefined threshold, the communication device (202) achieves cell synchronization by correlating the DL signal with a larger set of locally generated PSS waveforms, wherein each PSS waveform is offset in frequency by the maximum possible Doppler frequency offset value related to the movement of the NGSO satellite transmitter (208) relative to the coverage area of ​​the DL beam (206).

6. The method (100) according to claim 4 or 5, characterized in that, include: After achieving cell synchronization, the communication device (202) detects the physical cell identity (PCI); based on the received PSS (210) and SSS (212), it estimates the residual portion of the Doppler frequency offset.

7. The method (100) according to claim 6, characterized in that, Also includes: The communication device (202) determines the value of the partial pre-compensation for the Doppler frequency offset performed by the NGSO satellite transmitter (208) based on the difference between the center frequencies of the subcarriers of the received PSS (210) and SSS (212) and the received demodulation reference signal (DMRS) of the physical broadcast channel (PBCH) (506) in the partially pre-compensated SSB (204).

8. The method (100) according to claim 7, characterized in that, Also includes: The communication device (202) determines the value of the Doppler frequency offset related to the movement of the NGSO satellite transmitter (208) relative to the coverage area of ​​the DL beam (206) based on the estimated residual portion of the Doppler frequency offset and the determined value of the partial pre-compensation of the Doppler frequency offset.

9. The method (100) according to claim 8, characterized in that, Also includes: The communication device (202) uses the determined value of the Doppler frequency offset to compensate for the phase distortion of the DL data signal associated with the DL beam (206), wherein the DL data signal includes a Physical Downlink Control Channel (PDCCH) signal or a Physical Downlink Shared Channel (PDSCH) signal.

10. The method (100) according to any one of claims 1 to 9, characterized in that, Also includes: If the PCI detected based on the received PSS (210) and SSS (212) belongs to a predefined identifier set, the communication device (202) determines that the partial pre-compensation of the Doppler frequency offset is applied to the DL signal by the NGSO satellite transmitter (208).

11. The method (100) according to any one of claims 1 to 10, characterized in that, Also includes: The communication device (202). Determine the SCS ratio between the Physical Random-Access Channel (PRACH) signal and the SCS used in the partially pre-compensated SSB (204); The position of the PRACH subcarrier in the PRACH signal is pre-offset by a value, wherein the value is defined by the determined value of the partial pre-compensation of the Doppler frequency offset and the determined SCS ratio; The pre-offset PRACH signal is transmitted to the NGSO satellite transmitter (208).

12. A communication device (202) for cell synchronization in a non-Geostationary Orbit (NGSO) satellite mobile communication system (200), characterized in that, The communication device (202) is used for: The partially pre-compensated synchronization signal block (SSB) (204) is received from the NGSO satellite transmitter (208) via the downlink (DL) beam (206). Cell synchronization is achieved using the partially pre-compensated SSB (204) and the NGSO satellite transmitter (208), wherein, The center frequencies of the primary synchronization signal (PSS) (210) and the secondary synchronization signal (SSS) (212) within the partially pre-compensated SSB (204) are pre-offset by an integer number of subcarriers relative to the center frequency of the partially pre-compensated SSB (204) by the NGSO satellite transmitter (208) to achieve partial pre-compensation of the Doppler frequency offset related to the movement of the NGSO satellite transmitter (208) relative to the coverage area of ​​the DL beam (206) on Earth.

13. The communication device (202) according to claim 12, characterized in that, The integer number of subcarriers whose center frequencies of the PSS (210) and SSS (212) are pre-offset within the partially pre-compensated SSB (204) are determined based on the orbital altitude and speed of the NGSO satellite transmitter (208), the coverage of the DL beam (206), the carrier frequency of the DL channel, and the subcarrier spacing (SCS) of the partially pre-compensated SSB (204).

14. The communication device (202) according to claim 12 or 13, characterized in that, The center frequencies of the PSS (210) and the SSS (212) are pre-offset in the range of -9 to +9 subcarriers within the empty subcarrier region of the partially pre-compensated SSB (204).

15. The communication device (202) according to any one of claims 12 to 14, characterized in that, Used to achieve cell synchronization in the following ways: The received DL signal, including the partially pre-compensated SSB (204), is correlated with a locally generated set of PSS waveforms, wherein each PSS waveform is a possible value of a residual portion of the Doppler frequency offset that is not compensated by the partially pre-compensated portion of the NGSO satellite transmitter (208). Determine the maximum correlation value.

16. The communication device (202) according to claim 15, characterized in that, It is also used to: if the maximum correlation value is less than a predefined threshold, Cell synchronization is achieved by correlating the DL signal with a large set of locally generated PSS waveforms, wherein each PSS waveform is offset in frequency by the maximum possible Doppler frequency offset value associated with the movement of the NGSO satellite transmitter (208) relative to the coverage area of ​​the DL beam (206).

17. The communication device (202) according to claim 15 or 16, characterized in that it is used for: after achieving cell synchronization, Detect the physical cell identity (PCI); based on the received PSS (210) and SSS (212), estimate the residual portion of the Doppler frequency offset.

18. The communication device (202) according to claim 17, characterized in that, Also used for: Based on the difference between the center frequencies of the subcarriers of the received PSS and SSS and the received demodulation reference signal (DMRS) of the physical broadcast channel (PBCH) (506) in the partially pre-compensated SSB (204), the value of the partial pre-compensation for the Doppler frequency offset performed by the NGSO satellite transmitter (208) is determined.

19. The communication device (202) according to claim 18, characterized in that, Also used for: Based on the estimated residual portion of the Doppler frequency offset and the determined value of the partial pre-compensation of the Doppler frequency offset, the value of the Doppler frequency offset related to the movement of the coverage area of ​​the NGSO satellite transmitter (208) relative to the DL beam (206) is determined.

20. The communication device (202) according to claim 19, characterized in that, Also used for: The determined value of the Doppler frequency offset is used to compensate for the phase distortion of the DL data signal associated with the DL beam (206), wherein the DL data signal includes a Physical Downlink Control Channel (PDCCH) signal or a Physical Downlink Shared Channel (PDSCH) signal.

21. The communication device (202) according to any one of claims 12 to 20, characterized in that, Also used for: If the PCI detected based on the received PSS (210) and SSS (212) belongs to a predefined identifier set, the partial pre-compensation of the Doppler frequency offset is determined to be applied to the DL signal by the NGSO satellite transmitter (208).

22. The communication device (202) according to any one of claims 12 to 21, characterized in that, Also used for: Determine the SCS ratio between the Physical Random-Access Channel (PRACH) signal and the SCS used in the partially pre-compensated SSB (204); The position of the PRACH subcarrier in the PRACH signal is pre-offset by a value, wherein the value is defined by the determined value of the partial pre-compensation of the Doppler frequency offset and the determined SCS ratio; The pre-offset PRACH signal is transmitted to the NGSO satellite transmitter (208).

23. A non-geostationary orbit (NGSO) satellite transmitter (208), characterized in that, Used for: Determine the value of the partial pre-compensation for the Doppler frequency offset related to the movement of the coverage area of ​​the NGSO satellite transmitter (208) relative to the downlink (DL) beam (206) on Earth; The center frequency (210) of the primary synchronization signal (PSS) and the center frequency (212) of the secondary synchronization signal (SSS) within the synchronization signal block (SSB) are pre-offset relative to the center frequency of the SSB by an integer number of subcarriers corresponding to the determined value of the partial pre-compensation of the Doppler frequency offset, so as to obtain the partially pre-compensated SSB (204). The partially pre-compensated SSB (204) is transmitted within the coverage area of ​​the DL beam (206).

24. The NGSO satellite transmitter (208) according to claim 23, characterized in that, The integer number of subcarriers whose center frequencies of the PSS (210) and SSS (212) are pre-offset within the partially pre-compensated SSB (204) are determined based on the orbital altitude and speed of the NGSO satellite transmitter (208), the coverage of the DL beam (206), the carrier frequency of the DL channel, and the subcarrier spacing (SCS) of the partially pre-compensated SSB (204).

25. The NGSO satellite transmitter (208) according to claim 23 or 24, characterized in that, The center frequencies of the PSS (210) and the SSS (212) are pre-offset in the range of -9 to +9 subcarriers within the empty subcarrier region of the partially pre-compensated SSB (204).

26. The NGSO satellite transmitter (208) according to any one of claims 23 to 25, characterized in that, Also used for: Select a physical cell identity (PCI) for the DL channel from a predefined set of identifiers to indicate the application of the partial pre-compensation for the Doppler frequency offset to the DL signal.

27. A method (400) for cell synchronization in a non-Geostationary Orbit (NGSO) satellite mobile communication system (200), characterized in that, The method (400) includes: The NGSO satellite transmitter (208) determines a partially pre-compensated value for the Doppler frequency offset related to the movement of the coverage area of ​​the NGSO satellite transmitter (208) relative to the downlink (DL) beam (206) on Earth; The NGSO satellite transmitter (208) pre-offsets the center frequency of the primary synchronization signal (PSS) (210) and the center frequency of the secondary synchronization signal (SSS) (212) within the synchronization signal block (SSB) relative to the center frequency of the SSB by an integer number of subcarriers corresponding to the determined value of the partial pre-compensation of the Doppler frequency offset, so as to obtain a partially pre-compensated SSB (204). The NGSO satellite transmitter (208) transmits the partially pre-compensated SSB (204) within the coverage area of ​​the DL beam (206).

28. The method (400) according to claim 27, characterized in that, Also includes: The NGSO satellite transmitter (208) selects a physical cell identity (PCI) for the DL channel from a predefined set of identifiers to indicate the application of the partial pre-compensation for the Doppler frequency offset to the DL signal.

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