Access method, communication system, terminal device and related apparatus

Abstract

The access method, the communication system, the terminal device and the related device provided by the embodiments of the present application relate to the technical field of communication. The method can be applied to a terminal device. In the case that GNSS of the terminal device is invalid, the terminal device can receive a first signal from a LEO satellite. The terminal device can initiate a first access attempt. The first access attempt adopts a first time delay and a first frequency shift for time-frequency pre-compensation of uplink. The first time delay and the first frequency shift are determined based on the first signal and / or a plurality of historical position information of the terminal device. The probability of failing to effectively pre-compensate the time delay and the frequency of the uplink due to the inability to determine the transmission time delay and the frequency shift between the terminal device and the LEO satellite can be reduced. In turn, the access success rate of the first access attempt can be improved.

Description

Technical Field

[0001] This application relates to the field of communication technology, and in particular to an access method, communication system, terminal equipment and related devices. Background Technology

[0002] Some terminal devices can access non-terrestrial networks (NTNs) to enable communication via NTNs.

[0003] In some implementations, the terminal device obtains its location information through a Global Navigation Satellite System (GNSS) and, based on this location information, determines the transmission delay and Doppler shift between the terminal device and satellites in the NTN network. The terminal device can then use the determined delay and Doppler shift to perform uplink time-frequency pre-compensation to achieve fast access to the NTN.

[0004] However, when the terminal device cannot obtain its location information via GNSS, the success rate of the terminal device accessing NTN is low, which may affect the user experience. Summary of the Invention

[0005] This application provides an access method, terminal device, and related apparatus, applicable to the field of communication technology. It can improve the success rate of terminal devices accessing NTN.

[0006] In a first aspect, embodiments of this application propose an access method, the method comprising: receiving a first signal from a satellite; initiating a first access attempt; the first access attempt employing a first delay and a first frequency shift for uplink time-frequency pre-compensation; the first delay and the first frequency shift being determined based on the first signal and / or multiple historical location information of the terminal device; wherein, the first signal can be used for communication.

[0007] Thus, the first delay and the first frequency shift can be understood as the transmission delay and frequency shift between the terminal device and the satellite, as determined by the terminal device. The first delay and the first frequency shift are determined based on the first signal and / or multiple historical location information of the terminal device. This allows for the determination of the first delay and the first frequency shift between the terminal device and the satellite, based on the satellite signal used for communication (such as the first signal) and / or multiple historical location information of the terminal device, even when the GNSS service of the terminal device fails and the location information of the terminal device cannot be determined based on the GNSS signal. This enables the terminal device to use the first delay and the first frequency shift for uplink time-frequency pre-compensation and to initiate the first access attempt. It reduces the probability of being unable to effectively pre-compensate uplink delay and frequency due to the inability to determine the transmission delay and frequency shift between the terminal device and the satellite because of GNSS service failure. Since the first delay and the first frequency shift are determined based on satellite signals (such as the first signal) and / or multiple historical location information of the terminal device, the accuracy of the delay and frequency shift determined by the terminal device can be improved. This can improve the success rate of the terminal device's first access attempt based on the first delay and the first frequency shift, and increase the success rate of the terminal device accessing the NTN where the satellite is located. The satellite signal, for example, is a first signal. The first signal, used for communication, can indicate that the satellite is a communication satellite, such as a satellite within the NTN. The access method of this embodiment can be applied to terminal devices.

[0008] In one possible implementation, the method further includes initiating a second access attempt if the first access attempt fails. The second access attempt uses the delay and frequency shift of a common location reference point (CNP) for uplink time-frequency pre-compensation. The CNP is selected from multiple CNPs of the satellite. The CNP is used for the access attempt. The CNP can be simply referred to as a reference point.

[0009] This allows for a second access attempt using the reference point's delay and frequency shift if the first access attempt fails. This reduces the probability of repeated failures when using the first delay and frequency shift after the first access attempt has failed, thus improving the success rate of subsequent access attempts after a failed first attempt.

[0010] In one possible implementation, the common location reference point used in the second access attempt is selected from multiple common location reference points in a reference point selection order, which indicates the order in which the distance between the common location reference point and the terminal device increases from smallest to largest.

[0011] In this way, the reference point selection order indicates the order in which the distance between the common location reference points and the terminal device increases, and the reference points selected in the second access attempt are selected according to this order. This allows the terminal device to preferentially select reference points that are closer to it for access attempts. The closer the reference point selected for the access attempt is to the terminal device, the smaller the residual delay, which reduces the probability of the residual delay exceeding the PRACH detection window, and thus reduces the probability of the satellite failing to receive the uplink signal sent by the terminal device. This improves the success rate of the satellite receiving the uplink signal sent by the terminal device, thereby improving the access success rate. This reduces the number of access attempts. The PRACH detection window can be referred to as the search range of the PRACH detection window.

[0012] In one possible implementation, the first signal includes reference point information for multiple common location reference points within the satellite's beam range; the reference point information is used to determine the selection order of the reference points.

[0013] This makes it easier for the terminal device to use the reference point information in the first signal to determine the order of reference point selection.

[0014] In one possible implementation, the first delay and the first frequency shift are the transmission delay and frequency shift between the terminal device and the satellite at the first moment. The reference point selection order is determined based on the first delay, the first frequency shift, and the second delay and second frequency shift of each of the multiple common location reference points at the first moment.

[0015] For example, before or after initiating the first access attempt, the terminal device may determine the reference point selection order based on the first delay, the first frequency shift, and the second delay and second frequency shift of each of the multiple common location reference points of the satellite at the first moment.

[0016] In this way, based on the first time delay, the first frequency shift, and the second time delay and second frequency shift of each of the multiple reference points of the satellite at the first moment, the reference point selection order for choosing a common location reference point from multiple common location reference points is determined. This provides richer parameters for multi-reference point selection, which can improve the accuracy of the reference point selection order, and thus improve the accuracy of reference point selection. The order represents the order in which the distance between the common location reference points and the terminal device increases. This allows the selection of reference points closer to the terminal device to be prioritized when selecting reference points according to this selection order. This reduces the probability of access failure caused by the residual time delay exceeding the PRACH detection window due to a large distance between the reference point and the terminal device, thereby improving the access success rate of access attempts based on reference point time-frequency pre-compensation.

[0017] In one possible implementation, the reference point selection order is determined as follows: The distances between the first coordinate point and the second coordinate point of each of multiple common location reference points in a coordinate system established by time delay and frequency shift are calculated. The first coordinate point of the common location reference point is determined based on the second time delay and the second frequency shift. The second coordinate point is determined based on the first time delay and the first frequency shift. The multiple common location reference points are sorted according to their distances to obtain a first sequence. The first sequence is used to indicate the reference point selection order. The common location reference points selected according to the reference point selection order can be selected sequentially according to the first sequence.

[0018] Thus, the distance between the first and second coordinate points of the reference point can be called the relative distance of the reference point relative to the UE, or simply the relative distance of the reference point. The first sequence can be obtained by sorting multiple reference points according to their relative distances. The actual distance between a reference point and the terminal device is positively correlated with the relative distance of that reference point. The larger the relative distance of a reference point, the larger the actual distance between the reference point and the terminal device. The smaller the relative distance of a reference point, the smaller the actual distance between the reference point and the terminal device. Therefore, the first sequence obtained by sorting multiple common location reference points by distance can be used to indicate the order of distances between the common location reference points and the terminal device from smallest to largest, so that the terminal device can sequentially select reference points from the multiple reference points in ascending order of distance to attempt access.

[0019] In one possible implementation, the multiple common location reference points include I common location reference points, where the first coordinate point of the i-th common location reference point is ( , The second coordinate point is (). The distance between the first and second coordinate points is the Euclidean distance between them. Where I is a positive integer, and i is the index of the common location reference point. Let i be the time delay axis coordinate value of the i-th common position reference point in the coordinate system. Let i be the frequency shift axis coordinate value of the i-th common position reference point in the coordinate system. It is obtained by normalizing the second time delay of the i-th common location reference point. It is obtained by normalizing the second frequency shift of the i-th common position reference point. Let the first time delay be the coordinate value of the time delay axis in the coordinate system. Let the first frequency shift be the frequency shift axis coordinate value in the coordinate system. It is obtained by normalizing the first time delay. It is obtained by normalizing the first frequency shift.

[0020] In this way, by normalizing the second time delay and the second frequency shift of the i-th common location reference point to obtain the first coordinate point of the i-th common location reference point, and by normalizing the first time delay and the first frequency shift to obtain the second coordinate point, the first coordinate point and the second coordinate point used for distance calculation can be within the same scale range. That is, the first coordinate point and the second coordinate point used for distance calculation are both standardized coordinate points, which can improve the accuracy of the distance calculated based on the first coordinate point and the second coordinate point, and thus improve the accuracy of the reference point selection order obtained by sorting by distance.

[0021] In one possible implementation, the reference point information may include a reference time and the time delay and frequency shift data of each of the multiple common location reference points at the reference time. The second time delay and second frequency shift of the i-th common location reference point at the first time are determined based on the time delay and frequency shift data of the i-th common location reference point and the first time. Here, i is the index of the common location reference point, and the second time delay and second frequency shift of the i-th common location reference point at the first time are positively correlated with the first duration from the reference time to the first time, and positively correlated with the time delay and frequency shift data of the i-th common location reference point.

[0022] This allows for the determination of the second time delay and second frequency shift of each common location reference point at a first time point, based on the time delay and frequency shift data of each reference point at a reference time. This enables the determination of the relative distance between each reference point and the terminal device based on its respective second time delay and second frequency shift.

[0023] In one possible implementation, the time delay data includes a first time advance (TA), the drift rate of the first TA, and the drift acceleration of the first TA; the frequency shift data includes a third frequency shift, the drift rate of the third frequency shift, and the drift acceleration of the third frequency shift. The i-th common position reference point is at the first time... Second delay Satisfying the formula:

[0024]

[0025] The i-th common location reference point at time T d1 Second frequency shift Satisfying the formula:

[0026]

[0027] in, For reference time, For the i-th common location reference point in The first TA at any moment For the i-th common location reference point in The drift rate of the first TA at time t. For the i-th common location reference point in The drift acceleration of the first TA at time moment, For the i-th common location reference point in The third frequency shift at time, For the i-th common location reference point in The drift rate of the third frequency shift at time t. For the i-th common location reference point in The drift acceleration of the third frequency shift at time t.

[0028] This allows for the determination of the second time delay and second frequency shift of each common location reference point at the first time moment, based on the first time transition (TA), the drift rate of the first TA, the drift acceleration of the first TA, the third frequency shift, the drift rate of the third frequency shift, and the drift acceleration of the third frequency shift at the reference time. This facilitates the determination of the relative distance between each reference point and the terminal device based on their respective second time delay and second frequency shift.

[0029] In one possible implementation, if the first access attempt fails, a second access attempt is initiated, including: first, initiating a second access attempt using the delay and frequency shift of the first reference point for uplink time-frequency pre-compensation; and second, if the first second access attempt fails, initiating a second access attempt again using the delay and frequency shift of the second reference point for uplink time-frequency pre-compensation. The first and second reference points are selected sequentially from multiple common location reference points according to the reference point selection order, and the distance between the first reference point and the terminal device is less than the distance between the second reference point and the terminal device.

[0030] In this way, if the first access attempt fails, reference points are selected sequentially from multiple satellite reference points according to the reference point selection order, and a second access attempt is made accordingly. The distance between the first reference point and the terminal device is less than the distance between the second reference point and the terminal device. This means that the distance between the reference point used in the earlier second access attempt and the terminal device is smaller than the distance used in the later second access attempt, resulting in a higher success rate for the earlier second access attempt. If the earlier second access attempt based on the first reference point is successful, there is no need to make a second access attempt based on the second reference point, reducing the number of access attempts and enabling the terminal device to quickly access the satellite and achieve satellite communication. Rapid satellite access for the terminal device can be understood as the terminal device accessing the NTN where the satellite is located.

[0031] In one possible implementation, if the first access attempt fails, initiating a second access attempt further includes: if the second access attempt fails again, initiating yet another second access attempt, where the second access attempt uses the delay and frequency shift of the third reference point for uplink time-frequency pre-compensation. The first, second, and third reference points are selected sequentially from multiple common location reference points in the order of reference point selection, and the distance between the second reference point and the terminal device is less than the distance between the third reference point and the terminal device.

[0032] In this way, the distance between the second reference point and the terminal device is less than the distance between the third reference point and the terminal device. This means that the distance between the reference point used in the earlier second access attempt and the terminal device is smaller than the distance used in the later second access attempt, resulting in a higher success rate for the earlier second access attempt. If the earlier second access attempt based on the second reference point is successful, there is no need to perform a second access attempt based on the third reference point, which reduces the number of access attempts and facilitates faster satellite access for the terminal device to achieve satellite communication.

[0033] In one possible implementation, multiple historical location information corresponds to multiple historical moments. The first delay and the first frequency shift are the transmission delay and frequency shift between the terminal device and the satellite corresponding to the first moment. The first delay and the first frequency shift are determined as follows: Based on the first signal, a third delay and a fourth frequency shift are determined. Based on multiple historical location information, a fourth delay and a fifth frequency shift corresponding to the first moment are determined. It is determined whether the Reference Signal Received Power (RSRP) of the first signal is less than a first threshold, and whether the second duration from the latest historical moment to the first moment is less than a second threshold. If the RSRP is less than the first threshold and the second duration is less than the second threshold, the first delay is determined to be the fourth delay, and the first frequency shift is determined to be the fifth frequency shift. If the RSRP is greater than or equal to the first threshold, and / or the second duration is greater than or equal to the second threshold, the first delay is determined to be the third delay, and the first frequency shift is determined to be the fourth frequency shift.

[0034] This allows for the estimation of time delay and frequency shift between the terminal device and the satellite based on satellite signals (such as the first signal), e.g., the third time delay and the fourth frequency shift. Based on multiple historical location information of the terminal device, the time delay and frequency shift between the terminal device and the satellite can be predicted, e.g., the fourth time delay and the fifth frequency shift. RSRP < the first threshold indicates that the signal strength of the first signal is low, and the accuracy of the time delay and frequency shift estimated based on the first signal may be low. RSRP ≥ the first threshold indicates that the signal strength of the first signal is high, and the accuracy of the time delay and frequency shift estimated based on the first signal is high. δ2 < the second threshold indicates that the first moment is close to the GNSS failure time of the terminal device, and the number of GNSS locations among the multiple historical location information used for time delay and frequency shift prediction is large, or all historical location information consists of GNSS locations. The accuracy of GNSS locations can be higher than the accuracy of predicted location information. When δ2 < the second threshold, the accuracy of time delay and frequency shift predicted based on multiple historical location information is high. When δ2 ≥ the second threshold, it indicates that the first moment is relatively long after the GNSS failure time of the terminal device, and there may be many predicted location information among the multiple historical location information used for delay and frequency shift prediction. The accumulation of errors in the predicted location information may result in lower accuracy of the delay and frequency shift predicted based on multiple historical location information. GNSS location can be understood as location information determined based on GNSS signals. Therefore, when RSRP < the first threshold and δ2 < the second threshold, the predicted delay and frequency shift are closer to the actual transmission delay and frequency shift between the terminal device and the satellite than the estimated delay and frequency shift. The predicted delay (e.g., τ2) is determined as the first delay (e.g., τ...). Td1 ), determine the predicted frequency shift (e.g., f) D2 ) is the first frequency shift (e.g., f) DTd1 When RSRP ≥ the first threshold and / or δ2 ≥ the second threshold, the estimated delay and frequency shift are closer to the actual transmission delay and frequency shift between the terminal device and the satellite than the predicted delay and frequency shift. The estimated delay (e.g., τ1) is determined as the first delay τ. Td1 And determine the estimated frequency shift (e.g., f). D1 ) is the first frequency shift f DTd1 This improves the accuracy of the first time delay and first frequency shift between the terminal device and the LEO satellite at the first moment, thereby enhancing the effectiveness of uplink time-frequency pre-compensation based on the first time delay and first frequency shift, and ultimately increasing the success rate of access attempts.

[0035] In one possible implementation, the first moment is the moment when the first signal is received, or the first moment is the moment when the first signal is received, or the first moment is later than the moment when the first signal is received.

[0036] In one possible implementation, the first signal includes an SSB signal. Determining a third time delay and a fourth frequency shift based on the first signal includes: determining the transmission and reception times of the SSB signal based on the SSB signal, where the third time delay is the difference between the reception and transmission times; and determining the fourth frequency shift based on the received primary synchronization signal (PSS) and the transmitted PSS determined by the SSB signal.

[0037] In this way, based on the SSB signal, the transmission delay and frequency shift between the terminal device and the satellite can be estimated, such as the third delay and the fourth frequency shift.

[0038] In one possible implementation, the transmission time of the SSB signal is determined as follows:

[0039] The SSB signal is demodulated to obtain the system frame number, half-frame index, and half-frame offset carried in the main information block. System information block type 1 (SIB1) is received on the time-frequency resources indicated by the main information block, and system information block type 1 is obtained. System information block type 19 (SIB19) is received on the time-frequency resources indicated by system information block type 1, and the timing reference carried in system information block type 19 is obtained. The transmission time is determined based on the timing reference, system frame number, half-frame index, and half-frame offset. The transmission time is positively correlated with the timing reference, system frame number, half-frame index, and half-frame offset.

[0040] This allows for the determination of the SSB signal transmission time based on the SSB signal, SIB1, and SIB19. This enables the estimation of the transmission delay between the terminal device and the satellite, such as the third delay, based on the SSB signal transmission time.

[0041] In one possible implementation, the launch time Satisfying the formula:

[0042]

[0043] in, This represents the start time of the radio frame corresponding to the system frame number. , The duration of the wireless frame. This is the system frame number.

[0044] In this way, the transmission time of the SSB signal can be determined based on the SSB signal, SIB1, and SIB19.

[0045] In one possible implementation, the transmission time of the SSB signal is determined as follows: The SSB signal is demodulated to obtain the system frame number, half-frame index, and half-frame offset carried in the main information block. System information block type 1 is received on the time-frequency resources of system information block type 1 indicated by the main information block, thus obtaining system information block type 1. System information block type 9 is received on the time-frequency resources of system information block type 9 (SIB9) indicated by system information block type 1, thus obtaining the Coordinated Universal Time (UTC) carried in system information block type 9. The system frame number (SFN) of the first radio frame after the end of the system information block type 9 transmission window. next .based on SFN next The system frame number, half-frame index, and half-frame offset determine the transmission time, and the transmission time is related to... The system frame number, half-frame index, and half-frame offset are all positively correlated.

[0046] In this way, the transmission time of the SSB signal can be determined based on the SSB signal, SIB1, and SIB9.

[0047] In one possible implementation, the launch time Satisfying the formula:

[0048]

[0049] in, This represents the start time of the radio frame corresponding to the system frame number. , The duration of the wireless frame. This is the system frame number.

[0050] In this way, the transmission time of the SSB signal can be determined based on the SSB signal, SIB1, and SIB9.

[0051] In one possible implementation, the reception time of the SSB signal is determined as follows: A sliding window cross-correlation operation is performed between the received PSS extracted from the SSB signal and a pre-stored local PSS sequence to obtain the cross-correlation peak h0. The reception time is then determined based on the cross-correlation peak h0 and the sampling period of the baseband signal. Determine the time delay offset Time delay offset With cross-correlation peak h0 and sampling period Positive correlation. Determine the reception time, reception time t. rx The start time t of the sliding window start With time delay offset sum.

[0052] This allows for the determination of the SSB signal reception time based on the SSB signal reception time. This, in turn, enables the estimation of the transmission delay between the terminal device and the satellite.

[0053] In one possible implementation, the fourth frequency shift is determined based on the received PSS and the transmitted PSS by the following method: [The received PSS signal is then...] With the transmitted PSS signal Conjugate multiplication yields .Will The correlation calculation is performed in two parts to obtain the correlation value R. PSS From the correlation value R PSS Extracting the fractional octave frequency offset Using fractional frequency offset For the received PSS signal Perform fractional frequency offset compensation to obtain the compensation result. The compensation results Transform to the frequency domain to obtain and will transmit PSS signals Transform to the frequency domain to obtain Detection and The maximum value of the relevant peak is used to determine the frequency offset corresponding to the maximum value of the relevant peak as the integer part of the frequency offset. Based on fractional frequency offset Integer part frequency offset The fourth frequency shift is determined based on the preset subcarrier spacing. The fourth frequency shift is positively correlated with the subcarrier spacing and with a fractional multiple of the frequency offset. Frequency offset of integer part Positive correlation.

[0054] In this way, the reception time of the SSB signal can be determined based on the SSB signal.

[0055] In one possible implementation, the fourth frequency shift Satisfying the formula:

[0056]

[0057] in, The subcarrier spacing.

[0058] In this way, the transmission frequency shift between the terminal device and the satellite, such as the fourth frequency shift, can be estimated based on the SSB signal.

[0059] In one possible implementation, the first signal includes satellite ephemeris information. Based on multiple historical position information, determining the fourth time delay and fifth frequency shift corresponding to the first moment includes: preprocessing the multiple historical position information to obtain preprocessed historical position information; inputting the preprocessed historical position information into a pre-trained first model, which outputs the position data for the first moment; and determining the fourth time delay and fifth frequency shift based on the position data and ephemeris information for the first moment.

[0060] In this way, based on multiple historical location information of the terminal device, the transmission delay and frequency shift between the terminal device and the satellite can be predicted, such as the fourth delay and the fifth frequency shift.

[0061] In one possible implementation, the method further includes terminating the access attempt when the most recent access attempt fails and the number of access attempts reaches a third threshold.

[0062] This reduces the probability of shortening the battery life of terminal devices due to excessive invalid access attempts, thus improving the user experience. Invalid access attempts can be understood as failed access attempts.

[0063] In one possible implementation, the method further includes: receiving a second signal transmitted by the satellite. The second signal can be used for communication. A first access attempt is then initiated again. The re-initiated first access attempt uses a fifth delay and a sixth frequency shift for uplink time-frequency pre-compensation. The fifth delay and sixth frequency shift are determined based on the second signal and / or multiple historical location information of the terminal device, and the fifth delay and sixth frequency shift represent the transmission delay and frequency shift between the terminal device and the satellite at the second time point.

[0064] This allows the terminal device to re-determine the fifth time delay and sixth frequency shift at the second moment, based on the re-received satellite signal (such as the second signal) and / or multiple historical location information of the terminal device, even after the terminal device terminates its access attempt and its environment changes. This enables the terminal device to attempt access again using the newly determined time delay and frequency shift (such as the fifth and sixth time delays). When the environment of the terminal device has minimal impact on the LEO satellite signal, using the newly determined time delay and frequency shift for access attempts can improve the success rate of the terminal device accessing the NTN where the satellite is located.

[0065] In one possible implementation, the method further includes: if the first access attempt fails again, then initiate a second access attempt.

[0066] In this way, if the first access attempt fails, the terminal device can initiate a second access attempt based on the time delay and frequency shift of the reference point selected in the reference point selection order at the second moment, which can also improve the success rate of the terminal device accessing the NTN where the satellite is located.

[0067] Secondly, embodiments of this application provide an access method, the method comprising: sending a first signal to cause a terminal device to initiate an access attempt, wherein the time delay and frequency shift of the uplink used for the access attempt are determined based on the first signal and / or multiple historical location information of the terminal device.

[0068] This allows for the determination of latency and frequency shift for access attempts based on a first signal and / or multiple historical location information of the terminal device, even when GNSS service fails and the terminal device's location information cannot be determined based on GNSS signals. This enables the terminal device to use the first latency and frequency shift for uplink time-frequency pre-compensation and initiate access attempts. It reduces the probability of ineffective uplink latency and frequency pre-compensation due to the inability to determine transmission latency and frequency shift between the terminal device and the satellite caused by GNSS service failure. Determining latency and frequency shift based on satellite signals (such as the first signal) and / or multiple historical location information of the terminal device improves the accuracy of the determined latency and frequency shift. This, in turn, increases the success rate of access attempts by the terminal device based on the determined latency and frequency shift, and improves the success rate of the terminal device accessing the NTN where the satellite is located. The first signal for communication can indicate that the satellite is a communication satellite, such as a satellite in an NTN. The access method of this embodiment can be applied to satellites (such as satellites in an NTN). This embodiment can be applied to satellites, such as communication satellites or satellites in an NTN.

[0069] In one possible implementation, the first signal includes reference point information for multiple common location reference points within the satellite's beam range. The reference point information is used to determine the reference point selection order, and the time-frequency pre-compensation delay and frequency shift for the uplink access attempt are the delay and frequency shift of the common location reference points selected from the multiple common location reference points according to the reference point selection order. The reference point selection order indicates the order in which the distances between the common location reference points and the terminal equipment increase from smallest to largest.

[0070] This allows for a second access attempt using the delay and frequency shift of a reference point, even if the access attempt based on the delay and frequency shift determined by the first signal and / or multiple historical location information of the terminal device fails. The reference point selection order indicates the order in which the common location reference points are located from the terminal device to the nearest reference point, allowing the terminal device to prioritize the reference point closest to it for access attempts. This reduces the probability of residual delay exceeding the PRACH detection window, thereby improving the success rate of access attempts. It also reduces the number of access attempts, enabling the terminal device to quickly access the satellite.

[0071] Thirdly, embodiments of this application provide a communication system comprising a satellite and a terminal device. The terminal device is used to execute the method described in the first aspect or any possible implementation thereof, and the satellite is used to execute the method described in the second aspect or any possible implementation thereof.

[0072] Fourthly, embodiments of this application provide a non-terrestrial network communication module, which is used to perform the methods described in the first aspect or any possible implementation of the first aspect.

[0073] Fifthly, embodiments of this application provide an access device, which may be an electronic device, or a chip or chip system within an electronic device. The access device may include a display unit and a processing unit. When the access device is an electronic device, the display unit may be a display screen. The display unit is used to perform display steps to enable the electronic device to implement an access method described in the first aspect or any possible implementation of the first aspect. When the access device is an electronic device, the processing unit may be a processor. The access device may further include a storage unit, which may be a memory. The storage unit is used to store instructions, and the processing unit executes the instructions stored in the storage unit to enable the electronic device to implement an access method described in the first aspect or any possible implementation of the first aspect. When the access device is a chip or chip system within an electronic device, the processing unit may be a processor. The processing unit executes the instructions stored in the storage unit to enable the electronic device to implement an access method described in the first aspect or any possible implementation of the first aspect. The storage unit may be a storage unit within the chip (e.g., a register, cache, etc.), or a storage unit located outside the chip within the electronic device (e.g., a read-only memory, random access memory, etc.).

[0074] In a sixth aspect, embodiments of this application provide a terminal device, including a processor and a memory, wherein the memory is used to store computer execution instructions, and the processor is used to run the computer execution instructions stored in the memory to perform the method described in the first aspect or any possible implementation of the first aspect.

[0075] In a seventh aspect, embodiments of this application provide a satellite, including a processor and a memory, wherein the memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions stored in the memory to perform the methods described in the second aspect or any possible implementation thereof.

[0076] Eighthly, embodiments of this application provide a computer-readable storage medium storing a computer program or instructions that, when executed on a computer, cause the computer to perform the methods described in the first aspect, any possible implementation of the first aspect, the second aspect, or any possible implementation of the second aspect.

[0077] Ninthly, embodiments of this application provide a computer program product including a computer program, which, when run, causes the computer to perform the methods described in the first aspect, any possible implementation of the first aspect, the second aspect, or any possible implementation of the second aspect.

[0078] Tenthly, this application provides a chip or chip system including at least one processor and a communication interface. The communication interface and the at least one processor are interconnected via a circuit. The at least one processor is used to run computer programs or instructions to perform the methods described in the first aspect, any possible implementation of the first aspect, the second aspect, or any possible implementation of the second aspect. The communication interface in the chip can be an input / output interface, pins, or circuits, etc.

[0079] In one possible implementation, the chip or chip system described above in this application further includes at least one memory storing instructions. The memory can be an internal storage unit of the chip, such as a register or cache, or it can be a storage unit of the chip itself (e.g., read-only memory, random access memory, etc.).

[0080] It should be understood that the second to tenth aspects of this application correspond to the technical solutions of the first or second aspects of this application, and the beneficial effects achieved by each aspect and the corresponding feasible implementation are similar, and will not be repeated here. Attached Figure Description

[0081] Figure 1 A flowchart illustrating the access method provided in an embodiment of this application;

[0082] Figure 2 A schematic diagram illustrating how to determine the start time of a radio frame containing an SSB signal, as provided in an embodiment of this application.

[0083] Figure 3 A schematic diagram of a historical location storage queue provided in an embodiment of this application;

[0084] Figure 4 A schematic diagram illustrating a process for selecting delay and frequency shift, provided for an embodiment of this application;

[0085] Figure 5 This application provides a schematic diagram of reference point deployment for an embodiment.

[0086] Figure 6 Another flowchart illustrating the access method provided in this application embodiment;

[0087] Figure 7 This is another flowchart illustrating the access method provided in an embodiment of this application;

[0088] Figure 8 This is another flowchart illustrating the access method provided in the embodiments of this application. Detailed Implementation

[0089] To facilitate a clear description of the technical solutions in the embodiments of this application, the technologies and some terms involved in the embodiments of this application will be briefly introduced below.

[0090] In the embodiments of this application, terms such as "first" and "second" are used to distinguish identical or similar items with substantially the same function and purpose. For example, "first chip" and "second chip" are used only to distinguish different chips and do not limit their order of execution. Those skilled in the art will understand that terms such as "first" and "second" do not limit the quantity or execution order, and that "first" and "second" do not necessarily imply that they are different.

[0091] It should be noted that, in the embodiments of this application, the terms "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design scheme described as "exemplary" or "for example" in this application should not be construed as being more preferred or advantageous than other embodiments or design schemes. Specifically, the use of terms such as "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0092] In this application embodiment, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c can represent: a, b, c, ab, a--c, bc, or abc, where a, b, and c can be single or multiple.

[0093] The technical solutions of this application can be applied to various communication systems, such as: Long Term Evolution (LTE) systems, LTE Frequency Division Duplex (FDD) systems, LTE Time Division Duplex (TDD) systems, Universal Mobile Telecommunication System (UMTS), Worldwide Interoperability for Microwave Access (WiMAX) communication systems, 5th Generation (5G) systems, New Radio (NR) systems, 6th Generation Mobile Communication Technology (6G) systems, or future evolution communication systems, etc.

[0094] The communication system may include a radio access network (RAN) and a core network (CN). The RAN may include RAN nodes and / or terminal equipment. Terminal equipment can connect to RAN nodes wirelessly. RAN nodes can connect to the core network wirelessly or via wired connections.

[0095] The RAN node involved in the embodiments of this application can be a device that communicates with terminal equipment. The RAN node can also be referred to as a RAN entity, access node, access network device, or radio access network device, etc. The RAN node can be a base station, a transmission reception point (TRP), an evolved NodeB (eNB or eNodeB) in an LTE system, a home base station (e.g., home evolved NodeB, or home Node B, HNB), a base band unit (BBU), a radio controller in a cloud radio access network (CRAN) scenario, or a relay station, access point, vehicle-mounted device, wearable device, or network device in a 5G network or a future evolved PLMN network, etc. It can also be an access point (AP) in a WLAN, or a next-generation NodeB (gNB) in a new radio (NR) system, etc. The aforementioned RAN node can also be a city base station, micro base station, pico base station, femtobase station, etc., and this application does not limit this.

[0096] In scenarios where RAN nodes are deployed off-ground, the RAN nodes can be non-terrestrial devices within an off-ground network (NTN). Off-ground communication based on NTN offers advantages such as wide coverage, long communication distance, high reliability, high flexibility, and high throughput, and it can make communication unaffected by geographical environment, climate conditions, and natural disasters. For example, NTN can provide more stable and higher-quality communication services to users on trains, airplanes, and other modes of transportation.

[0097] Non-terrestrial equipment in NTN can include satellites, drones, or high-altitude platforms. Taking satellites as an example, their orbits can be categorized based on altitude:

[0098] (1) Low Earth orbit (LEO): The orbital altitude can be from 500 km to 2000 km. Satellites operating in LEO can be called LEO satellites. LEO satellites are close to the ground, have extremely low signal transmission delay (about a few milliseconds), small signal attenuation, low requirements for transmission power, and high resolution.

[0099] (2) Medium Earth orbit (MEO): The orbital altitude can range from 2,000 km to 35,786 km, which is lower than the geostationary orbit altitude. Satellites operating in MEO can be called MEO satellites. MEO satellites have a relatively balanced coverage, signal power, and launch cost.

[0100] (3) Geostationary Earth Orbit (GEO): The orbital altitude can be 35,786 kilometers. Satellites operating in GEO can be called GEO satellites. The orbital plane coincides with the equatorial plane, and the inclination is 0 degrees. The direction of motion is the same as the direction of Earth's rotation, and the orbital period is equal to the Earth's rotation period.

[0101] Inclined geosynchronous orbit (IGSO): The orbital altitude is the same as GEO, which can also be 35,786 kilometers. Satellites operating in IGSO can be called IGSO satellites. The orbital period is the same as the Earth's rotation period, but the orbital plane has a large angle with the equatorial plane, with an inclination greater than 0 degrees. For example, the inclination can be 55°-65°.

[0102] The terminal devices in this application embodiment may include handheld devices, vehicle-mounted devices, etc., with wireless connectivity. For example, some terminal devices can be: mobile phones, tablets, PDAs, laptops, mobile internet devices (MIDs), virtual reality (VR) devices, augmented reality (AR) devices, wireless terminals in industrial control, wireless terminals in self-driving, wireless terminals in remote medical surgery, wireless terminals in smart grids, wireless terminals in transportation safety, wireless terminals in smart cities, wireless terminals in smart homes, cellular phones, cordless phones, session initiation protocol (SIP) phones, wireless local loop (WLL) stations, personal digital assistants (PDAs), handheld devices with wireless communication capabilities, computing devices or other processing devices connected to a wireless modem, in-vehicle devices, terminal devices in 5G networks, or future evolution of public land mobile communication networks (PLTs). Terminal devices in a mobile network (PLMN), etc., are not limited to this in the embodiments of this application.

[0103] By way of example and not limitation, in this embodiment, the terminal device can also be a wearable device. Wearable devices, also known as wearable smart devices, are a general term for devices that utilize wearable technology to intelligently design and develop everyday wearables, such as glasses, gloves, watches, clothing, and shoes. Wearable devices are portable devices that are worn directly on the body or integrated into the user's clothing or accessories. Wearable devices are not merely hardware devices, but also achieve powerful functions through software support, data interaction, and cloud interaction. Broadly speaking, wearable smart devices include those that are feature-rich, large in size, and can achieve complete or partial functions without relying on a smartphone, such as smartwatches or smart glasses, as well as those that focus on a specific type of application function and require the use of other devices such as smartphones, such as various smart bracelets and smart jewelry for vital sign monitoring.

[0104] Furthermore, in this embodiment, the terminal device can also be a terminal device in an Internet of Things (IoT) system. IoT is an important component of the future development of information technology. Its main technical feature is to connect objects to the network through communication technology, thereby realizing an intelligent network of human-machine interconnection and object-to-object interconnection.

[0105] The terminal equipment in this application embodiment can also be referred to as: user equipment (UE), mobile station (MS), mobile terminal (MT), access terminal, user unit, user station, mobile station, mobile station, remote station, remote terminal, mobile device, user terminal, terminal, wireless communication equipment, user agent, or user device, etc.

[0106] The following is a brief introduction to some of the terminology used in the embodiments of this application:

[0107] 1. Access attempt

[0108] An access attempt can be understood as a complete request process initiated by a terminal device to try to establish a connection with the network for service transmission.

[0109] For example, the access attempt process may include random access triggering, signaling interaction phase, and result determination.

[0110] Random access can be triggered, for example, when a terminal device is in an idle state, it can trigger a random access procedure if it needs to initiate a call, send data, or respond to a paging.

[0111] Taking a satellite communication scenario where the satellite is not a geographical device as an example, the signaling interaction stage may include steps (1)-(4).

[0112] Step (1): The terminal device sends a random access preamble to the satellite to request access resources; the random access preamble can be a physical random access channel (PRACH) preamble. The PRACH preamble sent by the terminal device to the satellite can be called a PRACH signal.

[0113] Step (2): The satellite can send a random access response (RAR) to the terminal device to allocate uplink resources to the terminal device.

[0114] Step (3): The terminal device can send a radio resource control (RRC) connection request to the satellite. The RRC connection request can carry the access reason, such as an emergency call or normal data transmission.

[0115] Step (4): The satellite can work with the core network to complete authentication and encryption, and send a message to the terminal equipment indicating that the RRC connection has been established.

[0116] The result of an access attempt can be either successful or unsuccessful. Successful access indicates that the terminal device has completed the RRC connection establishment and can enter the service transmission phase. Unsuccessful access indicates that due to reasons such as weak signal, insufficient resources, and / or authentication failure, the terminal device failed to establish a connection, and the terminal device can trigger a retry. An access attempt resulting in a successful connection can be termed a successful access attempt. An access attempt resulting in an unsuccessful connection can be termed an unsuccessful access attempt.

[0117] 2. Time delay and frequency offset (FO)

[0118] Time delay can be understood as the time it takes for a signal to travel from the transmitting end to the receiving end. For downlink signals, the transmitting end can be a satellite, and the receiving end can be a terminal device. For uplink signals, the transmitting end can be a terminal device, and the receiving end can be a satellite. Time delay can be simply referred to as latency.

[0119] Frequency offset can be understood as the shift between the frequency of the signal received at the receiver and the frequency of the signal transmitted at the transmitter. Frequency offset can be, for example, the Doppler shift. Frequency offset can be simply referred to as frequency shift.

[0120] 3. System Information Block (SIB)

[0121] The SIB transmission window can be understood as the time period allocated by the base station for repeatedly transmitting the SIB content for a given SIN. The SIB transmission window can be, for example, 80 milliseconds (ms).

[0122] To increase the probability of a terminal device receiving an SIB, the base station can allocate a window for each SIB. The base station can be a non-terrestrial device in the NTN as described in this application embodiment.

[0123] System information block type 1 (SIB1) can be a core component of the minimum system information (minimal SI) of 5G new radio (NR), also known as the remaining minimum system information (RMSI). It follows the 3GPP TS 38.331 protocol, carries the necessary parameters for initial access of terminal equipment and schedules other system information (OSI).

[0124] SIB1 can be used to transmit core configurations for PRACH occasions, as well as scheduling information for other SIBs, such as SIB9 and SIB19. This scheduling information includes indications or parameters for time and frequency resources. Scheduling information can also be called scheduling parameters. In satellite communications, SIB1 also carries NTN-specific parameters such as the downlink-to-uplink frame offset (k-offset).

[0125] System information block type 9 (SIB9) is another system information (OSI) defined from 3GPP Release 15 onwards. SIB9 can be used to broadcast coordinated universal time (UTC), global positioning system (GPS) time information, and local time synchronization information to support terminal device clock calibration, positioning assistance, and upper-layer time synchronization. SIB9 is not the minimum system information; it requires SIB1 scheduling.

[0126] System Information Block Type 19 (SIB19) is a proprietary Other System Information (OSI) introduced in 3GPP Release 17 for non-terrestrial networks (NTNs, including satellite communications). SIB19 can be used to transmit satellite-assisted, timing synchronization, and cell service parameters required for NTN access, serving as a key configuration carrier for terminal equipment accessing the NTN. SIB19 can be broadcast or dedicated, and requires SIB1 scheduling. For example, SIB19 can be used to transmit satellite ephemeris, uplink timing advance (TA), k-offset compensation, and / or cell mobility management.

[0127] 4. Time-frequency pre-compensation

[0128] Time-frequency precompensation can be understood as the active adjustment of the uplink signal transmission time and carrier frequency by the terminal equipment in non-terrestrial networks, such as satellite communications, in order to offset the long propagation delay and Doppler frequency shift caused by the high telemetry characteristics of satellites before transmitting the uplink signal.

[0129] Time-frequency pre-compensation can include time pre-compensation and frequency pre-compensation. Time-frequency pre-compensation is used to compensate for the propagation delay of the uplink signal from the terminal device to the satellite, ensuring that the uplink signal arrives at the expected reception time at the satellite end. Frequency pre-compensation is used to compensate for the Doppler frequency shift caused by the relative motion between the terminal device and the satellite, ensuring that the frequency of the uplink signal received at the satellite end falls within the operating bandwidth of the satellite receiver.

[0130] Time-frequency precompensation, also known as time delay and frequency offset precompensation, or time delay and frequency shift precompensation.

[0131] Some terminal devices may have GNSS functionality and NTN communication capabilities. NTN communication capabilities include, for example, satellite communication. The terminal device can receive GNSS signals transmitted by GNSS satellites and determine its location information based on the received GNSS signals. Location information may include, for example, position, velocity, and time (PVT) information.

[0132] Taking LEO satellites as non-terrestrial devices in an NTN network and PVT information as location information as an example, terminal devices can receive ephemeris information transmitted by LEO satellites. Based on the PVT information and the ephemeris information of LEO satellites, terminal devices can determine the transmission delay and Doppler shift between the terminal device and the LEO satellites.

[0133] Terminal equipment can adjust the timing and frequency of uplink signal transmission to LEO satellites based on transmission delay and Doppler shift, achieving uplink time-frequency pre-compensation. Time-frequency pre-compensation refers to the pre-compensation of both transmission delay and frequency offset.

[0134] Uplink time-frequency pre-compensation aligns the uplink signal received by LEO satellites with the desired window of the NTN network in both time and frequency, thereby improving the demodulation performance of the uplink signal. This enhances the reliability and stability of the link between the terminal device and the LEO satellite. For example, it can increase the success rate of the terminal device accessing the NTN network.

[0135] In this context, GNSS satellites can be understood as satellites within a GNSS system. GNSS satellites can also be called navigation satellites. To achieve a wider coverage area, GNSS satellites can be MEO satellites, GEO satellites, or IGSO satellites. GNSS signals are the satellite signals transmitted by GNSS satellites. Satellites in an NTN network can be called communication satellites or service satellites.

[0136] Compared to LEO satellite signals, GNSS signals are weaker. GNSS signals are more susceptible to environmental factors or interference from the terminal device. For example, when the terminal device is indoors, in a canyon, or in an environment with interference, it may be unable to receive GNSS signals.

[0137] When the GNSS signal received by the terminal device is below threshold A due to environmental influences or interference, or when the terminal device cannot receive GNSS signals at all, the terminal device cannot determine its PVT information, meaning the GNSS service of the terminal device is unavailable. A GNSS signal below threshold A indicates that the GNSS signal cannot be used to determine the PVT information of the terminal device.

[0138] GNSS service failure can be termed GNSS failure. In the event of GNSS failure, terminal devices cannot rely on GNSS for time-frequency precompensation.

[0139] For example, if the GNSS service of a terminal device fails, the terminal device cannot obtain its PVT information. Based solely on the ephemeris information of LEO satellites, the terminal device cannot determine the transmission delay and frequency shift between itself and the LEO satellites. This may result in the terminal device being unable to effectively pre-compensate for uplink delay and frequency, leading to a low success rate in accessing LEO satellites, or even failing to complete the initial access.

[0140] In view of this, embodiments of this application provide an access method applied to a terminal device. When the terminal device's GNSS service fails, the terminal device can receive a first signal from a LEO satellite. The terminal device can determine a first time delay and a first frequency shift based on the first signal and / or multiple historical location information of the terminal device. This reduces the probability of being unable to determine the transmission time delay and frequency shift between the terminal device and the LEO satellite when the terminal device's GNSS service fails. The terminal device can use the first time delay and the first frequency shift to perform uplink time-frequency pre-compensation and initiate a first access attempt. This reduces the probability of being unable to effectively pre-compensate the uplink time delay and frequency due to the inability to determine the transmission time delay and frequency shift between the terminal device and the LEO satellite. This further improves the success rate of the first access attempt. Determining the time delay and frequency shift based on the LEO satellite signal (such as the first signal) and / or multiple historical location information of the terminal device improves the accuracy of the determined time delay and frequency shift (such as the first time delay and the first frequency shift), thereby increasing the success rate of the terminal device accessing the LEO satellite.

[0141] The following description uses the terminal equipment as user equipment (UE) and the non-terrestrial equipment in NTN as LEO satellites as an example, and illustrates the solution provided in this application with reference to some embodiments. LEO satellites can be called service satellites or communication satellites.

[0142] Figure 1 This is a schematic flowchart of an access method provided in an embodiment of this application.

[0143] like Figure 1 As shown, the access method provided in this application embodiment may include:

[0144] S101, The satellite can send a first signal to the UE. Correspondingly, the UE can receive the first signal from the satellite. The first signal is used for communication.

[0145] For example, the satellite may periodically broadcast a first signal. Correspondingly, the UE may receive the first signal from the satellite. The first signal may be used for communication.

[0146] For example, LEO satellites operate at a lower altitude than GNSS satellites. Compared to the strength and interference resistance of GNSS signals, the first signal transmitted by LEO satellites to the UE is stronger and more resistant to interference. In the event of GNSS failure at the UE, the UE can receive the first signal transmitted by the LEO satellite.

[0147] S102, the UE may initiate a first access attempt. The first access attempt uses a first delay and a first frequency shift to perform uplink time-frequency pre-compensation. The first delay and the first frequency shift are determined based on a first signal and / or multiple historical location information of the terminal device.

[0148] The first time delay and the first frequency shift can refer to the transmission delay and frequency shift between the UE and the LEO satellite at the first moment. For example, the first time delay can be understood as the transmission delay between the UE and the LEO satellite at the corresponding first moment. The first frequency shift can be understood as the frequency shift between the UE and the LEO satellite at the corresponding first moment. The first moment can be the moment when the first signal is received. The first moment can also be later than the moment when the first signal is received. For example, the first moment T... d1 It can be equal to the moment the first signal is received plus a preset duration A. Duration A can be the duration that the UE determines for the delay and frequency shift used for the access attempt.

[0149] For example, the first time delay and the first frequency shift can be estimated by the UE based on the first signal.

[0150] In this way, even if the UE's GNSS fails, the UE can estimate the transmission delay and frequency shift between the UE and the LEO satellite at the first moment based on the LEO satellite signal (such as the first signal). This allows for uplink time-frequency pre-compensation using the estimated delay and frequency shift, and subsequent access attempts, thus improving the access success rate. The first signal is transmitted by the satellite and received by the UE. Estimating the delay and frequency shift based on the first signal improves the accuracy of the obtained delay and frequency shift. This, in turn, enhances the effectiveness of uplink time-frequency pre-compensation using the estimated delay and frequency shift, thereby increasing the UE's success rate in accessing the LEO satellite.

[0151] Among these, the GNSS of the UE is ineffective, for example, the GNSS signal received by the UE cannot be used to determine the location of the UE, or the UE cannot receive the GNSS signal.

[0152] Optionally, the first time delay and the first frequency shift can be predicted by the UE based on multiple historical location information of the UE. The historical location information can be location information determined by the UE based on GNSS signals. Location information determined based on GNSS signals can be referred to as GNSS location.

[0153] For example, the UE can use a first model to predict its location information, based on multiple historical location data of the UE, to predict the UE's location information at a first moment. Based on the predicted location information at the first moment and the ephemeris information of the LEO satellite, the UE can determine its first time delay and first frequency shift at the first moment, thus obtaining the time delay and frequency shift predicted based on historical location information.

[0154] The ephemeris information may include the correspondence between the position information and time of LEO satellites. The ephemeris information of LEO satellites may be pre-stored by the UE or obtained by the UE from the first signal. For example, the first signal may include a system information block (SIB), such as System Information Block Type 19 (SIB19). SIB19 may carry the ephemeris information of LEO satellites.

[0155] In this way, even if the UE's GNSS fails, the UE can predict its position at the first moment based on multiple historical location data. Then, based on the predicted position and the ephemeris information of the LEO satellites, the transmission delay and frequency shift between the UE and the LEO satellites at the first moment can be determined. This allows for uplink time-frequency pre-compensation using the predicted delay and frequency shift, and subsequent access attempts, improving the access success rate. Multiple historical location data can characterize the UE's movement trend; using multiple historical location data to predict the UE's position at the first moment improves the accuracy of the predicted position. This, in turn, improves the accuracy of the predicted delay and frequency shift. Consequently, it enhances the effectiveness of uplink time-frequency pre-compensation using the predicted delay and frequency shift, thereby increasing the UE's success rate in accessing LEO satellites.

[0156] Optionally, the first time delay and the first frequency shift can be a set of time delays and frequency shifts selected by the UE from the estimated time delay and frequency shift and the predicted time delay and frequency shift based on the first signal and multiple historical location information of the UE.

[0157] For example, the UE can estimate the time delay and frequency shift at a first moment based on the first signal. The UE can also predict the time delay and frequency shift at a first moment based on multiple historical location information of the UE.

[0158] The UE can determine whether to attempt access using the estimated time delay and frequency shift, or the predicted time delay and frequency shift, based on the signal strength of the first signal and the second time interval from the moment when the UE's location information was last determined based on the GNSS signal to the moment when the first time interval is reached.

[0159] Among them, the time when the UE most recently determined its location information based on GNSS signals is the time when the UE most recently obtained its GNSS location.

[0160] Thus, in the event of GNSS failure, based on the signal strength of the first signal and the second duration from the time the UE last obtained its GNSS position to the first moment, the UE can select the more accurate time delay and frequency shift from the estimated time delay and frequency shift to the predicted time delay and frequency shift. This allows the UE to use the selected time delay and frequency shift for uplink time-frequency pre-compensation and to attempt access, thereby improving the access success rate.

[0161] Given the first delay and the first frequency shift, the UE may initiate a first access attempt. The first access attempt uses the first delay and the first frequency shift for uplink time-frequency pre-compensation.

[0162] For example, taking the uplink signal of the access attempt as including the PRACH signal as an example, the UE can base its decision on the first time delay τ. Td1 The second timing advance (TA) of the PRACH signal is determined as follows: The UE can be based on the first frequency shift f. DTd1 The frequency adjustment amount of the PRACH signal is determined to be -f DTd1 This enables time-frequency pre-compensation for uplink signals such as PRACH signals. Timing advance (TA) can also be called timing advance.

[0163] UE can follow the second TA as Adjust the transmission time of the PRACH signal, and adjust the frequency by -f. DTd1 Adjust the frequency of the PRACH signal. The UE can send the frequency-adjusted PRACH signal to the LEO satellite at the adjusted transmission time to initiate the first access attempt.

[0164] The first time delay and the first frequency shift are determined based on multiple historical location information of the first signal and / or the terminal device.

[0165] For example, the first delay and the first frequency shift can be estimated by the UE based on the first signal, predicted by the UE based on multiple historical location information of the UE, or selected by the UE from the estimated delay and frequency shift and the predicted delay and frequency shift based on the signal strength and second duration of the first signal. The second duration can be understood as the duration from the time when the UE last determined its location information based on the GNSS signal to the first time. The second duration can be called the prediction duration or the GNSS failure duration.

[0166] The access attempt in this embodiment can be used to request access to a LEO satellite, that is, to request access to the NTN network where the LEO satellite resides. The access attempt may be a first access attempt or a second access attempt. For ease of understanding, the second access attempt will be described later and will not be described here.

[0167] In this way, in the event of GNSS failure, the probability of not being able to effectively pre-compensate uplink delay and frequency due to the inability to determine the transmission delay and frequency shift between the terminal device and LEO satellite can be reduced, thereby improving the success rate of UE accessing LEO satellite.

[0168] like Figure 1 As shown in the embodiments of this application, the access method allows the UE to receive satellite signals transmitted by LEO satellites when the UE's GNSS fails. The satellite signals transmitted by the LEO satellites include, for example, a first signal. The UE can determine a first time delay and a first frequency shift based on the first signal and / or multiple historical location information of the UE. This allows the UE to use the first time delay and the first frequency shift to perform uplink time-frequency pre-compensation and initiate an access attempt (such as a first access attempt). This reduces the probability of the UE failing to access the LEO satellite due to its inability to determine the transmission delay and frequency shift between the UE and the LEO satellite, and improves the success rate of the UE accessing the LEO satellite.

[0169] The following section will explain S102 in detail, taking the first time delay and the first frequency shift corresponding to the first time moment as an example.

[0170] In one possible implementation, the UE's first time delay and first frequency shift can be, for example, a third time delay and a fourth frequency shift estimated by the UE based on the first signal. The determination of the third time delay and the fourth frequency shift can be found in Example 1.

[0171] Example 1: The UE can determine the third time delay and the fourth frequency shift based on the first signal.

[0172] For example, the first signal may include a synchronization signal block (SSB) signal. If the first moment is the reception moment of the first signal, then the first moment may be the reception moment of the SSB signal.

[0173] The UE can determine the third time delay and the fourth frequency shift based on the SSB signal, thus obtaining the time delay and frequency shift estimated based on the satellite signal. The first time delay and the third time delay can be the same. The first frequency shift and the fourth frequency shift can be the same.

[0174] For example, the UE can determine the transmission time t of the SSB signal based on the SSB signal. tx and receiving time t rx .

[0175] The UE can be based on the transmission time t tx and receiving time t rx Determine the transmission delay between the UE and the LEO satellite. . This refers to the third time delay. The third time delay can be the difference between the reception time and the transmission time. The formula can be satisfied:

[0176]

[0177] Launch time t tx and receiving time t rx The following is an example of how to determine it.

[0178] Determine the launch time t tx Example:

[0179] In one possible implementation, the transmission time of the SSB signal is determined as follows:

[0180] The UE can demodulate the SSB signal to obtain the system frame number, half-frame index, and half-frame offset carried in the main information block. The UE can receive SIB1 on the time-frequency resources of SIB1 indicated by the main information block to obtain SIB1. The UE can receive SIB19 on the time-frequency resources of SIB19 indicated by SIB1 to obtain the timing reference carried in SIB19. The UE can determine the transmission time based on the timing reference, system frame number, half-frame index, and half-frame offset. The transmission time is positively correlated with the timing reference, system frame number, half-frame index, and half-frame offset.

[0181] In one possible implementation, the transmission time of the SSB signal is determined as follows:

[0182] The UE can demodulate the SSB signal to obtain the system frame number, half-frame index, and half-frame offset carried in the main information block. The UE can receive SIB1 on the time-frequency resources of SIB1 indicated by the main information block to obtain SIB1. The UE can receive SIB9 on the time-frequency resources of SIB9 indicated by SIB1 to obtain the Coordinated Universal Time (UTC) carried in SIB9. The system frame number (SFN) of the first radio frame after the SIB9 transmission window ends. next UE can be based on SFN next The system frame number, half-frame index, and half-frame offset determine the transmission time, and the transmission time is related to... The system frame number, half-frame index, and half-frame offset are all positively correlated.

[0183] For example, in the event of GNSS failure, the UE can receive SSB signals transmitted by LEO satellites. The SSB signals may include the primary synchronization signal (PSS), the secondary synchronization signal (SSS), and the physical broadcast channel (PBCH).

[0184] Satellites and terminal equipment can use orthogonal frequency division multiplexing (OFDM) for signal transmission.

[0185] In an SSB signal, the PSS, SSS, and PBCH can reside on different OFDM symbols in the time domain, but on the same 240 subcarriers in the frequency domain. For example, the SSB occupies four consecutive OFDM symbols in the time domain. Taking four consecutive OFDM symbols (symbol 0, symbol 1, symbol 2, and symbol 3) as an example, the PSS can be located at symbol 0, the PBCH at symbol 1, the SSS at symbol 2, and the PBCH at symbol 3.

[0186] The time-frequency positions of PSS, SSS, and PBCH are defined by the 3rd Generation Partnership Project (3GPP). The time-frequency positions of PSS, SSS, and PBCH are fixed. That is, the PSS, SSS, and PBCH in the SSB signal have fixed time-frequency resource mappings. The UE can obtain symbol synchronization by detecting the PSS; that is, the UE can obtain the symbol containing the PSS by detecting the PSS. Based on the symbol containing the PSS, the UE can extract the SSS and PBCH from the SSB signal according to the symbol offset specified in the 3GPP standard. The specific implementation principle of UE PSS detection can be found in the subsequent section on determining the reception time t. rx The specific implementation principle of PSS detection in the example will not be described here.

[0187] The UE can use the PSS and SSS in the SSB signal for time-frequency synchronization to obtain synchronization information and lock the cell identifier (ID). The PBCH can include PBCH data and demodulation reference signal (DM-RS). The UE can use the synchronization information and the demodulation reference signal in the SSB signal to perform channel estimation and obtain the channel estimation result. The UE can use the channel estimation result to descramble and decode the PBCH to obtain the master information block (MIB) and obtain the system frame number (SFN), half-frame index, and half-frame offset (SSB offset within half-frame) carried in the MIB.

[0188] The MIB carries the system frame number, which is the system frame number (SFN) of the radio frame where the SSB signal resides. SSB Wireless frame duration The interval can be 10 milliseconds (ms). For example, the SFN can be a 10-bit counter, and its value can be any value from 0 to 1023. The SFN increments by 1 every 10 ms, with a period of 10.24 seconds. The half-frame index can be 0 or 1, where 0 indicates the first half-frame and 1 indicates the second half-frame. Taking a radio frame duration of 10 ms as an example, a half-frame index of 0 can indicate that the SSB is located in the first 5 ms of the radio frame, and a half-frame index of 1 can indicate that the SSB is located in the last 5 ms of the radio frame. The half-frame offset can be understood as the offset time of the SSB within a half-frame, and can be used to indicate the specific time-domain position of the SSB within a half-frame, such as indicating which symbol the SSB is within.

[0189] The MIB can also carry indication information A for indicating the time-frequency resources of SIB1. Indication information A can be, for example, pdcch-ConfigSIB1 information. Time-frequency resources refer to time and frequency resources.

[0190] The UE can receive SIB1 on the time-frequency resources indicated by indication information A. For example, the UE can monitor the PDCCH on the time-frequency resources indicated by the pdcch-ConfigSIB1 information and then receive SIB1. SIB1 can carry indication information B for indicating time-frequency resources of SIB9 and / or indication information C for indicating time-frequency resources of SIB19.

[0191] The UE may receive SIB9 on the time-frequency resources indicated by indication information B, and / or the UE may receive SIB19 on the time-frequency resources indicated by indication information C.

[0192] For example, SIB9 may carry the Coordinated Universal Time (UTC) and the System Frame Number (SFN) of the first radio frame after the end of the SIB9 transmission window. next UTC can be referred to as UTC time. The UTC time carried by SIB9 is the start time of the first radio frame (SFN) after the end of the SIB9 transmission window. .

[0193] The UE can base its decisions on the system frame number (SFN) of the radio frame in which the SSB signal is located. SSB UTC time The system frame number (SFN) of the first radio frame after the SIB9 transmission window ends. next Determine the start time of the radio frame containing the SSB signal. The start time of the radio frame containing the SSB signal. The formula can be satisfied:

[0194]

[0195] Here, mod can be either modulo or modulus. It can represent taking The remainder. This is the duration of the wireless frame.

[0196] With wireless frame duration Taking 10 milliseconds (ms) as an example, The formula can be satisfied:

[0197]

[0198] Optionally, the SIB19 may carry a timing reference. Taking the latest radio frame as SFN #0 as an example, the timing reference may include the start time of the latest radio frame. .

[0199] The UE can base its decisions on the timing reference and the system frame number (SFN) of the radio frame in which the SSB signal resides. SSB Determine the start time of the radio frame containing the SSB signal. The start time of the radio frame containing the SSB signal. The formula can be satisfied:

[0200]

[0201] Still based on wireless frame duration Taking 10 milliseconds (ms) as an example, The formula can be satisfied:

[0202]

[0203] Figure 2 This is a schematic diagram illustrating how to determine the start time of a radio frame containing an SSB signal, as provided in an embodiment of this application.

[0204] For example, such as Figure 2 As shown, the radio frame containing the SSB signal is designated SFN #16, and the radio frame duration is... Taking 10 milliseconds (ms) as an example, if the system frame number of radio frame SFN #16 is 16, then the start time of the radio frame containing the SSB signal is... The formula can be satisfied:

[0205]

[0206] like Figure 2 As shown, taking radio frame SFN #32 where the SSB signal is located as an example, the system frame number of radio frame SFN #32 is 32. Therefore, the start time of the radio frame where the SSB signal is located... The formula can be satisfied:

[0207]

[0208] At the start time of the radio frame containing the SSB signal. In this case, the UE can be based on The half-frame index and half-frame offset are used to determine the transmission time t. tx Launch time t tx The formula can be satisfied:

[0209]

[0210] Still based on wireless frame duration Taking 10 milliseconds (ms) as an example, The formula can be satisfied:

[0211]

[0212] Determine the receiving time t rx Example:

[0213] In one possible implementation, the reception time of the SSB signal is determined as follows:

[0214] The UE can perform a sliding window cross-correlation operation on the received PSS extracted from the SSB signal and the pre-stored local PSS sequence to obtain the cross-correlation peak h0. The UE can then use the cross-correlation peak h0 and the sampling period as a basis for further analysis. Determine the time delay offset Delay offset With cross-correlation peak h0 and sampling period Positive correlation. The UE can determine the reception time, reception time t. rx The start time t of the sliding window start With time delay offset sum.

[0215] For example, upon receiving an SSB signal r(n) transmitted by an LEO satellite, the UE can correlate the SSB signal with a pre-stored PSS sequence s(n) and determine the symbol position corresponding to the correlation peak higher than a preset peak value as the symbol position of the PSS, thus achieving symbol synchronization. Here, s(n) can be pre-generated by the UE or pre-stored in the UE. s(n) can be referred to as the local PSS sequence.

[0216] For example, the local PSS sequence may include three PSS sequences that conform to the 3GPP standard. Each of the three standard PSS sequences corresponds to a cell identifier. The UE can traverse these three standard PSS sequences and correlate the traversed PSS sequences with the received SSB signal to determine the symbol position of the PSS, thereby achieving symbol synchronization.

[0217] For example, the UE can traverse the three standard PSS sequences and slide the traversed PSS sequences on the SSB signal received by the UE. At each sliding position, a similarity score is calculated. The duration between two adjacent similarity scores is the sampling period. The UE can determine scores higher than a preset peak value. The time point in question is the starting position of the PSS sequence. Alternatively, the UE can determine multiple positions corresponding to the sliding of the PSS sequence on the SSB signal. Among them, the largest The time point in question is the starting position of the PSS sequence. (Higher than the preset peak value) The sign position corresponding to the given time point is the sign position of the PSS. Alternatively, the largest... The symbol position corresponding to the given time point is the symbol position of the PSS. This achieves symbol synchronization.

[0218] The formula can be satisfied:

[0219]

[0220] Where r(n) can be the SSB signal received by the UE. n can be a time-domain variable or a discrete-time sampling point index in the time domain. N can be the length of the SSB signal in the time domain. N represents the time offset of the slide. N can be an integer.

[0221] The UE can extract the PSS signal from the SSB signal based on the symbol position of the PSS, and this extracted PSS signal is the received PSS signal. In this way, the PSS signal can be detected.

[0222] The extracted PSS signal is represented in the time domain as follows: For example, the UE can call the local PSS sequence. ,right and Perform cross-correlation calculations using a sliding window to search for the cross-correlation peak h0. The UE can then determine the actual arrival time delay offset of the SSB signal based on the cross-correlation peak h0. .

[0223] The cross-correlation peak h0 can satisfy the formula:

[0224]

[0225] Delay offset The formula can be satisfied:

[0226]

[0227] in, It can represent At its maximum, h is h0. h can be the time offset of the slide. This can be the sampling period of the baseband signal. Time delay offset. This can also be understood as the delay offset calculated based on the UE's local clock. The UE's local clock can be the UE's system time.

[0228] UE can be based on delay offset and sliding window start time t start Determine the receiving time t rx . t start For UE and The start time of the sliding window in the cross-correlation operation using a sliding window. Reception time t. rx With time delay offset and sliding window start time t start Positive correlation.

[0229] For example, receiving time t rx The formula can be satisfied:

[0230]

[0231] Upon receiving an SSB signal, the UE can perform Doppler frequency shift estimation based on the SSB signal to obtain the estimated frequency shift f. D1 .

[0232] For example, the UE can determine the fourth frequency shift based on the received PSS and the transmitted PSS determined by the SSB signal. For ease of understanding, the specific implementation principle of the UE determining the transmitted PSS based on the SSB signal will be described later, and will not be described here.

[0233] For example, the UE can base its decisions on the received time-domain SSB signal. Deterministic time-domain received PSS signal and transmit PSS signal UE can and Conjugate multiplication yields UE can The correlation was calculated in two parts, before and after, to obtain the correlation value R. PSS The UE can obtain the relevant value R. PSS Extracting the fractional octave frequency offset The UE can use a fractional frequency offset. For receiving PSS signals Fractional frequency offset compensation is performed to obtain the compensation result. The UE can detect the maximum value of the correlation peak between the compensation result and the pre-stored local PSS sequence, and determine that the frequency offset corresponding to the maximum value of the correlation peak is the integer part of the frequency offset. The UE can be based on a fractional multiple of the frequency offset. Integer part frequency offset The fourth frequency shift is determined based on the preset subcarrier spacing. The fourth frequency shift is positively correlated with the subcarrier spacing and with a fractional multiple of the frequency offset. Frequency offset of integer part Positive correlation.

[0234] For example, the SSB signal received by the UE in the time domain, denoted as r(n), can satisfy the formula:

[0235]

[0236] in, SSB signal transmitted by LEO satellite. It is noise. This is the initial phase. This represents the normalized Doppler frequency shift. n can be the index of the discrete-time sampling point in the time domain.

[0237] Normalized Doppler frequency shift The formula can be satisfied:

[0238]

[0239] in, This represents the frequency offset value to be estimated. The preset subcarrier spacing. The frequency offset is for the fractional part. The frequency offset is the integer part. Optionally, The subcarrier spacing of LEO satellites can be used, and the ephemeris information of LEO satellites can include the subcarrier spacing. The UE can obtain this information from the ephemeris information broadcast by the LEO satellites. The ephemeris information of the LEO satellite can be carried in SIB19 broadcast by the LEO satellite.

[0240] The UE can determine the estimated frequency shift f based on the fractional part of the frequency offset, the integer part of the frequency offset, and the subcarrier spacing. D1 Examples of estimation for the fractional part frequency offset and the integer part frequency offset are as follows.

[0241] Example of estimating the frequency offset of the decimal part:

[0242] by The PSS signal is part of the SSB signal transmitted by the LEO satellite. Taking the PSS signal in the SSB signal received by the UE as an example, the UE can decode the received PSS to obtain the transmitted PSS. For instance, after decoding the SSB signal by matching it against the local PSS sequence to obtain the cell identifier, the UE can obtain the transmitted PSS signal corresponding to the cell identifier. .

[0243] For example, taking a local PSS sequence containing three standard PSS sequences s0(n), s1(n), and s2(n), where s(n) is s0(n), s1(n), or s2(n), each of s0(n), s1(n), and s2(n) corresponds to a cell identifier. One of the PSS sequences s0(n), s1(n), and s2(n) can determine the symbol position of the PSS. When the UE determines the symbol position of the PSS by traversing and correlating the SSB signal with the local PSS sequence, the local PSS sequence corresponding to the symbol position of the PSS is the PSS sequence transmitted by the LEO satellite. The PSS sequence transmitted by the LEO satellite corresponds to the cell identifier, which is the cell identifier that the UE locks onto based on the SSB signal. The local PSS sequence corresponding to the locked cell identifier is the PSS sequence transmitted by the LEO satellite. .

[0244] Taking the local PSS sequence corresponding to the symbol position of PSS as s0(n) as an example, the local PSS sequence s0(n) corresponding to the UE is = .

[0245] UE can and Conjugate multiplication yields .

[0246] The formula can be satisfied:

[0247]

[0248] in, It represents a conjugate complex number. express The conjugate of complex numbers.

[0249] UE can The correlation was calculated in two parts, before and after, to obtain the correlation value R. PSS .

[0250] Correlation value R PSS The formula can be satisfied:

[0251]

[0252] UE can extract fractional frequency offset estimated value . The formula can be satisfied:

[0253]

[0254] in, It can represent The maximum value. The variables can include and The fractional octet frequency offset can be referred to as the fractional part frequency offset.

[0255] Example of estimating the integer part of the frequency offset:

[0256] The UE can receive the PSS signal By performing fractional octave frequency offset compensation, the compensation result can be obtained. . The formula can be satisfied:

[0257]

[0258] UE can Fourier transform to the frequency domain yields And will Fourier transform to the frequency domain yields the local standard frequency domain PSS signal. UE can and Correlation calculations are performed to measure the maximum value of the correlation peak, and the integer part of the frequency offset corresponding to the maximum value of the correlation peak is determined based on the maximum value of the correlation peak. Integer part frequency offset The formula can be satisfied:

[0259]

[0260] in, This can be the frequency offset of the slide. It can represent The value of g at its maximum is k can be the index of a discrete frequency sampling point in the frequency domain, or , which is a variable in the frequency domain. It can be the length of the PSS signal in the frequency domain. It can be an integer.

[0261] UE can be based on the fractional part of the frequency offset Frequency offset of integer part ,as well as Determine Doppler frequency shift Doppler shift The formula can be satisfied:

[0262]

[0263] Doppler shift That is, the estimated frequency shift, also known as the fourth frequency shift.

[0264] In one possible implementation, the UE's first delay and first frequency shift at the first moment can be, for example, a fourth delay and a fifth frequency shift predicted by the UE based on multiple historical location information. When the terminal device is the UE, the terminal device's location information can be referred to as UE location information. The determination of the fourth delay and the fifth frequency shift can be found in Example 2.

[0265] Example 2: The UE can determine the fourth delay and fifth frequency shift corresponding to the first moment based on multiple historical location information.

[0266] For example, the UE may have a pre-configured historical location storage queue. The historical location storage queue may be simply referred to as the storage queue. The length of the storage queue can be L. L can be a positive integer. The storage queue can be used to store L UE location information from the most recent L time points. The duration between two adjacent time points in the L time points is ΔT. ΔT can be preset. L can be, for example, 60, or any other value besides 60; the specific value of L is not limited in this embodiment.

[0267] ΔT can be determined based on the UE's movement speed. For example, if the UE is a mobile phone, its speed can be the user's walking speed, then ΔT could be tens of seconds. If the UE is an in-vehicle device, its speed can be the vehicle's driving speed, then ΔT could be several seconds. ΔT can be called the sampling interval or epoch interval of location information. Taking an in-vehicle device as an example, the sampling interval ΔT for the location information of the in-vehicle device can be 2 seconds, or it can be any other value besides 2 seconds. This application does not limit the specific value of ΔT in its embodiments.

[0268] The storage queue can be a first-in-first-out queue. For example, when the position information at time T0 is stored in the storage queue, the position information at time T0-LΔT in the storage queue is deleted.

[0269] If GNSS is not invalid, the latest location information stored in the storage queue can be the location information of the UE determined based on the GNSS signal.

[0270] In the event of GNSS failure, the latest location information stored in the storage queue can be the UE location information predicted based on multiple historical location information.

[0271] Once the UE determines its location information, it can store the determined UE location information into a storage queue, thereby updating the historical location information in the storage queue.

[0272] Figure 3 This is a schematic diagram of a historical location storage queue provided in an embodiment of this application.

[0273] like Figure 3 The storage queue shown stores P0, P1, ..., P L-1 There are L location information points in total. These L location information points correspond to T0, T1, ..., T L-1 There are L time points in total. For example, P0 corresponds to time T0, and P1 corresponds to time T1. L-1 The corresponding time is T L-1 When the UE stores the location information P0 at time T0 into the storage queue, the UE can store the location information P0 at time T0-LΔT in the storage queue. L delete.

[0274] For example, location information may include a timestamp, location coordinates, velocity, and acceleration. Location information including timestamps, location coordinates, velocity, and acceleration can also be called spatiotemporal location information. Historical location information P is stored in the storage queue. l It can be represented as:

[0275] P l = (T l X l Yl Z l V xl V yl V zl A xl A yl A zl )

[0276] Here, l can represent the sequence number of the position information in the storage queue corresponding to the time. l can be any natural number from 0 to L-1. For example, l = 0, 1, 2, ..., L-1. l This is the timestamp of the l-th moment.

[0277] X l Let X be the X-axis coordinate of the UE at time l. l Let Z be the Y-axis coordinate of the UE at time l. l Let X be the Z-axis coordinate of the UE at time l. l Y l Z l () can represent the position coordinates of the UE at the l-th time.

[0278] V xl Let V be the velocity of the UE in the X-axis direction at time l. yl Let V be the velocity of UE in the Y-axis direction at time l. zl Let V be the velocity of the UE in the Z-axis direction at time l. xl V yl V zl () can represent the velocity of the UE at time l.

[0279] A xl Let A be the acceleration of the UE in the X-axis direction at time l. yl Let A be the acceleration of UE in the Y-axis direction at time l. zl Let be the acceleration of UE in the Z-axis direction at time l. (A) xl A yl A zl () can represent the acceleration of the UE at time l.

[0280] To accelerate convergence, the UE can preprocess the L location information data in the storage queue to obtain preprocessed historical location information. This allows the location feature data P to be processed. l Transformed into position increment ΔP between epochs l Data preprocessing can be simply referred to as preprocessing.

[0281] For example, to ensure the stability and accuracy of model training, and to ensure that different types of features have the same scale, the UE can normalize the data in the storage queue to obtain the position increment ΔP between epochs. l Position increment ΔP between epochs l It can be represented as:

[0282] ΔP l =(ΔT l ΔX l ΔY l ΔZ l V xl V yl V zl A xl A yl A zl )

[0283] Where, ΔT l =T l -T l+1 ΔX l =X l -X l+1 ΔY l =Y l -Y l+1 ΔZ l =Z l -Z l+1 T l+1 This represents the (l+1)th time step in the storage queue. l+1 Let X be the X-axis coordinate of the UE at time l+1. l+1 Let Z be the Y-axis coordinate of the UE at time l+1. l+1 Let X be the Z-axis coordinate of the UE at time l+1. l+1 Y l+1 Z l+1 () can represent the position coordinates of the UE at time l+1.

[0284] Preprocessed historical location information, such as the location increment ΔP between epochs corresponding to the last L-1 times stored in the storage queue. l The UE can store the position increment ΔP between the last L-1 time intervals in the storage queue. l Input a pre-trained first model. The first model can output the first time step T. d1 Predicted position increment ΔP Td1 First moment T d1 Predicted position increment ΔP Td1 This refers to the predicted location data at the first moment. First moment T d1 Predicted position increment ΔP Td1It can be represented as:

[0285] ΔP Td1 =(ΔT Td1 ΔX Td1 ΔY Td1 ΔZ Td1 V xTd1 V yTd1 V zTd1 A xTd1 A yTd1 A zTd1 )

[0286] The UE can determine the fourth time delay and the fifth frequency shift based on the location data at the first moment and the ephemeris information of the LEO satellite.

[0287] For example, the UE can be based on ΔP Td1 Based on the latest stored position information in the storage queue, determine the UE's position coordinates at the first moment. Taking the latest stored position information in the storage queue as P0 as an example, the UE's position coordinates at the first moment... The following formula can be satisfied:

[0288]

[0289] in, Let X be the X-axis coordinate of the UE at the first moment. , This represents the X-axis coordinate of the UE at time 0 in the storage queue. Let Y be the Y-axis coordinate of UE at the first moment. , This represents the Y-axis coordinate of the UE at time 0 in the storage queue. Let Z be the Z-axis coordinate of the UE at the first moment. , This represents the Z-axis coordinate of the UE at time 0 in the storage queue. The position coordinates of the UE at time 1 are the predicted position results of the UE.

[0290] SIB19 can also carry ephemeris information for LEO satellites. This ephemeris information can include the correspondence between the LEO satellite's position information and time. The LEO satellite's position information can include its position coordinates and velocity vector. Based on this correspondence, the UE can determine the LEO satellite's position coordinates p at the first moment. sat and the velocity vector of the LEO satellite at the first moment .

[0291] The UE can be based on the UE's position coordinates at the first moment. and the position coordinates p of the LEO satellite at the first momentsat Determine the fourth delay Furthermore, the UE can be based on the UE's position coordinates at the first moment. The position coordinates p of the LEO satellite at the first moment sat The velocity vector of the LEO satellite at the first moment and preset carrier frequency Determine the fifth frequency shift .

[0292] The fourth delay and the fifth frequency shift are the predicted delay and frequency shift. Fourth delay The formula can be satisfied:

[0293]

[0294] in, for and p sat The Euclidean distance between them. c is the speed of light.

[0295] Fifth frequency shift The formula can be satisfied:

[0296]

[0297] in, , This is the unit direction vector from which the UE points to the satellite.

[0298] As shown in the above embodiments, the first model can be used to predict the UE's location information at a target time based on historical location information. The target time can be, for example, the first moment. The first model can be pre-trained. The first model can be a long short-term memory (LSTM) network model or a gated recurrent unit (GRU) network model, etc. The UE can pre-divide the model training dataset into training, validation, and test sets proportionally. The UE can use the training set to train the first model.

[0299] The User Interface (UE) can use a test set to test the trained first model to verify its accuracy or to tune its parameters before retraining. For example, the UE can input the test set into the trained first model, which can output multiple predicted values. The UE can calculate the root mean square error (RMSE) between each of the predicted values ​​and its corresponding true value. Taking Q predicted values ​​as an example, the RMSE can satisfy the formula:

[0300]

[0301] in, Let q be the predicted value. Let q be the actual value corresponding to the q-th predicted value. Q is a positive integer.

[0302] If the root mean square error (RMSE) is less than a preset error threshold, the UE can use historical location information from the storage queue for initial location prediction. If the RMSE is greater than or equal to the preset error threshold, the UE can tune the first model and retrain it until the RMSE is less than the preset error threshold. A RMSE less than the preset error threshold indicates that the trained first model has high accuracy and can be used for location prediction. Tuning the first model can include adjusting its hyperparameters, network structure, and / or the step size of the sliding window.

[0303] In one possible implementation, the first time delay and the first frequency shift can be a set of time delays and frequency shifts selected by the UE from the estimated time delay and frequency shift and the predicted time delay and frequency shift based on the first signal and multiple historical location information of the UE. For the specific implementation principle of selecting a set of time delays and frequency shifts from the estimated time delay and frequency shift and the predicted time delay and frequency shift, please refer to Example 3.

[0304] In this context, multiple historical location information corresponds to multiple historical moments. Multiple historical moments can be, for example, the L moments in Example 2.

[0305] Example 3:

[0306] For example, the estimated time delay is, for instance, a third time delay τ1. The predicted time delay is, for instance, a fourth time delay τ2. The estimated frequency shift is, for instance, a fourth frequency shift f. D1 The predicted frequency shift, for example, is the fifth frequency shift f. D2 Example 3 may include S1021, S1022, and S1023.

[0307] S1021. The UE can determine the third time delay and the fourth frequency shift based on the first signal. The specific implementation principle of S1021 can be found in the specific implementation principle of Example 1 above, and will not be repeated here.

[0308] S1022: The UE can determine the fourth time delay and fifth frequency shift corresponding to the first moment based on multiple historical location information. The specific implementation principle of S1022 can be found in Example 2 above, and will not be repeated here.

[0309] S1023, The UE can determine whether the reference signal receiving power (RSRP) of the first signal is less than the first threshold, and determine whether the second duration from the latest historical moment to the first moment among multiple historical moments is less than the second threshold.

[0310] The first threshold can be called the signal power threshold RSRP. th The first threshold can be -95 dBm, or any other value besides -95. The second duration can be called the prediction duration. The second threshold can be called the prediction duration threshold T. th The second threshold can be 30 seconds, or any other value besides 30. This application does not limit the specific values ​​of the first and second thresholds.

[0311] If RSRP is less than the first threshold and the second duration is less than the second threshold, the first delay is determined to be the fourth delay, and the first frequency shift is determined to be the fifth frequency shift.

[0312] If RSRP is greater than or equal to the first threshold, and / or the second duration is greater than or equal to the second threshold, the first delay is determined as the third delay, and the first frequency shift is determined as the fourth frequency shift.

[0313] For details on the implementation principle of S1023, please refer to [link / reference]. Figure 4 The illustrated embodiment. Figure 4 This is a schematic diagram illustrating a process for selecting delay and frequency shift according to an embodiment of this application. S1023 may include, for example: Figure 4 S401-S404 are shown.

[0314] S401 and UE can extract RSRP and the second duration.

[0315] For example, upon receiving an SSB signal, the UE can measure the SSB signal power RSRP. The UE can calculate the second duration δ2 by combining the first time point and the time when the UE most recently determined its GNSS position. Taking the time when the UE most recently determined its GNSS position as T0 as an example, the second duration δ2 can satisfy the formula:

[0316] δ2=T d1 - T0

[0317] S402, the UE can determine whether RSRP is less than the first threshold and whether δ2 is less than the second threshold.

[0318] S403. When RSRP < the first threshold and δ2 < the second threshold, the UE can be determined as having the first delay. For the fourth delay and determine the first frequency shift For the fifth frequency shift That is, the UE can determine:

[0319] ( , ) = ( , )

[0320] If RSRP < the first threshold and δ2 < the second threshold, it indicates that the accuracy of the predicted latency and frequency shift may be higher than the accuracy of the estimated latency and frequency shift. That is, compared to the estimated latency, the predicted latency is closer to the actual transmission latency between the UE and the LEO satellite. Compared to the estimated frequency shift, the predicted frequency shift is closer to the actual Doppler frequency shift between the UE and the LEO satellite.

[0321] S404. When RSRP ≥ the first threshold and / or δ2 ≥ the second threshold, the UE can determine the first delay. For the third delay and determine the first frequency shift For the fourth frequency shift That is, the UE can determine:

[0322] ( , ) = ( , )

[0323] If RSRP ≥ the first threshold and / or δ2 ≥ the second threshold, it indicates that the accuracy of the estimated latency and frequency shift may be higher than the accuracy of the predicted latency and frequency shift. That is, compared to the predicted latency, the estimated latency is closer to the actual transmission latency between the UE and the LEO satellite. Compared to the predicted frequency shift, the estimated frequency shift is closer to the actual Doppler frequency shift between the UE and the LEO satellite.

[0324] As shown in Example 3, the access method provided in this application embodiment allows the UE to estimate the time delay and frequency shift based on a first signal. The UE can also predict the time delay and frequency shift based on multiple GNSS locations at multiple historical times. The UE can measure the RSRP of the SSB signal in the first signal and calculate a second duration δ2 from the time the UE obtains its most recent UE location based on the GNSS signal to the first time. The UE can determine whether RSRP < a first threshold and δ2 < a second threshold.

[0325] RSRP < the first threshold indicates that the SSB signal strength in the first signal is low, and the accuracy of the time delay and frequency shift estimated based on the SSB signal in the first signal may be low. RSRP ≥ the first threshold indicates that the SSB signal strength in the first signal is high, and the accuracy of the time delay and frequency shift estimated based on the SSB signal in the first signal is high.

[0326] If δ2 < the second threshold, it indicates that the time from the UE's GNSS failure to the first moment is relatively short, resulting in a large number of GNSS locations among the historical location information in the storage queue used for delay and frequency shift prediction, or even that all historical location information consists of GNSS locations. The accuracy of GNSS locations can be higher than the accuracy of predicted location information. When δ2 < the second threshold, the accuracy of delay and frequency shift prediction based on multiple historical location information in the storage queue is relatively high. When δ2 ≥ the second threshold, it indicates that the time from the UE's GNSS failure to the first moment is relatively long, and since the storage queue is a first-in-first-out queue, there may be a large number of predicted location information in the storage queue. The accumulation of errors in the predicted location information may result in lower accuracy of delay and frequency shift prediction based on multiple historical location information in the storage queue.

[0327] Therefore, when RSRP < the first threshold and δ2 < the second threshold, the predicted latency and frequency shift are closer to the actual transmission latency and frequency shift between the UE and the LEO satellite than the estimated latency and frequency shift. The UE can determine the predicted latency (e.g., ) is the first time delay (e.g. ), determine the predicted frequency shift (e.g. ) is the first frequency shift (e.g. When RSRP ≥ the first threshold and / or δ2 ≥ the second threshold, the estimated latency and frequency shift are closer to the actual transmission latency and frequency shift between the UE and the LEO satellite than the predicted latency and frequency shift. The UE can determine the estimated latency (e.g., () is the first delay And determine the estimated frequency shift (e.g. ) is the first frequency shift This improves the accuracy of the first time delay and first frequency shift between the UE and the LEO satellite at the first moment, thereby enhancing the effectiveness of uplink time-frequency pre-compensation based on the first time delay and first frequency shift, and ultimately increasing the success rate of access attempts.

[0328] As shown in Example 3, the embodiments of this application use a combination of signal estimation delay and frequency shift method and historical location prediction delay and frequency shift method to obtain more accurate delay and Doppler frequency shift estimates, thereby improving the effectiveness of time-frequency pre-compensation based on the more accurate delay and Doppler frequency shift estimates and increasing the success rate of terminal equipment accessing NTN.

[0329] Next, S102 will be explained in detail.

[0330] For example, SIB1 may also carry the PRACH occasion configured by the network. The PRACH occasion can be referred to as the target time slot configured for PRACH, for example, the Xth time slot after receiving the SSB. Upon receiving SIB1, the UE can read the target time slot configured for PRACH from SIB1. The UE can then determine the target time slot based on a first delay and the SSB signal reception time t. rx The target time slot configured with PRACH determines the time t at which the network expects to receive the PRACH signal. rx_net The network expects to receive the PRACH signal at time t. rx_net The formula can be satisfied:

[0331]

[0332] UE can be set to the second TA. Adjust the transmission time of the PRACH signal to Furthermore, the UE can adjust the frequency by an amount of -f. DTd1 Adjust the frequency of the PRACH signal. The UE can adjust the frequency at a time of... At that time, a frequency-adjusted PRACH signal is sent to the LEO satellite to initiate the first access attempt.

[0333] Optionally, the UE can be based on The time t for receiving the SSB signal rx Time offset as specified in 3GPP protocol TS 38.214 Determine the timing T for sending the PRACH signal in the first access attempt. PRACH-1 T PRACH-1 The formula can be satisfied:

[0334]

[0335] The UE can be adjusted by a frequency amount of -f DTd1 Adjust the frequency of the PRACH signal, and at T PRACH-1 It continuously sends frequency-adjusted PRACH signals to LEO satellites to initiate the first access attempt.

[0336] To improve the success rate of initial access for terminal devices in the event of GNSS failure, some implementations pre-configure a common location reference point (CNPPT) on the LEO satellite. The CNPPT, or simply reference point, is located within the LEO satellite's serving beam. The serving beam can be simply referred to as the beam. For example, the reference point may be located within the LEO satellite's beam coverage area.

[0337] LEO satellites can broadcast reference points to all terminal devices within the beam coverage area of ​​the LEO satellite. Terminal devices (such as UEs) can use the reference points for pre-compensation of time delay and frequency offset. For example, terminal devices can use the transmission delay and Doppler frequency shift between the reference point and the LEO satellite to perform uplink time and frequency pre-compensation.

[0338] Because LEO satellites have a large beam coverage radius, the distance between the reference point and the actual location of the terminal equipment may be considerable, potentially resulting in significant residual time delay and / or residual frequency offset. Taking the uplink signal as a PRACH signal as an example, a large residual time delay may exceed the search range of the PRACH detection window, preventing the LEO satellite from receiving the PRACH signal and causing initial access failure.

[0339] In this embodiment, initial access can also be referred to as random access. Taking PRACH access as an example, to address the issue of residual delay exceeding the search range of the PRACH detection window when terminal devices perform time-frequency pre-compensation based on a single LEO satellite reference point, and to further improve the initial access success rate of terminal devices, multiple reference points can be pre-deployed within the LEO satellite beam. The LEO satellite can broadcast multiple reference points within its service beam to all terminal devices within the LEO satellite's beam coverage area. The terminal device can select the reference point closest to it from the multiple reference points for delay and frequency offset pre-compensation. This can improve the accuracy of delay and frequency offset compensation in the first few PRACH access attempts, reduce the number of random access attempts, and improve the PRACH access success rate.

[0340] Figure 5 This application provides a schematic diagram of a reference point deployment.

[0341] For example, using LEO satellites as an example Figure 5 Taking satellite 501 as an example, Figure 5 The diagram shows the operating speed V of satellite 501, its direction of travel, its beam coverage area 503, and multiple reference points deployed within the beam coverage area 503. The direction of travel of satellite 501, for example... Figure 5 The middle arrow indicates direction. Multiple reference points, such as... Figure 5Reference points 502a, 502b, 502c, 502d, 502e, 502f, and 502g are shown. These multiple reference points are located on the ground projection axis 504 along the satellite's direction of motion. Reference point 502d is located at the center of the beam coverage area 503, i.e., at the beam center. Reference point 502d can be referred to as the beam center reference point.

[0342] Optionally, taking an LEO satellite orbital altitude of 800 km, a carrier frequency of 2 GHz, and a service beam coverage radius of 50 km as an example, 11 reference points can be deployed along the ground projection axis of the satellite's motion direction within the beam, with a spacing of 10 km between the reference points.

[0343] Figure 6 This illustration shows another flowchart of the access method provided in an embodiment of this application. The following is in conjunction with... Figure 5 and Figure 6 The solutions provided in the embodiments of this application will be described.

[0344] For example, still referring to the terminal device as UE and the satellite as a LEO satellite, such as Figure 6 As shown, the access method provided in this application embodiment may include S101-S102 and S601, wherein the specific implementation principle of S101-S102 can be found in [reference needed]. Figure 1 The specific implementation principle of the illustrated embodiment will not be elaborated here.

[0345] S601. If the first access attempt fails, the UE may initiate a second access attempt. The second access attempt uses the delay and frequency shift of the common location reference point for uplink time-frequency pre-compensation. The common location reference point is selected from multiple common location reference points of satellites (such as LEO satellites).

[0346] The common location reference point used in the second access attempt is selected from multiple common location reference points in a reference point selection order. The reference point selection order indicates the order in which the distance between the common location reference point and the terminal device (i.e., UE) increases.

[0347] For example, the first delay and the first frequency shift are the transmission delay and frequency shift between the UE and the LEO satellite at the first time point. The reference point selection order is determined based on the first delay, the first frequency shift, and the second delay and second frequency shift of each of the multiple common location reference points of the LEO satellite at the first time point.

[0348] For example, the UE can determine the reference point selection order from multiple reference points based on a first time delay, a first frequency shift, and the second time delay and second frequency shift of each of the multiple reference points of the LEO satellite at a first time moment. The reference point selection order can represent the order in which the distance between the reference points and the UE increases from smallest to largest.

[0349] For example, the first signal may include reference point information of multiple common location reference points within the beam range of a satellite (such as an LEO satellite). The reference point information is used to determine the selection order of the reference points.

[0350] For example, the first signal may include SIB19. Reference point information may be carried in SIB19.

[0351] For example, reference point information for multiple common location reference points within the beam range of an LEO satellite may include reference times. This includes time delay and frequency shift data for each reference point within multiple common location reference points across the LEO satellite's beamwidth at a reference time. The time delay data may include a first transition time (TA), its drift rate, and its drift acceleration. The frequency shift data may include a third frequency shift, its drift rate, and its drift acceleration.

[0352] Reference point information of multiple common position reference points within the satellite's beam range can be used to determine the second time delay and second frequency shift of each of the multiple common position reference points at the first moment.

[0353] For example, before or after S102, the terminal device can determine the reference point selection order based on a first time delay, a first frequency shift, and the second time delay and second frequency shift of each of the multiple common location reference points of the satellite at a first moment. The common location reference points can be used for access attempts.

[0354] For example, when the reference point information of the LEO satellite is obtained, the UE can determine the second time delay and second frequency shift of each of the multiple reference points at the first time based on the first time and the time delay data and frequency shift data of each reference point at the reference time.

[0355] For example, taking multiple reference points as I reference points, where I is a positive integer, SIB19 can also carry the time delay data and frequency shift data of the i-th reference point among the multiple reference points of the LEO satellite at the reference time. i is the sequence number of the common location reference point. i can be any positive integer from 1 to I. For example, i = 1, 2, ..., I. The specific value of I is not limited in the embodiments of this application.

[0356] UE can be based on the first time T d1Using the time delay and frequency shift data of the i-th reference point, determine the second time delay and second frequency shift of the i-th reference point at the first moment. The second time delay and second frequency shift of the i-th reference point at the first moment are positively correlated with the first duration from the reference moment to the first moment, and are also positively correlated with the time delay and frequency shift data of the i-th reference point.

[0357] The i-th reference point at time T d1 Second delay The formula can be satisfied:

[0358]

[0359] The i-th reference point at time T d1 Second frequency shift The formula can be satisfied:

[0360]

[0361] in, For reference time, For the i-th reference point The first TA at any moment For the i-th reference point The drift rate of the first TA at time t. For the i-th reference point The drift acceleration of the first TA at time moment, For the i-th reference point The third frequency shift at time, For the i-th reference point The drift rate of the third frequency shift at time t. For the i-th reference point The drift acceleration of the third frequency shift at time t.

[0362] If the second time delay and second frequency shift of each of the multiple reference points are determined at the first moment, the UE can execute S6011-S6012 to determine the reference point selection order.

[0363] S6011, the UE can calculate the distance between the first coordinate point and the second coordinate point of each of multiple reference points in a coordinate system established by time delay and frequency shift.

[0364] The coordinates of the first coordinate point of the reference point are determined based on the second time delay and the second frequency shift corresponding to that reference point. The coordinates of the second coordinate point are determined based on the first time delay and the first frequency shift.

[0365] For example, a coordinate system established using time delay and frequency shift can be called a time-frequency coordinate system. The first coordinate point of the i-th common location reference point among I common location reference points can be (…). , ), where i is the index of the common location reference point. Let be the time delay axis coordinate value of the i-th common location reference point in the time-frequency coordinate system. Let be the frequency shift axis coordinate value of the i-th common location reference point in the time-frequency coordinate system. It is obtained by normalizing the second time delay of the i-th common location reference point. It is obtained by normalizing the second frequency shift of the i-th common position reference point.

[0366] The second coordinate point is ( ). This represents the time delay axis coordinate value of the first time delay in the time-frequency coordinate system. This represents the frequency shift axis coordinate value of the first frequency shift in the time-frequency coordinate system. It is obtained by normalizing the first delay. It is obtained by normalizing the first frequency shift.

[0367] The distance between the first coordinate point and the second coordinate point can be the Euclidean distance between the first coordinate point and the second coordinate point.

[0368] For example, the UE can specify the i-th reference point R. i The second time delay and the second frequency shift are normalized respectively to obtain the first coordinate point of the i-th reference point as ( , ).

[0369] The formula can be satisfied:

[0370]

[0371] The formula can be satisfied:

[0372]

[0373] in, This is the default value. This is the default value. This is the default value. This is the default value.

[0374] UE can handle the first delay and the first frequency shift After normalization, the second coordinate point is ( ).

[0375] The formula can be satisfied:

[0376]

[0377] The formula can be satisfied:

[0378]

[0379] For example, taking the distance between the first coordinate point and the second coordinate point as the Euclidean distance, the first coordinate point of the i-th reference point ( , ) and the second coordinate point ( The distance S between them i The formula can be satisfied:

[0380]

[0381] S6012, the UE can sort multiple reference points by distance to obtain a first sequence. The first sequence indicates the order in which the distances between the reference points and the UE increase from smallest to largest. The reference points selected in sequence can be selected sequentially according to the first sequence. The order indicated by the first sequence is the reference point selection order.

[0382] The distance between the first and second coordinate points of a reference point can be called the relative distance between the reference point and the UE, or simply the relative distance of the reference point. The first sequence can be obtained by sorting multiple reference points according to their relative distances. The actual distance between a reference point and the UE is positively correlated with the relative distance of the reference point. The larger the relative distance of the reference point, the larger the actual distance between the reference point and the UE. The smaller the relative distance of the reference point, the smaller the actual distance between the reference point and the UE.

[0383] If the reference points in the first sequence are arranged in ascending order of relative distance, then the order from front to back shown in the first sequence is the reference point selection order.

[0384] If the reference points in the first sequence are arranged in descending order of relative distance, then the order from back to front shown in the first sequence is the reference point selection order.

[0385] With multiple reference points including Figure 5 The reference points 502a, 502b, 502c, 502d, 502e, 502f, and 502g shown are used as an example, with the first sequence being {reference point 502a, reference point 502b, reference point 502c, reference point 502d, reference point 502e, reference point 502f, reference point 502g}.

[0386] When the reference points in the first sequence are arranged in ascending order of relative distance, reference point 502a has the smallest relative distance, and reference point 502g has the largest relative distance. The order in which the reference points are selected, i.e., the order from front to back shown in the first sequence, can be: reference point 502a → reference point 502b → reference point 502c → reference point 502d → reference point 502e → reference point 502f → reference point 502g.

[0387] When the reference points in the first sequence are arranged in descending order of relative distance, reference point 502a has the largest relative distance, and reference point 502g has the smallest relative distance. The order of reference point selection, i.e., the order from back to front shown in the first sequence, can be: reference point 502g → reference point 502f → reference point 502e → reference point 502d → reference point 502c → reference point 502b → reference point 502a.

[0388] In this way, when the UE selects a reference point from multiple reference points in the order of reference point selection for access attempts, the UE can prioritize selecting the reference point closer to it. The closer the reference point selected for the access attempt is to the UE, the smaller the residual latency, which reduces the probability of the residual latency exceeding the PRACH detection window, and thus reduces the probability of the LEO satellite failing to receive the uplink signal sent by the UE. This improves the success rate of the LEO satellite receiving the uplink signal sent by the UE, thereby improving the access success rate. Consequently, the number of access attempts can be reduced.

[0389] Based on the first time delay, the first frequency shift, and the second time delay and second frequency shift of each of the multiple reference points deployed within the LEO satellite beam at the first moment, the order in which reference points are selected from the multiple reference points is determined. This order can represent the order in which the distance between the reference points and the terminal device increases from smallest to largest. The terminal device can sequentially select reference points in order of increasing distance between the reference points and the terminal device to perform time-frequency pre-compensation and initiate PRACH access attempts. Since the shorter the distance between the reference point and the terminal device, the higher the success rate of the terminal device's access attempt based on that reference point. The reference point selection order determined in this embodiment is the order in order of increasing distance between the reference points and the terminal device. Selecting reference points in this order for access attempts allows the terminal device to preferentially select reference points with shorter distances to the terminal device for access attempts. This can improve the accuracy of time delay and frequency offset compensation in the earlier PRACH access attempts, reduce the number of random access attempts, and improve the PRACH access success rate.

[0390] For example, such as Figure 6As shown, if the reference point selection order is determined and the first access attempt fails, the UE can initiate a second access attempt. The second access attempt involves time-frequency pre-compensation of the time delay and frequency shift of the reference points selected from multiple reference points on the LEO satellite according to the reference point selection order.

[0391] For example, if the first access attempt fails, the UE can sequentially select reference points from multiple reference points according to the reference point selection order. For each selected reference point, the UE can use the delay and frequency shift of that reference point at the target time to perform uplink time-frequency pre-compensation and make a second access attempt. This improves the access success rate and reduces the number of access attempts, enabling the UE to quickly establish an RRC connection with the LEO satellite.

[0392] The target time can be either the first time or a time later than the first time. The time delay of the i-th reference point at the target time T is also considered. The formula can be satisfied:

[0393]

[0394] Frequency shift of the i-th reference point at the target time T The formula can be satisfied:

[0395]

[0396] For example, taking the reference point selected by the UE as the i-th reference point, the UE can determine the third TA of the PRACH signal as... The UE can determine the frequency adjustment amount of the PRACH signal as - This allows for time-frequency pre-compensation of the PRACH signal by using the time delay and frequency shift of the i-th reference point.

[0397] UE can be based on the third TA. Adjust the transmission time of the PRACH signal and adjust the frequency by - Adjust the frequency of the PRACH signal. The UE can do this by pressing... The adjusted PRACH signal transmission time is sent to the LEO satellite by pressing - The PRACH signal is frequency-adjusted to initiate a second access attempt.

[0398] For example, the network's expected reception time of the PRACH signal determined by the UE is still taken as... For example, the UE can be set to the third TA. Adjust the transmission time of the PRACH signal to And the UE can adjust the amount by frequency as - Adjust the frequency of the PRACH signal. The UE can adjust the frequency at a time of... At that time, send a press-to- The PRACH signal is frequency-adjusted to initiate a second access attempt.

[0399] Optionally, the UE can be based on The time t for receiving the SSB signal rx Time offset as specified in 3GPP protocol TS 38.214 Determine the timing of sending the PRACH signal for the second access attempt. . The formula can be satisfied:

[0400]

[0401] The UE can adjust the frequency by - Adjust the frequency of the PRACH signal, and at T PRACH-2 It continuously sends frequency-adjusted PRACH signals to LEO satellites to initiate a second access attempt.

[0402] For example, if the first access attempt fails, the UE may initiate a second access attempt for the first time. The first initiated second access attempt uses the delay and frequency shift of the first reference point for uplink time-frequency pre-compensation.

[0403] If the initial second access attempt fails, the UE can initiate a second access attempt again. The second access attempt uses the delay and frequency shift of the second reference point for uplink time-frequency pre-compensation.

[0404] The first reference point and the second reference point are selected sequentially from multiple common location reference points according to the reference point selection order. The distance between the first reference point and the terminal device (i.e., the UE) is less than the distance between the second reference point and the terminal device. The first reference point can be the reference point ranked first in the sequence.

[0405] In this way, if the first access attempt fails, reference points are selected sequentially from multiple satellite reference points according to the reference point selection order, and a second access attempt is made accordingly. The distance between the first reference point and the terminal device is less than the distance between the second reference point and the terminal device. This means that the distance between the reference point used in the earlier second access attempt and the terminal device is smaller than the distance used in the later second access attempt, resulting in a higher success rate for the earlier second access attempt. If the earlier second access attempt based on the first reference point is successful, there is no need to make a second access attempt based on the second reference point, reducing the number of access attempts and enabling the terminal device to quickly access the satellite and achieve satellite communication. Rapid satellite access for the terminal device can be understood as the terminal device accessing the NTN where the satellite is located.

[0406] For example, if the second access attempt fails again, the UE can initiate a second access attempt once more. The second access attempt uses the delay and frequency shift of the third reference point for uplink time-frequency pre-compensation.

[0407] The first, second, and third reference points were selected sequentially from multiple common location reference points in the order of reference point selection. The distance between the second reference point and the terminal device is less than the distance between the third reference point and the terminal device.

[0408] In this way, the distance between the second reference point and the terminal device is less than the distance between the third reference point and the terminal device. This means that the distance between the reference point used in the earlier second access attempt and the terminal device is smaller than the distance used in the later second access attempt, resulting in a higher success rate for the earlier second access attempt. If the earlier second access attempt based on the second reference point is successful, there is no need to perform a second access attempt based on the third reference point, which reduces the number of access attempts and facilitates faster satellite access for the terminal device to achieve satellite communication.

[0409] Optionally, starting from the first access attempt, the UE can terminate the access attempt when the most recent access attempt fails and the number of access attempts reaches the third threshold. This reduces the probability of shortened UE battery life due to excessive invalid access attempts, thus improving user experience. An invalid access attempt can be understood as an access attempt that has failed. The third threshold can be 4 times, or any other value besides 4. This application embodiment does not limit the specific value of the third threshold.

[0410] like Figure 6As shown in the embodiments of this application, the access method provided allows the terminal device (such as a UE) to receive satellite signals (such as LEO satellites) when GNSS fails. The satellite signal transmitted by the satellite is, for example, a first signal. The terminal device can determine a first time delay and a first frequency shift at a first moment based on the first signal and / or multiple historical location information of the terminal device. This allows the terminal device to use the first time delay and the first frequency shift to perform uplink time-frequency pre-compensation and initiate a first access attempt. The terminal device can also determine the reference point selection order based on the first time delay, the first frequency shift, and the second time delay and second frequency shift of multiple reference points of the satellite at the first moment. The reference point selection order is the order in which the distance between the reference points and the terminal device increases, so that the terminal device can preferentially select the reference point closer to the terminal device from multiple reference points according to the reference point selection order for a second access attempt, thereby improving the success rate of the second access attempt.

[0411] Given the first time delay and the first frequency shift, the terminal device can use these parameters for uplink time-frequency pre-compensation and initiate a first access attempt. If the first access attempt fails, the terminal device can select a reference point from multiple reference points in the reference point selection order for a second access attempt. If the first access attempt succeeds, the terminal device can skip the second access attempt, reducing the number of access attempts and enabling the terminal device to quickly establish an RRC connection with the satellite. A successful first access attempt is indicated by a "access successful" result.

[0412] The reference point selection order allows the terminal device to prioritize access attempts from reference points closer to it. This reduces the probability of residual latency exceeding the satellite's (e.g., LEO satellite) PRACH detection window, thereby reducing the probability of the satellite failing to receive uplink signals from the terminal device. By initiating access attempts based on the latency and frequency shift of the reference points selected according to the reference point selection order, the terminal device can improve the success rate of the satellite receiving uplink signals from the terminal device. This, in turn, increases the access success rate and reduces the number of access attempts, enabling the terminal device to quickly establish an RRC connection with the satellite.

[0413] The embodiments of this application determine the reference point selection order by using a first time delay, a first frequency shift, and the second time delay and second frequency shift of each of the multiple reference points of the satellite at a first moment. This provides richer parameters for multiple reference point selection and can improve the accuracy of reference point selection. The scheme provided in the embodiments of this application introduces a reference point sorting operation and uses the results of dual-parameter estimation to determine this order, providing a basis for time delay and frequency offset compensation for multiple access attempts.

[0414] In one possible implementation, if the UE terminates the access attempt, the UE can determine whether the GNSS service is still ineffective from the time the UE terminates the access attempt until the duration B is reached.

[0415] If the UE determines that GNSS service is not down, it can acquire GNSS signals and determine its GNSS location based on these signals. This allows it to determine the transmission delay and frequency shift between the UE and the LEO satellite and initiate an access attempt. This enables timely monitoring of the UE's GNSS status after the UE terminates the access attempt, facilitating the timely establishment of a communication connection with the LEO satellite once GNSS service is restored (i.e., GNSS is not down).

[0416] If the UE determines that GNSS service is still unavailable, the UE can receive a second signal transmitted by LEO satellites. This second signal can be used for communication. The second signal may include SSB and SIB, etc.

[0417] The UE can determine the fifth time delay and the sixth frequency shift at the second time point based on the second signal and / or multiple historical location information of the UE. The second time point is later than the first time point.

[0418] The UE can use the fifth delay and the sixth frequency shift for time-frequency pre-compensation, perform uplink time-frequency pre-compensation, and initiate the first access attempt again.

[0419] The specific implementation principle of this embodiment can be found in the above embodiment, whereby the UE receives a first signal, determines the time delay and frequency shift at the first moment based on the first signal and / or multiple historical location information of the UE, and performs a first access attempt using the time delay and frequency shift at the first moment.

[0420] This allows the UE to re-determine the fifth time delay and sixth frequency shift at the second moment, based on the re-received signals from the LEO satellite and / or multiple historical location information of the terminal device, even if the UE's environment changes after the UE terminates its access attempt. This enables the UE to attempt access again using the newly determined time delay and frequency shift (such as the fifth and sixth time delays). When the UE's environment has minimal impact on the LEO satellite signal, using the newly determined time delay and frequency shift can improve the success rate of UE accessing the LEO satellite. UE access to the LEO satellite can be understood as the UE accessing the NTN where the LEO satellite is located.

[0421] In one possible implementation, if the first access attempt fails, the UE can select a reference point according to the reference point selection order. The UE can then initiate a second access attempt based on the latency and frequency shift of the reference point selected in the order. For example, the UE can initiate a second access attempt based on the latency and frequency shift of the reference point selected in the order at a second time moment. The determination of the latency and frequency shift of the reference point at the second time moment can be found in the principle for determining the latency and frequency shift of the reference point at the target time moment. The specific implementation principle of this embodiment can be found in the specific implementation principle of the second access attempt in the above embodiments.

[0422] In this way, if the first access attempt fails, the UE can initiate a second access attempt based on the time delay and frequency shift of the reference point selected in the reference point selection order at the second moment, which can also improve the success rate of the UE accessing the LEO satellite.

[0423] Figure 7 This illustration shows another flowchart of the access method provided in an embodiment of this application. The following is in conjunction with... Figure 7 The solutions provided in the embodiments of this application will be described.

[0424] like Figure 7 As shown, the access method provided in this application embodiment may include S701, S101-S103, S601-S602, or may include S701, S101-S102, S601, S103, and S602. The specific implementation principles of each step in S101-S103 and S601-S602 can be found in the corresponding implementation principles of the steps in the above embodiments, and will not be repeated here.

[0425] S701: The satellite side can calculate the TA and FO parameters corresponding to each reference point based on the configuration information of multiple configured reference points. The TA and FO parameters corresponding to each reference point can be distributed via SIB.

[0426] For example, a satellite can calculate the time delay and frequency shift data of each of the multiple reference points at the reference time based on the configuration information of the multiple reference points.

[0427] The S702 satellite can transmit signals such as SSB and SIB.

[0428] For example, a satellite can periodically transmit SSB signals within each beam using a multi-beam antenna. The SIB signals can be transmitted via a PDSCH channel. For a detailed explanation of the implementation principle of S702, please refer to the detailed implementation principle of S101.

[0429] S703, the UE side can receive relevant signals.

[0430] For example, referring to Example 1, in the event of GNSS failure, after the UE captures the SSB signal, it completes time-frequency synchronization, locks onto the cell identifier, demodulates the PBCH channel in the SSB, and obtains the Master Information Block (MIB). Based on the MIB's scheduling parameters (such as indication information), the UE can receive SIB1 on the specified time-frequency resources. Following the guidance of SIB1, the UE can receive other required SIB information on the corresponding time-frequency resources. Other SIB information may, for example, be SIB9 and / or SIB19.

[0431] S704, the UE side performs time delay and Doppler frequency shift estimation.

[0432] For example, the UE can estimate the UE delay frequency shift based on the received signal, estimate the UE delay frequency shift based on the location prediction result, and select the final delay frequency shift estimate.

[0433] For example, when the UE receives a signal transmitted from the satellite, the UE can perform a UE delay and frequency shift estimation process based on the received signal to obtain the estimated delay and frequency shift, such as obtaining the third delay and the fourth frequency shift. For the specific implementation principle, please refer to the specific implementation principle of estimating the third delay and the fourth frequency shift based on the SSB signal in Example 1.

[0434] The UE can perform a location-based delay and frequency shift estimation process to obtain the predicted delay and frequency shift, such as the fourth delay and the fifth frequency shift. For a detailed explanation of its implementation principle, please refer to Example 2, which demonstrates how to determine the fourth delay and the fifth frequency shift at the first moment based on multiple historical location information.

[0435] The UE can choose the final time delay frequency shift estimate. For the specific implementation principle, please refer to Example 3.

[0436] S705, Reference point selection.

[0437] For example, the UE can execute a reference point sorting process to determine the reference point selection order. The specific implementation principle can be found in the specific implementation principle of S601.

[0438] S706, UE side conducts access attempt.

[0439] For example, the UE first attempts to access the system using the estimated TA and FO. If this fails, it then attempts to access the system again using the TA and FO corresponding to each reference point in sequence.

[0440] For example, the UE can use a first delay and a first frequency shift to make a first access attempt. If the first access attempt fails, the UE can select the delay and frequency shift of the reference point at the target time according to the reference point selection order to make a second access attempt.

[0441] Figure 7 The technical effects of the illustrated embodiments can be seen in [reference needed]. Figure 6 The specific implementation principle of the illustrated embodiment will not be elaborated here.

[0442] The following example uses a vehicle traveling on a highway, with the UE as an in-vehicle device. Figure 8 The solutions provided in the embodiments of this application will be described. Figure 8 This is another flowchart illustrating the access method provided in the embodiments of this application.

[0443] S801, Configure and distribute reference points on the satellite side.

[0444] For example, taking a LEO satellite with a service beam coverage radius of 50 km and I = 11 as an example, the LEO satellite can deploy one reference point every 10 km along the ground projection axis of the satellite's motion direction within the 50 km service beam, for a total of 11 reference points. The 11 reference points can be numbered R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, and R11 in sequence. In this embodiment, the LEO satellite can be simply referred to as a satellite.

[0445] The satellite can calculate the parameters of each reference point; for example, the satellite can calculate the parameters of the i-th reference point. , , , , , and reference time And it was issued in SIB19.

[0446] S802, the vehicle-mounted equipment can capture SSB and SIB signals.

[0447] For example, a vehicle traveling at 100 km / h on a highway enters a tunnel, and the onboard equipment triggers a GNSS failure state to capture SSB and SIB signals. For instance, after entering the tunnel, if the onboard equipment determines that GNSS is disabled, it can set its GNSS state to GNSS failure. While in GNSS failure mode, the onboard equipment can capture SSB and SIB signals broadcast by LEO satellites.

[0448] When the vehicle-mounted equipment captures the SSB signal transmitted by the LEO satellite, it can achieve time-frequency synchronization through the PSS and SSS sequences, lock the cell identifier, and demodulate the MIB information in the PBCH channel. The vehicle-mounted equipment can then receive SIB1 on the designated time-frequency resources according to the MIB scheduling parameters. Following the SIB1 instructions, the vehicle-mounted equipment can receive SIB19 to obtain the reference point parameters, satellite ephemeris, and time reference carried by SIB19. .

[0449] S803. The vehicle-mounted equipment can perform time delay and Doppler frequency shift estimation based on the received signal. The implementation principle can be found in Example 1, which details the estimation of the third time delay and fourth frequency shift based on the SSB signal. The vehicle-mounted equipment can also calculate the received signal power RSRP, for example, by measuring the RSRP of the received SSB signal.

[0450] S804, vehicle-mounted equipment can predict latency and Doppler shift based on historical location.

[0451] For example, taking the GRU model as the first model, the vehicle-mounted device can read GNSS high-precision locations from 60 historical time points in its historical location storage queue. These GNSS high-precision locations are simply GNSS positions. The vehicle-mounted device can preprocess the read GNSS locations, such as performing position increment calculations and normalization, to obtain processed location data. The vehicle-mounted device can then input the processed location data into the trained GRU model to predict the location information for the first time point. The vehicle-mounted device can also calculate the second time duration δ2.

[0452] S805. The on-board equipment can select a set of time delays and frequency shifts from the estimated time delays and frequency shifts and the predicted time delays and frequency shifts. The specific implementation principle can be found in Example 3. The selected time delays and frequency shifts are, for example, the first time delay and the first frequency shift determined based on RSRP and the second duration δ2 in Example 3.

[0453] S806, Onboard equipment can sort reference points.

[0454] For example, the vehicle-mounted device can sort the reference points according to the selected time delay and Doppler frequency shift, and the distance between these values ​​and the time delay and Doppler frequency shift of the reference points, to obtain a first sequence. For the specific implementation principle of sorting the reference points to obtain the first sequence, please refer to the specific implementation principle of S601.

[0455] Taking I as 11 as an example, the first sequence could be {R4, R3, R5, R2, R6, R1, R7, R8, R9, R10, R11}. If the first sequence is arranged in ascending order of distance, the reference point selection order could be R4→R3→R5→R2→R6→R1→R7→R8→R9→R10→R11.

[0456] S807 and PRACH access attempts.

[0457] For example, taking a third threshold of 4 times as an example, the PRACH signal can be a PRACH access request. On the first attempt, the on-board device can use the final estimate, calculate TA and FO, and send a PRACH access request.

[0458] If the access attempt fails, a second attempt will be made: select the TA and FO parameters corresponding to the first reference point in the sorting list for the access attempt. If this is unsuccessful, other reference points will be tried in turn until the total number of access attempts reaches 4 without success, at which point the access attempt will be abandoned. If the access attempt is successful before the total number of access attempts reaches 4, the vehicle-mounted equipment can enter the subsequent random access process and uplink data transmission process.

[0459] For example, the on-board equipment can use a determined first time delay and a first frequency shift to calculate a second TA and a first frequency adjustment amount. Second TA = 2τ Td1 First frequency adjustment amount = -f DTd1 .

[0460] The on-board equipment can send a PRACH access request based on the second TA and the first frequency adjustment to initiate an initial access attempt. The specific implementation principle of the initial access attempt can be found in S103. The initial access attempt is also known as the first access attempt.

[0461] If the initial access attempt fails, the onboard equipment can select the reference point ranked first in the reference point selection order and perform a second access attempt based on its latency and frequency shift at the target time. For example, if the reference point selection order is R4→R3→R5→R2→R6→R1→R7→R8→R9→R10→R11, the first reference point in the ranking is reference point R4.

[0462] If the second access attempt fails, the on-board equipment can continue to select other reference points (such as reference point R3) in the order of reference point selection and perform a third access attempt based on the time delay and frequency shift at the target time.

[0463] If the third access attempt fails, the on-board equipment can continue to select other reference points (such as reference point R5) in the order of reference point selection to perform a fourth access attempt based on the time delay and frequency shift at the target time.

[0464] If the fourth access attempt fails, the onboard device can abandon the access attempt.

[0465] If the first, second, third, or fourth access attempts are successful, the on-board equipment can proceed to the subsequent random access process and uplink data transmission flow.

[0466] The second access attempt can be referred to as the second access attempt. The third access attempt can also be referred to as the second access attempt. The fourth access attempt can also be referred to as the second access attempt. For the specific implementation principle of the vehicle-mounted equipment performing the second, third and / or fourth access attempts, please refer to the specific implementation principle of S602, which will not be repeated here.

[0467] like Figure 8 As shown in the embodiment of this application, the access method allows LEO satellites to deploy multiple reference points every 10 km along the ground projection axis of the satellite's motion direction within the service beam. The satellite can calculate the parameters and reference time for each reference point. This information is then distributed via SIB19. In the event of GNSS failure on the vehicle-mounted equipment, the equipment can trigger a GNSS failure state. While in a GNSS failure state, the equipment can acquire SSB and SIB signals periodically transmitted by LEO satellites. The equipment can perform time delay and Doppler shift estimation based on the received signal, obtaining the estimated time delay and frequency shift. The equipment can also predict the time delay and Doppler shift based on historical location, obtaining the predicted time delay and frequency shift. Finally, the equipment can select a set of time delay and frequency shift from the estimated and predicted values.

[0468] The onboard equipment can sort the reference points according to the distance between the selected time delay and Doppler frequency shift and the time delay and Doppler frequency shift values ​​of the reference points, thus obtaining the reference point selection order. The onboard equipment can use the selected time delay and Doppler frequency shift to calculate TA and FO, and send a PRACH access request to realize the initial access attempt.

[0469] If the initial access attempt fails, the onboard device can select the first reference point in the reference point selection order (e.g., reference point R4) and use its latency and frequency shift at the target time for a second access attempt. If the second access attempt fails, the onboard device can continue selecting other reference points in the reference point selection order (e.g., reference point R3) and use their latency and frequency shift at the target time for a third access attempt. If the third access attempt fails, the onboard device can continue selecting other reference points in the reference point selection order (e.g., reference point R5) and use their latency and frequency shift at the target time for a fourth access attempt.

[0470] If the fourth access attempt fails, the on-board device may abandon the access attempt. If the first, second, third, or fourth access attempt is successful, the on-board device may proceed to the subsequent random access process and uplink data transmission flow.

[0471] The reference points are selected in ascending order of distance from the vehicle-mounted equipment. This allows the vehicle-mounted equipment to prioritize the closest reference point from multiple options for access attempts, improving the success rate of subsequent access attempts and enabling the vehicle-mounted equipment to establish a communication connection with the LEO satellite. If the initial access attempt is successful, the vehicle-mounted equipment does not need to attempt a second one, reducing the number of attempts and allowing for a faster communication connection. This ensures that even when the vehicle-mounted equipment's GNSS fails during high-speed driving, it can still establish a communication connection with the LEO satellite promptly, reducing the probability of the vehicle and equipment being unable to establish a communication connection with the network, thus affecting driving safety.

[0472] The first model can be, for example, an LSTM network model or a GRU network model. Taking the GRU network model as an example, the network structure parameters of the GRU network model can include: the sliding window length, for example, can be 10; the input feature vector dimension (feature_dim), for example, can be 10, and the input vector can be represented as (ΔT) in ΔX in ΔY in ΔZ in V xin V yin V zin A xin A yin A zin The input vector is, for example, ΔP in the above embodiment. l The number of hidden layer units (gate_size) can be, for example, 64, and the number of hidden layers (num_layers) can be, for example, 2. Hidden layers can be, for example, GRU-1 or GRU-2. The loss function (dropout) can be, for example, 0.1; the output layer vector dimension (out_steps) can be, for example, 10, and the output vector can be represented as (ΔT) out ΔX out ΔY out ΔZ out V xout V yout V zout A xout A yout Azout The output vector is, for example, ΔP in the above embodiment. Td1 .

[0473] For example, the network structure parameters of the GRU network model can be found in Table 1.

[0474] Table 1 Network structure parameters

[0475]

[0476] The training parameters for the GRU network model are shown in Table 2.

[0477] Table 2 Network training parameters

[0478]

[0479] The embodiments of this application do not limit the structure of the first model.

[0480] Some terminal devices may have a GNSS receiver chip and an NTN communication module. In one possible implementation, when the GNSS receiver chip determines that the GNSS service of the terminal device is unavailable, the GNSS receiver chip can set the GNSS status of the terminal device to an unavailable state. The GNSS receiver chip can transmit information indicating that the GNSS status is unavailable to the NTN communication module. The NTN communication module can execute the access method provided in the embodiments of this application to determine the time delay and frequency shift based on SSB and SIB signals transmitted by non-terrestrial devices (such as LEO satellites) in the NTN network when the terminal device is in a GNSS unavailable state, and perform uplink time-frequency compensation. This improves the success rate of accessing the NTN network when GNSS is unavailable.

[0481] The access method provided in this application can be applied to select reference points in GNSS failure scenarios to attempt access. Furthermore, the access method provided in this application can also be applied to scenarios where GNSS is subject to deception interference. When GNSS is subject to deception interference, the UE location result obtained from GNSS becomes unreliable, and delay and frequency pre-compensation cannot be performed based on the UE location obtained from GNSS. In this case, the reference point selection scheme in the access method provided in this application can be used to complete delay and frequency pre-compensation.

[0482] This application provides a communication system, which may include a satellite and a terminal device; the terminal device may be used to perform the actions performed by the UE in the above embodiments, and the satellite may be used to perform the actions performed by the LEO satellite in the above embodiments.

[0483] It should be noted that the module names involved in the embodiments of this application can all be defined as other names, as long as they can achieve the function of each module, and there are no specific restrictions on the module names. This application uses LEO satellites as an example of non-ground equipment in NTN for illustration, but this is not a limitation on non-ground equipment or NTN. In one possible implementation, non-ground equipment can also be MEO satellites, satellites other than LEO and MEO satellites, or other non-ground equipment besides satellites. This application does not limit the non-ground equipment.

[0484] In the solution provided in this application embodiment, the satellite side can add an information block to the SIB signal to indicate the transmission timing reference. This information block, for example, is an information block carrying reference point information. The solution provided in this application embodiment is compatible with existing NR and NTN related protocols.

[0485] The access method of the embodiments of this application has been described above. The apparatus for executing the above method provided in the embodiments of this application is described below. Those skilled in the art will understand that the methods and apparatus can be combined and referenced with each other, and the related apparatus provided in the embodiments of this application can execute the steps in the above access method.

[0486] The access method provided in this application can be applied to electronic devices with communication functions. Electronic devices include terminal devices, and the specific device form of the terminal device can be referred to the above-mentioned descriptions, which will not be repeated here.

[0487] This application provides a terminal device, which includes a processor and a memory; the memory stores computer execution instructions; the processor executes the computer execution instructions stored in the memory, causing the terminal device to perform the above-described method.

[0488] This application provides a chip. The chip includes a processor, which is used to call a computer program in memory to execute the technical solutions in the above embodiments. Its implementation principle and technical effects are similar to those in the related embodiments described above, and will not be repeated here.

[0489] This application also provides a computer-readable storage medium. The computer-readable storage medium stores a computer program. When the computer program is executed by a processor, it implements the methods described above. The methods described in the above embodiments can be implemented wholly or partially by software, hardware, firmware, or any combination thereof. If implemented in software, the functionality can be stored as one or more instructions or code on or transmitted over the computer-readable medium. The computer-readable medium can include computer storage media and communication media, and can also include any medium that can transfer a computer program from one place to another. The storage medium can be any target medium accessible by a computer.

[0490] In one possible implementation, a computer-readable medium may include RAM, ROM, compact disc read-only memory (CD-ROM) or other optical disc storage, disk storage or other magnetic storage devices, or any other medium targeted to carry or to store the required program code in the form of instructions or data structures, and accessible by a computer. Furthermore, any connection is appropriately referred to as a computer-readable medium. For example, if software is transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave, then coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. As used herein, disks and optical discs include laser discs, Digital Versatile Discs (DVDs), floppy disks, and Blu-ray discs, where disks typically reproduce data magnetically, while optical discs optically reproduce data using lasers. Combinations of the above should also be included within the scope of computer-readable media.

[0491] This application provides a computer program product, which includes a computer program that, when run, causes a computer to perform the above-described method.

[0492] This application describes embodiments of methods, apparatus (systems), and computer program products according to embodiments of this application with reference to flowchart illustrations and / or block diagrams. It should be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processing unit of a general-purpose computer, special-purpose computer, embedded processor, or other programmable device to produce a machine, such that the instructions, which execute via the processing unit of the computer or other programmable data processing device, generate instructions for implementing the flowchart illustrations. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0493] The above detailed embodiments further illustrate the purpose, technical solution, and beneficial effects of the embodiments of this application. It should be understood that the above are merely specific embodiments of the embodiments of this application and are not intended to limit the protection scope of the embodiments of this application. Any modifications, equivalent substitutions, improvements, etc., made on the basis of the technical solutions of the embodiments of this application should be included within the protection scope of the embodiments of this application.

Claims

1. An access method, characterized in that, The method includes: Receive the first signal from the satellite; Initiate a first access attempt, wherein the first access attempt uses a first delay and a first frequency shift for uplink time-frequency pre-compensation, wherein the first delay and the first frequency shift are determined based on the first signal and / or multiple historical location information of the terminal device; The method further includes: If the first access attempt fails, a second access attempt is initiated. The second access attempt uses the delay and frequency shift of a common location reference point (CRP) to perform time-frequency pre-compensation for the uplink. The CRP is selected from a plurality of common location reference points of the satellite.

2. The method according to claim 1, characterized in that, The public location reference point used in the second access attempt is selected from the plurality of public location reference points in a reference point selection order, which indicates the order in which the distance between the public location reference point and the terminal device increases from smallest to largest.

3. The method according to claim 2, characterized in that, The first signal includes reference point information of multiple common location reference points within the beam range of the satellite; the reference point information is used to determine the selection order of the reference points.

4. The method according to claim 3, characterized in that, The first delay and the first frequency shift are the transmission delay and frequency shift between the terminal device and the satellite at the first moment; The order of reference point selection is determined based on the first time delay, the first frequency shift, and the second time delay and second frequency shift of each of the plurality of common location reference points at the first time.

5. The method according to claim 4, characterized in that, The order of reference point selection is determined as follows: Calculate the distances between the first coordinate point and the second coordinate point of each of the plurality of common position reference points in a coordinate system established by time delay and frequency shift; the first coordinate point of the common position reference point is determined based on the second time delay and the second frequency shift of the common position reference point; the second coordinate point is determined based on the first time delay and the first frequency shift. The plurality of common location reference points are sorted according to the distance to obtain a first sequence, which is used to indicate the selection order of the reference points.

6. The method according to claim 5, characterized in that, The plurality of common location reference points includes I common location reference points, and the first coordinate point of the i-th common location reference point is: The second coordinate point is ; The distance between the first coordinate point and the second coordinate point is the Euclidean distance between the first coordinate point and the second coordinate point; Where I is a positive integer, and i is the index of the common location reference point. Let be the time delay axis coordinate value of the i-th common position reference point in the coordinate system. Let be the frequency shift axis coordinate value of the i-th common position reference point in the coordinate system. It is obtained by normalizing the second time delay of the i-th common location reference point. It is obtained by normalizing the second frequency shift of the i-th common position reference point; The first time delay is represented by the time delay axis coordinate value in the coordinate system. The first frequency shift is represented by the frequency shift axis coordinate value in the coordinate system. It is obtained by normalizing the first delay. It is obtained by normalizing the first frequency shift.

7. The method according to claim 4, characterized in that, The reference point information includes a reference time and the time delay data and frequency shift data of each of the plurality of common location reference points at the reference time; The second time delay and the second frequency shift of the i-th common location reference point among the plurality of common location reference points at the first time are determined based on the time delay data and the frequency shift data of the i-th common location reference point and the first time. Where i is the sequence number of the common location reference point, the second time delay and the second frequency shift of the i-th common location reference point at the first time are positively correlated with the first duration from the reference time to the first time, and positively correlated with the time delay data and the frequency shift data of the i-th common location reference point.

8. The method according to claim 7, characterized in that, The time delay data includes a first time advance (TA), the drift rate of the first TA, and the drift acceleration of the first TA; the frequency shift data includes a third frequency shift, the drift rate of the third frequency shift, and the drift acceleration of the third frequency shift. The i-th common location reference point at the first time T d1 The second delay Satisfying the formula: The i-th common location reference point at the first time T d1 The second frequency shift Satisfying the formula: in, The reference time is... For the i-th common location reference point in The first TA at that moment, For the i-th common location reference point in The drift rate of the first TA at time t. For the i-th common location reference point in The drift acceleration of the first TA at time t. For the i-th common location reference point in The third frequency shift at time, For the i-th common location reference point in The drift rate of the third frequency shift at time t. For the i-th common location reference point in The drift acceleration of the third frequency shift at time t.

9. The method according to claim 2, characterized in that, The step of initiating a second access attempt if the first access attempt fails includes: If the first access attempt fails, a second access attempt is initiated for the first time. The first initiated second access attempt uses the delay and frequency shift of the first reference point to perform time-frequency pre-compensation for the uplink. If the first attempt to access the second access fails, a second attempt to access the second access is initiated again. The second attempt to access the second access uses the delay and frequency shift of the second reference point to perform time-frequency pre-compensation for the uplink. The first reference point and the second reference point are selected sequentially from the plurality of common location reference points according to the reference point selection order, and the distance between the first reference point and the terminal device is less than the distance between the second reference point and the terminal device.

10. The method according to claim 9, characterized in that, The step of initiating a second access attempt if the first access attempt fails also includes: If the second access attempt fails again, the second access attempt is initiated again, and the second access attempt is initiated again to perform time-frequency pre-compensation of the uplink using the delay and frequency shift of the third reference point; The first reference point, the second reference point, and the third reference point are selected sequentially from the plurality of common location reference points in the order of reference point selection, and the distance between the second reference point and the terminal device is less than the distance between the third reference point and the terminal device.

11. The method according to any one of claims 1-10, characterized in that, The multiple historical location information corresponds to multiple historical moments; the first delay and the first frequency shift are the transmission delay and frequency shift between the terminal device and the satellite at the first moment; The first time delay and the first frequency shift are determined in the following manner: Based on the first signal, the third time delay and the fourth frequency shift are determined; Based on the aforementioned historical location information, the fourth time delay and the fifth frequency shift corresponding to the first moment are determined; Determine whether the reference signal received power (RSRP) of the first signal is less than a first threshold, and determine whether the second duration from the latest historical moment to the first moment among the plurality of historical moments is less than a second threshold; If the RSRP is less than the first threshold and the second duration is less than the second threshold, the first delay is determined to be the fourth delay and the first frequency shift is determined to be the fifth frequency shift. If the RSRP is greater than or equal to the first threshold, and / or the second duration is greater than or equal to the second threshold, the first delay is determined to be the third delay, and the first frequency shift is determined to be the fourth frequency shift.

12. The method according to claim 11, characterized in that, The first moment is the moment when the first signal is received, or the first moment is the moment when the first signal is received, or the first moment is later than the moment when the first signal is received.

13. The method according to claim 11, characterized in that, The first signal includes the synchronization signal block (SSB) signal; The method based on the first signal, the third time delay, and the fourth frequency shift includes: Based on the SSB signal, the transmission time and reception time of the SSB signal are determined, and the third delay is the difference between the reception time and the transmission time; The fourth frequency shift is determined based on the received primary synchronization signal (PSS) and the transmitted PSS determined by the SSB signal.

14. The method according to claim 13, characterized in that, The transmission time of the SSB signal is determined in the following way: The SSB signal is demodulated to obtain the system frame number, half-frame index and half-frame offset carried by the main information block; The system information block type 1 is received on the time-frequency resource of the system information block type 1 indicated by the main information block, and the system information block type 1 is obtained; The system information block type 19 is received on the time-frequency resources of the system information block type 19 indicated by the system information block type 1, and the timing reference carried by the system information block type 19 is obtained. ; The transmission time is determined based on the timing reference, the system frame number, the half-frame index, and the half-frame offset. The transmission time is positively correlated with the timing reference, the system frame number, the half-frame index, and the half-frame offset.

15. The method according to claim 14, characterized in that, The launch time Satisfying the formula: in, The system frame number corresponds to the start time of the wireless frame. , The duration of the wireless frame. This refers to the system frame number.

16. The method according to claim 13, characterized in that, The transmission time of the SSB signal is determined in the following way: The SSB signal is demodulated to obtain the system frame number, half-frame index and half-frame offset carried by the main information block; The system information block type 1 is received on the time-frequency resource of the system information block type 1 indicated by the main information block, and the system information block type 1 is obtained; The system information block type 9 is received on the time-frequency resource of the system information block type 9 indicated by system information block type 1, and the world standard time carried by the system information block type 9 is obtained. The system frame number (SFN) of the first radio frame after the end of the system information block type 9 transmission window. next ; based on SFN next The system frame number, the half-frame index, and the half-frame offset determine the transmission time, and the transmission time is related to the system frame number, the half-frame index, and the half-frame offset. The system frame number, the half-frame index, and the half-frame offset are all positively correlated.

17. The method according to claim 16, characterized in that, The launch time Satisfying the formula: in, The system frame number corresponds to the start time of the wireless frame. , The duration of the wireless frame. This refers to the system frame number.

18. The method according to claim 13, characterized in that, The reception time of the SSB signal is determined in the following way: A sliding window cross-correlation operation is performed on the received PSS extracted from the SSB signal and the pre-stored local PSS sequence to obtain the cross-correlation peak h0; Based on the cross-correlation peak h0 and the sampling period of the baseband signal Determine the time delay offset The time delay offset With the cross-correlation peak h0 and sampling period Positive correlation; Determine the receiving time t rx The start time t of the sliding window start With the time delay offset sum.

19. The method according to claim 13, characterized in that, The fourth frequency shift is determined based on the received PSS and the transmitted PSS in the following manner: The received PSS signal With the transmitted PSS signal Conjugate multiplication yields ; The The correlation calculation is performed in two parts to obtain the correlation value R. PSS ; From the relevant value R PSS Extracting the fractional octave frequency offset ; Using the fractional frequency offset For the received PSS signal Perform fractional frequency offset compensation to obtain the compensation result. ; The compensation result Transform to the frequency domain to obtain and the transmitted PSS signal Transform to the frequency domain to obtain Detect the With the The maximum value of the relevant peak is used to determine the frequency offset corresponding to the maximum value of the relevant peak as an integer part of the frequency offset. ; Based on the fractional frequency offset The frequency offset of the integer part The fourth frequency shift is determined based on the preset subcarrier spacing, and the fourth frequency shift is positively correlated with the subcarrier spacing and with the fractional frequency offset. and the frequency offset of the integer part Positive correlation.

20. The method according to claim 19, characterized in that, The fourth frequency shift Satisfying the formula: in, The subcarrier spacing is defined as follows.

21. The method according to claim 11, characterized in that, The first signal includes the ephemeris information of the satellite; The step of determining the fourth time delay and fifth frequency shift corresponding to the first time moment based on the multiple historical location information includes: The multiple historical location information is preprocessed to obtain preprocessed historical location information; The preprocessed historical location information is input into a pre-trained first model, and the first model outputs the location data at the first moment. Based on the location data at the first moment and the ephemeris information, the fourth time delay and the fifth frequency shift are determined.

22. The method according to claim 1, characterized in that, The method further includes: The access attempt is terminated when the most recent access attempt fails and the number of access attempts reaches the third threshold.

23. An access method, characterized in that, The method includes: A first signal is sent to enable the terminal device to initiate an access attempt. The time delay and frequency shift of the uplink time-frequency pre-compensation for the access attempt are determined based on the first signal and / or multiple historical location information of the terminal device. The first signal includes reference point information of multiple common location reference points within the beam range of the satellite; the reference point information is used to determine the reference point selection order, and the time and frequency shift of the uplink time-frequency pre-compensation for the access attempt are the time and frequency shift of the common location reference point selected from the multiple common location reference points according to the reference point selection order.

24. A communication system, characterized in that, The communication system includes: a satellite and a terminal device; the terminal device is used to perform the method as described in any one of claims 1-22, and the satellite is used to perform the method as described in claim 23.

25. A terminal device, characterized in that, include: Processor and memory; The memory stores computer-executed instructions; The processor executes computer execution instructions stored in the memory, causing the terminal device to perform the method as described in any one of claims 1-22.

26. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by a processor, it implements the method as described in any one of claims 1-23.

27. A chip system, characterized in that, It includes at least one processor and a communication interface, the communication interface and the at least one processor being interconnected via a line, the at least one processor being configured to run a computer program or instructions to perform the method as described in any one of claims 1-23.

28. A computer program product, characterized in that, Includes a computer program that, when run, causes a computer to perform the method as described in any one of claims 1-23.

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