Satellite ephemeris epoch time broadcasting method

Abstract

The invention belongs to the technical field of satellite navigation and communication, and discloses a satellite ephemeris epoch time broadcasting method, and the broadcasting method specifically comprises the following steps: S1, calculating the number of SFNs required by a satellite ephemeris; s3, calculating an expansion bit length; S4, selecting an expansion strategy and determining a final expansion bit number; S5, combining the expansion bit and an original time field; s6, calculating the minimum effective time of the epoch time; and S7, determining the final epoch time by the base station. According to the method, the time range of the epochs is scientifically and reasonably determined according to the maximum value of the effective duration of the ephemeris, and the problem of time blurring under long-time epochs is effectively solved. Afterwards, the expanded ephemeris epoch time range is accurately transmitted to the terminal by using an air interface broadcast technology, so that the timeliness and accuracy of information are ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field of satellite navigation and communication, and specifically relates to a method for broadcasting the epoch time of satellite ephemeris. Background Art

[0002] The method for broadcasting the epoch time of satellite ephemeris refers to a technical means of sending the epoch time (i.e., the starting time of the valid time of ephemeris) information of satellite ephemeris to terminal users through a wireless communication network. This method aims to ensure that terminal users can accurately receive and interpret satellite ephemeris data, so as to accurately estimate the position and speed of satellites. In the prior art, the SFN and subFrame ranges of epochTime are limited, resulting in the problem of ambiguous ephemeris epoch time when the valid time exceeds 10 seconds, and it is difficult for the terminal to determine the exact position of the epoch time. At the same time, the ephemeris update cycle is inconsistent with the SI broadcast cycle, which also poses a challenge for the terminal to obtain the accurate ephemeris effective time. To solve this problem, a new method for determining the epoch time is needed. This method should be able to accurately calculate and broadcast the ephemeris epoch time in the SI message to ensure that the terminal can obtain the accurate starting time of ephemeris effectiveness. This method needs to consider the differences between the ephemeris update cycle and the SI broadcast cycle, as well as the limited range of epochTime, and through reasonable algorithms and parameter settings, achieve the accurate determination and broadcast of the ephemeris epoch time, thereby improving network performance and user experience. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for broadcasting the epoch time of satellite ephemeris to solve the problems raised in the above background art.

[0004] To achieve the above purpose, the present invention provides the following technical solution: A method for broadcasting the epoch time of satellite ephemeris, and the specific usage steps of this broadcasting method are as follows:

[0005] S1: Calculate the number of SFNs required for satellite ephemeris: According to the maximum valid time of satellite ephemeris, calculate the required number of SFNs N = ceil;

[0006] S2: Determine whether the epoch time needs to be extended: If N > 1024, the epoch time needs to be extended to adapt to the long-cycle ephemeris, otherwise use the original format;

[0007] S3: Calculate the extended bit length (M): When extension is required, calculate the minimum number of bits M = ceil(log2(N / 1024)) to ensure that the epoch time covers the N×SFN cycle;

[0008] S4: Select an extension strategy and determine the final extended bit number: Determine the extended bit number according to the strategy: directly M, limited to 10, or fixed at 10, to balance the requirements and implementation;

[0009] S5: Combine the extended bit with the original epoch time field: Combine the extended bit with the SFN, subframe number and epochTime, and broadcast it to the terminal through the system message SI;

[0010] S6: Calculate the minimum effective time of the epoch time: The lower limit of the ephemeris time is jointly determined by the maximum value of the ephemeris and the SI period, the SI listening window, and the terminal processing delay;

[0011] S7: The base station determines the final epoch time: The base station sets epochTime ≥ epochTime_min, and aligns the SI period with the formula to ensure no configuration conflicts.

[0012] Preferably, the specific steps for using the number of SFNs (N) required for calculating the satellite ephemeris in S1 are as follows:

[0013] Step 1: Determine the maximum effective time of the satellite ephemeris

[0014] Operation: According to the update requirements of the satellite ephemeris, clarify its maximum effective time;

[0015] Example: If the ephemeris is updated every 1 hour, the maximum effective time T1 = 1 hour = 3600 seconds;

[0016] Step 2: Calculate the number of system frame numbers

[0017] Formula: N = ceil, where the SFN period is fixed at 10 ms;

[0018] Example: If T1 = 3600 seconds

[0019]

[0020] Preferably, the specific steps for determining whether to extend the epoch time in S2 are as follows:

[0021] Step 1: Judge the SFN quantity threshold: Check whether the calculated number of SFNs N is greater than 1024;

[0022] Step 2: Trigger the extension requirement: If N > 1024, it is determined that the epoch time needs to be extended to adapt to the ultra-long ephemeris period;

[0023] Step 3: Select the format strategy: If N ≤ 1024, directly use the original epoch time format without extension.

[0024] Preferably, the specific steps for calculating the extended bit length (M) in S3 are as follows:

[0025] Step 1: Calculate the extension multiple: Divide the number of SFNs N by 1024 to obtain the time multiple that needs to be extended;

[0026] Step 2: Take the logarithm and round up: Take the base-2 logarithm of the result and round up to obtain the minimum number of extended bits M.

[0027] Step 3: Verify the coverage range: Ensure that the extended epoch time can represent the total duration of N × SFN cycles.

[0028] Preferably, the specific steps for selecting the extension strategy and determining the final number of extended bits in S4 are as follows:

[0029] Step 1: Evaluate the applicability of the strategy: Select candidate strategies from Strategy 1, Strategy 2, and Strategy 3 according to system compatibility requirements and implementation complexity factors.

[0030] Step 2: Select the extension strategy:

[0031] If full adaptation to an extremely long cycle is required and compatibility permits, select Strategy 1;

[0032] If a balance between extension and compatibility is required, select Strategy 2;

[0033] If simplifying the implementation is required, select Strategy 3;

[0034] Step 3: Calculate the final number of extended bits:

[0035] Strategy 1: FinalM = M;

[0036] Strategy 2: FinalM = min(M, 10);

[0037] Strategy 3: FinalM = 10.

[0038] Preferably, the specific steps for combining the extended bits with the original epoch time field in S5 are as follows:

[0039] Step 1: Combine the extended epoch time: Concatenate the extended bits with the original SFN and subframe number in the protocol format to generate a complete epochTime field.

[0040] Step 2: Broadcast the extended epoch time: Broadcast the combined epochTime to the terminals through the system message in the scheduling period to ensure that the terminals are synchronized and updated.

[0041] Preferably, the specific steps for calculating the minimum effective time of the epoch time in S6 are as follows:

[0042] Step 1: Determine the maximum value

[0043] First, it is necessary to determine the larger value between the ephemeris update period T1 and the system message broadcast period T2;

[0044] It is expressed by the mathematical formula: max period = max(T1, T2);

[0045] Step 2: Calculate the base time

[0046] Next, add the max_period obtained in Step 1 to the SI window time and the terminal processing delay to obtain the base time;

[0047] It is expressed by the mathematical formula as:

[0048] base_time = max_period + SI window time + terminal processing delay;

[0049] Step 3: Obtain the final result

[0050] Finally, use the base_time calculated in Step 2 as the value of epochTime_min.

[0051] It is expressed by the mathematical formula as:

[0052] epochTime_min = base_time.

[0053] Preferably, the specific steps for the base station in S7 to determine the final epoch time (epochTime) are as follows:

[0054] Step 1: Determine epochTime_min and SI period T2;

[0055] Step 2: Use the formula to calculate epochTime: epochTime = ceil(epochTime_min / T2)*T2;

[0056] Step 3: Verify that epochTime is an integer multiple of T2;

[0057] Step 4: Ensure that the effective moment of epochTime is later than the SI reception moment to avoid conflicts.

[0058] The beneficial effects of the present invention are as follows:

[0059] The present invention scientifically and reasonably determines the epoch time range based on the maximum value of the valid duration of the ephemeris, effectively solving the problem of time ambiguity in long epochs. Subsequently, using the air interface broadcast technology, the extended ephemeris epoch time range is accurately transmitted to the terminal, ensuring the timeliness and accuracy of the information. During this process, special attention is paid to the adaptation problem between the ephemeris update cycle and the system information (SI) broadcast cycle. Through refined parameter adjustment and algorithm optimization, seamless docking between the two is achieved, avoiding configuration conflicts and time errors caused by inconsistent cycles. This innovative method not only improves the terminal's ability to accurately receive and interpret the ephemeris epoch time but also significantly improves the accuracy of estimating the satellite position and speed, providing a more solid and reliable time reference for positioning and navigation services and effectively enhancing the user experience and the overall system performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 It is a schematic diagram of the overall process of the present invention;

[0061] Figure 2 It is a schematic diagram of the number of bits of the present invention;

[0062] Figure 3 It is a schematic diagram of the relationship between EpochTime of the present invention, the ephemeris cycle, and the SI transmission cycle. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0063] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0064] As Figures 1 to 3 shown, the embodiments of the present invention provide a method for broadcasting the ephemeris epoch time of a satellite. The specific usage steps of this broadcasting method are as follows:

[0065] S1: Calculate the number of SFNs (N) required for the satellite ephemeris: According to the maximum valid time of the satellite ephemeris, calculate the required number of SFNs N = ceil(maximum valid time / 10 ms).

[0066] S2: Determine whether the epoch time needs to be extended: If N > 1024, the epoch time needs to be extended to adapt to the long-cycle ephemeris, otherwise use the original format;

[0067] S3: Calculate the extended bit length (M): When extension is required, calculate the minimum number of bits M = ceil(log2(N / 1024)) to ensure that the epoch time covers the N × SFN cycle;

[0068] S4: Select an extension strategy and determine the final number of extension bits: Determine the number of extension bits according to the strategy: direct M, limit 10, or fixed 10, balancing requirements and implementation;

[0069] S5: Combine the extension bits with the original epoch time field: Combine the extension bits with the SFN and subframe number to form epochTime, and broadcast it to the terminal through the system message SI;

[0070] S6: Calculate the minimum effective time of the epoch time (epochTime_min): The lower limit of the ephemeris time is jointly determined by the maximum value of the ephemeris and SI period, the SI listening window, and the terminal processing delay;

[0071] S7: The base station determines the final epoch time (epochTime): The base station sets epochTime ≥ epochTime_min and aligns the SI period using a formula to ensure no configuration conflicts.

[0072] This method for broadcasting the satellite ephemeris epoch time realizes the efficient and accurate broadcasting of the epoch time by precisely calculating the number of SFNs, intelligently judging the extension requirements, flexibly calculating the length of the extension bits, and scientifically combining the extension bits with the original epoch time field. At the same time, this method also considers the minimum effective time of the epoch time, ensuring the timely update of the ephemeris information and the synchronous reception of the terminal. Finally, the base station avoids configuration conflicts by precisely setting the epoch time, improving the stability and reliability of the system. This method not only optimizes the time management of the satellite navigation system but also provides more accurate and efficient positioning services for end-users.

[0073] Among them, the specific steps for using the calculation of the number of SFNs (N) required for the satellite ephemeris in S1 are as follows:

[0074] Step 1: Determine the maximum effective time of the satellite ephemeris

[0075] Operation: According to the update requirements of the satellite ephemeris, clarify its maximum effective time (such as the ephemeris update period T1);

[0076] Example: If the ephemeris is updated every 1 hour, then the maximum effective time T1 = 1 hour = 3600 seconds.

[0077] Step 2: Calculate the number of system frame numbers (SFNs) (N)

[0078] Formula: N = ceil(SFN period / maximum effective time), where the SFN period is fixed at 10 ms;

[0079] Example: If T1 = 3600 seconds

[0080]

[0081] The method for calculating the number of SFNs required for satellite ephemeris provides an accurate time management basis for satellite navigation systems. By determining the maximum effective time of satellite ephemeris and combining it with the period of the system frame number, the system can accurately calculate the required number of SFNs. This step not only ensures the timely update of ephemeris data but also avoids navigation errors caused by improper time management. At the same time, using a fixed SFN period for calculation improves the standardization and automation of time management. In summary, this method provides strong guarantee for the stable operation and precise positioning of satellite navigation systems, contributing to the improvement of overall navigation performance and service quality.

[0082] Among them, the specific steps for determining whether to extend the epoch time in S2 are as follows:

[0083] Step 1: Determine the SFN quantity threshold: Check whether the calculated number of SFNs N is greater than 1024.

[0084] Step 2: Trigger the extension requirement: If N > 1024, it is determined that the epoch time needs to be extended to adapt to the ultra-long ephemeris period.

[0085] Step 3: Select the format strategy: If N ≤ 1024, directly use the original epoch time format without extension.

[0086] The specific steps for determining whether to extend the epoch time provide an efficient and accurate time management strategy for satellite navigation systems. By determining the SFN quantity threshold, the system can automatically identify whether the epoch time needs to be extended to adapt to the ultra-long ephemeris period. When the number of SFNs exceeds 1024, the system immediately triggers the extension requirement to ensure that the epoch time can fully cover the required time range. Conversely, if the number of SFNs is within the threshold, the original epoch time format is directly used without additional extension, thus simplifying the system complexity. This method not only improves the flexibility of time management but also effectively avoids unnecessary resource consumption, providing strong support for the stable operation and efficient positioning of satellite navigation systems.

[0087] Among them, the specific steps for calculating the extended bit length (M) in S3 are as follows:

[0088] Step 1: Calculate the extension multiple: Divide the number of SFNs N by 1024 to obtain the time multiple that needs to be extended.

[0089] Step 2: Take the logarithm and round up: Take the logarithm base 2 of the result and round up to obtain the minimum number of extended bits M.

[0090] Step 3: Verify the coverage range: Ensure that the extended epoch time can represent the total duration of N × SFN period.

[0091] The specific steps for calculating the extended bit length (M) provide a scientific and rigorous method for the extension of the epoch time in the satellite navigation system. By calculating the extension multiple and taking the integer part of the logarithm, the system can accurately obtain the minimum number of extended bits required, thus ensuring that the epoch time can fully cover the required time range. This method not only improves the flexibility of the epoch time expression but also enhances the system's adaptability to ultra-long cycles. At the same time, the step of verifying the coverage range ensures that the extended epoch time can accurately represent the total duration required, avoiding errors caused by insufficient time range. In summary, this method for calculating the extended bit length provides a strong guarantee for the stable operation and precise positioning of the satellite navigation system.

[0092] Among them, the specific usage steps for selecting the extension strategy and determining the final extended bit number in S4 are as follows:

[0093] Step 1: Evaluate the strategy applicability: Select candidate strategies from Strategy 1 (directly extend M), Strategy 2 (limit to 10 bits), and Strategy 3 (fixed 10 bits) according to factors such as system compatibility requirements and implementation complexity;

[0094] Step 2: Select the extension strategy:

[0095] If full adaptation to ultra-long cycles is required and compatibility permits, select Strategy 1;

[0096] If a balance between extension and compatibility is required, select Strategy 2;

[0097] If simplifying the implementation is required, select Strategy 3;

[0098] Step 3: Calculate the final extended bit number:

[0099] Strategy 1: FinalM = M;

[0100] Strategy 2: FinalM = min(M, 10);

[0101] Strategy 3: FinalM = 10.

[0102] The specific steps for selecting the extension strategy and determining the final extended bit number provide a flexible and efficient solution for the extension of the epoch time in the satellite navigation system. By evaluating the applicability of different strategies, the system can select the most suitable extension strategy according to actual needs and compatibility requirements. Strategy 1 is applicable to cases where full adaptation to ultra-long cycles is required, Strategy 2 balances extension and compatibility, and Strategy 3 simplifies the implementation process. Finally, the extended bit number calculated according to the selected strategy ensures the integrity and accuracy of the epoch time information. This method not only improves the flexibility and adaptability of the system but also optimizes the expression of the epoch time, providing strong support for the stable operation of the satellite navigation system and the precise positioning of end-users.

[0103] Among them, the specific usage steps of combining the extended bit with the original epoch time field in S5 are as follows:

[0104] Step 1: Combine the extended epoch time: Concatenate the extended bit (FinalM or fixed 10-bit) with the original SFN and subframe number according to the protocol format to generate a complete epochTime field;

[0105] Step 2: Broadcast the extended epoch time: Broadcast the combined epochTime to the terminal through the system information (SI) according to the scheduling period to ensure that the terminal synchronously updates.

[0106] The method of combining the extended bit with the original epoch time field and broadcasting it provides a more flexible and efficient time management means for the satellite navigation system. By combining the extended epoch time, the system can more accurately express the complete information of the epoch time, avoiding ambiguity problems caused by time range limitations. At the same time, broadcasting the combined epochTime to the terminal through the system information regularly ensures that the terminal can synchronously update the epoch time information, thereby maintaining precise synchronization with the satellite system. This method not only improves the accuracy and integrity of the time information, but also effectively enhances the stability and reliability of the satellite navigation system, providing more accurate positioning and navigation services for end users.

[0107] Among them, the specific usage steps of calculating the minimum effective time (epochTime_min) of the epoch time in S6 are as follows:

[0108] Step 1: Determine the maximum value

[0109] First, it is necessary to determine the larger value between the ephemeris update period T1 and the system information (SI) broadcast period T2;

[0110] Expressed by a mathematical formula: max period = max(T1, T2)

[0111] This step is the basis for calculating epochTime_min, because it ensures that regardless of the specific values of T1 and T2, the larger one of them will be taken as the starting point, thus ensuring the sufficiency of time.

[0112] Step 2: Calculate the base time

[0113] Next, add the max_period obtained in Step 1 to the SI window time and the terminal processing delay to obtain the base time;

[0114] Expressed by a mathematical formula:

[0115] base_time = max_period + SI window time + terminal processing delay;

[0116] This step is to integrate all time-related parameters together to form a basic time value, preparing for the final calculation of epochTime_min.

[0117] Step 3: Obtain the final result

[0118] Finally, use the base_time calculated in Step 2 as the value of epochTime_min.

[0119] It is expressed by a mathematical formula as:

[0120] epochTime_min = base_time.

[0121] This step is the one to obtain the final result, which directly gives the specific value of epochTime_min. This value is the minimum time that the terminal needs to wait before configuring the MAC layer.

[0122] The method for calculating the minimum effective time of the epoch time (epochTime_min) ensures the sufficiency and accuracy of time through scientific and rigorous steps. First, by determining the larger value between the ephemeris update period and the system message broadcast period, a solid foundation is laid for the calculation of the epoch time. Subsequently, adding this larger value to the SI window time and the terminal processing delay to obtain the base time, fully considering all time-related factors. Finally, directly using the base time as the value of epochTime_min provides a clear minimum waiting time for the terminal before configuring the MAC layer. This method not only improves the accuracy of time calculation but also effectively avoids configuration conflicts and errors caused by insufficient time, providing a strong guarantee for the stable operation of the satellite navigation system.

[0123] Among them, the specific steps for the base station in S7 to determine the final epoch time (epochTime) are as follows:

[0124] Step 1: Determine epochTime_min and the SI period T2;

[0125] Step 2: Use the formula to calculate epochTime: epochTime = ceil(epochTime_min / T2)*T2;

[0126] Step 3: Verify that epochTime is an integer multiple of T2;

[0127] Step 4: Ensure that the effective moment of epochTime is later than the SI reception moment to avoid conflicts.

[0128] In S7, the steps for the base station to determine the final epoch time ensure the efficiency and stability of network configuration. First, by precisely calculating epochTime_min and considering the SI period T2, the base station can set an epochTime that not only meets the minimum time requirement but also aligns with the system message broadcast period. Second, verifying that the epochTime is an integer multiple of T2 avoids time fragmentation and configuration complexity. Finally, ensuring that the effective moment of epochTime is later than the SI reception moment effectively prevents configuration conflicts and improves the reliability and security of network operation. This series of steps is crucial for optimizing network performance and user experience.

[0129] Embodiment 1: According to expansion strategy 3, directly expand the epoch time by 10 bits. A possible broadcast message is as follows:

[0130]

[0131] Introduce a 10-bit superframe number, then the epochtime range is expanded to 10240 s, which is greater than the maximum valid time s900. Therefore, the ephemeris epoch time can be uniquely identified.

[0132] Embodiment 2: According to expansion strategy 1, calculate N = 900000 ms / 10 ms, calculate M = ceil(log2(N / 1024)), obtain M = 7 bits. A possible broadcast message is as follows:

[0133]

[0134] ul-SyncValidityDuration-r17 ENUMERATED{s5,s10,s15,s20,s25,s30,s35,s40,s45,s50,s55,s60,s120,s180,s240,s900}

[0135] Embodiment 3: Determine the epcoTime. Assume that the latest ephemeris update time is SFN100, subframe 0, the ephemeris update period is 2 s, the SI period is 640 ms, the SI window is 160 ms, and the time required for the terminal to unpack the ephemeris and configure the ephemeris to take effect in the MAC is 6 ms. Then, the minimum time of epochTime = max(ephemeris update period T1, SI period T2) + SI window + time required for the terminal to unpack the ephemeris and configure the ephemeris to take effect in the MAC = max(2 s, 640 ms) + 160 ms + 6 ms = 2166 ms. The smallest integer multiple of the SI period greater than 2166 ms is 2560 ms. Therefore, the epochtime of the ephemeris at this moment is SFN100 - 0 + 2560 ms = SFN356 subframe 0.

[0136] It should be noted that, in this document, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variation thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device.

[0137] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for broadcasting satellite ephemeris epoch time, characterized in that: The specific steps of using this broadcast method are as follows: S1: Calculate the number of SFNs required for satellite ephemeris: Calculate the number of SFNs required N=ceil according to the maximum valid time of satellite ephemeris; S2: Determine whether the epoch time needs to be extended: if N>1024, the epoch time needs to be extended to adapt to the long-period ephemeris, otherwise the original format is used; S3: Calculate the extended bit length: When extension is required, calculate the minimum number of bits M = ceil(log2(N / 1024)) to ensure that the epoch time covers N×SFN cycles; S4: Select an expansion strategy and determine the final number of expansion bits: Determine the number of expansion bits according to the strategy: direct M, limited to 10, or fixed to 10, balancing demand and implementation; S5: Combine the extension bit with the original epoch time field: Combine the extension bit with the SFN and subframe number to form epochTime, which is broadcast to the terminal through the system message SI; S6: Calculate the minimum effective time of the epoch time: the lower limit of the ephemeris time is determined by the maximum value of the ephemeris and SI cycles, the SI listening window and the terminal processing delay; S7: The base station determines the final epoch time: The base station sets epochTime ≥ epochTime_min and uses the formula to align the SI period to ensure that there is no configuration conflict.

2. A method for broadcasting satellite ephemeris epoch time according to claim 1, characterized in that: The specific steps for calculating the number of SFNs required for satellite ephemeris in S1 are as follows: Step 1: Determine the maximum valid time of the satellite ephemeris Operation: According to the update requirements of satellite ephemeris, its maximum effective time shall be clarified; Example: If the ephemeris is updated every hour, the maximum valid time T1 = 1 hour = 3600 seconds; Step 2: Calculate the number of system frame numbers Formula: N = ceil, where the SFN period is fixed at 10ms; Example: If T1 = 3600 seconds 3. The method for broadcasting satellite ephemeris epoch time according to claim 1, characterized in that: The specific steps for determining whether the epoch time needs to be extended in S2 are as follows: Step 1: Determine the SFN number threshold: Check whether the calculated SFN number N is greater than 1024; Step 2: Triggering the expansion requirement: If N>1024, it is determined that the epoch time needs to be expanded to adapt to the ultra-long ephemeris cycle; Step 3: Select the format strategy: If N ≤ 1024, use the original epoch time format directly without expansion.

4. The method for broadcasting satellite ephemeris epoch time according to claim 1, characterized in that: The specific steps for calculating the extended bit length in S3 are as follows: Step 1: Calculate the expansion multiple: Divide the number of SFNs N by 1024 to get the time multiple to be expanded; Step 2: Calculate the logarithm and round it up: Take the logarithm with base 2 of the result and round it up to get the minimum number of extended bits M; Step 3: Verify coverage: Ensure that the extended epoch time can represent the total duration of N × SFN cycles.

5. The method for broadcasting satellite ephemeris epoch time according to claim 1, characterized in that: The specific steps of selecting the extension strategy and determining the final extension bit number in S4 are as follows: Step 1: Evaluate strategy applicability: Select candidate strategies from strategy 1, strategy 2, and strategy 3 based on system compatibility requirements and implementation complexity factors; Step 2: Select an expansion strategy: If you need to fully adapt to an extremely long period and compatibility allows, choose strategy 1; If you need to balance expansion and compatibility, choose strategy 2; If you need to simplify the implementation, choose strategy 3; Step 3: Calculate the final number of extended bits: Strategy 1: FinalM=M; Strategy 2: FinalM = min(M, 10); Strategy three: FinalM=10.

6. The method for broadcasting satellite ephemeris epoch time according to claim 1, characterized in that: The specific steps of using the combined extension bit and the original epoch time field in S5 are as follows: Step 1: Combine the extended epoch time: concatenate the extended bits with the original SFN and subframe number according to the protocol format to generate a complete epochTime field; Step 2: Broadcast the extended epoch time: Broadcast the combined epochTime to the terminal through system messages according to the scheduling period to ensure that the terminal is updated synchronously.

7. The method for broadcasting satellite ephemeris epoch time according to claim 1, characterized in that: The specific steps for calculating the minimum effective time of the epoch time in S6 are as follows: Step 1: Determine the maximum value First, it is necessary to determine the larger value of the ephemeris update period T1 and the system message broadcast period T2; Mathematically expressed as: max period = max(T1, T2); Step 2: Calculate base time Next, add the max_period obtained in step 1 to the SI window time and the terminal processing delay to get the base time; The mathematical expression is: base_time = max_period + SI window time + terminal processing delay; Step 3: Get the final result Finally, use the base_time calculated in step 2 as the value of epochTime_min. The mathematical expression is: epochTime_min=base_time.

8. The method for broadcasting satellite ephemeris epoch time according to claim 1, characterized in that: The specific steps for the base station to determine the final epoch time in S7 are as follows: Step 1: Determine epochTime_min and SI period T2; Step 2: Calculate epochTime using the formula: epochTime = ceil (epochTime_min / T2) * T2; Step 3: Verify that epochTime is an integer multiple of T2; Step 4: Ensure that epochTime takes effect later than SI reception time to avoid conflicts.

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