Method and device for supporting lag indication of timing advance command in NTN satellite communication

Abstract

The application discloses a method and device for supporting lag indication of timing advance command in NTN satellite communication, and belongs to the technical field of communication. The method is to expand the RAR timing advance command field to support simultaneous indication of timing advance and timing lag (negative adjustment). The core idea is to introduce a symbol bit (or expand the coding space) in the timing advance command field of the RAR MAC PDU, so that the timing advance command field can represent both positive numbers (timing advance) and negative numbers (timing lag / negative adjustment), thereby allowing the network to indicate the UE to appropriately lag the uplink transmission time through the RAR when detecting that the UE uplink timing is earlier than the ideal time (overcompensation, early transmission), and correcting the overcompensation problem caused by the ephemeris error.

Description

Technical Field

[0001] This invention relates to the field of communication technology, and in particular to a method and device for supporting lag indication in timing advance commands in NTN satellite communication. Background Technology

[0002] Non-Terrestrial Networks (NTNs) are satellite communication technologies introduced by 3GPP in Release 17. They aim to extend the 5G NR air interface protocol to non-terrestrial communication scenarios such as satellites and High Altitude Platforms (HAPS), achieving integrated space-ground communication. NTNs can provide communication coverage in terrestrial network blind spots such as oceans, deserts, and aviation, and are an important component of the 5G Advanced and future 6G network architectures. 3GPP has defined a complete frequency band system for NTNs, covering the FR1 Sub-6GHz band (n255, n256, etc.) and the FR2 millimeter-wave band (n510, n511, etc.), supporting both transparent forwarding and regenerative forwarding architectures. Compared to terrestrial 5G cellular systems, NTN faces key challenges including: ultra-long propagation latency (LEO satellite one-way latency of 4~12ms, while GEO can reach over 270ms), Doppler shift (LEO @2GHz can reach ±50kHz, far higher than terrestrial 5G's ±0.1kHz), rapid mobility (LEO needs to switch every 3~10 minutes), and ephemeris errors.

[0003] Timing Advance (TA) is a core technology for ensuring uplink synchronization in cellular communication systems. In terrestrial 5G NR systems, User Equipment (UE) estimates the timing offset based on the received downlink synchronization signal. The base station informs the UE of the required timing advance through the TA command in the Random Access Response (RAR). The UE then sends uplink data in advance, ensuring that the uplink signals of different UEs are aligned within the base station's receiving window.

[0004] In Release 17, 3GPP enhanced the Timing Advancement (TA) mechanism for NTN scenarios, introducing a separate timing advance architecture. This architecture achieves latency compensation through the coordinated use of three timing parameters: (1) Common TA (Common Timing Advance): gNB broadcasts the ta-Common parameter via SIB19, which represents the round-trip time delay from the Reference Point (RP) to the satellite payload; (2) UE autonomous calculation: The UE uses GNSS to obtain its own position, and combines the ephemeris data broadcast by SIB19 (ephemerisInfo, which supports two formats: state vector and Kepler orbital elements) to calculate the precise geometric distance of the service link, and converts it into UE-specific timing advance components. (3) K_offset: The configured scheduling offset, used to reserve sufficient uplink and downlink signal processing time for the UE.

[0005] In existing 5G NR MAC RAR (Random Access Response), the TA command field is 12 bits (unsigned, 0~3846), with a maximum TA of approximately 2.5ms; LTE uses 11 bits. Residual errors under NTN require bidirectional adjustment, and existing unsigned coding cannot support negative correction.

[0006] In summary, the shortcomings of existing technologies are manifested in the following aspects: Defect 1: The existing RAR TA command only supports indicating timing advance and cannot compensate for timing lag caused by overcompensation.

[0007] In NTN scenarios, after the UE autonomously calculates the timing advance based on ephemeris, satellite ephemeris errors can cause a deviation between the timing compensation calculated by the UE and the actual required compensation. When the UE overestimates the distance between the satellite and the terminal, its calculated timing advance is too large, causing the UE to actually advance the uplink transmission time too much (i.e., transmit too early). This results in the PRACH preamble or PUSCH data arriving at the satellite receiver earlier than the ideal time (i.e., overcompensation occurs, requiring timing lag correction). In existing technologies, the RAR TA command is always positive, only instructing the UE to transmit further ahead, and cannot correct the timing lag problem in this overcompensated scenario.

[0008] Defect 2: The existing 12-bit unsigned encoding of the TA command field is not suitable for the bidirectional delay adjustment requirements of NTN.

[0009] The maximum timing advance that the 12-bit TA command field (unsigned integer, value range 0~3846) of terrestrial 5G NR can cover is approximately 2.5ms. Although 3GPP R17 alleviated the NTN ultra-long latency problem through the sub-architecture of Common TA + UE-specific calculation, the TA command field in MAC RAR is unsigned and can only indicate positive timing advance, not negative timing lag (i.e., delaying UE transmission). In NTN, ephemeris errors may cause UE overcompensation (transmission too early), in which case the network needs to instruct the UE to make negative adjustments (timing lag), and the existing unsigned coding cannot meet this bidirectional adjustment requirement.

[0010] MAC RAR refers to MAC Random Access Response, which is a key message (Msg2) sent by the base station (gNB) to the terminal (UE) during the random access process. Defect 3: Ephemeris errors lead to a decrease in the success rate of NTN random access, affecting user experience and system efficiency.

[0011] The LEO satellite operates at a high speed of approximately 7.8 km / s, resulting in a time lag between the satellite ephemeris broadcast update cycle and the actual position change of the UE. Furthermore, external factors such as satellite attitude deviation and atmospheric refraction introduce additional timing estimation errors. These factors combined can cause the timing error during PRACH transmission by the UE to exceed the cyclic prefix (CP) tolerance of the satellite receiver, leading to random access failure and increased access latency and signaling overhead. Summary of the Invention

[0012] In view of the problem that timing advance commands in the prior art cannot indicate timing lag, the purpose of this invention is to provide a method and device for timing advance commands to support lag indication in NTN satellite communication, so as to at least partially solve the above-mentioned problem.

[0013] To achieve the above objectives, the technical solution of the present invention is as follows: In a first aspect, the present invention provides a method for supporting hysteresis indication in timing advance commands in NTN satellite communication, applied to network-side equipment, the method comprising the following steps: Receive uplink signals sent by user equipment; Based on the uplink signal, the timing deviation of the user equipment is estimated. The timing deviation has positive and negative polarities. When it is positive, it is used to indicate timing advance, and when it is negative, it is used to indicate timing lag. The timing deviation is mapped to a timing advance command field with a sign and a deviation value through a preset encoding rule. The sign is used to represent the polarity of the timing deviation, and the deviation value is used to represent the absolute value of the timing deviation. The timing advance command field is constructed and expanded into a timing adjustment command and sent to the user equipment. After receiving the timing adjustment command, the user equipment can parse the sign and deviation value of the timing advance command field, and perform timing advance or timing lag adjustment corresponding to the deviation value on the uplink according to the polarity of the sign.

[0014] In some preferred embodiments, when the uplink signal is a PRACH preamble, the network-side device fills the timing advance command field in the RAR MACPDU and sends it to the user equipment through a combination structure of MAC Subheader + MAC RAR. When the uplink signal is a PUSCH or SRS uplink reference signal, the network-side device sends the timing adjustment command to the user equipment via Timing AdvanceMAC CE.

[0015] In some preferred embodiments, mapping the timing deviation to a timing advance command field with a sign and a deviation value using a preset encoding rule includes: One bit of the timing advance command field is used as a sign flag bit, and the remaining bits are used as value bits.

[0016] In some preferred embodiments, the timing deviation is mapped to a timing advance command field with a sign and a deviation value using a threshold difference method, including: When the value represented by the advance timing command field does not exceed a preset threshold, the polarity of the symbol is the preset polarity, and the deviation value is the value represented by the advance timing command field. When the value represented by the advance timing command field is greater than a preset threshold, the polarity of the sign is opposite to the preset polarity, and the deviation value is the difference between the value represented by the advance timing command field and the preset threshold.

[0017] In some preferred embodiments, the network-side device uses the difference between the arrival time of the uplink signal and the theoretical propagation delay as the timing deviation, where the theoretical propagation delay is the propagation time of the uplink signal between the user equipment and the satellite.

[0018] Secondly, the present invention also provides a method for supporting lag indication in timing advance commands in NTN satellite communication, applied to user equipment, the method comprising the following steps: Receive system information broadcast by satellite and calculate the initial timing advance; The initial timing advance is sent to the network-side device so that the network-side device can estimate the timing deviation based on the initial timing advance and map the timing deviation into a timing advance command field with a sign and a deviation value through a preset encoding rule. Then, the timing advance command field is constructed and expanded into a timing adjustment command and sent to the user equipment. The timing deviation has positive and negative polarities. When it is positive, it is used to indicate timing advance, and when it is negative, it is used to indicate timing lag. The timing adjustment command is received, and a timing advance command field with a sign and a deviation value is parsed out according to a preset decoding rule. The sign is used to represent the polarity of the timing deviation, and the deviation value is used to represent the absolute value of the timing deviation. Based on the polarity of the symbol, the uplink transmission timing is adjusted to either advance or lag the timing according to the deviation value.

[0019] In some preferred embodiments, the step of receiving system information broadcast by satellite and calculating the initial timing advance includes: User equipment receives common timing advance parameters and satellite ephemeris data from SIB19; The user equipment calculates the satellite's position based on the satellite ephemeris data; The user equipment uses the GNSS module to obtain its own geographic coordinates, and calculates the geometric distance D between the user equipment and the satellite based on its own geographic coordinates and the position of the satellite; The user equipment converts the geometric distance D into a light propagation delay τ, where τ = D / c, and c is the speed of light. The user equipment calculates the initial timing advance T_UE, where T_UE = τ - τ_RP, and τ_RP is the CommonTA delay corresponding to the reference point RP.

[0020] Thirdly, the present invention also provides a network-side device, comprising: The uplink receiving module is used to receive uplink signals sent by user equipment; The timing deviation estimation module is used to estimate the timing deviation of the user equipment based on the uplink signal. The timing deviation has positive and negative polarities. When it is positive, it is used to indicate timing advance, and when it is negative, it is used to indicate timing lag. The timing advance command generation module is used to map the timing deviation into a timing advance command field with a sign and a deviation value through a preset encoding rule. The sign is used to represent the polarity of the timing deviation, and the deviation value is used to represent the absolute value of the timing deviation. The system also includes a sending module, which constructs and expands the timing advance command field into a timing adjustment command and sends it to the user equipment. This enables the user equipment to parse the sign and deviation value of the timing advance command field after receiving the timing adjustment command, and to perform timing advance or timing lag adjustment on the uplink transmission timing according to the polarity of the sign, corresponding to the deviation value.

[0021] Fourthly, the present invention also provides a user equipment, comprising: The satellite ephemeris receiver module is used to receive satellite ephemeris information broadcast by satellite; The initial timing calculation module is used to calculate the geometric distance from the user equipment to the satellite by combining the satellite ephemeris information and its own GNSS positioning data, and to calculate the initial timing advance accordingly. The uplink transmission module is used to transmit an uplink signal according to the initial timing advance, so that the network-side device can estimate the timing deviation based on the initial timing advance after receiving the uplink signal, and map the timing deviation into a timing advance command field with a sign and a deviation value through a preset encoding rule. Then, the timing advance command field is constructed and expanded into a timing adjustment command and sent to the user equipment. The timing deviation has positive and negative polarities, with positive indicating timing advance and negative indicating timing lag. The parsing module is used to receive timing adjustment commands and parse out a timing advance command field with a sign and a deviation value, wherein the sign is used to represent the polarity of the timing deviation and the deviation value is used to represent the absolute value of the timing deviation. And a timing adjustment module, used to adjust the uplink transmission timing according to the polarity of the symbol, corresponding to the deviation value, by timing advance or timing lag.

[0022] Fifthly, the present invention also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, performs the method described above.

[0023] By adopting the above technical solution, the beneficial effects of the present invention are as follows: 1. Effectively solves the PRACH overcompensation problem caused by NTN ephemeris errors, improving the success rate of random access.

[0024] In NTN satellite communication scenarios, the UE autonomously calculates timing advance based on ephemeris data. However, factors such as ephemeris errors, satellite attitude deviations, and atmospheric refraction can cause discrepancies between the calculated and actual values. When the timing advance calculated by the UE is too large, the UE transmits too early (overcompensated), and the PRACH preamble arrives at the satellite earlier than the ideal time. Existing technologies, RAR TA commands can only indicate advance and cannot correct this overcompensation problem. This invention extends the RAR TA command to support simultaneous indication of advance and lag (negative adjustment), enabling the gNB to issue a negative TA command (timing lag) to the UE based on the actual measured timing deviation. This accurately corrects overcompensation, ensuring the UE's PRACH transmission time falls precisely within the satellite receiver's CP window, significantly improving the random access success rate.

[0025] 2. The extended encoding scheme is simple and flexible, compatible with existing protocol structures, and has low modification costs.

[0026] This invention provides two encoding extension schemes to adapt to different deployment requirements. Scheme A (sign bit multiplexing) reuses the reserved bit in RAR as the sign bit, resulting in an 11-bit value + 1-bit sign = 12-bit signed TA command, requiring minimal modification. Scheme B (threshold differential coding) fully reuses the existing 12-bit field, setting Th=512. A value ≤ 512 indicates advance (value × Tc), and a value > 512 indicates lag (value - 512) × Tc, without any changes to the MAC layer structure. Both schemes support backward compatibility; Legacy UEs that do not support the new encoding can continue to interpret the value as a pure advance according to the original rules. Furthermore, the extended signed TA command is also applicable to Timing Advance MAC CE in connected mode, enabling bidirectional fine-tuning of uplink timing throughout the entire NTN lifecycle.

[0027] 3. Seamlessly integrates with the 3GPP R17 NTN split timing advance architecture, enhancing overall timing synchronization accuracy.

[0028] The separate timing advance architecture (Common TA + UE-specific calculation + k_offset / k_mac offset) introduced in 3GPP R17 provides basic timing synchronization capabilities for NTN. Building upon this architecture, this invention further corrects residual timing errors after UE-autonomous pre-compensation using signed TA commands at the RAR level on the network side. This two-tier architecture of pre-compensation + network fine-tuning is highly consistent with the design philosophy of the 3GPP standard. It leverages the advantages of real-time pre-compensation assisted by UE-side ephemeris while retaining the network-side's precise adjustment capabilities based on measured deviations, forming a complementary advantage and significantly improving the overall timing synchronization accuracy in NTN scenarios.

[0029] 4. This invention supports signed timing adjustment by extending the RAR TA command without introducing new security risks. The timing adjustment command is generated by the gNB based on physical layer received measurements, making it impossible for attackers to forge valid timing deviation information. The UE's interpretation of the TA command in RAR follows the protocol's predefined encoding rules, eliminating security vulnerabilities caused by parsing ambiguity. Furthermore, this invention has no impact on security mechanisms above the MAC layer (PDCP encryption, integrity protection, etc.), and the preconditions for secure communication remain unchanged. Attached Figure Description

[0030] Figure 1 This is a flowchart illustrating a method for supporting lag indication in timing advance commands during NTN satellite communication according to Embodiment 1 of the present invention. Figure 2 This is a schematic diagram illustrating the encoding of the timing advance command field in this invention; Figure 3This is a schematic diagram of the user equipment in this invention; Figure 4 This is a flowchart illustrating a method for supporting lag indication in timing advance commands during NTN satellite communication according to Embodiment 4 of the present invention. Figure 5 This is a schematic diagram of the network-side device in this invention. Detailed Implementation

[0031] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0032] Example 1 See Figure 1 This is a flowchart illustrating a method for supporting hysteresis indication in timing advance commands during NTN satellite communication, provided by an embodiment of the present invention. Figure 1 The execution subject of the method shown is a user device, which may include, but is not limited to, computers, smartphones, personal digital assistants (PDAs), and the aforementioned electronic devices.

[0033] The method provided in this embodiment of the invention specifically includes the following steps: Step S01: The user equipment receives system information broadcast by the satellite and calculates the initial timing advance.

[0034] After powering on, the user equipment (UE) acquires the ta-Common parameter (common timing advance) and satellite ephemeris information via SIB19. The UE uses its GNSS module to obtain its own geographic coordinates, calculates the satellite's current position based on the ephemeris information, and then calculates the geometric distance D from the UE to the satellite. This geometric distance D is converted into a light propagation delay τ = D / c, from which the estimated one-way propagation delay from the UE to the satellite is obtained. The UE then uses the Common TA to calculate the initial timing advance T_UE for uplink PRACH transmission, T_UE = τ - τ_RP, where τ_RP is the Common TA delay corresponding to the reference point RP.

[0035] Step S02: The user equipment sends the initial timing advance to the network-side equipment.

[0036] The user equipment sends a random access preamble in the PRACH time domain according to the calculated initial timing advance T_UE, so that the network-side equipment can estimate the timing deviation based on the initial timing advance, and map the timing deviation into a timing advance command field with a sign and deviation value through a preset coding rule, and then construct and expand the timing advance command field into a timing adjustment command and send it to the user equipment.

[0037] After receiving the PRACH preamble sent by the user equipment (UE), the network-side device performs timing estimation based on the received preamble sequence to obtain the actual arrival time of the PRACH preamble, ToA_actual. Simultaneously, the network-side device calculates the theoretical propagation delay τ_theory from the UE to the satellite based on satellite ephemeris information and the UE's location registration information. The difference between these two values ​​is the timing deviation ΔT_raw of the UE, where ΔT_raw = ToA_actual - τ_theory. This timing deviation has positive and negative polarities. A positive deviation indicates timing advance, while a negative deviation indicates timing lag. Timing advance means the UE is sending too late, indicating undercompensation, and needs to be advanced; timing lag means the UE is sending too early, indicating overcompensation, and needs to be delayed.

[0038] In existing technologies, the timing advance command field contains 12 bits, which can only represent numerical values ​​and cannot represent signs. However, in this embodiment, the network-side device maps the timing deviation to a timing advance command field with a sign and deviation value using a preset encoding rule, such as... Figure 2 As shown, there are two options: Option A: Use one bit (e.g., reserved bit) from the original 12 bits of the advance timing command field as a sign bit. That is, one bit is the sign bit, and the remaining bits are still used as value bits, forming 11 value bits and 1 sign bit. The time range that can be represented is -2046×Tc to +2046×Tc, where Tc is the basic time unit.

[0039] For example, a sign bit value of 0 indicates positive polarity, meaning a timing advance is needed, with the advance amount represented by 11 bits (N×Tc). A sign bit value of 1 indicates negative polarity, meaning a timing lag is needed, with the lag amount represented by 11 bits (N×Tc). Alternatively, a sign bit value of 0 can represent negative polarity, and a sign bit value of 1 can represent positive polarity.

[0040] When the number of bits in the advance timing command field changes, for example, to N bits, it is expanded by a preset encoding rule to form a 1-bit sign bit and N-1 bits of value bits.

[0041] Scheme B (Threshold Difference Method): When the value represented by the timing advance command field does not exceed the preset threshold, the polarity of the sign is the preset polarity, and the deviation value is the value represented by the timing advance command field; when the value represented by the timing advance command field is greater than the preset threshold, the polarity of the sign is opposite to the preset polarity, and the deviation value is the difference between the value represented by the timing advance command field and the preset threshold.

[0042] For example, if the preset threshold Th is 512, when the value N represented by the timing advance command field is less than or equal to 512, it indicates that timing advance is required, and the advance amount is N × Tc. When the value N represented by the timing advance command field is greater than 512, it indicates that timing lag is required, and the lag amount is (N - 512) × Tc. This preset threshold Th can be configured by the network through RRC or predefined by the protocol. In other preferred embodiments, the preset polarity can also be defined in reverse, that is, when the value N represented by the timing advance command field is less than or equal to 512, it indicates that timing lag is required.

[0043] Step S03: The user equipment receives the timing adjustment command and parses out the timing advance command field with a sign and a deviation value through a preset decoding rule. The sign is used to indicate the polarity of the timing deviation, and the deviation value is used to indicate the absolute value of the timing deviation.

[0044] The network-side device fills the timing advance command field with the aforementioned extended encoding, sign, and offset values ​​into the RAR MAC PDU, and sends it to the user equipment through a combined structure of MAC Subheader + MAC RAR.

[0045] The user equipment listens to the downlink PDSCH within the RAR window and receives the RAR MAC PDU sent by the network-side device. The user equipment parses the timing advance command field with a sign and a deviation value from it according to the preset decoding rules. The sign is used to indicate the polarity of the timing deviation, and the deviation value is used to indicate the absolute value of the timing deviation.

[0046] Step S04: The user equipment performs timing advance or timing lag adjustments on the uplink transmission timing according to the polarity of the symbol, corresponding to the deviation value, to ensure that the uplink signal always falls within the CP window of the satellite receiver.

[0047] Specifically, the user equipment makes incremental adjustments based on the initial timing advance. The increment is either the advance (positive value) or the lag (negative value) indicated by the timing advance command field. For example, if the user equipment parses the timing advance command field and finds it to be positive, it indicates timing advance, and the user equipment will advance the uplink transmission time by ΔT_raw based on the initial timing advance. If the user equipment parses the timing advance command field and finds it to be negative, it indicates timing lag, and the user equipment will lag the uplink transmission time by |ΔT_raw| based on the initial timing advance.

[0048] After the adjustment is completed, the user equipment sends MSG3 data via PUSCH under the UL Grant scheduling allocated in RAR. At this time, the uplink timing of the user equipment has been finely corrected by the network-side equipment through a signed timing advance command, effectively compensating for the timing deviation introduced by ephemeris errors.

[0049] In step S01, if the uplink signal can also be a PUSCH or SRS uplink reference signal, the network-side device will send the timing adjustment command to the user equipment through the Timing Advance MAC CE.

[0050] This invention also applies to timing adjustment commands in connected mode, enabling network-side devices to continuously correct timing drift (both advance and lag) caused by high-speed satellite movement. User equipment (UE) continuously updates its uplink transmission timing based on the received timing adjustment commands (supporting both positive and negative directions), ensuring the uplink signal always falls within the satellite receiver's CP window. Specifically, in connected mode, network-side devices can further fine-tune the UE's timing using traditional Timing Advance MAC CE.

[0051] This invention uses a LEO transparent forwarding NTN system as an example to illustrate the specific implementation process. Assume the LEO satellite altitude is 600km, the architecture is transparent, and the UE is located within the satellite's coverage area. After powering on, the UE first receives the ta-Common (common timing advance) and satellite ephemeris parameters (ephemerisInfo, containing the satellite's position and velocity vectors in the ECEF coordinate system) from SIB19. The UE uses GNSS to obtain its own coordinates and, combined with the ephemeris, calculates the UE-satellite geometric distance D = 850km, converting it to obtain a one-way propagation delay τ = D / c ≈ 2.83ms. The UE calculates the uplink PRACH timing advance T_PRACH = τ - τ_RP = 2.83ms - 2.50ms = 0.33ms and sends the PRACH preamble according to this timing advance.

[0052] After receiving the PRACH preamble, the network-side device estimates the timing to ToA_actual = 2.85ms, while the theoretical delay τ_theory = 2.83ms. The timing deviation ΔT is calculated to be +0.02ms (a positive value indicates the UE is sending too late, meaning the UE's pre-compensation is too small, resulting in undercompensation, requiring earlier timing). The network-side device quantizes this deviation into a positive TA command (timing advance) and sends it to the UE via RAR. Upon receiving the RAR, the UE parses the TA command value as +2 (i.e., advancing by 2 TA basic units) and advances the PRACH timing by the corresponding amount.

[0053] On the other hand, assuming there are errors in the UE's ephemeris data, causing the UE's calculated T_PRACH to be too large (i.e., too early, resulting in premature transmission), the timing deviation ΔT_raw measured by the network-side equipment will be negative (e.g., -0.01ms, indicating overcompensation and requiring a delay). The network-side equipment encodes this negative deviation into a signed timing advance command field (e.g., using the above scheme A: sign bit = 1, value bit = 1, indicating a delay of 1×Tc), and sends it to the UE via RAR. After parsing the negative timing advance command, the UE delays the uplink transmission time by the corresponding amount, thereby correcting the overcompensation problem caused by the ephemeris error.

[0054] The above process is continuously executed in connected mode via Timing Advance MAC CE to ensure that the UE's uplink timing is always accurately synchronized.

[0055] Example 2 This invention provides a user equipment, such as... Figure 3 As shown, the user equipment includes a satellite ephemeris receiving module, an initial timing calculation module, an uplink transmission module, a parsing module, and a timing adjustment module.

[0056] The satellite ephemeris receiver module is used to receive satellite ephemeris information broadcast by satellite.

[0057] The initial timing calculation module is used to calculate the geometric distance from the user equipment to the satellite by combining satellite ephemeris information and its own GNSS positioning data, and to calculate the initial timing lead accordingly.

[0058] The uplink transmission module is used to transmit uplink signals according to the initial timing advance.

[0059] The parsing module is used to receive timing adjustment commands and parse out the timing advance command field with a sign and a deviation value. The sign is used to indicate the polarity of the timing deviation, and the deviation value is used to indicate the absolute value of the timing deviation.

[0060] The timing adjustment module is used to adjust the uplink transmission timing according to the polarity of the symbol, and to adjust the timing advance or timing lag corresponding to the deviation value, so as to ensure that the uplink signal always falls within the CP window of the satellite receiver.

[0061] After the user equipment (UE) is powered on, the satellite ephemeris receiving module acquires the ta-Common parameter (common timing advance) and satellite ephemeris information by receiving SIB19 data. Simultaneously, it uses the GNSS module to obtain its own geographic coordinates and calculates the satellite's current position based on the ephemeris information. This allows it to calculate the geometric distance D from the UE to the satellite, converting D into a light propagation delay τ = D / c, thus obtaining an estimate of the one-way propagation delay from the UE to the satellite. The initial timing calculation module, in conjunction with the Common TA, calculates the initial timing advance T_UE for uplink PRACH transmission, where T_UE = τ - τ_RP, and τ_RP is the Common TA delay corresponding to the reference point RP.

[0062] The uplink transmission module transmits a random access preamble in the PRACH time domain according to the calculated initial timing advance T_UE. This allows the network-side device to estimate the timing deviation based on the initial timing advance after receiving the PRACH preamble. The timing deviation has positive and negative polarities; a positive deviation indicates timing advance, and a negative deviation indicates timing lag. Then, using a preset encoding rule, the timing deviation is mapped into a timing advance command field with a sign and deviation value. The network-side device fills the RAR MAC PDU with the aforementioned extended encoding of the timing advance command field with the sign and deviation value, and sends it to the user equipment through a combined structure of MAC Subheader + MAC RAR. The user equipment listens for the downlink PDSCH within the RAR window and receives the RAR MAC PDU sent by the network-side device.

[0063] The parsing module extracts the timing advance command field with a sign and a deviation value from the preset decoding rules. The sign is used to indicate the polarity of the timing deviation, and the deviation value is used to indicate the absolute value of the timing deviation.

[0064] The timing adjustment module makes incremental adjustments based on the initial timing advance. The increment is either the advance (positive value) or the lag (negative value) indicated by the timing advance command field. For example, if the parsing module finds the sign of the timing advance command field to be positive, indicating timing advance, the timing adjustment module will advance the uplink transmission time by ΔT_raw based on the initial timing advance. If the parsing module finds the sign of the timing advance command field to be negative, indicating timing lag, the timing adjustment module will lag the uplink transmission time by |ΔT_raw| based on the initial timing advance.

[0065] After the adjustment is completed, the user equipment sends MSG3 data via PUSCH under the UL Grant scheduling allocated in RAR. At this time, the uplink timing of the user equipment has been finely corrected by the network-side equipment through a signed timing advance command, effectively compensating for the timing deviation introduced by ephemeris errors.

[0066] Example 3 See Figure 4 This is a flowchart illustrating a method for supporting hysteresis indication in timing advance commands during NTN satellite communication, provided by an embodiment of the present invention. Figure 4 The method shown is implemented by network-side equipment, such as a base station gNB mounted on the ground or satellite.

[0067] The method provided in this embodiment of the invention specifically includes the following steps: Step S11: The network-side device receives the uplink signal sent by the user equipment.

[0068] Step S12: The network-side device estimates the timing deviation of the user equipment based on the uplink signal. The timing deviation has positive and negative polarities. When it is positive, it is used to indicate timing advance, and when it is negative, it is used to indicate timing lag.

[0069] Step S13: The network-side device maps the timing deviation into a timing advance command field with a sign and a deviation value through a preset encoding rule. The sign is used to indicate the polarity of the timing deviation, and the deviation value is used to indicate the absolute value of the timing deviation.

[0070] Step S14: The network-side device constructs and expands the timing advance command field into a timing adjustment command and sends it to the user equipment. After receiving the timing adjustment command, the user equipment can parse the sign and deviation value of the timing advance command field, and perform timing advance or timing lag adjustment on the uplink transmission timing according to the polarity of the sign, so as to ensure that the uplink signal always falls within the CP window of the satellite receiver.

[0071] In step S11, the uplink signal sent by the user equipment can be a PRACH preamble. After calculating the initial timing advance based on step S01 in Embodiment 1, the user equipment sends a random access preamble in the PRACH time domain according to the calculated initial timing advance T_UE.

[0072] In step S12, after receiving the PRACH preamble sent by the user equipment, the network-side device performs timing estimation based on the received preamble sequence to obtain the actual arrival time of the PRACH preamble, ToA_actual. Simultaneously, the network-side device calculates the theoretical propagation delay τ_theory from the user equipment to the satellite based on satellite ephemeris information and the user equipment's location registration information. The difference between the two is the timing deviation ΔT_raw of the user equipment, where ΔT_raw = ToA_actual - τ_theory. This timing deviation has positive and negative polarities. When it is positive, it indicates timing advance; when it is negative, it indicates timing lag. Timing advance means the user equipment sent the signal too late, indicating undercompensation, and needs to be advanced; timing lag means the user equipment sent the signal too early, indicating overcompensation, and needs to be delayed.

[0073] In step S13, the timing advance command field in the prior art contains 12 bits, which can only represent numerical values ​​and cannot represent signs. In this embodiment, the network-side device maps the timing deviation to a timing advance command field with a sign and deviation value using preset encoding rules, including two schemes: Option A: Use one bit (e.g., reserved bit) from the original 12 bits of the advance timing command field as a sign bit. That is, use one bit as a sign bit and use the remaining bits as value bits to form 11 value bits and 1 sign bit. The time range that can be represented is -2046×Tc to +2046×Tc, where Tc is the basic time unit.

[0074] For example, a sign bit value of 0 indicates positive polarity, meaning a timing advance is needed, with the advance amount represented by 11 bits (N×Tc). A sign bit value of 1 indicates negative polarity, meaning a timing lag is needed, with the lag amount represented by 11 bits (N×Tc). Alternatively, a sign bit value of 0 can represent negative polarity, and a sign bit value of 1 can represent positive polarity.

[0075] When the number of bits in the advance timing command field changes, for example, to N bits, it is expanded by a preset encoding rule to form a 1-bit sign bit and N-1 bits of value bits.

[0076] Scheme B (Threshold Difference Method): When the value represented by the timing advance command field does not exceed the preset threshold, the polarity of the sign is the preset polarity, and the deviation value is the value represented by the timing advance command field; when the value represented by the timing advance command field is greater than the preset threshold, the polarity of the sign is opposite to the preset polarity, and the deviation value is the difference between the value represented by the timing advance command field and the preset threshold.

[0077] For example, if the preset threshold Th is 512, when the value N represented by the timing advance command field is less than or equal to 512, it indicates that timing advance is required, and the advance amount is N × Tc. When the value N represented by the timing advance command field is greater than 512, it indicates that timing lag is required, and the lag amount is (N - 512) × Tc. This preset threshold Th can be configured by the network through RRC or predefined by the protocol. In other preferred embodiments, the preset polarity can also be defined in reverse, that is, when the value N represented by the timing advance command field is less than or equal to 512, it indicates that timing lag is required.

[0078] In step S14, the network-side device fills the timing advance command field with the aforementioned extended encoding, which contains the sign and offset values, into the RAR MAC PDU, and sends it to the user equipment through a combined structure of MAC Subheader + MAC RAR.

[0079] The user equipment listens to the downlink PDSCH within the RAR window and receives the RAR MAC PDU sent by the network-side device. The user equipment parses the timing advance command field with a sign and a deviation value from it according to the preset decoding rules. The sign is used to indicate the polarity of the timing deviation, and the deviation value is used to indicate the absolute value of the timing deviation.

[0080] In step S11, if the uplink signal can also be a PUSCH or SRS uplink reference signal, the network-side device will send the timing adjustment command to the user equipment through the Timing Advance MAC CE.

[0081] In the connected state after random access is completed, the network-side equipment continuously monitors the timing deviation of the user equipment (UE) via the PUSCH or SRS uplink reference signal. For timing drift caused by high-speed satellite movement in NTN scenarios, the network-side equipment periodically calculates the timing deviation and issues timing adjustment commands via Timing Advance MAC CE (also extended to a signed format). When the UE's timing is consistently ahead (overcompensated), the network-side equipment issues a negative timing adjustment command to indicate that the UE is lagging; when the UE's timing is consistently lagging (undercompensated), the network-side equipment issues a positive timing adjustment command to indicate that the UE is further ahead.

[0082] Example 4 This invention also provides a network-side device, such as... Figure 5 As shown, it includes an uplink receiving module, a timing deviation estimation module, a timing advance command generation module, and a sending module.

[0083] The uplink receiving module is used to receive uplink signals sent by user equipment; The timing deviation estimation module is used to estimate the timing deviation of the user equipment based on the uplink signal. The timing deviation has positive and negative polarities. When it is positive, it is used to indicate timing advance, and when it is negative, it is used to indicate timing lag. The timing advance command generation module is used to map timing deviations into timing advance command fields with signs and deviation values ​​through preset encoding rules. The signs are used to indicate the polarity of the timing deviation, and the deviation values ​​are used to indicate the absolute value of the timing deviation. The transmitting module is used to construct and expand the timing advance command field into a timing adjustment command and send it to the user equipment. After receiving the timing adjustment command, the user equipment can parse the sign and deviation value of the timing advance command field, and perform timing advance or timing lag adjustment on the uplink transmission timing according to the polarity of the sign, so as to ensure that the uplink signal always falls within the CP window of the satellite receiver.

[0084] Example 5 A computer storage medium storing a computer program, wherein the computer program is executed by a processor to perform the method steps disclosed in Embodiment 1 or 3 above.

[0085] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will 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 processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0086] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0087] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0088] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "front", "rear", etc., indicate the orientation or positional relationship based on the description of the structure of this invention shown in the accompanying drawings. They are only for the convenience of describing this invention and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0089] The terms "first" and "second" in this technical solution are merely designations for corresponding structures that are identical or similar, or that perform similar functions. They do not represent an arrangement of the importance of these structures, nor do they imply any ranking, comparison of size, or other meaning.

[0090] Furthermore, unless otherwise explicitly specified and limited, the terms "installation" and "connection" should be interpreted broadly. For example, a connection can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two structures. Those skilled in the art can understand the specific meaning of the above terms in this invention by considering the overall concept of the invention and the specific context of the solution.

[0091] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A method for supporting lag indication in timing advance commands in NTN satellite communication, applied to network-side equipment, characterized in that, The method includes the following steps: Receive uplink signals sent by user equipment; Based on the uplink signal, the timing deviation of the user equipment is estimated. The timing deviation has positive and negative polarities. When it is positive, it is used to indicate timing advance, and when it is negative, it is used to indicate timing lag. The timing deviation is mapped to a timing advance command field with a sign and a deviation value through a preset encoding rule. The sign is used to represent the polarity of the timing deviation, and the deviation value is used to represent the absolute value of the timing deviation. The timing advance command field is constructed and expanded into a timing adjustment command and sent to the user equipment. After receiving the timing adjustment command, the user equipment can parse the sign and deviation value of the timing advance command field, and perform timing advance or timing lag adjustment corresponding to the deviation value on the uplink according to the polarity of the sign.

2. The method according to claim 1, characterized in that: When the uplink signal is a PRACH preamble, the network-side device fills the timing advance command field in the RAR MAC PDU and sends it to the user equipment through a combination of MAC Subheader and MAC RAR. When the uplink signal is a PUSCH or SRS uplink reference signal, the network-side device sends the timing adjustment command to the user equipment via Timing Advance MACCE.

3. The method according to claim 1, characterized in that: The step of mapping the timing deviation to a timing advance command field with a sign and a deviation value using a preset encoding rule includes: One bit of the timing advance command field is used as a sign flag bit, and the remaining bits are used as value bits.

4. The method according to claim 1, characterized in that: The timing deviation is mapped to a timing advance command field with a sign and a deviation value using a threshold difference method, including: When the value represented by the advance timing command field does not exceed a preset threshold, the polarity of the symbol is the preset polarity, and the deviation value is the value represented by the advance timing command field. When the value represented by the advance timing command field is greater than a preset threshold, the polarity of the sign is opposite to the preset polarity, and the deviation value is the difference between the value represented by the advance timing command field and the preset threshold.

5. The method according to claim 1, characterized in that: The network-side equipment measures the difference between the arrival time of the uplink signal and the theoretical propagation delay as the timing deviation, where the theoretical propagation delay is the propagation time of the uplink signal between the user equipment and the satellite.

6. A method for supporting hysteresis indication in timing advance commands in NTN satellite communication, applied to user equipment, characterized in that, The method includes the following steps: Receive system information broadcast by satellite and calculate the initial timing advance; The initial timing advance is sent to the network-side device so that the network-side device can estimate the timing deviation based on the initial timing advance and map the timing deviation into a timing advance command field with a sign and a deviation value through a preset encoding rule. Then, the timing advance command field is constructed and expanded into a timing adjustment command and sent to the user equipment. The timing deviation has positive and negative polarities. When it is positive, it is used to indicate timing advance, and when it is negative, it is used to indicate timing lag. The timing adjustment command is received, and a timing advance command field with a sign and a deviation value is parsed out according to a preset decoding rule. The sign is used to represent the polarity of the timing deviation, and the deviation value is used to represent the absolute value of the timing deviation. Based on the polarity of the symbol, the uplink transmission timing is adjusted to either advance or lag the timing according to the deviation value.

7. The method according to claim 6, characterized in that, The steps of receiving system information broadcast by satellite and calculating the initial timing advance include: User equipment receives common timing advance parameters and satellite ephemeris data from SIB19; The user equipment calculates the satellite's position based on the satellite ephemeris data; The user equipment uses the GNSS module to obtain its own geographic coordinates, and calculates the geometric distance D between the user equipment and the satellite based on its own geographic coordinates and the position of the satellite; The user equipment converts the geometric distance D into a light propagation delay τ, where τ = D / c, and c is the speed of light. The user equipment calculates the initial timing advance T_UE, where T_UE = τ - τ_RP, and τ_RP is the Common TA delay corresponding to the reference point RP.

8. A network-side device, characterized in that, include: The uplink receiving module is used to receive uplink signals sent by user equipment; The timing deviation estimation module is used to estimate the timing deviation of the user equipment based on the uplink signal. The timing deviation has positive and negative polarities. When it is positive, it is used to indicate timing advance, and when it is negative, it is used to indicate timing lag. The timing advance command generation module is used to map the timing deviation into a timing advance command field with a sign and a deviation value through a preset encoding rule. The sign is used to represent the polarity of the timing deviation, and the deviation value is used to represent the absolute value of the timing deviation. The system also includes a sending module, which constructs and expands the timing advance command field into a timing adjustment command and sends it to the user equipment. This enables the user equipment to parse the sign and deviation value of the timing advance command field after receiving the timing adjustment command, and to perform timing advance or timing lag adjustment on the uplink transmission timing according to the polarity of the sign, corresponding to the deviation value.

9. A user equipment, characterized in that, include: The satellite ephemeris receiver module is used to receive satellite ephemeris information broadcast by satellite; The initial timing calculation module is used to calculate the geometric distance from the user equipment to the satellite by combining the satellite ephemeris information and its own GNSS positioning data, and to calculate the initial timing advance accordingly. The uplink transmission module is used to transmit an uplink signal according to the initial timing advance, so that the network-side device can estimate the timing deviation based on the initial timing advance after receiving the uplink signal, and map the timing deviation into a timing advance command field with a sign and a deviation value through a preset encoding rule. Then, the timing advance command field is constructed and expanded into a timing adjustment command and sent to the user equipment. The timing deviation has positive and negative polarities, with positive indicating timing advance and negative indicating timing lag. The parsing module is used to receive timing adjustment commands and parse out a timing advance command field with a sign and a deviation value, wherein the sign is used to represent the polarity of the timing deviation and the deviation value is used to represent the absolute value of the timing deviation. And a timing adjustment module, used to adjust the uplink transmission timing according to the polarity of the symbol, corresponding to the deviation value, by timing advance or timing lag.

10. A computer-readable storage medium storing a computer program, characterized in that: The computer program is executed by the processor to perform the method as described in any one of claims 1-7.

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