6g low earth orbit satellite random access signal generation and detection method based on zc sequence

Abstract

This invention discloses a method for generating a random access signal transmission sequence for 6G low-Earth orbit satellites based on ZC sequences, belonging to the field of satellite wireless communication technology. The random access signal of this invention includes a cyclic prefix, a preamble sequence, and a guard interval. The preamble sequence is obtained by multiplying corresponding elements of two sequences of length N. The mathematical expression for the access preamble sequence is as follows: where the first sequence is a sequence with root value s and length N. ZC The length of the short ZC sequence obtained by repeating it K times is N (N = K·N). ZC The first sequence is a sequence of two random access preambles, the short sequences of which are completely identical; the second sequence is the result of adding and multiplying two ZC sequences of length N with root values ​​r1 and r2 respectively. This invention can effectively combat frequency offset and is applicable to scenarios where the terminal is not stationary, and has the advantage of maintaining good detection performance even in scenarios with large frequency offset.

Description

Technical Field

[0001] This invention belongs to the field of satellite wireless communication technology, specifically, it relates to a method for generating a random access signal transmission sequence for 6G low-Earth orbit satellites based on ZC sequences and a method for detecting the receiver. Background Technology

[0002] The rapid development of mobile communication systems has greatly facilitated daily life. With the increasing demand for communication and the continuous expansion of new services, the integration of terrestrial cellular communication systems and satellite communication systems has gradually become one of the research hotspots of next-generation communication technology (6G). Compared with medium and high orbit satellite communication systems, low earth orbit (LEO) satellite communication systems, with their mature technology, wide coverage, and low transmission latency, can serve as an effective extension of terrestrial cellular systems, laying the foundation for realizing integrated space-ground communication networks.

[0003] Random access technology is one of the key technologies in cellular communication systems. Its main function is to establish a communication link between the base station and the user, obtain timing advance information, and ensure reliable uplink data transmission. In the random access process of current 4G and 5G cellular systems on the ground, the base station determines whether the corresponding user wants to access the system and the corresponding round-trip transmission delay by detecting all possible random access preamble sequences one by one. The base station feeds back the detected information to the user equipment, and the user equipment adjusts the timing advance (TA) according to the received delay information and sends subsequent data information.

[0004] Unlike current terrestrial 4G and 5G cellular communication systems, satellite communication systems have longer propagation distances, wider coverage, and faster relative speeds between user terminals and satellites. This means that existing 4G (e.g., LTE) and 5G (e.g., NR) random access technologies are not directly applicable to satellite communication systems. Therefore, the transceiver end of the random access signal needs to be redesigned to adapt to the characteristics of low-Earth orbit satellite communication systems and be compatible with terrestrial communication systems. In particular, the relative motion between the satellite and the user terminal in satellite communication systems generates significant Doppler frequency offsets, which will cause received signal distortion and severely affect the detection of random access signals at the receiver. Therefore, being able to handle large frequency offsets has become one of the challenges in designing the transceiver end of the random access signal.

[0005] Existing random access signal designs fail to simultaneously consider the wide coverage, large transmission delay, numerous user terminal devices, and significant Doppler frequency offset characteristics of low-Earth orbit satellite systems. Reference CN2022102755797 presents a random access preamble design scheme adapted to the channel characteristics of satellite communication systems. However, this scheme does not consider frequency offset, meaning it is only applicable to scenarios where user terminals are stationary, and requires GNSS equipment to predict satellite motion trajectories to avoid frequency offset caused by satellite movement. This invention comprehensively considers these factors, including frequency offset, and redesigns the random access signal sequence at the transmitting end and the detection timing scheme at the receiving end. The scheme designed in this invention is also applicable in scenarios where terminal devices are moving (i.e., scenarios with frequency offset), and has broader application value. Summary of the Invention

[0006] Compared to current 4G and 5G terrestrial cellular communication systems, satellite communication has longer propagation delays and greater frequency offsets, which cause severe distortion of the received signal and affect the timing and detection performance of the receiver. To address these problems in existing technologies, this invention aims to provide a method for generating physical layer random access signal transmission sequences and timing detection at the receiver, applicable to LEO satellite systems. This method includes the design of a random access preamble scheme, a root value set generation algorithm, and a timing detection algorithm at the receiver. The proposed method can combat frequency offsets without affecting the timing and detection performance of the receiver.

[0007] To address the aforementioned problems, the technical solution adopted by this invention is as follows: the random access signal includes a cyclic prefix (CP), a preamble sequence, and a guard time (GT).

[0008] The preamble sequence is obtained by multiplying corresponding elements of two sequences of length N. The mathematical expression for the preamble sequence is as follows: The first sequence is a sequence with root value s and length N. ZC The length of the short ZC sequence obtained by repeating it K times is N (N = K·N). ZC The short sequences of different random access leader sequences are completely identical;

[0009] The second sequence is the sum and multiplication of two ZC sequences of length N with root values ​​r1 and r2 respectively. The resulting sequence.

[0010] As a preferred embodiment of the present invention, the parameters of the preceding sequence are obtained through the following steps:

[0011] S1: Determine the maximum round-trip transmission delay difference between the ground terminal equipment and the low-Earth orbit satellite.

[0012] S2: Based on the maximum round-trip transmission delay difference Determine the duration T of the cyclic prefix CP and the protection interval GT. CP T GT ,

[0013] S3: Determine the duration T of the random access preamble sequence (Sequence). Seq and the length N of the preceding sequence;

[0014] S4: Set the first sequence root value s such that the first sequence root value s is equal to the length N of the short ZC sequence. ZC Coprime;

[0015] S5: Obtain the set R consisting of the second sequence root values ​​r1 and r2 used by different random access leader sequences (the number of random access leader sequences required is I). root1 ,R root2 .

[0016] As a preferred embodiment of the present invention, step S1 calculates the maximum round-trip transmission delay difference based on the parameters and coverage area of ​​the LEO satellite system. The specific method is as follows:

[0017] S101: Obtain the beam diameter d of the satellite communication system cell And the Earth's radius D, based on the beam diameter d of the satellite communication system. cell The beam diameter d is calculated from the Earth's radius D. cell Angle with Earth's radius D

[0018] S102: Let the distance between the satellite and the point on Earth where the satellite signal can reach the maximum range be L. Let the angle between the line connecting the satellite and the point on Earth where the satellite signal can reach the maximum range be tangent to the line connecting the satellite and the point on Earth where the satellite signal can reach the maximum range be θ. Then, calculate the minimum distance from the edge of the cell covered by the satellite to the satellite based on the maximum transmission distance L and the minimum communication angle θ.

[0019] S103: Calculate the maximum round-trip time delay difference based on the minimum distance d from the edge of the cell covered by the satellite to the satellite, the maximum transmission distance L, and the speed of light c.

[0020] As a preferred embodiment of the present invention, step S3 specifically includes the following steps:

[0021] S301: Obtain the noise density N0 and noise figure N of the random access channel. f PRACH signal target received power P RA The duration T of the physical layer random access preamble sequence in a 6G terrestrial cellular communication system. ss The random access signal sampling frequency f at the receiving end s False alarm probability p FA And the false negative probability p of the detection system MD ;

[0022] S302: According to the formula Find the detection threshold 'a' and the detection window length. f s The sampling frequency of the randomly accessed signal at the receiving end, symbol This indicates rounding x up;

[0023] S303: According to the formula Obtain the leader sequence energy to thermal noise ratio that meets the detection probability requirements. Where Q1 is the Markum function,

[0024] S304: To meet coverage performance requirements, the duration of the preceding sequence is set to...

[0025] S305: Considering compatibility with the physical layer random access signal design scheme of terrestrial cellular communication systems, the duration T of the preamble sequence is set as follows: Seq The duration of the random access preamble sequence (Sequence) in a 6G terrestrial cellular communication system is K times Tss, i.e., T Seq =K×T SS K is an integer;

[0026] S306: Considering the requirement of maximum round-trip transmission delay difference, let the duration of the preamble sequence be...

[0027] S307: Based on S304, S305, and S306, obtain the smallest positive integer K such that the duration P of the preceding sequence is... Seq =K×T ss ,and and

[0028] S308: Based on the obtained K and the length N of the short ZC sequence ZCThe lengths of the first and second sequences, N = K × N, are obtained. ZC .

[0029] As a preferred embodiment of the present invention, N is determined. ZC In the case of K and N, the root value s of the first short sequence in step S4 is set to s = 1, satisfying the condition s and N. ZC Coprime.

[0030] As a preferred embodiment of the present invention, the set R composed of the root values ​​r1 and r2 of the second sequence in S5 is... root1 (r1∈R root1 ) and R root2 (r2∈R root2 This includes the following steps:

[0031] S501, Initialize parameters N, K, N ZC The required number of random access preamble sequences is I, the first sequence root value is s = 1, and the set of long ZC sequence root values ​​is r1. The set R of the root values ​​r2 of a long ZC sequence root2 [1:I] = 0, the set of all root values ​​of a long ZC sequence And the intermediate variables t=1, r=1, i=1, j=1;

[0032] S502. Check parameter r. If r < N, proceed to step S503; otherwise, initialize parameter t = t + 1, r = 1. R root2 [1:I] = 0, i = 1, j = 1, and return to step S502;

[0033] S503. Check whether r is coprime to N and whether r+s×K is coprime to N; if r satisfies both requirements, proceed to step S504; otherwise, let r = r+1 and jump to step S502.

[0034] S504. If i = 1, put r into set R. root and R root1 In, that is, R root [i] = r, R root1 If [j] = r, and i = i + 1 and j = j + 1, jump to step S506; if i ≠ 1, check r and R. root Any root value element μ (μ∈R) root If g = GCD(N, r-μ) ≤ t, and for some root element μ, g ≤ t is not satisfied, then let r = r + 1 and jump to step S502; otherwise (i.e., for all μ ∈ R...), ... rootIf we have g = GCD(N, r-μ) ≤ t, then we check each value in the range k = 1 to k = j-1 one by one to see if we can find a k such that ((r+Ks) -1 -(R root1 [k]+Ks) -1 )mod N ZC ≠0 and R root2 If [k] = 0, and such a k can be found, for the first k that satisfies the condition, let R root2 [k] = r, and put r into set R. root In, that is, R root [i] = r, and let i = i + 1, then jump to step S506; if no such k can be found in the range k = 1 to k = j - 1 satisfying ((r + Ks) -1 -(R root1 [k]+Ks) -1 )mod N ZC ≠0 and R root2 If [k] = 0, then skip to step S505;

[0035] S505. Check if j ≤ I. If it does, add r to set R. root and R root1 In, that is, R root [i] = r, R root1 [j] = r, and at the same time let i = i+1, j = j+1, and jump to step S506; otherwise, jump directly to step S506.

[0036] S506. When i ≤ 2I, let r = r + 1 and jump to step S502; otherwise, end the selection and output R. root1 R root2 R root ;

[0037] Here, the function GCD(y1, y2) is used to find the greatest common divisor of the two numbers y1 and y2. (a) -1 This refers to an integer m that satisfies the condition m ∈ [1, N-1] and (m·a) mod N = 1. The resulting R... root1 R root2 That is, the set of root values ​​consisting of the long sequence root values ​​r1 and r2 that meet the requirements.

[0038] This invention also provides a method for detecting the receiver end of a 6G low-Earth orbit satellite random access signal transmission sequence based on ZC sequences, comprising the following steps:

[0039] S601. Initialize the set R of root values ​​r1 of the ZC sequence of initialization parameters. root1 R is the set of root values ​​r2 of a long ZC sequence. root2The short ZC sequence root value s = 1, the total number of random access sequences required I, the detection threshold T, the range of normalized integer frequency offset Φ = [-ε, ε] (ε is the maximum possible integer normalized frequency offset, normalized to the subcarrier spacing of random access), and the set of preamble sequence numbers of the detected random access preamble. Detection delay set of the detected random access preamble sequence Intermediate variable l = 1;

[0040] S602, Choose r1 = R root1 (l), to obtain the sequence The received signal {y(n), 0≤n≤N-1} is compared with... Performing cyclic correlation, that is The positions M where the two energy peaks are obtained 1主 and M 1副 That is, M 1主 =argmax m∈[0，N-1] E1(m), and the energy E at the corresponding location 1主 =E1(M 1主 ) and E 1副 =E1(M 1副 Proceed to step S603;

[0041] S603, Choose r2 = R root2 (l), to obtain the sequence The received signal {y(n), 0≤n≤N-1} is compared with... Performing cyclic correlation, that is The positions M where the two energy peaks are obtained 2主 and M 2副 That is, M 2主 =argmax m∈[0，N-1] E2(m), and the energy E at the corresponding location 2主 =E2(M 2主 ) and E 2副 =E2(M 2副 Proceed to step S604;

[0042] S604, Detection E 1主 +E 1副 +E 2主 +E 2副 If the threshold T is greater than 1, proceed to step S605; otherwise, it is considered that the l-th random access preamble sequence has not been detected, and jump to step S609.

[0043] S605, according to |M1主 -M1 副 The size of | determines the parameter M1;

[0044] S606, according to |M 2主 -M 2副 The value of 1 determines the parameter M2;

[0045] S607. Calculate the set of positional intervals ΔM based on the range of the normalized integer frequency offset Φ = [-ε, ε] and r1, r2. Φ ;

[0046] S608. Calculate the actual ΔM based on M1 and M2 determined in steps S605 and S606. 实际 = (M1-M2)modN, and check ΔM 实际 If ΔM 实际 In set ΔM Φ In the case of a random access preamble sequence, it is assumed that the l-th random access preamble sequence has been detected, and l is placed into set P, where P = P∪{l}. Then, according to ΔM... 实际 In set ΔM Φ The index number m in the table determines the estimate of the normalized integer frequency offset. According to the obtained Perform timing estimation Will Put into set D If ΔM 实际 Not in set ΔM Φ If the first random access preamble sequence is not detected, proceed to step S609.

[0047] S609, l = l + 1, and check l. If l is less than or equal to I, jump to step S602; otherwise, the detection ends and output set P and set D. At this time, set P contains the sequence number of the random access preamble signal detected by the base station, and set D contains the estimated time delay information corresponding to these detected random access signals.

[0048] As a preferred embodiment of the present invention, in step S605 when |M 1主 -M 1副 |=(r1+sK) -1 When, if M 1主 <M 1副 Let M1 = M 1主 Otherwise, let M1 = M 1副 When |M 1主 -M 1副 |=N-(r1+sK) -1 When, if M 1主 <M 1副 Let M1 = M1副 Otherwise, let M1 = M 1主 And when |M 1主 -M 1副 If | is any other, let M1 = M 1主 .

[0049] As a preferred embodiment of the present invention, in step S606 when |M 2主 -M 2副 |=(r2+sK) -1 When, if M 2主 <M 2副 Let M2 = M 2主 Otherwise, let M2 = M 2副 When |M 2主 -M 2副 |=N-(r2+sK) -1 When, if M 2主 <M 2副 Let M2 = M 2副 Otherwise, let M2 = M 2主 And when |M 2主 -M 2副 If | is otherwise, let M2 = M 2主 .

[0050] In a preferred embodiment of the present invention, step S607 specifically involves sequentially selecting the m-th (1≤m≤2ε+1) element Φ(m) from the set Φ, and calculating the corresponding timing position interval ΔM under the given frequency offset. 理论 =(Φ(m)·(r1+sK) -1 -Φ(m)·(r2+sK) -1 mod N, and ΔM 理论 Put into set ΔM Φ In, that is, ΔM Φ (m)=ΔM 理论 .

[0051] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0052] The random access signal designed in this invention not only meets the characteristics of wide coverage, large transmission delay, and a large number of access user terminal devices in satellite communication systems, but also effectively combats frequency offset and is suitable for scenarios where terminals are not stationary. Compared with the preamble design scheme in reference CN2022102755797 (which is only applicable to the case without frequency offset), it has a broader application prospect. Furthermore, this invention studies a root value optimization algorithm for generating specific preamble sequences. Simulation analysis results show that using the root value selected by the algorithm in this paper, the generated preamble generates less interference when correlated at the receiver.

[0053] Meanwhile, this invention provides a detection and timing algorithm for the receiver. This algorithm can estimate the normalized frequency offset as an integer multiple based on the designed random access signal, and further estimate the round-trip transmission delay based on this. Simulation verification shows that the random access signal and detection algorithm designed in this invention still have good detection performance in scenarios with large frequency offsets. Attached Figure Description

[0054] Figure 1 A flowchart for generating the set consisting of the root values ​​r1 and r2 of a long sequence;

[0055] Figure 2 Flowchart for the detection of random access signal transmission sequence at the receiver;

[0056] Figure 3 Plot of the normalized cross-correlation peak cumulative distribution function;

[0057] Figure 4 A diagram illustrating the false detection rate under different integer CFO values;

[0058] Figure 5 This diagram illustrates the false positive rate under different decimal CFO values. Detailed Implementation

[0059] The present invention will be further described below with reference to specific embodiments.

[0060] A method for generating random access signal transmission sequences for 6G low-Earth orbit satellites based on ZC sequences includes the following steps:

[0061] S1: Determine the maximum round-trip transmission delay difference between the ground terminal equipment and the low-Earth orbit satellite. Specifically, the steps include: S101: Obtaining the beam diameter d of the satellite communication system. cell And the Earth's radius D, based on the beam diameter d of the satellite communication system. cell Given the Earth's radius D, calculate the beam diameter d. cell Angle with Earth's radius D S102: Let the maximum transmission distance L be the distance between the satellite and the point on Earth where the satellite signal can reach the maximum range of the satellite. Let the angle between the line connecting the satellite and the point on Earth where the satellite signal can reach the maximum range of the satellite and the tangent line at that point be the minimum communication angle θ. Then, calculate the minimum distance from the edge of the cell covered by the satellite to the satellite based on the maximum transmission distance L and the minimum communication angle θ. S103: Calculate the maximum round-trip time delay difference based on the minimum distance d from the edge of the cell covered by the satellite to the satellite, the maximum transmission distance L, and the speed of light c.

[0062] S2: Based on the maximum round-trip transmission delay difference Determine the duration T of the cyclic prefix CP and the guard interval GT. CP T GT ,

[0063] S3: Determine the duration T of the random access preamble sequence (Sequence). Seq The process includes the following steps: S301: Obtain the noise density N0 and noise figure N of the random access channel. f PRACH signal target received power P RA The duration T of the physical layer random access preamble sequence in a 6G terrestrial cellular communication system. SS The random access signal sampling frequency f at the receiving end s False alarm probability p FA And the false negative probability p of the detection system MD S302: According to the formula Find the detection threshold 'a' and the detection window length. f s The sampling frequency of the randomly accessed signal at the receiving end, symbol This indicates rounding x up; S303: According to the formula Obtain the leader sequence energy to thermal noise ratio that meets the detection probability requirements. Where Q1 is the Markum function, S304: To meet coverage performance requirements, the duration of the preamble sequence is set... S305: Considering compatibility with the physical layer random access signal design scheme of terrestrial cellular communication systems, the preamble sequence duration T is set... Seq The duration T of the random access preamble sequence for a 6G terrestrial cellular communication system. SS K times, that is, T Seq =K×T SS K is an integer; S306: Considering the requirement of maximum round-trip transmission delay difference, let the duration of the preamble sequence be... S307: Based on S304, S305, and S306, obtain the smallest positive integer K such that the duration T of the preceding sequence is... Seq =K×T SS ,and and S308: Based on the obtained K and the length N of the short ZC sequence ZC The lengths of the first and second sequences, N = K × N, are obtained. ZC .

[0064] S4: Set the first sequence root value s such that the first sequence root value s is relatively prime to the short ZC sequence length N ZC and relatively prime;

[0065] S5: Obtain the set R composed of the second sequence root values r1 and r2 used for different random access preamble sequences root1 , R root2 , as Figure 1 shown, the set R composed of the second sequence long sequence root values r1 and r2 in S5 root1 (r1 ∈ R root1 ) and R root2 (r2 ∈ R root2 ) includes the following steps:

[0066] S501. Initialize the parameters N, K, N ZC , the number of random access preamble sequences to be provided is I, the first sequence root value s = 1, the set of long ZC sequence root values r1 the set of long ZC sequence root values r2 of R root2 [1:I] = 0, the set of all root values of the long ZC sequence and the intermediate variables t = 1, r = 1, i = 1, j = 1;

[0067] S502. Check the parameter r. If r < N, go to step S503, otherwise, initialize the parameters t = t + 1, r = 1,<00005​​​​​​​​​​​​​​​​​​​​​​​​​-1 -(R root1 [k]+Ks) -1 )mod N ZC ≠0 and R root2 If [k] = 0, and such a k can be found, for the first k that satisfies the condition, let R root2 [k] = r, and put r into set R. root In, that is, R root [i] = r, and let i = i + 1, then jump to step S506; if no such k can be found in the range k = 1 to k = j - 1 satisfying ((r + Ks) -1 -(R root1 [k]+Ks) -1 )modN ZC ≠0 and R root2 If [k] = 0, then skip to step S505;

[0070] S505. Check if j ≤ I. If it does, add r to set R. root and R root1 In, that is, R root [i] = r, R root1 [j] = r, and at the same time let i = i+1, j = j+1, and jump to step S506; otherwise, jump directly to step S506.

[0071] S506. When i ≤ 2I, let r = r + 1 and jump to step S502; otherwise, end the selection and output R. root1 R root2 R root ;

[0072] Here, the function GCD(y1, y2) is used to find the greatest common divisor of the two numbers y1 and y2. (a) -1 This refers to an integer m that satisfies the condition m ∈ [1, N-1] and (m·a) mod N = 1. The resulting R... root1 R root2 That is, the set of root values ​​consisting of the long sequence root values ​​r1 and r2 that meet the requirements.

[0073] The random access signal includes a cyclic prefix (CP), a preamble sequence, and a guard time (GT). The preamble sequence is obtained by multiplying corresponding elements of two sequences of length N. The mathematical expression for the access preamble sequence is as follows: The first sequence is a sequence with root value s and length N. ZC The length of the short ZC sequence obtained by repeating it K times is N (N = K·N). ZCThe sequence is given by N. The short sequences of different random access leader sequences are completely identical. The root value s of the first short sequence is set to s = 1, satisfying the condition that s and N... ZC Coprime;

[0074] The second sequence is the sum and multiplication of two ZC sequences of length N with root values ​​r1 and r2 respectively. The resulting sequence.

[0075] This invention also provides a method for detecting the receiver end of a 6G low-Earth orbit satellite random access signal transmission sequence based on ZC sequences, such as... Figure 2 As shown, it includes the following steps:

[0076] S601. Initialize the set R of root values ​​r1 of the ZC sequence of initialization parameters. root1 R is the set of root values ​​r2 of a long ZC sequence. root2 The short ZC sequence root value s = 1, the total number of random access sequences required I, the detection threshold T, the range of normalized integer frequency offset Φ = [-ε, ε] (ε is the maximum possible integer normalized frequency offset, normalized to the subcarrier spacing of random access), and the set of preamble sequence numbers of the detected random access preamble. Detection delay set of the detected random access preamble sequence Intermediate variable l = 1;

[0077] S602, Choose r1 = R root1 (l), to obtain the sequence The received signal {y(n), 0≤n≤N-1} is compared with... Performing cyclic correlation, that is The positions M where the two energy peaks are obtained 1主 and M 1副 That is, M 1主 =arg max m∈[0，N-1] E1(m), and the energy E at the corresponding location 1主 =E1(M 1主 ) and E 1副 =E1(M 1副 Proceed to step S603;

[0078] S603, Choose r2 = R root2 (l), to obtain the sequence The received signal {y(n), 0≤n≤N-1} is compared with... Performing cyclic correlation, that is The positions M where the two energy peaks are obtained 2主 and M 2副 That is, M2主 =argmax m∈[0，N-1] E2(m), and the energy E at the corresponding location 2主 =E2(M 2主 ) and E 2副 =E2(M 2副 Proceed to step S604;

[0079] S604, Detection E 1主 +E 1副 +E 2主 +E 2副 If the threshold T is greater than 1, proceed to step S605; otherwise, it is considered that the l-th random access preamble sequence has not been detected, and jump to step S609.

[0080] S605, according to |M 1主 -M 1副 The size of | determines the parameter M1, when |M 1主 -M 1副 |=(r1+sK) -1 When, if M 1主 <M 1副 Let M1 = M 1主 Otherwise, let M1 = M 1副 When |M 1主 -M 1副 |=N-(r1+sK) -1 When, if M 1主 <M 1副 Let M1 = M 1副 Otherwise, let M1 = M 1主 And when |M 1主 -M 1副 If | is any other, let M1 = M 1主 ;

[0081] S606, according to |M 2主 -M 2副 The size of | determines the parameter M2, when |M 2主 -M 2副 |=(r2+sK) -1 When, if M 2主 <M 2副 Let M2 = M 2主 Otherwise, let M2 = M 2副 When |M 2主 -M 2副 |=N-(r2+sK) -1 When, if M 2主 <M 2副 Let M2 = M 2副 Otherwise, let M2 = M 2主And when |M 2主 -M 2副 If | is otherwise, let M2 = M 2主 ;

[0082] S607. Calculate the set of positional intervals ΔM based on the range of the normalized integer frequency offset Φ = [-ε, ε] and r1, r2. Φ Specifically, the m-th (1≤m≤2ε+1) element Φ(m) in the set Φ is selected sequentially, and the corresponding timing position interval ΔM under this frequency offset is calculated. 理论 =(Φ(m)·(r1+sK) -1 -Φ(m)·(r2+sK) -1 mod N, and ΔM 理论 Put into set ΔM Φ In, that is, ΔM Φ (m)=ΔM 理论 ;

[0083] S608. Calculate the actual ΔM based on M1 and M2 determined in steps S605 and S606. 实际 = (M1-M2)modN, and check ΔM 实际 If ΔM 实际 In set ΔM Φ In the case of a random access preamble sequence, it is assumed that the l-th random access preamble sequence has been detected, and l is placed into set P, where P = P∪{l}. Then, according to ΔM... 实际 In set ΔM Φ The index number m in the table determines the estimate of the normalized integer frequency offset. According to the obtained Perform timing estimation Will Put into set D If ΔM 实际 Not in set ΔM Φ If the first random access preamble sequence is not detected, proceed to step S609.

[0084] S609, l = l + 1, and check l. If l is less than I, jump to step S602; otherwise, the check ends and output set P and set D.

[0085] The set P obtained at this time contains the sequence number of the random access preamble signal detected by the base station, and the set D contains the estimated time delay information corresponding to these detected random access signals.

[0086] A typical LEO communication system—the Iridium system—has the following system parameters:

[0087] Table 1. Iridium Satellite System Parameters

[0088]

[0089]

[0090] 1. Following the calculation process in step 2, T can be obtained. Sea =6.4ms, K=8, N=K*N ZC =8*839=6712.

[0091] 2. Set the number of users in the sector to I = 64. According to step S5, we finally obtain t = 8, and the root value set R. root1 and R root2 They are: R root1 ={1, 5, 9, 13, 17, 21, 25, 29, 33, 37, 41, 45, 49, 53, 57, 61, 65, 69, 73, 77, 81, 85, 89, 93, 97, 101, 105, 109, 113, 117, 121, 125, 129, 133, 137, 141, 145, 149, 153, 157, 161, 165, 169, 173, 177, 181, 185, 189, 193, 197, 201, 205, 209, 213, 217, 221, 225, 229, 233, 237, 241, 245, 249, 253};

[0092] R root2 ={3, 7, 11, 15, 19, 23, 27, 31, 35, 39, 43, 47, 51, 55, 59, 63, 67, 71, 75, 79, 83, 87, 91, 95, 99, 103, 107, 111, 115, 119, 123, 127, 131, 135, 139, 143, 147, 151, 155, 159, 163, 167, 171, 175, 179, 183, 187, 191, 195, 199, 203, 207, 211, 215, 219, 223, 227, 231, 235, 239, 243, 247, 251, 255}.

[0093] 3. Changing I = 128 gives t = 8, and the root set R root1 and R root2 They are respectively:

[0094] R root1＝{1，5，9，13，17，21，25，29，33，37，41，45，49，53，57，61，65，69，73，77，81，85，89，93，97，101，105，109，113，117，121，125，129，133，137，141，145，149，153，157，161，165，169，173，177，181，185，189，193，197，201，205，209，213，217，221，225，229，233，237，241，245，249，253，257，261，265，269，273，277，281，285，289,293,297,301，305,309,313,317,321,325，329，333，337，341，345，349，353,357,361，365，369，373，377，381，385，389，393,397,401，405,409，413,417,421，425，429，433，437，441，445，449，453，457，461，465，469，473，477，481，485，489，493，497，501，505，509}；

[0095] R root2={3, 7, 11, 15, 19, 23, 27, 31, 35, 39, 43, 47, 51, 55, 59, 63, 67, 71, 75, 79, 83, 87, 91, 95, 99, 103, 107, 111, 115, 119, 123, 127, 131, 135, 139, 143, 147, 151, 155, 159, 163, 167, 171, 175, 179, 183, 187, 191, 195, 199, 203, 207, 211, 215, 219, 223, 227, 231, 235, 239, 243, 247, 251, 255, 259, 263, 267, 2 71,275,279,283,287,291,295,299,303,307,311,315,319,323,327,331,335,339,343,347,351,355,359,363,367,371,375,379,383,387,391,395,399,403,407,411,415,419,423,427,431,435,439,443,447,451,455,459,463,467,471,475,479,483,487,491,495,499,503,507,511}.

[0096] The union R of the root values ​​of a long sequence root =R root1 ∪R root2 Choose any pair of elements and calculate the sequence {x} they form. s，r , r∈R root The normalized cross-correlation results are shown below. The peak cumulative distribution function of the normalized cross-correlation is plotted as follows. Figure 3 As shown.

[0097] from Figure 3 As can be seen, when I is 64 and 128 respectively, the peak value of the normalized cross-correlation is approximately 50%. Much smaller than the autocorrelation peak value, and the maximum cross-correlation peak value is [missing value]. This indicates that using the long ZC sequence root value obtained by the long ZC sequence root value selection algorithm designed in this invention to generate the preamble will greatly reduce the probability of large cross-correlation interference during the correlation calculation at the receiver, and will not affect the performance of the receiver's TA timing detection.

[0098] Figure 4The normalized carrier frequency offset (CFO) is CFO=1 and CFO=7. As can be seen from the figure, the timing detection performance of the transceiver design of this invention does not significantly decrease in the presence of integer CFO. This is because integer CFO does not cause signal energy leakage in the design of this invention. Therefore, the accurate correlation peak position can be obtained at the receiver. The frequency offset can be estimated using two correlation peak positions. The timing can be accurately completed even at a low SNR, which is superior.

[0099] Figure 5 The normalized CFO values ​​are CFO = 1.2 and CFO = 1.5. As shown in the figure, even in scenarios with a decimal CFO, the timing detection algorithm designed in this invention suffers minimal performance loss and still maintains a low false detection rate. This is because the invention employs energy superposition at the receiving end, superimposing leaked energy onto the main peak of the relevant calculations, thereby improving detection accuracy. Especially when the decimal CFO is 0.5, it still exhibits excellent performance.

[0100] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the invention.

Claims

1. A method for generating a random access signal transmission sequence for a 6G low-Earth orbit satellite based on the ZC sequence, wherein the random access signal includes a cyclic prefix, a preamble sequence, and a guard interval, characterized in that... The leader sequence consists of two sequences of length [missing information]. N The sequence is obtained by multiplying corresponding elements of the sequence. The mathematical expression of the leading sequence is as follows: The root value of the first sequence is s , length is Short ZC sequence repeats K The length obtained after this is ( The sequences are identical for all short sequences of different random access leader sequences; the root values ​​of the second sequence are respectively and The two lengths are N Adding and multiplying the ZC sequences The obtained sequence, the root value of the first sequence s With the length of short ZC sequences Coprime; The root value of the second sequence in S5 and The set ( )and ( This includes the following steps: S501, Initialization Parameters , , The number of random access preamble sequences required is The root value of the first sequence , root value of long ZC sequence set Root value of long ZC sequence set The set of all root values ​​of a long ZC sequence and intermediate variables , , , ; S502, Check parameters ,if Proceed to step S503; otherwise, initialize parameters. and return to step S502; S503, Inspection Whether or not coprime and Whether or not Coprime; for those satisfying both requirements Proceed to step S504, otherwise let Skip to step S502; S504, if ,Will Add to collection and In, that is , At the same time, Skip to step S506; if ,examine and any root value element in Does it meet the requirements? For example, for a certain root element Not satisfied Then let Skip to step S502, otherwise (i.e., for all) They all ), then in arrive Check each item within the specified range to see if you can find it. Make as well as If we can find such For the first one that meets the conditions ,make and will Add to collection In, that is and order Skip to step S506; if in arrive The range cannot find such a satisfy as well as Then proceed to step S505; S505, Check if it is satisfied. If satisfied, Add to collection and In, that is , At the same time, If the condition is met, proceed to step S506; otherwise, proceed directly to step S506. S506, when season If the selection fails, proceed to step S502; otherwise, end the selection and output the result. , , ; Here, function Used to find these two numbers and The greatest common divisor, It refers to satisfying Within the range and satisfy mod Integers that are equal to 1 At this point, we get That is, the root value of the long sequence that meets the requirements. and The set of root values ​​formed by this.

2. The method for generating a 6G low-Earth orbit satellite random access signal transmission sequence based on ZC sequence according to claim 1, characterized in that, Specifically, the parameters of the preceding sequence (Sequence) are obtained through the following steps: S1: Determine the maximum round-trip transmission delay difference between the ground terminal equipment and the low-Earth orbit satellite. ; S2: Based on the maximum round-trip transmission delay difference Determine the duration T of the cyclic prefix CP and the protection interval GT. CP T GT T CP = T GT = ; S3: Determine the duration of the random access preamble sequence (Sequence). T Seq and the length of the preceding sequence N ; S4: Set the root value of the first sequence s , so that the root value of the first sequence s With the length of the short ZC sequence Coprime; S5: Obtain the root value of the second sequence used for different random access leader sequences. and The set .

3. The method for generating a 6G low-Earth orbit satellite random access signal transmission sequence based on ZC sequence according to claim 2, characterized in that, Step S1 calculates the maximum round-trip transmission delay difference based on the parameters and coverage area of ​​the LEO satellite system. The specific method is as follows: S101: Obtain the beam diameter of the satellite communication system d cell and Earth's radius D According to the beam diameter of the satellite communication system d cell and the Earth's radius D Calculate the beam diameter d cell With Earth's radius D The included angle ; S102: Let the distance between the points on Earth where satellite signals can reach the maximum range of the Earth be defined as the maximum transmission distance. L Let the angle between the line connecting the satellite and the point on Earth where the satellite signal can reach the maximum range of the Earth, and the tangent line at that point be the minimum communication angle. θ Then, based on the maximum transmission distance L and the minimum communication angle θ Calculate the minimum distance from the edge of the cell covered by the satellite to the satellite. ; S103: Based on the minimum distance from the edge of the cell covered by the satellite to the satellite. d The maximum transmission distance L and the speed of light c The maximum round-trip transmission delay difference is calculated. .

4. The method for generating a 6G low-Earth orbit satellite random access signal transmission sequence based on ZC sequence according to claim 2, characterized in that, Step S3 specifically includes the following steps: S301: Obtain the noise density of the random access channel N 0. Noise figure N f PRACH signal target received power P RA 6G terrestrial cellular communication system physical layer random access preamble sequence duration T SS Random access signal sampling frequency at the receiving end f s False alarm probability and the probability of missed detection in the detection system ; S302: According to the formula Find the detection threshold Detection window length The sampling frequency of the randomly accessed signal at the receiving end, symbol Indicates to Round up; S303: According to the formula The energy-to-thermal-noise ratio of the leader sequence that meets the detection probability requirements is obtained. ,in, For Markum functions, ; S304: To meet coverage performance requirements, the duration of the preamble sequence is set to... ; S305: Considering compatibility with the physical layer random access signal design scheme of terrestrial cellular communication systems, the duration of the preamble sequence is set to... Duration of the random access preamble sequence for 6G terrestrial cellular communication systems of K times, that is , K It is an integer; S306: Considering the requirement of maximum round-trip transmission delay difference, the duration of the preamble sequence is set as follows: ; S307: Based on S304, S305, and S306, obtain the smallest positive integer. K The duration of the preceding sequence is thus determined. ,and ,and ; S308: Based on the obtained K and the length of the short ZC sequence Find the lengths of the first and second sequences. .

5. The method for generating a 6G low-Earth orbit satellite random access signal transmission sequence based on ZC sequence according to claim 2, characterized in that, Step S4 includes determining , and In the case of the first sequence short sequence root value Set as The conditions are met. and Coprime.

6. A method for detecting the receiver end of a 6G low-Earth orbit satellite random access signal transmission sequence based on ZC sequences, characterized in that, Includes the following steps: S601, Initialize the root value of the long ZC sequence parameter. set Root value of long ZC sequence set Root value of short ZC sequence s= The total number of random access sequences required Detection threshold The range of normalized integer frequency offset ( The set of detected random access preamble sequence numbers (the largest possible integer normalized frequency offset, normalized to the subcarrier spacing of random access). The set of detection delays for the detected random access preamble sequence D intermediate variables l ; S602, Select , to obtain the sequence , will receive signal and Performing cyclic correlation, that is = To obtain the locations of the two peaks with the highest energy. and , that is , and the energy at the corresponding location. and Proceed to step S603; S603, Select , to obtain the sequence , will receive signal and Performing cyclic correlation, that is = To obtain the locations of the two peaks with the highest energy. and , that is , and the energy at the corresponding location. and Proceed to step S604; S604, Testing If it is greater than the threshold Proceed to step S605; otherwise, consider the first step as... If no random access preamble sequence is detected, proceed to step S609. S605, according to The size is used to select and determine the parameters. ; S606, according to The size is used to select and determine the parameters. ; S607, Based on the range of normalized integer frequency offset and Calculate the set of position intervals ; S608, Based on the determination in steps S605 and S606 and Calculate the actual and check ,if In the set In the middle, it is believed that the first A random access preamble sequence was detected, Add to collection , ,according to In the set Index number in Determine the estimate of the normalized integer frequency offset According to the obtained Perform timing estimation ,Will Add to collection middle, ; if Not in the set In the middle, it is considered that the first one was not detected. A random access leader sequence is generated, and the process proceeds to step S609. S609 and check ,if Less than or equal to If the test ends, proceed to step S602; otherwise, the test ends and the set is output. and set D The set obtained at this time It contains the sequence number of the random access preamble signal detected by the base station, and the set. D It contains the estimated time delay information corresponding to these detected random access signals.

7. The method for detecting the receiver end of a 6G low-Earth orbit satellite random access signal transmission sequence based on ZC sequence according to claim 6, characterized in that, In step S605 when At that time, if ,make Otherwise ,when At that time, if ,make Otherwise , and when For other cases, let .

8. The method for detecting the receiver end of a 6G low-Earth orbit satellite random access signal transmission sequence based on ZC sequence according to claim 6, characterized in that, In step S606 when At that time, if ,make Otherwise ,when At that time, if ,make Otherwise , and when For other cases, let .

9. The method for detecting the receiver end of a 6G low-Earth orbit satellite random access signal transmission sequence based on ZC sequence according to claim 6, characterized in that, Specifically, in step S607, sets are selected sequentially. The first in element Calculate the corresponding timing position interval under this frequency offset. and will Add to collection In, that is .

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