Chaotic sequence-based low-orbit satellite communication synchronous broadcast channel design method

Abstract

The invention provides a low-orbit satellite communication synchronous broadcast channel design method based on a chaos sequence, and belongs to an anti-interference enhancement technology in the field of satellite communication. The method comprises the following steps: constructing a second-order improved Logistic mapping function; chaotic data Q1, Q2 and Q3 are generated; performing binary quantization on the chaotic data Q1, Q2 and Q3; respectively cutting off the binary quantized chaotic data Q1, Q2 and Q3 to form chaotic sequences S1, S2 and S3; in each 1ms subframe, filling each SSB (Secure Socket Block), and constructing a synchronous broadcast burst set of each subframe; in each 10ms frame, 10 1ms subframes contained in the 10ms frame are filled, and a synchronous broadcast channel of each frame is formed. According to the invention, the anti-interception and anti-interference capabilities of a synchronous broadcast channel can be effectively improved, and the anti-interference capability of an existing 5G NTN physical layer transmission system is improved, so that the reliability of a satellite-ground communication link is improved.

Description

Technical Field

[0001] The present invention relates to an anti-interference enhancement technology in the field of satellite communications, and in particular to a design method for a low-orbit satellite communication synchronous broadcast channel based on a chaotic sequence. Background Art

[0002] With the rapid convergence of heterogeneous satellite and ground networks, information exchange between terrestrial mobile cellular networks, low-orbit satellite internet, and traditional high-orbit satellite systems is becoming increasingly frequent, leading to increasing challenges such as resource collisions and spectrum conflicts. Currently, the downlink synchronous broadcast channels of low-orbit satellite communications based on the 5GNTN architecture are highly susceptible to intentional or unintentional co-channel interference, preventing ground terminals from correctly acquiring important parameters such as operating frequency and system bandwidth, leading to network access failures.

[0003] Anti-interference enhancement technology is crucial for improving the reliability of satellite-to-ground communication links. Traditional frequency-hopping satellite communication systems are well-suited for single-carrier systems with a fixed central operating frequency, offering significant frequency-hopping gain. However, for multi-carrier Orthogonal Frequency Division Multiplexing (OFDM) systems, the start and end times of frequency hopping and the complex frequency synchronization require changes to the existing OFDM-based physical layer transmission system, severely restricting its application in 5G NTNs. Summary of the Invention

[0004] The purpose of this invention is to propose a design method for low-orbit satellite communication synchronous broadcast channel based on chaotic sequence to address the problem that the existing 5G NTN synchronous broadcast channel is extremely susceptible to intentional or unintentional co-channel interference.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for designing a low-orbit satellite communication synchronous broadcast channel based on a chaotic sequence comprises the following steps:

[0007] Step 1: Construct a second-order improved Logistics mapping function;

[0008] Step 2: Based on the second-order improved Logistics mapping function, generate chaotic data Q1 with an initial value of 0.2, chaotic data Q2 with an initial value of 0.3, and chaotic data Q3 with an initial value of 0.4;

[0009] Step 3, perform binary quantization on chaotic data Q1, Q2, and Q3;

[0010] Step 4: truncate the binary quantized chaotic data Q1, Q2, and Q3 respectively to form chaotic sequences S1 and S2 with a length of 127 bits, and a chaotic sequence S3 with a length of 240 bits;

[0011] Step 5: In each 1ms subframe, within the {4th, 8th, 16th, 20th}+28nth symbols in the time domain, where n = 0, 1, 2, 3, fill each SSB to construct a synchronized broadcast burst set for each subframe; wherein the first, third, and fourth symbols in the SSB are filled based on the chaotic sequences S1, S2, and S3, respectively;

[0012] Step 6: In each 10ms frame, fill the 10 1ms subframes contained therein according to step 5 to form a synchronous broadcast channel for each frame.

[0013] Furthermore, the second-order improved Logistics mapping function is expressed as:

[0014]

[0015] Among them, x n Indicates the calculated value. When n=1, x1 indicates the initial value, x n+1 represents the mapping value, μ represents the mapping parameter; x n That is the nth chaotic data.

[0016] Furthermore, in step 4, the binary quantization criteria are as follows:

[0017]

[0018] Among them, y n+1 represents the n+1th chaotic data after quantization, x n+1 Represents the original (n+1)th chaotic data.

[0019] Furthermore, in step 5, the specific method of filling each SSB is as follows:

[0020] Step 501: Fill the middle 127 subcarriers of the first symbol in the SSB with S1, fill the middle 127 subcarriers of the third symbol in the SSB with S2, and fill the remaining subcarriers in the first and third symbols in the SSB with 0;

[0021] Step 502: Payload padding is performed on the second symbol in the SSB according to the PBCH specified in the 3GPP TS38.211 standard.

[0022] Step 503: Use the chaotic sequence S3 to spread the original sequence of the fourth symbol in the SSB to obtain spread data; the spreading method is:

[0023] S seq =S ori ×S3

[0024] Among them, Sori represents the original sequence of the fourth symbol, S seq represents the data after spread spectrum, and × represents multiplying the numbers in the same position of the two sequences;

[0025] Step 504: Fill the fourth symbol in the SSB with the spread spectrum data S seq .

[0026] The advantages of the present invention compared to the background technology are:

[0027] 1. The present invention designs a two-dimensional improved Logistics mapping function, which can obtain a larger full mapping range and generate a binary chaotic sequence with stronger randomness compared with the traditional Logistics mapping.

[0028] 2. The present invention innovatively hides the physical broadcast channel data obtained through chaotic sequence spread spectrum modulation in the synchronous broadcast block, thereby improving the anti-detection capability of the synchronous broadcast signal. In addition, the present invention can reduce the complexity of resource demapping through long sequence truncation operation.

[0029] 3. By combining the current 3GPP 5G NTN standard, the present invention can adapt to the physical layer transmission system of existing low-orbit satellite communications to the greatest extent possible, with minimal hardware changes. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the usage scenario of the present invention.

[0031] Figure 2 It is a flow chart of the present invention.

[0032] Figure 3 This is a schematic diagram of the synchronous broadcast channel designed by the present invention. DETAILED DESCRIPTION

[0033] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0034] A chaotic sequence-based low-orbit satellite communication synchronous broadcast channel design method is proposed. The method is applicable to the satellite-to-ground downlink of the low-orbit satellite communication network. Figure 1 This is its usage scenario, in which the ground terminal first receives the downlink synchronization signal before receiving the service signal. The synchronization signals transmitted by low-orbit satellites at different times will be received by different ground terminal receivers in a time-sharing manner.

[0035] This method is implemented based on the existing 5G NTN physical layer transmission system. Figure 2 , the specific steps are as follows:

[0036] S1, constructs the second-order improved Logistics mapping function, expressed as:

[0037]

[0038] Among them, x n represents the calculated value (when n=1, x1 represents the initial value), x n+1 represents the mapping value; μ represents the mapping parameter.

[0039] S2, set the threshold value T = 0, and set three initial values: a1 = 0.2, b1 = 0.3, c1 = 0.4.

[0040] S3, using the second-order improved Logistics mapping function and three initial values, generates chaotic data Q1 with an initial value of a1, chaotic data Q2 with an initial value of b1, and chaotic data Q3 with an initial value of c1.

[0041] S4, respectively, performs binary quantization on the three sets of chaotic data Q1, Q2 and Q3. The quantization criteria are as follows:

[0042]

[0043] Among them, y n+1 Represents quantized chaotic data.

[0044] S5, set the truncation bit number D1 = 127, truncate the binary quantized Q1 and Q2 to form chaotic sequences S1 and S2 with a length of 127 bits; set the truncation bit number D2 = 240, truncate the binary quantized Q3 to form a chaotic sequence S3 with a length of 240 bits.

[0045] S6: Fill the middle 127 subcarriers of the first symbol in each SSB with the S1 sequence, and fill the middle 127 subcarriers of the third symbol in each SSB with the S2 sequence. The remaining subcarriers in the first and third symbols are filled with 0s. The corresponding relationship between the subcarriers and the filling of chaotic sequences S1 and S2 is shown in Table 1 and Table 2 respectively:

[0046] Table 1 Correspondence between chaotic sequence S1 and subcarriers

[0047] subcarrier 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Filling number 0 1 1 1 1 1 0 0 0 1 1 1 1 0 1 0 subcarrier 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 Filling number 0 1 1 1 1 1 1 1 0 1 1 0 1 0 0 0 subcarrier 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 Filling number 1 1 0 1 1 1 0 0 1 0 1 1 1 0 1 1 subcarrier 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 Filling number 1 0 0 1 1 0 1 0 1 1 0 0 0 0 0 0 subcarrier 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 Filling number 0 1 1 0 1 0 0 1 1 0 1 0 0 1 1 0 subcarrier 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 Filling number 1 0 0 1 0 1 0 1 1 1 1 0 1 1 0 0 subcarrier 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 Filling number 1 1 1 1 0 1 1 0 1 1 0 1 0 1 1 0 subcarrier 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 Filling number 0 1 1 0 0 0 0 1 1 1 0 0 1 1 1

[0048] Table 2 Correspondence between chaotic sequence S2 and subcarriers

[0049]

[0050]

[0051] S7, according to the PBCH specified in the 3GPP TS38.211 standard, the second symbol in the SSB is filled with payload.

[0052] S8, use sequence S3 to spread the fourth symbol in SSB, the spreading method is as follows:

[0053] S seq =S ori ×S3

[0054] Among them, S ori The original sequence of the fourth symbol in SSB, S seq Represents the filling data after spreading by chaotic sequence S3.

[0055] S9: Fill the fourth symbol in each SSB with data spread by sequence S3. The corresponding relationship between the subcarriers and the filling sequence S3 is shown in Table 3 below:

[0056] Table 3 Correspondence between chaotic sequence S3 and subcarriers

[0057]

[0058]

[0059] S10 , in each 1 ms subframe, in the {4, 8, 16, 20}+28nth symbols in the time domain, where n=0, 1, 2, 3, repeat steps S6 to S9 to construct a synchronized broadcast burst set for each subframe.

[0060] S11, in each 10ms frame, the 10 1ms subframes contained therein are filled in accordance with the method of step S10 to form a synchronous broadcast channel of each frame, such as Figure 3 shown.

[0061] After completing the above steps, the design of low-orbit satellite communication synchronous broadcast channel based on chaotic sequence is completed.

[0062] The two-dimensional improved Logistics mapping function designed by the present invention generates a chaotic sequence. Compared with the traditional Logistics mapping, the two-dimensional improved Logistics mapping function has a larger full mapping range and the generated binary chaotic sequence has stronger randomness.

[0063] The present invention operates at the physical layer, using a generated 127-bit chaotic sequence with different initial values to fill the primary and secondary synchronization signals of the Synchronization Signal Block (SSB) in the 5GNTN (5th Generation Non-terrestrial Network), improving the anti-interference capability of the downlink synchronization signal. Furthermore, combined with the generated 240-bit chaotic sequence, a physical broadcast channel (PBCH) in the SSB is spread-spectrum modulated, allowing data with center frequency information to be hidden within another PBCH data that has not been spread-spectrum modulated. This further enhances the anti-detection capability of the low-orbit communication satellite downlink without changing the existing 5G NTN standard physical layer design.

[0064] The present invention is based on the current physical layer communication standard of 3GPP (3rd Generation Partnership Project) 5G NTN. The newly constructed synchronous broadcast channel can seamlessly adapt to the physical layer downlink transmission system of existing low-orbit satellite communications.

[0065] In summary, the present invention hides the physical broadcast channel data obtained through chaotic sequence spread spectrum modulation in the synchronous broadcast block, and improves the anti-detection capability of the synchronous broadcast signal without changing the existing 5G NTN standard physical layer design. The long sequence truncation operation can also reduce the complexity of resource mapping, minimize hardware changes, and to a certain extent solve the problem that the downlink synchronization signal of the low-orbit communication satellite is easily interfered with, and has certain engineering practice value. In a low-orbit satellite communication network with a complex electromagnetic environment and frequent air-ground link interactions, the use of this method can effectively improve the anti-detection and anti-interference capabilities of the synchronous broadcast channel, improve the anti-interference capability of the existing 5GNTN physical layer transmission system, and thus improve the reliability of the satellite-to-ground communication link.

Claims

1. A method for designing a low-orbit satellite communication synchronous broadcast channel based on chaotic sequences, characterized in that: The following steps are involved: Step 1: Construct a second-order improved Logistics mapping function; Step 2: Based on the second-order improved Logistics mapping function, generate chaotic data Q1 with an initial value of 0.2, chaotic data Q2 with an initial value of 0.3, and chaotic data Q3 with an initial value of 0.4; Step 3, perform binary quantization on chaotic data Q1, Q2, and Q3; Step 4: truncate the binary quantized chaotic data Q1, Q2, and Q3 respectively to form chaotic sequences S1 and S2 with a length of 127 bits, and a chaotic sequence S3 with a length of 240 bits; Step 5: In each 1ms subframe, within the {4th, 8th, 16th, 20th}+28nth symbols in the time domain, where n = 0, 1, 2, 3, fill each SSB to construct a synchronized broadcast burst set for each subframe; wherein the first, third, and fourth symbols in the SSB are filled based on the chaotic sequences S1, S2, and S3, respectively; Step 6: In each 10ms frame, fill the 10 1ms subframes contained therein according to step 5 to form a synchronous broadcast channel for each frame.

2. The method for designing a LEO satellite communication synchronous broadcast channel based on chaotic sequence according to claim 1, characterized in that: The second-order improved Logistics mapping function is expressed as: Among them, x n Indicates the calculated value. When n=1, x1 indicates the initial value, x n+1 represents the mapping value, μ represents the mapping parameter; x n That is the nth chaotic data.

3. The method for designing a LEO satellite communication synchronous broadcast channel based on chaotic sequence according to claim 1, characterized in that: In step 4, the binary quantization criteria are as follows: Among them, y n+1 represents the n+1th chaotic data after quantization, x n+1 Represents the original (n+1)th chaotic data.

4. The method for designing a low-orbit satellite communication synchronous broadcast channel based on chaotic sequence according to claim 1, characterized in that: In step 5, the specific method for filling each SSB is: Step 501: Fill the middle 127 subcarriers of the first symbol in the SSB with S1, fill the middle 127 subcarriers of the third symbol in the SSB with S2, and fill the remaining subcarriers in the first and third symbols in the SSB with 0; Step 502: Payload padding is performed on the second symbol in the SSB according to the PBCH specified in the 3GPP TS38.211 standard. Step 503: Use the chaotic sequence S3 to spread the original sequence of the fourth symbol in the SSB to obtain spread data; the spreading method is: S seq =S ori ×S3 Among them, S ori represents the original sequence of the fourth symbol, S seq represents the data after spread spectrum, and × represents multiplying the numbers in the same position of the two sequences; Step 504: Fill the fourth symbol in the SSB with the spread spectrum data S seq .

Images