A Novel Method for Constructing a Protocol Sequence Set for Unauthorized Access

Abstract

The present invention discloses a method for constructing a new protocol sequence set for license-free access, which includes constructing a primary new sequence set based on any sequence of the CRT sequence set, selecting the primary new sequences in the primary new sequence set with the smallest sum of the maximum Hamming cross-correlations with other sequences to form an alternative new sequence set, selecting the sequence with the lowest uniformity in the alternative new sequence set to replace the current sequence, and constructing a new protocol sequence set that meets the target code weight requirement in an iterative manner based on the above process. The present invention can construct a new protocol sequence set with a higher code weight, a lower Hamming cross-correlation, and a lower sequence uniformity for any total number of devices, and can provide each device with a reasonable number of transmission opportunities that are evenly distributed, thereby reducing the average delay and having better delay performance compared to other license-free access schemes.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless network communication, and specifically relates to a method for constructing a new protocol sequence set for license-free access. Background Art

[0002] With the rapid development of information technology, a new generation of network based on and extended from the Internet, namely the Internet of Things (IoT), has emerged. Many IoT application scenarios require each data packet to be transmitted with high reliability within a strict transmission time limit. Therefore, it is particularly important to design a transmission strategy with excellent performance under time limit constraints. Massey and Mathys proposed a protocol sequence set in 1985 to ensure high-reliability transmission without feedback. Wong proposed the UI property with the design goal of minimizing the maximum delay in 2007, which can ensure both the reliability and timeliness of transmission. Shum et al. constructed a CRT sequence set with the UI property in 2010, and Zhang et al. constructed a CRTm sequence set with higher code weight and the UI property in 2019. Nevertheless, previous work has focused on how to construct a UI sequence set with the shortest possible sequence period to minimize the maximum delay, while lacking optimization of the code weight and sequence structure to reduce the average delay. The present invention aims to provide a method for constructing a new protocol sequence for license-free access. The constructed protocol sequence has a high code weight, a low Hamming cross-correlation, and a low sequence uniformity, and can provide each device with a reasonable number and evenly distributed transmission opportunities, thereby reducing the average delay and having better delay performance compared to other license-free access schemes. Summary of the Invention

[0003] The present invention aims to provide a method for constructing a new protocol sequence set for license-free access, which can provide more and more evenly distributed transmission opportunities for each device and reduce the average delay, and has better delay performance compared to other access protocols. The technical solution for achieving the object of the present invention is: a method for constructing a new protocol sequence set for license-free access, and the specific steps are as follows:

[0004] Step 1: Given the number of devices M, define p M as the smallest prime number not less than M, and set the currently constructed sequence set U as a binary CRT sequence set U with a period length L = p M (2M - 1). Set the target code weight value as N = 2M, and set i = 1;

[0005] Step 2: Obtain the code weight w i of the current U sequence S i . If w i < N, then enter Step 3; otherwise, the sequence construction ends;

[0006] Step 3: Respectively, for the sequence S iSet the 0th position in it to 1 to obtain L-w i A number of primary selected new sequences S i ', define the maximum Hamming cross-correlation as the maximum value of the number of positions where two sequences simultaneously take the value of 1 under any cyclic shift, and select several candidate new sequences S with the smallest sum of the maximum Hamming cross-correlations with other sequences in the current U i outside to form an alternative set C i '; i ;

[0007] Step 4: Define the uniformity of a sequence as the sum of the squares of the distances between adjacent positions where the value is 1 in this sequence, and randomly select a sequence with the smallest uniformity in C i to replace the sequence S of the current U i , generating a new U;

[0008] Step 5: If i < M, set i = i + 1 and return to Step 2, otherwise set i = 1 and return to Step 2. Description of the Drawings

[0009] Figure 1 It is a flowchart of the method for constructing a new protocol sequence set of the present invention.

[0010] Figure 2 It is a comparison of the average delay of three license-free transmission strategies in Example 1 under different numbers of devices M. Detailed Embodiment

[0011] The present invention constructs a new protocol sequence set for license-free access. As Figure 1 shown, the specific implementation process includes:

[0012] Step 1: Given the number of devices M, define p M as the smallest prime number not less than M, and set the currently constructed sequence set U as a 0, 1 binary CRT sequence set U with a period length L = p M (2M - 1). Set the target code weight value as N = 2M, and set i = 1.

[0013] Step 1-1: Given the number of devices M, find the smallest prime number p not less than the number of devices M M , and set the sequence period as L = p M (2M - 1);

[0014] Step 1-2: Define the set of any positive integer modulo n as Z n = {0, 1, 2,..., n - 1};

[0015] Step 1-3: According to the Chinese Remainder Theorem, define the mapping relationship:

[0016]

[0017] To make a one - dimensional sequence correspond one - to - one with a two - dimensional matrix, define:

[0018]

[0019] According to the above formula, obtain the sequence feature set I g as:

[0020]

[0021] where g is an arbitrary integer from 1 to p M The sequence feature set I g represents the positions of 1s in the sequence S g in the CRT sequence set.

[0022] Step 2: Obtain the code weight w i of the current U - sequence S i , if w i < N, then go to Step 3, otherwise the sequence construction ends.

[0023] Step 3: Set the 0 positions in the sequence S i to 1 respectively to obtain L - w i primary candidate new sequences S i ', select several candidate new sequences S i ' with the minimum sum of the maximum Hamming cross - correlations with other sequences in the current U except the sequence S i ', and form the candidate set C i .

[0024] Step 2 - 1: Successively set the 0 positions in the sequence S i in the current U to 1 respectively to obtain L - w i primary candidate new sequences S i ';

[0025] Step 2 - 2: Define the maximum Hamming cross - correlation as the maximum value of the number of positions where two sequences take the value 1 simultaneously under any cyclic shift. Calculate the maximum Hamming cross - correlations between the L - w i primary candidate new sequences S i ' and each of the other sequences in the current U except the sequence S i . Select the primary candidate new sequence S i ' with the minimum sum of the maximum Hamming cross - correlations with other sequences in the current U except the sequence S i ', and form the candidate set C i .

[0026] Step 4: Select a sequence with the minimum uniformity in C i to replace the sequence S i of the current U, and generate a new U.

[0027] Step 3-1: Calculate the uniformity of a sequence as the sum of the squares of the distances between the positions where adjacent values are 1 in this sequence.

[0028] Step 3-2: Randomly select a sequence with the minimum uniformity from the alternative set C i to replace the sequence S in the current U i , and generate a new U.

[0029] Step 5: If i < M, set i = i + 1 and return to Step 2; otherwise, set i = 1 and return to Step 2.

[0030] Example 1

[0031] The present invention implements the method using MATLAB software. Set M = 10, and construct a new protocol sequence set using the present invention. Each sequence S i has a feature set I i as follows.

[0032] I 1 = {1, 20, 29, 39, 49, 58, 68, 77, 87, 96, 115, 125, 134, 144, 153, 163, 172, 181, 191, 200}

[0033] I 2 = {1, 14, 28, 44, 52, 60, 71, 79, 87, 95, 103, 111, 119, 127, 135, 148, 162, 178, 194, 202}

[0034] I 3 = {1, 12, 24, 30, 36, 47, 59, 65, 71, 82, 94, 105, 117, 128, 140, 152, 164, 175, 186, 198}

[0035] I 4 = {1, 12, 22, 32, 43, 54, 64, 74, 85, 95, 106, 116, 127, 137, 148, 158, 169, 179, 190, 200}

[0036] I 5 = {1, 13, 26, 40, 53, 65, 72, 79, 91, 104, 111, 118, 131, 143, 157, 170, 182, 189, 196, 203}

[0037] I 6={1, 13, 25, 31, 38, 50, 62, 74, 86, 93, 99, 111, 123, 129, 136, 148, 160, 173, 185, 197}

[0038] I 7 ={1, 15, 29, 38, 46, 54, 63, 71, 80, 88, 97, 111, 125, 134, 142, 159, 167, 176, 184, 193}

[0039] I 8 ={1, 21, 31, 41, 51, 61, 71, 81, 91, 101, 111, 121, 131, 141, 151, 161, 171, 181, 191, 201}

[0040] I 9 ={1, 14, 27, 42, 49, 57, 70, 83, 90, 98, 111, 124, 132, 139, 154, 167, 180, 188, 195, 203}

[0041] I 10 ={1, 12, 23, 34, 45, 56, 67, 73, 78, 89, 100, 111, 122, 133, 144, 155, 166, 177, 188, 199}

[0042] The simulation scenario considers that M devices with unknown clock asynchrony in the wireless network send data to the base station. It is assumed that each device always has a data transmission requirement and is within the range that the base station can receive. The channel time is in units of time slots, and the length of all data packets is one unit time slot. When each device adopts the license-free access scheme based on the protocol sequence set, the protocol sequence values assigned are read sequentially by time slot, and data can be sent only when its sequence value is 1; while when each device adopts the license-free access scheme based on ALOHA, data is sent with a fixed probability by time slot. Compare the delay performance of the following three license-free access schemes in the above simulation scenario. Scheme 1: License-free access based on the optimal ALOHA with a fixed access probability of 1 / M. Scheme 2: License-free access based on the CRT sequence set with a cycle length of L = p M (2M - 1) and a code weight of M. Scheme 3: License-free access based on the novel protocol sequence set constructed by the present invention.

[0043] As Figure 2 shown, it can be seen that the novel protocol sequence set designed by the present invention for license-free access can achieve better average delay performance in the cases of M = 10, 12,..., 20.

Claims

1. A novel method for constructing a protocol sequence set for license-free access, characterized in that, the specific steps are as follows: Step 1: Given the number of devices M, define p M as the smallest prime number not less than M, and set the currently constructed sequence set U as a 0, 1 binary CRT sequence set U with a period length L = p M (2M - 1), set the target code weight value as N = 2M, and set i = 1; Step 2: Obtain the current U sequence S i with code weight w i , if w i < N, then go to Step 3; otherwise, the sequence construction ends. Step 3: Set the 0th position of the sequence S i to 1 respectively to obtain L-w i primary new sequences S i '. Define the maximum Hamming cross-correlation as the maximum value of the number of positions where two sequences take the value 1 simultaneously under any cyclic shift, and select several candidate new sequences S i ' with the minimum sum of the maximum Hamming cross-correlations with other sequences outside the current sequence S i ' to form the candidate set C i ; Step 4: Define the uniformity of the sequence as the sum of the squares of the distances between the positions where adjacent values are 1 in this sequence, and randomly select a sequence with the minimum uniformity in C i to replace the current sequence S of U i to generate a new U; Step 5: If i < M, set i = i + 1 and return to Step 2; otherwise, set i = 1 and return to Step 2.

2. The novel method for constructing a protocol sequence set for license-free access according to claim 1, characterized in that, the specific method for constructing the CRT sequence set U according to the parameters in Step 1 is: Step 1-1: Given the number of devices M, find the smallest prime number p not less than the number of devices M M , and set the sequence period as L = p M (2M - 1); Step 1-2: Define the set of all non-negative integers modulo n as Z n ={0, 1, 2,..., n - 1}; Step 1-3: According to the Chinese Remainder Theorem, define the mapping relationship: To make a one-dimensional sequence correspond to a two-dimensional matrix one by one, define: Obtain the sequence feature set I according to the above formula g It is as follows: where g is any integer from 1 to p M and the sequence feature set I g represents the positions of 1s in the sequence S g in the CRT sequence set.

3. The novel method for constructing a protocol sequence set for license-free access according to claim 1, characterized in that, The specific method for Step 2 is: Obtain the sequence S in the current U i and its Hamming weight w i , that is, the number of 1s in the sequence S i . If w i < N, then go to Step 3; otherwise, the sequence construction ends.

4. The novel method for constructing a protocol sequence set for license-free access according to claim 1, characterized in that, the specific method of Step 5 is: If i < M, set i = i + 1 and return to Step 2; otherwise, set i = 1 and return to Step 2.

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