Terminal priority-based irregular repeated time slot ALOHA protocol method

Abstract

The invention provides a protocol method of irregular repeated time slot ALOHA based on terminal priority, which mainly solves the problem that the throughput performance of an IRSA protocol and PR-ALOHA is reduced and low under high channel load. According to the scheme, the method comprises the following steps: on the basis of an IRSA protocol, adding an access controller, and constructing a P-IRSA scheme system model framework; according to the method, a new P-ISRA scheme is constructed, on the basis of an IRSA protocol, the original high performance of the IRSA scheme is reserved, an access controller influencing the access probability of the terminal equipment is added, and different access probabilities are given to the terminal equipment with different priorities according to the estimated value of the current channel load. The scheme is verified through actual experiments, and the superiority of the scheme is shown.

Description

Technical Field

[0001] The invention belongs to the technical field of wireless communications, and in particular relates to a protocol method of irregularly repeated time slot ALOHA based on terminal priority. Background Art

[0002] With the continuous development of the economy and society, communication scenarios and user needs are becoming increasingly diversified, and the communication needs of massive machine-type devices have become an urgent problem to be solved. The traditional random access strategy based on resource allocation is stretched when dealing with massive machine-type communication scenarios where the number of terminals changes frequently and short burst packets are dominant. Therefore, researchers have begun to refocus on the contention-based ALOHA and its derivative machine protocols proposed in the last century, especially after the introduction of iterative interference cancellation technology, the performance of these protocols has been significantly improved. For example, the contention-removing diversity slotted ALOHA (CRDSA) and iterative random subset assignment (IRSA) protocols, by optimizing the number of data packet copies and introducing iterative interference cancellation technology, not only improve the throughput performance, but also significantly reduce the probability of collision.

[0003] However, although the IRSA protocol performs well in theoretical throughput, it does not fully consider the user's quality of service (QoS) requirements, especially when the channel load is higher than the threshold, which will cause the service quality of some services to decline. In a large number of machine-type communications, a large part of the communication scenarios do not have high requirements for real-time performance, such as regularly updating system information and location information; correspondingly, there are many scenarios involving system security, payment and other requirements. In comparison, these scenarios should have higher access priorities. That is, when channel data packet conflicts cannot be avoided, try to ensure the communication needs of these scenarios. To solve this problem, the PR-ALHOA protocol reserves specific time slots in the data frame for high-priority services, and divides the traffic into low priority or high priority to handle different scenarios. PR-ALHOA solves the communication problem of high-priority scenarios well without affecting the total throughput. However, the throughput performance of PR-ALHOA is not as good as IRSA, and the utilization of channel resources is still worth optimizing. Summary of the invention

[0004] In order to overcome the deficiencies of the prior art and solve the problems of reduced throughput performance of the existing IRSA protocol under high channel load and low throughput performance of the PR-ALOHA protocol, the present invention proposes a protocol method of irregularly repeated time slot ALOHA based on terminal priority.

[0005] A protocol method of irregularly repeated time slot ALOHA based on terminal priority includes a P-IRSA system framework model; the P-IRSA system framework model is an IRSA protocol model with an access controller added thereto; the IRSA protocol model includes a terminal, a selector, a receiving channel and a receiving end; the access controller includes an access control adaptive method and a system channel load estimation method; the access control adaptive method calculates the system channel load according to the system channel load estimation method, multiplies the calculated access probability of a terminal with a priority of k by a random number of 0 to 1, and if the multiplied result is less than the access probability of a terminal with a priority of k, the terminal is allowed to access; if the multiplied result is greater than or equal to the access probability of a terminal with a priority of k, the access is denied; if the terminal is allowed to access, the selector uses the degree distribution of a predefined terminal to determine the number of data packet copies, and according to the number of data packet copies, the terminal will send data packet copies in different time slots; if the terminal is denied access, the access request of the next terminal is processed continuously.

[0006] Furthermore, the steps of the access control adaptive method are:

[0007] S1-101: Define the priority of the terminal according to the type of the terminal;

[0008] S1-102: Define the constraints of the P-IRSA system framework model:

[0009] The constraints of the P-IRSA system framework model are the simulation channel load threshold The probability that the channel load threshold G * , the constraint expression is:

[0010]

[0011] 0≤p ac (k)≤1,k=1,2,…,L;

[0012] Among them, P user (k) is the ratio of the number of terminals with priority k to the number of all terminals; p ac (k) is the access probability of the terminal with priority k; is the simulation channel load threshold, G is the system channel load; L is the number of terminal priorities;

[0013] S1-103: define a system channel load turning point P(k), which is used to adjust the access probability of terminals with different priorities; the number of channel load turning points P(k) is the same as the number of terminal priorities;

[0014] The expression formula of the system channel load turning point P(k) is:

[0015]

[0016] Among them, P user (i) is the ratio of the number of terminals with priority i to the number of all terminals; is the simulation channel load threshold;

[0017] S1-104: Calculate access probabilities of terminals with different priorities;

[0018] Calculate the system channel load, and based on the system channel load, calculate the access probability of terminals of different priorities.

[0019] Furthermore, the steps of the system channel load estimation method are:

[0020] Step 1: Calculate the number of time slots N in each frame where no terminal is connected to any time slot in the frame I :

[0021]

[0022] Where n is the number of time slots; m is the number of terminals in the current channel; Λ'(1) is the average number of data packet copies sent by all active terminals;

[0023] Step 2: Calculate the number of terminals in the current channel and obtain the estimated channel load G;

[0024] By calculating the number of terminals in the current channel, the estimated channel load G is:

[0025]

[0026] Where n represents the number of time slots; N I represents the number of time slots in each frame to which no terminal is connected; Λ'(1) represents the average number of data packet copies sent by all active terminals.

[0027] Furthermore, the system channel load includes four situations, specifically:

[0028] a. When the system channel load is less than or equal to the first turning point;

[0029] b. When the system channel load is greater than the first system channel load turning point, and the system channel load is less than or equal to the second system channel load turning point;

[0030] c. When the system channel load is greater than the ω-th system channel load turning point, and the system channel load is less than or equal to the ω+1-th system channel load turning point;

[0031] d. The system channel load is greater than the Lth system channel load turning point.

[0032] Furthermore, the step of calculating the access probability of terminals of different priorities is:

[0033] When the system channel load is case a, the following conditions apply:

[0034] G≤P(1);

[0035]

[0036] Where G is the system channel load; P(1) represents the load turning point of the first channel; P user (k) is the ratio of the number of terminals with priority k to the number of all terminals; L is the number of different terminal priorities;

[0037] At this time, the channel load has not yet reached the first turning point. When all terminals do not perform access control, the maximum throughput is obtained, that is:

[0038] p ac (k) = 1, k = 1, 2, ..., L;

[0039] Among them, p ac (k) is the access probability of a terminal with priority k; L is the number of different terminal priorities;

[0040] When the system channel load is case b, there is a condition: P(1) <G≤P(2);

[0041] Where G is the system channel load; P(1) represents the load turning point of the first channel; P(2) represents the load turning point of the second channel;

[0042] At this time, the channel load is between the first channel load turning point and the second channel load turning point. ac When (k)=1,k=1,2,...,L, we have:

[0043]

[0044] Among them, P user (k) is the ratio of the number of terminals with priority k to the number of all terminals; is the simulation channel load threshold, G is the system channel load;

[0045] When the system channel load exceeds the critical point, the throughput will be reduced, thus limiting the access probability of low-priority terminals. According to the constraints of the P-IRSA system framework model, there is a formula:

[0046]

[0047] Among them, P user (k) is the ratio of the number of terminals with priority k to the number of all terminals; p ac (k) is the access probability of the terminal with priority k; is the simulation channel load threshold, G is the system channel load, and L is the number of different terminal priorities;

[0048] In order to obtain the maximum throughput and ensure the transmission of high-priority terminals, the access probability p of terminals with different priorities is ac (k) is set to:

[0049]

[0050] Among them, P user (i) is the ratio of the number of terminals with priority i to the number of all terminals; p ac (k) is the access probability of the terminal with priority k; is the simulation channel load threshold, G is the system channel load, and L is the number of different terminal priorities;

[0051] When the system channel load is case c, the following conditions apply:

[0052] P(ω) <G≤P(ω+1),ω=2,3,...,L-1;

[0053] Where G is the system channel load; P(ω) represents the load turning point of the ωth channel; P(ω+1) represents the load turning point of the ω+1th system channel;

[0054] At this time, when p ac When (k)=1, k=1,2,...,L, we have the following formula:

[0055]

[0056] Among them, P user (k) is the ratio of the number of terminals with priority k to all terminals; p ac (k) is the access probability of the terminal with priority k; is the simulation channel load threshold, G is the system channel load, and L is the number of different terminal priorities;

[0057] In order to achieve the maximum throughput and ensure the data packet transmission of high-priority terminals, the access probability of high-priority terminals is set to 1 and the access probability of low-priority terminals is set to 0. The formula is:

[0058]

[0059] Among them, Puser (k) is the ratio of the number of terminals with priority k to all terminals; p ac (k) is the access probability of the terminal with priority k; is the simulation channel load threshold, G is the system channel load, and L is the number of different terminal priorities;

[0060] In order to obtain the maximum throughput and ensure the transmission of high-priority terminals, the access probability p of terminals with different priorities is ac (k) is set to:

[0061]

[0062] Among them, P user (i) is the ratio of the number of terminals with priority i to the number of all terminals; p ac (k) is the access probability of the terminal with priority k; is the simulation channel load threshold, G is the system channel load, L is the number of different terminal priorities, and ω is the ωth channel;

[0063] When the system channel load is situation d, the following conditions apply:

[0064] G>P(L);

[0065] Where G is the system channel load; P(L) represents the load turning point of the ωth channel;

[0066] At this time, only the terminal with the highest priority can access the channel, p ac (k) is set to:

[0067]

[0068] Among them, P user (1) is the ratio of the number of terminals with priority 1 to the number of all terminals; p ac (k) is the access probability of the terminal with priority k; is the simulation channel load threshold, G is the system channel load, and L is the number of different terminal priorities.

[0069] The beneficial effects of the present invention are as follows: the present invention adopts the P-IRSA scheme, which greatly reduces the packet loss rate and improves the throughput under high channel load compared with the IRSA scheme, and the channel load estimation proposed by the scheme is very close to the actual channel load, ensuring the service quality of key services under high load conditions. Under high channel load conditions, the communication needs of high-priority terminal devices are met first, thereby ensuring the service quality of key services. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1The design flow chart of the irregular repetitive time slot ALOHA protocol method based on terminal priority;

[0071] Figure 2 The simulation results of packet loss rate of different schemes changing with channel load G;

[0072] Figure 3 The simulation results of throughput of different schemes changing with channel load G. DETAILED DESCRIPTION

[0073] A protocol method for irregularly repeated time slot ALOHA based on terminal priority comprises the following steps:

[0074] S1: Based on the IRSA protocol, construct the P-IRSA system framework model;

[0075] The IRSA protocol model includes a terminal, a selector, a receiving channel and a receiving end;

[0076] The P-IRSA system framework model is to add an access controller on the basis of the IRSA protocol;

[0077] After receiving the terminal access request, the access controller determines whether the terminal is allowed to access according to the terminal priority and channel load;

[0078] If the terminal is allowed to access, the selector uses the degree distribution of the predefined terminals to determine the number of packet copies. According to the number of packet copies, the terminal will send packet copies in different time slots;

[0079] If the terminal access is denied, the access request of the next terminal will be processed;

[0080] The access control module gives different access probabilities to different terminals according to the terminal priority and channel load conditions, so that when the channel load is greater than the channel load threshold, the high-priority terminal enjoys a higher access probability;

[0081] The access controller includes an access control adaptive method and a system channel load estimation method; the access control adaptive method, according to the system channel load, multiplies the access probability of the terminal with a priority k calculated by a random number between 0 and 1, and if the multiplied result is less than the access probability of the terminal with a priority k, the terminal is allowed to access, otherwise the access is denied;

[0082] The access controller gives priority to meeting the communication needs of high-priority terminal devices under high channel load conditions, thereby ensuring the service quality of key services;

[0083] The steps of designing the access control adaptive method by the access controller are as follows:

[0084] S201: defining the priority of the terminal according to the type of the terminal;

[0085] S202: Define the constraints of the P-IRSA system framework model:

[0086] The constraints of the P-IRSA system framework model are the simulation channel load threshold The probability that the channel load threshold G * , the constraint condition makes the packet loss rate within the acceptable range, guarantees the traffic of high-priority terminals, and reduces the access of low-priority devices when the traffic load exceeds the critical point. The expression of the constraint condition is:

[0087]

[0088] 0≤p ac (k)≤1,k=1,2,…,L;

[0089] Among them, P user (k) is the ratio of the number of terminals with priority k to the number of all terminals; p ac (k) is the access probability of the terminal with priority k; is the simulation channel load threshold, G is the system channel load; L is the number of terminal priorities;

[0090] S203: defining a system channel load turning point P(k), where the system channel load turning point is used to adjust the access probability of terminals with different priorities; the number of channel load turning points P(k) is the same as the number of terminal priorities;

[0091] The expression formula of the system channel load turning point P(k) is:

[0092]

[0093] Among them, P user (i) is the ratio of the number of terminals with priority i to the number of all terminals; is the simulation channel load threshold;

[0094] S204: Calculate the access probability of the terminal;

[0095] According to the system channel load, the access probability of the terminal is calculated in four cases, specifically:

[0096] a. When the system channel load is less than or equal to the first turning point;

[0097] b. When the system channel load is greater than the first system channel load turning point, and the system channel load is less than or equal to the second system channel load turning point;

[0098] c. When the system channel load is greater than the ω-th system channel load turning point, and the system channel load is less than or equal to the ω+1-th system channel load turning point;

[0099] d. The system channel load is greater than the Lth system channel load turning point;

[0100] When the system channel load is case a, the following conditions apply:

[0101] G≤P(1);

[0102]

[0103] Where G is the system channel load; P(1) represents the load turning point of the first channel; P user (k) is the ratio of the number of terminals with priority k to the number of all terminals; p ac (k) is the access probability; L is the number of different terminal priorities;

[0104] At this time, the channel load has not yet reached the first turning point. When all terminals do not perform access control, the maximum throughput is obtained, that is:

[0105] p ac (k) = 1, k = 1, 2, ..., L;

[0106] Among them, p ac (k) is the access probability; L is the number of different terminal priorities;

[0107] When the system channel load is case b, the following conditions apply:

[0108] P(1) <G≤P(2);

[0109] Where G is the system channel load; P(1) represents the load turning point of the first channel; P(2) represents the load turning point of the second channel;

[0110] At this time, the channel load is between the first channel load turning point and the second channel load turning point. ac When (k)=1,k=1,2,...,L, we have:

[0111]

[0112]

[0113] Among them, P user (k) is the ratio of the number of terminals with priority k to the number of all terminals; is the simulation channel load threshold, G is the system channel load;

[0114] When the system channel load exceeds the critical point, the throughput will be reduced, thus limiting the access probability of low-priority terminals. According to the constraints of the P-IRSA system framework model, the following formula is available:

[0115]

[0116] Among them, P user (k) is the ratio of the number of terminals with priority k to the number of all terminals; p ac (k) is the access probability of the terminal with priority k; is the simulation channel load threshold, G is the system channel load, and L is the number of different terminal priorities;

[0117] In order to obtain the maximum throughput and ensure the transmission of high-priority terminals, the access probability of terminals with different priorities is set as follows:

[0118]

[0119] Among them, P user (i) is the ratio of the number of terminals with priority i to the number of all terminals; p ac (k) is the access probability of the terminal with priority k; is the simulation channel load threshold, G is the system channel load, and L is the number of different terminal priorities;

[0120] When the system channel load is case c, the following conditions apply:

[0121] P(ω) <G≤P(ω+1),ω=2,3,...,L-1;

[0122] Where G is the system channel load; P(ω) represents the load turning point of the ωth channel; P(ω+1) represents the load turning point of the ω+1th system channel;

[0123] At this time, when p ac When (k)=1, k=1,2,...,L, we have the following formula:

[0124]

[0125] Among them, P user (k) is the ratio of the number of terminals with priority k to all terminals; p ac (k) is the access probability of the terminal with priority k; is the simulation channel load threshold, G is the system channel load, and L is the number of different terminal priorities;

[0126] In order to achieve the maximum throughput and ensure the data packet transmission of high-priority terminals, the access probability of high-priority terminals is set to 1 and the access probability of low-priority terminals is set to 0. The following formula is used:

[0127]

[0128] Among them, P user (k) is the ratio of the number of terminals with priority k to all terminals; p ac (k) is the access probability of the terminal with priority k; is the simulation channel load threshold, G is the system channel load, and L is the number of different terminal priorities;

[0129] In order to obtain the maximum throughput and ensure the transmission of high-priority terminals, the access probability of terminals with different priorities is set as follows:

[0130]

[0131] Among them, P user (i) is the ratio of the number of terminals with priority i to the number of all terminals; p ac (k) is the access probability of the terminal with priority k; is the simulation channel load threshold, G is the system channel load, L is the number of different terminal priorities, and ω is the ωth channel;

[0132] When the system channel load is situation d, the following conditions apply:

[0133] G>P(L);

[0134] Where G is the system channel load; P(L) represents the load turning point of the ωth channel;

[0135] At this time, only the highest priority terminal can access the channel, and the access probability is set as follows:

[0136]

[0137] Among them, P user (1) is the ratio of the number of terminals with priority 1 to the number of all terminals; p ac (k) is the access probability of the terminal with priority k; is the simulation channel load threshold, G is the system channel load, and L is the number of different terminal priorities;

[0138] The access controller designs an access control adaptive method, which can effectively control the number of data packets in the channel and avoid the increase of packet loss rate and the decrease of throughput caused by channel overload by dividing the terminals into multiple priority levels and dynamically adjusting the access probability of terminals of each priority level according to the channel load situation;

[0139] The estimation method of the system channel load G is:

[0140] Step 1: The number of time slots in each frame where no terminal is connected to any time slot in the frame is N I :

[0141]

[0142] Where n represents the number of time slots; m represents the number of terminals in the current channel; Λ'(1) represents the average number of data packet copies sent by all active terminals;

[0143] Step 2: Calculate the number of terminals in the current channel and obtain the estimated channel load G;

[0144] In this embodiment, the estimated channel load G obtained by calculating the number of terminals in the current channel is expressed as follows:

[0145]

[0146] Where n represents the number of time slots; N I represents the number of time slots in each frame with no terminal connected to it; Λ'(1) represents the average number of data packet copies sent by all active terminals;

[0147] S3. Based on the P-IRSA system framework model, an iterative elimination scheme is used to evaluate the packet loss rate and throughput of the network system;

[0148] For the iterative elimination scheme, the probability that the state of an edge associated with a time slot node is unknown during the i-th iterative interference elimination process is defined as p i , assuming that the probability that the state of an edge associated with a terminal node is unknown is q i Then, p i and q i Respectively expressed as:

[0149]

[0150] Among them, ρ l represents the probability that an edge is connected to a time slot node with degree l; p i,l represents the probability that the state of the edge connected to a time slot node with degree l is unknown during the i-th iteration of interference elimination; λ l represents the probability that an edge is connected to a terminal node with degree l; qi,l It represents the probability that the state of the edge connected to a terminal node with degree l is unknown during the i-th iteration of interference elimination.

[0151] In this embodiment, since the time slot node and the terminal node require different processing logic when decoding: the terminal node with an in-degree of l only needs to successfully receive any one of l different time slot data packet copies to recover all other copies, while the time slot node with an in-degree of l needs l-1 terminal node data packets to successfully receive to decode the last data packet, thus defining p i,l and q i,l as follows:

[0152] p i,l =1-(1-q i ) l-1 ;

[0153] q i,l =p i-1 i-1 ;

[0154] Among them, p i represents the probability that the state of an edge associated with a time slot node is unknown during the i-th iteration of interference elimination; q i represents the probability that the state of an edge associated with a terminal node is unknown during the i-th iteration of interference elimination; p i,l represents the probability that the state of the edge connected to a time slot node with degree l is unknown during the i-th iteration of interference elimination; q i,l It represents the probability that the state of the edge connected to a terminal node with degree l is unknown during the i-th iteration of interference elimination.

[0155] According to the above formula, we can get p i and q i , respectively expressed as the following formulas:

[0156]

[0157] Among them, p i represents the probability that the state of an edge associated with a time slot node is unknown during the i-th iteration of interference elimination; q i represents the probability that the state of an edge associated with a terminal node is unknown during the i-th iteration of interference elimination; ρ l represents the probability that an edge is connected to a time slot node with degree l; λ l It represents the probability that an edge is connected to a terminal node with degree l.

[0158] In this embodiment, the derived packet loss rate P L The calculation formula is as follows:

[0159]

[0160] Among them, Λ l represents the probability that the terminal node degree is l; p l It represents the probability that the node degree of a terminal node is l.

[0161] In this embodiment, the derived calculation formula for throughput is as follows:

[0162] T=G(1-P L );

[0163] Where G represents the channel load; P L Indicates the packet loss rate.

[0164] In this embodiment, the channel load threshold G * It is the maximum channel load that the system can converge to so that all data packets can be successfully received. When the channel load is lower than G * When the channel load is higher than G * When , it cannot converge to 0, and the channel load satisfies the following expression:

[0165]

[0166] Where Λ'(1) represents the average number of data packet copies sent by all active terminals; G represents the channel load; q i It represents the probability that the state of an edge associated with a terminal node is unknown during the i-th iteration of interference elimination.

[0167] The final channel load threshold G is derived based on mathematical derivation * The expression is as follows:

[0168]

[0169] Among them, G * represents the channel load threshold; Λ'(1) represents the average number of data packet copies sent by all active terminals; λ2 represents the probability that an edge is connected to a terminal node with degree 2.

[0170] The iterative elimination scheme can accurately evaluate the packet loss rate and throughput of the network system through precise iterative elimination scheme design and probability calculation, significantly improving the efficiency and reliability of network transmission.

[0171] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0172] Now, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be understood that the embodiments shown and described in the accompanying drawings are only exemplary and are intended to explain the principles and spirit of the present invention, rather than to limit the scope of the present invention.

[0173] like Figure 1 As shown, an irregularly repeated time slot ALOHA protocol scheme based on terminal priority includes the following steps:

[0174] S1. Based on the IRSA protocol, the P-IRSA scheme system model framework is constructed, which mainly includes the terminal, access controller, selector, receiving channel and receiving end;

[0175] S2. Based on the P-IRSA scheme system model, design an access control adaptive scheme in the access controller;

[0176] S3. Based on the P-IRSA scheme system model, an iterative elimination scheme is designed at the receiving end;

[0177] In this embodiment, the P-IRSA solution system model framework in step S1 adds modules for channel load estimation and access control.

[0178] In this embodiment, the access control module is specifically: the terminal device uses an access controller (Access Controller) to limit the number of data packets in the channel before accessing, and the access controller gives different terminal devices different access probabilities according to the terminal device priority and channel load conditions to ensure that when the channel load is greater than the channel load threshold, high-priority terminal devices enjoy a higher access probability.

[0179] In this embodiment, in step S2, the access controller designs an access control adaptive scheme, and the access control adaptive algorithm is specifically:

[0180] S201. Divide the total number of terminals into multiple priority levels;

[0181] S202. Define simulation channel load threshold The probability is slightly less than the system channel load threshold G * , ensure that the packet loss rate is within an acceptable range;

[0182] S203. Define L channel load turning points P(k) to adjust the access probability of terminals of different priorities;

[0183] S204. Design the access probability of each terminal node under different channel loads.

[0184] In this embodiment, the simulation channel load threshold defined in step S202 is The probability is slightly less than the system channel load threshold G * The expression formula is:

[0185]

[0186] 0≤p ac (k)≤1,k=1,2,…,L;

[0187] Among them, P user (k) is the ratio of terminals with priority k to all terminal devices; p ac (k) is the access probability; is the simulation channel load threshold, and G is the system channel load.

[0188] In this embodiment, the expression formula of the L channel load turning points P(k) defined in step S203 is:

[0189]

[0190] Among them, P user (i) is the ratio of terminals with priority i to all terminal devices; is the simulated channel load threshold.

[0191] In this embodiment, the access probability of each terminal node under different channel loads is designed in step S204 to consider four different situations according to the channel load, specifically:

[0192] a. The channel load has not yet reached the first turning point.

[0193] b. The channel load is between the first channel load turning point and the second channel load turning point.

[0194] c. The channel load is between the ωth channel load turning point and the ω+1th channel load turning point.

[0195] d. The channel load exceeds the Lth channel load turning point.

[0196] In this embodiment, for the above situation a, the following conditions apply:

[0197] G≤P(1);

[0198]

[0199] Where G is the system channel load; P(1) represents the load turning point of the first channel; P user (k) is the ratio of terminals with priority k to all terminal devices; p ac (k) is the access probability; L is the number of channels.

[0200] At this time, the channel load has not yet reached the first turning point. When all terminal nodes do not perform access control, the maximum throughput is obtained, that is:

[0201] p ac (k) = 1, k = 1, 2, ..., L;

[0202] Among them, p ac (k) is the access probability; L is the number of channels.

[0203] In this embodiment, for the above situation b, the following conditions apply:

[0204] P(1) <G≤P(2);

[0205] Where G is the system channel load; P(1) represents the load turning point of the first channel; and P(2) represents the load turning point of the second channel.

[0206] At this time, the channel load is between the first channel load turning point and the second channel load turning point. ac When (k)=1,k=1,2,...,L, we have:

[0207]

[0208] Among them, P user (k) is the ratio of terminals with priority k to all terminal devices; p ac (k) is the access probability; is the simulation channel load threshold, G is the system channel load, and L is the number of channels.

[0209] When the channel load exceeds the critical point, the throughput will be reduced. Therefore, the access probability of low-priority terminals should be limited. According to the probability that the simulation channel load threshold is less than the system channel load threshold, the following formula is obtained:

[0210]

[0211] Among them, P user (k) is the ratio of terminals with priority k to all terminal devices; p ac (k) is the access probability; is the simulation channel load threshold, G is the system channel load, and L is the number of channels.

[0212] In order to obtain the maximum throughput and ensure the transmission of high-priority terminals, the access probability of terminals with different priorities is set as follows:

[0213]

[0214] Among them, P user(i) is the ratio of terminals with priority i to all terminal devices; p ac (k) is the access probability; is the simulation channel load threshold, G is the system channel load, and L is the number of channels.

[0215] In this embodiment, for the above situation c, the following conditions apply:

[0216] P(ω) <G≤P(ω+1),ω=2,3,...,L-1;

[0217] Where G is the system channel load; P(ω) represents the load turning point of the ωth channel; and P(ω+1) represents the load turning point of the ω+1th channel.

[0218] At this time, when p ac When (k)=1, k=1,2,...,L, we have the following formula:

[0219]

[0220] Among them, P user (k) is the ratio of terminals with priority k to all terminal devices; p ac (k) is the access probability; is the simulation channel load threshold, G is the system channel load, and L is the number of channels.

[0221] In order to achieve the maximum throughput and ensure the data packet transmission of high-priority terminals, the access probability of high-priority terminals is set to 1 and the access probability of low-priority terminals is set to 0. The following formula is used:

[0222]

[0223] Among them, P user (k) is the ratio of terminals with priority k to all terminal devices; p ac (k) is the access probability; is the simulation channel load threshold, G is the system channel load, and L is the number of channels.

[0224] In order to obtain the maximum throughput and ensure the transmission of high-priority terminals, the access probability of terminals with different priorities is set as follows:

[0225]

[0226] Among them, P user (i) is the ratio of terminals with priority i to all terminal devices; p ac (k) is the access probability; is the simulation channel load threshold, G is the system channel load, L is the number of channels, and ω is the ωth channel.

[0227] In this embodiment, for the above situation d, the following conditions apply:

[0228] G>P(L);

[0229] Where G is the system channel load; P(L) represents the load turning point of the ωth channel.

[0230] At this time, only the highest priority terminal can access the channel, and the access probability is set as follows:

[0231]

[0232] Among them, P user (1) is the ratio of terminals with priority 1 to all terminal devices; p ac (k) is the access probability; is the simulation channel load threshold, G is the system channel load, and L is the number of channels.

[0233] In this embodiment, the method for estimating the channel load required for designing the access probability in step S204 includes defining the number of time slots N in each frame to which no terminal node is connected. I And calculate the number of terminals in the current channel.

[0234] In this embodiment, the channel load estimation method defines the number of time slots N in each frame to which no terminal node is connected. I The expression is as follows:

[0235]

[0236] Where n represents the number of time slots; m represents the number of terminals in the current channel; Λ'(1) represents the average number of data packet copies sent by all active terminals.

[0237] In this embodiment, the estimated channel load G' obtained by calculating the number of terminals in the current channel is expressed as follows:

[0238]

[0239] Where n represents the number of time slots; N I represents the number of time slots in each frame with no terminal node connected to it; Λ'(1) represents the average number of data packet copies sent by all active terminals.

[0240] In this embodiment, the simulation channel load threshold is slightly smaller than the system channel load threshold, which ensures that the packet loss rate can remain within an acceptable range when the channel load is high, thereby improving the stability and reliability of the system. At the same time, by defining multiple channel load turning points and adjusting the access probability according to different stages of the channel load, it is possible to flexibly respond to communication needs under different load conditions, especially in high-load conditions, giving priority to accessing high-priority terminals, thereby improving the overall performance and service quality of the system.

[0241] In this embodiment, the iterative elimination scheme designed at the receiving end in step S3 is analyzed using a bipartite graph method, and its performance such as throughput and packet loss rate is derived.

[0242] In this embodiment, for the iterative elimination scheme, the probability that the state of a certain edge associated with a time slot node is unknown during the i-th iterative interference elimination process is defined as p i , assuming that the probability that the state of an edge associated with a terminal node is unknown is q i Then, p i and q i Respectively expressed as:

[0243]

[0244] Among them, ρ l represents the probability that an edge is connected to a time slot node with degree l; p i,l represents the probability that the state of the edge connected to a time slot node with degree l is unknown during the i-th iteration of interference elimination; λ l represents the probability that an edge is connected to a terminal node with degree l; q i,l It represents the probability that the state of the edge connected to a terminal node with degree l is unknown during the i-th iteration of interference elimination.

[0245] In this embodiment, since the time slot node and the terminal node require different processing logic when decoding: the terminal node with an in-degree of l only needs to successfully receive any one of l different time slot data packet copies to recover all other copies, while the time slot node with an in-degree of l needs l-1 terminal node data packets to successfully receive to decode the last data packet, thus defining p i,l and q i,l as follows:

[0246] p i,l =1-(1-q i ) l-1 ;

[0247] q i,l =p i-1 i-1 ;

[0248] Among them, p i represents the probability that the state of an edge associated with a time slot node is unknown during the i-th iteration of interference elimination; q i represents the probability that the state of an edge associated with a terminal node is unknown during the i-th iteration of interference elimination; p i,l represents the probability that the state of the edge connected to a time slot node with degree l is unknown during the i-th iteration of interference elimination; q i,l It represents the probability that the state of the edge connected to a terminal node with degree l is unknown during the i-th iteration of interference elimination.

[0249] According to the above formula, we can get p i and q i , respectively expressed as the following formulas:

[0250]

[0251] Among them, p i represents the probability that the state of an edge associated with a time slot node is unknown during the i-th iteration of interference elimination; q i represents the probability that the state of an edge associated with a terminal node is unknown during the i-th iteration of interference elimination; ρ l represents the probability that an edge is connected to a time slot node with degree l; λ l It represents the probability that an edge is connected to a terminal node with degree l.

[0252] In this embodiment, the derived packet loss rate P L The calculation formula is as follows:

[0253]

[0254] Among them, Λ l represents the probability that the terminal node degree is l; p l It represents the probability that the node degree of a terminal node is l.

[0255] In this embodiment, the derived calculation formula for throughput is as follows:

[0256] T=G(1-P L );

[0257] Where G represents the channel load; P L Indicates the packet loss rate.

[0258] In this embodiment, the channel load threshold G * It is the maximum channel load that the system can converge to so that all data packets can be successfully received. When the channel load is lower than G * When the channel load is higher than G *When , it cannot converge to 0, and the channel load satisfies the following expression:

[0259]

[0260] Where Λ'(1) represents the average number of data packet copies sent by all active terminals; G represents the channel load; q i It represents the probability that the state of an edge associated with a terminal node is unknown during the i-th iteration of interference elimination.

[0261] The final channel load threshold G is derived based on mathematical derivation * The expression is as follows:

[0262]

[0263] Among them, G * represents the channel load threshold; Λ'(1) represents the average number of data packet copies sent by all active terminals; λ2 represents the probability that an edge is connected to a terminal node with degree 2.

[0264] The present invention is simulated and verified, and the relationship between the channel load and the packet state is obtained through numerical analysis. The terminal node degree distribution Λ=0.5x 2 +0.28x 3 +0.22x 8 ,n=200,channel load G=[1,0.938,0.85],channel threshold G * =0.985. The results show that when the channel load is G=0.938 and G=0.85, the value of the unknown probability q of the packet will drop significantly after one iteration, which means that the system can effectively decode and recover the packet under these loads. When the channel load is G=1, the value of the unknown probability q of the packet still decreases in the high value interval (0.8,1), but starts to increase in the low value interval (0, 0.8), which indicates that the high channel load leads to intensified packet conflicts and some packets enter a deadlock state and cannot be successfully received or recovered.

[0265] According to the experimental results, the actual performance of the proposed channel load estimation method shows that the estimated channel load is very close to the actual channel load. By calculating and comparing the estimated mean and variance under different channel loads, it can be found that under low channel load, the variance of the estimated value is small, and as the channel load increases, the variance gradually increases. When the channel load is high, the variance increases significantly, which indicates that the accuracy of the estimation decreases under high load. When the actual channel load G = 0.5, the probability density distribution of the estimated channel load is estimated. According to the image obtained by the experiment, it can be seen that the image is approximately a Gaussian distribution, and its mean and variance are closely related to the actual channel load.

[0266] like Figure 2 and Figure 3 As shown: The actual simulation experiment used the terminal node degree distribution Λ = 0.5x 2 +0.28x 3 +0.22x 8 ,n=200 (maximum number of iterations) When the channel load G is at a high level, the packet loss rate of IRSA approaches 100%, while that of P-IRSA approaches 1%; the actual simulation experiment uses the terminal node degree distribution Λ=0.5x 2 +0.28x 3 +0.22x 8 ,n=200 (maximum number of iterations) When the channel load G is at a high level, the IRSA throughput rate approaches 0%, while the P-IRSA throughput rate approaches 70%.

[0267] Throughput performance analysis shows that the throughput performance of the P-IRSA scheme is particularly outstanding under high channel load. Under low channel load G<0.5, the throughput of IRSA, AC-CRDSA and P-IRSA is almost equal to the channel load, there are fewer packet conflicts, and the decoding process is efficient. As the channel load increases, the throughput of IRSA gradually decreases, especially when G>0.8, the throughput drops rapidly, which is consistent with the previous theoretical analysis. The throughput performance of AC-CRDSA is relatively stable due to the introduction of the access control mechanism, but its maximum throughput remains at around 0.5. The P-IRSA scheme has the best throughput performance under high channel load, especially in terms of throughput protection of high-priority terminals, where P-IRSA shows significant advantages. These results show that P-IRSA effectively improves the overall throughput of the system by dynamically adjusting the terminal access probability.

Claims

1. A protocol method for irregularly repeated time slot ALOHA based on terminal priority, comprising an IRSA protocol model, wherein the IRSA protocol model comprises a terminal, a selector, a receiving channel and a receiving end, characterized in that: An access controller is added on the basis of the IRSA protocol model to form a P-IRSA system framework model; the access controller includes an access control adaptive method and a system channel load estimation method; the access control adaptive method multiplies the access probability of a terminal with a priority k calculated by the system channel load estimation method by a random number between 0 and 1, and if the multiplied result is less than the access probability of the terminal with a priority k, the terminal is allowed to access; if the multiplied result is greater than or equal to the access probability of the terminal with a priority k, the terminal is denied access; If the terminal is allowed to access, the selector uses the degree distribution of the predefined terminals to determine the number of data packet copies; the terminal will send data packet copies in different time slots according to the number of data packet copies; If the terminal access is denied, the next terminal access request will be processed.

2. The protocol method of irregularly repeated time slot ALOHA based on terminal priority according to claim 1, characterized in that: The steps of the access control adaptive method of the access controller are: S1-101: Define the priority of the terminal according to the type of the terminal; S1-102: Define the constraints of the P-IRSA system framework model: The constraints of the P-IRSA system framework model are the simulation channel load threshold The probability that the channel load threshold G * , the constraint expression is: 0≤p ac (k)≤1,k=1,2,...,L; Among them, P user (k) is the ratio of the number of terminals with priority k to the number of all terminals; p ac (k) is the access probability of the terminal with priority k; is the simulation channel load threshold, G is the system channel load; L is the number of terminal priorities; S1-103: define a system channel load turning point P(k), which is used to adjust the access probability of terminals with different priorities; the number of channel load turning points P(k) is the same as the number of terminal priorities; The expression formula of the system channel load turning point P(k) is: Among them, P user (i) is the ratio of the number of terminals with priority i to the number of all terminals; is the simulation channel load threshold; S1-104: Calculate access probabilities of terminals with different priorities; Calculate the system channel load, and calculate the access probability of terminals of different priorities based on the system channel load.

3. The protocol method of irregularly repeated time slot ALOHA based on terminal priority according to claim 1, characterized in that: The steps of the system channel load estimation method are: Step 1: Calculate the number of time slots N in each frame where no terminal is connected to any time slot in the frame I : Where n is the number of time slots; m is the number of terminals in the current channel; Λ'(1) is the average number of data packet copies sent by all active terminals; Step 2: Calculate the number of terminals in the current channel and obtain the estimated channel load G; By calculating the number of terminals in the current channel, the estimated channel load G is: Where n represents the number of time slots; N I represents the number of time slots in each frame to which no terminal is connected; Λ'(1) represents the average number of data packet copies sent by all active terminals.

4. The protocol method of irregularly repeated time slot ALOHA based on terminal priority according to claim 2, characterized in that: The system channel load is as follows: a. When the system channel load is less than or equal to the first turning point; b. When the system channel load is greater than the first system channel load turning point, and the system channel load is less than or equal to the second system channel load turning point; c. When the system channel load is greater than the ω-th system channel load turning point, and the system channel load is less than or equal to the ω+1-th system channel load turning point; d. The system channel load is greater than the Lth system channel load turning point.

5. The protocol method of irregularly repeated time slot ALOHA based on terminal priority according to claim 4, characterized in that: The steps of calculating the access probabilities of terminals with different priorities are: When the system channel load is case a, the following conditions apply: G≤P(1); Where G is the system channel load; P(1) represents the load turning point of the first channel; P user (k) is the ratio of the number of terminals with priority k to the number of all terminals; L is the number of different terminal priorities; At this time, the channel load has not yet reached the first turning point. When all terminals do not perform access control, the maximum throughput is obtained, that is: p ac (k)=1,k=1,2,...,L; Among them, p ac (k) is the access probability of a terminal with priority k; L is the number of different terminal priorities; When the system channel load is case b, there is a condition: P(1) <G≤P(2); Where G is the system channel load; P(1) represents the load turning point of the first channel; P(2) represents the load turning point of the second channel; At this time, the channel load is between the first channel load turning point and the second channel load turning point. ac When (k)=1,k=1,2,...,L, we have: Among them, P user (k) is the ratio of the number of terminals with priority k to the number of all terminals; is the simulation channel load threshold, G is the system channel load; When the system channel load exceeds the critical point, the throughput will be reduced, thus limiting the access probability of low-priority terminals. According to the constraints of the P-IRSA system framework model, there is a formula: Among them, P user (k) is the ratio of the number of terminals with priority k to the number of all terminals; p ac (k) is the access probability of the terminal with priority k; is the simulation channel load threshold, G is the system channel load, and L is the number of different terminal priorities; In order to obtain the maximum throughput and ensure the transmission of high-priority terminals, the access probability p of terminals with different priorities is ac (k) is set to: Among them, P user (i) is the ratio of the number of terminals with priority i to the number of all terminals; p ac (k) is the access probability of the terminal with priority k; is the simulation channel load threshold, G is the system channel load, and L is the number of different terminal priorities; When the system channel load is case c, the following conditions apply: P(ω) <G≤P(ω+1),ω=2,3,...,L-1; Where G is the system channel load; P(ω) represents the load turning point of the ωth channel; P(ω+1) represents the load turning point of the ω+1th system channel; At this time, when p ac When (k)=1, k=1,2,...,L, we have the following formula: Among them, P user (k) is the ratio of the number of terminals with priority k to all terminals; p ac (k) is the access probability of the terminal with priority k; is the simulation channel load threshold, G is the system channel load, and L is the number of different terminal priorities; In order to achieve the maximum throughput and ensure the data packet transmission of high-priority terminals, the access probability of high-priority terminals is set to 1 and the access probability of low-priority terminals is set to 0. The formula is: Among them, P user (k) is the ratio of the number of terminals with priority k to all terminals; p ac (k) is the access probability of the terminal with priority k; is the simulation channel load threshold, G is the system channel load, and L is the number of different terminal priorities; In order to obtain the maximum throughput and ensure the transmission of high-priority terminals, the access probability p of terminals with different priorities is ac (k) is set to: Among them, P user (i) is the ratio of the number of terminals with priority i to the number of all terminals; p ac (k) is the access probability of the terminal with priority k; is the simulation channel load threshold, G is the system channel load, L is the number of different terminal priorities, and ω is the ωth channel; When the system channel load is situation d, the following conditions apply: G>P(L); Where G is the system channel load; P(L) represents the load turning point of the ωth channel; At this time, only the terminal with the highest priority can access the channel, p ac (k) is set to: Among them, P user (1) is the ratio of the number of terminals with priority 1 to the number of all terminals; p ac (k) is the access probability of the terminal with priority k; is the simulation channel load threshold, G is the system channel load, and L is the number of different terminal priorities.

6. A computer-readable storage medium, wherein a computer program is stored in the medium, characterized in that: When the computer program is executed by a processor, the protocol method of irregularly repeated time slot ALOHA based on terminal priority according to any one of claims 1 to 5 is implemented.

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