High-timeliness cooperative transmission method for aviation ad hoc network

Abstract

The invention discloses a high-timeliness cooperative transmission method for an aviation ad hoc network, and belongs to the technical field of wireless communication. Firstly, an aviation ad hoc network system model is constructed; secondly, dividing a transmission time slot into two parts, selecting an aircraft of which the forwarding distance is smaller than the distance of an aircraft transceiver as a candidate relay, and completing a data broadcast transmission process to each candidate relay by a transmitter in the previous part of time slot; thirdly, the available frequency spectrum is divided into a plurality of sub-channels, and the aircraft relay selects the orthogonal sub-channels to complete data forwarding and transmission to the receiver in the latter part of time slots; fourthly, performing performance evaluation and optimal parameter searching on different time slot distribution proportions and sub-channel division numbers; and finally, implementing a distributed relay forwarding scheme according to an optimization result. According to the method, inherent challenges of the aviation ad hoc network can be effectively resisted, and adverse factors such as wireless interference and long-time deep attenuation can be resisted; the transmission time distribution proportion and the sub-channel division number can be flexibly adjusted, the information transmission timeliness is enhanced, and the network survivability is enhanced.

Description

Technical Field

[0001] The present invention belongs to the field of wireless communication technology, and relates to a high-efficiency coordinated transmission method for aviation ad hoc networks, and in particular to a high-efficiency coordinated transmission method combining distributed aircraft relay and frequency domain sub-channel division. Background Art

[0002] Aeronautical ad hoc networks use sensors and communication equipment to monitor the surrounding environment in real time, including aircraft position, speed, control information and other environmental status information, providing basic support for the dynamic adjustment of the network. The timeliness and accuracy of the transmission of these perception information is crucial for aircraft to make scientific decisions. However, in the scenario of aeronautical ad hoc networks, wireless transmission links are usually accompanied by the relative movement of the aircraft's spatial position, causing the channel gain of the transceiver to change rapidly, and the fast-changing wireless channel will affect the timeliness and accuracy of information transmission. When there are multiple activated aircraft nodes in the aeronautical ad hoc network, limited wireless resources cause concurrent links to generate wireless co-frequency interference, and relative movement will make the network topology time-varying and random, resulting in more complex and dynamic wireless co-frequency interference, thereby generating additional delays in the transmission of perception information in the network, affecting the timeliness and accuracy of information transmission. The self-organizing characteristics of the aeronautical network may result in jammers that are closer than the transmitter, causing strong interference to the aircraft receiver. The sparse deployment of aircraft causes the aircraft's transceiver to experience ultra-long-distance deep fading, and the occlusion characteristics of the earth's own sphere make it difficult for aircraft to interact wirelessly directly, requiring intermediate aircraft nodes to relay and forward. In addition, aircraft may suffer from sudden interference or damage, making it impossible to forward the current environmental status information in a timely manner. These wireless interference, long-distance deep fading, and earth occlusions cause multiple types of information transmission uncertainty scenarios in aviation ad hoc networks, resulting in information transmission failures. This will cause a backlog of perception data at the source or relay node, and the receiver will not be able to obtain the latest environmental status information in time to make decisions, resulting in decision deviations. In order to combat the uncertainty of the transmission environment, redundant transmission is a powerful weapon to combat information transmission failures, but the multiple retransmission strategies often adopted in existing networks cannot achieve timely transmission of information. For example, long-term deep fading and wireless interference will still cause data retransmission failures, thereby affecting the timely and accurate transmission of information. In view of the time-varying characteristics of aeronautical ad hoc networks, existing literature combines fountain codes and reliable user datagram protocols to design a reliable and effective data transmission protocol with adjustable code rate, so as to complete the data transmission task with only one transmission as much as possible, so as to counter the negative impact of the retransmission strategy on the information transmission delay. (Reference Qin Luo and Junfeng Wang. FRUDP: A Reliable Data Transport Protocol for Aeronautical Ad Hoc Networks [J]. IEEE Journal on Selected Areas in Communications, 2018, 36 (2): 257-267.) However, this method is difficult to solve the scenario where the transmission is blocked in aeronautical ad hoc networks, that is, the scenario where the direct wireless signal disappears.In addition, this strategy does not consider the timeliness of information, so that under harsh transmission conditions, the strategy can only successfully transmit data by lowering the bit rate to extend the transmission time, but too long a transmission time will also cause the receiver to be unable to obtain the latest environmental status information in a timely manner. Therefore, the present invention shortens the data transmission distance between transceivers by using distributed aircraft relay forwarding, and combines the frequency domain sub-channel division method to eliminate mutual interference between distributed relays, thereby improving the timeliness of data transmission.

[0003] This invention is supported by the Aeronautical Science Foundation of China (2022Z001063001). Summary of the invention

[0004] The multiple retransmission strategy in the existing aviation ad hoc network is difficult to solve the problem of long-term and long-distance deep fading and wireless interference causing the failure of perception data transmission, thereby affecting the timely and accurate information transmission. In view of the above problems, the present invention proposes a high-efficiency cooperative transmission method that combines distributed aircraft relay and frequency domain sub-channel division to enhance network survivability, and proposes a matching survivability evaluation and optimization method. Specifically, the present invention relates to a two-stage information transmission process, in which the first stage is that the aircraft transmitter negotiates with the aircraft located between the transceiver to relay auxiliary forwarding data and broadcast the perception data packet to each aircraft relay; the second stage is that the aircraft relay that successfully decodes the perception data packet selects an orthogonal frequency domain sub-channel to receive the aircraft for information transmission. In the proposed method, the cooperative transmission of the distributed relay nodes is used to combat uncertainties such as long-distance path loss and earth occlusion, while the frequency domain sub-channel division is used to combat frequency-selective deep fading and wireless interference. Since the high-efficiency cooperative transmission method proposed by the present invention is completed by the two-stage transmission scheme through adaptive dynamic scheduling of the transmission time allocation ratio and the number of sub-channel divisions, it is necessary to evaluate in time according to the actual situation for flexible scheduling. Therefore, the present invention proposes an optimization method for information timeliness, provides a calculation method for the information age that the proposed collaborative transmission method can achieve, and is used to quickly evaluate whether the proposed collaborative transmission method can enhance network survivability under a certain aviation ad hoc network scenario and system parameter configuration, as well as to find the optimal transmission time allocation ratio and sub-channel division number that minimizes the information age.

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

[0006] A high-efficiency cooperative transmission method for aviation ad hoc networks is a high-efficiency cooperative transmission method that combines distributed aircraft relays and frequency domain sub-channel division. The high-efficiency cooperative transmission method first constructs an aviation ad hoc network system model based on the collected network information. Secondly, the transmission time slot is divided into two parts, and aircraft with a forwarding distance less than the distance of the aircraft transceiver are selected as candidate relays. The transmitter uses all available spectrum to complete the data broadcast transmission process to each candidate relay in the first part of the time slot. Third, the available spectrum is divided into multiple sub-channels, and each aircraft relay that correctly decodes the perception data will select an orthogonal sub-channel to complete the data forwarding transmission to the receiver in the second part of the time slot. Fourth, based on the established aviation ad hoc network system model, an analytical expression for solving the average peak information age is established, and performance evaluation and optimal parameters are performed for different time slot allocation ratios and sub-channel division numbers. Finally, based on the optimization results, a distributed relay forwarding scheme for aircraft is implemented. The following steps are included:

[0007] Step 1: construct an aviation ad hoc network system model;

[0008] Step 1.1: Based on the aircraft density λ and earth radius R collected from the network side earth and aircraft height H, the spatial topology of the aeronautical ad hoc network is modeled as a radius of R = R earth +H's spherical Poisson point process model Φ. Based on the power law model information collected from the network side A large-scale power path loss model for wireless signals is established, where α is the path loss exponent and r is the propagation distance of the signal. Small-scale channel fading is modeled as Rayleigh fading.

[0009] Step 1.2: Transmit the time slot length T according to the aircraft configuration information s , the sensing frequency ζ and the sensing packet size K bits, the aircraft sensing environment process is modeled as a discrete Bernoulli packet arrival process. The aircraft transmitter adopts the first-come-first-served principle and sends the first packet in the cache queue with probability p. At the same time, the transmitter adopts a no-retransmission transmission strategy, that is, once the first packet is scheduled to be sent, it needs to be removed from the queue regardless of whether it is successfully transmitted.

[0010] Step 2: aircraft relay selection and perception data broadcast;

[0011] Step 2.1, set the transmission time slot T s It is divided into two parts, where the allocation ratio of the first part is η, which is used by the aircraft transmitter to broadcast the perception data to each candidate aircraft relay, and the allocation ratio of the second part is 1-η, and the remaining time slots are used by the aircraft relay to forward the correctly decoded perception data to the aircraft receiver.

[0012] Step 2.2, after information exchange between aircraft nodes or aircraft position information obtained from the ground control terminal, first, the aircraft transmitter can obtain the transceiver distance r0 through calculation. Then, calculate the distance r from other aircraft nodes to the transmitter i ,i=1,2…,M, where M is the number of other aircraft nodes, and select the aircraft nodes with a distance less than r0 as the nodes in the candidate relay set Ξ. Again, calculate the distance between the node in the candidate relay set Ξ and the receiver i=1,2…,M, remove the distance to the receiver The candidate relay nodes are further selected to select the candidate relay set Ξ. Finally, the nodes in the candidate relay set Ξ are sorted according to the distance difference to the transceiver. i=1,2…,M, are sorted in ascending order as the priority of relay forwarding selection.

[0013] Step 2.3, when the aircraft transmitter is scheduled to send the team head perception data packet, if the selected candidate relay set Ξ is an empty set, that is, there is no candidate relay, the transmitter uses all available bandwidth to send the team head perception data packet to the receiver in the entire transmission time slot, and then directly jumps to step 5 to implement the aircraft information transmission scheme. If the selected candidate relay set Ξ is a non-empty set, the transmitter uses all available bandwidth to broadcast the team head perception data packet to each node in the candidate relay set Ξ in the first part of the transmission time slot.

[0014] Step 3: frequency domain sub-channel division and perception data forwarding;

[0015] Step 3.1: Divide the total available bandwidth W into N sub-channels. When the number of nodes in the candidate relay set Ξ obtained in step 2.2 is N relay ≥N, the total available bandwidth W is evenly divided into N sub-channels, where the bandwidth of the sub-channel is W sub =W / N, and select N aircraft relays from the candidate relay set according to the priority order in step 2.2, and assign an orthogonal subchannel to each aviation relay. When the number of nodes in the candidate relay set Ξ obtained in step 2.2 is N relay <N, divide the total available bandwidth W into N relay sub-channels, N relay Each aircraft relay node is assigned an orthogonal subchannel, where the bandwidth of the subchannel is W sub =W / N relay .

[0016] Step 3.2, for the aircraft relay assigned with the orthogonal subchannel, if it can correctly decode the sensing data of the transmitter, the aircraft relay uses the assigned orthogonal subchannel to forward the sensing data packet to the receiver in the latter part of the transmission time slot. If the aircraft relay fails to correctly decode the sensing data of the transmitter, it remains silent and does not send data.

[0017] Step 3.3, if any aircraft relay can successfully forward the data packet, the receiver will feedback a confirmation signal, i.e., an ACK signal, to the transmitter, and the receiver will make a decision based on the current most recently received perception data packet. If all aircraft relays fail to forward the data packet, the receiver will feedback a NACK signal to the transmitter and still make a decision based on the last successfully received perception data packet.

[0018] Step 4: survivability performance evaluation and optimization;

[0019] Step 4.1, survivability performance evaluation;

[0020] Based on the aviation ad hoc network system model established in step 1 and the high-efficiency cooperative transmission method of joint distributed aircraft relay and frequency domain sub-channel division designed in steps 2 and 3, the analytical expression of information timeliness is established by solving the average peak information age, the network survivability is measured, and the number of sub-channel divisions and the time slot allocation ratio are optimized with the goal of minimizing the average peak information age, thereby enhancing the network survivability. The details are as follows:

[0021] When p≤ζ, the average peak information age is infinite, that is, When N relay = 0 and p>ζ, the average peak information age for:

[0022]

[0023] When p>ζ and N relay ≥1, mean peak information age for:

[0024]

[0025] Among them, N relay is the number of nodes in the candidate relay set Ξ, r0 represents the relative distance of the aircraft transceiver; r i and is the distance from the aircraft node in the candidate relay set Ξ in step 2.2 to the aircraft transmitter and the aircraft receiver respectively, ζ represents the environmental information perception frequency; T s represents the transmission time slot length; p represents the probability of data packet transmission in each time slot; Indicates the critical elevation angle where the interfering aircraft is located; Rearth is the radius of the Earth; R = R earth +H is the radius of the sphere where the aircraft is located; H is the altitude of the aircraft; K represents the bit size of the data packet; W is the communication bandwidth; represents the normalized noise power; α represents the path loss index; λ represents the aircraft density; η represents the allocation ratio of the transmission time slot; W sub is the spectrum bandwidth of the subchannel.

[0026] Step 4.2, optimizing survivability performance;

[0027] Set no less than two groups of different transmission time slot allocation ratios and sub-channel division numbers, and evaluate the average peak information age index according to the evaluation method of step 4.1; based on the analysis results obtained, select the transmission time slot allocation ratio and sub-channel division number corresponding to the minimized average peak information age index as the optimal parameter configuration, and as the final transmission time slot allocation ratio and sub-channel division number.

[0028] Step 5: Implement the information transmission plan for aviation aircraft;

[0029] If the screened candidate relay set Ξ is an empty set, the transmitter uses all available bandwidth W to send the head-of-line perception data packet to the receiver in the entire transmission time slot, and the receiver will be configured to a signal reception mode of full spectrum bandwidth and full time slot.

[0030] If the selected candidate relay set Ξ is a non-empty set, based on the optimal transmission time slot allocation ratio and the number of sub-channel divisions obtained by the evaluation in step 4, the aircraft transmitter feeds back to the aircraft relay and the aircraft receiver to adjust their respective signal reception and transmission modes. When the aircraft relay receives the parameter feedback information, it is configured as a signal reception mode of the full spectrum bandwidth in the first part of the time slots, and is configured as a signal transmission mode of the sub-channel spectrum bandwidth in the second part of the time slots. The aircraft receiver is configured as a signal reception mode of the full spectrum bandwidth in the second part of the time slots, and performs signal parallel processing and decoding according to the sub-channels.

[0031] The beneficial effects of the present invention are:

[0032] (1) The high-efficiency collaborative transmission method of the joint distributed aircraft relay and frequency domain sub-channel division proposed in the present invention can effectively combat the inherent challenges of aeronautical ad hoc networks such as long-distance path loss and earth obstruction through the method of relay forwarding. At the same time, the airspace diversity and frequency domain sub-channel division embodied by the distributed relay can effectively combat adverse factors such as wireless interference and long-term deep fading.

[0033] (2) The performance evaluation and optimization method proposed in the present invention can flexibly adjust the transmission time allocation ratio and the number of sub-channel divisions according to the actual scenario to minimize the average peak information age, enhance the timeliness of information transmission, and thus enhance the survivability of the network. In addition, the proposed performance evaluation method only needs to know the location of the aircraft transceiver and relay in the network, and does not need to know the real-time channel fading coefficient and the specific location of the interference source, thereby reducing the complexity of performance evaluation and optimization and the amount of interaction of control signaling. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of the network topology of the aviation ad hoc network of the present invention.

[0035] Figure 2 (a) is a flowchart of the transmitter side operation of the present invention.

[0036] Figure 2 (b) is a flowchart of the relay side working process of the present invention.

[0037] Figure 2 (c) is a flowchart of the receiver side work flow of the present invention.

[0038] Figure 3 (a) is the relationship curve between the average peak information age and the transmission time slot allocation ratio in step 4.

[0039] Figure 3 (b) is the relationship curve between the average peak information age and the packet perception frequency in step 4. DETAILED DESCRIPTION

[0040] The specific implementation of the present invention is described in detail below with reference to the accompanying drawings.

[0041] A time-efficient cooperative transmission method combining distributed aircraft relay and frequency domain sub-channel division includes the following steps:

[0042] Step 1: construct an aviation ad hoc network system model;

[0043] Step 1.1: Based on the aircraft density λ and earth radius R collected from the network side earth and aircraft height H, the spatial topology of the aeronautical ad hoc network is modeled as a radius of R = R earth +H spherical Poisson point process model Φ. Based on the power law model information collected from the network side A large-scale power path loss model for wireless signals is established, where α is the path loss exponent and r is the propagation distance of the signal. Small-scale channel fading is modeled as Rayleigh fading. Figure 1 The spatial topology of the aeronautical ad hoc network is shown in the figure, where x0 and y0 represent the aircraft transmitter and aircraft receiver respectively, and z i,i=1,2,…,M represents the i-th aircraft relay node.

[0044] Step 1.2: Transmit the time slot length T according to the aircraft configuration information s , perception frequency ζ and perception data packet size K bits, the aircraft perception environment process is modeled as a discrete Bernoulli data packet arrival process, that is, the aircraft perceives and generates an environmental state data packet with K information bits with probability ζ in each time slot, and assigns a timestamp to each data packet and stores it in the cache queue. The aircraft transmitter adopts the first-come-first-served principle. If the aircraft's cache queue is not empty, the data packet at the head of the queue is sent at the starting boundary of the time slot with a scheduling probability p, that is, the probability of sending the data packet. In other words, the aviation ad hoc network adopts the commonly used ALOHA strategy for data packet scheduling, and only sends one data packet in a time slot. At the same time, the aircraft transmitter adopts a transmission strategy without retransmission, that is, once the first data packet of the queue is scheduled to be sent, regardless of whether it is sent successfully, the data packet needs to be removed from the aircraft transmitter cache queue.

[0045] Step 2: aircraft relay selection and perception data broadcast;

[0046] Step 2.1, set the transmission time slot T s It is divided into two parts, where the allocation ratio of the first part is η, which is used by the aircraft transmitter to broadcast the perception data to each candidate aircraft relay, and the allocation ratio of the second part is 1-η, and the remaining time slots are used by the aircraft relay to forward the correctly decoded perception data to the aircraft receiver.

[0047] Step 2.2, after information exchange between aircraft nodes or aircraft position information obtained from the ground control terminal, first, the aircraft transmitter can obtain the transceiver distance r0 through calculation. Then, calculate the distance r from other aircraft nodes to the transmitter i ,i=1,2…,M, where M is the number of other aircraft nodes, and select the aircraft nodes with a distance less than r0 as the nodes in the candidate relay set Ξ. Again, calculate the distance between the node in the candidate relay set Ξ and the receiver i=1,2…,M, remove the distance to the receiver The candidate relay nodes are further selected to select the candidate relay set Ξ. Finally, the nodes in the candidate relay set Ξ are sorted according to the distance difference to the transceiver. i=1,2…,M, are sorted in ascending order as the priority of relay forwarding selection.

[0048] Step 2.3, when the aircraft transmitter is scheduled to send the head-of-line perception data packet, if the screened candidate relay set Ξ is an empty set, that is, there is no candidate relay, the transmitter uses all available bandwidth W to send the head-of-line perception data packet to the receiver in the entire transmission time slot. If the data packet is successfully transmitted, the receiver feeds back a confirmation signal, i.e., an ACK signal, to the transmitter, and the receiver will make a decision based on the current most recently received perception data packet. The successfully transmitted data packet refers to the link capacity C = Wlog (1 + SINR) from the transmitter x0 to the receiver y0 in a time slot length T s The size of the data packet is K bits, that is, C×T s >K, where represents the signal-to-interference-to-noise ratio of the link; r0 represents the relative distance of the aircraft transceiver; |x-y0| represents the distance from the interference transmitter x to the receiver y0; Φ represents the topological model of the aeronautical ad hoc network; Ω is the visible area of ​​the receiver y0 formed by the earth's shielding effect; and h x They represent the small-scale channel power fading factors from transmitter x0 and interference transmitter x to receiver y0 respectively; and represent the path loss from transmitter x0 and interference transmitter x to receiver y0 respectively; B x Q is a Bernoulli random variable with probability p being 1 and probability 1-p being 0 indicating whether transmitter x sends data; x represents the number of packets in the buffer queue of transmitter x; represents the normalized noise power. If the data packet transmission fails, it means that C×T s >K, the receiver feeds back a NACK signal to the transmitter and still makes decisions based on the last successfully received perception data packet.

[0049] If the selected candidate relay set Ξ is a non-empty set, the transmitter uses all available bandwidth W to broadcast the head-of-line sensing data packet to each node in the candidate relay set Ξ in the first part of the transmission time slot. i The link capacity C i =W log(1+SINR i ) in a previous part of the time slot length ηT s The size of the data packet is K bits, that is, C i ×ηT s >K, then it means relay z i Successfully decoded the sensing data packet transmitted by the aircraft transmitter. Represents transmitter x0 to relay z i The signal-to-interference-to-noise ratio of the link; r i Represents transmitter x0 to relay z iThe relative distance of |xz i | indicates the jammer x to the relay z i The distance; Φ represents the topological model of the aeronautical ad hoc network; Ω i It is a relay i The visible area formed by the earth's obstruction; and h x Represents transmitter x0 and jammer x to relay z respectively i The small-scale channel power fading factor; and Represents transmitter x0 and jammer x to relay z respectively i The path loss of B x Q is a Bernoulli random variable with probability p being 1 and probability 1-p being 0 indicating whether transmitter x sends data; x represents the number of packets in the buffer queue of transmitter x; represents the normalized noise power. If C×ηT is not satisfied s >K, then it means relay z i Failure to successfully decode the sensing data packet transmitted by the aircraft transmitter will prevent it from being a relay for forwarding data in the later part of the transmission time slot.

[0050] Step 3: frequency domain sub-channel division and perception data forwarding;

[0051] Step 3.1: Divide the total available bandwidth W into N sub-channels. relay ≥N, the total available bandwidth W is evenly divided into N sub-channels, where the bandwidth of the sub-channel is W sub =W / N, and select N aircraft relays from the candidate relay set according to the priority order in step 2.2, and assign an orthogonal subchannel to each aircraft relay. relay <N, divide the total available bandwidth W into N relay sub-channels, N relay Each aircraft relay node is assigned an orthogonal subchannel, where the bandwidth of the subchannel is W sub =W / N relay .

[0052] Step 3.2, for the aircraft relay assigned with the orthogonal subchannel, if it correctly decodes the sensing data of the transmitter, the aircraft relay uses the assigned orthogonal subchannel to forward the sensing data packet to the receiver in the latter part of the transmission time slot. If the aircraft relay fails to correctly decode the sensing data of the transmitter, it remains silent and does not send data.

[0053] Step 3.3, if any aircraft relay can successfully forward the data packet, the receiver will feedback a confirmation signal, i.e., an ACK signal, to the transmitter, and the receiver will make a decision based on the current most recently received perception data packet. If all aircraft relays fail to forward the data packet, the receiver will feedback a NACK signal to the transmitter and still make a decision based on the last successfully received perception data packet. The aircraft relay can successfully forward the data packet means that the relay z i The link capacity to receiver y0 In a later part of the time slot length (1-η)T s The size of the data packet K bits is sufficient to transmit in, Relay z i The signal-to-interference-and-noise ratio of the link to receiver y0; Relay z i The relative distance to the receiver y0; |x-y0| represents the distance from the interference transmitter x to the receiver y0; Φ represents the topological model of the aeronautical ad hoc network; Ω is the visible area of ​​the receiver y0 formed by the earth's obstruction; and h x Represents relay z i and the small-scale channel power fading factor from the interfering transmitter x to the receiver y0; and Represents relay z i and the path loss from the interfering transmitter x to the receiver y0; B x Q is a Bernoulli random variable with probability p being 1 and probability 1-p being 0 indicating whether transmitter x sends data; x represents the number of packets in the buffer queue of transmitter x; represents the normalized noise power. If it does not satisfy This means that the receiver y0 failed to successfully decode the aircraft relay z i The forwarded sensing packets.

[0054] Step 4: survivability performance evaluation and optimization;

[0055] Step 4.1, survivability performance evaluation;

[0056] Based on the aviation ad hoc network system model established in step 1 and the high-efficiency cooperative transmission method of joint distributed aircraft relay and frequency domain sub-channel division designed in steps 2 and 3, the analytical expression of information timeliness is established by solving the average peak information age, the network survivability is measured, and the number of sub-channel divisions and the time slot allocation ratio are optimized with the goal of minimizing the average peak information age, thereby enhancing the network survivability. The details are as follows:

[0057] The peak information age is defined as the maximum information age value that the current data packet can reach when the next data packet is successfully transmitted. The network survivability can be characterized from the timeliness of information, which can be decomposed into the end-to-end delay of the perceived data packet and the perceived interval time between two consecutive successful transmissions of data packets. (Reference: Inoue Y, Masuyama H, Takine T, et al. A general formula for the stationary distribution of the age of information and its application to single-server queues [J]. IEEE Transactions on Information Theory, 2019, 65 (12): 8305-8324.) Therefore, the average peak information age can also be decomposed into the average end-to-end transmission delay of the data packet and the average perceived interval time of consecutive successful transmissions.

[0058] Step 4.1.1, for the average end-to-end transmission delay of the data packet, according to the discrete Bernoulli data packet arrival process, ALOHA protocol and no retransmission scheme of the transmitter in step 1.2, the process of sensing the arrival and departure of the data packet from the transmitter can be modeled as a Geo / Geo / 1 queue model, where the arrival rate is the data packet sensing frequency ζ, and the service rate is the probability of data packet transmission p in each time slot. According to the queuing theory, the average end-to-end transmission delay is: When p>ζ, the average end-to-end transmission delay is (1-ζ)(p-ζ) -1 T s , when p≤ζ, the average end-to-end transmission delay of the data packet tends to ∞; (Reference: Atencia I and Moreno PA discrete-time GEO / G / 1 retrial queue with general retrial times [J]. Queueing Systems, 2004, 48: 5-21.)

[0059] Step 4.1.2, for the perception time interval X of continuous successful transmission inter , under the given aeronautical ad hoc network topology Φ, the conditional mean of the perception time interval of continuous successful transmission is The unconditional mean of the perception time interval of continuous successful transmission is obtained as Where T s is the transmission slot length, ζ is the packet sensing frequency, and is the probability of successful end-to-end transmission of a data packet under a given aeronautical ad hoc network topology Φ. (Reference: Martin Haenggi. The Local Delay in Poisson Networks [J]. IEEE Transactions on Information Theory, 2013, 59 (3): 1788-1802.)

[0060] When N relay = 0, the aircraft transmitter communicates directly with the aircraft receiver without relaying. The probability of successful end-to-end transmission of a data packet under the given aeronautical ad hoc network topology Φ is It is expressed as:

[0061]

[0062] Where Ω is the visible area of ​​the receiver y0 blocked by the earth, K is the bit size of the data packet; W is the communication bandwidth; T s is the transmission time slot length; r0 represents the relative distance of the aircraft transceiver; ζ represents the packet sensing frequency; represents the normalized noise power; α represents the path loss index; x and y0 represent the locations of the interference transmitter and receiver, respectively; represents the path loss from the interference transmitter x to the receiver y0. Furthermore, the average perception interval time of continuous successful transmission can be obtained as

[0063]

[0064] When N relay When >1, the aircraft transmitter needs to communicate directly with the aircraft receiver through a relay. The lower bound of the average perception interval time of continuous successful transmission can be obtained by using Jensen's inequality:

[0065]

[0066] in The probability of unconditional end-to-end successful transmission is:

[0067]

[0068] Where P1(r i )and are the distances from the aircraft transmitter x0 to the relay z. i The probability of successful transmission of the link and the relay z i The probability of successful transmission of the link y0 to the aircraft receiver, r i and are the distances from the aircraft nodes in the candidate relay set Ξ in step 2.2 to the aircraft transmitter and the aircraft receiver respectively.

[0069] Step 4.1.3, considering the average end-to-end transmission delay of data packets and the average perceived interval time of consecutive successful transmissions, we can get the analytical expression of the average peak information age. The details are as follows:

[0070] When p≤ζ, the average peak information age is infinite, that is,

[0071] When p>ζ and N relay =0, the average peak information age is:

[0072]

[0073] When p>ζ and N relay When ≥1, the average peak information age is:

[0074]

[0075] Among them, N relay is the number of nodes in the candidate relay set Ξ, r0 represents the relative distance of the aircraft transceiver; r i and is the distance from the aircraft node in the candidate relay set Ξ in step 2.2 to the aircraft transmitter and the aircraft receiver respectively, ζ represents the environmental information perception frequency; T s represents the transmission time slot length; p represents the probability of data packet transmission in each time slot; Indicates the critical elevation angle where the interfering aircraft is located; R earth is the radius of the Earth; R = R earth +H is the radius of the sphere where the aircraft is located; H is the altitude of the aircraft; K represents the bit size of the data packet; W is the communication bandwidth; represents the normalized noise power; α represents the path loss index; λ represents the aircraft density; η represents the allocation ratio of the transmission time slot; W sub is the spectrum bandwidth of the subchannel.

[0076] Step 4.2: Optimizing survivability performance

[0077] Set L different transmission time slot allocation ratios η1, η2, ..., η between (0, 1) L ,L>1, the values ​​of sending probability are p1,p2,...,p L ,L>1 and the values ​​of packet sensing frequency ζ1,ζ2,...,ζ L ,L>1, in [1,N max ] set L different sub-channel division numbers N1, N2, ..., NL ,L>1, where N max It is the maximum number of sub-channels that can be divided and is set by hardware design constraints. The average peak information age index is evaluated according to the evaluation method of step 4.1, and based on the analysis results obtained, the transmission time slot allocation ratio, number of sub-channel divisions, transmission probability and data packet sensing frequency corresponding to the minimum average peak information age index are selected as the optimal parameter configuration and used as the final parameter configuration.

[0078] An example is given as a reference, in which the aircraft can obtain some system parameters from its own configuration, transceiver interaction and network side as follows: Earth radius R earth =6371km, road loss index α = 2.5, aircraft flight altitude H = 40km, aircraft density λ = 10 6 / (4π(R earth +H) 2 ), relative distance between aircraft transceivers r0 = 5 km, communication bandwidth W = 5 MHz, data packet size K = 1000, scheduling probability p = 1, normalized noise power There are 5 candidate relays, and the distances from each relay to the transmitter are 2km, 2.2km, 2.4km, 2.6km, and 2.5km, and the distances from each relay to the receiver are 3.2km, 3km, 2.8km, 2.6km, and 2.6km, respectively. Figure 3 (a) Given a packet perception frequency ζ = 0.9, the transmission time slot allocation ratio is changed from 0.01 to 0.99, and a value is selected every 0.01 to calculate the corresponding average peak information age, which considers selecting N = 1, 2, 3 relays from the candidate relay set for forwarding and N = 0 relays, that is, direct transmission. Therefore, in this example, for example, when the transmission time slot ratio is η = 0.5 and N = 1, the minimum average peak information age value obtained by using the relay forwarding scheme is 0.764ms. Figure 3 (b) Given a transmission time slot allocation ratio η = 0.5, the packet sensing frequency is changed from 0.01 to 0.99, and a value is selected every 0.01 to calculate the corresponding average peak information age, where N = 1, 2 relays are selected from the candidate relay set for forwarding and N = 0 relays, that is, direct transmission. Therefore, in this example, for example, when the packet sensing frequency configuration satisfies the condition of ζ ≥ 0.78 per time slot, the average peak information age of the relay forwarding scheme using N = 1 reaches the minimum.

[0079] Step 5: Implement the information transmission plan for aviation aircraft;

[0080] Based on the transmission time slot allocation ratio, number of sub-channel divisions, transmission probability and packet sensing frequency evaluated in step 4, the aircraft transmitter and receiver perform system parameter configuration and perform information transmission to minimize PAoI. The details are as follows:

[0081] If the screened candidate relay set Ξ is an empty set, the transmitter uses all available bandwidth W to send the head-of-line perception data packet to the receiver in the entire transmission time slot, and the receiver will be configured to a signal reception mode of full spectrum bandwidth and full time slot.

[0082] If the selected candidate relay set Ξ is a non-empty set, based on the optimal transmission time slot allocation ratio and the number of sub-channel divisions obtained by the evaluation in step 4, the aircraft transmitter feeds back to the aircraft relay and the aircraft receiver to adjust their respective signal reception and transmission modes. When the aircraft relay receives the parameter feedback information, it is configured as a signal reception mode of the full spectrum bandwidth in the first part of the time slots, and is configured as a signal transmission mode of the sub-channel spectrum bandwidth in the second part of the time slots. The aircraft receiver is configured as a signal reception mode of the full spectrum bandwidth in the second part of the time slots, and performs signal parallel processing and decoding according to the sub-channels.

[0083] From the above description, it can be seen that the high-efficiency collaborative transmission method of the present invention combining distributed aircraft relay and frequency domain sub-channel division is significantly different from the existing transmission method based on information retransmission. The relay forwarding in the proposed collaborative transmission method can effectively combat the adverse factors of long-distance path loss and earth obstruction, and the spatial domain diversity and frequency domain sub-channel division in the distributed relay collaborative transmission method can effectively combat wireless interference and long-term deep attenuation, avoiding the use of data retransmission methods and reducing end-to-end transmission delays. In addition, the proposed performance evaluation method provides a mapping relationship between each system parameter and the average peak information age, and does not need to rely on large-scale system simulation methods, so it does not need to occupy too many storage and computing resources.

[0084] The above-described embodiments merely express the implementation methods of the present invention, but they cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A high-efficiency collaborative transmission method for aviation ad hoc networks, characterized in that: The high-efficiency cooperative transmission method firstly constructs an aviation ad hoc network system model according to network information; secondly, divides the transmission time slot into two parts, selects an aircraft whose forwarding distance is less than the distance of the aircraft transceiver as a candidate relay, and the transmitter uses all available spectrum to complete the data broadcast transmission process to each candidate relay in the first part of the time slot; Third, the available spectrum is divided into multiple sub-channels. Each aircraft relay that correctly decodes the perceived data will select an orthogonal sub-channel to complete the data forwarding transmission to the receiver in the latter part of the time slot. Fourth, based on the aviation ad hoc network system model, an analytical expression for solving the average peak information age is established, and the performance of different time slot allocation ratios and sub-channel division numbers is evaluated and the optimal parameters are found. Finally, based on the optimization results, a distributed relay forwarding solution for aircraft is implemented. The following steps are involved: Step 1: construct an aviation ad hoc network system model; Step 2: aircraft relay selection and perception data broadcast; Step 3: frequency domain sub-channel division and perception data forwarding; Step 4: Survivability performance evaluation and optimization.

2. The high-efficiency collaborative transmission method for aeronautical ad hoc networks according to claim 1, characterized in that: The step 1 is specifically as follows: Step 1.1: Based on the aircraft density λ and earth radius R collected from the network side earth and aircraft height H, the spatial topology of the aeronautical ad hoc network is modeled as a radius of R = R earth +H spherical Poisson point process model Φ; according to the power law model information collected from the network side l(r) = r -α A large-scale power path loss model for wireless signals is established, where α is the path loss exponent and r is the propagation distance of the signal; small-scale channel fading is modeled as Rayleigh fading; Step 1.2: Transmit the time slot length T according to the aircraft configuration information s , perception frequency ζ and perception packet size K bits, the aircraft perception environment process is modeled as a discrete Bernoulli packet arrival process; the aircraft transmitter adopts the first-come-first-served principle and sends the first packet in the cache queue with probability p; at the same time, the transmitter adopts a no-retransmission transmission strategy.

3. The high-efficiency collaborative transmission method for aviation ad hoc networks according to claim 2, characterized in that: The step 2 is specifically as follows: Step 2.1, set the transmission time slot T s It is divided into two parts, where the first part is allocated with a ratio of n for the aircraft transmitter to broadcast the sensing data to each candidate aircraft relay, and the second part is allocated with a ratio of 1-n for the remaining time slots for the aircraft relay to forward the correctly decoded sensing data to the aircraft receiver; Step 2.2, obtain the aircraft position information. First, the aircraft transmitter calculates the transceiver distance as r0; then, calculates the distance r from other aircraft nodes to the transmitter i ,i=1,2…,M, where M is the number of other aircraft nodes, and the aircraft nodes with a distance less than r0 are selected as nodes in the candidate relay set Ξ; Again, calculate the distance between the node and the receiver in the candidate relay set Ξ Remove distance to receiver The candidate relay nodes are further selected to select the candidate relay set Ξ; finally, the nodes in the candidate relay set Ξ are selected according to the distance difference to the transceiver. Sort in ascending order as the priority for relay forwarding selection; Step 2.3, when the aircraft transmitter is scheduled to send the head-of-team perception data packet, if the screened candidate relay set Ξ is an empty set and there is no candidate relay, the transmitter uses all available bandwidth W to send the head-of-team perception data packet to the receiver in the entire transmission time slot, and then jumps directly to step five to implement the aircraft information transmission plan; if the screened candidate relay set Ξ is a non-empty set, the transmitter uses all available bandwidth W to broadcast the head-of-team perception data packet to each node in the candidate relay set Ξ in the first part of the transmission time slot.

4. The high-efficiency collaborative transmission method for aviation ad hoc networks according to claim 3, characterized in that: In the step 2.2, the aircraft position information is obtained through information interaction between aircraft nodes or from the ground control terminal.

5. The high-efficiency collaborative transmission method for aeronautical ad hoc networks according to claim 3, characterized in that: The step three is specifically as follows: Step 3.1, according to the number of nodes in the candidate relay set Ξ obtained in step 2.2, the total available bandwidth W is divided into N sub-channels; Step 3.2, for the aircraft relay assigned with the orthogonal subchannel, if it can correctly decode the sensing data of the transmitter, the aircraft relay uses the assigned orthogonal subchannel to forward the sensing data packet to the receiver in the latter part of the transmission time slot; if the aircraft relay fails to correctly decode the sensing data of the transmitter, it remains silent and does not send data; Step 3.3, if any aircraft relay can successfully forward the data packet, the receiver will feedback a confirmation signal, i.e., an ACK signal, to the transmitter, and the receiver will make a decision based on the current most recently received perception data packet; if all aircraft relays fail to forward the data packet, the receiver will feedback a NACK signal to the transmitter, and will still make a decision based on the last successfully received perception data packet.

6. The high-efficiency collaborative transmission method for aeronautical ad hoc networks according to claim 5, characterized in that: The step 3.1 is specifically as follows: When the number of nodes N in the candidate relay set Ξ obtained in step 2.2 relay ≥N, the total available bandwidth W is evenly divided into N sub-channels, where the bandwidth of the sub-channel is W sub =W / N, and select N aircraft relays from the candidate relay set according to the priority order in step 2.2, and assign an orthogonal subchannel to each aviation relay; when the number of nodes in the candidate relay set Ξ obtained in step 2.2 is N relay <N, divide the total available bandwidth W into N relay sub-channels, N relay Each aircraft relay node is assigned an orthogonal subchannel, where the bandwidth of the subchannel is W sub =W / N relay .

7. The high-efficiency collaborative transmission method for aeronautical ad hoc networks according to claim 5, characterized in that: The step 4 is specifically as follows: Step 4.1, survivability performance evaluation; Based on the aviation ad hoc network system model established in step 1 and the high-efficiency cooperative transmission method of joint distributed aircraft relay and frequency domain sub-channel division designed in steps 2 and 3, the analytical expression of information timeliness is established by solving the average peak information age to measure the network survivability, and the number of sub-channel divisions and the time slot allocation ratio are optimized with the goal of minimizing the average peak information age, thereby enhancing the network survivability; Step 4.2, optimizing survivability performance; Set no less than two groups of different transmission time slot allocation ratios and sub-channel division numbers, and evaluate the average peak information age index according to the evaluation method of step 4.1; based on the analysis results obtained, select the transmission time slot allocation ratio and sub-channel division number corresponding to the minimized average peak information age index as the optimal parameter configuration, and as the final transmission time slot allocation ratio and sub-channel division number.

8. The high-efficiency collaborative transmission method for aviation ad hoc networks according to claim 7, characterized in that: The step 4.1 is as follows: When p≤ζ, the average peak information age is infinite, that is, When N relay = 0 and p>ζ, the average peak information age for: When p>ζ and N relay ≥1, mean peak information age for: Among them, N relay is the number of nodes in the candidate relay set Ξ, r0 represents the relative distance of the aircraft transceiver; r i and is the distance from the aircraft node in the candidate relay set Ξ in step 2.2 to the aircraft transmitter and the aircraft receiver respectively, ζ represents the environmental information perception frequency; T s represents the transmission time slot length; p represents the probability of data packet transmission in each time slot; Indicates the critical elevation angle where the interfering aircraft is located; R earth is the radius of the Earth; R = R earth +H is the radius of the sphere where the aircraft is located; H is the altitude of the aircraft; K represents the bit size of the data packet; W is the communication bandwidth; represents the normalized noise power; α represents the path loss index; λ represents the aircraft density; η represents the allocation ratio of the transmission time slot; W sub is the spectrum bandwidth of the subchannel.

9. The high-efficiency collaborative transmission method for aviation ad hoc networks according to claim 7, characterized in that: The step five is specifically as follows: If the selected candidate relay set Ξ is an empty set, the transmitter uses all available bandwidth W to send the head-of-line sensing data packet to the receiver in the entire transmission time slot, and the receiver will be configured to the signal reception mode of full spectrum bandwidth and full time slot; If the screened candidate relay set Ξ is a non-empty set, based on the optimal transmission time slot allocation ratio and the number of sub-channel divisions obtained by evaluation in step 4, the aircraft transmitter feeds back to the aircraft relay and the aircraft receiver to adjust their respective signal reception and transmission modes; when the aircraft relay receives the parameter feedback information, it is configured as a signal reception mode of the full spectrum bandwidth in the first part of the time slots, and is configured as a signal transmission mode of the sub-channel spectrum bandwidth in the second part of the time slots, and the aircraft receiver is configured as a signal reception mode of the full spectrum bandwidth in the second part of the time slots, and performs signal parallel processing and decoding according to the sub-channels.

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