Channel opportunity scheduling method

Abstract

The invention discloses a channel opportunity scheduling method, which is characterized in that based on a social trust relationship between user pairs, communication nodes with mutual deep trust can serve as relay nodes of the opposite sides at the same time, and space-time diversity and relay diversity gain are fully utilized. In the second-level trusted cooperative relay detection, the optimal relay node set is selectively detected, the time overhead of relay detection is associated with the detection income, the relay set with the maximum expected income is selected for detection, the trusted cooperative relay nodes with better channel conditions are detected under the limited detection overhead, and unnecessary detection overhead is avoided. According to the method, modeling is carried out on the social trust relationship of user pairs in wireless networking, meanwhile, two conditions of relay untrusted eavesdropping and communication node deep trust cooperation are considered, network trust is divided into three levels, and the method conforms to existing flexible and changeable unsafe networks such as temporary networking, emergency networks and unmanned aerial vehicle clusters which are lack of node security verification; and the method has relatively high flexibility and applicability.

Description

Technical Field

[0001] The present invention relates to the field of network protocols and physical layer security technology in wireless communication technology, and in particular to a channel opportunity scheduling method with three-level decision-making based on multi-level social trust relationships. Background Art

[0002] The cooperative channel opportunistic scheduling in distributed networks mainly includes the channel sensing access modeling and statistical optimization methods under the two relay point working modes of controlled and autonomous relay points. Among them, mathematical modeling is carried out based on the stopping optimization theory, and a full sensing and access statistical decision method for relay channels under the relay resource controlled mode is proposed. In view of the linear increase of the relay channel sensing overhead in the controlled mode with the number of relay points, a full distributed channel sensing access method under the relay resource autonomous mode is studied, and a mathematical modeling method based on the double-order stopping optimization method is proposed. A fully distributed statistical decision optimization method of user channel competition sensing and front-hop broadcast-multi-relay point distributed sensing and back-hop forwarding is established, which has the statistical optimality of network throughput. However, for the scenario of untrusted relays, the existing research work is still in the primary stage. In the published papers, for the scenario with an untrusted relay, the sink-assisted cooperative interference is combined with the cooperative channel opportunistic scheduling of multiple user pairs for the first time, and a secure channel opportunistic scheduling method is proposed, but it does not explain the scenario of multiple untrusted relays, and does not consider the mutual cooperation between user pairs, and the utilization of multi-relay cooperative gain is not sufficient.

[0003] It can be seen that the coordinated channel access opportunity scheduling method in the prior art has the following three main defects:

[0004] 1. The node role is single. The network generally only considers relay nodes and user pairs. Relay nodes only forward signals as relays, and user nodes access the channel only when they get the channel access opportunity, resulting in a large number of user pairs being idle when they do not access the channel.

[0005] 2. It does not take into account the potential social relationships within the network, where there may be further deep trust relationships between user pairs.

[0006] 3. It does not consider secure transmission under multiple untrusted relays, that is, other physical layer security transmission methods need to be adopted to prevent untrusted relays from eavesdropping on the network. Summary of the invention

[0007] In view of the above problems, the present invention provides a channel opportunity scheduling method for overcoming the above problems or at least partially solving the above problems. The method is used for performing distributed channel detection and secure access decision in a heterogeneous wireless cooperative network composed of multiple source-destination pairs.

[0008] The present invention provides the following scheme:

[0009] A channel opportunity scheduling method, comprising:

[0010] Network description: The heterogeneous wireless collaborative network described in the present invention is composed of multiple source-destination pairs, referred to as user pairs, and multiple untrusted relays. The untrusted relays will eavesdrop when the source of the user pair sends data, resulting in data leakage. In order to suppress its eavesdropping, in relay mode, when the source sends data, the sink will synchronously send an interference signal to interfere with the untrusted relay. On this basis, there is a deep trust relationship between user pairs (this relationship may be derived from previous data transmission, user social relationships, transmission tasks, etc.). The trust relationships of all user pairs constitute a social trust network. Deeply trusted user pairs can relay and forward for each other when the other party transmits data, that is, they exist as potential relays. Assume that there are K user pairs, represented as the set of user pairs The source index is s1,...,s k ,...,s K , the destination index is d1,...,d k ,...,d K , there are L untrusted relay nodes, represented as the untrusted relay set The jth untrusted relay index is r j ; The set of trusted cooperative user pairs for each communication pair k is A k , then the cooperative trust relationship of the network is expressed as

[0011] Channel scheduling process:

[0012] When each channel contention starts, all user pairs compete and access the shared channel in a distributed manner to achieve time-division data transmission.

[0013] During the channel contention process, if there is only one source s k Sending an RTS contention packet, the source wins the channel and is called the winning source, which corresponds to the cooperative relay set A k All source and sink nodes in s are willing to provide relay assistance for their data transmission. By receiving this RTS, all other nodes (source, sink and untrusted relay) can obtain the channel from s through channel estimation. k to its own channel SNR, that is, the node Get the first jump Destination k Get the direct channel SNRγ k . Destination k Can make first-level decisions. First-level decisions include:

[0014] ①Stop and connect. d k Send a CTS packet, so that the source sk At rate Access the direct channel.

[0015] ② Give up access. k Send a CTS packet to make all sources compete for the channel again.

[0016] ③Detect untrusted relays.

[0017] Destination k We choose to further detect all untrusted relays to obtain the SNR of the relay and eavesdropping channels, and make further decisions based on the information after detection. k Send a CTS packet, and let L untrusted relay nodes reply RTS in turn. The RTS of the reply contains By receiving the node RTS,d k The second hop can be estimated Detection time τ L =τ C +L·τ R After all L RTSs are received, d k That is, get the two hops of all untrusted relay links And calculate the maximum safe transmission rate of the relay link d k Second-level decisions can be made. Second-level decisions include:

[0018] ①Stop and access. For the optional relay set d k The method with a higher security transmission rate is preferred in the direct link and the cooperative interference link, and a CTS packet is sent to the source s k Transmit on the preferred link at the corresponding rate, and the transmission time is

[0019] ② Give up access. k Send a CTS packet to make all sources compete for the channel again.

[0020] ③Detect trusted cooperative relay.

[0021] Destination k Select the cooperative relays to further explore their social trust relationship, represented as a set And make further decisions based on the information after detection, J * is the optimal number of detection relays. Similar to untrusted relay detection, d k Send a CTS packet to collect The nodes in the The RTS of the reply contains By receiving the node RTS,d k The second hop can be estimated Detection time After that, all J * RTS received, d k Get the collection Two-hop SNR of all node relay links in And calculate the maximum safe transmission rate of the relay link Destination k Can make third-level decisions, including:

[0022] ①For optional relay sets Destination k The method with a higher security transmission rate is preferred in the direct link and the cooperative interference link, and a CTS packet is sent to the source s k Transmit on the preferred link at the corresponding rate, and the transmission time is

[0023] ② Abandon access. k Send a CTS packet to make all sources compete for the channel again.

[0024] After a single access transmission ends, all signal sources restart the next round of channel contention, and each channel contention-access process is independent of each other. Figure 3 Given a signal from source s k Schematic diagram of the signaling process from winning the channel to accessing the cooperative interference link assisted by the trusted cooperative relay after the third-level decision.

[0025] For the above channel scheduling process, the above three-level scheduling process based on real-time calculation of local information is simplified through mathematical reasoning and statistical calculation, so that the first two levels of decision-making process are simplified to a decision-making process based on threshold comparison. The decision threshold can be obtained by offline calculation of channel statistical information, which does not occupy the online channel transmission time, reduces the complexity of online calculation, and maximizes the channel utilization. The threshold calculation process can refer to the "Specific Implementation Method", and the threshold-based channel scheduling method can be described as the following steps:

[0026] Step 1: Based on a given social trust network The characteristic parameters are obtained based on the statistics of the distributed wireless network channels, and the average security throughput of the system is obtained through offline iterative calculation. Optimal decision level threshold vector User Classification Collection The social trust network includes a heterogeneous wireless collaborative network consisting of multiple information source and information sink pairs with a three-level trust relationship;

[0027] Step 2: At the beginning of the mini-slot of duration δ, all sources send RTS packets with the same probability P0 to independently compete for the channel;

[0028] Step 3: Sink k According to the calculation result of step 1, determine the destination d k Which category does the user k belong to? Go to step 4; otherwise Go to step 5;

[0029] Step 4: If the channel signal-to-noise ratio Then the destination k Select the direct connection mechanism and send a CTS packet. k At the maximum achievable rate Access direct channel, duration τ d , after a single transmission is completed, return to step 2; otherwise, the destination d k Give up access and send a CTS packet, compete again in the next time slot, and return to step 2;

[0030] Step 5: If the channel signal-to-noise ratio Then the destination k Give up access and send CTS data packet, compete again in the next time slot, and return to step 2; if the channel signal-to-noise ratio Then the destination k Select the direct connection mechanism and send a CTS packet. k Then at the maximum achievable rate Access direct channel, duration τ d , after a single transmission is completed, return to step 2; otherwise, go to step 6;

[0031] Step 6: Sink k Select to detect all untrusted relays and send CTS packets. L untrusted relays then reply with RTS packets in turn. The detection time is τ L After that, the destination k Obtain the SNRs of the cooperative two-hop link of the untrusted relay and calculate the secure transmission rate of the direct access mechanism access and the secure transmission rate of relay-assisted and cooperative interference access mechanisms under the assistance of untrusted relays make If the user Go to step 7, otherwise the user Go to step 8;

[0032] Step 7: If Then the destination k Decide to stop and send CTS packets if Then the destination k Select the direct connection mechanism, source s k After receiving the CTS packet, the maximum achievable rate Access direct channel, duration After a single transmission is completed, return to step 2, otherwise, the destination d k Select the relay-assisted and cooperative interference access mechanism, the source s k After receiving the CTS packet, the maximum achievable rate Access channel, duration forward In time, source s k and Xin Su k Broadcast data and interference signals separately, then Time, untrusted relay To the hostel k Amplify and forward the received data packet, and return to step 2 after the single transmission is completed; otherwise Destination k Give up access and send a CTS packet, compete again in the next time slot, and return to step 2;

[0033] Step 8: Calculate the optimal number of trusted cooperative relay detections J * ; Traverse J = 1,…,|A k |, calculate the difference function like Then J * = J, end the traversal; otherwise J * =|A k |, the optimal detection relay node set is Calculate the benefits of detecting trusted cooperative relays Go to step 9;

[0034] Step 9: If Then the destination k Select Stop and send CTS packet to return to step 7; if Then the destination k Give up access and send CTS data packet, compete again in the next time slot, and return to step 2; otherwise, the destination d k Select Probe J * trusted cooperative relay and send CTS packets, the collection The trusted relays in the network then reply to the RTS packets one by one, detecting the time After that, the destination k Get a collaborative two-hop link with a trusted relay Calculate the secure transmission rate of relay-assisted and cooperative interference access mechanisms under trusted relay assistance Go to step 10;

[0035] Step 10: Compare If the size The maximum, then the destination d k Select the direct connection mechanism, source s k After receiving the CTS packet, the maximum achievable rate Access direct channel, duration if The maximum, then the destination d k Select the relay-assisted and cooperative interference access mechanism, the source s k After receiving the CTS packet, the maximum achievable rate Access channel, duration forward In time, source s k and Xin Su k Broadcast data packets and interference respectively, then Time, untrusted or trusted cooperative relay To the hostel k Amplify and forward the received data packet, and return to step 2 after the single transmission is completed; otherwise Maximum, sink d k Give up access and send a CTS packet, compete again in the next time slot, and return to step 2.

[0036] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0037] A channel opportunity scheduling method provided by an embodiment of the present invention is based on the social trust relationship between user pairs. Communication nodes that deeply trust each other can simultaneously serve as each other's relay nodes, which increases role diversity and makes full use of spatiotemporal diversity and relay diversity gain. In the second-level trusted cooperative relay detection, the optimal set of relay nodes is selectively detected, the time overhead of detecting relays is associated with the detection benefit, and the relay set with the largest expected benefit is selected for detection. Under limited detection overhead, trusted cooperative relay nodes with better channel conditions are detected to avoid unnecessary detection overhead. According to the actual situation of the wireless communication network, the social trust relationship of user pairs in the wireless networking is modeled, and the two situations of untrusted relay eavesdropping and deep trust cooperation of communication nodes are considered at the same time. The network trust is divided into three levels, which conforms to the existing temporary networking, emergency network, drone clusters and other flexible and unsafe networks that lack node security verification, and have strong flexibility and applicability.

[0038] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0040] Figure 1 is a flow chart of a channel opportunity scheduling method provided by an embodiment of the present invention;

[0041] Figure 2 is a schematic diagram of a social relationship network model provided by an embodiment of the present invention;

[0042] Figure 3 It is a schematic diagram of the contention-detection-access signaling process provided by an embodiment of the present invention;

[0043] Figure 4 It is a schematic diagram of the network node topology and social trust network structure provided by an embodiment of the present invention;

[0044] Figure 5 This is a comparison result diagram of the impact of channel coherence time on the security transmission performance of different strategies provided by an embodiment of the present invention;

[0045] Figure 6 This is a comparison result diagram of the impact of the interruption threshold provided by an embodiment of the present invention on the security transmission performance of different strategies. DETAILED DESCRIPTION

[0046] The technical scheme in the embodiment of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiment of the present invention. Obviously, the described embodiment is only a part of the embodiment of the present invention, not all of the embodiments. Based on the embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0047] See also Figure 1 , is a channel opportunity scheduling method provided by an embodiment of the present invention, such as Figure 1 As shown, the method may include:

[0048] Step 1: Based on a given social trust network, obtain characteristic parameters according to the distributed wireless network channel statistics, and obtain the system average security throughput through offline iterative calculation Optimal decision level threshold vector User Classification Collection The social trust network includes a heterogeneous wireless collaborative network consisting of multiple information source and information sink pairs with a three-level trust relationship;

[0049] In specific implementation, the embodiments of the present invention can provide an optimal system average security throughput. It is defined as the unique solution that satisfies the following equation:

[0050]

[0051] Where: K represents the number of source and sink pairs, τ d represents the channel coherence time, represents the safe transmission rate under direct channel transmission, n represents the number of observations, represents the expected revenue function of all untrusted relays, γ represents the signal-to-noise ratio, and τ0 represents the average time of a single observation.

[0052] Furthermore, the average time τ0 of a single observation is expressed as follows:

[0053]

[0054] Where: τ R Indicates the time to transmit the RTS packet, τ C represents the time to transmit the CTS data packet, K represents the number of source and sink pairs, δ represents the duration of the idle time slot, τ R Indicates the time when the conflict occurs, Kp0(1-p0) K-1 The total number of channel contentions experienced by a single observation follows the parameter.

[0055] The optimal decision level threshold vector Defined as:

[0056] Distribution as equation and The only solution of There is no solution with γ>0, so let

[0057] The user classification set Defined as:

[0058] For a given set of users Untrusted Relay Collection and social trust network A={A1,A1,…A K＝}, the user classifies k as follows:

[0059] If |A k |=0, Then the user has a first-level decision structure for k, which belongs to the classification set

[0060] If |A k |=0, Then the user has a secondary decision structure for k, belonging to the classification set

[0061] If |A k |>0, Then the user has a first-level decision structure for k, which belongs to the classification set

[0062] If |A k |>0, Then the user has a three-level decision structure for k, belonging to the classification set

[0063] Step 2: At the beginning of the mini-slot of duration δ, all sources send RTS packets with the same probability P0 to independently compete for the channel;

[0064] Step 3: Sink k According to the calculation result of step 1, determine the destination d k Which category does the user k belong to? Go to step 4; otherwise Go to step 5;

[0065] Step 4: If the channel signal-to-noise ratio Then the destination k Select the direct connection mechanism and send a CTS packet. k At the maximum achievable rate Access direct channel, duration τ d , after a single transmission is completed, return to step 2; otherwise, the destination d k Give up access and send a CTS packet, compete again in the next time slot, and return to step 2;

[0066] In specific implementation, the embodiment of the present invention can provide a signal source s k Maximum achievable rate It is expressed by the following formula:

[0067]

[0068] Where: γ k represents the signal-to-noise ratio of the direct channel, D k Indicates k and d k The straight-line distance between them, α represents the channel fading depth, h k represents the small-scale fading parameter and its mean is A negative exponential random distribution.

[0069] Step 5: If the channel signal-to-noise ratio Then the destination kGive up access and send CTS data packet, compete again in the next time slot, and return to step 2; if the channel signal-to-noise ratio Then the destination k Select the direct connection mechanism and send a CTS packet. k Then at the maximum achievable rate Access direct channel, duration τ d , after a single transmission is completed, return to step 2; otherwise, go to step 6;

[0070] Step 6: Sink k Select to detect all untrusted relays and send CTS packets. L untrusted relays then reply with RTS packets in turn. The detection time is τ L After that, the destination k Obtain the SNRs of the cooperative two-hop link of the untrusted relay and calculate the secure transmission rate of the direct access mechanism access and the secure transmission rate of relay-assisted and cooperative interference access mechanisms under the assistance of untrusted relays make If the user Go to step 7, otherwise the user Go to step 8;

[0071] In specific implementation, the embodiment of the present invention can provide a secure transmission rate of direct access mechanism access It is expressed by the following formula:

[0072]

[0073] Where: Indicates the source k The maximum achievable rate, Indicates the maximum eavesdropping rate.

[0074] Secure transmission rate of relay-assisted and cooperative interference access mechanisms under untrusted relay assistance It is expressed by the following formula:

[0075]

[0076] Where: Indicates the maximum achievable transmission rate of an untrusted relay link. Indicates the eavesdropping rate of the relay link.

[0077] Step 7: If Then the destination k Decide to stop and send CTS packets if Then the destination k Select the direct connection mechanism, source s k After receiving the CTS packet, the maximum achievable rate Access direct channel, duration After a single transmission is completed, return to step 2, otherwise, the destination d k Select the relay-assisted and cooperative interference access mechanism, the source s k After receiving the CTS packet, the maximum achievable rate Access channel, duration forward In time, source s k and Xin Su k Broadcast data and interference signals separately, then Time, untrusted relay To the hostel k Amplify and forward the received data packet, and return to step 2 after the single transmission is completed; otherwise Destination k Give up access and send a CTS packet, compete again in the next time slot, and return to step 2;

[0078] Step 8: Calculate the optimal number of trusted cooperative relay detections J * ; Traverse J = 1,…,|A k |, calculate the difference function like Then J * = J, end the traversal; otherwise J * =|A k |, the optimal detection relay node set is Calculate the benefits of detecting trusted cooperative relays Go to step 9;

[0079] Step 9: If Then the destination k Select Stop and send CTS packet to return to step 7; if Then the destination k Give up access and send CTS data packet, compete again in the next time slot, and return to step 2; otherwise, the destination d k Select Probe J * trusted cooperative relay and send CTS packets, the collection The trusted relays in the network then reply to the RTS packets one by one, detecting the time After that, the destination k Get a collaborative two-hop link with a trusted relay Calculate the secure transmission rate of relay-assisted and cooperative interference access mechanisms under trusted relay assistance Go to step 10;

[0080] Step 10: Compare If the size The maximum, then the destination dk Select the direct connection mechanism, source s k After receiving the CTS packet, the maximum achievable rate Access direct channel, duration if The maximum, then the destination d k Select the relay-assisted and cooperative interference access mechanism, the source s k After receiving the CTS packet, the maximum achievable rate Access channel, duration forward In time, source s k and Xin Su k Broadcast data packets and interference respectively, then Time, untrusted or trusted cooperative relay To the hostel k Amplify and forward the received data packet, and return to step 2 after the single transmission is completed; otherwise Maximum, sink d k Give up access and send a CTS packet, compete again in the next time slot, and return to step 2.

[0081] In specific implementation, the embodiment of the present invention may also provide a duration It is expressed by the following formula:

[0082]

[0083] Where: τ d represents the channel coherence time, τ J =Jτ R +τ C represents the time to detect J relays;

[0084] Detection time It is expressed by the following formula:

[0085]

[0086] Where: τ C Indicates the time of transmitting CTS data packet, J * represents the optimal number of detection relays, τ R Indicates the time when the RTS packet is transmitted.

[0087] Duration It is expressed by the following formula:

[0088]

[0089] The channel opportunity scheduling method provided by the embodiment of the present invention is based on the collaborative trust relationship between user pairs. There are untrusted relay nodes and user-to-communication nodes in the network. The user-to-communication nodes may have a deep trust relationship. The communication nodes that establish a deep trust relationship can relay each other. In order to suppress untrusted relay eavesdropping, when a certain source is transmitted through a relay link, its destination can synchronously send an artificial interference signal during the first hop transmission process, so that the signal-to-noise ratio received by the untrusted relay becomes smaller, thereby reducing its eavesdropping rate. Under such a social trust network structure, multiple sources compete for channels by sending and receiving detection data packets in a distributed manner, and measure the channel state in real time. When used, the user pair can dynamically select the direct channel, the trusted cooperation / untrusted relay-assisted collaborative interference channel according to its observation information to access, and realize the secure data transmission and reception under the assistance of multi-level trusted relays. Through simulation results, the security throughput and security interruption probability performance of the proposed method and existing similar methods are compared, and the effectiveness of the proposed three-level decision channel opportunity scheduling method is verified.

[0090] The method provided in the embodiment of the present invention is described in detail below and its effect is verified.

[0091] Aiming at the problem of users' collaborative access to distributed channels under multi-level trust, the present invention designs a three-level decision channel opportunity scheduling method based on multi-level social trust relationships. Under this method, for a social network with a three-level trust relationship, the optimal access strategy is selected according to the trust level between nodes to ensure the optimal average security throughput of the entire network.

[0092] The social trust relationship network model considered by the present invention is as follows: Figure 1 As shown, a multi-user network with three-level trust relationships is described.

[0093] The system contains multiple source nodes (i.e., information sources s1, s2, ..., s K ), destination node (i.e., destination d1, d2, ..., d K ), and the relay node source to sink pair satisfies the mapping relationship, the source s k The information sent is transmitted to the destination via direct / relay channels k .

[0094] For each user pair k, there may be three levels of trust relationships: untrusted, trusted, and cooperative. j , which is an untrusted node for all user pairs. Untrusted nodes can serve as auxiliary relay nodes for other user pairs, but are not allowed to access the channel alone because they may leak information. Untrusted nodes continuously eavesdrop on the information of the source during the source transmission process of the user pairs. They are referred to as untrusted relays in the present invention.

[0095] For user pairs, since they have obtained network authentication, they are all recognized as trusted nodes. On this basis, user pairs may have further trust relationships due to transmission tasks or holder attributes, that is, they are willing to cooperate to help each other forward data packets. On this basis, in order to suppress the eavesdropping of untrusted relays, the sink assists in sending artificial noise to interfere with untrusted relays to reduce their eavesdropping rate. Therefore, for user pair k, the set of user pairs willing to cooperate is called S K Based on a given social trust relationship network, different source-destination pairs can choose different access methods. The specific situations are divided into three types: direct connection (DT) channel access; relay-assisted-cooperative interference (CJ) channel access (untrusted relay); relay-assisted-cooperative interference (CJ) channel access (cooperative relay) or giving up the access opportunity and re-competing for the channel.

[0096] For ease of description, based on Figure 2 The network model shown in the figure first defines the basic parameters as follows:

[0097] There are K source-destination pairs, represented as a set of user pairs The source index is s1,...,s k ,...,s K , the destination index is d1,...,d k ,...,d K , there are L untrusted relay nodes, represented as the untrusted relay set The jth untrusted relay index is r j ; The set of trusted cooperative user pairs for each communication pair k is A k , then the cooperative trust relationship of the network is expressed as

[0098] All nodes compete for channels in a distributed manner in units of micro-time slots δ. At the beginning of each competitive micro-time slot, all sources independently send channel competition RTS packets with the same probability p0. If and only if there is only one source sending an RTS packet in the same micro-time slot, the source is the winning source, which is called a successful channel competition. The process from the start of channel competition to the emergence of the winning source is defined as an observation. For each observation process, the time elapsed before the winning source appears is random. Since each channel competition is independent, the total number of channel competitions experienced in a single observation follows the parameter Kp0(1-p0) K-1 The geometric distribution of , the average time of a single observation is:

[0099]

[0100] Among them, τ R Indicates the time to transmit the RTS packet, τC represents the time for transmitting CTS packets, K represents the number of source-destination pairs, δ represents the duration of idle time slots, and the time when a conflict occurs can be τ R express.

[0101] Consider a random channel fading model with statistical characteristics. Rayleigh fading is used to model the wireless channel. k To its destination k The direct channel SNR is expressed as Where D k Indicates k and d k The straight-line distance between them, α is the channel fading depth, h k is a small-scale fading parameter and its mean is Negative exponential random distribution, then γ k The mean is A negative exponential random distribution.

[0102] For indirect links, nodes The channel SNR between u≠v is expressed as:

[0103]

[0104] Among them, D u,v represents the distance between node u and node v, h u,v is a small-scale fading parameter and its mean is Negative exponential random distribution, then γ u,v The mean is Negative exponential random distribution. Assume that all wireless channels are symmetric, that is, γ u,v =γ v,u .

[0105] For the source k , the achievable transmission rate of the direct link can be expressed as The maximum eavesdropping rate can be expressed as Then the secure transmission rate under direct channel transmission can be expressed as make Indicates the maximum eavesdropping SNR of an untrusted relay.

[0106] For a given social trust relationship network Sources k Choose to use cooperative interference to In the first stage, the information source s k Broadcast data packets, while the destination d kIf the interference signal is broadcast, all other nodes receive a mixed signal containing data packets, interference signals and noise; in the second stage, the relay u amplifies and forwards the received signal, and the power of the relay amplification and forwarding is consistent with the power of the signal sent by the source, and the destination d k After receiving the forwarded mixed signal, it can be filtered according to the known interference signal information to obtain a signal containing only data packets and background noise. Based on this two-stage mechanism, the maximum achievable transmission rate of the relay link can be expressed as:

[0107]

[0108] The eavesdropping rate can be expressed as:

[0109]

[0110] Relay The secure transmission rate of the cooperative interference mechanism under assistance can be expressed as

[0111] For optional relay collections That is, the set of relay nodes that have obtained the link SNR, the maximum safe transmission rate and its corresponding achievable transmission rate and Can be expressed as:

[0112]

[0113] in, Indicates a set of optional relays The best relay index number within.

[0114] The channel coherence time is denoted as τ d , the time to detect J relays is denoted as τ J =Jτ R +τ C , then the channel transmission time after the detection relay is When each channel contention starts, all user pairs compete and access the shared channel in a distributed manner to achieve time-division data transmission.

[0115] During the channel contention process, if there is only one source s k Sending an RTS contention packet, the source wins the channel and is called the winning source, which corresponds to the cooperative relay set A k All source and sink nodes in s are willing to provide relay assistance for their data transmission. By receiving this RTS, all other nodes (source, sink and untrusted relay) can obtain the channel from s through channel estimation. k to its own channel SNR, that is, the node Get the first jump Destination k Get the direct channel SNRγ k . Destination k Can make first-level decisions. First-level decisions include:

[0116] ①Stop and connect. d k Send a CTS packet, so that the source s k At rate Access the direct channel.

[0117] ② Give up access. k Send a CTS packet to make all sources compete for the channel again.

[0118] ③Detect untrusted relays.

[0119] Destination k We choose to further detect all untrusted relays to obtain the SNR of the relay and eavesdropping channels, and make further decisions based on the information after detection. k Send a CTS packet, and let L untrusted relay nodes reply RTS in turn. The RTS of the reply contains By receiving the node RTS,d k The second hop can be estimated Detection time τ L =τ C +L·τ R After all L RTSs are received, d k That is, get the two hops of all untrusted relay links And calculate the maximum safe transmission rate of the relay link d k Second-level decisions can be made. Second-level decisions include:

[0120] ①Stop and access. For the optional relay set d k The method with a higher security transmission rate is preferred in the direct link and the cooperative interference link, and a CTS packet is sent to the source s k Transmit on the preferred link at the corresponding rate, and the transmission time is

[0121] ② Give up access. k Send a CTS packet to make all sources compete for the channel again.

[0122] ③Detect trusted cooperative relay.

[0123] Destination kSelect the cooperative relays to further explore their social trust relationship, represented as a set And make further decisions based on the information after detection, J * is the optimal number of detection relays. Similar to untrusted relay detection, d k Send a CTS packet to collect The nodes in the The RTS of the reply contains By receiving the node RTS,d k The second hop can be estimated Detection time After that, all J * RTS received, d k Get the collection Two-hop SNR of all node relay links in And calculate the maximum safe transmission rate of the relay link Destination k Can make third-level decisions, including:

[0124] ①For optional relay sets Destination k The method with a higher security transmission rate is preferred in the direct link and the cooperative interference link, and a CTS packet is sent to the source s k Transmit on the preferred link at the corresponding rate, and the transmission time is

[0125] ② Abandon access. k Send a CTS packet to make all sources compete for the channel again.

[0126] After a single access transmission ends, all signal sources restart the next round of channel contention, and each channel contention-access process is independent of each other. Figure 3 Given a signal from source s k Schematic diagram of the signaling process from winning the channel to accessing the cooperative interference link assisted by the trusted cooperative relay after the third-level decision.

[0127] For the selected detection relay number J≤|A k |, the corresponding detection relay set The specific description is: For each user pair k, calculate its trusted cooperative relay set A k Node u∈A k The average SNR of the relay link according to For set A k Rearrange in descending order and define the arranged set as where uj Mean The jth largest trusted cooperative relay node index. Then for a given number of trusted cooperative relay detections J≤|A k |, and the corresponding detection relay node set can be expressed as

[0128] The channel competition-observation-decision process is modeled as a three-level sequential planning decision process, which is specifically described as:

[0129] For the nth observation, after the nth successful channel contention, the source s k(n) Win the channel, its destination k(n) Get the direct channel SNRγ of the nth observation k (n), let φ n , and ψ n They represent the first-level, second-level, and third-level decisions, respectively, corresponding to the 3n-2, 3n-1, and 3n sub-observations.

[0130] In the 3n-2nd sub-observation, based on the observation information obtained in The time spent on the nth channel contention.

[0131] Winning Destination k(n) Make the first-level decision, denoted as φ n =-1,0,L, where φ n =0 means stop, that is, use the direct channel for transmission; φ n =-1 means continue, that is, give up the transmission opportunity and re-participate in channel competition; φ n =L means further detecting all untrusted relay nodes.

[0132] In addition, if the first-level decision n > 0, then enter the 3n-1th observation. If φ n =1, then the subsequent observation is skipped directly and the next channel competition process is entered.

[0133] In the 3n-1th observation, the destination d k(n) Detect all untrusted relay nodes and L After that, the observation information is obtained Based on observation information d k(n) Make the second-level decision, expressed as in Indicates stop, that is, in direct transmission and collection The best untrusted relay node in In the cooperative interference transmission under assistance, a method of selecting a channel with a higher rate is used for access; Indicates to continue, that is, to give up the transmission opportunity and re-participate in the channel competition; J * =1,…,|A k | indicates further detection of the set of trusted cooperative relay nodes

[0134] In the 3nth observation, the destination d k(n) Detecting a set of trusted cooperative relay nodes And at the detection time After that, the observation information is obtained Then, the hostel i(n) Make the third level decision n =-1,0, where ψ n =0 means stop, that is, in direct transmission and collection The best untrusted / trusted cooperative relay node in In the cooperative interference transmission under assistance, the method of selecting a channel with a higher rate is used for access; ψ n = -1 means continue, that is, the sink still decides to give up the access opportunity after detecting the relay, and makes the source compete for the channel again.

[0135] Based on the above three-level observation-decision process, for a given social collaboration network Definable historical decision sequences And the historical observation information sequence Respectively expressed as:

[0136]

[0137] The superscript n is a variable related to the length of the observation-decision sequence. For the convenience of representation, the following description of the present invention uses replace Obviously, the decision sequence Always terminates when the value of its elements is 0, and is reset after a successful transfer.

[0138] For each decision sequence Its time cost and benefits The specific description is: is the time from the start of channel contention to the end of a single transmission, expressed as:

[0139]

[0140] in represents the conditional assumption, represents the time spent on the lth channel contention, with an average value of τ0, τ L Indicates the time spent on the secondary untrusted relay detection. represents the time spent on the third-level trusted relay detection, τ d The total (detection and) data transmission time spent in this stop.

[0141] Based on the three-level stopping decision model, the user's benefit of accessing the channel at each level is different.

[0142] For the first-stage stop φ n =0, the expected return is expressed as:

[0143]

[0144] For the second stop The expected return is expressed as:

[0145]

[0146] For the third level stop ψ n =0, the expected return is expressed as:

[0147]

[0148] Each successful channel competition-channel access process is independent of each other. By repeating the observation-access process multiple times, the time-averaged system safety throughput can be obtained, that is, the system average safety throughput

[0149] Based on the three-level detection-decision channel access model of the above social trust network, the purpose of the method proposed in the present invention is to Design the optimal channel access method, i.e. the optimal decision sequence (stop time) Achieve the maximum system average safe throughput and achieve the optimal system average throughput:

[0150]

[0151] in, represents expectation, and sup represents the lowest upper bound.

[0152] For a given social trust network The present invention designs an optimal security channel opportunity scheduling method With a three-level decision-making structure, the maximum system average safe throughput can be achieved. The implementation steps are as follows: Figure 1 The specific description is as follows:

[0153] Step 1: Based on a given social trust network According to the statistical characteristic parameters of the distributed wireless network channel, the average security throughput of the system is obtained through offline iterative calculation Optimal decision level threshold vector User Classification Collection The specific function definition is as follows:

[0154] The three-level decision benefit function is defined as:

[0155] In the third-level decision, the benefits of stopping and giving up are:

[0156] and And there is

[0157] In the second-level decision, the expected benefit function of detecting J trusted cooperative relays is:

[0158]

[0159] in, Then the optimal number of detection relays J for detecting trusted cooperative relays is * And the corresponding profit function for:

[0160]

[0161] The payoffs of stopping and giving up in the second-level decision are and

[0162] Expected benefit function of detecting all untrusted relays in the first-level decision There are two cases, for satisfying |A k |>0 cooperative user pairs k.

[0163] For satisfying |A k |=0 for non-cooperative user pair k, The benefits of stopping and abandoning are and 0.

[0164] For a trusted cooperative user pair k, the detection difference function between detecting J cooperative relays and detecting J+1 cooperative relays is

[0165] Optimal system average safety throughput It is defined as the unique solution that satisfies the following equation.

[0166]

[0167] Optimal decision level threshold vector Defined as, For the equation and The only solution of There is no solution with γ>0, so let

[0168] User Classification Collection It is defined as, for a given set of user pairs Untrusted Relay Collection and social trust networks Users can classify k as follows.

[0169] For a given set of users Untrusted Relay Collection and social trust networks The user classifies k as follows:

[0170] If |A k |=0, Then the user has a first-level decision structure for k, which belongs to the classification set

[0171] If |A k |=0, Then the user has a secondary decision structure for k, belonging to the classification set

[0172] If |A k |>0, Then the user has a first-level decision structure for k, which belongs to the classification set

[0173] If |A k |>0, Then the user has a three-level decision structure for k, belonging to the classification set

[0174] Step 2: Multiple sources compete for the channel. At the beginning of the mini-slot of duration δ, all sources send RTS packets (request to send packets) with probability p0 to independently compete for the channel. There are three possible situations.

[0175] a. If no source sends an RTS packet, all sources compete for the channel in the next mini-time slot;

[0176] b. If two or more sources send RTS packets, an RTS transmission conflict occurs between the sources, and all sources continue to compete in the next mini-time slot;

[0177] c. If there is only one source s k Sending an RTS packet, the source gets the channel access opportunity and is called the winning source of the channel competition. k By receiving the RTS contention packet, all relay nodes and the destination can obtain sk The channel SNR to itself. k Get the instantaneous SNRγ of its direct link k (n) = γ, and the direct channel transmission rate Go to step 3;

[0178] Step 3: Sink k According to the calculation results of step 1, determine which category it belongs to. If Go to step 4; otherwise Go to step 5;

[0179] Step 4: If Then the destination k Select the direct DT access mechanism and send a CTS packet (allow sending of packets). The source s k Then at the maximum achievable rate Access direct channel, duration τ d , after a single transmission is completed, return to step 2; otherwise, the destination d k Give up access and send CTS, compete again in the next time slot, and return to step 2.

[0180] Step 5: If Then the destination k Give up access and send CTS, compete again in the next time slot, and return to step 2; if Then the destination k Select DT access mechanism and send CTS, source s k Then at the maximum achievable rate Access direct channel, duration τ d , after a single transmission is completed, return to step 2; otherwise, go to step 6;

[0181] Step 6: Sink k Select to detect all untrusted relays and send CTS. L untrusted relays then reply RTS in turn. The detection time is τ L After that, the destination k Get the SNRs of the cooperative two-hop link of the untrusted relay, Calculate the secure transmission rate of DT access and the secure transmission rate of the CJ access mechanism assisted by an untrusted relay make If the user Go to step 7, otherwise the user Go to step 8;

[0182] Step 7: If Then the destination k Decide to stop and send CTS, further, if Then the destination k Select DT access mechanism, source s k After receiving CTS, the maximum achievable rate Access direct channel, duration After a single transmission is completed, return to step 2, otherwise, the destination d k Select CJ access mechanism, source s k After receiving CTS, the maximum achievable rate Access channel, duration First 1 / 2τ d1 In time, source s k and Xin Su k Broadcast data and interference signals separately, then Time, untrusted relay To the hostel k Amplify and forward the received data packet, and return to step 2 after the single transmission is completed; otherwise Destination k Give up access and send CTS, compete again in the next time slot, and return to step 2;

[0183] Step 8: Calculate the optimal number of trusted cooperative relay detections J * Specifically, traverse J = 1, ..., | A k |, calculate the difference function like Then J * = J, end the traversal; otherwise, J * =|A k |, the optimal detection relay node set is Calculate the benefits of detecting trusted cooperative relays Go to step 9;

[0184] Step 9: If Then the destination k Select Stop and send CTS, return to step 7; if Then the destination k Give up access and send CTS, compete again in the next time slot, and return to step 2; otherwise, the destination d k Select Probe J * Trusted cooperative relays and send CTS, collection The trusted relays in the network then reply to RTS in turn, detecting the time After that, the destination k Obtaining SNRs of the cooperative two-hop link of the trusted relay Calculation of secure transmission rate of CJ access mechanism assisted by trusted relay Go to step 10;

[0185] Step 10: Compare If the size The maximum, then the destination d k Select DT access, source s k After receiving CTS, the maximum achievable rate Access direct channel, duration if The maximum, then the destination d k Select CJ access mechanism, source s k After receiving CTS, the maximum achievable rate Access channel, duration forward In time, source s k and Xin Su k Broadcast data packets and interference respectively, then Time, untrusted / trusted cooperative relay To the hostel k Amplify and forward the received data packet, and return to step 2 after the single transmission is completed; otherwise Maximum, d k Give up access and send CTS, compete again in the next time slot, and return to step 2.

[0186] The present invention has been rigorously simulated and tested, and the effectiveness and feasibility of the method proposed in this patent have been verified by computer simulation. A simulated wireless network communication scenario is constructed in MATLAB. Consider a 5km×5km square map with 10 source-destination communication pairs randomly deployed in it, and an untrusted relay is located in the center. Figure 4 shown.

[0187] Referring to the commonly used wireless communication scenarios, the channel fading depth is set to α = 2.5. u≠v, The statistical parameters of the relay channel and the direct channel are set as The unit is dB, ρ = 10dB. The length of the channel contention mini-slot is δ = 25μs, and the transmission time of RTS and CTS is τ R =τ C =50μs, channel coherence time is τ d =1ms, the channel contention probability is p0=0.3.

[0188] By comparing the performance of the method proposed in the present invention with the existing research methods, the superiority of the proposed method can be effectively verified. For the existing research methods on distributed channel access, the following four access strategies are mainly considered.

[0189] 1. Direct / relay transmission strategy: Multiple users compete for channels with reference to similar CSMA / CA protocols. The winning user has known SNRs of direct and untrusted relay links, and prefers the better way to access the channel between DT and AF transmission mechanisms, without considering the possibility of giving up.

[0190] 2. Collaborative interference transmission strategy: Multiple users compete for channels with reference to similar CSMA / CA protocols. The winning user always accesses the channel in CJ mode for known SNRs of direct and untrusted relay links, without considering the possibility of giving up.

[0191] 3. Direct / Relay-Optimal Transmission Strategy: Multiple users compete for channels with similar CSMA / CA protocols, and the winning user has known SNRs for direct and untrusted relay links. In the untrusted relay scenario, the winning user makes the best decision with the goal of maximizing the average network throughput, that is, it can choose to give up or stop. If it stops, it can select a better way to access the channel between the DT and AF transmission mechanisms.

[0192] 4. Collaborative Interference - Optimal Transmission Strategy: Multiple users compete for channels with reference to similar CSMA / CA protocols, and the winning user has known SNRs for direct and untrusted relay links. In the untrusted relay scenario, the winning user makes the best decision with the goal of maximizing the average security throughput of the system, that is, it can choose to give up or stop. If it stops, it uses the CJ transmission mechanism to access the channel.

[0193] Firstly, the impact of channel coherence time on network performance is analyzed. Figure 5 The average security throughput of the system is given by the channel coherence time τ d The curve of the change. Figure 5 It can be seen that when τ d When the access time increases from 1ms to 5ms, the average security throughput performance of all access strategies increases, but at different rates. Figure 5 It can be seen from the above that the average security throughput performance of the proposed method is always better than that of the other four comparison strategies. d =2ms, the average security throughput performance of the system proposed by the method of the present invention is 390% higher than the direct connection / relay strategy, 148% higher than the collaborative transmission strategy, 260% higher than the direct connection / relay-optimal transmission strategy, and 45% higher than the collaborative interference-optimal transmission strategy compared with the other four access strategies. By comparing these performance improvement ratios, it can be found that for a secure transmission network with an untrusted relay network, an effective collaborative interference mechanism will bring about significant performance improvement. On this basis, the efficient scheduling of access opportunities by users can further improve the overall network performance.

[0194] The present invention designs the optimal access method with the goal of maximizing the average security throughput of the system. However, for traditional secure transmission networks, the security interruption probability is a performance indicator that cannot be ignored. Most existing studies design algorithms based on the optimization of the security interruption probability. Therefore, in order to comprehensively compare the security transmission performance of the proposed method, the impact of the security interruption threshold β on the average security interruption probability in different strategies is compared. The security interruption probability is calculated as follows: for each data transmission, if the actual security transmission rate is greater than the security interruption threshold β, the transmission is called successful, otherwise it is a transmission interruption. After a certain number of transmissions, the ratio of the number of interrupted transmissions to the total number of transmissions is the security interruption probability.

[0195] Figure 6 Given that when τ d =2ms, the curve diagram of the average security interruption probability under different strategies changes with the security interruption threshold β. It is obvious that the average security interruption probability of the method proposed in the present invention is lower than that of the other four comparison algorithms. This is because in the proposed algorithm, after obtaining the channel SNR, the winning user pair only accesses the channel when the channel conditions are good, and the transmission rate is adaptively adjustable, that is, there is no transmission interruption and the probability of security interruption is small. When the security interruption threshold is small, the average security interruption probability of the cooperative interference-optimal transmission strategy with the goal of maximizing the security throughput and the strategy proposed in this chapter are both close to 0, and when the security interruption threshold is greater than the average security throughput of the network λ * When the expected safe transmission rate is less than λ, the average safe interruption probability increases sharply. * When the user gives up access to the channel, avoiding interruption of secure transmission.

[0196] The embodiment of the present invention is based on a distributed wireless collaborative network with a three-level social trust relationship, and proposes an opportunistic channel access scheduling method based on a given social trust network structure. A three-level competition-observation-decision channel access scheduling mechanism is defined. In each set of decisions, the user decides whether to access the channel or detect the relay channel based on the local and relay channel information observed by the user.

[0197] Based on the different properties of untrusted relays and trusted cooperative relays, a two-level relay detection method is defined. In the first detection, all untrusted relays need to be detected, and in the second detection, some trusted cooperative relays can be selectively detected.

[0198] The trusted cooperative relay detection in the proposed method selects the optimal number of detection relays and the corresponding optimal detection trusted relay set according to the difference benefit function, and sorts all trusted relays in descending order according to the SNR expectation, so that for each number of detection relays, there is a unique optimal detection trusted relay set, which transforms the multi-combinatorial problem into a linear quantity selection problem and reduces the computational complexity.

[0199] The optimal decision-first-level threshold vector, optimal system average throughput, and source-destination pair classification in the proposed method can all be obtained through offline calculation. The Monte Carlo method is used to simulate the statistical characteristics of the network channel to calculate the corresponding parameters. The calculation complexity is low and it can converge to the optimal value in a limited number of iterations.

[0200] Based on the optimal system average throughput, classification set, and optimal decision-level threshold vector, a three-level decision channel opportunistic scheduling method based on multi-level social trust relationship is designed; after the source successfully competes for the channel, it determines the classification interval to which it belongs and selects the corresponding opportunistic access strategy; then, by comparing the direct channel SNR with the optimal decision-level threshold vector, it is determined whether it needs to further detect the untrusted relay channel. If it chooses to detect the untrusted relay, it makes a further decision after the detection to determine whether it needs to further detect the trusted cooperative relay. If it chooses to detect the trusted cooperative relay, it selects the optimal number of relays and the optimal relay set to detect. Then, according to the direct channel, trusted relay channel, and untrusted relay channel information obtained by the detection, the access method with the maximum expected secure transmission rate is selected for access. The proposed method combines the physical layer, network layer protocols, and cooperative interference secure transmission mechanism, making full use of multi-user diversity, relay diversity, and cooperative interference. The user pairs cooperate with each other, and the user sends an artificial interference signal to its own destination for the first hop link of its source. It makes full use of multiple transmission mechanisms and scheduling methods to optimize the average secure throughput of the system.

[0201] In summary, the channel opportunity scheduling method provided by the present invention is based on the social trust relationship between user pairs. Communication nodes that deeply trust each other can simultaneously serve as each other's relay nodes, which increases role diversity and makes full use of spatiotemporal diversity and relay diversity gain. In the second-level trusted cooperative relay detection, the optimal set of relay nodes is selectively detected, the time overhead of detecting relays is associated with the detection benefit, and the relay set with the largest expected benefit is selected for detection. Under limited detection overhead, the trusted cooperative relay nodes with better channel conditions are detected to avoid unnecessary detection overhead. According to the actual situation of the wireless communication network, the social trust relationship of user pairs in the wireless networking is modeled, and the two situations of untrusted relay eavesdropping and deep trust cooperation of communication nodes are considered at the same time. The network trust is divided into three levels, which is in line with the existing temporary networking, emergency network, drone clusters and other flexible and unsafe networks that lack node security verification, and have strong flexibility and applicability. The channel parameter model is constructed with the distance between nodes as a reference, which reflects the heterogeneity of the network. Different source-destination pairs may have three different access decision structures. Moreover, the optimal decision-making first-level threshold vector of each user pair depends on its own channel statistical characteristics and social trust relationship, and can be calculated offline without occupying the channel transmission time of the user pair. The optimal number of detection relays in the second-level decision can also be calculated by Monte Carlo simulation. Online, only the expected benefit function of detecting trusted cooperative relays needs to be calculated, and the calculation amount is relatively small.

[0202] RTS: request-to-send, a request to send packet, is a common data packet in the channel sensing access protocol. It is used by the sending node user to detect channel occupancy and estimate channel quality.

[0203] CTS: clear-to-send, clear-to-send packet, is a common data packet in the channel-aware access protocol, and the receiving node responds to the sending node.

[0204] SNR: Signal Noise Ratio, signal-to-noise ratio, is the power ratio of the effective signal to the noise in the signal received by the receiver.

[0205] Opportunistic channel scheduling: multiple users share the channel, compete for the channel when the channel is idle, and dynamically schedule access channel opportunities.

[0206] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0207] It can be seen from the above description of the implementation mode that those skilled in the art can clearly understand that the present invention can be implemented by means of software plus a necessary general hardware platform. Based on such an understanding, the technical solution of the present invention is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a storage medium, such as ROM / RAM, a magnetic disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment of the present invention or some parts of the embodiments.

[0208] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can refer to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system or system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can refer to the partial description of the method embodiment. The system and system embodiments described above are merely schematic, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without creative work.

[0209] The above description is only a preferred embodiment of the present invention and is not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.

Claims

1. A channel opportunity scheduling method, characterized in that: include: Step 1: Based on a given social trust network, obtain characteristic parameters according to the distributed wireless network channel statistics, and obtain the system average security throughput through offline iterative calculation Optimal decision level threshold vector User Classification Collection The social trust network includes a heterogeneous wireless collaborative network consisting of multiple information source and information sink pairs with a three-level trust relationship; Step 2: At the beginning of the mini-slot of duration δ, all sources send RTS packets with the same probability P0 to independently compete for the channel; Step 3: Sink k According to the calculation result of step 1, determine the destination d k Which category does the user k belong to? Go to step 4; otherwise Go to step 5; Step 4: If the channel signal-to-noise ratio Then the destination k Select the direct connection mechanism and send a CTS packet. k At the maximum achievable rate Access direct channel, duration τ d , after a single transmission is completed, return to step 2; otherwise, the destination d k Give up access and send a CTS packet, compete again in the next time slot, and return to step 2; Step 5: If the channel signal-to-noise ratio Then the destination k Give up access and send CTS data packet, compete again in the next time slot, and return to step 2; if the channel signal-to-noise ratio Then the destination k Select the direct connection mechanism and send a CTS packet. k Then at the maximum achievable rate Access direct channel, duration τ d , after a single transmission is completed, return to step 2; otherwise , go to step 6; Step 6: Sink k Select to detect all untrusted relays and send CTS packets. L untrusted relays then reply with RTS packets in turn. The detection time is τ L After that, the destination k Obtain the SNRs of the cooperative two-hop link of the untrusted relay and calculate the secure transmission rate of the direct access mechanism access and the secure transmission rate of relay-assisted and cooperative interference access mechanisms under the assistance of untrusted relays make If the user Go to step 7, otherwise the user Go to step 8; Step 7: If Then the destination k Decide to stop and send CTS packets if Then the destination k Select the direct connection mechanism, source s k After receiving the CTS packet, the maximum achievable rate Access direct channel, duration After a single transmission is completed, return to step 2, otherwise, the destination d k Select the relay-assisted and cooperative interference access mechanism, the source s k After receiving the CTS packet, the maximum achievable rate Access channel, duration forward In time, source s k and Xin Su k Broadcast data and interference signals separately, then Time, untrusted relay To the hostel k Amplify and forward the received data packet, and return to step 2 after the single transmission is completed; otherwise Destination k Give up access and send a CTS packet, compete again in the next time slot, and return to step 2; Step 8: Calculate the optimal number of trusted cooperative relay detections J * ; Traverse J = 1,…,|A k |, calculate the difference function like Then J * = J, end the traversal; otherwise J * =|A k |, the optimal detection relay node set is Calculate the benefits of detecting trusted cooperative relays Go to step 9; Step 9: If Then the destination k Select Stop and send CTS packet to return to step 7; if Then the destination k Give up access and send CTS data packet, compete again in the next time slot, and return to step 2; otherwise, the destination d k Select Probe J * trusted cooperative relay and send CTS packets, the collection The trusted relays in the network then reply to the RTS packets one by one, detecting the time After that, the destination k Obtaining SNRs of the cooperative two-hop link of the trusted relay Calculate the secure transmission rate of relay-assisted and cooperative interference access mechanisms under trusted relay assistance Go to step 10; Step 10: Compare If the size The maximum, then the destination d k Select the direct connection mechanism, source s k After receiving the CTS packet, the maximum achievable rate Access direct channel, duration if The maximum, then the destination d k Select the relay-assisted and cooperative interference access mechanism, the source s k After receiving the CTS packet, the maximum achievable rate Access channel, duration forward In time, source s k and Xin Su k Broadcast data packets and interference respectively, then Time, untrusted or trusted cooperative relay To the hostel k Amplify and forward the received data packet, and return to step 2 after the single transmission is completed; otherwise Maximum, sink d k Give up access and send a CTS packet, compete again in the next time slot, and return to step 2.

2. The channel opportunity scheduling method according to claim 1, characterized in that: The optimal system average safety throughput It is defined as the unique solution that satisfies the following equation: Where: K represents the number of source and sink pairs, τ d represents the channel coherence time, represents the safe transmission rate under direct channel transmission, n represents the number of observations, represents the expected revenue function of all untrusted relays, γ represents the signal-to-noise ratio, and τ0 represents the average time of a single observation.

3. The channel opportunity scheduling method according to claim 2, characterized in that: The average time τ0 of a single observation is expressed as follows: Where: τ R Indicates the time to transmit the RTS packet, τ C represents the time to transmit the CTS data packet, K represents the number of source and sink pairs, δ represents the duration of the idle time slot, τ R Indicates the time when the conflict occurs, Kp0(1-p0) K-1 The total number of channel contentions experienced by a single observation follows the parameter.

4. The channel opportunity scheduling method according to claim 1, characterized in that: The optimal decision level threshold vector Defined as: Distribution as equation and The only solution of There is no solution with γ>0, so let 5. The channel opportunity scheduling method according to claim 1, characterized in that: The user classification set Defined as: For a given set of users Untrusted Relay Collection and social trust network A={A1,A1,…A K＝ }, the user classifies k as follows: If |A k |=0, Then the user has a first-level decision structure for k, which belongs to the classification set If |A k |=0, Then the user has a secondary decision structure for k, belonging to the classification set If |A k |>0, Then the user has a first-level decision structure for k, which belongs to the classification set If |A k |>0, Then the user has a three-level decision structure for k, belonging to the classification set 6. The channel opportunity scheduling method according to claim 1, characterized in that: Sources k Maximum achievable rate It is expressed by the following formula: Where: γ k represents the signal-to-noise ratio of the direct channel, D k Indicates k and d k The straight-line distance between them, α represents the channel fading depth, h k represents the small-scale fading parameter and its mean is A negative exponential random distribution.

7. The channel opportunity scheduling method according to claim 6, characterized in that: Secure transmission rate for direct access mechanism access It is expressed by the following formula: Where: Indicates the source k The maximum achievable rate, Indicates the maximum eavesdropping rate.

8. The channel opportunity scheduling method according to claim 1, characterized in that: Secure transmission rate of relay-assisted and cooperative interference access mechanisms under untrusted relay assistance It is expressed by the following formula: Where: Indicates the maximum achievable transmission rate of an untrusted relay link. Indicates the eavesdropping rate of the relay link.

9. The channel opportunity scheduling method according to claim 1, characterized in that: Duration It is expressed by the following formula: Where: τ d represents the channel coherence time, τ J =Jτ R +τ C represents the time to detect J relays; Detection time It is expressed by the following formula: Where: τ C Indicates the time of transmitting CTS data packet, J * represents the optimal number of detection relays, τ R Indicates the time when the RTS packet is transmitted.

10. The channel opportunity scheduling method according to claim 9, characterized in that: Duration It is expressed by the following formula:

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