Multi-hop wireless ad hoc network and centerless distributed frequency selection networking transmission method thereof

Abstract

The invention relates to the technical field of mobile wireless network communication, and provides a multi-hop wireless ad hoc network and a centerless distributed frequency selection networking transmission method thereof. The method comprises the steps of networking control based on a service frequency hopping channel, spectrum sensing and spectrum evaluation, frequency selection negotiation based on neighbor nodes, time-frequency resource scheduling based on frequency selection, and frequency selection optimization based on data transmission. On the basis of TDMA channel access design, a networking control mechanism based on a service frequency hopping channel is designed, and nodes dynamically select available frequency channels for network service transmission in a distributed mode. Available frequency spectrum information is obtained through autonomous frequency spectrum sensing and frequency spectrum evaluation of nodes, frequency selection negotiation is performed between adjacent network nodes, and dynamic scheduling use of time-frequency two-dimensional resources is performed in combination with a frequency selection result, so that data transmission of network centerless distributed self-adaptive frequency selection is realized; and the reliable networking and communication capabilities of the network in a complex electromagnetic interference environment are enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of mobile wireless network communication. Specifically, it relates to a multi-hop wireless ad-hoc network and a centerless distributed frequency selection networking transmission method thereof. Background Art

[0002] A wireless ad-hoc network is a communication network that does not rely on a pre-set infrastructure. It is widely used in special occasions such as military, emergency communication, disaster relief, etc., and has always been a key research direction in wireless communication technology. A wireless ad-hoc network forms a multi-hop, temporary autonomous communication system based on the communication protocol interaction between peer nodes. Its construction is inseparable from the wireless channel transmission based on a specific frequency channel between nodes, and thus there are inevitable requirements for the use of frequency channel resources.

[0003] Existing ad-hoc networks mostly use a fixed-frequency method for communication, that is, data is transmitted between nodes at a pre-configured fixed channel frequency. When there is external interference in the used channel frequency, serious packet loss will occur in the communication between network nodes, and even the link will be blocked, making it impossible to normally carry out networking protocol interaction and service data transmission. Therefore, in order to improve the anti-interference ability of wireless ad-hoc networks and enhance the effectiveness of working in a complex electromagnetic environment, the network needs to have the ability of dynamic frequency selection networking communication.

[0004] In order to avoid the interfered channel frequency and achieve dynamic selection of non-interfering frequencies for communication, the ad-hoc network introduces a design of frequency selection working mode, and two methods, centralized frequency selection and distributed frequency selection, can be adopted. When using the centralized frequency selection method, the ad-hoc network nodes need to collect the frequency selection auxiliary information and converge and transmit it to a specific node in the network, and this node makes a decision to select the best frequency suitable for the overall network operation according to the converged network-wide frequency selection information. Centralized frequency selection requires multi-hop relay transmission of frequency selection information, resulting in a large network resource overhead; at the same time, since the spectrum environment information and interference status faced by each node in the working area of the network change rapidly, it is difficult to quickly and efficiently select the best unified frequency suitable for the overall network use. These disadvantages of the centralized frequency selection method will be more prominent in large-scale wireless ad-hoc network applications.

[0005] To overcome the deficiencies of the centralized frequency selection method, adopting distributed frequency selection for networking communication is an important direction in the research of wireless ad-hoc networks. Although the existing method "A Distributed Frequency Selection Method for Wireless Ad-hoc Networks" (publication number CN110881221A) adopts a distributed spectrum sensing design, its frequency selection decision still relies on a central node or a specific decision node for centralized decision-making. To eliminate the inconvenience caused by the central node making frequency selection decisions and achieve stable and reliable distributed non-centralized networking applications for wireless ad-hoc networks in an interference environment, the present invention proposes a multi-hop wireless ad-hoc network and its non-centralized distributed frequency selection networking transmission method. By designing and running a distributed frequency selection algorithm without the participation of a central node among nodes, each node in the network can automatically negotiate with its neighbor nodes to adapt to the available frequency channels in the current network environment, and based on the negotiated and selected channels, perform distributed networking resource scheduling and data transmission, realizing robust and efficient networking communication for the ad-hoc network in an interference environment. Summary of the Invention

[0006] Aiming at the application requirements of multi-hop wireless ad-hoc networks for adaptive frequency selection communication in an interference environment, the present invention provides a multi-hop wireless ad-hoc network and its non-centralized distributed frequency selection networking transmission method to solve the problem of how nodes in the network dynamically and efficiently select non-interfering frequency channels in a non-centralized distributed manner for networking communication.

[0007] A non-centralized distributed frequency selection networking transmission method for a multi-hop wireless ad-hoc network provided by the present invention includes:

[0008] Networking control based on duty hopping channels: Divide the channel time into a continuous and periodically repeated time frame structure; in each time frame period, further divide the channel into several time slots, and classify the time slots into spectrum sensing time slots, networking control time slots, and data transmission time slots according to the usage type;

[0009] Spectrum sensing and spectrum evaluation: In the spectrum sensing time slots, screen the frequency channels through spectrum sensing and spectrum evaluation;

[0010] Frequency selection negotiation based on neighbor nodes: Nodes negotiate frequency selection with neighbor nodes based on the results of spectrum sensing and spectrum evaluation using the networking control time slots;

[0011] Time-frequency resource scheduling based on frequency selection: After completing the frequency selection negotiation, perform time-frequency resource scheduling for the data transmission time slots;

[0012] Frequency selection optimization based on data transmission: Perform data transmission based on the time-frequency resource scheduling, and optimize the frequency selection according to the data transmission situation.

[0013] In some embodiments, the functions of the spectrum sensing time slots, networking control time slots, and data transmission time slots are as follows:

[0014] The spectrum sensing time slot is used for each network node to perform spectrum sensing and obtain the available spectrum information in the current working environment;

[0015] The network formation control time slot is used for each network node to reliably interact with network formation control and distributed frequency selection information;

[0016] The data transmission time slot is used for each network node to transmit service data information to neighbor nodes using the selected frequency according to its own service communication requirements, supporting various types of service transmission services.

[0017] In some embodiments, the screening of frequency channels through spectrum sensing and spectrum evaluation includes:

[0018] The node performs spectrum sensing on the frequency channels within the working frequency band in the spectrum sensing time slot, and uses the receiver to detect the signals on each frequency channel; through digital signal processing, the spectral energy of the signals received on each frequency channel is quantitatively graded, and E(i,f) represents the spectral energy of the signal obtained by node i for spectrum sensing of frequency channel f, E th represents the threshold setting for interference detection. When E(i,f)≥E th , it is determined that there is interference on frequency channel f, otherwise there is no interference, and the corresponding frequency channel can be used for node frequency selection;

[0019] Under the condition of no obvious interference, the node senses the spectral energy of the surrounding environment through the receiver to obtain the receiver environmental noise floor B n (i,f) of node i for frequency channel f. Let the receiver noise floor of node i for frequency channel f be R n (i,f). For node reception, when the receiver environmental noise floor is lower than the receiver noise floor, the node's wireless reception can work normally. Thus, the spectral quality is evaluated through environmental noise floor analysis, and a frequency channel with better spectral quality is selected for communication.

[0020] In some embodiments, let the M frequency channels available for node data transmission in the wireless ad hoc network be represented as the frequency set F(M) = {f1, f2,..., f M}; N(u) represents the set of one-hop neighbor nodes of node u, and |A| represents the number of elements in set A; the node and its neighbor nodes perform frequency selection negotiation using the network formation control time slot based on the results of spectrum sensing and spectrum evaluation, including:

[0021] Step S101: Each node in the wireless ad hoc network preliminarily screens non-interfering frequencies according to the results of spectrum sensing and spectrum evaluation; for node i, for each frequency f in the frequency set F(M) j, 1 ≤ j ≤ M, excluding those that satisfy condition E(i, f j ) ≥ E th of the frequency points, and the remaining frequency set is denoted as F1(i);

[0022] Step S102: Each node in the wireless ad-hoc network separately filters out frequencies with better quality from the obtained remaining frequency set; for node i, for each frequency f in its remaining frequency set F1(i) j , 1 ≤ j ≤ |F1(i)|, excluding those that satisfy condition B n (i, f j ) ≥ B th of the frequency points, where B th represents the acceptable noise threshold, and the remaining frequency set is denoted as F2(i);

[0023] Step S103: Each node checks whether the remaining frequency set F2(i) is empty, that is, whether there are available frequencies; for node i, it determines whether the condition |F2(i)| ≥ 1 is satisfied; when the condition is satisfied, it indicates that there is at least one frequency in the frequency set F2(i), that is, the node has at least one frequency available for communication reception, and the next step is executed; if the condition is not satisfied, the acceptable noise threshold B th in Step S102 is adjusted again, and Step S102 is repeatedly executed until the condition is satisfied;

[0024] Step S104: Each node in the wireless ad-hoc network uses its respective network control time slot to broadcast and announce the selected frequency set F2 to all one-hop neighbor nodes, and the frequency set announced by node i is F2(i);

[0025] Step S105: Each node receives the frequency sets announced by neighbor nodes and stores them in the local memory for subsequent use by this node to perform frequency selection data transmission to neighbor nodes.

[0026] In some embodiments, the time-frequency resource scheduling is based on two-dimensional time-frequency resource scheduling, including resource application, neighbor response, and occupancy announcement; the two-dimensional time-frequency resource is composed of a time slot s and the corresponding frequency f; during the time-frequency resource scheduling process, when a node allocates a data transmission time slot, it needs to specify the frequency used for sending during this data transmission time slot.

[0027] In some embodiments, the resource application includes:

[0028] Step S201: A node calculates the required number of data transmission time slots according to the service sending requirement, the amount of data R to be sent per unit time, and the data size D_Size that the node can send per unit time slot;

[0029] Step S202: According to the calculation result of the number of data transmission time slots required by the node, assuming that the node needs m data transmission time slots, randomly select m data transmission time slots in the TDMA time frame for application, where the selected data transmission time slots exclude the time-frequency resources that have been announced to be occupied by its own node and each neighbor node in terms of frequency requirements;

[0030] After the node selects the applied time-frequency resources, it broadcasts and sends the application information through the inherent networking control time slot of this node.

[0031] In some embodiments, the neighbor response includes:

[0032] Step S301: All neighbor nodes receive the application information announced by the sending node in the networking control time slot;

[0033] After each node receives the application information broadcast and sent by the neighbor node, it will judge whether the application is granted according to the information it has, and give the corresponding response information;

[0034] According to the response information given by the node, broadcast and announce the response in the next sending opportunity of the inherent networking control time slot of this node.

[0035] In some embodiments, the occupancy announcement includes:

[0036] Step S401: The node receives the response announcement from the neighbor node and extracts the response information related to the time-frequency application information of this node;

[0037] Step S402: According to the response information from the neighbor node, judge whether the time-frequency application of the node is granted. When the time-frequency application is granted, in the next time frame, the node will occupy time slot s and use frequency f to transmit data to the receiving node;

[0038] Step S403: According to the service sending requirement of node i, the node continuously uses the applied time slot for transmission; among them, node i continuously announces the time slot sending status in the inherent networking control time slot sending opportunity, and the receiving node continuously announces the time slot receiving status in the inherent networking control time slot sending opportunity until node i no longer needs to occupy the allocated time slot for sending.

[0039] In some embodiments, the optimization of frequency selection according to the data transmission situation includes:

[0040] During the data transmission process, the receiving node evaluates whether the selected frequency meets the transmission requirements by statistically counting the frame error rate; when the frame error rate is high and the data transmission between nodes cannot be effectively executed, the receiving node will update the frequency set F2 announced in step S104, thereby triggering the sending node i to re-select new time-frequency resources for application and transmission.

[0041] The present invention also provides a multi-hop wireless ad-hoc network, and the multi-hop wireless ad-hoc network includes several nodes;

[0042] The several nodes perform data transmission by using the above multi-hop wireless ad-hoc network centerless distributed frequency selection networking transmission method.

[0043] In summary, due to the adoption of the above technical solutions, the beneficial effects of the present invention are as follows:

[0044] 1. The present invention uses a distributed design for frequency selection and time-frequency resource scheduling transmission of a wireless ad-hoc network, avoiding the deficiencies of the traditional centralized frequency selection working mode that requires multi-hop aggregation and forwarding of frequency selection auxiliary information, and does not require a centralized frequency selection control node to be set in the network, and can better adapt to and ensure the good characteristics of the centerless and distributed operation of the multi-hop wireless ad-hoc network.

[0045] 2. The present invention integrates the networked frequency selection design with the networking scheduling transmission of time-frequency resources, which can not only effectively solve the problem that network nodes autonomously avoid interfering frequencies for communication under interference conditions, but also can perform resource scheduling and allocation from the two-dimensional perspective of time-frequency, and can achieve better channel resource utilization, which has certain practical significance for improving the data transmission performance of the wireless ad-hoc network. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a schematic diagram of a multi-hop wireless ad-hoc network centerless distributed frequency selection networking transmission method provided by an embodiment of the present invention.

[0047] Figure 2 It is a schematic diagram of the TDMA time frame structure in an embodiment of the present invention.

[0048] Figure 3 It is a schematic diagram of the networking control time slot transmission based on duty hopping in an embodiment of the present invention.

[0049] Figure 4 It is a flowchart of the spectrum sensing and spectrum evaluation interference discovery work in an embodiment of the present invention.

[0050] Figure 5 It is a schematic diagram of a multi-hop topology wireless ad-hoc network exemplified in an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0051] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Components of the embodiments of the present invention generally described and illustrated in the drawings herein may be arranged and designed in a variety of different configurations.

[0052] Therefore, the detailed description of the embodiments of the present invention provided in the drawings below is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0053] In view of the application requirements of multi-hop wireless ad-hoc networks for adaptive frequency selection communication in an interference environment, the present invention provides a multi-hop wireless ad-hoc network centerless distributed frequency selection networking transmission method to solve the problem of how nodes in the network dynamically and efficiently select non-interfering frequency channels for networking communication in a centerless distributed manner. Its design principle is: based on the TDMA channel access design, a networking control mechanism based on duty hopping channels is designed to enable nodes to distributively and dynamically select available frequency channels for network service transmission. Through the autonomous spectrum sensing and spectrum evaluation of nodes, available spectrum information is obtained, and frequency selection negotiation is carried out between adjacent network nodes. At the same time, combined with the frequency selection results, dynamic scheduling and use of time-frequency two-dimensional resources are carried out to achieve centerless distributed adaptive frequency selection data transmission of the network, enhancing the reliable networking and communication capabilities of the network in a complex electromagnetic interference environment.

[0054] First, consider a wireless ad-hoc network with a multi-hop topology. Each node in the network is configured with a transceiver with an omnidirectional antenna, and the transceiver operates in a half-duplex mode. Therefore, a node cannot perform sending and receiving operations simultaneously during operation. This wireless ad-hoc network has multiple channels with different frequencies available, and the node transceiver can dynamically switch the operating frequency to achieve node transmission based on channels with different frequencies. Network nodes use the TDMA method to access channels and share wireless channel resources, and the clocks of all network nodes are precisely synchronized. During the operation of the network, external interference appears randomly and can be effectively detected, and the channel frequencies affected by interference cannot be used for node communication anymore.

[0055] Based on this, as Figure 1 shown, a multi-hop wireless ad-hoc network centerless distributed frequency selection networking transmission method proposed in this embodiment includes five design aspects: networking control based on duty hopping channels, spectrum sensing and spectrum evaluation, frequency selection negotiation based on neighbor nodes, time-frequency resource scheduling based on frequency selection, and frequency selection optimization based on data transmission. Specifically as follows:

[0056] First aspect, networking control based on service hopping channels:

[0057] In a wireless ad-hoc network with a multi-hop topology, if the frequency channel where a node operates is interfered with, it may lead to data transmission failure between nodes. Distributed frequency selection networking transmission requires nodes to continuously and stably exchange basic information such as networking control information and distributed frequency selection information with each other at a certain period, even under the condition of partial frequency interference. Therefore, in order to ensure that nodes can still stably exchange basic information under interference conditions and support distributed frequency selection networking, this embodiment designs networking control based on service hopping channels. For a wireless ad-hoc network based on TDMA access, the channel time is divided into a continuous and periodically repeating TDMA time frame (Frame) structure. In each time frame period, the channel is further divided into a certain number of time slots, and the time slots are classified into spectrum sensing time slots, networking control time slots, and data transmission time slots according to different usage types. The functions of each type of time slot are described as follows:

[0058] Spectrum sensing time slot: Defined as the SS (Spectrum Sensing) time slot, which is used for each network node to perform spectrum sensing and obtain the available spectrum information in the current working environment. In the spectrum sensing time slot, all network nodes do not need to send on the channel to avoid the influence of their own signals on the spectrum sensing results.

[0059] Networking control time slot: Defined as the NC (Networking Control) time slot, which is used for each network node to reliably exchange networking control and distributed frequency selection information. Each node in a wireless ad-hoc network needs to be effectively allocated at least one networking control time slot to meet its periodic transmission requirements for basic information such as networking control and frequency selection.

[0060] Data transmission time slot: Defined as the DT (Data Transmitting) time slot, which is used for each network node to transmit service data information to neighbor nodes using the selected frequency according to its own service communication requirements, supporting various types of service transmission services. According to the amount of service data sent, a node may apply to occupy multiple data transmission time slots as needed and release the occupied time slots after completing the service transmission, so as to leave them for other nodes to continue to apply for use.

[0061] The TDMA time frame structure is as Figure 2 shown. Generally speaking, for a wireless ad-hoc network according to different usage requirements, the design form of the TDMA time frame structure is different, and the number of various time slot planning configurations is also different, but this does not affect the use of the method of the present invention. Generally, in order to obtain a higher networking transmission efficiency, the configuration of various time slots is mainly based on data transmission time slots, so that more channel resources are used for service data transmission in the network.

[0062] The networking control time slot adopts a channel transmission method based on service frequency hopping to ensure that information transmission will not fail due to interference on some frequencies during the transmission process. In each networking control time slot, the node uses multiple service frequencies for frequency hopping communication to achieve frequency diversity transmission. By sending signals on different frequencies and taking advantage of the different interference characteristics of signals on different frequencies, the influence of interference on the transmitted signal is reduced, and the reliability and stability of the networking control time slot transmission are improved. Assume that the frequency set of service frequency hopping contains N frequencies, and these N frequencies are randomly selected according to TOD (Time Of Day) information and a random sequence, and the N frequencies are evenly distributed within the entire frequency hopping band. Physical layer channel redundancy coding is adopted and long interleaved frequency hopping transmission is performed. Among the N frequencies f1, f2, …, f N , as long as 1 frequency is not interfered, it can ensure that the control information sent by the node can be correctly received. The N frequencies in the frequency set change with the passage of TOD information. Therefore, it will not occur that when there is interference on certain established frequencies in the frequency band, it continuously affects the reliable transmission of a certain networking control time slot during the network operation process, ensuring the reliable interaction of basic information between networking nodes under interference conditions. The transmission method of the networking control time slot based on service frequency hopping is as Figure 3 shown.

[0063] Second aspect, spectrum sensing and spectrum evaluation

[0064] For the network node to perform the frequency selection operation, it needs to be based on the node's discovery of potential interference on the spectrum channel and the detection of idle and available spectrum channels. In the said spectrum sensing time slot, the frequency channels are screened through spectrum sensing and spectrum evaluation, and the surrounding electromagnetic environment where the node's work deployment is located is sensed and analyzed to immediately discover available high-quality frequency points, thereby supporting the node to select and utilize the best frequency points to communicate with surrounding neighbor nodes.

[0065] In this embodiment, the energy detection method is adopted for spectrum sensing. The node performs spectrum sensing on M frequency channels within the working frequency band in the spectrum sensing time slot, uses the receiver to detect the signals on each frequency channel, and quantifies and classifies the signal spectrum energy received on each channel through digital signal processing (including FFT Fourier transform, modulus square, cumulative summation, etc.). The lower the signal spectrum energy, the smaller the interference signal on this channel and the smaller the influence on data transmission. Let E(i,f) represent the signal spectrum energy obtained by node i for spectrum sensing of frequency channel f, and E th represent the threshold setting for interference detection. When E(i,f) ≥ E th , it is determined that there is interference on frequency channel f, otherwise there is no interference, and the corresponding frequency channel can be used for node frequency selection. The interference discovery work process of spectrum sensing and spectrum evaluation is as Figure 4as shown

[0066] Under the condition of no obvious interference, the node senses the spectrum energy of the surrounding environment through the receiver, and obtains the receiver environmental noise floor B of node i for frequency channel f n (i, f). Let the receiver noise floor of node i for frequency channel f be R n (i, f). For node reception, when the receiver environmental noise floor is lower than the receiver noise floor, the node's wireless reception can work normally; otherwise, the receiver sensitivity will degrade, resulting in a significant decline in the communication performance between nodes. Therefore, the spectrum quality is evaluated through the analysis of the environmental noise floor, promoting the selection of a frequency channel with better spectrum quality for communication to support better frequency selection and networking communication performance.

[0067] Thirdly, frequency selection negotiation based on neighbor nodes

[0068] In a wireless ad hoc network, when a node sends data to a neighbor node, its success depends on the quality of the received signal at the receiving node. When node i sends data to node j using frequency f, if there is signal interference in node j's reception on frequency f, it will lead to data transmission failure. Therefore, in distributed frequency selection transmission, the receiving node needs to perform frequency selection negotiation using the networking control time slot based on the spectrum sensing and spectrum evaluation results, so as to actively select the communication frequency and notify the selected frequency to those neighbor nodes that will send data to this node.

[0069] Let the M frequency channels available for node data transmission in a wireless ad hoc network be represented as the frequency set F(M) = {f1, f2,..., f M}). Let N(u) represent the set of one-hop neighbor nodes of node u, and |A| represent the number of elements in set A.

[0070] The method steps for frequency selection negotiation between a node and its neighbor nodes are as follows:

[0071] Step S101: Each node in the wireless ad hoc network preliminarily filters out non-interfering frequencies according to the spectrum sensing and spectrum evaluation results. For node i, for each frequency f in the frequency set F(M) j (1 ≤ j ≤ M), filter out the frequency points that satisfy the condition E(i, f j ) ≥ E th . The remaining frequency set is represented as F1. Due to different environments at different nodes, the obtained frequency set F1 will be different. The frequency set obtained by node i is represented as F1(i).

[0072] Step S102: Each node in the wireless ad hoc network separately filters out frequencies with better quality from the obtained remaining frequency set F1. For node i, for each frequency f in the frequency set F1(i)j (1 ≤ j ≤ |F1(i)|), eliminate the frequency points that satisfy condition B n (i, f j ) ≥ B th , where B th represents the acceptable noise threshold, and the remaining frequency set is denoted as F2(i).

[0073] Step S103: Each node checks whether the remaining frequency set F2(i) is empty, that is, whether there is a frequency available. For node i, determine whether the condition |F2(i)| ≥ 1 is satisfied. When the condition is satisfied, it indicates that there is at least one frequency in the frequency set F2(i), that is, the node has at least one frequency available for communication reception, and the next step is executed. If the condition is not satisfied, the acceptable noise threshold B th in step S102 can be adjusted again th , and step S102 is repeated to enable the node to select a frequency with relatively good quality. The adjustment range of the acceptable noise threshold B

[0074] depends on the tolerance of the wireless ad hoc network to the ambient noise floor. Different network designs can have different threshold adjustment settings.

[0075] Step S104: Each node in the wireless ad hoc network uses its respective network control time slot to broadcast and announce the selected frequency set F2 to all one-hop neighbor nodes. The frequency set announced by node i is F2(i).

[0075] Step S105: Each node receives the frequency sets announced by neighbor nodes and stores them in the local memory for subsequent use by this node to perform frequency selection data transmission to neighbor nodes. The frequency set F2(i) received by node k from the broadcast announcement of node i is denoted as F2(k, i), and obviously F2(k, i) = F2(i).

[0076] Fourth aspect, time-frequency resource scheduling based on frequency selection

[0077] To make full use of the frequency selection results of nodes for network communication, it is also necessary to combine with the frequency selection results in the scheduling use of data transmission time slots. When a node performs data transmission to a neighbor node, it needs to occupy a certain number of data transmission time slots. Since the channel resources are very limited, usually the wireless ad hoc network needs to design a scheduling algorithm to dynamically allocate the use of data transmission time slots. For distributed frequency selection networking applications, this embodiment proposes a method based on two-dimensional time-frequency resource scheduling, which effectively supports the broadcast and unicast data transmission of nodes to neighbor nodes. The two-dimensional time-frequency resource is composed of a time slot s and the corresponding frequency f, which is simply referred to as time-frequency resource. During the time-frequency resource scheduling process, when a node allocates a data transmission time slot, it needs to clarify the frequency used for sending in this data transmission time slot.

[0078] The time-frequency resource scheduling is divided into three processes: resource application, neighbor response, and occupancy notification.

[0079] The method steps of the resource application are as follows:

[0080] Step S201: The node calculates the required number of data transmission time slots according to the service sending requirement, the amount of data R to be sent per unit time, and the data size D_Size that the node can send within a unit time slot. For the convenience of calculation, the unit time here can adopt the cycle duration of the time slot scheduling, that is, the instant frame length. Then the required number of data transmission time slots of the node can be calculated as:

[0081]

[0082] where, The operator represents rounding up.

[0083] Step S202: According to the calculation result of the required number of data transmission time slots of the node, assuming that the node needs m data transmission time slots, randomly select m data transmission time slots in the TDMA instant frame for application. The selected data transmission time slots exclude the time-frequency resources that have been notified to be occupied by the node itself and each neighbor node. The occupancy status of a time-frequency resource is represented by a quadruple (Tran_ID, Recv_ID, Slot_Num, Freq), where Tran_ID represents the sending node ID (node identity), Recv_ID represents the receiving node ID, Slot_Num represents the time slot number, and Freq represents the frequency used. The time slot s and frequency f selected by node i for application are required to meet the following conditions:

[0084] ① Node i has no sending or receiving operation in time slot s.

[0085] ② Among any neighbor nodes j of node i, that is, j ∈ N(i), no node j notifies the receiving status (d, j, s, f), where d represents any node.

[0086] ③ The target receiving node j for which node i applies for time slot s to send r does not notify the receiving status (d, j r , s, f arb ), where f arb represents any frequency.

[0087] ④ The target receiving node j for which node i applies for time slot s to send r does not notify the sending status (j r , d, s, f arb ).

[0088] Step S203: After the node selects the applied time-frequency resource, it broadcasts and sends the application information through the network control time slot inherent to this node. The application information includes: the sending node ID, the receiving node ID, the time slot number, and the sending frequency. Similarly, the application information for a time-frequency resource can also be represented by a quadruple (Tran_ID, Recv_ID, Slot_Num, Freq).

[0089] For the time-frequency resource application announced by the node, the neighbor nodes will respond according to whether the resource application will cause a conflict at the receiving node. The method steps of the neighbor response are as follows:

[0090] Step S301: All neighbor nodes receive the application information announced by the sending node in the network control time slot. Each node in the wireless ad hoc network sends its own application information in the network control time slot inherent to this node, and also receives the transmissions of other nodes in other network control time slots, collects all the received application information and stores it locally.

[0091] Step S302: After each node receives the application information broadcast and sent by the neighbor node, it will judge whether the application is approved according to the information it has, and give the corresponding response information. For the time-frequency application announced by node i (i, j r , s, f), when any of the following conditions exists, the neighbor node j will send a negative response to node i:

[0092] ① Among the neighbor nodes k of node j, there is k ∈ N(j) and k ≠ i, and there exists a time-frequency application (k, j, s, f), resulting in multiple time-frequency applications conflicting at node j. Node j performs a Hash calculation for each time-frequency application, using the application information (Tran_ID, Recv_ID, Slot_Num, Freq) and the TDMA frame sequence number as inputs, compares the calculation results, and when the Hash value corresponding to the time-frequency application (i, j r , s, f) is not the smallest, a negative response is made. The purpose of the Hash calculation is to perform fair response processing for multiple applications. Any Hash algorithm can be used for design, and each node uses the same Hash algorithm.

[0093] ② Among the neighbor nodes k of node j, there is k ∈ N(j) and k ≠ i, and it is announced that there is time-frequency occupancy (k, j, s, f).

[0094] ③ In particular, j = j r , node j r itself has sent an application for time slot s (j r , d, s, f arb ), d represents any node, and f arb represents any frequency.

[0095] ④In particular, j = j r , node j r itself will announce the reception status regarding time slot s (d(i), j r , s, f arb ), where d(i) represents any node other than node i.

[0096] ⑤In particular, j = j r , node j r among the neighbor nodes k of, there is k ∈ N(j r ), and k ≠ i, announce the existence of time-frequency occupation (k, d, s, f), where d represents any node.

[0097] For receiving node j r , when the above negative response condition does not occur, node j r needs to feedback a positive response to the requesting node i, indicating the reception of the transmission from node i through frequency f in time slot s.

[0098] Step S303: According to the response information given by the node, broadcast a response announcement outward during the next inherent networking control time slot transmission opportunity of this node.

[0099] The resource application needs to further determine whether it is successful according to the responses given by the neighbor nodes, and the relevant nodes will announce the occupation of the resources. The method steps of the occupation announcement are as follows:

[0100] Step S401: The node receives the response announcements from the neighbor nodes and extracts the response information related to the time-frequency application information of this node. For the time-frequency application (i, j r , s, f) announced by node i, the relevant response information includes the positive response from node j r , and the negative responses from the neighbor nodes other than j r nodes.

[0101] Step S402: According to the response information from the neighbor nodes, when either of the following two conditions is met, the time-frequency application of node i is granted, otherwise it is not granted:

[0102] ①When j r is a broadcast, node i does not receive any negative responses from neighbor nodes j (j ∈ N(i));

[0103] ②When j r is a unicast, node i does not receive any negative responses from neighbor nodes j (j ∈ N(i)), and receives a positive response from node j r .

[0104] When the time-frequency application is granted, in the next time frame, node i will occupy time slot s and use frequency f to transmit to node j r for transmission.

[0105] Step S403: According to the service transmission requirements of node i, the node continuously uses the allocated time slot for transmission. In order to continuously maintain the allocation and occupancy of time slot s, node i continuously announces the time slot transmission status (i, j r , s, f) in the inherent networking control time slot transmission opportunity, and node j r continuously announces the time slot reception status (i, j r , s, f) in the inherent networking control time slot transmission opportunity until node i no longer needs to occupy the allocated time slot for transmission.

[0106] Fifth aspect, frequency selection optimization based on data transmission

[0107] The node uses the obtained time-frequency resources (i, j r , s, f) for data transmission. During the data transmission process, receiving node j r further evaluates whether the selected frequency f meets the transmission requirements by statistically calculating the frame error rate. When the frame error rate is high and the data transmission between nodes cannot be effectively executed, receiving node j r will update the frequency selection set F2 announced in step S104, thereby triggering sending node i to re-select new time-frequency resources for application and transmission.

[0108] Next, a specific embodiment will be given in combination with an example of a multi-hop topology wireless ad hoc network to further illustrate the method of the present invention. It should be noted that here a typical network example is used as a reference scenario to specifically illustrate the implementation manner and operation process of the technical solution of the present invention, but the method of the present invention is not limited to being used in this example network.

[0109] As Figure 5 shown, an example of a multi-hop topology wireless ad hoc network, where the linked dotted lines represent the neighbor nodes that can be reached by a one-hop transmission of the node, and the numbers in the circles represent the node numbers ID. In the example, 7 nodes form a multi-hop mesh-connected wireless ad hoc network.

[0110] Assume that there are a total of M = 8 frequency channels available for use within the working frequency band of the nodes in this wireless ad hoc network. Affected by random interference, different nodes, according to the spectrum sensing and evaluation of their respective environments, and through frequency selection negotiation operations based on neighbor nodes, clarify the available non-interference frequency set F2(i), as shown in Table 1 respectively. It can be seen that there is interference in each frequency in this wireless ad hoc network. If the traditional frequency selection method with unified network-wide frequencies is adopted, effective working frequencies cannot be selected for the network.

[0111] Table 1. Frequency set F2(i) of each node in the exemplary wireless ad-hoc network:

[0112]

[0113]

[0114] By using the method of the present invention, each node broadcasts the frequencies included in the frequency set F2(i) to the surrounding neighbor nodes through the networking control time slot, and synchronously by receiving these announcements, the node can know the frequencies that can be selected when sending a time slot to a certain neighbor node.

[0115] Assume that nodes 1 and 4 in the wireless ad-hoc network have successfully applied for and occupied some data transmission time slots in the early stage, and nodes 2, 3, and 5 have new service sending requirements, and a new round of time-frequency resource application operations is performed. The time-frequency occupation and time-frequency application information of the relevant nodes are shown in Table 2. For node 2, according to step S202, time slot s1 does not meet the application conditions, so time slot s1 cannot be selected for application. According to the available frequency F2(3) announced by node 3 received, node 2 randomly selects the time-frequency resources - time slot s2 and frequency f4 for application. Similarly, nodes 3 and 5 select the time-frequency resources (s3, f6), (s1, f1), (s4, f4), (s5, f6) for application. In particular, in the time-frequency application (5, 0, s5, f6), the receiving node 0 indicates that node 5 needs to use this time-frequency resource to broadcast to all neighbor nodes.

[0116] Table 2. Time-frequency occupation and time-frequency application information of each node in the exemplary wireless ad-hoc network:

[0117]

[0118] The time-frequency application information is broadcast through the networking control time slots of the nodes. The neighbor nodes that receive the time slot application information will respond according to the information they have collected, including positive responses and negative responses. Step S302 is executed. After each neighbor node receives the application information, according to the condition judgment, the response results are shown in Table 3. Taking the response of the neighbor nodes to the application of Node 5 as an example: For the application (5, 3, s1, f1), since Node 1 announces the existing time-frequency occupancy (1, 2, s1, f1), which will cause a channel resource conflict and prevent Node 3 from effectively receiving the signal sent by Node 5, so Node 3 gives a negative response; for the application (5, 4, s4, f4), the receiving Node 4 gives a positive response, indicating that it will receive the transmission from Node 5 at frequency f4 in time slot s4; for the application (5, 0, s5, f6), none of the neighbor nodes give a negative response, and through positive responses, it means that this node can effectively receive the broadcast transmission from Node 5.

[0119] Table 3. Response information of each node in the example wireless ad hoc network:

[0120]

[0121] The response information shown in Table 3 will be broadcast through the networking control time slots of each relevant node. The node corresponding to the initiated time-frequency application will determine whether the application is permitted by the neighbor nodes according to the responses given by the neighbor nodes. According to the judgment method in Step S402, except that the application (5, 3, s1, f1) of Node 5 is given a negative response by neighbor node 3, the rest of the applications are successful, and there is no conflict in the time-frequency resource scheduling and use among the nodes in this wireless ad hoc network, realizing the time-frequency resource scheduling based on frequency selection. After the application is successful, the node will announce the occupancy through the networking control time slot in the next time frame and use the time-frequency resources of the corresponding application for data transmission to realize the transmission of service data.

[0122] The above is only the preferred embodiment of the present invention and is not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A multi-hop wireless self-organizing network centerless distributed frequency selection networking transmission method, characterized in that: include: Network control based on service frequency hopping channels: divide the channel time into a continuous and periodically repeated time frame structure; in each time frame period, the channel is further divided into several time slots, and the time slots are classified into spectrum sensing time slots, networking control time slots and data transmission time slots according to the usage type; Spectrum sensing and spectrum evaluation: In the spectrum sensing time slot, frequency channels are screened by spectrum sensing and spectrum evaluation; Neighbor-based frequency selection negotiation: Based on spectrum sensing and spectrum evaluation results, the node and neighbor nodes use the networking control time slot to negotiate frequency selection. Frequency resource scheduling based on frequency selection: After completing the frequency selection negotiation, the time and frequency resource scheduling is performed for the data transmission time slot; Frequency selection optimization based on data transmission: data transmission is performed based on the time-frequency resource scheduling, and frequency selection is optimized according to the data transmission situation.

2. The multi-hop wireless self-organizing network centerless distributed frequency selection networking transmission method according to claim 1 is characterized in that: The functions of the spectrum sensing time slot, networking control time slot and data transmission time slot are as follows: The spectrum sensing time slot is used by each network node to perform spectrum sensing and obtain available spectrum information in the current working environment; The networking control time slot is used for reliable interaction of networking control and distributed frequency selection information among various network nodes; The data transmission time slot is used by each network node to transmit service data information to a neighboring node using the selected frequency according to its own service communication needs, supporting various types of service transmission services.

3. The multi-hop wireless self-organizing network centerless distributed frequency selection networking transmission method according to claim 1, characterized in that: The screening of frequency channels by spectrum sensing and spectrum evaluation includes: In the spectrum sensing time slot, the node performs spectrum sensing on the frequency channels within the working frequency band and uses the receiver to detect the signals on each frequency channel. The signal spectrum energy received on each frequency channel is quantized and graded through digital signal processing. E(i,f) represents the signal spectrum energy obtained by the spectrum sensing of the node i on the frequency channel f. th Indicates the threshold setting for interference detection. When E(i,f)≥E th When , it is determined that there is interference on the frequency channel f, otherwise there is no interference, and the corresponding frequency channel can be used for node frequency selection; In the absence of obvious interference, the node senses the spectrum energy of the surrounding environment through the receiver and obtains the receiver environment noise floor B of node i for frequency channel f n (i,f), let the receiver noise floor of node i for frequency channel f be R n (i,f), for node reception, when the receiver environment noise floor is lower than the receiver noise floor, the node wireless reception can work normally. In this way, the spectrum quality is evaluated through environmental noise floor analysis, and the frequency channel with better spectrum quality is selected for communication.

4. The multi-hop wireless self-organizing network centerless distributed frequency selection networking transmission method according to claim 3 is characterized in that: Assume that the M frequency channels available for node data transmission in a wireless ad hoc network are represented by a frequency set F(M) = {f1, f2, ..., f M }, N(u) represents the set of one-hop neighbor nodes of node u, |A| represents the number of elements in set A; The node and the neighboring node perform frequency selection negotiation based on spectrum sensing and spectrum evaluation results using the networking control time slot, including: Step S101: Each node in the wireless self-organizing network preliminarily screens non-interference frequencies according to spectrum sensing and spectrum evaluation results; For node i, for each frequency f in the frequency set F(M) j , 1≤j≤M, remove those that meet the condition E(i,f j )≥E th The remaining frequency set is denoted as F1(i); Step S102: Each node in the wireless ad hoc network selects a frequency with better quality from the remaining frequency set obtained; for node i, for each frequency f in its remaining frequency set F1(i), j , 1≤j≤|F1(i)|, remove those that meet condition B n (i,f j )≥B th The frequency point, where B th represents the acceptable noise threshold, and the remaining frequency set is denoted as F2(i); Step S103: Each node checks whether the remaining frequency set F2(i) is empty, that is, whether there is a frequency available; for node i, determine whether the condition |F2(i)|≥1 is satisfied; when the condition is satisfied, it indicates that there is at least one frequency in the frequency set F2(i), that is, the node has at least one frequency available for communication reception, and the next step is executed; if the condition is not satisfied, the acceptable noise threshold B in step S102 is adjusted again th , and repeat step S102 until the condition is met; Step S104: each node in the wireless ad hoc network uses its own networking control time slot to broadcast and notify all one-hop neighboring nodes of the selected frequency set F2, and the frequency set broadcast and notified by node i is F2(i); Step S105: Each node receives the frequency set notified by the neighboring node and stores it in the local memory for subsequent frequency selection data transmission from the node to the neighboring node.

5. The multi-hop wireless self-organizing network centerless distributed frequency selection networking transmission method according to claim 4 is characterized in that: The time-frequency resource scheduling is based on time-frequency two-dimensional resource scheduling, including resource application, neighbor response and occupancy notification; the time-frequency two-dimensional resource is composed of a combination of time slot s and corresponding frequency f; during the time-frequency resource scheduling process, when a node allocates a data transmission time slot, it is necessary to clearly specify the frequency used to send in the data transmission time slot.

6. The multi-hop wireless self-organizing network centerless distributed frequency selection networking transmission method according to claim 5, characterized in that: The resource application includes: Step S201: The node calculates the number of data transmission time slots required according to the service transmission requirements, the amount of data R required to be transmitted per unit time, and the data size D_Size that the node can transmit per unit time slot; Step S202: Based on the calculation result of the number of data transmission time slots required by the node, assuming that the node needs m data transmission time slots, m data transmission time slots in the TDMA time frame are randomly selected for application, wherein the selected data transmission time slots and frequencies are required to exclude the time and frequency resources that have been notified by the node itself and each neighboring node as occupied; Step S203: After the node selects the time-frequency resources to apply for, it broadcasts the application information outward through the node's inherent networking control time slot.

7. The multi-hop wireless self-organizing network centerless distributed frequency selection networking transmission method according to claim 6, characterized in that: The neighbor response includes: Step S301: All neighboring nodes receive the application information announced by the sending node in the networking control time slot; Step S302: After receiving the application information broadcasted by the neighboring node, each node will determine whether the application is approved based on the information it has, and give corresponding response information; Step S303: According to the response information given by the node, a broadcast response notification is made in the next networking control time slot transmission opportunity inherent to the node.

8. The multi-hop wireless self-organizing network centerless distributed frequency selection networking transmission method according to claim 7, characterized in that: The occupancy notice includes: Step S401: The node receives a response notification from a neighboring node, and extracts the response information related to the time and frequency application information of the node; Step S402: judging whether the time and frequency application of the node is approved according to the response information from the neighboring node. If the time and frequency application is approved, in the next time frame, the node will occupy the time slot s and use the frequency f to transmit data to the receiving node; Step S403: According to the service transmission requirements of node i, the node continues to use the time slot applied for for transmission; wherein, node i continuously announces the time slot transmission status in the inherent networking control time slot transmission opportunity, and the receiving node continuously announces the time slot reception status in the inherent networking control time slot transmission opportunity until node i no longer needs to occupy the allocated time slot for transmission.

9. The multi-hop wireless self-organizing network centerless distributed frequency selection networking transmission method according to claim 8, characterized in that: The optimizing of frequency selection according to the data transmission situation includes: During the data transmission process, the receiving node evaluates whether the selected frequency meets the transmission requirements by counting the frame error rate; when the frame error rate is high and the data transmission between nodes cannot be effectively executed, the receiving node will update the frequency set F2 announced in step S104, thereby triggering the sending node i to reselect new time-frequency resources for application and transmission.

10. A multi-hop wireless self-organizing network, characterized in that: The multi-hop wireless self-organizing network includes a number of nodes; The plurality of nodes use the multi-hop wireless self-organizing network centerless distributed frequency selection networking transmission method as described in any one of claims 1-9 to transmit data.

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