Improved AODV routing method for ocean cross-medium acoustic-electric cooperative network

Abstract

The invention belongs to the technical field of ocean cross-medium acoustic-electric cooperative network communication, and discloses an improved AODV routing method for an ocean cross-medium acoustic-electric cooperative network, and the method comprises the steps: introducing a link stability factor of radio and underwater acoustic transmission when a route is established; the water surface cross-medium node specifies related equipment for data transmission according to the type of the destination node; after the node receives the routing response and establishes the routing, setting to send a HELLO packet at regular time for routing maintenance, and not sending the HELLO packet by other nodes which do not establish the routing; and after receiving the routing request, the underwater destination node continuously sends two routing responses to the source node. According to the method, a routing establishment and maintenance mechanism is improved, acoustic-electric weighted hops and link stability factors are introduced, the problems that underwater propagation packet collision is caused by too many traditional AODV notification packets, the packet delivery rate is low and the time delay is large due to the fact that the minimum hops serve as the principle are solved, the network time delay is reduced, and the packet delivery rate and throughput of integrated networking are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of marine cross-medium acoustic and electric cooperative network communication, and relates to a communication ad hoc network routing protocol, and in particular to a routing protocol for a cross-medium acoustic and electric cooperative communication network, and in particular to an improved AODV routing method for a marine cross-medium acoustic and electric cooperative network. Background Art

[0002] The marine cross-medium acoustic-electric collaborative network integrates hydroacoustic and radio communication methods. Nodes such as unmanned underwater vehicles (AUVs) and sensors below the sea surface use hydroacoustic communication, while nodes such as buoys and ships on the sea surface integrate both hydroacoustic and radio communication methods to achieve cross-medium communication. Equipment such as drones above the sea surface use radio for communication. The network uses a self-organizing network protocol to connect underwater, surface, and air nodes into an interconnected three-dimensional information network, providing an effective technical means for real-time sharing of marine information.

[0003] In the acoustic-electric cooperative network, information is transmitted above the sea surface by radio, and information is transmitted below the sea surface by underwater acoustics. These two transmission methods are quite different in terms of transmission rate, delay, etc. There are two main methods for acoustic-electric cooperative routing protocols: networking of different media separately and integrated networking of acoustic-electric cooperative. In terms of networking of different media separately, Yang Yuxuan proposed a hop-based underwater acoustic routing protocol MAVOR, which uses multiple buoy nodes and replaces the distance from underwater nodes to the surface of the water with the number of hops from underwater nodes to ocean surface nodes, so that the data packets generated by underwater nodes reach the surface buoy nodes in the direction of the minimum number of hops. In the surface forwarding stage, the radio opportunistic routing protocol is adopted. This routing protocol can only realize one-way information transmission. Ding Jiannan et al. proposed a cross-media adaptive routing strategy, in which the AODV routing protocol is used on the surface using ground radio, and the HH-VBF routing protocol is used underwater to realize acoustic-electric cooperative transmission. Before transmission, the source node will calculate the transmission delay of different links to determine whether to choose the above-water link or the underwater link, but this method requires obtaining the location information of the destination node before the source node sends data. Liu Yangfei proposed a study on the opportunistic routing algorithm of the marine acoustic-electric cooperative network, and designed a forwarding selection method based on depth weighting and node residual energy in underwater routing. In view of the problem of data forwarding mechanism of surface buoy nodes, a location-based priority sorting method was proposed. However, this routing method can only realize one-way information transmission.

[0004] In terms of integrated networking routing, Tan Yanjie proposed flood routing for acoustic-electric coordination and radio-priority forwarding routing, detailed the principle of the radio-priority forwarding routing protocol, and improved the RREQ and RREP frame formats, adding node load and residual energy as the basis for node forwarding judgment. Jiang Zilong conducted simulation analysis of the performance of AODV and OLSR in acoustic-electric coordination networks. However, these routing methods have high overhead and are prone to cause channel conflicts during underwater acoustic transmission.

[0005] At present, most of the routing strategies for networking different media separately can only achieve one-way transmission from underwater to surface, or the source node needs to obtain the location information of the destination node before sending data, which is difficult to apply in practice. Most of the integrated networking routing currently directly applies the traditional radio self-organizing network routing algorithm to the acoustic-electric cooperative network, which has problems such as high overhead and poor adaptability to the underwater environment.

[0006] Through the above analysis, the problems and defects of the prior art are as follows:

[0007] (1) At present, most of the routing strategies that use different media to form networks can only achieve one-way transmission from underwater to surface, or the source node needs to obtain the location information of the destination node before sending data, which makes practical application difficult.

[0008] (2) Most of the existing integrated networking routing currently directly applies the traditional radio self-organizing network routing algorithm to the acoustic-electric collaborative network, which has problems such as high overhead and poor adaptability to underwater environments. Summary of the invention

[0009] In order to overcome the problems existing in the related art, the disclosed embodiment of the present invention provides an improved AODV routing method for an ocean cross-medium acoustic-electric cooperative network, and the technical solution is as follows:

[0010] The present invention is implemented as follows: an improved AODV routing method for an ocean cross-medium acoustic-electric cooperative network includes route search, route reply, and route maintenance;

[0011] When establishing the route, the link stability factor of radio and underwater acoustic transmission is introduced; after the route is established, each node determines whether the route is invalid by whether it can receive the HELLO packets regularly broadcast by its neighbors;

[0012] The surface cross-medium node specifies the device for data transmission according to the type of the destination node; when the hydroacoustic device of the cross-medium node receives the routing request information, if the destination node is an aerial node, it is directly forwarded through the radio device of the buoy; when the destination node is an underwater node, if the surface cross-medium node receives the routing request from the underwater node, the routing request is forwarded by the radio device; if the radio device of the surface cross-medium node receives the routing request, the routing request is forwarded simultaneously through the hydroacoustic device and the radio device;

[0013] After the node receives the routing response and establishes the route, it sets a timer to send HELLO packets for route maintenance. Nodes that have not established routes do not send HELLO packets.

[0014] After receiving the routing request, the underwater destination node sends two routing responses to the source node in succession.

[0015] Further, route search includes:

[0016] (1) When the source node has data to send to the destination node, the source node checks whether there is a route to the destination node. If so, the data is sent directly; if not, the source node sends a route request RREQ to start establishing the route;

[0017] (2) When a node receives a routing request, it determines whether the survival hop count TTL of the routing request is a finite value. If not, it is discarded. If it is a finite value, it calculates the distance between the node and the previous hop node and the single-hop link stability factor RQ value. It adds the RQ value to the total support value ALLRQ in RREQ and divides it by the number of hops to obtain the average link quality AVGRQ.

[0018] (3) The node determines whether it has received an RREQ with the same ID. If not, it directly stores or updates the path to the source node in the routing table. If it has received an RREQ with the same ID, it determines whether AVGRQ is greater than the value in the existing routing table. If so, it stores or updates the path to the source node in the routing table. If AVGRQ is not greater than the value in the existing routing table, it discards the routing request.

[0019] (4) Determine whether it is the destination node or whether there is a path to the destination node. If so, send two routing response RREPs to the source node. When the source node receives the RREPs, the route establishment is complete.

[0020] (5) If the node is not the destination node or there is a path to the destination node, determine whether the node is a buoy node;

[0021] (6) If the node is a buoy node, determine whether the node receives an RREQ from an underwater acoustic device. If so, subtract b from the routing request survival hop count TTL, and the node continues to broadcast the RREQ using radio. The next-hop node continues to execute step (2). If the node does not receive an RREQ from an underwater acoustic device, determine whether the destination node is an underwater node. If not, subtract b from the node routing request survival hop count TTL, and broadcast the RREQ using radio. The next-hop node continues to execute step (2). If the destination node is an underwater node, subtract b from the node routing request survival hop count TTL, and continue to broadcast the RREQ using radio. At the same time, subtract a from the node request survival hop count TTL, and broadcast the RREQ using underwater acoustic. The next-hop node continues to execute step (2). a is the one-hop weight coefficient of the underwater acoustic sensor node, and b is the one-hop weight coefficient of the radio node.

[0022] (7) If the node is not a buoy node, determine whether the node is an underwater acoustic node. If so, subtract a from the node request survival hop count TTL, and continue to broadcast the RREQ using underwater acoustic. The next-hop node continues to execute step (2). If the node is not an underwater acoustic node, subtract b from the node routing request survival hop count TTL, and broadcast the RREQ using radio. The next-hop node continues to execute step (2).

[0023] In step (1), the source node checks whether there is a route to the destination node, including: the routing request data packet contains the survival hop count TTL. If the route reply is not received for a long time, increase the survival hop count and continue to send the routing request.

[0024] In step (2), the number of hops passed by the routing request is the weighted hop count Hop, and the expression is:

[0025] Hop = a * Hop uw + b * Hop wr

[0026] In the formula, a is the one-hop weight coefficient of the underwater acoustic sensor node, Hop uw is the number of hops of the underwater acoustic node passed by the routing request, b is the one-hop weight coefficient of the radio node, and Hop wr is the number of hops of the buoy node or air node passed by the routing request;

[0027] Introduce the underwater acoustic transmission link stability factor RQ, and the calculation formula is as follows:

[0028]

[0029] In the formula, d is the distance between two underwater nodes, R represents the maximum underwater acoustic communication radius, w is the distance threshold coefficient, 0 < w < 1, and w × R represents the communication critical distance;

[0030] The total support value ALLRQ is the sum of the total RQ of radio and underwater acoustic communications on the path, and the expression is:

[0031]

[0032] In the formula, ALLRQ is the total support value, i represents the i-th node of the path, n represents the total number of nodes in the path, and RQ i represents the transmission link stability factor of the i-th node;

[0033] The average link quality AVGRQ is the ratio of the sum of all link stability factors in the path to the number of hops. The calculation formula is as follows:

[0034]

[0035] In the formula, n represents the total number of nodes on the path. The larger the AVGRQ value is, the higher the link quality is.

[0036] In step (3), the node determines whether it has received an RREQ with the same ID. The determination process is as follows:

[0037] 1) When a node receives a RREQ, it determines whether there is an ID number of the same RREQ as the source node and destination node of the RREQ in the RREQ record table. If so, the RREQ is discarded;

[0038] 2) When a node receives a RREQ, if it is the first time to receive the RREQ, it stores the RREQ ID number and the source node and destination node addresses of the RREQ in the RREQ record table.

[0039] In step (4), the node determines whether it is the destination node or there is a path to the destination node. The determination method is: whether the destination node IP address in the RREQ is the same as the IP address of the node;

[0040] The method for determining whether there is a path to the destination node is as follows: determining whether the routing table stores a path to the destination node;

[0041] In step (6), judging whether the information received from the hydroacoustic / radio interface is received by the hydroacoustic device or the radio device, and judging the node type according to the IP address of the destination node;

[0042] In step (7), the node type is determined based on the node's IP address.

[0043] Further, the routing reply includes:

[0044] (1) If a network node receives a RREP packet, it determines whether there is a RREP packet with the same ID and the same destination node in the message list. The determination process of the RREP packet with the same ID is as follows: first determine whether there is the same RREQ ID number and the source node and destination node of the RREQ in the RREQ record table. If so, discard the RREQ; if it is the first time to receive the RREQ, store the RREQ ID number and the source node and destination node address of the RREQ in the RREQ record table; if not, update the destination node routing table and start periodically broadcasting HELLO packets; if there is a RREP packet with the same ID and the same destination node in the message list, read the AVGRQ in the RREP to determine whether it is greater than the AVGRQ value in the existing routing table. If not, discard the RREP packet; if it is greater than the AVGRQ value in the existing routing table, update the destination node routing table and start periodically broadcasting HELLO packets;

[0045] (2) Determine whether the node is a source node, and then determine whether the source node address in the RREP data packet is the local address. If they are the same, it is the source node; if so, the route establishment is completed; if not, unicast forward the RREP to the source node, and the next hop node continues to execute step (1).

[0046] Furthermore, after the route is established, each node on the path broadcasts a Hello packet regularly and starts executing the route maintenance steps, which include:

[0047] (1) The node determines whether it has received a Hello packet from a neighbor node regularly;

[0048] (2) If a Hello packet is received regularly from a neighbor node, no processing is done on the routing table;

[0049] (3) If the Hello packet from a neighbor node is not received regularly, determine whether there is a route with the next hop being the neighbor node in the routing table; if not, execute step (2); if so, delete the route and send a routing error RERR packet to the source node of the route;

[0050] (4) After receiving the RERR packet, the node determines whether there is an erroneous route in its own routing table. If not, no processing is done on the routing table. If so, the route is deleted.

[0051] (5) The node determines whether there is still a route in its routing table. If not, it stops broadcasting Hello packets periodically. If yes, it determines whether the node is a source node. If not, it unicasts the RERR to the source node. If not, it ends the routing maintenance process.

[0052] In step (1), the process of a node determining whether it has received a Hello packet from a neighbor node regularly is as follows: the node is set to broadcast a Hello packet every T seconds, and determines whether it has received a Hello packet from a neighbor node within every 2T seconds;

[0053] In step (3), based on the IP address of the neighboring node, the next hop IP address of each path in the routing table is retrieved to see whether it is the same as the IP address of the neighboring node;

[0054] In step (4), the destination node and next hop information of the path in the routing table are retrieved to see whether they are consistent with the information in the RERR packet.

[0055] In step (5), determine whether there are still routes in its own routing table, then determine whether the number of paths currently existing in the routing table is 0; determine whether the node is a source node, then determine whether it has the previous hop address of the path, if so, it is not a source node; if not, it is a source node.

[0056] In combination with all the above technical solutions, the advantages and positive effects of the present invention are as follows: in view of the problems of one-way transmission, high overhead, and poor adaptability to underwater environment in the routing algorithm of the current marine cross-media acoustic-electric collaborative network, the present invention proposes an optimized AODV Protocol for Cross-media Acoustic-wireless radio Collaborative Networks (CACN-OAODV) based on the traditional wireless ad hoc on-demand distance vector routing protocol (Ad hoc On-Demand Distance Vector Routing, AODV). The protocol takes into account the characteristics of both underwater acoustic and radio communication modes, improves the routing establishment and maintenance mechanism, introduces acoustic-electric weighted hops and link stability factors, solves the problems of too many traditional AODV notification packets leading to underwater propagation collisions, and the principle of minimum hops leading to low packet delivery rate and large delay, reduces network delay, and improves the packet delivery rate and throughput of integrated networking.

[0057] The CACN-OAODV protocol of the present invention has advantages over AODV in terms of packet delivery rate, throughput and delay; in the underwater to underwater node data transmission scenario, the CACN-OAODVV protocol packet delivery rate is improved by about 15%, the throughput is improved by an average of about 20bps, and the delay is reduced by an average of about 0.06 seconds; in the underwater to aerial node data transmission scenario, the CACN-OAODV protocol packet delivery rate is improved by about 9%, the throughput is improved by an average of about 12bps, and the delay is reduced by an average of about 0.24 seconds.

[0058] The present invention belongs to the field of marine cross-medium acoustic-electric cooperative network communication technology, and in particular, relates to a communication ad hoc network routing protocol in a marine cross-medium acoustic-electric cooperative network. This technical field is extremely important for the real-time sharing of marine information, the exploration and development of marine resources, marine environmental monitoring, and marine safety. The expected benefits include promoting the real-time sharing of marine information and promoting the innovative development of marine technology. It has important value in marine scientific research and resource development, marine environmental monitoring and protection, and marine safety.

[0059] The problems existing in the prior art mainly include that most of the routing strategies for networking different media separately can only realize one-way transmission from underwater to above water, or the source node needs to obtain the location information of the destination node before sending data, which makes practical application difficult; and most of the integrated networking routing currently directly applies the traditional radio self-organizing network routing algorithm to the acoustic-electric collaborative network, which has the problems of high overhead, adaptability to underwater environment, and poor adaptability when the communication node moves. The present invention effectively solves these problems. By improving the AODV routing method, two-way communication across media nodes is realized, and there is no need to obtain the location information of the destination node before the source node sends data. At the same time, the method also reduces network overhead and improves adaptability to underwater environments by optimizing routing algorithms and introducing link stability factors and other technical means.

[0060] The present invention introduces a number of innovative technologies in key steps such as route search, route reply, and route maintenance. These innovative technologies enable the present invention to overcome the limitations of the prior art and achieve two-way communication across media nodes without the need to obtain the location information of the destination node before the source node sends data. At the same time, the method also reduces network overhead and improves adaptability to underwater environments by optimizing routing algorithms and introducing link stability factors and other technical means. Through actual testing and experimental verification, the present invention has demonstrated good stability and reliability in cross-media communications, proving its effectiveness in overcoming technical bias. Compared with the prior art, the present invention has achieved significant advantages in communication efficiency, network overhead, and adaptability to underwater environments.

[0061] In summary, the technical solution of the present invention has indeed overcome technical prejudice and made important contributions to the development of the field of marine cross-medium acoustic and electrical collaborative network communication technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] The accompanying drawings herein are incorporated in and constitute a part of the specification, illustrate embodiments consistent with the present disclosure, and together with the description, serve to explain the principles of the present disclosure;

[0063] Figure 1 It is a flow chart of an improved AODV routing method for an ocean cross-medium acoustic-electric cooperative network provided by an embodiment of the present invention;

[0064] Figure 2 It is a CACN-OAODV route search flow chart provided by an embodiment of the present invention;

[0065] Figure 3 It is a CACN-OAODV routing reply flow chart provided by an embodiment of the present invention;

[0066] Figure 4 It is a CACN-OAODV routing maintenance flow chart provided by an embodiment of the present invention;

[0067] Figure 5 It is a topological structure diagram of an acoustic-electric collaborative network simulation scenario provided by an embodiment of the present invention;

[0068] Figure 6 is a simulation result diagram of radio node hop weight selection provided by an embodiment of the present invention;

[0069] Figure 7 is a graph showing the relationship between the underwater acoustic packet delivery rate and the distance between nodes provided by an embodiment of the present invention;

[0070] Figure 8 is a graph showing the relationship between the radio packet delivery rate and the distance between nodes provided by an embodiment of the present invention;

[0071] Fig. 9 It is a schematic diagram of underwater-underwater transmission packet delivery rate provided by an embodiment of the present invention;

[0072] Fig.10 Schematic diagram of underwater-to-air transmission packet delivery rate provided by an embodiment of the present invention;

[0073] Fig.11 is a schematic diagram of underwater-underwater transmission throughput provided by an embodiment of the present invention;

[0074] Fig.12 is a schematic diagram of underwater-to-air transmission throughput provided by an embodiment of the present invention;

[0075] Fig.13 Schematic diagram of underwater-underwater transmission delay provided by an embodiment of the present invention;

[0076] Fig.14 is a schematic diagram of underwater-to-air transmission delay provided by an embodiment of the present invention;

[0077] Fig.15 This is a topological diagram of the acoustic-electric collaborative network provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0078] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific implementation disclosed below.

[0079] The marine cross-media acoustic-electric cooperative network can be regarded as a heterogeneous mobile self-organizing network. There are three types of nodes in the network: aerial nodes, surface cross-media nodes, and underwater nodes. Nodes on and above the sea surface use radio for communication, underwater nodes use hydroacoustic communication, and surface cross-media nodes have both radio and hydroacoustic communication functions to achieve cross-media communication. All nodes are mobile, and different types of nodes move at different speeds. The topology of the acoustic-electric cooperative network is as follows: Fig.15 The following problems exist when the traditional AODV routing protocol is directly applied to the ocean cross-medium acoustic and electrical cooperative network:

[0080] First, when the source node sends data to the target node, it first establishes a path to the destination node through the AODV protocol routing discovery process. Each node stores the routing information in its own routing table, and a lifetime is set for each route in the routing table. If the route exceeds the lifetime, each node will delete the route from the routing table. The source node needs to re-initiate the routing request. If the route does not change, the information interaction in the routing process will lead to a waste of bandwidth and energy. At the same time, since the delay of underwater acoustic communication is longer than that of radio communication, this will also aggravate the conflict of underwater acoustic nodes. In addition, all nodes in the traditional AODV protocol will broadcast Hello packets for route maintenance. Even if the node is not on the transmission path, Hello packets are broadcast, which increases the burden on the underwater acoustic channel, resulting in a decrease in the data packet transmission rate of the entire acoustic-electric collaborative network.

[0081] Second, the traditional AODV protocol is based on the principle of minimum hop count. When a routing request is initiated for the first time, the hop count is set to a minimum initial value. If the routing response message is not received within the set waiting time, the source node will increase the lifetime and continue to send routing requests. Since the transmission speed of radio is much higher than that of underwater acoustics, the minimum hop count in the acoustic-electric cooperative network is not equivalent to the minimum delay. Therefore, the transmission speed and transmission delay of radio and underwater acoustics need to be considered in the acoustic-electric cooperative network to reduce the overall transmission delay.

[0082] Third, the position of each node in the acoustic-electric collaborative network is in a state of dynamic change. In the marine environment, the communication link is easy to break, especially when the intermediate node is located at the communication boundary of the adjacent node, the communication link is more unstable. Once a break occurs, the route needs to be re-established, which will affect the overall network transmission efficiency. Therefore, choosing a stable route is particularly important in the marine environment. When establishing a route, the distance factor between nodes can be considered to improve the packet delivery rate and throughput.

[0083] The present invention solves the problem of data packet collision caused by too many routing notification packets in the traditional AODV protocol. In the traditional AODV protocol, each node will set the routing validity period after the routing is established, and continuously send routing notification packets during this period to maintain the routing status. However, this method will cause packet collision problems when data is transmitted underwater, increasing the network burden. And in the traditional AODV protocol, when a cross-media node receives a routing request, it may forward the request indiscriminately, resulting in unnecessary network overhead. The present invention no longer sets the routing validity period, but relies on the HELLO packet broadcast by the node regularly to determine whether the route is invalid, thereby effectively reducing the sending of routing notification packets and reducing the risk of data packet collision. And by introducing a cross-media node intelligent data transmission mechanism, the corresponding device is selected for data transmission according to the type of the destination node (in the air or underwater), effectively reducing underwater overhead and improving communication efficiency.

[0084] The present invention solves the problem of large transmission delay and unstable link. Due to the large difference in transmission speed between underwater acoustics and radio, the traditional AODV protocol may increase the delay during route discovery due to too many hops. In addition, the traditional AODV protocol does not fully consider the stability of the link when establishing the route, which makes the link easy to disconnect in harsh environments (such as underwater), affecting the communication quality. The present invention introduces a weighted hop design to weight the hops according to the transmission speed of underwater acoustics and radio, thereby speeding up the route discovery speed and reducing the delay. And by introducing a link stability factor, the stability of the link is evaluated when the route is established, so that a more stable routing path can be selected, thereby improving the reliability and stability of communication.

[0085] The core innovation point of the present invention is: dynamic routing failure judgment and HELLO packet optimization;

[0086] Dynamic route failure judgment: Abandoning the traditional route validity period setting, the route failure is judged by whether the node can receive the HELLO packets broadcast regularly by the neighbors. This innovation improves the dynamics and accuracy of route judgment.

[0087] HELLO packet optimization: HELLO packets are sent periodically for route maintenance only after the node has established a route. Nodes that have not established a route do not send HELLO packets. This strategy significantly reduces the overall information interaction and alleviates the communication burden.

[0088] The second core innovation of the present invention: intelligent data transmission across media nodes;

[0089] Destination node type-guided data transmission: Based on the type of destination node (air or underwater), the cross-medium node can intelligently choose to transmit data via radio equipment or hydroacoustic equipment. This innovation effectively reduces underwater overhead and improves communication efficiency.

[0090] The third core innovation of the present invention: weighted hop count design;

[0091] Hop weighted design: A lifetime, i.e., the maximum number of hops, is set in the route request packet (RREQ), and the hops are weighted according to the difference in transmission speed between hydroacoustic and radio. The hop weight of the buoy radio equipment is lower, while the hop weight of the hydroacoustic equipment is higher. This design speeds up the route discovery and converts the minimum hop number into the minimum delay.

[0092] The fourth core innovation of the present invention: introduction of link stability factor;

[0093] Link stability factor: The link stability factor of radio and underwater acoustic transmission is introduced when establishing the route. By evaluating the stability of the link, the route selection is optimized, the stability of the route and the packet delivery rate are improved, and the problems of large transmission delay and unstable link are effectively addressed.

[0094] The innovative features of the present invention can be divided into:

[0095] 1. In order to solve the problem of packet collision in underwater data transmission caused by too many routing notification packets in the traditional AODV protocol, firstly, after the route is established, each node no longer sets the validity period of the route. Each node can determine whether the route is invalid by whether it can receive the HELLO packet broadcast regularly by its neighbors. Secondly, in the acoustic-electric collaborative routing protocol, the surface cross-medium node specifies the relevant equipment for data transmission according to the type of the destination node. When the hydroacoustic device of the cross-medium node receives the routing request information, if the destination node is an aerial node, it is directly forwarded through the radio equipment of the buoy, and the hydroacoustic device no longer forwards it, thereby reducing the underwater overhead; when the destination node is an underwater node, there are two situations. If the surface cross-medium node receives the routing request from the underwater node, the routing request is forwarded by the radio equipment; if the radio equipment of the surface cross-medium node receives the routing request, the routing request is forwarded by its hydroacoustic equipment and radio equipment at the same time. Thirdly, after the node receives the routing response and establishes the route, it is set to send HELLO packets regularly for route maintenance. Other nodes that have not established routes do not send HELLO packets, reducing the overall information interaction and reducing the communication burden. Finally, after receiving the routing request, the underwater destination node sends two consecutive routing responses (RREPs) to the source node to improve the success rate of routing establishment under unreliable communication links.

[0096] 2. To address the problems of large transmission delay and unstable link, there are two innovations.

[0097] (1) Set a lifetime in the route request packet (RREQ), that is, the maximum number of hops that the route request packet goes through. If the number of hops that the route request packet goes through exceeds this maximum hop value, the route request packet will not be forwarded. Due to the large difference in the transmission speed of underwater acoustics and radio, in order to convert the minimum number of hops into the minimum delay and speed up the route discovery speed, the number of hops can be weighted. The one-hop weight of the buoy radio equipment is lower, and the one-hop weight of the underwater acoustic equipment is higher. The number of hops that the route request goes through is the weighted hop number Hop, and its value is set as follows:

[0098] Hop=a*Hop uw +b*Hop wr (1)

[0099] Where a is the one-hop weight coefficient of the underwater acoustic sensor node, Hop uw is the number of hops of the hydroacoustic node through which the routing request passes, b is the one-hop weight coefficient of the radio node, and Hop wr is the number of buoy nodes or aerial nodes that the routing request passes through; coefficients a and b are obtained through empirical settings or optimization methods;

[0100] Using formula (1), the number of hops can be made positively correlated with the delay. Since the transmission speeds of underwater acoustic and radio in the acoustic-electric collaborative network are different, the traditional number of hops cannot be positively correlated with the delay. The minimum number of hops does not necessarily correspond to the minimum delay. Through the design of hop weighting, the number of hops is made positively correlated with the delay.

[0101] (2) When establishing the route, introduce the link stability factors of radio and underwater acoustic transmissions to increase the stability of the route and improve the packet delivery rate.

[0102] Introduce the single-hop link stability factor RQ of underwater acoustic transmission. The calculation formula is as follows:

[0103]

[0104] In the formula, d is the distance between two underwater nodes, R represents the maximum communication radius of underwater acoustic, w is the distance threshold coefficient; 0 < w < 1, w×R represents the critical communication distance. Beyond this distance, the communication link is unstable, which will lead to packet loss. The radio transmission link stability factor can also use the same expression, except that the coefficient w in the two communication link stability factors is different.

[0105] Formula (2)尽可能的解决了声电协同网络路径上存在两点处在临界通信范围的情况,与公式(3)联合使用,使声电协同网络建立的路径更稳定,尽量不出现路径上两点处在临界通信范围的情况,使源节点到目的节点的路径最稳定。

[0106] The total support value (ALLRQ) is the sum of the RQs of radio and underwater acoustic communications on this path.

[0107]

[0108] In the formula, ALLRQ is the total support value, i represents the i-th node of the path, n represents the total number of nodes in the path, and RQ i represents the transmission link stability factor of the i-th node;

[0109] Formula (3)尽可能的解决了声电协同网络路径上存在两点处在临界通信范围的情况,与公式(2)联合使用。利用公式(3)计算路径上所有节点的链路稳定因子的和,使声电协同网络建立的路径更稳定,尽量不出现路径上两点处在临界通信范围的情况,使源节点到目的节点的路径最稳定。

[0110] If a path contains multiple hop nodes, then when considering the definition of path quality, the number of hops needs to be considered. The average link quality (AVGRQ) is the ratio of the sum of all link stability factors in the path to the number of hops. The formula is as follows. The larger the AVGRQ value, the higher the link quality.

[0111]

[0112] In the formula, n represents the total number of nodes on the path. The larger the AVGRQ value is, the higher the link quality is.

[0113] Formula (4) solves the problem of two points in the critical communication range on the path of the acoustic-electric cooperative network as much as possible, making the total link factor and the overall number of hops optimal, and is used in conjunction with formula (3). Formula (4) is used to calculate the average value of the path link stability factor, so that the path established by the acoustic-electric cooperative network has fewer hops and is more stable, and the situation where two points on the path are in the critical communication range is avoided as much as possible, making the path from the source node to the destination node the most stable.

[0114] After the improvement, the routing request needs to include the coordinate information of the previous hop, and the message format is modified as shown in Table 1 and Table 2. The main innovation is to add "previous hop geographic location information" and "total support value ALLRQ" in the RREQ message, and add "average support value (AVGRQ)" in the RREP message. The number of hops in the two data packets is calculated according to formula (1).

[0115] Table 1 Route Request (RREQ) Packet Format

[0116]

[0117] Table 2 Routing Reply (RREP) Packet Format

[0118]

[0119] Implementation case, in the cross-media transmission scenario, when the underwater node has data to send to the destination node, the underwater node checks whether there is a route to the destination node. If "yes", the data is sent directly; if "no", the source node sends a route request (RREQ) to start establishing a route. The route request data packet contains the survival hop count TTL. If no route response is received for a long time, the survival hop count is increased and the route request is continued.

[0120] When other nodes receive a routing request, they first determine whether the survival hop count TTL of the routing request is a finite value. If not, discard it. If so, calculate the distance between this node and the previous hop node, and calculate the single-hop link stability factor (RQ) value, add the RQ value to the total support value (ALLRQ) value in the RREQ, and divide it by the number of hops to obtain the average link quality (AVGRQ). The node determines whether it has received the RREQ with the same ID. If not, directly store or update the path to the source node in the routing table. If yes, determine whether the AVGRQ is greater than the value in the existing routing table. If yes, store or update the path to the source node in the routing table. If not, discard the routing request.

[0121] Then determine whether it is the destination node or there is a path to the destination node. If it is not the destination node or there is no path to the destination node, if the node is a buoy node, determine whether the node has received RREQ from the hydroacoustic device. If it has received RREQ from the hydroacoustic device, the routing request survival hop count TTL minus b, and the node continues to broadcast RREQ using radio. If RREQ is not received from the hydroacoustic device, determine whether the destination node is an underwater node. If it is not an underwater node, the node routing request survival hop count TTL minus b, and uses radio to broadcast RREQ. If it is an underwater node, the node routing request survival hop count TTL minus b, and continues to broadcast RREQ using radio. At the same time, the node requests survival hop count TTL minus a, and continues to broadcast RREQ using hydroacoustic. If it is not a buoy node, determine whether the node is a hydroacoustic node. If it is a hydroacoustic node, the node requests survival hop count TTL minus a, and continues to broadcast RREQ using hydroacoustic. If it is an aerial node, the node routing request survival hop count TTL minus b, and uses radio to broadcast RREQ.

[0122] If the node is the destination node or there is a path to the destination node, two routing replies RREP are sent to the source node.

[0123] If a network node receives a RREP packet, it determines whether there is a RREP packet with the same ID and the same destination node in the message list. If not, it updates the routing table to the destination node and starts to broadcast HELLO packets periodically. If so, it reads the AVGRQ in the RREP and determines whether the value is greater than the AVGRQ value in the existing routing table. If not, it discards the RREP packet. If so, it updates the routing table to the destination node and starts to broadcast HELLO packets periodically. It determines whether the node is the source node. If it is the source node, the route is established; if it is not the source node, it unicasts the RREP to the continuing source node.

[0124] The above process realizes effective communication between underwater nodes and sea surface buoy nodes and aerial platforms in cross-media ocean communication. It reduces underwater communication overhead and improves communication efficiency. At the same time, it speeds up route discovery, reduces latency, improves route stability and packet delivery rate, and enhances network reliability. It solves the problems of high overhead, high latency and unstable links of traditional routing protocols in cross-media ocean networks.

[0125] like Figure 1 As shown, the improved AODV routing method for the marine cross-medium acoustic and electrical cooperative network provided by the embodiment of the present invention consists of search, route reply and route maintenance processes.

[0126] S1, when establishing the route, the link stability factor of radio and underwater acoustic transmission is introduced; after the route is established, each node determines whether the route is invalid by whether it can receive the HELLO packet broadcast regularly by its neighbors;

[0127] S2, the surface cross-medium node specifies relevant equipment for data transmission according to the type of the destination node; when the hydroacoustic device of the cross-medium node receives the routing request information, if the destination node is an aerial node, it is directly forwarded through the radio device of the buoy; when the destination node is an underwater node, if the surface cross-medium node receives the routing request from the underwater node, the routing request is forwarded by the radio device; if the radio device of the surface cross-medium node receives the routing request, the routing request is forwarded by the hydroacoustic device and the radio device at the same time;

[0128] S3, after the node receives the routing response and establishes the route, it sets a timer to send HELLO packets for route maintenance. Other nodes that have not established routes do not send HELLO packets;

[0129] S4, after receiving the routing request, the underwater destination node sends two routing responses to the source node in succession.

[0130] like Figure 2 As shown, the route search process provided by the embodiment of the present invention is as follows:

[0131] 1. When the source node has data to send to the destination node, the source node checks whether there is a route to the destination node. If yes, the data is sent directly; if no, the source node sends a route request (RREQ) to start establishing a route. The route request data packet contains the survival hop count TTL. If no route response is received for a long time, the survival hop count is increased and the route request is continued.

[0132] 2. When a node receives a routing request, it first determines whether the survival hop count TTL of the routing request is a finite value. If not, it is discarded; if so, the distance between the node and the previous hop node is calculated, and the single-hop link stability factor (RQ) value is calculated. The RQ value is added to the total support value (ALLRQ) value in RREQ, and divided by the number of hops to obtain the average link quality (AVGRQ);

[0133] 3. The node determines whether it has received the RREQ with the same ID. If not, it directly stores or updates the path to the source node in the routing table. If yes, it determines whether AVGRQ is greater than the value in the existing routing table. If yes, it stores or updates the path to the source node in the routing table. If not, it discards the routing request.

[0134] 4. The node determines whether it is the destination node or there is a path to the destination node. If so, it sends two routing response RREPs to the source node. When the source node receives the RREP, the route establishment is completed.

[0135] 5. If not, determine whether the node is a buoy node;

[0136] 6. If yes, determine whether the node has received RREQ from the hydroacoustic device. If yes, the routing request survival hop count TTL minus b, the node continues to broadcast RREQ using radio, and the next hop node continues to execute step 2. If no, determine whether the destination node is an underwater node. If no, the node routing request survival hop count TTL minus b, uses radio to broadcast RREQ, and the next hop node continues to execute step 2. If yes, the node routing request survival hop count TTL minus b, uses radio to continue broadcasting RREQ, and at the same time, the node requests survival hop count TTL minus a, uses hydroacoustic to continue broadcasting RREQ, and the next hop node continues to execute step 2.

[0137] 7. If not, determine whether the node is an acoustic node. If so, the node requests the survival hop count TTL minus a, uses acoustic broadcasting to continue broadcasting RREQ, and the next hop node continues to execute step 2. If not, the node routing requests the survival hop count TTL minus b, uses radio broadcasting RREQ, and the next hop node continues to execute step 2.

[0138] like Figure 3 As shown, the routing reply process provided by the embodiment of the present invention is as follows:

[0139] 1. If a network node receives a RREP packet, it determines whether there is a RREP packet with the same ID and the same destination node in the message list. If not, it updates the destination node routing table and starts to periodically broadcast HELLO packets. If yes, it reads the AVGRQ in the RREP and determines whether the value is greater than the AVGRQ value in the existing routing table. If not, it discards the RREP packet. If yes, it updates the destination node routing table and starts to periodically broadcast HELLO packets.

[0140] 2. Determine whether the node is the source node. If so, the route is established. If not, unicast the RREP to the source node, and the next hop node continues to execute step 1.

[0141] After the route is established, each node on the path broadcasts Hello packets regularly and starts the route maintenance process. Figure 4 As shown, the route maintenance process provided by the embodiment of the present invention is as follows:

[0142] 1. The node determines whether it has received a Hello packet from a neighbor node regularly;

[0143] 2. If yes, do not do anything with the routing table;

[0144] 3. If not, determine whether there is a route with the next hop being the neighbor node in the routing table; if not, execute step 2; if yes, delete the route and send a routing error RERR packet to the source node of the route.

[0145] 4. The node receives the RERR packet and determines whether there is an erroneous route in its routing table. If not, no processing is done on the routing table; if so, the route is deleted.

[0146] 5. The node determines whether there is still a route in its routing table; if not, it stops broadcasting the Hello packet periodically; if so, it determines whether the node is the source node, if not, it unicasts the RERR to the source node. If so, the routing maintenance process ends.

[0147] In order to further demonstrate the positive effects of the above embodiment, the present invention conducts the following experiments based on the above technical solution.

[0148] To describe the advantages of this routing protocol, a simulation scenario topology is constructed as follows: Figure 5 As shown in the figure, the network has 28 underwater nodes, 6 sea surface buoy nodes, and 3 aerial nodes. The topological structure of each node is shown in the figure 5 The specific simulation parameter settings are shown in Table 3.

[0149] Table 3 Simulation parameter settings

[0150]

[0151]

[0152] The present invention simulates the network performance of the above-mentioned acoustic-electric collaborative network using the traditional AODV and CACN-OAODV routing protocols in two transmission scenarios. The two scenarios are: the source node and the destination node are both located at a depth of 1000 meters underwater; the source node is located at a depth of 1000 meters underwater and the destination node is located in the air. The present invention analyzes the latency, throughput and packet delivery rate performance indicators brought by different routing protocols in these two scenarios.

[0153] The weight coefficients a and b in the weighted hop count in the CACN-OAODV routing protocol, and the critical communication distance w×R in the stability factor of the underwater acoustic and radio transmission links are determined by simulation experience values ​​in the present invention.

[0154] Since the transmission speed of radio is much faster than that of underwater acoustics, the underwater acoustic node hop weight a is set to 1; the radio node hop weight b is set to 0.25, 0.5, 0.75, and 1 respectively, and the simulation test of route establishment time is carried out to record the time of establishing acoustic-electric collaborative routing with different radio hop weights. The simulation results are shown in Figure 2. Figure 6 As shown, when b=0.5, the route establishment time is the shortest, so b is set to 0.5 in the example.

[0155] Regardless of underwater acoustic communication or radio communication, at the critical distance, the point-to-point packet delivery rate cannot reach 100%. Next, the critical distances of the two communication methods are simulated to determine the w value in the link stability factor of the two communication methods. The critical distances of the two nodes are simulated using underwater acoustic and radio communication methods, and 900 data are sent. The simulation results of the data packet delivery rate are as follows: Figure 7 and Figure 8 shown.

[0156] like Figure 7 As shown in the figure, the maximum communication radius R of underwater acoustic transmission is 2200m. When it is greater than 2000m, packet loss begins to occur. Therefore, the critical distance is 2000m, corresponding to w is about 0.91, so w=0.91 is set. The link stability factor in the underwater acoustic transmission link is:

[0157]

[0158] like Figure 8 As shown in the figure, the maximum radio communication radius is 7800m. When the distance between two nodes is greater than 7600m, packet loss begins to occur. Therefore, the critical distance is 7600m, and the corresponding w is about 0.97, so w=0.97 is set. In this regard, the calculation formula of the link stability factor in the radio transmission link is as follows:

[0159]

[0160] After setting the above parameters, we then analyze the network latency, throughput, and packet delivery rate performance indicators of the two routing protocols, traditional AODV and CACN-OAODV, in the two scenarios of underwater node-underwater node and underwater node-air node.

[0161] a. Packet delivery rate: The packet delivery rate in the above two scenarios is as follows Fig. 9 and Fig.10 As shown. In both scenarios, the packet delivery rate of the CACN-OAODV routing protocol is higher than that of the AODV protocol. The underwater-underwater transmission scenario is about 15% higher than the traditional AODV, and the underwater-air scenario is about 9% higher than the traditional AODV. This is because the improved AODV routing protocol effectively controls the number of routing data packets and reduces the probability of channel conflicts in the underwater acoustic channel space. At the same time, the destination node replies to the RREP twice, which speeds up the establishment of the data transmission path. When establishing the path, the distance between nodes is also considered, which improves the stability of route establishment and thus improves the packet reception rate of the destination node.

[0162] b. Throughput: The throughput in the above two scenarios is as follows Fig.11 and Fig.12As shown. The throughput of the CACN-OAODV routing protocol is higher than that of AODV in both scenarios. In the underwater-underwater transmission scenario, it is about 20bps higher than the traditional AODV, and in the underwater-air transmission scenario, it is about 12bps higher than the original AODV. In the first 100 seconds of the simulation, the throughput fluctuates greatly because the path has not been fully established. After 100 seconds, the throughput gradually stabilizes, but the subsequent fluctuations are due to the path being broken due to node movement, and the path needs to be reestablished, which causes the throughput to fluctuate for a certain period of time. In the later stages of the simulation, it can be clearly seen that CACN-OAODV performs better than traditional AODV.

[0163] c. Delay: as shown in Table 4;

[0164] Table 4 Average transmission delay between underwater and underwater, and between underwater and air

[0165] Average delay (s) Underwater - Underwater Underwater-Aerial AODV 2.64 1.83 CACN-OAODV 2.58 1.59

[0166] The delay in the above two scenarios is as follows Fig.13 and Fig.14 The average delay is shown in Table 4. In both scenarios, the delay of the CACN-OAODV routing protocol is lower than that of the AODV protocol. The underwater-underwater transmission scenario is about 0.06 seconds lower than the original AODV, and the underwater-air transmission scenario is about 0.24 seconds lower than the original AODV. Compared with the unimproved AODV routing protocol, the number of large delays is significantly reduced after the improvement. This is because the destination node replies to the RREP twice after receiving the routing request, so that the data transmission path is established faster and the cache time of the data packet is reduced. At the same time, when requesting a route, the corresponding survival hop count is reduced according to the corresponding sending device, making it more likely that the link will pass through the underwater acoustic-radio-underwater acoustic link, speeding up the transmission speed and reducing the transmission delay.

[0167] After simulation analysis, the CACN-OAODV protocol has advantages over AODV in terms of packet delivery rate, throughput and latency. In the underwater to underwater node data transmission scenario, the CACN-OAODVV protocol packet delivery rate increased by about 15%, the average throughput increased by about 20bps, and the average latency decreased by about 0.06 seconds; in the underwater to air node data transmission scenario, the CACN-OAODV protocol packet delivery rate increased by about 9%, the average throughput increased by about 12bps, and the average latency decreased by about 0.24 seconds.

[0168] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principles of the present invention should be covered by the protection scope of the present invention.

Claims

1. An improved AODV routing method for marine cross-medium acoustic-electric cooperative network, characterized in that: The method includes route finding, route replying and route maintenance; When establishing the route, the link stability factor of radio and underwater acoustic transmission is introduced; after the route is established, each node determines whether the route is invalid by whether it can receive the HELLO packets broadcast regularly by its neighbors; The surface cross-medium node specifies the device for data transmission according to the type of the destination node; when the hydroacoustic device of the cross-medium node receives the routing request information, if the destination node is an aerial node, it is directly forwarded through the buoy's radio equipment; When the destination node is an underwater node, if the surface cross-medium node receives a routing request from the underwater node, it forwards the routing request using a radio device; If the surface cross-medium node radio equipment receives a routing request, the routing request is forwarded simultaneously through the hydroacoustic equipment and the radio equipment; After the node receives the routing response and establishes the route, it sets a timer to send HELLO packets for route maintenance. Nodes that have not established routes do not send HELLO packets. After receiving the routing request, the underwater destination node sends two routing responses to the source node in succession.

2. The improved AODV routing method for ocean cross-medium acoustic-electric cooperative network according to claim 1 is characterized in that: Route search, including: (1) When the source node has data to send to the destination node, the source node checks whether there is a route to the destination node. If so, the data is sent directly; if not, the source node sends a route request RREQ to start establishing the route; (2) When a node receives a routing request, it determines whether the survival hop count TTL of the routing request is a finite value. If not, it is discarded. If it is a finite value, it calculates the distance between the node and the previous hop node and the single-hop link stability factor RQ value. It adds the RQ value to the total support value ALLRQ in RREQ and divides it by the number of hops to obtain the average link quality AVGRQ. (3) The node determines whether it has received an RREQ with the same ID. If not, it directly stores or updates the path to the source node in the routing table. If it has received an RREQ with the same ID, it determines whether AVGRQ is greater than the value in the existing routing table. If so, it stores or updates the path to the source node in the routing table. If AVGRQ is not greater than the value in the existing routing table, it discards the routing request. (4) Determine whether it is the destination node or whether there is a path to the destination node. If so, send two routing response RREPs to the source node. When the source node receives the RREPs, the route establishment is complete. (5) If the node is not the destination node or there is a path to the destination node, determine whether the node is a buoy node; (6) If the node is a buoy node, it is determined whether the node receives an RREQ from an underwater acoustic device. If so, the routing request survival hop count TTL is subtracted by b, and the node continues to broadcast the RREQ using radio, and the next-hop node continues to execute step (2); if the node does not receive the RREQ from the underwater acoustic device, it is determined whether the destination node is an underwater node. If not, the node routing request survival hop count TTL is subtracted by b, and the RREQ is broadcast using radio, and the next-hop node continues to execute step (2); if the destination node is an underwater node, the node routing request survival hop count TTL is subtracted by b, and the RREQ is broadcast using radio. At the same time, the node request survival hop count TTL is subtracted by a, and the RREQ is broadcast using underwater acoustic, and the next-hop node continues to execute step (2); a is the one-hop weight coefficient of the underwater acoustic sensor node, and b is the one-hop weight coefficient of the radio node; (7) If the node is not a buoy node, it is determined whether the node is an underwater acoustic node. If so, the node request survival hop count TTL is subtracted by a, and the RREQ is broadcast using underwater acoustic, and the next-hop node continues to execute step (2); if the node is not an underwater acoustic node, the node routing request survival hop count TTL is subtracted by b, and the RREQ is broadcast using radio, and the next-hop node continues to execute step (2).

3. The improved AODV routing method for ocean cross-medium acoustic-electric cooperative network according to claim 2 is characterized in that: In step (1), the source node checks whether there is a route to the destination node, including: the routing request packet contains the survival hop count TTL. If the routing reply is not received for a long time, the survival hop count is increased and the routing request is sent continuously.

4. The improved AODV routing method for ocean cross-medium acoustic-electric cooperative network according to claim 2 is characterized in that: In step (2), the number of hops passed by the routing request is the weighted hop count Hop, and the expression is: Hop=a*Hop w +b*Hopw r Where a is the one-hop weight coefficient of the underwater acoustic sensor node, Hopu w is the number of hops of the hydroacoustic node through which the routing request passes, b is the one-hop weight coefficient of the radio node, and Hop w r is the number of buoy nodes or aerial nodes that the routing request passes through; Introduce the underwater acoustic transmission link stability factor RQ, and the calculation formula is as follows: In the formula, d is the distance between two underwater nodes, R represents the maximum underwater acoustic communication radius, w is the distance threshold coefficient, 0 < w < 1, and w×R represents the communication critical distance; The total support value ALLRQ is the sum of the RQs of radio and underwater acoustic communications on the path, and the expression is: In the formula, ALLRQ is the total support value, i represents the i-th node of the path, n represents the total number of nodes in the path, and RQ i represents the transmission link stability factor of the i-th node; The average link quality AVGRQ is the ratio of the sum of all link stability factors in the path to the number of hops, and the calculation formula is as follows: In the formula, n represents the total number of nodes in the path. The larger the AVGRQ value, the higher the link quality.

5. The improved AODV routing method for ocean cross-medium acoustic-electric cooperative network according to claim 2 is characterized in that: In step (3), the node determines whether it has received an RREQ with the same ID. The determination process is as follows: 1) When the node receives an RREQ, it is determined whether there is the same RREQ ID number, source node, and destination node in the RREQ record table. If so, the RREQ is discarded; 2) When the node receives an RREQ, if it receives the RREQ for the first time, the RREQ ID number, source node address, and destination node address are stored in the RREQ record table.

6. The improved AODV routing method for ocean cross-medium acoustic-electric cooperative network according to claim 2, characterized in that: In step (4), the node determines whether it is the destination node or there is a path to the destination node. The determination method is: whether the destination node IP address in the RREQ is the same as the local node IP address; The method for determining whether there is a path to the destination node is: determining whether the routing table stores a path to the destination node; In step (6), judging whether the information received from the hydroacoustic / radio interface is received by the hydroacoustic device or the radio device, and judging the node type according to the IP address of the destination node; In step (7), the node type is determined based on the node's IP address.

7. The improved AODV routing method for ocean cross-medium acoustic and electrical cooperative network according to claim 1 is characterized in that: Routing reply, including: (1) If a network node receives a RREP packet, it determines whether there is a RREP packet with the same ID and the same destination node in the message list. The determination process of the RREP packet with the same ID is as follows: first determine whether there is the same RREQ ID number and the source node and destination node of the RREQ in the RREQ record table. If so, discard the RREQ; if it is the first time to receive the RREQ, store the RREQ ID number and the source node and destination node address of the RREQ in the RREQ record table; if not, update the destination node routing table and start periodically broadcasting HELLO packets; if there is a RREP packet with the same ID and the same destination node in the message list, read the AVGRQ in the RREP to determine whether it is greater than the AVGRQ value in the existing routing table. If not, discard the RREP packet; if it is greater than the AVGRQ value in the existing routing table, update the destination node routing table and start periodically broadcasting HELLO packets; (2) Determine whether the node is a source node, and then determine whether the source node address in the RREP data packet is the local address. If they are the same, it is the source node; if so, the route establishment is completed; if not, unicast forward the RREP to the source node, and the next hop node continues to execute step (1).

8. The improved AODV routing method for ocean cross-medium acoustic-electric cooperative network according to claim 1, characterized in that: After the route is established, each node on the path broadcasts Hello packets regularly and starts to perform route maintenance steps, which include: (1) The node determines whether it has received a Hello packet from a neighbor node regularly; (2) If a Hello packet is received regularly from a neighbor node, no processing is done on the routing table; (3) If the Hello packet from a neighbor node is not received regularly, determine whether there is a route with the next hop being the neighbor node in the routing table; if not, execute step (2); if so, delete the route and send a routing error RERR packet to the source node of the route; (4) After receiving the RERR packet, the node determines whether there is an erroneous route in its own routing table. If not, no processing is done on the routing table. If so, the route is deleted. (5) The node determines whether there is still a route in its routing table. If not, it stops broadcasting Hello packets periodically. If yes, it determines whether the node is a source node. If not, it unicasts the RERR to the source node. If not, it ends the routing maintenance process.

9. The improved AODV routing method for ocean cross-medium acoustic-electric cooperative network according to claim 8, characterized in that: In step (1), the process of a node determining whether it has received a Hello packet from a neighbor node regularly is as follows: the node is set to broadcast a Hello packet every T seconds, and determines whether it has received a Hello packet from a neighbor node within every 2T seconds; In step (3), based on the IP address of the neighboring node, the next hop IP address of each path in the routing table is retrieved to see whether it is the same as the IP address of the neighboring node; In step (4), the destination node and next hop information of the path in the routing table are retrieved to see whether they are consistent with the information in the RERR packet.

10. The improved AODV routing method for ocean cross-medium acoustic and electrical cooperative network according to claim 8, characterized in that: In step (5), determine whether there are still routes in its own routing table, then determine whether the number of paths currently existing in the routing table is 0; determine whether the node is a source node, then determine whether it has the previous hop address of the path, if so, it is not a source node; if not, it is a source node.

Images