Energy-saving and high-efficiency routing method for underwater sensor network

Abstract

Provided in the present invention is an energy-balanced and high-efficiency routing method. The method uses a power control mechanism to reduce the energy consumption. The method includes a routing establishment stage and a data transmission stage. In the routing establishment stage, an aggregation node broadcasts a beacon packet at the maximum transmitting power to establish an initial path, and a receiving node updates a routing table according to beacon information and forwards the beacon packet. In a data forwarding stage, the present invention provides a new forwarding factor, and energy efficiency and an energy balance are comprehensively taken into consideration to select as an optimal next hop a node having a high energy efficiency and relatively sufficient energy, thereby prolonging the life cycle of a network. In addition, the present invention further provides a data protection and network reconstruction mechanism to deal with problems such as network topology changes and data forwarding failures, which are caused by node movements. Compared with other typical routing methods, the present invention exhibits a superior performance in terms of reducing the network energy consumption and prolonging the life cycle of a network.

Description

An energy-saving and efficient routing method for underwater sensor networks Technical Field

[0001] The present invention relates to the technical field of sensor networks, and in particular to an energy-saving and efficient routing method for an underwater sensor network. Background Art

[0002] Routing in underwater wireless sensor networks is crucial for realizing underwater applications. It enables information and data transmission between underwater nodes. However, underwater wireless sensor networks differ significantly from their terrestrial counterparts, presenting additional challenges. Firstly, underwater networks place higher demands on energy balance between nodes, as underwater nodes cannot replenish their own energy and have limited energy storage. If a node is overused, it will prematurely deplete its energy and become ineffective. The premature demise of these nodes can disrupt the network and affect its normal operation. Therefore, routing design should ensure that the energy consumption of all nodes decreases synchronously. Secondly, underwater network structures are dynamic. Due to the influence of water flow, nodes move within a certain range, causing the network structure to change dynamically. This requires routing designs to adapt to changes in network topology. These characteristics place higher demands on routing, necessitating the design of routing methods that are more suitable for underwater networks.

[0003] Summary of the Invention

[0004] Purpose of the invention: To reduce the energy consumption of underwater networks, extend the network life cycle, and achieve efficient forwarding of data packets at each hop.

[0005] Technical Solution: To achieve the above objectives, the present invention provides an energy-efficient and efficient routing method for a depth-based underwater sensor network. In the present invention, all data and control packets contain information such as the transmission power, remaining energy, and depth of the sending node. During the routing establishment phase, the sink node broadcasts a beacon packet at maximum transmission power. After receiving the beacon packet sent by the previous hop node, the relay node first calculates the power level required for the previous hop node by measuring the received signal strength. Then, based on the information in the packet and the power level, it calculates the forwarding factor for the node and stores it in the routing table. Finally, the relay node updates the information in the beacon packet and broadcasts it at maximum power. To avoid nodes repeatedly sending beacon packets, each node only sends a beacon packet once within a period of time. During the data transmission phase, the node sets the node with the largest forwarding factor in the routing table as the optimal next hop node and forwards data to it. To address the node mobility problem and the low channel utilization and high energy consumption caused by the frequent transmission of beacon packets, we propose an implicit routing update mechanism, whereby the node monitors all data and control packets within its communication range and updates and maintains the route based on the signal strength and information in the packet. To address data forwarding failures and routing failures caused by node mobility, we propose an integrated local-global strategy. This strategy incorporates two parallel mechanisms: local recovery and global recovery. When packet forwarding fails, the local recovery mechanism is triggered, and the node sends a probe packet to rebuild the routing table and then retransmits the packet based on the routing table. When the sink node detects that the packet reception rate falls below a threshold, the global recovery mechanism is triggered, and the sink node sends a beacon packet to reestablish routing for the entire network. The specific steps of our approach are as follows:

[0006] Step 1: First, the surface aggregation node broadcasts a beacon packet at maximum transmission power to establish a route. This beacon packet is broadcast at maximum transmission power to establish the initial path. Data transmission along this path achieves the optimal balance between energy efficiency and energy balance, leveraging the forwarding factor. The receiving node determines whether the node sending the beacon meets the next-hop criteria based on depth information. If not, the packet is discarded. Otherwise, the optimal transmission power from the node to the sending node is estimated using the transmission power and received signal strength recorded in the packet. The forwarding factor is then calculated and recorded in the routing table based on the node's remaining energy information. The neighboring node with the highest forwarding factor is then designated as the optimal next-hop. The node then generates and broadcasts a beacon packet. To prevent duplicate transmissions, a node only sends a beacon packet once per period.

[0007] Step 2: After the route is established, the network enters the data forwarding phase. When the relay node receives a data packet, it first executes the implicit routing update mechanism, updates the routing table according to the information in the packet, and then forwards the data packet to the neighbor node with the largest forwarding factor.

[0008] Step 3: When the sink node receives a data packet, it indicates that the data forwarding is successful. The sink node filters duplicate packets and counts the packet rate. If the packet rate is lower than the threshold, the overall recovery mechanism is triggered and the sink node rebuilds the network route.

[0009] When packet forwarding fails, the following steps are performed:

[0010] Step 4: After a node forwards data, if it neither monitors the data packet forwarded by the next-hop node nor receives the ACK packet from the next-hop node within T time, it is considered a forwarding failure and the node needs to execute a local recovery mechanism.

[0011] Step 5: When the local recovery mechanism cannot reconstruct the route, the node is determined to be a hole node. The node broadcasts a hole notification packet to notify the previous hop node to remove itself from the neighbor table.

[0012] Furthermore, the forwarding factor involved in step 1 is calculated as follows: assuming the current node is A and the neighboring node is B, the forwarding factor between node A and node B is calculated as follows:

[0013] When node A receives a packet (such as a beacon packet) sent by node B, let the received signal strength of the packet be Rss, then Rss=10log P0 (1.1)

[0014] Where P0 is the signal power received by node A. Let the power of node B sending beacon packet be P t , then the path loss between node A and node B is L AB It can be expressed as

[0015] Then the optimal transmission power P from A to B is optAB P optAB =L AB P th (1.3)

[0016] Among them, P th Indicates the signal reception threshold in watts, the power level P for communication between node A and node B ABL By P optAB Decision, that is, P ABL ←P optAB (1.4)

[0017] From the above formula, we can get that when A sends a data packet to B, the energy consumed is E AB For E AB =P opt t send (1.5)

[0018] where tsend It is worth noting that node B also consumes energy when receiving data. However, since the node receiving power is much smaller than the sending power, we ignore this energy consumption when calculating the forwarding factor.

[0019] Let the normalized residual energy of node A and the normalized energy efficiency between node A and node B be E re and E ηAB , then the forwarding factor from A to B is f AB =p B (αE ηAB +βE re ) E re ,E ηAB ∈(0,1] (1.6)

[0020] Among them, p B is the packet forwarding success rate of node B, with an initial value of 1; α and β are system parameters, satisfying α+β=1. In theory, the larger α is, the better the routing effect in terms of energy saving; conversely, the smaller α is, the better the routing effect in terms of energy balance. Energy efficiency E ηAB It can be calculated by the following formula:

[0021] where △d AB is the depth difference between node A and node B.

[0022] The forwarding factor is used to select relay nodes, which plays an important role in improving energy-efficient data transmission. However, if the distance between the source and the relay is greater, the transmission energy consumption increases. On the other hand, if the distance is smaller, the number of hops increases, which also leads to higher end-to-end delay. Therefore, in order to limit the number of packet hops and balance network energy consumption with end-to-end delay, we set the depth difference threshold to d th ,Only when the depth difference between a node and its neighbor node is greater than the depth difference threshold, the node will calculate the forwarding factor between it and the neighbor node and store it in the neighbor table. th Calculate d by the following formula th =γR (1.8)

[0023] Among them, R is the maximum communication radius, and γ is the threshold coefficient with a value of 0 to 1.

[0024] Furthermore, the overall recovery mechanism and local recovery mechanism mentioned in step 3 and step 4 are two parallel mechanisms in the integrated strategy of local-overall combination. The specific operation is as follows: for local recovery, when the transmission fails, the node sends a probe packet at maximum power and sets a waiting time T. After receiving the probe reply packet, the node that meets the next hop conditions replies with the probe reply packet at maximum power. After receiving the packet, the node calculates the forwarding factor and updates the routing table. After T ends, the node selects the neighbor node with the largest forwarding factor in the routing table as the next hop node and forwards the data packet. For overall recovery, the specific operation is that all aggregation nodes share the received data packets, and record the total number of non-duplicate data packets received within T time, and compare this value with the total number of data packets sent by the source node within the same time. When the ratio is less than the set threshold, the overall recovery mechanism is triggered, that is, the aggregation node sends a beacon packet to rebuild the network route.

[0025] Beneficial Effects: The present invention proposes an energy-efficient and efficient routing method for underwater sensor networks. In terms of power control, the present invention estimates path loss based on received signal strength and then adjusts the transmit power based on the loss. In terms of next-hop selection, the forwarding factor takes into account information such as transmit power, depth difference, and residual energy, fully considering energy efficiency and energy balance, and then selects a node with high energy efficiency and relatively sufficient energy as the optimal next hop. Simulation results show that compared with existing typical routing, the present invention has a longer network lifespan and lower energy consumption. However, because the power control and data protection mechanisms of the present invention increase end-to-end latency, the present invention is suitable for systems that are insensitive to delay and have high network lifespan requirements, such as long-term applications such as underwater pollution monitoring and equipment monitoring (which do not require high real-time performance). BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG1 is a flow chart of a method for forwarding data packets in an energy-saving and efficient routing method for an underwater sensor network according to the present invention;

[0027] FIG2 is a schematic diagram of establishing a route according to the present invention;

[0028] FIG3 is a schematic diagram of data forwarding implemented in the present invention;

[0029] FIG4 is a schematic diagram of partial recovery according to the present invention;

[0030] FIG5 is a diagram comparing the energy consumption of the present invention and other routing methods; DETAILED DESCRIPTION

[0031] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0032] As shown in Figure 1, the present invention discloses an energy-saving and efficient routing method for an underwater sensor network. If a data packet comes from above, it indicates that the node may have monitored a data packet forwarded by the next-hop node. The node updates the routing table information, then searches for and removes the packet from the packet list. If the data packet comes from below, the node forwards or discards the packet based on the packet header information. If the current forwarding power is less than the previous hop forwarding power, it indicates that the previous hop node cannot monitor the data packet forwarded this time, and therefore needs to reply with an ACK packet to inform the previous hop that the data forwarding is successful. Conversely, if the current forwarding power is greater than or equal to the previous hop forwarding power, the previous hop node can monitor the data packet forwarded by this node and, based on this, determines that the data has been successfully forwarded, and therefore does not need to reply with an ACK packet.

[0033] Fig. 2 shows the process of implementing route establishment of the present invention. In the figure, the sink node (sink node) first broadcasts a beacon packet with maximum transmit power. The node (such as N2, N3 or N4) that receives the beacon packet calculates the power level required by the node to the sink node by measuring the received signal strength. Then, the forwarding factor of the node to the sink node is calculated based on the information in the packet and the power level, and stored in the routing table. Finally, the node can update the information in the beacon packet and broadcast it with maximum power. By analogy, until the source node receives the beacon packet. The node (such as N1 or N11) that does not receive the beacon packet does not participate in communication because it does not have a suitable next hop node.

[0034] Figure 3 illustrates the data forwarding process implemented in the present invention. A source node sends a data packet and sets the packet's next hop to node N5 according to the routing table. After receiving the packet, node N5 simply forwards it and stores the transmitted packet in a packet queue. It does not send an ACK packet to the source node. This is because the power level at which node N5 forwards the packet is greater than the power level at which the source node sends it. The source node can directly monitor the packet forwarded by N5, confirming that the packet has been successfully sent, and simultaneously updating the routing table information for node N5. When forwarding a packet, node N3 needs to send an ACK packet to node N5. However, because N3 uses a lower power level when forwarding the packet, N5 cannot monitor the packet forwarded by N3. Since sink nodes do not forward packets underwater, they also need to send an ACK packet. Node N4 in the figure receives the packet sent by N5, but because it determines that it is not the destination node, it discards the packet. Simultaneously, N4 receives the packet and ACK packet sent by N3 and updates the routing table based on the packet information and signal strength.

[0035] FIG4 shows the process of implementing local recovery in the present invention. Node N1 is at power level P n The data packet is forwarded to N2, but at this time N2 has left the power level P due to movement. nThe communication range is beyond the reach of N1, so the forwarding fails. Therefore, N1 triggers the local recovery mechanism and sends a probe packet at maximum power. Nodes N2, N3, and N4 all receive the probe packet. Among them, N4 has a depth greater than N1, so N4 will not send a probe reply packet to N1, but N4 will update its own routing table based on the information in the probe packet; N2 and N3 will both send a probe reply packet to N1, and N1 will update its routing table accordingly and resend the data packet.

[0036] Figure 5 shows a comparison of the network lifespan of the routing method proposed in this invention and other routing methods. Simulations were performed for different numbers of nodes and different node migration speeds. The results show that this method is superior to other methods in reducing network energy consumption and extending network lifespan.

[0037] The energy-saving and efficient routing method for underwater sensor networks of the present invention includes the following three parts:

[0038] a. Data Forwarding Algorithm: During the data forwarding phase, a node traverses its neighbor table, selects the neighbor with the highest forwarding factor as the optimal next-hop node, and forwards the data to that node. Because a node requires time to confirm the success of a data packet after sending it, each node maintains a queue Q of pending packets. When a node sends a data packet, it sets a timer T and stores the packet in Q. If, before T expires, it detects the next-hop node forwarding the data packet or receives an ACK packet from the next-hop node, the packet is successfully transmitted and the node removes the packet from Q. Otherwise, the packet fails to be transmitted and a local recovery mechanism is implemented.

[0039] b. Implicit routing update algorithm: Different from the traditional update mechanism that updates the routing table by sending control packets, the implicit routing update mechanism emphasizes completing the routing update process while communicating between nodes (such as sending data packets or other control packets).

[0040] c. Data protection and network reconstruction mechanism: Due to the mobility of nodes, packet forwarding may be interrupted. For such situations, we adopt an integrated local-global strategy to ensure network communication effectiveness.

[0041] The data forwarding algorithm uses the forwarding factor we designed to determine the best next hop. Assuming that node A is the data forwarding node and node B is the next hop node of node A, the forwarding factor of node B relative to node A is f AB The calculation method is as follows: AB =p B (αE ηAB +βE re ) E re ,E ηAB ∈(0,1]

[0042] Among them, pB is the packet forwarding success rate of node B, with an initial value of 1; α and β are system parameters, satisfying α+β=1. In theory, the larger α is, the better the routing effect in terms of energy saving; conversely, the smaller α is, the better the routing effect in terms of energy balance. re and E ηAB are the normalized residual energy of node A and the normalized energy efficiency between node A and node B, respectively.

[0043] The implicit routing update algorithm emphasizes completing routing updates simultaneously with inter-node communication (such as sending data or other control packets). When a data or control packet is detected, a node first measures the packet's signal strength and reads the information within it. It then traverses its neighbor list. If the node sending the packet is among the neighboring nodes, the node's information is updated. If not, the node's depth information determines whether it meets the criteria for becoming the next hop. If so, the sending node's information is added to the neighbor list. Otherwise, the routing table is not updated.

[0044] The data protection and network reconstruction mechanism described above incorporates a local-global integrated strategy we designed. It features two parallel mechanisms: local recovery and global recovery. When packet forwarding fails, the local recovery mechanism is triggered, and nodes send probe packets to rebuild their routing tables and then retransmit packets based on the routing table. When a sink node detects a drop in packet reception, the global recovery mechanism is triggered, and the sink node sends beacon packets to reestablish routing for the entire network.

[0045] The present invention provides an energy-balanced and efficient routing method. The present invention adopts a power control mechanism to reduce energy consumption. The present invention includes two stages: routing establishment and data transmission. In the routing establishment stage, the aggregation node broadcasts a beacon packet with the maximum transmission power to establish the initial path. The receiving node updates the routing table according to the beacon information and forwards the beacon packet. In the data forwarding stage, the present invention proposes a new forwarding factor, which comprehensively considers energy efficiency and energy balance, and selects a node with high energy efficiency and relatively sufficient energy as the optimal next hop, thereby extending the network life cycle. In addition, the present invention also proposes a data protection and network reconstruction mechanism to cope with problems such as network topology changes and data forwarding failures caused by node movement. Compared with other typical routing methods, the present invention shows superior performance in reducing network energy consumption and extending network life cycle.

[0046] Although the embodiments of the present invention have been described with reference to the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention. Such modifications and variations are all within the scope defined by the appended claims.

Claims

1. An energy-saving and efficient routing method for underwater sensor networks, characterized in that: The following steps are involved: Step 1: The surface aggregation node broadcasts a beacon packet with maximum transmission power to establish a route; Step 2: After the route is established, the network enters the data forwarding phase. When the relay node receives a data packet, it first executes the implicit routing update mechanism, updates the routing table according to the information in the packet, and then forwards the data packet to the neighbor node with the largest forwarding factor. Step 3: When the sink node receives a data packet, it indicates that the data forwarding is successful. The sink node filters duplicate packets and counts the packet rate. If the packet rate is lower than the threshold, the overall recovery mechanism is triggered and the sink node rebuilds the route.

2. The energy-saving and efficient routing method for underwater sensor networks according to claim 1, characterized in that: When packet forwarding fails, the next steps are: Step 4: After the node forwards data, if it neither monitors the data packet forwarded by the next-hop node nor receives the ACK packet replied by the next-hop node within T time, it is judged as forwarding failure, and the node needs to execute the local recovery mechanism; Step 5: When the local recovery mechanism cannot rebuild the route, the node is determined to be a hole node, and the node broadcasts a hole notification packet to notify the previous hop node to remove itself from the neighbor table.

3. The energy-saving and efficient routing method for underwater sensor networks according to claim 1 is characterized in that: The routing is established by broadcasting a beacon packet with maximum transmission power by the aggregation node. After the relay node receives the beacon packet sent by the previous hop node, it first calculates the power level required for the previous hop node by measuring the received signal strength, and then calculates the forwarding factor for the previous hop node based on the information in the packet and the power level, and stores it in the routing table. Finally, the relay node updates the information in the beacon packet and broadcasts it with maximum power.

4. The energy-saving and efficient routing method for underwater sensor networks according to claim 1 is characterized in that: The implicit routing update mechanism is that the node will monitor all data packets and control packets within its communication range, and complete the update and maintenance of the route according to the signal strength and the information in the packet.

5. The energy-saving and efficient routing method for underwater sensor networks according to claim 4 is characterized in that: The implicit routing update mechanism is specifically that when a data packet or control packet is monitored, the node first measures the signal strength of the packet and reads the information in the packet, and then traverses the neighbor list. If the node sending the packet is in the neighbor node, the node information is updated. If not in the neighbor list, it is determined based on the depth information whether the node meets the conditions for becoming the next hop. If so, the information of the sending node is added to the neighbor table, otherwise the routing table is not updated.

6. The energy-saving and efficient routing method for underwater sensor networks according to claim 1, characterized in that: The forwarding factor is specifically: assuming that node A is a data forwarding node and node B is the next hop node of node A, then the forwarding factor of node B relative to node A is f AB The calculation method is as follows: AB =p B (αE ηAB +βE re ) E re ,E ηAB ∈(0,1] Among them, p B is the packet forwarding success rate of node B, with an initial value of 1; α and β are energy efficiency weights and residual energy weights, respectively, satisfying α+β=1; E re and E ηAB are the normalized residual energy of node A and the normalized energy efficiency between node A and node B, respectively.

7. The energy-saving and efficient routing method for underwater sensor networks according to claim 1, characterized in that: When the depth difference between a node and its neighbor node is greater than the depth difference threshold, the node will calculate the forwarding factor between the node and the neighbor node and store it in the neighbor table; Depth difference threshold d th Calculated by the following formula: th =γR Among them, R is the maximum communication radius; γ is the threshold coefficient, and its value is (0,1].

8. The energy-saving and efficient routing method for underwater sensor networks according to claim 1, characterized in that: Since a node needs a certain amount of time to confirm whether the packet is sent successfully after sending a data packet, each node maintains a queue Q of packets to be confirmed. The node sets a timer T while sending a data packet and stores the sent packet in Q. If the node monitors the next-hop node forwarding the data packet or receives an ACK packet from the next-hop node before T expires, it means that the packet is sent successfully and the node deletes the packet from Q. Otherwise, the data packet fails to be sent and a local recovery mechanism needs to be executed.

9. The energy-saving and efficient routing method for underwater sensor networks according to claim 1, characterized in that: The local recovery mechanism is that when the transmission fails, the node sends a detection packet at maximum power and sets a waiting time T. After receiving the detection packet, the node that meets the next hop conditions replies with the detection reply packet at maximum power. After receiving the packet, the node calculates the forwarding factor and updates the routing table. After T ends, the node selects the neighbor node with the largest forwarding factor in the routing table as the next hop node and forwards the data packet.

10. The energy-saving and efficient routing method for underwater sensor networks according to claim 1, characterized in that: The overall recovery mechanism is that all aggregation nodes share the received data packets, and record the total number of non-duplicate data packets received within time T, and compare this value with the total number of data packets sent by the source node within the same time. When the ratio is less than the set threshold, the overall recovery mechanism is triggered, and the aggregation node sends a beacon packet to complete the routing reconstruction of the entire network.

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