Routing method applied to indoor fire communication

Abstract

The present invention discloses a routing method for indoor firefighting communications, which is specifically carried out in the following steps: Step 1: Model the wireless signal propagation model in the scenario and obtain relevant parameters; Step 2: Implement information interaction in the scenario through the neighbor discovery algorithm and estimate the link duration LET; Step 3: Improve the intra-region routing algorithm and construct an intra-region routing table based on LET; Step 4: Improve the routing discovery process and update the inter-region routing based on LET. Based on the original ZRP, the present invention combines the indoor propagation model and the node motion state to estimate the link duration, allowing the node to predict the link state, thereby maximizing the routing lifetime. Through simulation verification, the method of the present invention can reduce end-to-end delay, reduce packet loss rate and improve network throughput.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless Mesh networks, and in particular relates to a routing method applied to indoor firefighting communications. Background Art

[0002] In recent years, with the continuous expansion of urban construction, the number of high-rise and super-high-rise buildings in cities has continued to increase. Consequently, fire safety issues within these buildings have become increasingly prominent, and the frequency of fires has also increased. On the one hand, sensing environmental conditions within buildings, such as temperature, smoke, and combustible gases, can help prevent fires. On the other hand, fires often result in power outages and public network unavailability, making public networks unable to meet the needs of emergency communications for the public and firefighters within buildings. Firefighting incidents are characterized by uncertainty in both location and time, requiring firefighting communication networks to be fast and highly reliable. Firefighting incidents often result in damage to signal booster towers and switches within buildings, rendering the public network unavailable and requiring lengthy repairs, making them inadequate for firefighting communication networks. Existing firefighting-specific communication equipment, when deployed deep within buildings, faces the challenge of wireless signals failing to penetrate multiple layers of walls, making it difficult to achieve full on-site network coverage.

[0003] Wireless mesh networking is a multi-hop networking technology characterized by being decentralized, self-organizing, and enabling multi-hop routing. Indoor firefighting communication networks constructed using wireless mesh networks offer exceptional resilience and flexibility, ensuring reliable and unimpeded communication for firefighting and rescue teams during large-scale, complex rescue operations. Wireless mesh networks achieve multi-hop communication through wireless routing algorithms, and their performance is directly dependent on the algorithm employed. Numerous studies have been conducted on wireless routing algorithms, which are currently categorized into two main types: proactive and reactive. Proactive routing algorithms (such as OLSR) maintain a global routing table through network-wide information exchange. When sending data, they directly use the routes in this table. This enables these algorithms to achieve very low latency. However, the data packets sent to maintain the routing table incur significant routing overhead, consuming significant bandwidth resources. This overhead is particularly pronounced in scenarios with rapidly changing topologies. Reactive routing algorithms (such as AODV) are also called on-demand routing algorithms. Devices using on-demand routing algorithms only broadcast route request frames to query the target device when there is a need to send data, reducing routing overhead but also increasing latency. ZRP (Zone Routing Protocol) is a hybrid routing algorithm. Each ZRP node maintains an area with a radius of r. Within this area, a proactive routing algorithm is used to maintain a local routing table. Beyond this area, a reactive routing algorithm is used. ZRP combines the advantages of proactive and reactive routing algorithms while offering excellent scalability, making it commonly used in tactical networking.

[0004] However, the existing ZRP routing algorithm is not suitable for indoor firefighting communications. The reasons are as follows: (1) The mobility of nodes is not properly considered in the routing process. (2) The end-to-end delay is too long to be used in emergency situations. (3) The existing ZRP is mainly based on free space and does not consider the attenuation of wireless signals by obstacles. Therefore, in scenarios with many indoor obstacles (i.e., walls, damaged buildings, and furniture), routing reliability will be greatly reduced. Therefore, it is necessary to improve the ZRP protocol for indoor scenarios. Summary of the Invention

[0005] The purpose of the present invention is to provide a routing method for indoor fire communication, which solves the problem of ZRP performance degradation caused by attenuation of wireless signals by obstacles and node mobility in indoor scenarios.

[0006] The technical solution adopted by the present invention is:

[0007] The routing method applied to indoor fire communication is specifically carried out in the following steps:

[0008] Step 1: Model the wireless signal propagation model in the scenario and obtain relevant parameters; install a Mesh router in the scenario and obtain the propagation model parameters of the current scenario through the Mesh client device and the Mesh router;

[0009] Step 2: Use the neighbor discovery algorithm to implement information exchange between nodes in the current scenario and estimate the link duration LET;

[0010] Step 3: Improve the intra-area routing algorithm and build an intra-area routing table based on LET;

[0011] Step 4: Improve the intra-area routing algorithm and update the inter-area routing based on LET.

[0012] The present invention is also characterized in that:

[0013] In step 1, the indoor propagation model is built as follows:

[0014] The Seidel model is used to model the indoor propagation model. The received signal power P of the Seidel model is r , which is given by formula (1):

[0015] P r =P0-10nlog(d / d0)-N wall WAF-N door DAF-N win WiAF (1);

[0016] Among them, N wall 、N door 、N win where is the number of walls, doors, and windows that the wireless signal passes through, respectively. WAF, DAF, and WiAF are the attenuation factors of walls, doors, and windows, respectively. n is the path loss exponent. d is the distance between the transmitter and the receiver. P0 is the received signal power at d0 = 1 m.

[0017] In step 1, the Mesh router is a fire emergency light with integrated wireless communication capabilities. The fire emergency light is installed in indoor corridors and stairways. After the indoor propagation model is built, the parameters of the indoor propagation model will be stored in the Mesh router.

[0018] Step 2 is as follows:

[0019] Step 2.1: Each node periodically locates d Detect your own position and movement speed as the basis for position prediction;

[0020] Step 2.2: Each node, such as node A, periodically broadcasts neighbor detection frames. After receiving the neighbor detection frames, other nodes, such as node B, detect their current location and movement speed based on the indoor positioning system and motion sensor, and calculate the movement direction. The node then unicasts an ACK reply containing the node's movement speed, direction, and location coordinates. Assume that the node's positions at time t1 and t2 are (x1, y1) and (x2, y2), respectively. The node's movement direction θ can be estimated using formula (2).

[0021]

[0022] Step 2.3: After node A receives the ACK, it marks node B as a neighbor node, obtains the motion information and position information in the ACK, estimates the LET between the two neighbor nodes through position prediction, updates the link state table, and calculates the node n at t using the following formulas (3) and (4): p The position at the moment (x p ,y p );

[0023] x p =x+v(t p -t)cosθ (3);

[0024] y p =y+v(t p -t)sinθ (4);

[0025] From this we can estimate the future t p The distance d between two neighboring nodes at the moment p ;

[0026]

[0027] in, and Nodes A and B are at t p coordinates of the moment;

[0028] Finally, by combining formula (1) and the node's acceptance signal threshold P h , and estimate LET.

[0029] The estimation method is to calculate t in a node loop. p The received power P at the moment r , after each cycle t p Increase by 2s until P r Less than P h , then t p It's LET.

[0030] Step 3 is as follows:

[0031] Step 3.1: Node period T min Detect whether it is necessary to send an UPDATE data packet. If the UPDATE send flag is set or the sending interval is greater than T max , then the UPDATE sending condition is met, and the UPDATE data frame is broadcast to the nodes in the area. The UPDATE data frame contains the link status information of the node;

[0032] Step 3.2: The node receives the UPDATE data frame, parses the link state information in the data frame, and recalculates the routing table. The next hop selection in the routing table is based on the following:

[0033] Assume LET i represents the LET of link i, then the LET of the entire route should be the minimum value of all links on the route, that is, the following formula (6);

[0034] LET=min{LET1,LET2,…,LET n} (6);

[0035] Assuming that the number of routing hops is N, the new routing cost function RC is shown in the following formula (7):

[0036] RC=N*e -LET (7);

[0037] The node calculates the routing costs of all paths to the destination node, and the path with the smallest routing cost RC is selected as the route. Finally, the intra-area routing table is constructed.

[0038] Step 4 is as follows:

[0039] Step 4.1: When a node has a data transmission requirement, it first checks whether there is a route to the destination node in the local routing table. If not, it starts the inter-area route discovery process and sends a route request RREQ to all peripheral nodes in the area where the node is located.

[0040] Step 4.2: When a node receives a route request frame, if the destination node is itself, it replies with a route reply RREP carrying the LET. The RREP records the minimum LET on the path. If the destination node is not itself, it checks whether there is a route to the destination node in the local routing table. If so, it forwards the RREQ along the route to the destination node. If not, it broadcasts the RREQ to the peripheral nodes in the area where the node is located.

[0041] Step 4.3: The source node receives the routing RREP, reads the LET, and calculates and updates the optimal route according to formula (7).

[0042] The process also includes step 5, which specifically includes: for the link carrying data services, the node periodically calculates the LET. When the LET is less than the neighbor detection period, the node sends a routing error frame to the service flow source node to notify the source node to reselect the route.

[0043] The present invention's beneficial effects include the ability to apply this routing method to indoor firefighting communications, which uses location prediction combined with indoor propagation models to predict link status, improving the reliability of routing algorithms in indoor scenarios. By predicting link status, the link duration (LET) can be estimated. Then, by combining the number of route hops and LET to measure routing costs, a more reliable route can be selected. Furthermore, the present invention incorporates a monitoring mechanism for service-carrying links, enabling rapid route switching and further reducing packet loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 1 is a flow chart of a routing method for indoor firefighting communication according to the present invention;

[0045] Figure 2 Schematic diagram of a Mesh device module in a routing method for indoor fire communication according to the present invention;

[0046] Figure 3 This is a curve diagram showing the change of packet delivery rate with moving speed in the routing method of the present invention applied to indoor fire communication;

[0047] Figure 4 Schematic diagram of a curve showing a change in throughput versus moving speed in a routing method for indoor firefighting communication according to the present invention;

[0048] Figure 5 This is a schematic diagram of a curve showing how end-to-end delay varies with moving speed in a routing method for indoor firefighting communications according to the present invention. DETAILED DESCRIPTION

[0049] The routing method applied to indoor firefighting communication of the present invention will be described in detail below with reference to the accompanying drawings and specific implementation methods.

[0050] like Figure 1 As shown in FIG, the present invention is applied to a routing method for indoor fire communication. By combining the node motion state with the indoor propagation model, a ZRP routing method based on link state prediction is proposed. The method is mainly divided into the following parts:

[0051] 1. Obtain the information required by the routing algorithm;

[0052] The routing method applied to indoor fire communication in the present invention runs on specific equipment. Before use, it is necessary to model the wireless signal propagation model in the scenario and obtain relevant parameters. The Mesh device integrates motion state sensors and indoor positioning systems, and can detect its own motion state and location information in real time.

[0053] Modeling of indoor propagation models;

[0054] In order to accurately predict indoor positions, a deterministic model is needed to model the indoor propagation model. The present invention uses the Seidel model to model the indoor propagation model. The signal power of the Seidel model is given by formula (1).

[0055] P r =P0-10nlog(d / d0)-N wall WAF-N door DAF-N win WiAF (1);

[0056] Among them, N wall 、N door 、N win WAF, DAF, and WiAF are the attenuation factors of walls, doors, and windows, respectively, that wireless signals pass through. n is the path loss exponent. These parameters can be obtained by looking up tables or performing on-site measurements.

[0057] Mesh router installation;

[0058] The mesh router of this invention is a fire emergency light with integrated wireless communication capabilities. It is installed in indoor corridors and stairways, among other locations. Once the indoor propagation model is built, the parameters are stored in the mesh router. When a fire incident occurs, firefighters' portable mesh client devices can access the propagation model parameters through the mesh router, providing support for the proposed routing algorithm.

[0059] 2. Neighbor discovery algorithm (using the neighbor discovery algorithm to achieve scene information interaction);

[0060] Each node is periodically (t d ) detects its own position and movement speed as the basis for position prediction.

[0061] Each node (assuming it's A) periodically broadcasts neighbor detection frames. After receiving these frames, other nodes (assuming it's B) detect their current locations and calculate their speed and direction. The node then unicasts an ACK reply containing its motion and location information. Because people move slowly in indoor scenarios and the detection cycle is short, they can be considered to be moving at a constant speed. Assuming the node's positions at times t1 and t2 are (x1, y1) and (x2, y2), respectively, the node's motion direction θ can be estimated using formula (2).

[0062]

[0063] After receiving the ACK, node A marks node B as a neighbor node, obtains the motion information and location information in the ACK, estimates the link duration (Link Expiration Time, LET) from node A to node B through location prediction, and updates the link state table. The following formulas (3) and (4) can be used to calculate the node n at t p The position at the moment (x p ,y p ).

[0064] x p =x+v(t p -t)cosθ (3);

[0065] y p =y+v(t p -t)sinθ (4);

[0066] From this we can estimate the future t p The distance d between two neighboring nodes at the moment p .

[0067]

[0068] in, and are the coordinates of nodes A and B at time tp respectively.

[0069] Combined with formula (1) and the node's acceptance signal threshold P h , the link duration LET is estimated. The estimation method is that the node loop calculates t p The received power Pr at the moment, after each cycle t p Increase by 2s until P r Less than P h Then t p It's LET.

[0070] 3. Implement the improved intra-region routing algorithm;

[0071] Node periodicity (T min ) detects whether an UPDATE packet needs to be sent. If the UPDATE send flag is set or the send interval is greater than T max , then the UPDATE sending condition is met and the UPDATE data frame is broadcast to the nodes within the area (radius r hops). The UPDATE data frame contains the link status information of the node.

[0072] When a node receives an UPDATE data frame, it parses the link state information in the frame and recalculates the routing table. The next hop in the routing table is selected based on the following:

[0073] Assume LET i represents the link duration of link i, then the link duration LET of the entire route should be the minimum value of all links on the route, that is:

[0074] LET=min{LET1,LET2,…,LET n} (6);

[0075] Assuming that the number of routing hops is N, the new routing cost function RC is shown in formula (7), RC = N*e -LET (7);

[0076] The node calculates the routing costs of all paths to the destination node, and the one with the smallest routing cost RC is selected as the route, and then the intra-area routing table is constructed;

[0077] 4. Implement the improved inter-area routing algorithm;

[0078] When a node has a data transmission requirement, it first checks whether there is a route to the destination node in the local routing table. If not, it starts the inter-area route discovery process and sends a route request RREQ to all peripheral nodes in the area where the node is located.

[0079] When a node receives a route request frame, if the destination node is itself, it replies with a route reply (RREP) containing the LET. The RREP records the minimum LET along the path. If the destination node is not itself, the node checks its local routing table for a route to the destination node. If so, it forwards the RREQ along the route to the destination node. If not, it broadcasts the RREQ to all nodes in the node's area.

[0080] The source node receives the routing RREP, reads the LET, and updates and selects the best route according to formula (7).

[0081] 5. Link interruption monitoring;

[0082] For links carrying data services, nodes periodically calculate the LET. When the LET is less than the neighbor detection period, the link is unreliable. To reduce packet loss caused by link interruptions, the node sends a routing error frame to the source node of the service flow, instructing the source node to reselect the route.

[0083] There are many indoor propagation models. To verify the feasibility of the algorithm, the present invention uses the Seidel model in simulation. In addition, there are the Motley-Keenan Model, the Adjusted Motley-Keenan Model, and the more complex Han's model. A more accurate model can be selected during implementation.

[0084] There are many indoor position prediction algorithms. Taking into account the slow indoor movement speed, the present invention uses kinematic method prediction. In more complex scenarios, Kalman filter prediction, time series prediction and other methods can also be used.

[0085] Traditional routing algorithms and link state prediction methods are mainly based on free space and are not suitable for indoor environments. The routing method applied to indoor fire communication in this invention uses position prediction and combines it with indoor propagation model to predict link state, thereby improving the reliability of routing algorithms in indoor scenarios.

[0086] The traditional method of measuring routing cost based on routing hop count may not necessarily select the best route. The present invention predicts the link status and estimates the link duration, and then combines routing hop count and LET to measure routing cost, thereby selecting a more reliable route.

[0087] The present invention monitors the link carrying the service to achieve fast route switching and further reduce the packet loss rate.

[0088] The technical effects of the present invention are further described below in conjunction with simulation experiments:

[0089] The present invention is aimed at indoor fire protection scenarios, so the Seidel model is first implemented on ns2, and the Seidel model is used to simulate the proposed algorithm. During the experiment, 25 nodes were placed in a 200m*200m scene, of which 9 nodes were placed statically as Mesh routers, and the remaining nodes were randomly distributed in the scene, moving randomly in the scene at a rate v, and then 6 data streams were randomly selected and sent at a rate of 1Mbps. In order to verify the effectiveness of the proposed algorithm, the algorithm was simulated at rates v = 1m / s, 2m / s, 3m / s, 4m / s, and 5m / s, and the network packet delivery rate, throughput and end-to-end experimental data were obtained. The routing method proposed in the present invention is named LP-ZRP, and its performance is compared with the original ZRP routing algorithm.

[0090] As an embodiment, the specific parameters set in the experimental simulation of the present invention are as follows: simulation scene: 200m×200m; node movement speed v: 1m / s-5m / s; data stream transmission rate: 1Mbps; wireless transmission range: 70m; wireless propagation model: Seidel'model; data packet type: cbr; data packet size: 512Byte; simulation duration: 90s.

[0091] like Figure 3 As shown, the horizontal axis represents the moving speed, and the vertical axis represents the data packet delivery rate. Figure 3 It can be seen that as the moving speed increases, the packet delivery rate of the ZRP algorithm gradually decreases. Although the packet delivery rate of the LP-ZRP routing algorithm proposed in the present invention also decreases with increasing speed, the decreasing trend is more gradual than that of the ZRP algorithm. This means that in scenarios with a high topology change rate, the routing method proposed in the present invention can also maintain a low packet loss rate, ensuring the reliability of communication.

[0092] like Figure 4 As shown in the figure, the horizontal axis represents the mobile speed and the vertical axis represents the network packet throughput. As can be seen from the figure, the throughput performance of the proposed LP-ZRP routing algorithm is better than that of the ZRP algorithm, which means that the LP-ZRP routing algorithm can provide higher network capacity and carry more services.

[0093] Figure 5 This is a graph showing how network end-to-end delay changes with mobile speed. Figure 5 It can be seen that the delay of the LP-ZRP algorithm is lower than that of the ZRP algorithm, so it can better ensure the real-time performance of communication.

[0094] This routing method, applied to indoor firefighting communications, predicts link status and estimates the LET. It then combines the number of route hops and LET to measure routing cost, selecting routes with the largest LET. Simulations have shown that this routing method improves packet delivery rate and throughput while reducing end-to-end latency compared to the original ZRP routing protocol.

Claims

1. A routing method for indoor firefighting communication, characterized in that: Follow these steps: Step 1: Model the wireless signal propagation model in the scenario and obtain relevant parameters; install a Mesh router in the scenario and obtain the propagation model parameters of the current scenario through the Mesh client device and the Mesh router; In step 1, the indoor propagation model is built as follows: The Seidel model is used to model the indoor propagation model. The received signal power P of the Seidel model is r , which is given by formula (1): （1）； in, 、 、 are the number of walls, doors, and windows that the wireless signal passes through, 、 、 are the attenuation factors of walls, doors, and windows, respectively. is the path loss exponent, is the distance between the transmitter and the receiver, for The received signal power at Step 2: Use the neighbor discovery algorithm to implement information exchange between nodes in the current scenario and estimate the link duration LET; specifically: Step 2.1: Each node periodically locates d Detect your own position and movement speed as the basis for position prediction; Step 2.2: Each node, node A, periodically broadcasts neighbor detection frames; after receiving the neighbor detection frames, other nodes B detect the current position and moving speed based on the indoor positioning system and motion sensor, and calculate the moving direction. Then the node unicasts an ACK containing the node's moving speed, direction and position coordinates; assuming that the positions of the nodes at time t1 and t2 are and ; Node movement direction It can be estimated by formula (2); （2）； Step 2.3: After node A receives the ACK, it marks node B as a neighbor node, obtains the motion information and position information in the ACK, estimates the LET between the two neighbor nodes through position prediction, updates the link state table, and calculates the node n at t using the following formulas (3) and (4): p Position at the moment ; （3）； （4）； From this we can estimate the future t p The distance d between two neighboring nodes at the moment p ; （5）； in, and Nodes A and B are at t p coordinates of the moment; Finally, by combining formula (1) and the node's acceptance signal threshold P h , estimate LET; The estimation method is to calculate t in a node loop. p The received power P at the moment r , after each cycle t p Increase by 2s until P r Less than P h , then t p It is LET; Step 3: Improve the intra-area routing algorithm and build an intra-area routing table based on LET; specifically: Step 3.1: Node period T min Detect whether it is necessary to send an UPDATE data packet. If the UPDATE send flag is set or the sending interval is greater than T max , then the UPDATE sending condition is met, and the UPDATE data frame is broadcast to the nodes in the area. The UPDATE data frame contains the link status information of the node; Step 3.2: The node receives the UPDATE data frame, parses the link state information in the data frame, and recalculates the routing table. The next hop selection in the routing table is based on the following: Assume LET i represents the LET of link i, then the LET of the entire route should be the minimum value of all links on the route, that is, the following formula (6); （6）； Assuming that the number of routing hops is N, the new routing cost function RC is shown in the following formula (7): （7）； The node calculates the routing costs of all paths to the destination node, and the path with the smallest routing cost RC is selected as the route, and finally the intra-area routing table is constructed. Step 4: Improve the intra-area routing algorithm and update the inter-area routing based on LET; specifically: Step 4.1: When a node has a data transmission requirement, it first checks whether there is a route to the destination node in the local routing table. If not, it starts the inter-area route discovery process and sends a route request RREQ to all peripheral nodes in the area where the node is located. Step 4.2: When a node receives a route request frame, if the destination node is itself, it replies with a route reply RREP carrying the LET. The RREP records the minimum LET on the path. If the destination node is not itself, it checks whether there is a route to the destination node in the local routing table. If so, it forwards the RREQ along the route to the destination node. If not, it broadcasts the RREQ to the peripheral nodes in the area where the node is located. Step 4.3: The source node receives the routing RREP, reads the LET, and calculates and updates the optimal route according to formula (7).

2. The routing method for indoor firefighting communication according to claim 1, characterized in that: In step 1, the Mesh router is a fire emergency light with integrated wireless communication capabilities. The fire emergency light is installed in indoor corridors and stairways. After the indoor propagation model is built, the parameters of the indoor propagation model will be stored in the Mesh router.

3. The routing method for indoor firefighting communication according to claim 1, characterized in that: The process also includes step 5, which specifically includes: for the link carrying data services, the node periodically calculates the LET. When the LET is less than the neighbor detection period, the node sends a routing error frame to the service flow source node to notify the source node to reselect the route.

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