Tunnel emergency lighting ad hoc network frequency hopping and opportunistic routing method

Abstract

The application discloses a tunnel emergency lighting ad hoc network frequency hopping and opportunity routing method, which is applied to an ad hoc network containing fixed nodes, target nodes and mobile relay nodes. Each fixed node periodically collects a channel quality index and compares the channel quality index with a preset disconnection threshold value, determines a multi-hop link connection state, and calculates an available probability based on a mobile relay node rule. When a data packet to be sent is acquired, a communication mode is selected based on the above parameters: in a good channel, a multi-hop forwarding is directly performed; in an interference interval where a link is connected but a channel quality is lower than a preset quality threshold value and is not lower than the preset disconnection threshold value, if the available probability is low, frequency hopping synchronous switching of a standby channel is triggered; if the link is disconnected or is in the interference interval and the available probability is not lower than a preset probability threshold value, a relay mode is triggered, the data packet to be sent is buffered, a buffering time length and a forwarding priority are set, and the buffered data packet is handed over to the mobile relay node for relay and breakthrough, so that the self-rescue ability of communication under extreme disasters is remarkably improved.

Description

Technical Field

[0001] This application relates to the field of communications, and in particular to frequency hopping and opportunistic routing methods for self-organizing tunnel emergency lighting networks. Background Technology

[0002] With the acceleration of urbanization, the construction scale of underground spaces and tunnels (such as subway tunnels, highway tunnels, and urban underground utility tunnels) is expanding daily. Due to the narrow and enclosed environment of underground spaces, conventional public communication networks cannot provide comprehensive coverage. Therefore, the industry typically utilizes intelligent emergency lighting fixtures evenly distributed along the tunnel walls as communication nodes to construct wireless self-organizing networks (Mesh networks). This network is not only used for daily lighting control but also bears the crucial responsibility of collecting and transmitting critical data such as environmental parameters (e.g., temperature, humidity, and harmful gas concentrations), fire alarms, and personnel location during emergencies.

[0003] However, existing wireless ad hoc networks in underground spaces still face the following technical bottlenecks in actual deployment and under extreme conditions.

[0004] On the one hand, strong interference and multipath fading in narrow spaces make communication extremely vulnerable. Tunnel environments suffer from severe electromagnetic wave reflection and multipath effects. Simultaneously, the start-up and shutdown of large electromechanical equipment (such as fans and pumps) or the high-speed passage of trains can generate sudden, strong electromagnetic interference, causing a sharp deterioration in the quality of previously unobstructed wireless channels. Most existing ad hoc networks employ static channel configuration or simple timeout retransmission mechanisms, which often lead to widespread network congestion and packet loss when encountering persistent, strong local interference. They lack an adaptive frequency hopping mechanism that can proactively sense channel quality and guide local nodes to synchronously escape the interfering frequency band.

[0005] On the other hand, tunnel ad hoc networks often exhibit linear or chain-like topologies. In the event of extreme disasters such as fires, flooding, or partial collapses, some fixed communication nodes are highly susceptible to physical damage, directly severing multi-hop links and dividing the network into multiple "information islands" unable to communicate with the tunnel entrance control center. Traditional wireless routing protocols (such as AODV and OLSR) heavily rely on end-to-end physical link connectivity; when the link is completely broken, the routing protocol fails, preventing critical disaster alarm data trapped in these islands from being transmitted. Furthermore, in existing technologies, fixed lighting nodes and mobile devices typically belong to different subsystems and are independent of each other. Therefore, how to break the rigid mechanisms of existing technologies and design a routing method that can dynamically adapt to the complex interference environment of tunnels and utilize opportunistic relay to achieve data breakthroughs under extreme network outage conditions has become a pressing technical challenge in the field of emergency communication in underground spaces. Summary of the Invention

[0006] This addresses the technical problems of existing wireless ad hoc networks in underground spaces being prone to network congestion when facing strong electromagnetic interference, and being unable to transmit critical data when physical links are broken due to disasters, creating "information islands".

[0007] This application provides a frequency hopping and opportunistic routing method for self-organizing tunnel emergency lighting networks, which adopts the following technical solution: A frequency hopping and opportunistic routing method for tunnel emergency lighting ad hoc networks, applied to ad hoc networks comprising multiple fixed nodes, a target node, and at least one mobile relay node, comprising: S1. Each of the fixed nodes periodically collects channel quality indicators and compares the channel quality indicators with a preset disconnection threshold to determine the multi-hop link connectivity status to the target node; and listens to the mobile relay node, records its occurrence frequency and dwell time, and calculates the availability probability to characterize the expected reachability. S2. When any of the fixed nodes acquires a data packet to be sent, it selects a normal, frequency hopping, or relay mode based on the channel quality index, the multi-hop link connectivity status, and the availability probability. S31. Normal mode: If the multi-hop link is connected and the channel quality index is not lower than the preset quality threshold, the fixed node forwards the data packet to be sent through the multi-hop link; S32. Frequency hopping mode: If the multi-hop link is connected, the channel quality index is lower than the preset quality threshold and not lower than the preset disconnection threshold, and the availability probability is lower than the preset probability threshold, the fixed node selects a backup channel to send a message containing the channel number and switching time to the adjacent fixed node for synchronous switching, and then forwards the data packet to be sent through the multi-hop link; S33. Relay Mode: If the multi-hop link is disconnected, or the multi-hop link is connected but the channel quality index is lower than the preset quality threshold and not lower than the preset disconnection threshold, and the availability probability is not lower than the preset probability threshold, the fixed node stores the data packet to be sent in the buffer queue and sets the maximum buffer duration and forwarding priority, and sends the data packet to be sent when the mobile relay node is detected.

[0008] The above technical solution involves periodically collecting channel quality indicators from each fixed node, determining the connectivity status of multi-hop links, and calculating the availability probability based on the frequency of occurrence and dwell time of the mobile relay node to characterize its expected reachability. Based on this, when any fixed node acquires the data packet to be sent, it collaboratively selects between normal mode, frequency hopping mode, and relay mode based on the above three core parameters. In particular, this solution precisely identifies the "grayscale interference state" where the multi-hop link is not physically disconnected but its quality has severely degraded by strictly setting the judgment range of the channel quality indicator being "below the preset quality threshold and not below the preset disconnection threshold." In this state, if the availability probability is lower than the preset probability threshold, the fixed node actively selects the backup channel and synchronously switches to restore communication; if the multi-hop link is completely disconnected, or in the aforementioned grayscale state and the availability probability is not lower than the preset probability threshold, the fixed node buffers the data packet to be sent and sets the buffer duration and forwarding priority, waiting for the mobile relay node to arrive before attempting to send it. This mechanism breaks the rigidity of existing technologies where frequency hopping and opportunistic routing are independent and fixed nodes and mobile devices belong to different subsystems. It eliminates system deadlock caused by overlapping threshold boundaries or logical blind spots, and achieves significant anti-damage effects such as active frequency hopping avoidance under strong interference and collaborative breakthrough under extreme network outages.

[0009] Optionally, the fixed node is an intelligent emergency lighting node deployed in underground space, and the mobile relay node is an inspection robot or a handheld mobile terminal with a regular inspection trajectory.

[0010] The above technical solution concretizes the fixed nodes as intelligent emergency lighting nodes and the mobile relay nodes as inspection robots or handheld mobile terminals, making full use of existing infrastructure resources in underground spaces. This method directly reuses the hardware deployment of existing lighting and inspection systems, greatly reducing network construction costs; at the same time, since the scheduling trajectory of inspection equipment is relatively fixed, the calculation of the availability probability in step S1 has a stable and highly predictive data foundation.

[0011] Optionally, in step S1, the channel quality indicators include background noise level, packet loss rate, signal-to-noise ratio, and link delay; each of the fixed nodes collects the channel quality indicators by periodically sending and receiving routing probe messages.

[0012] The above technical solution limits the channel quality indicators to include background noise level, packet loss rate, signal-to-noise ratio, and link delay. This allows the fixed node to comprehensively evaluate the channel status from multiple dimensions at both the physical and link layers, completely avoiding misjudgments based on a single indicator in underground environments with severe multipath effects. Active detection enables the quality data to sensitively capture dynamic fluctuations within the tunnel, providing reliable support for the subsequent accurate triggering of various modes.

[0013] Optionally, in S1, the specific process for calculating the available probability is as follows: S11. Obtain the occurrence frequency and dwell time of the mobile relay node; S12. Introduce a time decay factor to update the historical occurrence frequency and dwell time, normalize the updated values, and then sum them according to a preset weight coefficient to obtain the available probability.

[0014] The above technical solution innovatively introduces a time decay factor to dynamically update historical frequency and dwell time, giving the originally abstract expected reachability a quantitative calculation model resistant to interference. This mechanism allows recently frequently appearing nodes to obtain a higher availability probability, effectively filtering out the misleading influence of historical "zombie nodes" such as those undergoing maintenance on system decisions, and preventing fixed nodes from blindly waiting for unreachable relay resources.

[0015] Optionally, in step S32, the specific process by which the fixed node selects a backup channel includes: S3201. Each of the fixed nodes maintains an unavailable channel list, adds channels whose channel quality indicators are consistently lower than the preset quality threshold to the unavailable channel list, and starts an aging timer for the added channels, removing them from the unavailable channel list after the timer expires. S3202. Avoid the channels in the unavailable channel list and comprehensively evaluate the background noise level and packet loss rate measured in history to select the backup channel.

[0016] The above technical solution, by maintaining the unavailable channel list and configuring an aging timer, enables automatic removal and dynamic recycling of degraded channels upon timeout, completely eliminating the system-level risk of network spectrum depletion caused by channels "only entering and not exiting" in complex underground electromagnetic environments, and improving long-term communication stability after frequency hopping.

[0017] Optionally, in step S33, the specific process of allocating forwarding priorities includes: S3301. Extract the service type of the data packet to be sent, assign a quantified data packet urgency according to a preset mapping table, and the data packet carrying the fire alarm signal has the highest data packet urgency. S3302. Start a life timer for the data packet to be sent and set the maximum buffer duration; S3303. Calculate the comprehensive weight of each data packet to be sent in the queue in real time. The comprehensive weight is positively correlated with the urgency of the data packet and negatively correlated with the remaining duration of the survival timer. The data packets are arranged in descending order of the comprehensive weight to be sent with priority.

[0018] The above technical solution abandons the rigid first-in, first-out (FIFO) mechanism. A dynamic priority algorithm to prevent expiration is constructed by calculating a comprehensive weight determined by the urgency of the data packet and the remaining duration of the survival timer. This ensures that when a connection is established, alarm data that is more urgent and closer to the timeout limit receives a higher comprehensive weight, thus solving the logical problem of high-risk, rapidly expiring data being easily deleted or discarded by the system within a very limited communication window.

[0019] Optionally, in step S33, the step of establishing a bidirectional connection when the mobile relay node is detected includes: S3304. The fixed node and the mobile relay node perform two-way authentication using digital certificates or locally pre-stored public keys; S3305. After the two-way verification is successful, both parties establish a secure transmission connection through a challenge-response mechanism; and apply a transmission lock to the data packet to be sent that is in the priority sending state, and suspend the corresponding survival timer.

[0020] The above technical solution enables the construction of a secure communication handshake loop in a zero-trust environment by using digital certificates or locally pre-stored public keys to perform two-way authentication and negotiate keys in isolated environments where extreme disasters cause the network to lose centralized authentication capabilities. This effectively prevents the theft of critical disaster data by illegally disguised devices.

[0021] Optionally, each of the mobile relay nodes announces its existence by broadcasting a relay announcement; when there are multiple mobile relay nodes, step S33 further includes the step of evaluating the multiple mobile relay nodes to select a target relay node: S3306. Extract the remaining energy information carried in the relay announcement, determine the consistency between the current movement direction of the mobile relay node and the direction of the target node, and obtain the available probability corresponding to the mobile relay node. S3307. Based on the remaining energy information, the availability probability, and the consistency, calculate the relay utility value according to the preset utility weight, and select the node with the highest relay utility value as the target relay node.

[0022] The above technical solution involves a weighted evaluation based on the remaining energy information, availability probability, and consistency when multiple relay resources exist. Remaining energy prevents power outages, availability probability ensures reliable historical behavior, and consistency guarantees that the data packet to be sent can be carried along the tunnel exit rather than deeper. The optimal combination of these three factors maximizes delivery timeliness.

[0023] Optionally, when the target relay node moves while carrying the data packet to be sent, if it finds that a direct connection has been established with the target node, it directly submits the data packet to be sent to the target node in a single hop; if it establishes a connection with other fixed nodes, it integrates into the multi-hop link as an ordinary relay node to complete data forwarding.

[0024] The above technical solution endows the mobile relay node with the ability to dynamically switch roles. Once a direct connection is detected, it actively submits a single hop, or after leaving the network outage blind spot, it integrates into the surrounding normal link to complete the relay. This allows the data packets to be sent to arrive ahead of time without having to wait for the entire process, greatly reducing end-to-end transmission latency.

[0025] Optional steps include data cleaning: S41. After the mobile relay node successfully delivers the data packet to be sent to the target node or integrates it into the network for forwarding, it clears the data packet to be sent from its own cache. S42. After the target node successfully receives the data packet to be sent, it broadcasts an acknowledgment message. After the fixed node that generated the data packet to be sent receives the acknowledgment message, or after the survival timer times out and the transmission lock is not applied, it completely removes the data packet to be sent from the queue.

[0026] The above technical solution establishes a robust data cleanup loop to prevent memory overflow. It requires mobile relay nodes to immediately clear the pending data packets from their caches after handover; simultaneously, by combining broadcast acknowledgment information with the timeout mechanism of the survival timer, the limited storage space of the fixed nodes within the isolated network can be safely and promptly reclaimed, ensuring long-term network sustainability during disasters.

[0027] In summary, this application includes at least one of the following beneficial technical effects: 1. When the data packet to be sent is acquired at any of the fixed nodes in step S2, a collaborative decision is made based on the channel quality index, the multi-hop link connectivity status, and the availability probability. This not only endows all intermediate forwarding nodes in the network with the ability to withstand damage and recover, but also constructs a rigorous and blind-zone-free mutually exclusive triggering closed loop: when the multi-hop link is connected, the channel quality index is lower than the preset quality threshold but not lower than the preset disconnection threshold, and the availability probability is lower than the preset probability threshold, a frequency hopping mode is triggered for active avoidance; when the multi-hop link is disconnected, or the channel quality index is in the aforementioned range and the availability probability is not lower than the preset probability threshold, a relay mode is triggered. This mechanism completely breaks the rigid situation where frequency hopping and opportunistic routing are separated in traditional networks. Through rigorous mathematical boundary judgment, it solves the logical conflict deadlock of the network in the interference gray range and avoids the risk of missing highly reliable relay nodes due to blind frequency hopping.

[0028] 2. By introducing the time decay factor in step S1, the occurrence frequency and dwell time of the mobile relay node are updated and calculated. The updated values ​​are then normalized and weighted by a preset weight coefficient to obtain the availability probability. This mechanism transforms the originally highly random mobile relay resources into quantifiable and dynamically decaying expected indicators, effectively filtering out the interference of "zombie nodes" that have not appeared for a long time due to downtime or maintenance, and providing an extremely accurate quantitative basis for determining whether the fixed node is worthwhile to wait in place. 3. In step S33, the survival timer is started for the data packets to be sent and a maximum buffering time is set. At the same time, the comprehensive weight value, which is positively correlated with the urgency of the data packets and inversely correlated with the remaining time of the survival timer, is calculated in real time and arranged in descending order of the comprehensive weight value for priority sending. This algorithm addresses the logical pain point of high-risk, rapidly expiring data being automatically discarded by the system in traditional queues. It ensures that the more urgent the disaster alarm data and the closer it is to the timeout limit, the higher its comprehensive weight, thereby enabling the data packets to be sent to break through preferentially within an extremely limited communication window. Attached Figure Description

[0029] Figure 1 This paper presents a schematic diagram of a frequency hopping and opportunistic routing method for an ad hoc network of tunnel emergency lighting according to this application. Figure 2 This is a schematic diagram of the overall topology of the tunnel emergency lighting self-organizing network in this embodiment; Figure 3 This is a schematic diagram of the mode selection logic and processing flow in this embodiment; Figure 4 This is a schematic diagram of the data interaction and cleanup process in the relay mode of this embodiment. Detailed Implementation

[0030] The following is in conjunction with the appendix Figures 1 to 4 As shown, this application will be further described in detail. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit this application.

[0031] 1. A frequency hopping and opportunistic routing method for tunnel emergency lighting ad hoc networks, applied to ad hoc networks comprising multiple fixed nodes, a target node, and at least one mobile relay node, comprising: S1. Each of the fixed nodes periodically collects channel quality indicators and compares the channel quality indicators with a preset disconnection threshold to determine the multi-hop link connectivity status to the target node; and listens to the mobile relay node, records its occurrence frequency and dwell time, and calculates the availability probability to characterize the expected reachability. S2. When any of the fixed nodes acquires a data packet to be sent, it selects a normal, frequency hopping, or relay mode based on the channel quality index, the multi-hop link connectivity status, and the availability probability. S31. Normal mode: If the multi-hop link is connected and the channel quality index is not lower than the preset quality threshold, the fixed node forwards the data packet to be sent through the multi-hop link; S32. Frequency hopping mode: If the multi-hop link is connected, the channel quality index is lower than the preset quality threshold and not lower than the preset disconnection threshold, and the availability probability is lower than the preset probability threshold, the fixed node selects the backup channel and sends a message containing the channel number and switching time to the adjacent fixed node for synchronous switching, and then forwards the data packet to be sent through the multi-hop link; S33. Relay Mode: If the multi-hop link is disconnected, or the multi-hop link is connected but the channel quality index is lower than the preset quality threshold and not lower than the preset disconnection threshold, and the availability probability is not lower than the preset probability threshold, the fixed node stores the data packet to be sent in the buffer queue and sets the maximum buffer duration and forwarding priority, and sends the data packet to be sent when the mobile relay node is detected.

[0032] In a tunnel scenario, multiple fixed nodes can be arranged at intervals along the tunnel's length. Fixed nodes G, F, E, D, C, B, and A are sequentially arranged along the tunnel's exit or entrance direction. For example, a smart emergency lighting node can be placed every 20 meters as a fixed node. At least one emergency control center is set up at the tunnel exit or entrance as a target node. Several mobile relay nodes (such as inspection robots or handheld mobile terminals with regular inspection trajectories) move along a preset path within the tunnel. These mobile relay nodes can communicate with each of the fixed nodes along the way. All the fixed nodes form a self-organizing emergency lighting network oriented towards underground spaces and tunnel scenarios through wireless communication networking.

[0033] In actual tunnel operation (e.g., when subway trains pass by or large electromechanical equipment starts and stops), strong electromagnetic interference or temporary physical blockages often occur. Therefore, each fixed node needs to rely on periodically collected channel quality indicators to perceive the severity of the current environment and compare these indicators with a preset disconnection threshold. If the index is lower than the threshold, the multi-hop link to the target node is determined to be broken. Simultaneously, each fixed node actively listens for mobile relay nodes entering its communication range. By recording the historical patterns of these mobile relay nodes' tunnel inspections (such as frequency of appearance and dwell time), each fixed node calculates an availability probability characterizing the expected reachability of the mobile relay node. This probability is used to predict the likelihood of the mobile relay node reappearing in the near future and providing stable relay services.

[0034] Each fixed node periodically collects channel quality indicators and determines the multi-hop link connectivity status with the target node. Taking a fixed node G as an example: Fixed node G sends a route probe message to its neighboring fixed node F every 1 second, and receives probe messages and acknowledgments from its neighboring fixed node F, in order to collect the channel quality indicators, including parameters such as background noise level, packet loss rate, signal-to-noise ratio and link delay.

[0035] Next, the fixed node G compares the collected channel quality index with the preset disconnection threshold. As an example, when it is determined that the current link packet loss rate continuously exceeds 30%, the fixed node G determines that the multi-hop link from itself to the target node is disconnected; conversely, if the channel quality index is not lower than the preset disconnection threshold, it is in a connected state.

[0036] Simultaneously, the fixed node G continuously listens for relay announcements broadcast by the mobile relay node within its communication range to obtain the frequency of occurrence and dwell time of the mobile relay node. The fixed node G introduces a time decay factor to update the historical frequency of occurrence and dwell time, normalizes the updated values ​​(e.g., mapping them to the interval between 0 and 1), and then performs a weighted summation according to preset weighting coefficients (e.g., frequency of occurrence weighted at 0.6, dwell time weighted at 0.4) to obtain the availability probability. This availability probability directly characterizes the reliability of the fixed node G's expected data forwarding through the mobile relay node.

[0037] When any of the fixed nodes (e.g., an environmental sensor inside fixed node G suddenly detects abnormal high temperature or dense smoke and generates data, or receives data from a deep node) acquires a data packet to be sent, the fixed node makes a cooperative selection among normal mode, frequency hopping mode, or relay mode based on the channel quality indicators, the multi-hop link connectivity status, and the availability probability: Execution logic in normal mode Under normal, stable operation of the tunnel, if fixed node G determines that the multi-hop link is connected and the channel quality indicators are not lower than a preset quality threshold (e.g., packet loss rate less than 10%, signal-to-noise ratio greater than 20dB), it indicates that the current channel is unobstructed and free from significant interference. In this case, fixed node G maintains its current communication strategy and directly forwards the data packets to be sent hop-by-hop along the preset routing table "Node G -> Node F -> Node E -> Target Node" through the multi-hop link to ensure low latency in data transmission.

[0038] Execution logic of frequency hopping mode When a localized area of ​​the tunnel experiences sudden, severe interference (e.g., large-scale electromechanical construction causing suppression of the original frequency band), if fixed node F determines that the multi-hop link is connected, the channel quality index is lower than the preset quality threshold but not lower than the preset disconnection threshold, and the availability probability is lower than the preset probability threshold (e.g., lower than 0.3, indicating that no reliable mobile relay node has passed recently), fixed node F will trigger a frequency hopping mode to actively avoid interference. Fixed node F comprehensively evaluates historically measured background noise levels and packet loss rates to select a clean backup channel and sends a message containing the channel number and switching time to adjacent fixed nodes (e.g., node G, node E) for synchronized switching. After switching, the multi-hop link is re-established based on the clean backup channel, and subsequently, the data packets to be sent are forwarded via the multi-hop link.

[0039] To prevent being deceived by "high-interference, high-energy" noise in the complex electromagnetic environment of underground spaces, the specific determination mechanism for "channel quality indicators falling below the preset quality threshold" adopts a joint evaluation of physical layer and link layer parameters: Evaluation metrics collection: Received signal strength indicator (RSSI), signal-to-noise ratio (SNR), and packet loss rate (PER) are collected in real time at each fixed node. Joint channel quality score calculation: Each node introduces a sliding time window of length Tw. At the end of each sliding time window, the node calculates the current channel quality score. Q=ω1⋅RSSInorm+ω2⋅SNRnorm−ω3⋅PER In the formula, RSSInorm is the normalized signal strength; SNRnorm is the normalized signal-to-noise ratio; PER is the actual packet loss rate; ω1, ω2, and ω3 are all preset weighting coefficients of the system. The system triggers and sends the message containing the channel number and handover time based on the extreme packet loss rate within a very short period or the quality score Q within a continuous window being lower than the preset quality threshold and not lower than the preset disconnection threshold.

[0040] Execution logic of relay mode In extreme disaster scenarios (e.g., physical damage causing the physical network to be blocked, resulting in node G forming an information island), if the multi-hop link is found to be disconnected, or the multi-hop link is connected but the channel quality index is lower than the preset quality threshold and not lower than the preset disconnection threshold, and the availability probability is not lower than the preset probability threshold (e.g., higher than 0.7, indicating that a highly regular inspection robot is about to pass by), the fixed node G will trigger relay mode and temporarily suspend transmission.

[0041] The fixed node G buffers the pending data packets into the queue and sets the buffer duration and forwarding priority for each packet. For example, the pending data packet carrying a fire alarm signal is assigned the highest quantized data packet urgency level, Eval, and a survival timer with a set maximum buffer duration, Tmax, is started. The system uses the following formula: Wi=μ1⋅Eval+μ2⋅(Twait / Tmax) The overall weight Wi of each pending data packet in the queue is calculated in real time, where Twait is the waiting time (equal to the maximum buffer time minus the remaining time of the timer), and μ1 and μ2 are weights. This formula ensures that the overall weight is positively correlated with the urgency of the data packet and inversely correlated with the remaining time of the timer (i.e., the longer the wait and the closer to timeout, the higher the overall weight), and the packets are arranged in descending order of their overall weight for priority transmission.

[0042] When the mobile relay node (such as an inspection robot) enters the communication range, the fixed node and the mobile relay node perform two-way authentication using digital certificates or locally pre-stored public keys. After successful two-way authentication, both parties establish a secure transmission connection through a challenge-response mechanism. Subsequently, the fixed node sends the data packets to be sent (i.e., prioritizing high-priority data packets that are about to expire and are picked up by the robot). The mobile relay node physically carries the data packets to be sent along the tunnel. If it finds that a direct connection has been established with the target node, it directly submits the data packets to the target node in a single hop. If a connection is established with other fixed nodes, it integrates into the multi-hop link as a regular relay node to complete data forwarding.

[0043] In S1 above, the specific process for calculating the available probability is as follows: S11. Obtain the occurrence frequency and dwell time of the mobile relay node; S12. Introduce a time decay factor to update the historical occurrence frequency and dwell time, normalize the updated values, and then sum them according to a preset weight coefficient to obtain the available probability.

[0044] In the tunnel scenario, fixed node G retrieves passage records and updates the historical occurrence frequency and dwell time using an exponential moving average algorithm (e.g., a time decay factor of 0.7). This gives higher weight to robots that have appeared frequently recently, while the weight of maintenance equipment that has not appeared for a long time naturally decays. The updated values ​​are then mapped to a range of 0 to 1 for normalization and weighted summed according to preset weight coefficients. The higher the available probability, the stronger the regularity of the mobile relay node's timely inspection.

[0045] In S32 above, the specific process by which the fixed node selects a backup channel includes: S3201. Each of the fixed nodes maintains an unavailable channel list, adds channels whose channel quality indicators are consistently lower than the preset quality threshold to the unavailable channel list, and starts an aging timer for the added channels, removing them from the unavailable channel list after the timer expires. S3202. Avoid the channels in the unavailable channel list and comprehensively evaluate the background noise level and packet loss rate measured in history to select the backup channel.

[0046] In actual operation, to prevent the available channels from becoming depleted due to only receiving traffic, fixed node F blacklists and adds to the unavailable channel list any interference frequencies that are consistently below the preset quality threshold. Then, a 30-minute aging timer is started. When frequency hopping mode is triggered, channels in the unavailable channel list (blacklist) are strictly avoided. From the remaining available channels, a comprehensive evaluation is conducted to select the clean channel with the lowest historical background noise and the lowest packet loss rate as the backup channel.

[0047] In S33 above, the specific process of allocating forwarding priorities includes: S3301. Extract the service type of the data packet to be sent, assign a quantified data packet urgency according to a preset mapping table, and the data packet carrying the fire alarm signal has the highest data packet urgency. S3302. Start a life timer for the data packet to be sent and set the maximum buffer duration; S3303. Calculate the comprehensive weight of each data packet to be sent in the queue in real time. The comprehensive weight is positively correlated with the urgency of the data packet and negatively correlated with the remaining duration of the survival timer. The data packets are arranged in descending order of the comprehensive weight to be sent with priority.

[0048] Specifically, when a smoke exceedance alarm is generated, node G assigns the highest urgency level of 100 to the pending data packet carrying the fire alarm signal and sets a maximum buffer duration of 60 seconds to start the survival timer. Based on the aforementioned formula, the comprehensive weight is calculated, and the pending data packets with the shortest remaining survival time and the most critical situation are prioritized to ensure they are sent immediately upon robot arrival, preventing expired alarms from clogging the network.

[0049] In S33 above, the step of establishing a bidirectional connection when the mobile relay node is detected includes: S3304. The fixed node and the mobile relay node perform two-way authentication using digital certificates or locally pre-stored public keys; S3305. After the two-way verification is successful, both parties establish a secure transmission connection through a challenge-response mechanism; and apply a transmission lock to the data packet to be sent that is in the priority sending state, and suspend the corresponding survival timer.

[0050] To prevent unauthorized devices from stealing data in an isolated environment, the fixed node G and the nearby mobile relay node mutually verify each other's digital credentials using their legitimate public keys (two-way verification). After successful verification, both parties exchange random challenge codes and encrypt responses with their private keys to generate temporary session keys. A secure, eavesdropping-resistant transmission connection is established through the challenge-response mechanism. To prevent high-priority data packets from being mistakenly cleared by the system's underlying layer due to timeouts during the handshake process of establishing a secure connection, once the secure transmission connection is established, the fixed node applies a transmission lock to the data packet at the head of the current queue (marking its status as 'sending') and simultaneously suspends (pauses) its timer, fundamentally eliminating the race condition between data forwarding and timeout cleanup.

[0051] When there are multiple mobile relay nodes (i.e., multiple mobile relay nodes enter simultaneously), step S33 further includes the step of evaluating the multiple mobile relay nodes to select a target relay node: S3306. Extract the remaining energy information carried in the relay announcement, determine the consistency between the current movement direction of the mobile relay node and the direction of the target node, and obtain the available probability corresponding to the mobile relay node. S3307. Based on the remaining energy information, the availability probability, and the consistency, calculate the relay utility value according to the preset utility weight, and select the node with the highest relay utility value as the target relay node.

[0052] Each of the fixed nodes calculates the relay utility value U using the following mathematical model: U=η1⋅Enorm+η2⋅Pavail+η3⋅Dcos In the formula, Enorm represents the normalized remaining energy information; Pavail represents the availability probability; Dcos represents the consistency quantization value between the current movement direction of the mobile relay node and the direction pointing to the target node, which is obtained by mapping the cosine of the angle between the two; η1, η2, and η3 are preset utility weight coefficients corresponding to the remaining energy information, availability probability, and direction consistency, respectively, where η1, η2, and η3 are all non-negative numbers, and η1 + η2 + η3 = 1. Each fixed node calculates the relay utility value by combining the remaining energy information, availability probability, and consistency quantization value, and selects the mobile relay node with the highest relay utility value as the target relay node.

[0053] Finally, this method also includes a data cleaning step: S41. After the mobile relay node successfully delivers the data packet to be sent to the target node or integrates it into the network for forwarding, it clears the data packet to be sent from its own cache. S42. After the target node successfully receives the data packet to be sent, it broadcasts an acknowledgment message. After the fixed node that generated the data packet to be sent receives the acknowledgment message, or after the survival timer times out and the transmission lock is not applied, it completely removes the data packet to be sent from the queue.

[0054] After the mobile relay robot completes the data handover at node E, it immediately clears the pending data packets from its own cache to prevent memory overflow. The target node sends an acknowledgment message back to the fixed node G within the island. Upon receiving the acknowledgment message, or if the survival timer expires due to a network outage, the fixed node G completely removes the pending data packets from the queue, releasing limited memory resources and ensuring the long-term stable operation of the entire network.

[0055] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A frequency hopping and opportunistic routing method for tunnel emergency lighting ad hoc networks, applied to ad hoc networks containing multiple fixed nodes, target nodes, and mobile relay nodes, characterized in that, include: S1. Each of the fixed nodes periodically collects channel quality indicators and compares the channel quality indicators with a preset disconnection threshold to determine the multi-hop link connectivity status to the target node; and listens to the mobile relay node, records its occurrence frequency and dwell time, and calculates the availability probability to characterize the expected reachability. S2. When any of the fixed nodes acquires a data packet to be sent, it selects a normal, frequency hopping, or relay mode based on the channel quality index, the multi-hop link connectivity status, and the availability probability. S31. Normal mode: If the multi-hop link is connected and the channel quality index is not lower than the preset quality threshold, the fixed node forwards the data packet to be sent through the multi-hop link; S32. Frequency hopping mode: If the multi-hop link is connected, the channel quality index is lower than the preset quality threshold and not lower than the preset disconnection threshold, and the availability probability is lower than the preset probability threshold, the fixed node selects the backup channel and sends a message containing the channel number and switching time to the adjacent fixed node for synchronous switching, and then forwards the data packet to be sent through the multi-hop link; S33. Relay Mode: If the multi-hop link is disconnected, or the multi-hop link is connected but the channel quality index is lower than the preset quality threshold and not lower than the preset disconnection threshold, and the availability probability is not lower than the preset probability threshold, the fixed node stores the data packet to be sent in the buffer queue and sets the maximum buffer duration and forwarding priority, and sends the data packet to be sent when the mobile relay node is detected.

2. The tunnel emergency lighting self-organizing network frequency hopping and opportunistic routing method according to claim 1, characterized in that, The fixed nodes are intelligent emergency lighting nodes deployed in underground spaces, and the mobile relay nodes are inspection robots or handheld mobile terminals with regular inspection trajectories.

3. The tunnel emergency lighting self-organizing network frequency hopping and opportunistic routing method according to claim 1, characterized in that, In step S1, the channel quality indicators include background noise level, packet loss rate, signal-to-noise ratio, and link delay; each fixed node collects the channel quality indicators by periodically sending and receiving routing probe messages.

4. The tunnel emergency lighting self-organizing network frequency hopping and opportunistic routing method according to claim 1, characterized in that, In S1, the specific process for calculating the available probability is as follows: S11. Obtain the occurrence frequency and dwell time of the mobile relay node; S12. Introduce a time decay factor to update the historical occurrence frequency and dwell time, normalize the updated values, and then sum them according to a preset weight coefficient to obtain the available probability.

5. The tunnel emergency lighting self-organizing network frequency hopping and opportunistic routing method according to claim 3, characterized in that, In step S32, the specific process by which the fixed node selects a backup channel includes: S3201. Each of the fixed nodes maintains an unavailable channel list, adds channels whose channel quality indicators are consistently lower than the preset quality threshold to the unavailable channel list, and starts an aging timer for the added channels, removing them from the unavailable channel list after the timer expires. S3202. Avoid the channels in the unavailable channel list and comprehensively evaluate the background noise level and packet loss rate measured in history to select the backup channel.

6. The tunnel emergency lighting self-organizing network frequency hopping and opportunistic routing method according to claim 1, characterized in that, In step S33, the specific process of allocating forwarding priorities includes: S3301. Extract the service type of the data packet to be sent, assign a quantified data packet urgency according to a preset mapping table, and the data packet carrying the fire alarm signal has the highest data packet urgency. S3302. Start a life timer for the data packet to be sent and set the maximum buffer duration; S3303. Calculate the comprehensive weight of each data packet to be sent in the queue in real time. The comprehensive weight is positively correlated with the urgency of the data packet and negatively correlated with the remaining duration of the survival timer. The data packets are arranged in descending order of the comprehensive weight to be sent with priority.

7. The tunnel emergency lighting self-organizing network frequency hopping and opportunistic routing method according to claim 6, characterized in that, In step S33, the step of establishing a bidirectional connection when the mobile relay node is detected includes: S3304. The fixed node and the mobile relay node perform two-way authentication using digital certificates or locally pre-stored public keys; S3305. After the two-way verification is successful, both parties establish a secure transmission connection through a challenge-response mechanism; and apply a transmission lock to the data packet to be sent that is in the priority sending state, and suspend the corresponding survival timer.

8. The tunnel emergency lighting self-organizing network frequency hopping and opportunistic routing method according to claim 1, characterized in that, Each of the mobile relay nodes announces its existence by broadcasting a relay announcement; when there are multiple mobile relay nodes, step S33 further includes the step of evaluating the multiple mobile relay nodes to select a target relay node: S3306. Extract the remaining energy information carried in the relay announcement, determine the consistency between the current movement direction of the mobile relay node and the direction of the target node, and obtain the available probability corresponding to the mobile relay node. S3307. Based on the remaining energy information, the availability probability, and the consistency, calculate the relay utility value according to the preset utility weight, and select the node with the highest relay utility value as the target relay node.

9. The tunnel emergency lighting self-organizing network frequency hopping and opportunistic routing method according to claim 8, characterized in that, When the target relay node moves carrying the data packet to be sent, if it finds that a direct connection has been established with the target node, it directly submits the data packet to the target node in a single hop; if it establishes a connection with other fixed nodes, it integrates into the multi-hop link as an ordinary relay node to complete data forwarding.

10. The tunnel emergency lighting self-organizing network frequency hopping and opportunistic routing method according to claim 7, characterized in that, It also includes data cleaning steps: S41. After successfully delivering the data packet to be sent to the target node or integrating it into the network for forwarding, the mobile relay node clears the data packet to be sent from its own cache; S42. After successfully receiving the data packet to be sent, the target node broadcasts a confirmation message; The fixed node that generated the data packet to be sent will completely remove the data packet from the queue after receiving an acknowledgment message, or after the survival timer expires and the transmission lock is not applied.

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