Research On Key Technologies Of Wireless Ad-hoc Network For Seismic Data Quality Monitoring System

Node seismograph is becoming more and more important in seismic exploration equipment because of its portability and flexibility.With the rapid development of wireless communication technology,wireless seismic exploration systems with data quality monitoring systems are gradually increasing,and wireless seismic exploration systems have become one of the most promising development directions of seismic exploration equipment.However,as the main equipment of wireless seismic exploration system,node seismograph often works in complex geological environment.A series of problems caused by the serious interference of complex geological environment on the wireless signal of node seismograph have become a challenging new research field.The data transmission reliability of node seismograph wireless network has always been the focus of research.At present,there are still few nodal seismometers with the function of data quality monitoring system.There are three main reasons.Firstly,in the harsh working environment in the field,the antenna of the node seismometer is close to the ground.Affected by the ground,the time-varying and asymmetry of wireless signals are enhanced,and the resulting link fluctuations and frequent changes in network topology seriously affect the reliable transmission of data packets;Secondly,in large-scale seismic exploration,data need more forwarding times to be sent to the control center,and the long link increases the impact of wireless signal fluctuation on the non-fixed topology routing algorithm;Finally,node seismographs are being developed in a low-power and miniaturized fashion.It is difficult to use high-power wireless transceivers or large antennas.In order to solve the above problems,this paper develops a wireless communication system for the node seismograph GEIWSR-? which independently developed by the National Geophysical Exploration Instrument Engineering Technology Research Center of Jilin University,and realizes the real-time state monitoring of field wireless ad hoc network.This paper puts forward a series of key technologies suitable for the field seismic exploration environment of node seismograph.These technologies ensure the reliability of node seismograph,reduce construction complexity and increase seismic exploration efficiency.In large-scale field wireless seismic exploration,the working state data and data quality information of node seismograph can be sent to the control center accurately and quickly.In order to solve the problem caused by wireless signal interference when the node seismograph is near the ground,this paper analyzes the technical difficulties of each level of the node seismometer wireless self-organizing network,and conducts in-depth research on each key problem.This paper designs and implements the software and hardware of the nodal seismograph wireless communication system,the wireless link quality estimation method based on exponentially weighted moving average,the hybrid gradient construction method based on link quality and residual energy,and the greedy geographic routing based on the connected set,and struct-free data aggregation method for node seismograph data quality monitoring system.The above research content constitutes a self-organizing network of nodal seismograph data quality monitoring system.The effectiveness and practicability of the methods designed in this paper are verified by field experiments.The main research contents of the paper are as follows:(1)Design of Wireless Communication System for Low Power Node Seismograph.Adopt low-power Zig Bee technology as the wireless communication technology solution.The wireless communication system has a micro-control unit,which uses serial communication protocol to communicate with the node seismograph,works independently of each other and does not interfere with each other,reducing the coupling of the system.Aiming at the characteristics of multi-asynchronous,multi-parallel and multi-task of the network,a micro-operating system based on event message was designed,and a set of protocol stack was implemented for the operating system.The application scenarios of node seismographs are optimized,considering the requirements of low power consumption,low resources,and complex environment.(2)To adapt to the field environment of the node seismograph and accurately obtain the wireless fluctuation,this paper designs an optimized exponentially weighted moving average to evaluate the link quality between nodes.The link quality evaluation package of the node is iteratively evaluated by using the multi-functional periodic data exchange package instead of the link quality evaluation package.At the same time,the evaluation results are supplemented and corrected by the packet sending and receiving.The evaluation results will provide data support for subsequent gradient construction methods and routing algorithms.The method is simple to calculate and suitable for low-power node seismometers.The simulation results show that the method follows the fluctuation of the wireless link well,and the experimental results prove the reliability of the method,which is suitable for the field near-ground application scenario.(3)Aiming at the problem of poor link quality of nodal seismographs,this paper proposes a Link and Energy aware Gradient Construction method LEGC suitable for nodal seismographs with multiple survey lines.LEGC considers the link quality and the residual power of the node,and introduces a concept of Link Potential Energy(LPE).LPE is the virtual energy generated by the control center in the network.It is transmitted to other nodes in the network through periodic broadcast packets.The conduction process will lose a part of the LPE according to the link potential energy loss model composed of the link quality between nodes and the residual power of the nodes.Finally,a gradient field with respect to LPE can be formed covering all nodes in the network.Since the gradient uses the link quality as the gradient construction parameter,it can reflect the link between the node and the control center,which can be used as the basis for judging the relative position of the node in the network,and is used to verify the packets sending direction in the network during routing or used as gradient data for gradient routing.The simulation results show that the gradient routing algorithm based on LEGC can effectively alleviate the influence of the wireless link fluctuation on the routing method compared with other gradient routing methods or geographic routing methods under the multi-survey line.The experimental results show that LEGC can effectively reduce the fluctuation interference of wireless signals,and the gradient data provided by LEGC can accurately reflect the link quality between the node and the control center,thereby improving the gradient routing performance of the node seismometer network.(4)In the wireless self-organizing network,the routing method is one of the key technologies.In 3D seismic exploration,the LEGC method can effectively complete the data transmission task as a routing method.In non-3D seismic surveys,too few available links,severe link quality fluctuations,GPS signal loss,and too many hops limit the performance of the routing method.In view of the above difficulties,this paper proposes a stateless Greedy Flee in the Direction Routing method(GFDR)based on the LEGC method and the regular arrangement of node seismographs.Nodes establish connection sets through periodic data exchange packets,and use the overlapping of connection sets to get relative position information of nodes in the survey line through a series of set operations.When GPS location information is reliable,greedy routing can be performed using GPS location information.When the spacing is too small,the occlusion,or the abnormal operation of the node seismometer causes the GPS location information to be unreliable,and the network falls into an irreparable routing hole,the FD mode is entered to perform greedy forwarding.FD mode is a method of greedy routing and forwarding of packets along the survey line by introducing the concept of packet history set and relative position information of nodes.The FD mode also makes full use of the long-term stability of the gradient data of the LEGC when the node seismometers are arranged in non-3D,ensuring the correct direction of data forwarding.The non-bypass routing in FD mode avoids the recovery mode in geographic routing.The simulation results show that when the GPS location information is unreliable,the routing method can reduce the delay by 55% at most,reduce the number of data packet forwarding by about 50%,and reduce the energy consumption of transmitting a data packet by at most 51%.The experimental results show that the routing method is suitable for large-scale single survey line multi-hop self-organizing networks,and the method can run stably for a long time.GFDR can effectively supplement the insufficiency of geographic routing and improve the reliability of the node seismograph wireless network.(5)Aiming at the problems of poor link and network congestion caused by the fluctuation of wireless link,this paper designs a Struct-Free Data Aggregation(SFDA)method based on the relative position of nodes.The method restricts the forwarding direction of packets according to the location information of nodes to complete the spatial constraints of the aggregation method.By predicting whether the network is blocked or not,it is decided whether to aggregate the packets to complete the time constraint.According to the packet characteristics of the node seismograph data quality monitoring system,a packet classification – split-aggregation mechanism is designed to maximize the available load of the wireless link layer data frame and improve the aggregation efficiency.SFDA can adapts to different location-based routing algorithms,and is compatible with the LEGC method and GFDR method proposed in this paper.The simulation results show that SFDA can reduce the transmission time of packets by about 55% and the number of packets by 70%.The experimental results show that the packet transmission time is reduced by about 50%.The number of packets is reduced by about 75%,which effectively improves the network performance of the node seismograph and alleviates network congestion caused by link fluctuations.