Design And Application Of Mobile AP Wireless Local Area Network In The Near-earth Shock Wave Measurement

The near-earth blast wave measurement reflects the pressure on ground targets truly,which can provide the scientific basis for evaluating the power of weapons and the damage effects of projectiles and ground protection. With the increase in the number of measurement systems, it will put forward higher requirements for controlling and monitoring all measuring points centrally and reading the test data by wireless transmission. The near-earth wireless channel is very complicate and the wireless signal is affected seriously by the ground and the amount of overall wireless data will soar suddenly after the explosion, which make the wireless performance decreased sharply.Aimed at the above problems, a mobile AP(Access Point) wireless local area network of explosive field based on WIFI is designed in this paper. This network can be constructed anywhere quickly in the test field, which has the function of controlling and monitoring 30 sets of test nodes centrally, setting and reading the test parameters of nodes by wireless communication, whose coverage distance is 140 meters and wireless rate is more than 150 kbps. To achieve higher rate of wireless data transmission, we can adjust communication distance flexibly by moving the portable AP. In order to solve the problem of network congestion and wireless rate drop caused the burst data volume after the explosion,the transmission plan of independent choice and controllable quantity for multiple wireless data transmission is designed. The network mode of operation based on event trigger is designed, which reduces the power consumption of system and realizes the cyclic tests.To research the characteristic of 2.4 GHz wireless WIFI near-earth transmission, a wireless channel test scheme based on RSSI(received signal strength indicator) is designed.The double-linear path loss model is obtained based on the measured data, which is suitable for characterization of near-earth wireless channel through experimental verification, andwhose absolute error of path loss is less than 3dB. The double-linear path loss model predicts that the coverage range of the mobile AP wireless local area network in this paper is 123 meters. However, the coverage range obtained by free space propagation model is 1080 metres. In fact, the actual network has a coverage distance of 140 meters through experimental verification, so the prediction accuracy of double-linear model is far better than that of free space propagation model. The double-linear path loss model can provide the reliable basis for the design of near-earth wireless network.Finally, the function and performance of the system has been tested and verified. The validity and superiority of the proposed system are further verified by applying it to actual measurement experiments.