A Study On Indoor Localization Using Wireless Local Network

With the rapid development of wireless communication system and the higher demand for Location Based Service(LBS) of people, technology of GPS has been implemented in the outside location for many years. But in the complex indoor environment with building blocked, the GPS signal is relatively weak and thus indoor positioning technology has quickly been the attention of people. And the rapid development of wireless local network has quickly made the indoor location based on WLAN technology became a hot research topic. Therefore, based on the most widely used fingerprint algorithm, this article will improve the weakness and disadvantage of the algorithm itself and design the active and passive location system respectively.First of all, through reading some related material, the current indoor positioning technology has been studied, compared and summarized. And starting from the principle of the WLAN, the principle and the basic positioning methods are emphasized. Then the article will introduce the various implementation methods on the most widely used fingerprint algorithm in detail, and put forward the existing deficiency and problems.Secondly, based on the deficiency of the current fingerprint algorithm based on WLAN location, an improved adative network fingerprint algorithm is put forward, which can monitor the matching number of wireless AP in real time and adapt to network changes according to the position. And thus the position precision improves 15.4 percent. Meanwhile, in order to reduce the large position error caused by the transient instability of wireless signal, a new data correction method is proposed, which can dynamicly adjust the parameter of predict coordinates and measured coordinates based on the average speed to abtain the final postion. And the average precision and stability improve obviously, the percentage of precision growth even reaches 21.4.Then, based on the wireless local network of campus, an indoor location system based on Win7 and adapt to the improved algorithm and data correction method is designed. In this system, key modules and detailed implementation are introduced and the positioning precision is also compared with the tranditional fingerprint algorithm and analyzed the result from different angles.Finally, from the angle of the passive positioning, this article has achieved to locate the mobile terminal which enters into the positioning area through grasping signal info on the server in the background. Specifically, when a mobile terminal enters into the positioning area, all the routers will grasp the signal strength information of this terminal, and all this sinal data will be transferred to the server in the background through the NFS technology. Then in this background sever, signal data will be classified through the unique MAC address of this mobile terminal and sent to the module of algorithm to obtain the final coordinate of this terminal.