Low Power Research Based On WiFi Location Terminal

With the development of computer technology, location terminal which has been embedded in all kinds of location based service such as location based information distribution or location tracing, has more and more pervasive application in daily life. Power consumption becomes one of the most critical performance indexes, for worse and worse contradiction between higher accuracy location, which requiring higher sampling frequency that increases the CPU and communication burden, and the limited power supplied by battery, which cannot provide long running time. How to decrease the power consumption to prolong the terminal running time within high location accuracy is one of the design aims.The low power technology applied in the terminal design, can be classified into hardware and software low power design. Two methods are employed in hardware design choosing low power component, including EraSoC, Marvell WiFi chipset and ADXL330 accelerometer, and COM circuit design. Methods employed in software design include compiling optimization, low power application design technology and low power running modal. What's more, the dynamic power management used in the terminal decreases the power consumption effectively.Low power location strategy via WiFi is addressed as three steps in this thesis. First of all, we sorting and selecting the AP using the signal entropy, where the AP with the least entropy has the highest priority level. Then a radio distribution map is set up by classifying the signal from a given environment, using ISODATA algorithm, after which the online location employs the decision tree algorithm. The result of optimum AP number and their scanning times, cutting down the power consumption, can be concluded from the training procedure. The low power location strategy can be used in other wireless location.Finally, a multimedia distribution system is developed in the low power terminal, which can be widely deployed in exhibition, mall and library, providing location based service. The system is built up by three parts: management computer that makes and distributes the location and multimedia data images; the sever that provides services from terminals such as receiving, restoring and redistributing the images; and the terminal that locates the position, downloads the multimedia data from server and show it to the user. Experiments show that, the system performance can meet the application requirements.