2. Radio Signal Strength: Free Lunch for Localization?

Radio signal strength (RSS) is an attractive property in wireless networks since it can be obtained without requiring additional hardware. Based on various signal propagation models that describe the relationship between RSS and transmitter-receiver (T-R) separation distance, RSS has been widely used for localization in sensor networks and 802.11x-based wireless networks. However, the ideal propagation models, in which RSS is only determined by T-R separation distance, are far from reality. In this talk, I will present our findings from a series of experiments using MICA2 nodes in real environments to investigate other parameters besides T-R separation distance -- frequency, variation of transceivers, antenna orientation, battery voltage, temporal-spatial properties of environment, and dynamic environment. Their impacts on RSS are measured comprehensively and independently. Our work should be beneficial to researchers who want to develop practical RSS-related solutions in wireless networks. A practical example on localization will be given.