Characterizing the impact of multi-frequency and multi-power on localization accuracy

Wireless localization using the received signal strength (RSS) can have tremendous savings over using specialized positioning infrastructures. In this work, we explore improving RSS localization performance in multipath environments by varying the transmitter's signal power and frequency. Using a theoretical analysis, we first show how selection of different signal powers and frequencies can improve localization accuracy for the least squares algorithm. We next develop a set of selection methods that attempt to select the combinations of power and frequencies which minimize the localization error. Our selection methods are based on the observed standard deviations of RSS as well as algorithm specific residuals. Using active RFID tags, we experimentally characterize the effect of using multiple signal powers and frequencies on a wide spectrum of RSS-based algorithms. We found that the performance of all the algorithms improves when leveraging on multiple power levels and frequencies, although different algorithms present different sensitivity in terms of localization accuracy under different selection methods.