Received signal strength gradient estimation for mobile networks

This paper considers the question: As a receiver moves along a trajectory, is its received signal strength (RSS) increasing or decreasing? This is an important question for mobile receivers to answer in order to maintain or improve connectivity within the network. When signal strength maps are unavailable a priori, a receiver decides the answer based on its observations. We derive the maximum likelihood estimate (MLE) of signal strength at a particular location in Rayleigh/Rician fading and additive Gaussian noise. We estimate the slope of the gradient by making RSS estimates at multiple locations. By making estimates of the MLE variance, we can derive confidence in the gradient, which can be used to decide future movements.