Exploiting multipath fading with a mobile robot

Abstract

In indoor or urban applications, a moving robot with wireless communications will experience multipath fading. This causes rapid signal strength variations due to interfering reflections of the radio signal. By making short stops at positions with high signal-to-noise ratio (SNR), the robot can trade trajectory tracking accuracy for increased link quality. This represents a type of opportunistic communication-aware motion planning. We propose two novel strategies for improving the link capacity or throughput when either the robot has full knowledge of how the SNR varies along the trajectory, or when only the SNR distribution is known or can be estimated. In the latter case, this leads to an optimal stopping problem over a finite horizon. Both cases are analyzed for independent as well as correlated SNR samples, and a bounded maximum trajectory tracking error. We derive the resulting SNR distributions for the proposed strategies and use them to show how the expected capacity and throughput vary with the allowed tracking error. The results are confirmed by simulations and experiments. Experiments in six different locations validate the communication model and show that the proposed motion planning is robust to non-static fading and can yield throughput improvements of more than 100%.

A directional antenna based leader–follower relay system for end-to-end robot communications

“…Radio signal strength has been widely used in robotics literature for predictions and improvements in wireless communication performance [35], [36]. The received signal strength (RSS) is given by [37], [38]:…”

“…While the path loss fading due to distance is deterministic, the shadowing and multipath fading are often modeled as stochastic processes with (zero-mean) Gaussian and Nakagami distribution respectively. Precisely modeling the shadowing and multipath effects are difficult [38], [39], and often not required in the proposed application as they are relatively smaller in effects compared to fading. Nevertheless, in our bearing estimation algorithm, the multipath effects are filtered out due to (spatial) averaging of the signal values over the angular spectrum.…”

A Spatiotemporal Optimal Stopping Problem for Mission Monitoring with Stationary Viewpoints

“…Recently, Lindhé and Johansson [30] study an optimal stopping problem for a robot that communicates with a base station while traversing a predefined path. The robot must choose stopping points that maximise communication quality while also making progress along its path.…”

Robotic Mobility Diversity Algorithm with Continuous Search Space

“…Now, a new class of diversity, referred to as mobility diversity, has recently started to be developed in the context of robotic communications. Algorithms implementing this type of diversity are called mobility diversity algorithms (MDAs) [1], [2].…”