Benefits of Cooperative Communication Applied to Robot Exploration

We define a wireless cooperative robotic communication network to be a network where robots cooperate in routing and/or improving the quality of transmission of each other´s communication packets. The cooperation is especially useful when the channel between a robot and base (source and destination) is in a deep shadow-fading state. In this situation increasing the power level may either not resolve the problem or be too power consuming, while generating interference for other robots operating on the same channel. A cooperating robot, which has good propagation channels to both the source and the destination, may be used to relay the packets between them. This paper presents the comparison of the average amounts of power consumed by robots in a standard network that uses single-hop transmission and a cooperative network that uses two-hop transmission. It is shown that under certain conditions the ratio of the average power consumptions in the two networks, when N cooperating robots on average are available for the source and the destination, can be approximated by k In N + q . The constants k and q are related to the propagation channel. For a Nakagami fading channel with parameter m, k = 1/lnm and q = 1, while for a shadowing channel with standard deviation sigma_dB, k = sigma_dB / radicpi and q = 0.23 sigma_dB dB.