Diversity and cooperative communications in body area networks

In this chapter, we investigate diversity and cooperative communications, and particularly cooperative diversity, for body-centric communications in wireless body area networks (BANs). Cooperative diversity for BANs is vitally important for required communications reliability, as well as increasing network and sensor lifetime by potentially reducing energy consumption, as will be shown here. We describe what is meant by cooperative communications and cooperative diversity, including a brief survey of the state-of-the-art. Description and analysis of the benefits of cooperative diversity in BANs is mainly with respect to the physical layer, but there is also some brief discussion of the MAC layer and network layer. In terms of cooperative receive diversity, feasible in IEEE 802.15.6 Standard compliant BAN, several cooperative receive combining techniques are described, which are all beneficial over single-link communications in terms of firstand second-order statistics. A simple, practical, technique of switch-and-examine combining shows good performance in terms of important metrics, and this can be further enhanced when combined with a simple “sample-and-hold” transmit power control, which can help reduce energy consumption for sensor radios.