Link-layer-and-above diversity in multihop wireless networks

The instability of wireless channels was a haunting issue in communications until recent exploration in utilizing variation. The same transmission might present significantly, and usually independently, different reception quality when broadcast to receivers at different locations. In addition, the same stationary receiver might experience drastic fluctuation over time as well. The combination of link-quality variation with the broadcasting nature of the wireless channel itself disclosed a direction in the research of wireless networking, namely, the utilization of diversity. In this article, we summarize the causes of channel diversity in wireless communications, and how it is perceived in different layers of multihop wireless networks. To promote new research innovations in this area, we concentrate on link-layer diversity and speculate on the challenges and potential of diversity schemes at the network layer.