ITR: Cooperative Wireless Networks

Ohio State University Research Foundation -Do Not Use, Columbus OH

Investigators

Abstract

We are in the midst of a new wireless revolution, brought on by the adoption of wireless networks for consumer, military, scientific and other applications. Wireless networks are a collection of terminals, or nodes, that are capable of transmitting and receiving information to nearby nodes using wireless access methods. The harsh characteristics of the wireless channel provide the fundamental challenge for communication between wireless network nodes. The key to reliable communication over wireless links is the exploitation of diversity, i.e., observation of the same information through different fading conditions. While it is possible to harness diversity by transmitting the same signal at different times or frequencies, the implied redundancy is costly from a bandwidth perspective. It has been shown, however, that introducing additional antennas at the source and/or destination enables diversity gain without compromise in bandwidth efficiency. Wireless network nodes may or may not be equipped with multiple antennas. How then, can they ensure reliable and efficient communication over the fading wireless channel? In this research, we investigate novel strategies by which nodes transmit and receive cooperatively, allowing exploitation of spatial diversity gain that would otherwise be unavailable. The lack of structure in ``ad-hoc'' wireless networks is advantageous from the viewpoint of flexibility, re-configurability, and low management cost. The same lack of structure, however, makes the implementation of cooperative strategies challenging. It may be difficult, for example, to know which of the helper nodes have correctly received the message. In fact, it may be difficult to know which, if any, of the nodes can be enlisted as helpers. In this research, we solve these problems through the combination of distributed cooperative coding strategies, clever protocols, and sophisticated signal processing techniques. The PIs are leveraging their respective expertise in space-time coding and blind signal processing to devise practical strategies for cooperative communication in wireless networks. In addition, this research investigates the fundamental limits on the capacity of cooperative wireless networks through a study of information-theoretic bounds.