Cooperative Communications in Mobile Ad Hoc Networks

摘要

The motivation of this article is to clarify and help resolve the gap between the link abstraction used in traditional wireless networking and its much broader definition used in the context of cooperative communications, which has received significant interest as an untapped means for improving performance of relay transmission systems operating over the ever-challenging wireless medium. The common theme of most research in this area is to optimize physical layer performance measures without considering in much detail how cooperation interacts with higher layers and improves network performance measures. Because these issues are important for enabling cooperative communications to practice in real-world networks, especially for the increasingly important class of mobile ad hoc networks (MANETs), the goals of this article are to survey basic cooperative communications and outline two potential architectures for cooperative MANETs. The first architecture relies on an existing clustered infrastructure: cooperative relays are centrally controlled by cluster heads. In another architecture without explicit clustering, cooperative links are formed by request of a source node in an ad hoc, decentralized fashion. In either case, cooperative communication considerably improves the network connectivity. Although far from a complete study, these architectures provide modified wireless link abstractions and suggest tradeoffs in complexity at the physical and higher layers. Many opportunities and challenges remain, including distributed synchronization, coding, and signal processing among multiple radios; modeling of new link abstractions at higher layers; and multiaccess and routing protocols for networks of cooperative links.