1.4 Related Work
1.4.1 Opportunistic Techniques
While opportunistic routing aims to harvest the diversity gain at the packet level, cooperative communication studies the diversity gain at the signal level. The idea of user cooperation diversity is usually attributed to Sendonaris, Erkip, and Aazhang in Sendonaris et al. (1998) but can also be traced back to the relay channel model first introduced in Meulen (1971). The relay channel generalizes the notion of a simple point-to-point channel with a single source and destination to include a relay whose sole purpose is to help transfer information from the source to the destination.
Cover and Gamal (1979) and Cover and Thomas (1991) are credited with developing most of the information theory results on relay channels. They analyzed the capacity of the relay channel under the assumption that all nodes operate in the same band. Under this assumption, the system can be decomposed into a broadcast channel from the viewpoint of the source and a multiple access channel from the viewpoint of the destination. The idea of user cooperation diversity first attracted the attention of the information theory after the paper by communit Sendonaris et al. (1998) was presented at the 1998 International Symposium on Information Theory. Many of the ideas and results that appeared in the literature shortly after Sendonaris et al. (1998) can be traced to Cover and Gamal (1979).
Sendonaris, Erkip, and Aazhang followed up on Sendonaris ...