CRBAR: Cooperative relay-based auto rate MAC for multirate wireless networks

Cooperative communication is becoming a promising technology for wireless networks by exploiting two key characteristics of the wireless medium: broadcast nature and spatial diversity. To integrate cooperation into practical systems, efficient protocols are needed across the entire protocol stack. This paper presents a novel cooperative relay-based auto rate medium access control (MAC) protocol (CRBAR) for multirate wireless networks, in which low-rate stations can be adaptively assisted by high-rate stations. Different from state-of-the-art table-based proactive relay selection schemes, a reactive relay selection scheme is developed to adapt to dynamical channel variation and network topology in which the relay candidates adaptively select themselves as the relay nodes and determine the relay scheme and transmission rates based on the instantaneous channel measurements. In terms of relay schemes, cooperative relaying can be employed whenever possible in addition to simple relaying. The receiver can improve its capability to decode the original frame by combining the information from both the sender and the relay. We have developed analytical models of different schemes for a simple scenario and carried out further simulations under a realistic fading channel and mobility model. Both analysis and simulation show that CRBAR significantly outperforms the table-based proactive relay selection scheme and direct rate adaptation scheme.