Real-time testbed implementation of a distributed cooperative MAC and PHY

We present the implementation and experimental evaluation of a new, fully distributed protocol for random access systems that exploits symbol-level physical layer cooperation. By allowing single-antenna nodes to cooperate with their neighbors, MIMO-like performance is achieved. Our Distributed On-demand Cooperation (DOC) protocol is unique in its ability to realize a cooperative mode only under circumstances where cooperation can assist. Thus, under high SNR scenarios where cooperation is rarely necessary, DOC gracefully reverts to a standard CSMA/CA protocol. Our implementation of the custom DOC MAC and PHY is built on the Rice University Wireless Open-Access Research Platform (WARP). It operates in real-time without any offline processing, allowing for standalone operation and packet exchanges at timescales comparable to commercial IEEE 802.11 devices. This implementation of the DOC MAC/PHY system addresses real-world degradations like imperfections in synchronization and link-level coordination. Extensive experimental results demonstrate that our implementation delivers substantial improvement in end-to-end throughput over that of a non-cooperative link.