Randomized Spatial Multiplexing for Distributed Cooperative Communications

In this paper, we design a simple and robust cooperation scheme that allows multiple relay stations, with only one antenna each, multiplex transmissions to a BS with multiple antennas. The data transmission is over two hops, where the source first sends information to relaying nodes. In the second hop, the data packet is split into multiple parallel streams in a deterministic manner. Each participating relaying node transmits a random and independent linear combination of the signal streams that would have been transmitted by all the elements of a multi-antenna system. This random processing eliminates the need to index and allocate a code for each participating relay, and thus makes the system more efficient and robust. We use the information-theoretic capacity as an upper bound for what can be achieved using this scheme. Since this scheme can achieve higher spatial multiplexing gain for the relay-destination link, it greatly improves the effective data rate for stations at the edge of the cell. This scheme requires multiple antennas at the receiver and is therefore more suitable for uplink transmission in wireless LANs and cellular networks.