Amplify-and-Forward Scheme in Cooperative Spatial Multiplexing

We investigate and propose a new amplify-and-forward cooperative spatial multiplexing scheme in which the transmitter (source), equipped with a single antenna, forms virtual antenna array from a collection of distributed single-antenna wireless terminals, and broadcasts identical signal to those terminals (relays). Each relay amplifies and forwards different portion of the received signal at a reduced data rate to the receiver (destination). The receiver, equipped with multiple antennas, nulls and cancels the interference from different relays in order of the signal-to-noise ratio, and detects the original signal transmitted from the source. The combination of transmitter, relays, and receiver forms a virtual MIMO system in single-antenna wireless terminals environment. Unlike the conventional spatial multiplexing scheme, the proposed scheme does not require multiple antennas at the transmitter side, making it to be particularly useful for uplink (mobile to base-station) data transmissions. It is shown that the performance of the proposed system approaches and, in some cases, surpasses that of the conventional MIMO spatial multiplexing scheme.