Combined asterism and sphere decoder for large asymmetric MIMO systems

The area of Multiple Input Multiple Output (MIMO) communications systems has received enormous attention recently as they can provide a roughly linear increase in data rate by using Multiple Transmit and Receive antennas. The optimal detection strategy for a MIMO receiver is to perform a Maximum-Likelihood (ML) search over all possible transmitted symbol combinations which has an exponential complexity when the constellation size of number of transmit antennas increase. Sphere and Asterism decoders are schemes that achieved ML performance for MIMO systems, but both have shortcomings in computational complexity, Sphere decoding when n(t) > n(r) and Asterism when n(t) < n(r). This paper combines Asterism and Sphere decoding for Asymmetric MIMO systems to reduce the overall computational complexity for any number of antennas.