The Sphere Decoding Algorithm applied to Space-Time Block Codes

The use of digital wireless communication systems has become more and more common during recent years. A multiple-input-multiple-output (MIMO) system using Space-Time Coding techniques can be implemented to enhance the capacity of a wireless link. The optimal decoder is based on the maximum likelihood principle. But as the number of the antennas in the system and the data rates increase, the maximum likelihood decoder becomes too complex to use. Examples of less complex decoding techniques used are zero-forcing and MMSE, as well as V-BLAST have been implemented at the price of reduced performance at the receiver. In this work, we investigate a new type of decoding algorithm called sphere decoding. As will be apparent from the development to follow, this algorithm delivers near optimal performance with reasonably low complexity. We have investigated the performance of the sphere decoding algorithm. As it has shown in the computer simulations, the decoder based on the sphere decoding algorithm has almost the same performance of a maximum likelihood decoder with much lower complexity. Further simulations of the sphere decoding algorithms has shown, with the channel estimation error at the receiver, the decoder with the sphere decoding algorithm still has the same performance as in a ML decoder without increase the decoding complexity.