An overview of soft-output sphere decoders with constant throughput

This paper represents an overview of the main sphere decoders used in MIMO (Multiple Input Multiple Output) spatial multiplexing communication systems. The family of sphere decoders addressed in this paper exhibits fixed throughput, regardless of the radio channel conditions. The algorithms are compared with respect to their complexity and performances when used with a soft Viterbi channel decoder. The paper concludes with the criteria for choosing the best algorithms in a given configuration and for specific modulation scheme.