A new approach for fast generalized sphere decoding in MIMO Systems

A new generalized sphere decoder (GSD), called a double-layer sphere decoder (DLSD), is proposed for under-determined MIMO systems with fewer receive antennas N than transmit antennas M. The proposed algorithm is significantly faster than those introduced in [1] and [2]. The basic idea is to partition the transmitted signal vector into two subvectors with M - N + 1 and N - 1 elements. After some simple transformations, we can use an outer layer sphere decoder (SD) to choose proper subvectors of length M - N + 1 and then use an inner layer SD to decide the other subvector of length N - 1, thus the whole transmitted signal vector is obtained. Simulation results show that DLSD has far less complexity than the existing GSDs.