A new reduced-complexity sphere decoder with true lattice-boundary-awareness for multi-antenna systems

Maximum-likelihood (ML) detection in a multi-antenna system can be cast as a problem of closest point search in a finite lattice, which can then be efficiently solved by a sphere decoder. Although the state-of-art sphere decoding algorithms proposed in [5] have considered the finiteness of the lattice, many points outside the finte lattice are still tested, resulting in much unnecessary computation. In this paper we address this problem by incorporating true lattice-boundary-awareness such that testing on any point outside the finite lattice is completely avoided. This new lattice-boundary-aware sphere decoder offers two important advantages: (i) Compared to the sphere decoder proposed in [5], it achieves up to 32% reudction in the number of multiplications and up to 39% in the number of additions; (ii) The complexity reduction tends to increase as SNR decreases. The proposed approach can thus significantly relax the requirements on hardware implementation of the sphere decoder.