SIlicon Complexity for Maximum Likelihood MIMO Detection Using Spectral Decoding

This paper presents a silicon complexity analysis of ML search techniques for MIMO as applied to the HDSPA extension of UMTS. For MIMO constellations of 4x4 QPSK or lower, it is possible to perform an exhaustive ML search in today's silicon technologies. When the search complexity exceeds technology limits for high complexity MIMO constellations, it is possible to apply spherical decoding techniques to achieve near-ML performance. The paper presents an architecture for a 4x4 16QAM MIMO spherical decocder that achieves 38.8 Mb/s over a 5 MHz channel using only approximately 10 mm2 in a 0.18mum CMOS process.