Approaching MIMO channel capacity with soft detection based on hard sphere decoding

• Published in: IEEE transactions on communications Vol. 54; no. 4; pp. 587 - 590
• Main Authors: Renqiu Wang, Giannakis, G.B.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.04.2006; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Amplitude estimation; Antennas; Applied sciences; Channel capacity; Coding, codes; Decoding; Demodulation; Exact sciences and technology; Information, signal and communications theory; Interference; MIMO; Modulation, demodulation; Multi-input multi-output (MIMO) detection; Phase estimation; Phase shift keying; Quadrature amplitude modulation; Radiocommunications; Signal and communications theory; soft decoding; sphere decoding; Systems, networks and services of telecommunications; Telecommunications; Telecommunications and information theory; Transmission and modulation (techniques and equipments); Transmitters; turbo decoding; Performance evaluation; Space-time codes; Quadrature amplitude modulation; Noise reduction; Signal estimation; Transmitter; Optimal detection; Binary code; sphere decoding; turbo decoding; Multilevel system; Antenna; MIMO system; Multiple access; Channel capacity; Multi-input multi-output (MIMO) detection; Turbo code; Decoding; Signalling; Algorithm; Quadrature phase shift keying; Interference suppression; Simulation; soft decoding; Demodulation
• ISSN: 0090-6778; 1558-0857
• DOI: 10.1109/TCOMM.2006.873064

Hard sphere decoding (HSD) has well-appreciated merits for near-optimal demodulation of multiuser, block single-antenna or multi-antenna transmissions over multi-input multi-output (MIMO) channels. At increased complexity, a soft version of sphere decoding (SD), so-termed list SD (LSD), has been recently applied to coded layered space-time (LST) systems enabling them to approach the capacity of MIMO channels. By introducing a novel bit-level multi-stream coded LST transmitter along with a soft-to-hard conversion at the decoder, we show how to achieve the near-capacity performance of LSD, and even outperform it as the size of the block to be decoded (M) increases. Specifically, for binary real LST codes, we develop exact max-log-based SD schemes with M + 1 HSD steps, and an approximate alternative with only one HSD step to trade off performance for average complexity. These schemes apply directly to the real and imaginary parts of quaternary phase-shift keying signaling, and also to quadrature amplitude modulation signaling after incorporating an appropriate interference estimation and cancellation module. We corroborate our near-optimal soft detection (SoD) algorithms based on HSD (SoD-HSD) with simulations.