1. Field of the Invention
This invention relates generally to a wireless communication system, and in particular to MIMO detection techniques.
2. Background
Multiple-Input-Multiple-Output, popularly known as MIMO, where multiple antennas are employed at both ends of the communication link, has recently emerged as a promising technology for providing spectral efficiencies far beyond those achieved by Single-Input-Single-Output (SISO) systems, where a single antenna is employed at both ends of the communication link.
Developing an algorithm they later named D-BLAST, researchers at Bell Labs demonstrated unprecedented spectral efficiencies on the order of 42 bits/s/Hz. A relatively less computationally intensive algorithm known as V-BLAST was proposed later. V-BLAST suffered in performance compared to D-BLAST mainly due to the self-generated error propagation problem that limited its performance.
Many solutions have been proposed since then that attempted to reconcile the performance of V-BLAST with that of the near-optimal performance of D-BLAST. Most of these solutions focused on mitigating the effects of the error propagation problem, but they did so by adding complexity to V-BLAST to the point where the added complexity made the new V-BLAST based solution unattractive for practical implementation.
V-BLAST (and its variants) focus mainly on maximizing the multiplexing gain (i.e. data rate) while most other space-time codes focus on maximizing diversity gain (i.e. reliability). The optimum solution seems to lie in a hybrid approach (See Conclusion, David Gesbert, Mansoor Shafi, and Da shan Shiu, From theory to practice: An overview of MIMO space-time coded wireless systems, IEEE Journal 21 (2003), no. 3, 281-302). So an optimal trade off is needed (optimal trade off can be measured according to Lizhong Zheng, Diversity and Multiplexing: A Fundamental Tradeoff in Multiple-Antenna Channels, IEEE Transactions on Information Theory, Vol. 49, No. 5, (2003)).
V-BLAST (and its variants) and other space-time codes do not account for channel correlation that normally exists in practice. Channel correlation tends to heavily degrade the performance of these systems.
So complexity reduction, correlation reduction, and diversity-multiplexing trade off are still an open problem in MIMO communications.
Therefore, there is a need for improved systems, apparatus, and techniques for signal detection techniques n a MIMO communication system.