Layered encoding for low complexity detection of high-order modulations in MIMO channels

Mobile receiver complexity persists as one of the key areas of concern in the adoption of MIMO technologies for systems such as high-speed downlink packet access (HSDPA) in UMTS. This is particularly the case for high-order modulation schemes such as 16-QAM and 64-QAM, where optimum a posteriori probability (APP) detection becomes too complex, and sub-optimal detection based on serial or parallel interference cancellation performs poorly. The above issues are successfully tackled by introducing a judicious layered encoding process at the transmitter, which once appropriately exploited at the receiver, allows considerable reductions in computational complexity in addition to improvements in performance.