Bit Stream Decorrelation in An Iterative Overloaded MIMO Receiver for Higher-Order QAMs

Abstract

This paper proposes techniques to improve the transmission performance of an iterative receiver for higher order quadrature amplitude modulations (QAMs) in overloaded MIMO systems. One of the proposed techniques, called applies a modulo function to demapping that transforms modulation signals into the bit sequence. Although the proposed demapping causes the performance degradation at first, the proposed demapping achieves better BER performance as the number of the iterations increases. The other of the proposed technique, called cyclic path switching changes parameters in the iteration loop of the receiver periodically. The performance of the proposed techniques is verified by computer simulation in a 6×2 overloaded MIMO channel. When the 64QAM is applied, the proposed techniques attain a gain about 1.5 dB at the BER of 10−5.