Power envelope reduction in MIMO-OFDM with block diagonalization by using fuzzy inference systems

Users of wireless communications nowadays request everyday more and more data rate. In order to provide such as high transmission rates, multiple antennas in transmission and reception (MIMO) are used combined with the high efficient transmission scheme of OFDM (orthogonal frequency division multiplexing). Besides, enhanced systems must be designed to accomplish with the demand. One of the solutions to reduce interferences in wireless mobile channels is the block diagonalization (BD). However, a MIMO-OFDM-BD signal exhibits the drawbacks of OFDM counterparts in terms of power envelope fluctuations which degrades the signal if high efficiency nonlinear High Power Amplifiers (HPA) are used. Thus, in this paper, a novel technique for reducing the power envelope fluctuations based on Fuzzy logic is presented and analized. The proposal obtains the same reduction as the best MIMO-OFDM technique denoted as ACE (Active Constellation Extension) but with much less complexity over MIMO-OFDM-BD signals. More than 2 dB of reduction can be easily obtained by using our proposal.