Non-Linear Companding Transform aided MIMO-OFDM Systems

Abstract

In this paper a new non-linear companding transform (NCT) technique based on inverse hyperbolic cosine function is proposed and implemented along with new Intercarrier interference reduction technique to improve the performance of Multi Input and Multi Output Orthogonal Frequency Division Multiplexing (MIMO-OFDM) system in terms of Peak-to-Average Power Ratio (PAPR) and Inter Carrier Interference (ICI). An effective trade-off between the PAPR and Bit Error Rate (BER) performance is achieved by introducing an inflection point and variable companding parameters in the companding function, such that it enables more design flexibility and freedom in companding form. As per theoretical study, a desired PAPR threshold can be achieved by proposed technique, since it introduces the companding distortion as small as possible with appropriate selection of the companding parameters. And new ICI cancellation scheme maintains orthogonality among subcarriers of OFDM symbol, since it decreases the Carrier to Interference Ratio (CIR). The analytical expressions regarding the achievable PAPR reduction transform gain G, signal attenuation factor and CIR expression are derived. Simulation results demonstrate this combination together substantially improves performance of the MIMO-OFDM system. Keywords: MIMO-OFDM, PAPR, ICI, non-linear companding transform (NCT), CIR, high power amplifiers (HPA).