Performance of coded multicarrier multiple transmit antenna DS-CDMA systems in the presence of power amplifier nonlinearity

Abstract

While a multicarrier approach of achieving frequency diversity performs well in the presence of jamming, it suffers from the effects of intermodulation distortion (IMD) due to power amplifier (PA) nonlinearity. On the other hand, transmit diversity using multiple transmit antennas has the benefit of no IMD effects, but suffers from a larger performance degradation due to jamming compared to the multicarrier approach. Hence, hybrid diversity schemes which use both multicarrier as well as multiple transmit antennas are of interest. Techniques to suppress IMD effects in such hybrid diversity schemes are important. In this paper, we propose a minimum mean square error (MMSE) receiver to suppress the intermodulation distortion in a coded multicarrier multiple transmit antenna (P transmit antennas) DS-CDMA system with M subcarriers on each transmit antenna. The system uses rate-1/M convolutional coding, interleaving and space-time coding. We compare the performance of a (M = 4, P = 2) scheme and a (M = 2, P = 4) scheme, both having the same diversity order. We show that the proposed MMSE receiver effectively suppresses the IMD effects, thus enabling us to retain better antijamming capability without much loss in performance due to IMD effects.