This paper investigates a random-interleaver-based approach to space-time coding. The basic principle is to employ a good forward error correction (FEC) code and transmit randomly interleaved codewords over an antenna array. A low-cost estimation technique is considered. The complexity involved grows only linearly with the number of transmit antennas. Near-capacity performance can be achieved with moderate complexity.

While a multicarrier approach of achieving frequency diversity performs well in the presence of partial-band interference, 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 can suffer from a larger performance degradation due to partial-band interference (e.g., jamming or narrowband signals in a overlay system) 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 and evaluate the performance of 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, for both BPSK and QPSK modulation. 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 to retain better antijamming capability without much loss in performance due to IMD effects.