Bit-interleaved space-frequency coded modulation for orthogonal frequency-division multiplexing systems.

摘要

We consider space-time coding design in frequency-selective fading channels. We present an orthogonal frequency-division multiplexing (OFDM) system with bit-interleaved space-frequency coded modulation (BI-SFCM) for frequency-selective fading channels employing multiple transmit and receive antennas. OFDM is used to transform a frequency selective fading channel into multiple flat fading channels, and space-frequency trellis coding combined with bit-interleaved coded modulation (BICM) is used to exploit space and frequency diversity.; The proposed scheme is an efficient method to employ multiple transmit antennas to increase the data rate and at the same time improve the performance by means of increased diversity obtained with BICM and multiple receive antennas. We develop an analytical performance evaluation framework for the proposed BI-SFCM approach based on applying a union bound technique to calculate the bit-error probability. This analysis shows that with BI-SFCM it is possible to achieve a diversity order given by the product of the number of receive antennas and minimum Hamming distance of the applied code, and the data rate increases linearly with the number of transmit antennas.; We also propose a linear block precoding method to further explore the diversity of the OFDM system. We suggest the use of lattice and fast Fourier transform (FFT) based matrices for linearly precoding blocks of transmit signals for the goal of increasing the diversity gain.; An efficient sphere decoding algorithm is also developed, for reducing the decoding complexity of the proposed schemes. We show that the increase in the decoding complexity caused by employing BI-SFCM can be limited by the use of the pro posed sphere decoding algorithm, without incurring a significant performance degradation.; We further improve the coding performance of BI-SFCM by employing iterative decoding between the outer convolutional code and the inner space-frequency modulation. Analytical bounds and simulations are used to evaluate the performance of BI-SFCM with iterative decoding (BI-SFCM-ID). We show that BI-SFCM-ID can achieve performance that is quite close to capacity limits. We also present an efficient sphere decoding algorithm for reducing the decoding complexity of BI-SFCM-ID.