Effects of diversity combining, coding and equalization on digital microcellular mobile communication systems

Abstract

The effects of diversity combining, coding, and equalization on the performance of digital microcellular mobile communication systems, operating over frequency-selective fading channels, are studied using computer simulations. The presence of co-channel interference and additive white Gaussian noise is assumed. The multiple-access channel is statistically modelled by Rician distributed plus lognormally shadowed desired signal and several uncorrelated Rayleigh plus lognormally shadowed interfering signals, propagating according to dual path loss law with a turning point. The modulation schemes considered are BPSK, and DPSK. The channel is modeled by two beams with a relative delay between them. The performance is determined in terms of bit error rate (BER), and spectrum efficiency. It is shown from the computer simulations done on the system that with dual diversity combining and BPSK modulation the irreducible bit error rate (IBER), due to co-channel interference and intersymbol interference (ISI), is reduced from 3.0 x 10⁻³ to 1.35 x 10⁻⁴. Also, with linear adaptive equalization and BPSK modulation, the IBER is reduced to 8.0 x 10⁻⁴. The use of Golay (23, 12) code with BPSK modulation enhances the performance of the system by 23.8 dB coding gain at 3.0 x 10⁻³ BER.