Technologies Lecture 17 & 18 : Diversity Combining Techniques

Diversity exploits the random nature of radio propagation by finding multiple independent (or at least uncorrelated) signal paths for comunication. Here we examine the microscopic diversity techniques to deal with small-scale fading characterized by deep and rapid amplitude fluctuations which occurs as the mobile moves over distances of just a few wavelengthes. There are four major diversity combining techniques, i.e., selection combining (SC), maximum ratio combining (MRC), equal gain combining (EGC), and switched combining. Section 2 discribes each diversity combining technique, and gives pdf (probability density function), cdf (cumulative density function), and the mean value of the resulting SNR of each technique. The advantages and disadvantages of each technique are discussed as well. Section 3 shows the effects of correlated signals and correlated noise to the diversity comibing techniques. In Section 4, we investigate the bit error performance of digital diversity combining system.