EFFECT OF CORRELATION IN DIVERSITY SYSTEMS WITH RAYLEIGH FADING, SHADOWING, AND POWER CAPTURE

With the growth of wireless personal communications networks and wirel ess local area networks (WLAN's), the need for increased reliability o f the radio link has become evident. The use of diversity techniques, suck as dual receiving antennas, helps mitigate the effect of multipat h fading in both the in-building and land mobile radio environments. A significant issue in the design of such systems is the degree to whic h correlation between the two or more diversity signals can he tolerat ed. In this paper, we consider the use of diversity techniques in radi o systems that are subject to correlation, Rayleigh fading, lognormal shadowing, and the radio capture effect. In the presence of two simult aneously transmitting stations, the throughput, conditioned on the loc al-mean power, is determined exactly for the case of a dual diversity receiving station. The insight gained from the two-station analysis is used to develop an accurate approximation for cases with more than tw o stations. The degree to which correlation can be tolerated without s ignificant performance loss relative to the case of independent divers ity signals is quantified, as are the effects of different system para meters (i.e., the capture ratio, power roll-off coefficient, and the a mount of shadowing). Furthermore, the relationship between the envelop e and power correlation coefficients is presented. An application of t he capture results to the slotted ALOHA protocol is also included.