Linear diversity combining techniques

Abstract

This paper provides analyses of three types of diversity combining systems in practical use. These are: selection diversity, maximal-ratio diversity, and equal-gain diversity systems. Quantitative measures of the relative performance (under realistic conditions) of the three systems are provided. The effects of various departures from ideal conditions, such as non-Rayleigh fading and partially coherent signal or noise voltages, are considered. Some discussion is also included of the relative merits of predetection and postdetection combining and of the problems in determining and using long-term distributions. The principal results are given in graphs and tables, useful in system design. It is seen that the simplest possible combiner, the equal-gain system, will generally yield performance essentially equivalent to the maximum obtainable from any quasilinear system. The principal application of the results is to diversity communication systems and the discussion is set in that context, but many of the results are also applicable to certain radar and navigation systems.

Multipath Interference Reduction In Wireless Radio Systems Using Two-Branch Selection Diversity

“…For example, with a multipath time of 3 μs (corresponding to a 1 km of added on-air travel for the last received impulse), there is a coherence bandwidth of about 330 kHz [1].…”

“…Having several receive sites increases the probability that one of the sites will receive the local signal in the presence of a distant, undesired one. Selective calling can eliminate users having to listen to the audio of distant signals even though the distant signals are within receive range of one or more receivers [1].…”

“…The subsequent derivation will employ a specific geometric model, that has been empirically verified to produce faithful expressions for the second-order spatial correlation coefficient across two receive-antennas, while coinciding with the well known formula in (1). Section I will define the geometric model of the fading channel.…”

“…A well-known example is power line communication. High-speed power line communication systems usually employ multi-carrier modulations to avoid the intersymbol interference that multipath propagation would cause [1].…”

“…Thus, the received signal will be expressed by where is the number of received impulses (equivalent to the number of electromagnetic paths, and possibly very large), is the time delay of the generic impulse, and represent the complex amplitude (i.e., magnitude and phase) of the generic received pulse. As a consequence, also represents the impulse response function of the equivalent multipath model [1].…”