Rain Outage Performance of Tandem and Path Diversity 18-GHz Short Hop Radio Systems

Abstract

The performance with respect to rain outage time of dual path diversity and non‐path diversity (tandem) arrangements for 18‐GHz short hop radio systems is computed and compared. The analysis is based on two extrapolations of R. A. Semplak's1 three‐year average of the measured probability distributions for rain attenuation at 18.5 GHz on a 6.4‐km hop in New Jersey. The effects of merge hops and joint fading between hops in the diversity system, dependence of the rain attenuation distribution on hop length, and uncertainty in the tail of the distribution are included. The results show that (i) the performance of tandem systems relative to diversity systems increases as the system length increases, (ii) the difference in the number of repeaters per unit length required for short and long tandem systems is small, (iii) the performance of the diversity system is strongly dependent on the amount of joint fading between parallel paths, and (iv) the performance of the tandem system is strongly dependent on the tail of the attenuation distribution. Neither of the latter two factors is known from rain attenuation measurements, but if the joint attenuation probabilities are sufficiently high, then diversity shows no advantage over tandem for either of the assumed extrapolations. The uncertainty in the tail of the attenuation distribution and the sensitivity of the tandem system performance to it emphasize the need for reliable attenuation measurements out to a probability of about 10−7.

Rain outage performance of tandem and route diversity systems at 11 GHz1

“…A similar comparison has been carried out by Osborne [1971] for 18 GHz systems, but, due to insufficient information about attenuation statistics, his conclusions are far from definitive. In this work, rain attenuation statistics obtained by radar observations [Dru [uca, 1974a] are used, these statistics being such that more definitive conclusions can be drawn.…”

“…Because of the role played by the tails of the distributions in the calculation of'system performance, the way in which the tails are described is important. Osborne [1971] proportionally to path length. Therefore, the probability distribution curves for longer paths will be parallel straight lines on a log scale.…”

11-GHz Radio: Nationwide Long-Term Rain Rate Statistics and Empirical Calculation of 11-GHz Microwave Rain Attenuation

“…In Ref. 39, a two-parameter empirical formula was shown to describe this nonlinear behavior. A single parameter variation also provides satis- …”

Outage performance analysis of route diversity systems of cellular structure

“…The outage performance of digital microwave systems operating at frequencies above 10 GHz is mainly affected by rain. Route diversity systems as an alternative way to the conventional tandem systems have been considered as one of the available means for reducing the rain outage time or equivalently constructing an economical circuit [Drufuca and Torlaschi, 1977;Osborne, 1971; $asam and Nagamune, 1983]. In this vein, some models dealing with the analysis of the outage performance of a route diversity system have also.…”