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This paper reports a statistical relationship between 1 s averaged rain attenuation (A, in decibels) and standard deviation (sigma, in decibels) of simultaneous tropospheric scintillation in 1 s intervals, derived from high resolution (50 samples/s) experimental 19.77 GHz attenuation time series recorded at Spino d'Adda (45.4°N) in a 30.6° slant path to satellite Olympus during an observation time of approximately 1 year. During rain the relationship between scintillation and rain attenuation, suitably separated, can be fit by the power law formula derivable from a turbulent thin layer model

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INTRODUCTIONCurrent high-throughput satellite (HTS) systems for broadbanddistributed user access are designed following two main concepts: C The use of Ka band radio frequency (RF) links both for the forward and for the return link; this choice is due to the congestion of lower frequency bands and to the relatively large bandwidth available in the Ka band. Moreover, the RF technology in the Ka band is mature [1], [2].C The use of multispot coverage: this technique is largely applied to increase the system throughput through frequency reuse and system reconfigurability [2], [3].HTS systems are dimensioned to support an aggregated total capacity (considering both forward and return links) of a tenth of a gigabit per second over a coverage area as large as Europe, with a single spot capacity of hundreds of megabits per second [3].As a matter of fact, HTSs still offer much less bandwidth per user with respect to the terrestrial broadband networks. To achieve very high throughput towards "terabit connectivity," bandwidth efficient modulation schemes have to be used [4], [5]. However, because there is a trade-off between bandwidth efficiency and power efficiency in modulation schemes, high bandwidth efficiency requires more transmission power that is a limited resource in satellite systems.Therefore, an important breakthrough is needed in terms of bandwidth availability. The Q/V band (40-50 GHz) seems to offer very promising perspectives, being unused for commercial systems and offering a large part of the spectrum allocated for satellite services [1]. In this frame, the medium-term HTS system architecture is based on the use of a Ka-band user link to maintain the user terminal compatibility with the current system and a Q/V band feeder link [4]- [7].This solution is particularly attractive for the following reasons:C The Q/V band spectrum allocated for fixed satellite service is very large, about 5 GHz of near-continuous bandwidth both for uplink and downlink.C The whole Ka-band spectrum (that is currently allocated both for feeder and user links of the HTS systems) will be available for user link, increasing the bandwidth allocated to the user segment. This will require a rethinking of International Telecommunication Union frequency allocation and a strong frequency coordination activity.It is well-known that the atmospheric propagation impairments at extremely high frequency (EHF) bands (30-300 GHz) are severe, not only when rain events occur but also in the presence of clouds. The EHF electromagnetic radiation that propagates through the atmosphere is subject to absorption, scattering, depolarization, and fast fluctuations of amplitude and phase (scintillation) that have to be carefully investigated. Moreover, some mitigation techniques have to be analyzed and properly tuned to realize an efficient transmission. To counteract rain fading effects, high static link margins can be considered to ensure a minimum service outage duration. However, setting large link margins is in contrast with technology limitations of s...

A large database of radiosoundings, brightness temperatures, and satellite beacon data was used to verify the ability of radiometers in estimating the attenuation in nonprecipitating conditions at millimeter wavelengths. The mass absorption models proposed by Liebe and Rosenkranz have been used coupled with the Helsinki University of Technology (TKK) cloud-detection model to derive coefficients for the calculation of the attenuation due to integrated water vapor and liquid water contents. Comparison of predicted and measured attenuation cumulative distribution functions in the 20-50-GHz band confirms radiometers as a unique tool for retrieving attenuation in nonrainy condition and shows the very good performance of the TKK model for propagation applications.