Time diversity analysis based on predicted rain attenuation at Ka and V bands using Synthetic Storm Technique

Abstract

Future satellite communication services are moving towards higher frequency Ka and V-bands. The use of these frequency bands is limited by different propagation impairments in atmosphere. Rain fade is the main challenge to design reliable earth to satellite communication links above 10 GHz. The problem becomes severe in tropical regions because of high rainfall occurs most of the time in a year. Time diversity technique is one of the potential mitigation techniques because this technique is cost effective and efficient mitigation techniques to overcome the attenuation due to rain (Del Pino et al, 2005). For time diversity analysis, measured real-time rain attenuation data are needed to design. But the problem is in the higher frequency bands like Ka and V bands, those data are not available. Hence, Synthetic Storm Technique (SST) can be utilized because it can convert the measured real-time rain rate data to rain attenuation data. This thesis presents analysis of one year measured rain rate data with 1-minute integration time which has been collected at IIUM, Kuala Lumpur campus. One year measured rain rate data are converted into equivalent attenuation data using Synthetic Storm Technique (SST). The Cumulative Distribution function of all converted rain attenuation is calculated without time delay and with time delays of 1, 3, 5, 10, 20 and 30 minutes respectively for Ku, Ka and V-bands. Time diversity gain is also analyzed and found that gain is higher with the increasing of time delay. It has been also observed that improvement is higher at a lower percentage of outages. The gain at 0.01% are found 4.7 and 27.8 dB for Ku-band, 6.8 and 58.7dB for Ka-band and 10.5 and 94.2 dB for V-band with the time delays for 1 and 30 min respectively. For comparison, the gains predicted by Matricciani model are compared with SST predictions for Ku, Ka and V-bands for all percentages of outages and for 1, 3, 5, 10, 20 and 30 minutes delays. Since the analysis is done based on measurement in tropical region, it is very significant that Matricciani model gain is found comparatively much higher than SST predicted rain attenuation gain in all the frequency bands. For the purpose of validation, SST predicted gain has been compared with the available Kuala Lumpur measurement at Ku-band. After comparison, it has been found that the SST predicted gain is much closer to measured one than gain predicted by the Matricciani model. Hence, a model can be proposed to predict the time diversity gain using measured rain rate time series and Synthetic Storm Technique (SST) with a correction which depends on frequency and time delay. For Ku-band, the correction function is developed and presented. For any other bands, the functions can be developed using available measured gains.