Satellite diversity system emulator

Abstract

Current satellite telecommunication systems are facing growing demand, in particular for broadband markets. In order to reach higher data rate and minimize the cost per Mbps, upcoming VHTS systems are targeting Terabit capacity. One of the most promising solution is to dedicate the whole Ka band to the user links to maximize the user link capacity whereas the feeder links operate in Q/V bands. However, the use of these higher frequencies (in the Q/V bands) raises new challenges, because of the increased sensitivity of these bands to meteorological events that may affect gateways link budget, making them unable to handle any traffic during a rain event. A simple solution to this shortcoming for ensuring constant service to users is to add additional gateways to the system and perform a handover to a redundancy gateway when a nominal gateway faces too strong fading 3,4. For example, a pan-european system with a dozen of operational gateways and a few redundancy gateways would be economically viable: the additional cost of the redundancy gateway is not offset by the benefits of increased system availability. Different design choices to realize diversity are possible 5: this work studies in particular geographical diversity, or (n+p) diversity. This (n+p) diversity scheme provides extremely high availability with very few redundant gateways. However, the impacts on services has still to be evaluated. This paper presents a diversity emulation test-bed developed to experiment different types of gateway handover scenarios to measure their impact on user’s experience. This emulator has been developed by IRT Saint-Exupéry in the framework of the ALBS project (Advanced Link for Broadband Satellite). The emulator is able to simulate both ground network and satellite links, up to the user’s terminals. It is designed to be representative of the network transit and switching losses and delays, as well as the satellite onboard switch behavior. The emulator is used to investigate the influence of the effects that switching mechanisms can have on the ongoing communications. It will also allow to investigate design optimization and provide recommendations to handle these ongoing communication during the gateway handover.