Abstract
In this paper, we review the work of the gateway diversity schemes for Q/V band feeder links for a future HTS system. As each gateway will carry very high capacity, it is essential to ensure very high availabilities for the feeder links, typically greater than 99.9%. In order to do so, spatial diversity is required, since Adaptive Coding and Modulation (ACM) and Uplink Power Control (UPC) are unable to cope with the fade dynamics encountered at these high frequency bands. In an effort to reduce the total number of gateways in the system and to result in a more cost effective system, the concept of Smart gateways has emerged. We first review different architectures implementations and highlight their similarities and differences. We then outline the technological challenges and the issues that the envisaged solutions should consider during the design process. Finally we give views on a technology roadmap to meet these challenges.