Design of an on-board beam generation process for the forward link of a multi-beam broadband satellite system

Next generation high throughput satellite systems are expected to rely on the deployment of a high number of beams in the coverage area. To this end, the payload is equipped with an array fed reflector antenna whose elements/feeds are more than the number of users. Under this context, as the number of beam increases the ground and space units must employ an extensive communication effort on the feeder link (i.e. the link between gateway and satellite) to exchange all of the feed signals yet maintaining a low processing responsibility to the payload. Since the feeder link spectral resources are scarce, it is desirable to use an on-board beam generation process which leads to a significant feeder link bandwidth reduction. In this context, a space/ground processing (i.e. both the gateway and the satellite digitally process the transmitted/received data) must be employed. This implies to implement an on-board beam generation process and, when a full frequency pattern among beams is used, on-ground linear processing techniques are required in order to reduce inter user/beam interference. In this paper, we restrict ourselves to design an on-board beam generation process in the forward link of a space/ground architecture satellite system. Moreover, we focus on linear minimum mean square error precoding strategy at a single gateway architecture. In addition, in order to more reduce payload complexity the beam generation process is assumed to be non channel adaptive (fixed) even if the user link (i.e. the link between satellite and users) channel appears as a random variable. This is done by means of considering robust optimization approach. Then, our design is evaluated both analytically and numerically, and it outperforms the current beam generation process. The provided simulation results quantify the performance gain obtained by our method.