Existing work on multibeam joint precoding technique assumes the availability of perfect channel state information(CSI) at the satellite transmitter.Unfortunately

this assumption is not applicable to mobile satellite systems due to the long propagation delays

especially for the geostationary earth orbit(GEO) satellite systems.In order to solve the problem

this paper presents a multibeam cooperative transmission method based on partial CSI.Employing the shadowed-Rice fading channel model

a closed form expression is derived for the outage capacity and the optimal joint precoding algorithms are proposed assuming the availability of only partial CSI.Simulation results have shown substantial performance gain compared with conventional single beam based processing scheme.