Robust precoding design for multibeam downlink satellite channel with phase uncertainty

Abstract

In this work, we study the design of a precoder on the user downlink of a multibeam satellite channel. The variations in channel due to phase noise introduced by on-board oscillators and the long round trip delay result in outdated channel information at the transmitter. The phase uncertainty is modelled and a robust design framework is formulated based on availability and power constraints. The optimization problem is cast into the convex paradigm after approximations and the benefits of the resulting precoder are highlighted.

Precoding design and user selection for multibeam satellite channels

“…We consider a typical Ka-band multibeam GEO satellite system with K beams [2], [6] employing a full frequency reuse where all the beams operate at the same frequency. We further assume a single feed per beam scenario with K antenna feeds at the satellite used to form the K fixed beams.…”

“…Ideal feeder link and lossless processing on-board the satellite are assumed [6]. Then, the received SINR at i th user takes the form,…”

“…In particular, the two hop propagation delay in the GEO orbit is about 250 milliseconds [4] compared to the few milliseconds in cellular systems. In the satellite channel, it was observed that the amplitude of the channel changes slowly compared to the RTD [5], [6]. However, the variations in the phase component of the channel are rapid due to phase noise contribution from the payload and the time dependent channel variations [4], [6].…”

“…In the satellite channel, it was observed that the amplitude of the channel changes slowly compared to the RTD [5], [6]. However, the variations in the phase component of the channel are rapid due to phase noise contribution from the payload and the time dependent channel variations [4], [6]. This time varying nature of the channel coupled with a high RTD result in outdated CSIT, or more specifically outdated channel phase [6].…”

“…A robust precoding design for a channel with outdated phase is described in [6] based on probabilistic approach. Therein, the precoder is designed to guarantee the desired quality of service (QoS) goals based on the outage probability for all users.…”