Balancing for Interference-Limited Multi-User Satellite Communications

The challenges in satellite communication for serving many (mobile) terminals simultaneously in higher carrier frequencies with reuse one are due to the interference and the various fading sources. Thus, the imposed downlink beamforming for the interference management has to account also for the link reliability. This chapter details the forward-link model of a modern multi-spotbeam satellite with generalized transmit power limitations, that also includes the basic rain-fading and scattering that is visible for the transmission to mobile terminals. In particular, the channel model consists of an additive and a multiplicative random channel error. Two kinds of rate balancing beamformer design strategies are studied then the satellite has statistical information about the fading channels, namely, the epsilon-outage rate balancing optimization and the average rate balancing optimization. Each of these robust approaches is detailed for fading that leads to a rank-one channel covariance or (at worst) a full-rank channel covariance due to scattering. While the epsilon-outage rate for the rank-one channel covariance can straightforwardly be rewritten into a standard rate balancing problem, but with increased noise, this is impossible for full-rank channel covariances. Then, the idea is to split the outage probability and the optimization into two parts for the multiplicative and the additive channel errors. An inner problem takes conservatively the additive channel errors into account, assuming prior information of the multiplicative errors, and the outer optimization adjusts this kind of information for the inner problem. For the average rate balancing optimization, already rank-one channel fading leads to unattractive rate expressions for a direct optimization. However, rate bounds with a standard logarithmic structure and an adapted effective noise power (and small offsets) are almost tight. This changes for a (worst-case) scattering that leads to full-rank channel covariance matrices. Then, a mean square error lower bound for the rate is sequentially optimized instead.     «

The challenges in satellite communication for serving many (mobile) terminals simultaneously in higher carrier frequencies with reuse one are due to the interference and the various fading sources. Thus, the imposed downlink beamforming for the interference management has to account also for the link reliability. This chapter details the forward-link model of a modern multi-spotbeam satellite with generalized transmit power limitations, that also includes the basic rain-fading and scattering tha...     »