Channel adaptive output back-off setting of non-linear power amplifiers for high throughput multi-spot beam satellite systems

In order to increase the satellite capacity for high throughput systems, the feeder link frequencies are gradually moved to higher bands, such as the Q/V-bands, where more bandwidth is available. Therefore, more spectrum shall be available for the user links at lower frequencies, such as in Ka-band. However, the rain attenuation on the feeder links becomes a limiting issue because of the higher frequencies. It is thus important to find link adaptation, or in other words channel adaptive techniques that can overcome this issue, such as smart gateway diversity or adaptive coding and modulation. This paper, however, introduces and describes a novel patented technique: channel adaptive output back-off (OBO) setting. This technique can be applied on any terrestrial or satellite link, in which a non-linear power amplifier is operated in multicarrier mode and the transmission channel experiences time varying attenuation. As a consequence, this technique can be applied, for example, both on the feeder uplink and on the feeder downlink of multi-spot beam satellite networks. However, due to several reasons, the present paper analyzes its performance only on the feeder downlink. According to the performed analysis, channel adaptive OBO setting can provide around 4.5 dB signal-to-noise and interference ratio improvement in case of deep rain fading compared with the conventional fixed OBO operation. This improvement reduces the outage by around 17% on the end-to-end return link. As a consequence, the feeder downlink and the total return link become much more robust against deep rain fading. Copyright © 2015 John Wiley & Sons, Ltd