Effect of Imperfect Channel Estimation on the Performance of Cognitive Satellite Terrestrial Networks

The incorporation of cognitive radio (CR) techniques into satellite communication systems, has been considered as one of the most promising approaches to address the spectrum scarcity, which constitutes an advanced infrastructure known as cognitive satellite terrestrial network (CSTN). Due to the estimation error or feedback delay, perfect channel state information (CSI) of satellite and/or terrestrial links in CSTNs are normally unavailable. This paper investigates the effect of imperfect CSI on the performance of CSTN, where a secondary satellite network coexists with a primary terrestrial network by employing the underlay cognitive mechanism according to which the satellite user is allowed to access the licensed spectrum without deteriorating the operation of terrestrial user. Specifically, we derive the analytical expressions for the outage probability and ergodic capacity of the cognitive network, which provides an efficient approach to jointly evaluate the impacts of imperfect channel estimations for different links on the performance of considered network. Moreover, simple asymptotic outage probability formula in the high signal-to-noise ratio regime is presented to reveal the diversity order and coding gain of the CSTNs. Finally, numerical results are provided to confirm the validity of the theoretical analysis, as well as quantitatively analyze the effects of various system parameters on the performance of the CSTNs with CSI imperfection.