Capacity of Satellite Communication Systems Under Different Adaptive Transmission Schemes

Satellite systems are widely used in applications such as broadcasting, navigation, emergency services, etc., because of some unique advantages such as providing service over wide coverage area, especially in regions where terrestrial communication fails. In this paper, channel capacity of satellite system subjected to three adaptive transmission policies namely, optimal rate adaptation with constant transmit power (ORA), optimal simultaneous power and rate adaptation (OPRA) and channel inversion with fixed rate (TIFR) is studied. Exact closed-form expressions of the Shannon capacity under these schemes are derived. The channel fading of the system is modelled using Shadowed Rician (SR) distribution. The derived expressions are applicable to integer as well as non integer valued severity/Nakagami-m parameter of the SR distribution. In addition to this, the effect of shadowing severity parameter on the capacity of adaptive schemes is also investigated. Numerical results reveal that OPRA scheme results in more capacity gain than the other two. On the other hand, TIFR scheme suffer a large outage probability which causes large capacity penalty as compared to ORA and OPRA schemes. Furthermore, increase in shadowing severity degrades the capacity of the satellite channel.