Green RF/FSO Communications in Cognitive Relay-Based Space Information Networks for Maritime Surveillance

In this paper, we provide an overview of a space-based network for the maritime surveillance information sharing and evaluate the coverage, the throughput and the real- time reception capacity of the presented systems. The focus is on the feeder link of a multi-hop geostationary satellite system. We propose a cognitive relay-based architecture for the inter-satellite and satellite-to-ground communication with a multi-band spectrum sensing operating on both free-space optical (FSO) and radio frequency (RF) bands. Furthermore, modeling the spectrum sensing energy as a Gamma distribution we derive the formula of the network energy consumption in presence of multipath fading and considering two different data relay schemes: amplify-and-forward (AF) and decode-and-forward (DF). We prove that the RF/FSO communication in the proposed relay-based architecture enhances the data transmission increasing the throughput and the real-time reception capacity and reducing the network energy consumption. The performance evaluation shows that the DF scheme overcomes the AF one in terms of energy consumption while the AF scheme overcomes the DF one in terms of probability detection, both experience the same throughput. Finally, the proposed novel architecture has been compared with existing ones showing that it enhances the current maritime surveillance systems by jointly optimizing communication functionalities.