Relay-assisted interference cancellation for cognitive aeronautical communication systems

Traditional air-ground communication systems are based on the principle of orthogonal transmission. For example, two adjacent Ground Stations communicate with their respective Air Stations on different subchannels. The orthogonal transmission leads to interference-free reception. However, the orthogonal transmission schemes also lead to poor spectrum utilization. Due to the limited spectrum availability, orthogonal transmission schemes may not cater the needs of future aeronautical communication demands. In this context, the present work proposes a cognitive overlay mode of transmission that is based on the non-orthogonal transmission to improve the spectrum efficiency. But the receivers in the non-orthogonal transmission based systems are interference-limited. This paper proposes decode-and-forward and amplify-and-forward relay-assisted interference cancellation schemes to mitigate the interference. The proposed relaying methods improve the reliability of the signal detection at the interference-free receiver. The ground-air wireless channels are modeled as Nakagami-m faded channel. The achievable diversity gain that characterizes the reliability of the signal detection at the receivers is also presented. The achievable diversity-multiplexing tradeoffs for the orthogonal and non-orthogonal transmission schemes are investigated in detail.