Communications and Network, 2013, 5, 225-230 http://dx.doi.org/10.4236/cn.2013.53027 Published Online August 2013 (http://www.scirp.org/journal/cn) Improving the Reliability of Unmanned Aircraft System Wireless Communications through Cognitive Radio Technology Hector Reyes * , Naima Kaabouch Electrical Engineering Department, University of North Dakota, Grand Forks, USA Email: * hector.reyesmoncayo@my.und.edu, naima.kaabouch@engr.und.edu Received May 24, 2013; revised June 24, 2013; accepted July 24, 2013 Copyright © 2013 Hector Reyes, Naima Kaabouch. This is an open access article distributed under the Creative Commons Attribu- tion License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. ABSTRACT Unmanned Aircraft System networks are a special type of networks where high speeds of the nodes, long distances and radio spectrum scarcity pose a number of challenges. In these networks, the strength of the transmitted/received signals varies due to jamming, multipath propagation, and the changing distance among nodes. High speeds cause another problem, Doppler Effect, which produces a shifting of the central frequency of the signal at the receiver. In this paper we discuss a modular system based on cognitive to enhance the reliability of UAS networks. Keywords: UAS; Intelligent Communication Systems; Cognitive Radio; Reliability 1. Introduction Wireless Communication plays a crucial role in unman- ned aircraft systems (UAS) security and accomplishment of their missions [1]. UAS have recently received rapidly growing and widespread interest for military and civil purposes. The U.S. military market is projected to grow at a CAGR (Compound Annual Growth Rate) of 10%. Revenues of $62 billion are predicted over the period of 2010-2015 [2]. Currently, most of the applications of UAS are concentrated on the military. Their application to civil operations is still very limited due to the lack of special regulation that leverages the integration of UAS to the national airspace system (NAS) [3]. One of the concerns of the federal aviation administration (FAA) is the availability and allocation of spectrum and bandwidth for communication, command, and control so that the UAS can meet the safety regulations without conflicting with existing systems. Unlike in conventional networks, in UAS networks there is not a dominant communication standard or tech- nology. On the contrary, one of the problems in the de- velopment of UAS is the lack of compatibility among different platforms [4]. For example, Predator vehicles use C-band for their line of sight communications whereas Global Hawk vehicles use CDL and UHF SATCOM. In addition to this lack of compatibility, UAS networks face other challenges including large distances and high speeds of the aircraft [5]. Large distances cause propaga- tion losses that reduce the power and the signal to noise ratio (SNR) at the receiver, which in turn affects the availability and throughput of the data links. High speeds of aircraft produce a shifting of the frequency at the re- ceiver called Doppler Spread. Additional problems, such as harsh environment, jamming and multipath fading as well as shadowing due to obstacles make the design of UAS networks a critical task, where it is necessary to incorporate unconventional techniques. In this paper, we describe a methodology to increase the reliability of UAS networks. This technique is based on cognitive radio supported by software defined radio technology. Both technologies are emerging and are still in their infancy. Cognitive radio was first introduced by J. Mitola in 2000 as a solution to solve the problem of radio spectrum scarcity and its inefficient usage and allocation. Although most of the current research focuses on the scarcity of the radio spectrum problem, this technology has also the potential to enhance the reliability of dy- namic networks [6] such as UAS networks. * Corresponding author. Copyright © 2013 SciRes. CN