Technical Challenges in Network- Centric Control and Communication Systems Vasilis N. Tsoulkas 1,2 , Leonidas Dritsas 3 and Athanasios A. Pantelous 4 1 General Secretariat for Research and Technology, Athens, GR 2 National Delegate to the Joint Communications Board of the European Space Agency (JCB/ESA) 3 Hellenic Air Force Academy, Division of Automatic Control, Athens, GR. 4 Department of Mathematical Sciences, University of Liverpool, U.K btsu@gsrt.gr , ldri@otenet.gr and A.Pantelous@liverpool.ac.uk Abstract-This paper is concerned with the technical challenges arising from the emerging unification of network-centric con- trol and communications. Specifically we are following two main directions. Firstly we briefly explore the current trends in the development of advanced satellite communications and hybrid satellite/terrestrial networks. Various technical issues are addressed and discussed within the field of integrated satel- lite systems and novel network architectures. Secondly we are concerned with the fast developing area of networked con- trolled systems (NCSs). In that respect relevant research prob- lems are investigated in conjunction with possible future direc- tions. Finally we conclude providing some specific research and development efforts related to state of the art integrated systems and services lying at the intersection of the above two categories and which are initiated and supported by interna- tional government and industrial organizations. Keywords: Network-Centric Control, Communication Systems. I. INTRODUCTION The establishment and continuous proliferation of inte- grated and distributed information networks in modern socie- ty is beyond any doubt. Moreover new network architectures integrating different components and elements are being developed by the industrial and academic sectors in a fast changing technological environment. In this paper we will focus our attention on some key technical issues and future trends related to integrated satellite systems as well as the emerging field of networked control systems (NCS) and their interplay. NCSs are distributed control systems comprised of the plant, the actuators and sensors and the controllers all inter- connected through a communications network as shown in Fig.1 below. In this type of architectures the control loop is closed with a communication network making the analysis of such systems considerably more complex than the typical point-to-point control schemes. Moreover wireless connec- tions of the distributed devices and elements are gaining popularity in an abundance of industrial applications raising new technical and theoretical challenges in communication and information theory and their interrelationship to net- worked control setups. New questions need to be resolved with respect to: band- width constraints, fading of the transmission channel, new distributed sensing requirements and transmission-induced delays, variable and fixed data sampling within the data net- work as well as the effect of packet rates and dropouts to the stability behavior of the control system. In other words ro- bust and reliable control over unreliable data networks is indeed a major technical challenge with serious implications on the performance of NCSs. Extending this concept to air and space systems we are faced with the challenge of coor- dinated control of applications involving UAVs (Unmanned Aerial Vehicles) and Satellite Constellations through ad- vanced hybrid and integrated communication links. On the other hand in the space sector there is a strong trend towards integrated satellite/terrestrial based communi- cation systems. In the sequel we will discuss specific tech- nical issues related to system concepts of distributed satellite networks and fundamental state of the art technical chal- lenges that need to be resolved. Our view will be towards the integration of NCSs with advanced hybrid satellite systems. II. I NTEGRATED SATELLITE SYSTEMS AND TERRESTRIAL NETWORKS The telecommunications market is going through various transformations affecting the satellite and terrestrial telecom industrial sector. More specifically the European satellite sector is experiencing a turbulent evolution with majoring restructuring efforts of the industry, changes among stake- holders of the main service providers and consolidation of the manufacturing capabilities. In parallel the continuous evolution of Information and Communication technologies as well as new and demanding user needs have been a con- stant triggering factor for the adaptation of satellite solutions to new technical directions. It is evident that future services will strongly depend on hybrid architectures as it is pointed out in [12] and [17]. In the last few years satellites have stea- dily increased and expanded their role in integrated networks for traditional public telephony (PSTN) and data tran- smission despite the widespread penetration of terrestrial links. The main advantages are: • Support for global mobility. • Fast deployment for the provision of new services on lo- cal and global scales. 2010 International Conference on Intelligent Systems, Modelling and Simulation 978-0-7695-3973-7/10 $26.00 © 2010 IEEE DOI 10.1109/ISMS.2010.55 256 2010 International Conference on Intelligent Systems, Modelling and Simulation 978-0-7695-3973-7/10 $26.00 © 2010 IEEE DOI 10.1109/ISMS.2010.55 256