This book focuses on the issue of optimizing radio resource allocation (RRA) and user admission control (AC) for multiple multicasting sessions on a single high altitude platform (HAP) with multiple antennas on-board. HAPs are quasi-stationary aerial platforms that carry a wireless communications payload to provide wireless communications and broadband services. They are meant to be located in the stratosphere layer of the atmosphere at altitudes in the range 17-22 km and have the ability to fly on demand to temporarily or permanently serve regions with unavailable telecommunications infrastructure. An important requirement that the book focusses on is the development of an efficient and effective method for resource allocation and user admissions for HAPs, especially when it comes to multicasting. Power, frequency, space (antennas selection) and time (scheduling) are the resources considered in the problem over an orthogonal frequency division multiple access (OFDMA) HAP system.Due to the strong dependence of the total number of users that could join different multicast groups, on the possible ways we may allocate resources to these groups, it is of significant importance to consider a joint user to session assignments and RRA across the groups. From the service provider's point of view, it would be in its best interest to be able to admit as many higher priority users as possible, while satisfying their quality of service requirements. High priority users could be users subscribed in and paying higher for a service plan that gives them preference of admittance to receive more multicast transmissions, compared to those paying for a lower service plan. Also, the user who tries to join multiple multicast groups (i.e. receive more than one multicast transmission), would have preferences for which one he would favor to receive if resources are not enough to satisfy the QoS requirements.Technical topics discussed in the book include: • Overview on High Altitude Platforms, their different types and the recent works in this area Radio Resource Allocation and User Admission Control in HAPs Multicasting in a Single HAP System: System Model and Mathematical Formulation Optimization schemes that are designed to enhance the performance of a branch and bound technique by taking into account special mathematical structure in the problem formulation

Professor Zabih Ghassemlooy (CEng, Fellow of IET, senior member of IEEE) received his BSc (Hons.) in electrical and electronics engineering from the Manchester Metropolitan University in 1981, and his MSc and Ph.D in optical communications from the University of Manchester Institute of Science and Technology thereafter in 1984 and 1987, respectively. Currently he is an associate dean for research in the School of Computing, Engineering and Information Sciences, University of Northumbria at Newcastle upon Tyne, UK. He also heads the Northumbria Communications Research Laboratories within the school. His research interests are mainly in the area of optical communications, and published over 415 papers. He is the founder and the chairman of the IEEE, IET International Symposium on Communication Systems, Network and Digital Signal Processing.

Dr. W. Popoola had his national diploma in electrical engineering from The Federal Polytechnic, Ilaro, Nigeria and later graduated with first class honours degree in electronic and electrical engineering from Obafemi Awolowo University, Nigeria. He later proceeded to Northumbria University at Newcastle upon Tyne, England, UK, for his MSc in optoelectronic and communication systems where he graduated with distinction in 2006. He was awarded his Ph.D. in 2009 at the Northumbria University for his research work in free-space optical communications. He is currently a researcher with the Institute for Digital Communications, University of Edinburgh, UK working on visible light communications.

Dr. S. Rajbhandari obtained his bachelor degree in electronics and communication engineering from the Institute of Engineering, Pulchowk Campus (Tribhuvan University), Nepal in 2004. In 2006, he received an MSc in optoelectronic and communication systems with distinction and was awarded the P. O. Byrne prize for most innovative project. He then joined the Optical Communications Research Lab (OCRG) at Northumbria University and was awarded a Ph.D degree in 2010. Since 2009, he has been with the OCRG at Northumbria University working as a postdoctoral researcher. He has published more than 70 scholarly articles in the area of optical wireless communications.