Voice Capacity and Data Response Time in Cognitive Radio Networks

The growing interest towards wireless communication services over the recent years has increased the demand for radio spectrum. Inefficient spectrum management together with the scarcity of the radio spectrum is a limiting factor for the development of modern wireless networks. As a solution, the idea of cognitive radio networks (CRNs) is introduced to use licensed spectrum for the benefit of the unlicensed secondary users. However, the preemptive priority of the licensed users results in random resource availabilities at the secondary networks, which makes the quality-of-service (QoS) support challenging. With the increasing demand for elastic/interactive data services (internet based services) and wireless multimedia services, QoS support becomes essential for CRNs. This research investigates the voice and elastic/interactive data service support over CRNs, in terms of their delay requirements. The packet level requirements of the voice service and session level delay requirements of the elastic/interactive data services are studied. In particular, constant-rate and on-off voice traffic capacities are analyzed over CRNs with centralized and distributed network coordination. Some generic channel access schemes are considered as the coordination mechanism, and call admission control algorithms are developed for non-fully-connected CRNs. Advantage of supporting voice traffic flows with different delay requirements in the same network is also discussed. The mean response time of the elastic data traffic over a centralized CRN is studied, considering the shortest processor time with and without preemption and shortest remaining processor time service disciplines, in comparison with the processor sharing service discipline. Effects of the traffic load at the base station and file length (service time requirement) distribution on the mean response time are discussed. Finally, the relationship between the mean response times of interactive and elastic data traffic is studied

Making pro-environmental behaviour work: an ethnographic case study of practice, process and power in the workplace

Conventional approaches to pro-environmental behaviour change rest on individualistic and reductive assumptions which posit that behaviour is the outcome of a linear and ultimately rational process of decision-making. Policy approaches have thus concentrated on providing tailored environmental information to individuals to encourage (eco)rational decisions and on removing barriers to 'correct' behaviour, and research has tended to focus on modelling the influences on individual decision-making processes through large scale questionnaire surveys.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

NASA/American Society for Engineering Education (ASEE) Summer Faculty Fellowship Program 1989

Since 1964, NASA has supported a program of summer faculty fellowships for engineering and science educators. The objectives are: to further the professional knowledge of qualified engineering and science faculty; to stimulate and exchange ideas between participants and NASA; to enrich and refresh the research and teachning activities of participants' institutions; and to contribute to the research objectives of the NASA center. College or university faculty members will be appointed as Research Fellows to spend 10 weeks in cooperative research and study at the NASA Langley Research Center. The Fellow will devote approximately 90 percent of the time to a research problem and the remaining time to a study program. The study program will consist of lecture and seminars on topics of interest or that are directly relevant to the Fellows' research topic