Current Issue : October - December Volume : 2014 Issue Number : 4 Articles : 4 Articles
This paper studies the auction-driven dynamic spectrum access in cognitive radio networks with heterogeneous\nsecondary users, who have different risk attitudes. First, a game theoretic framework is established for auction-driven\ndynamic spectrum access in cognitive radio networks. The utility functions and bidding strategies of heterogeneous\nsecondary users are defined, and the parameterized auction mechanisms of primary user are also introduced. Then,\nwe formulate the auction-driven dynamic spectrum access problem as a finite discrete game with a mixed- or\npure-strategy Nash equilibrium solution. We study the existence and uniqueness properties of the pure-strategy Nash\nequilibrium in the defined game. Next, we propose a distributed learning automata algorithm (DLA) to attain the Nash\nequilibrium of the defined game with limited feedback. The adaptive mechanism design is realized in the updating\nprocedure of our DLA algorithm. We further prove that our DLA algorithm converges to a Nash equilibrium of the\ndefined game. Finally, simulation results show that our DLA algorithm is efficient and outperforms the dynamic\nspectrum access schemes with fixed auction mechanism....
This paper discusses how educators could use the cognitive constructivist theory of multimedia (CCTM)\nto design interactive digital learning materials using Camtasia and Audacity. Camtasia allows educators to\ncreate videos that motivate students, inform parents and enhance learning. It allows educators to record\nlive presentations or lectures and provide students with a file to review. Audacity is a free cross-platform\naudio editor and recorder for Windows, Mac OS X, GNU/Linux and other operating systems. CCTM advocates\nfor the design of instruction using pictures, videos, audios and words that tap into the prior experiences\nof the learner, promote active learning, collaboration, personal autonomy, personal growth and\nalternative assessment that is aligned with multiple intelligences of learners as espoused by Gardener\n(1993) which are Linguistics, Logico-mathematics, Spatial, Musical, Bodily-kinesthetic, Interpersonal,\nIntrapersonal and Naturalist. Camtasia and Audacity promote use of CCTM because of their capabilities\nto construct knowledge through words, pictures, animations, videos and audio. Case studies show that use\nof teacher-made files could significantly impact students� learning. Use of teacher-made interactive digital\nlearning materials could revolutionize educational presentations and enhance e-learning delivery. CCMT\nproduced by dynamic presentations creates a balance between the learners� prior verbal and visual experiences,\nsensory repository, multiple intelligences and learning styles to construct new knowledge....
Over the past years, we have witnessed an explosive growth in the use of multimedia applications such as audio and\nvideo streaming with mobile and static devices. Multimedia streaming applications need new approaches to multimedia\ntransmissions to meet the growing volume demand and quality expectations of multimedia traffic. This paper studies\nnetwork coding which is a promising paradigm that has the potential to improve the performance of networks for multimedia\nstreaming applications in terms of packet delivery ratio (PDR), latency and jitter. This paper examines several\nnetwork coding protocols for ad hoc wireless mesh networks and compares their performance on multimedia streaming\napplications with optimized broadcast protocols, e.g., BCast, Simplified Multicast Forwarding (SMF), and Partial\nDominant Pruning (PDP). The results show that the performance increases significantly with the Random Linear Network\nCoding (RLNC) scheme....
Multi-carrier (MC) signaling is currently in the forefront of a myriad of systems, either wired or wireless, due to its high\nspectral efficiency, simple equalization, and robustness in front of multipath and narrowband interference sources.\nDespite its widespread deployment, the design of efficient architectures for MC systems becomes a challenging task\nwhen adopting filter bank multi-carrier (FBMC) modulation due to the inclusion of band-limited shaping pulses into\nthe signal model. The reason to employ these pulses is the numerous improvements they offer in terms of\nperformance, such as providing higher spectral confinement and no frequency overlap between adjacent subcarriers.\nThese attributes lead to a reduced out-of-band power emission and a higher effective throughput. The latter is indeed\npossible by removing the need of cyclic prefix, which is in charge of preserving orthogonality among subcarriers in\nconventional MC systems. Nevertheless, the potential benefits of FBMC modulations are often obscured when it\ncomes to an implementation point of view. In order to circumvent this limitation, the present paper provides a unified\nframework to describe all FBMC signals in which both signal design and implementation criteria are explicitly\ncombined. In addition to this, we introduce the concept of flexible FBMC signals that, unlike their traditional MC\ncounterparts, do not impose restrictions on the signal parameters (i.e., symbol rate, carrier spacing, or sampling\nfrequency). Moreover, our framework also proposes a methodology that overcomes the implementation issues that\ncharacterize FBMC systems and allows us to derive simple, efficient, and time-invariant transmitter and receiver\narchitectures....
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