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Spectrum Map and its Application in Cognitive Radio Networks
Title
Spectrum Map and its Application in Cognitive Radio Networks.
Creator
Debroy, Saptarshi, Chatterjee, Mainak, Bassiouni, Mostafa, Zou, Changchun, Jha, Sumit, Catbas, Necati, University of Central Florida
Abstract / Description
Recent measurements on radio spectrum usage have revealed the abundance of underutilizedbands of spectrum that belong to licensed users. This necessitated the paradigm shift from static to dynamic spectrum access. Cognitive radio based secondary networks thatutilize such unused spectrum holes in the licensed band, have been proposed as a possible solution to the spectrum crisis. The idea is to detect times when a particular licensed band is unused and use it for transmission without causing...
Show moreRecent measurements on radio spectrum usage have revealed the abundance of underutilizedbands of spectrum that belong to licensed users. This necessitated the paradigm shift from static to dynamic spectrum access. Cognitive radio based secondary networks thatutilize such unused spectrum holes in the licensed band, have been proposed as a possible solution to the spectrum crisis. The idea is to detect times when a particular licensed band is unused and use it for transmission without causing interference to the licensed user. We argue that prior knowledge about occupancy of such bands and the corresponding achievable performance metrics can potentially help secondary networks to devise effective strategiesto improve utilization.In this work, we use Shepard's method of interpolation to create a spectrum mapthat provides a spatial distribution of spectrum usage over a region of interest. It is achieved by intelligently fusing the spectrum usage reports shared by the secondary nodes at various locations. The obtained spectrum map is a continuous and differentiable 2-dimension distribution function in space. With the spectrum usage distribution known, we show how different radio spectrum and network performance metrics like channel capacity, secondary network throughput, spectral efficiency, and bit error rate can be estimated. We show the applicability of the spectrum map in solving the intra-cell channel allocation problem incentralized cognitive radio networks, such as IEEE 802.22. We propose a channel allocationscheme where the base station allocates interference free channels to the consumer premise equipments (CPE) using the spectrum map that it creates by fusing the spectrum usage information shared by some CPEs. The most suitable CPEs for information sharing arechosen on a dynamic basis using an iterative clustering algorithm. Next, we present a contention based media access control (MAC) protocol for distributed cognitive radio network. The unlicensed secondary users contend among themselves over a common control channel. Winners of the contention get to access the available channels ensuring high utilization and minimum collision with primary incumbent. Last, we propose a multi-channel, multi-hop routing protocol with secondary transmission power control. The spectrum map, created and maintained by a set of sensors, acts as the basis of finding the best route for every source destination pair. The proposed routing protocol ensures primary receiver protection and maximizes achievable link capacity.Through simulation experiments we show the correctness of the prediction model and how it can be used by secondary networks for strategic positioning of secondary transmitter-receiver pairs and selecting the best candidate channels. The simulation model mimics realistic distribution of TV stations for urban and non-urban areas. Results validate the nature and accuracy of estimation, prediction of performance metrics, and efficiency of the allocation process in an IEEE 802.22 network. Results for the proposed MAC protocol show high channel utilization with primary quality of service degradation within a tolerable limit. Performance evaluation of the proposed routing scheme reveals that it ensures primary receiver protection through secondary power control and maximizes route capacity.
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Date Issued
2014
Identifier
CFE0005324, ucf:50515
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0005324
MULTI-MODAL READING FOR LOW LEVEL READERS
Title
MULTI-MODAL READING FOR LOW LEVEL READERS.
Creator
O'Neal, Jamie, Dombrowski, Paul, University of Central Florida
Abstract / Description
The value of this research hinges on the idea that exchanging illustrations for descriptive text can provide appropriate schemas for students with reading difficulties and thereby improve their comprehension and vocabulary acquisition. The research in this dissertation is based on theories and earlier research in the fields of psychology, education, reading, and narratology. A review of these fields offers a variety of perspectives on the processes involved in reading and comprehension. These...
Show moreThe value of this research hinges on the idea that exchanging illustrations for descriptive text can provide appropriate schemas for students with reading difficulties and thereby improve their comprehension and vocabulary acquisition. The research in this dissertation is based on theories and earlier research in the fields of psychology, education, reading, and narratology. A review of these fields offers a variety of perspectives on the processes involved in reading and comprehension. These processes range from the physical systems involved in reading (e.g., early childhood development, eye movement) to the psychological systems, which include cognitive load theory as well as image and text processing models. This study compares two reading methods by analyzing studentsÂÂ' vocabulary and comprehension gains. Both groups read the same text and completed the same pre- and post-tests. The control group read the text from the book which was text only. The experimental group read from a modified text on the computer screen. The text was modified by replacing some sentences with images designed to transmit the same information (e.g., descriptions of the setting, vocabulary items) in a graphic format. The images were in-line with the text, and designed to be read as part of the story, not as additional illustrations. Final analysis shows that the experimental format performed as well as the control format for most students. However, students who have learning disabilities, particularly language learners who have learning disabilities, did not make gains in the text only control format. These same students did show statistically significant gains with the experimental format, particularly the section of reading where the vocabulary words were explicitly presented in the images. Disparate, non-homogenous groupings of students reflect the actual teaching and learning circumstances in the school, as required by the school system. This situation thus represents the actual status quo situation faced by teachers in our school. We leave it to future researchers to work with more homogenous groups of students in order to attain clearer, stronger and more plaintively useful results.
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Date Issued
2010
Identifier
CFE0003306, ucf:48486
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0003306