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Digital Communications and Networking Commons™

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Air Force Institute of Technology

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Articles 121 - 150 of 166

Full-Text Articles in Digital Communications and Networking

Network Visualization Design Using Prefuse Visualization Framework, John Mark Belue Mar 2008

Network Visualization Design Using Prefuse Visualization Framework, John Mark Belue

Theses and Dissertations

Visualization of network simulation events or network visualization is an effective and low cost method to evaluate the health and status of a network and analyze network designs, protocols, and network algorithms. This research designed and developed a network event visualization framework using an open source general visualization toolkit. This research achieved three major milestones during the development of this framework: A robust network simulator trace file parser, multiple network visualization layouts {including user-defined layouts, and precise visualization timing controls and integrated display of network statistics. The parser architecture is extensible to allow customization of simulator trace formats that are …

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Scripted Mobile Network Routing In A Contested Environment, Anthony R. Otto Mar 2008

Scripted Mobile Network Routing In A Contested Environment, Anthony R. Otto

Theses and Dissertations

Mobile wireless network protocols currently run on optimistic routing algorithms, adjusting node connectivity only when the chosen connectivity metrics, such as signal strength, pass beyond minimum thresholds. Optimistic routing has several weaknesses. Optimistic routing suffers from increased network overhead during increased frequency of node movement and increased node density per area, and optimistic routing also suffers from non-optimistic access change for individual nodes. The overall communication throughput of a network may be increased if the network topology change is scripted; a scripted plan can allow messages to travel along a more efficient topological path while creating less topology control traffic. …

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Network Formation Using Ant Colony Optimization -- A Systematic Review, Steven C. Oimoen, Gilbert L. Peterson, Kenneth M. Hopkinson Jan 2008

Network Formation Using Ant Colony Optimization -- A Systematic Review, Steven C. Oimoen, Gilbert L. Peterson, Kenneth M. Hopkinson

Faculty Publications

A significant area of research in the field of hybrid communications is the Network Design Problem (NDP) [1]. The NDP is an NP complete problem [1] that focuses on identifying the optimal network topology for transmitting commodities between nodes, under constraints such as bandwidth, limited compatible directed channels, and link and commodity costs. The NDP focuses on designing a flexible network while trying to achieve optimal flow or routing. If a link (or arc) is used, then an associated fixed cost of the edge is incurred. In addition, there is a cost for using the arc depending on the flow. …

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Performance Analysis And Comparison Of Multiple Routing Protocols In A Large-Area, High Speed Mobile Node Ad Hoc Network, Daniel K. Roberts Jun 2007

Performance Analysis And Comparison Of Multiple Routing Protocols In A Large-Area, High Speed Mobile Node Ad Hoc Network, Daniel K. Roberts

Theses and Dissertations

The U.S. Air Force is interested in developing a standard ad hoc framework using "heavy" aircraft to route data across large regions. The Zone Routing Protocol (ZRP) has the potential to provide seamless large-scale routing for DOD under the Joint Tactical Radio System program. The goal of this study is to determine if there is a difference between routing protocol performance when operating in a large-area MANET with high-speed mobile nodes. This study analyzes MANET performance when using reactive, proactive, and hybrid routing protocols, specifically AODV, DYMO, Fisheye, and ZRP. This analysis compares the performance of the four routing protocols …

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Voice And Video Capacity Of A Secure Wireless System, Jason R. Seyba Jun 2007

Voice And Video Capacity Of A Secure Wireless System, Jason R. Seyba

Theses and Dissertations

Improving the security and availability of secure wireless multimedia systems is the purpose of this thesis. Specifically, this thesis answered research questions about the capacity of wireless multimedia systems and how three variables relate to this capacity. The effects of securing the voice signal, real-time traffic originating foreign to a wireless local area network and use of an audio-only signal compared with a combined signal were all studied. The research questions were answered through a comprehensive literature review in addition to an experiment which had thirty-six subjects using a secure wireless multimedia system which was developed as part of this …

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Distributed Fault-Tolerant Quality Of Service Routing In Hybrid Directional Wireless Networks, Larry C. Llewellyn Ii Mar 2007

Distributed Fault-Tolerant Quality Of Service Routing In Hybrid Directional Wireless Networks, Larry C. Llewellyn Ii

Theses and Dissertations

This thesis presents a distributed fault-tolerant routing protocol (EFDCB) for QoS supporting hybrid mobile ad hoc networks with the aim of mitigating QoS disruption time when network failures occur. The experimental design presented in this thesis describes 22 experiments aimed at illustrating EFDCB's ability to handle fault-tolerance. The interpreted results show that EFDCB excels over a global rerouting protocol at this challenge which is the goal of this work.

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Effective Mobile Routing Through Dynamic Addressing, Heungsoon Park Mar 2007

Effective Mobile Routing Through Dynamic Addressing, Heungsoon Park

Theses and Dissertations

Military communications has always been an important factor in military victory and will surely play an important part in future combat. In modern warfare, military units are usually deployed without existing network infrastructure. The IP routing protocol, designed for hierarchical networks cannot easily be applied in military networks due to the dynamic topology expected in military environments. Mobile ad-hoc networks (MANETs) represent an appropriate network for small military networks. But, most ad-hoc routing protocols suffer from the problem of scalability for large networks. Hierarchical routing schemes based on the IP address structure are more scalable than ad-hoc routing but are …

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On-Demand Key Distribution For Mobile Ad-Hoc Networks, Daniel F. Graham Mar 2007

On-Demand Key Distribution For Mobile Ad-Hoc Networks, Daniel F. Graham

Theses and Dissertations

Mobile ad-hoc networks offer dynamic portable communication with little or no infrastructure. While this has many benefits, there are additional shortcomings specific to wireless communication that must be addressed. This research proposes gossip-based on-demand key distribution as a means to provide data encryption for mobile ad-hoc networks. This technique uses message keys to avoid encrypting and decrypting a message at every node. Other optimizations used include secure channel caching and joint rekey messages. The use of gossip makes the scheme robust to node failure. Experimental results show only a 15% increase in end-to-end delay with a node failure rate of …

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Overcoming Tcp Degradation In The Presence Of Multiple Intermittent Link Failures Utilizing Intermediate Buffering, Duane F. Harmon Mar 2007

Overcoming Tcp Degradation In The Presence Of Multiple Intermittent Link Failures Utilizing Intermediate Buffering, Duane F. Harmon

Theses and Dissertations

It is well documented that assumptions made in the popular Transmission Control Protocol's (TCP) development, while essential in the highly reliable wired environment, are incompatible with today's wireless network realities in what we refer to as a challenged environment. Challenged environments severely degrade the capability of TCP to establish and maintain a communication connection with reasonable throughput. This thesis proposes and implements an intermediate buffering scheme, implemented at the transport layer, which serves as a TCP helper protocol for use in network routing equipment to overcome short and bursty, but regular, link failures. Moreover, the implementation requires no modifications to …

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Performance Evaluation Of Ad Hoc Routing In A Swarm Of Autonomous Aerial Vehicles, Matthew T. Hyland Mar 2007

Performance Evaluation Of Ad Hoc Routing In A Swarm Of Autonomous Aerial Vehicles, Matthew T. Hyland

Theses and Dissertations

This thesis investigates the performance of three mobile ad hoc routing protocols in the context of a swarm of autonomous unmanned aerial vehicles (UAVs). It is proposed that a wireless network of nodes having an average of 5.1774 log n neighbors, where n is the total number of nodes in the network, has a high probability of having no partitions. By decreasing transmission range while ensuring network connectivity, and implementing multi-hop routing between nodes, spatial multiplexing is exploited whereby multiple pairs of nodes simultaneously transmit on the same channel. The proposal is evaluated using the Greedy Perimeter Stateless Routing (GPSR), …

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Analysis Of Routing Worm Infection Rates On An Ipv4 Network, James Gorsuch Mar 2007

Analysis Of Routing Worm Infection Rates On An Ipv4 Network, James Gorsuch

Theses and Dissertations

Malicious logic, specifically worms, has caused monetary expenditure problems to network users in the past. Worms, like Slammer and Code Red, have infected thousands of systems and brought the Internet to a standstill. This research examines the ability of the original Slammer worm, the Slammer based routing worm proposed by Zou et al, and a new Single Slash Eight (SSE) routing worm proposed by this research to infect vulnerable systems within a given address space. This research investigates the Slammer worm's ability to generate a uniform random IP addresses in a given address space. Finally, a comparison of the speed …

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Supplementing An Ad-Hoc Wireless Network Routing Protocol With Radio Frequency Identification (Rfid) Tags, Leroy S. Willemsen Mar 2006

Supplementing An Ad-Hoc Wireless Network Routing Protocol With Radio Frequency Identification (Rfid) Tags, Leroy S. Willemsen

Theses and Dissertations

Wireless sensor networks (WSNs) have a broad and varied range of applications, yet all of these are limited by the resources available to the sensor nodes that make up the WSN. The most significant resource is energy. A WSN may be deployed to an inhospitable or unreachable area, leaving it with a non-replenishable power source. This research examines a way of reducing energy consumption by augmenting the nodes with radio frequency identification (RFID) tags that contain routing information. It was expected that RFID tags would reduce the network throughput, the ad hoc on-demand distance vector (AODV) routing traffic sent, and …

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Characterization And Design Of High-Level Vhdl I/Q Frequency Downconverter Via Special Sampling Scheme, Jesse P. Somann Mar 2006

Characterization And Design Of High-Level Vhdl I/Q Frequency Downconverter Via Special Sampling Scheme, Jesse P. Somann

Theses and Dissertations

This study explores the characterization and implementation of a Special Sampling Scheme (SSS) for In-Phase and Quad-Phase (I/Q) down conversion utilizing top-level, portable design strategies. The SSS is an under-developed signal sampling methodology that can be used with military and industry receiver systems, specifically, United States Air Force (USAF) video receiver systems. The SSS processes a digital input signal-stream sampled at a specified sampling frequency, and down converts it into In-Phase (I) and Quad-Phase (Q) output signal-streams. Using the theory and application of the SSS, there are three main objectives that will be accomplished: characterization of the effects of input, …

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Optimal Coverage Of Theater Targets With Small Satellite Constellations, Axel Rendon Mar 2006

Optimal Coverage Of Theater Targets With Small Satellite Constellations, Axel Rendon

Theses and Dissertations

The daylight passes of a low-Earth orbit satellite over a targeted latitude and longitude are optimized by varying the inclination and eccentricity of an orbit at different altitudes. This investigation extends the work by Emery et al, in which the optimal Right Ascension of the Ascending Node was determined for a circular, matched inclination orbit. The optimal values were determined by a numerical research method based on Emery et al's Matlab program. Results indicate that small increases in inclination raise the number of daylight passes up to 33%. These optimal inclinations depend on the satellite semi-major axis. Eccentricity increases also …

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Geolocation Of A Node On A Local Area Network, John R. Clarson Mar 2005

Geolocation Of A Node On A Local Area Network, John R. Clarson

Theses and Dissertations

Geolocation is the process of identifying a node using only its Internet Protocol (IP) address. Locating a node on a LAN poses particular challenges due to the small scale of the problem and the increased significance of queuing delay. This study builds upon existing research in the area of geolocation and develops a heuristic tailored to the difficulties inherent in LANs called the LAN Time to Location Heuristic (LTTLH). LTTLH uses several polling nodes to measure latencies to end nodes, known locations within the LAN. The Euclidean distance algorithm is used to compare the results with the latency of a …

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Automatic Generation Of Social Network Data From Electronic-Mail Communications, Jason Yee, Robert F. Mills, Gilbert L. Peterson, Summer E. Bartczack Jan 2005

Automatic Generation Of Social Network Data From Electronic-Mail Communications, Jason Yee, Robert F. Mills, Gilbert L. Peterson, Summer E. Bartczack

Faculty Publications

Most organizations have formal and informal elements. Formal structures are usually documented in organizational charts showing chain of command, levels of authority, and personnel resources. The actual effectiveness of the organization or specific individuals may actually depend on informal structures and internal communication networks. These are by definition personality-dependent and may provide significant insight into how work actually gets done within the organization. Effective leaders will want insight into these informal structures for various reasons. Inefficient decision-making or staffing processes may result in unnecessary or redundant communications, chokepoints, or single points of failure, each of which can either delay decisions …

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Device Discovery In Frequency Hopping Wireless Ad Hoc Networks, Brian S. Peterson Sep 2004

Device Discovery In Frequency Hopping Wireless Ad Hoc Networks, Brian S. Peterson

Theses and Dissertations

This research develops a method for efficient discovery of wireless devices for a frequency hopping spread spectrum, synchronous, ad hoc network comprised of clustered sub-networks. The Bluetooth wireless protocol serves as the reference protocol. The development of a discovery, or outreach, method for scatternets requires the characterization of performance metrics of Bluetooth piconets, many of which are unavailable in literature. Precise analytical models characterizing the interference caused to Bluetooth network traffic by inquiring devices, the probability mass function of packet error rates between arbitrary pairs of Bluetooth networks, and Bluetooth discovery time distribution are developed. Based on the characterized performance …

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An Analysis Of Electromagnetic Interference (Emi) Of Ultra Wideband(Uwb) And Ieee 802.11a Wireless Local Area Network (Wlan) Employing Orthogonal Frequency Division Multiplexing (Ofdm), Juan Lopez Jr. Mar 2004

An Analysis Of Electromagnetic Interference (Emi) Of Ultra Wideband(Uwb) And Ieee 802.11a Wireless Local Area Network (Wlan) Employing Orthogonal Frequency Division Multiplexing (Ofdm), Juan Lopez Jr.

Theses and Dissertations

Military communications require the rapid deployment of mobile, high-bandwidth systems. These systems must provide anytime, anywhere capabilities with minimal interference to existing military, private, and commercial communications. Ultra Wideband (UWB) technology is being advanced as the next generation radio technology and has the potential to revolutionize indoor wireless communications. The ability of UWB to mitigate multipath fading, provide high-throughput data rates (e.g., greater than 100 Mbps), provide excellent signal penetration (e.g., through walls), and low implementation costs makes it an ideal technology for a wide range of private and public sector applications. Preliminary UWB studies conducted by The Institute for …

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Interference Suppression In Multiple Access Communications Using M-Ary Phase Shift Keying Generated Via Spectral Encoding, Abel S. Nunez Mar 2004

Interference Suppression In Multiple Access Communications Using M-Ary Phase Shift Keying Generated Via Spectral Encoding, Abel S. Nunez

Theses and Dissertations

A conceptual transform domain communication system (TDCS) is shown capable of operating successfully using M-Ary phase shift keying (MPSK) data modulation in a multiple access environment. Using spectral encoding, the conceptual TDCS provides an effective means for mitigating interference affects while achieving multiple access communications. The use of transform domain processing with MPSK data modulation (TD-MPSK) provides higher spectral efficiency relative to other modulation techniques (antipodal signaling and cyclic shift keying) considered previously for TDCS applications. The proposed TD-MPSK technique uses spectral encoding for both data and multiple access phase modulations. Demodulation of the spectrally encoded TD-MPSK communication symbols is …

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A Communications Modeling System For Swarm-Based Sensors, Brian A. Kadrovach Sep 2003

A Communications Modeling System For Swarm-Based Sensors, Brian A. Kadrovach

Theses and Dissertations

Today's information age has exploded the amount of data available to decision makers at all levels of the control hierarchy. The miniaturization and proliferation of sensor technology has enabled extensive detection and monitoring and advances in computational capabilities have provided for embedded data analysis and the generation of information from raw data. Additionally, with the miniaturization of mechanical systems it is possible to provide platforms for sensor suites that are capable of mobility and limited autonomy. Swarming or bio-emergent behavior problems, provides a robust scalable mechanism for organizing large numbers of mobile sensor platforms. However, the mobility dynamics of swarm …

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Characterizing Data Streams Over Ieee 802.11b Ad-Hoc Wireless Networks, John T. Wagnon Mar 2003

Characterizing Data Streams Over Ieee 802.11b Ad-Hoc Wireless Networks, John T. Wagnon

Theses and Dissertations

Soon, advancements in data encryption technology will make real-time decryption of the contents of network packets virtually impossible. This research anticipates this development and extracts useful information based on packet level characteristics. Distinguishing characteristics from e-mail, HTTP, print, and FTP applications are identified and analyzed. The analysis of collected data from an ad-hoc wireless network reveals that distinguishing characteristics of network traffic do indeed exist. These characteristics include packet size, packet frequency, inter-packet correlation, and channel utilization. Without knowing the contents of packets or the direction of the traffic flow, the applications accessing the wireless network can be determined.

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Wlan Csma/Ca Performance In A Bluetooth Interference Environment, Randall B. Noel Mar 2003

Wlan Csma/Ca Performance In A Bluetooth Interference Environment, Randall B. Noel

Theses and Dissertations

IEEE 802.11 WLANs and Bluetooth piconets both operate in the 2.4 GHz Industrial Scientific and Medical (ISM) radio band. When operating in close proximity, these two technologies interfere with each other. Current literature suggests that IEEE 802.11 (employing direct sequence spread spectrum technology) is more susceptible to this interference than Bluetooth, which uses frequency hopping spread spectrum technology, resulting in reduced throughput. Current research tends to focus on the issue of packet collisions, and not the fact that IEEE 802.11 may also delay its transmissions while the radio channel is occupied by a Bluetooth signal. This research characterizes previously neglected …

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Multicast Routing Algorithms And Failure Analyses For Low Earth Orbit Satellite Communication Networks, Jae Soong Lee Aug 2002

Multicast Routing Algorithms And Failure Analyses For Low Earth Orbit Satellite Communication Networks, Jae Soong Lee

Theses and Dissertations

In the rapidly changing environment of mobile communications, the importance of the mobile satellite (e,g,, low earth orbit satellites (LEOsats)) networks will increase due to their global visibility and connection. Multicasting is an effective communication method in terms of frequency spectrum usage for a LEO network. It is devised to provide lower network traffic (i,e,, one-to-many transmissions). This research examines the system performance of two dissimilar terrestrially-based multicasting protocols: the Distance Vector Multicast Routing Protocol (DVMRP) and the On Demand Multicast Routing Protocol (ODMRP). These two protocols are simulated in large group membership density and in the presence of satellite …

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Autoassociative-Heteroassociative Neural Network, Claudia V. Kropas-Hughes, Steven K. Rogers, Mark E. Oxley, Matthew Kabrisky Jun 2002

Autoassociative-Heteroassociative Neural Network, Claudia V. Kropas-Hughes, Steven K. Rogers, Mark E. Oxley, Matthew Kabrisky

AFIT Patents

An efficient neural network computing technique capable of synthesizing two sets of output signal data from a single input signal data set. The method and device of the invention involves a unique integration of autoassociative and heteroassociative neural network mappings, the autoassociative neural network mapping enabling a quality metric for assessing the generalization or prediction accuracy of the heteroassociative neural network mapping.

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Analysis Of Ultra Wide Band (Uwb) Technology For An Indoor Geolocation And Physiological Monitoring System, Cengiz Alabacak Mar 2002

Analysis Of Ultra Wide Band (Uwb) Technology For An Indoor Geolocation And Physiological Monitoring System, Cengiz Alabacak

Theses and Dissertations

The goal of this research is to analyze the utility of UWB for indoor geolocation and to evaluate a prototype system, which will send information detailing a person’s position and physiological status to a command center. In a real world environment, geolocation and physiological status information needs to be sent to a command and control center that may be located several miles away from the operational environment. This research analyzes and characterizes the UWB signal in the various operational environments associated with indoor geolocation. Additionally, "typical usage scenarios" for the interaction between UWB and other devices are also tested and …

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Integrated Manet Mutual Authentication System, Jason T. Ballah Mar 2002

Integrated Manet Mutual Authentication System, Jason T. Ballah

Theses and Dissertations

The Integrated MANET Mutual Authentication System (IMMAS) provides implied mutual authentication of all routing and data traffic within a Mobile Ad Hoc Network (MANET) by combining Elliptic Curve Cryptography, a public-key cryptosystem, with the Dynamic Source Routing (DSR) Protocol. IMMAS provides security by effectively hiding network topology from adversaries while reducing the potential for, among other things, traffic analysis and data tampering, all while providing a graceful degradation for each of the authentication components. Current research in MANETs tends to focus primarily on routing issues leaving topics such as security and authentication for future research. IMMAS focuses on achieving a …

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Performance Analysis Of A Dynamic Bandwidth Allocation Algorithm In A Circuit-Switched Communications Network, Timothy M. Schwamb Mar 2002

Performance Analysis Of A Dynamic Bandwidth Allocation Algorithm In A Circuit-Switched Communications Network, Timothy M. Schwamb

Theses and Dissertations

Military communications networks typically employ a gateway multiplexer to aggregate all communications traffic onto a single link. These multiplexers typically use a static bandwidth allocation method via time-division multiplexing (TDM). Inefficiencies occur when a high-bandwidth circuit, e.g., a video teleconferencing circuit, is relatively inactive rendering a considerable portion of the aggregate bandwidth wasted while inactive. Dynamic bandwidth allocation (DBA) reclaims unused bandwidth from circuits with low utilization and reallocates it to circuits with higher utilization without adversely affecting queuing delay. The proposed DBA algorithm developed here measures instantaneous utilization by counting frames arriving during the transmission time of a single …

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Fabrication Techniques For Micro-Optical Device Arrays, Ryan D. Conk Mar 2002

Fabrication Techniques For Micro-Optical Device Arrays, Ryan D. Conk

Theses and Dissertations

Micro-optical devices are vital components of conventional military data storage, sensor, and communication systems. Two types of micro-optical device arrays exist: individually addressable and matrix addressable. The matrix addressable array has a drastically reduced number of metal lines and can potentially be fabricated into large, dense (over 1k elements) arrays. Such arrays are expected to enable the development of extremely high bandwidth optical interconnect systems for future military applications including optical computing and short-haul fiber optical communication systems. I investigate new fabrication techniques for the assembly of dense matrix-addressed arrays of micro-optical devices such as vertical-cavity surface-emitting lasers. Using a …

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A Direct Sequence Code-Division Multiple-Access Local Area Network Model, James R. Rapallo Jr. Mar 2002

A Direct Sequence Code-Division Multiple-Access Local Area Network Model, James R. Rapallo Jr.

Theses and Dissertations

The United States Air Force relies heavily on computer networks for every-day operations. The medium access control (MAC) protocol currently used by most local area (LAN) permits a single station to access the network at a time (e.g. CSMA/CD or Ethernet). This limits network throughput to, at most, the maximum transmission rate of a single node with overhead neglected. Significant delays are observed when a LAN is overloaded by multiple users attempting to access the common medium. In CSMA/CD, collisions are detected and the data sent by the nodes involved are delayed and transmitted at a later time. The retransmission …

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Wavelet Domain Communication System (Wdcs): Packet-Based Wavelet Spectral Estimation And M-Ary Signaling, Marion Jay F. Lee Mar 2002

Wavelet Domain Communication System (Wdcs): Packet-Based Wavelet Spectral Estimation And M-Ary Signaling, Marion Jay F. Lee

Theses and Dissertations

A recently proposed Wavelet Domain Communication System (WDCS) using transform domain processing demonstrated excellent interference avoidance capability under adverse environmental conditions. This work extends previous results by: 1) incorporating a wavelet packet decomposition technique, 2) demonstrating M-Ary signaling capability, and 3) providing increased adaptivity over a larger class of interference signals. The newly proposed packet-based WDCS is modeled and its performance characterized using MATLAB®. In addition, the WDCS response to two scenarios simulating Doppler effects and physical separation of transceivers are obtained. The fundamental metric for analysis and performance evaluation is bit error rate (Pb). Relative to …

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