There is a growing demand for faster, improved data and voice services in rural areas without modern telecom infrastructure. A wireless network is often the only feasible solution for providing network access in this environment, due to the sparse populations and difficult natural conditions. A system solution that incorporates the Multipoint Communication System (MCS) algorithm created by TRLabs into the available IEEE 802.11b Wireless Local Area Network (WLAN) devices was proposed and studied in this thesis. It combines the advantages of both systems, that is, the MCS capability of integrating Voice over Internet Protocol (VoIP) and data services and the IEEE 802.11b standard, currently the most widely used in WLAN products. A system test bed was set up inside Network Simulator-2 (NS-2). The data and VoIP performance was tested. Modifications to the original MCS algorithm to improve system performance were made throughout this thesis. In a constant rate radio channel, data performance (throughput and transmission efficiency) was measured using the original MCS algorithm, which was comparable to the standard Distribution Coordination Function (DCF) operation of IEEE 802.11b when both were simulated at similar conditions. On an 802.11b platform, the Automatic Rate Fallback (ARF) feature was incorporated into the original MCS algorithm. However, when clients with different data rates were present in the same channel, all the clients involved received unacceptably low and equal data throughput, dragged down by the low rate clients. A modified MCS data polling algorithm was proposed with the capability of repeated polling, which eliminated the negative effect of low rate clients in a multi-rate channel. In addition, the original MCS algorithm was modified to be more efficient in the voice polling process. The voice performance and data throughput were tested at various conditions. However, the one-by-one polling still resulted in very low voice transmission efficiency. The time wasted became more severe with increasing relay distance and channel rate (only 8.5% in an 11 Mbps channel at 30 km). A new voice handling process similar to Time Division Multiple Access (TDMA) mode was implemented and simulated. Its voice efficiency can be kept at 25% at any setting of relay distance and channel rate. Data transmission in the same channel can also benefit from using the new voice scheme. The normalized saturation throughput could be improved by 13.5% if there were 40 voice clients involved in an 11 Mbps channel at the relay distance of 15 km, compared to the original MCS algorithm. More improvement in voice efficiency, voice capacity, and data throughput can be achieved at longer relay distance, or with more voice calls set up.

There is a growing demand for faster, improved data and voice services in rural areas without modern telecom infrastructure. A wireless network is often the only feasible solution for providing network access in this environment, due to the sparse populations and difficult natural conditions. A system solution that incorporates the Multipoint Communication System (MCS) algorithm created by TRLabs into the available IEEE 802.11b Wireless Local Area Network (WLAN) devices was proposed and studied in this thesis. It combines the advantages of both systems, that is, the MCS capability of integrating Voice over Internet Protocol (VoIP) and data services and the IEEE 802.11b standard, currently the most widely used in WLAN products. A system test bed was set up inside Network Simulator-2 (NS-2). The data and VoIP performance was tested. Modifications to the original MCS algorithm to improve system performance were made throughout this thesis. In a constant rate radio channel, data performance (throughput and transmission efficiency) was measured using the original MCS algorithm, which was comparable to the standard Distribution Coordination Function (DCF) operation of IEEE 802.11b when both were simulated at similar conditions. On an 802.11b platform, the Automatic Rate Fallback (ARF) feature was incorporated into the original MCS algorithm. However, when clients with different data rates were present in the same channel, all the clients involved received unacceptably low and equal data throughput, dragged down by the low rate clients. A modified MCS data polling algorithm was proposed with the capability of repeated polling, which eliminated the negative effect of low rate clients in a multi-rate channel. In addition, the original MCS algorithm was modified to be more efficient in the voice polling process. The voice performance and data throughput were tested at various conditions. However, the one-by-one polling still resulted in very low voice transmission efficiency. The time wasted became more severe with increasing relay distance and channel rate (only 8.5% in an 11 Mbps channel at 30 km). A new voice handling process similar to Time Division Multiple Access (TDMA) mode was implemented and simulated. Its voice efficiency can be kept at 25% at any setting of relay distance and channel rate. Data transmission in the same channel can also benefit from using the new voice scheme. The normalized saturation throughput could be improved by 13.5% if there were 40 voice clients involved in an 11 Mbps channel at the relay distance of 15 km, compared to the original MCS algorithm. More improvement in voice efficiency, voice capacity, and data throughput can be achieved at longer relay distance, or with more voice calls set up.

The decrease in price and the ease of use of wireless network devices make them an attractive alternative to standard wired networks. However, the intrinsic insecurity of wireless media and weaknesses in the standards for use of wireless media leave wireless networks vulnerable to attacks from unauthorized users. The intrinsic insecurity of wireless media results from radio signals extending beyond the networks intended coverage area and the weaknesses in the standards result from the methods used for authorization and privacy. These insecurities restrict the use of wireless networks by entities that need a high level of security. This paper describes a Wireless Intrusion Detection System (WIDS) that provides additional security for 802.11b wireless networks. WIDS provides intrusion detection that can react to potential threats and locate an intruder through the use of intelligent access points equipped with rotating directional antennas.

The thesis deals with improving location determination when using time of flight of radio signals to determine the location of a radiator. The goal of this project is to enhance an existing wireless data access point to perform an accurate measurement of the time of arrival of a data signal from a transmitter, and to combine this information with information from additional wireless data access points to determine the location of the transmitter. There have been a number of earlier efforts in indoor location determination system using different technologies. Many of which used signal strength analysis and they have low tolerance to moving obstacles such as humans, which frequently are the most usual dynamic obstacles in indoors. In this thesis, the proposed solution utilizes time stamping and sample correlation to utilize properties of the signal waveform, which has not previously been examined by researchers other than the examiner and advisor. The main contribution of the project is a detailed analysis and design of a solution, as well as a comparison with other potential solutions. The main purpose of this solution is to increase the timing accuracy to below the duration of a single symbol. The wireless device that has been analyzed implements the IEEE 802.11b protocol. Several investigations have been done to determine the best way of extracting information from the 802.11b data frame and symbol sequence; here we utilize a correlator to determine the time of arrival of a specific sequence of symbols in a data frame. The time stamping of a stream of samples has been implemented in an Altera FPGA to get a deterministic computation time. Instead of decoding the incoming I&Q signals and mapping them to bits, the correlator is used to detect the unique sequence containing PSK encoded and Barker code spread scrambled ones , as this sequence always appears at the start of each data frame. The advantage of this approach is that using of samples of the waveform instead of bits gives a significant enhancement in timing resolution. The design documents of this work include detailed descriptions, simulations, and plots. A number of simulations have been done to show the timing accuracy and standard deviation, as well as comparisons with several different approaches. Several potential optimizations have also been discussed in the report. Simulation code for MATLAB and implementation code for the FPGA has been included in appendices in the end of this thesis. / Denna rapport beskriver ett examensarbete som utgår ifrån att förbättra noggrannhet av en lokaliseringsteknik som tillämpar flygtiden av radiosignal för att mäta positionen av utsändaren. Målet av detta arbete är att förstärka en befintlig trådlösdata accesspunkt för att utföra en noggrann mätning av signals anländning från sändaren, och kombinera denna information från ytterliga trådlösdata accesspunkter för att lokalisera sändaren. Det har varit ett antal utvecklingar med olika teknologier för att ta fram en lösning för inomhus lokaliseringssystem. Många av de förslag som har kommit fram tillämpa signalstyrka och har en dålig tolerans av rörande hinder så som människor, vilka är det vanligaste fallet inomhus. Denna rapport ger ett förlag att lösa detta problem med att tillämpa tidstämpel och sampelkorrelation för att utnyttja egenskaper av signalens vågform, ett förlag som inte har blivit undersökt mycket av andra forskare. Stor del av denna rapport består av detaljerad analys och lösningsdesign, plus en jämförelse med andra potentiella lösningar. Meningen med denna lösning är att öka noggrannhet till att felmarginal i tid ska ligga under en symboltid. Den trådlösa enhet som har analyserats implementerar IEEE 802.11b protokollen. Flera undersökningar har utförts för att bestämma det bästa sättet att extrahera information från 802.11b dataramer och symbolsekvenser. För att göra det har vi implementerat en korrelator för att bestämma anländningstid av specifika symbolsekvenser i en dataram. En Altera FPGA har använts för att tidstämpla inkommande sampel för att ge en deterministisk beräkningstid. Istället för att avkoda inkommande I&Q signaler och mappa dem till bitar, har vi valt att implementera korrelator så att den opererar direkt på PSK-modulerade och Barkerkod-spridda ettor, eftersom att det visar sig att denna sekvens alltid visar sig i början av varje dataram. Fördelen med denna lösning är att direktanvändning av sampel ger en signifikant ökning på tidsupplösning jämfört med bitar. Designdokumentet av detta examensarbete består av detaljerade beskrivningar, simuleringar och grafer. Ett antal simuleringar har utförts för att visa tidsnoggrannhet och medelfel, plus jämförelser mellan olkia lösningsförslag. Olika möjliga optimeringar har också diskuterats i rapporten. Simuleringskod för MATLAB och implementeringskod FPGA bifogas i appendix slutet av denna rapport.

International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Wireless local area networks (WLANs) enable the extension of the Internet to aircrafts in flight. To establish this wireless network segment, commercial-of-the-shelve (COTS) 802.11b wireless Ethernet bridges were used. Wireless Ethernet bridges were chosen over optical wireless technology and Internet protocol (IP) satellite modems mainly because of their lower costs, ease and flexibility of implementation. Additionally, 802.11b wireless networks allow a wide range of mobile data devices such as laptop computers and personal digital assistance high-speed wireless access to critical information and applications resided on the aircrafts networks. Since 802.11b WLAN media is shared and traffic generated by other users will degrade the overall performance of the network. With the continual wide spread use of 802.11b WLAN, an aircraft in flight will experience network congestions and poor performance across all the frequency channels. The congestion and poor performance issues can be minimized by tracking the airborne wireless LAN using highly directional antenna and RF filtering. The method of tracking multiple 802.11 wirelesses LAN and the RF subsystem will be described. The applications of 802.11b wireless networks to man and unmanned aircrafts flight research will be discussed.

International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada / In our prior work [1] we proposed that network-centric data telemetry systems offer substantial improvements over traditional serial data telemetry systems. This paper is a follow up to that work and is also a companion to our experimentation paper [2]. In network-centric telemetry systems, there can be many infrastructure sites that form the network’s ad hoc communications paths, and there can be many fast-moving nodes, e.g., munitions, which enter the network, generate telemetry data, and exit the network. As the geographic size of such data telemetry networks grows, constraints on link margin will typically preclude a one-to-one matching of ground-based infrastructure sites to airborne, fast-moving nodes. That is, the fast-moving nodes will traverse distances that will require the mobile node to change which specific ground node it communicates with to transfer telemetry data. This paper describes an analytic model for the generic process of a fast moving node entering a wireless network and the associated handoffs of that node among ground stations as the fast mover traverses the spatial region covered by the wireless network. Our analysis and associated worst-case example demonstrate that wireless networking technology can handle the stress of rapidly managing connectivity to high-speed nodes for effective telemetry data extraction.

International Telemetering Conference Proceedings / October 21, 2002 / Town & Country Hotel and Conference Center, San Diego, California / A Wireless Local Area Network (WLAN) based system called 2-Way Robust Acquisition of Data (2-RAD) is being developed to telemeter data from a number of fast moving airborne platforms to ground collection points distributed over a large test range. The Johns Hopkins University Applied Physics Laboratory (JHU/APL) is analyzing a 2-RAD prototype currently in operation at the U.S. Army Yuma Proving Ground (YPG) that uses an IEEE 802.11b WLAN infrastructure. Preliminary analysis efforts at JHU/APL indicate that the Doppler shift from fast movers, and the system radio link margin, do not preclude IEEE 802.11b from being used for 2 -RAD.

Generally, collisions between packets are undesired in wireless networks. We design this scheme, Cooperative Jamming in Wireless Networks (CJWN), to make use of collision to protect secret DATA packets from being sniffed by a nearby eavesdropper. We are intending to greatly increase the Packet Error Rate (PER) at the eavesdropper when the PER at the receiver is maintained at an acceptable level. This scheme is not intended to completely take the place of various encryption/decryption schemes which are working based on successfully received packets. Adding CJWN to the popular CSMA/CA adopted in IEEE 802.11 will add more security even the key for encryption/decryption is already exposed. Because the overhead of CJWN is very big, we do not suggest using it on every transmission. When some secret packets have a high requirement of confidentiality, CJWN is worth trying at the cost of throughput performance and power.

El presente trabajo de tesis se ha desarrollado en cinco capítulos mediante la descripción de la tecnología WIFI y sus aplicaciones mediante el estándar 802.11b. En el Capítulo 1 se describe la tecnología inalámbrica,su funcionamiento,arquitectura y los protocolos involucrados en la performance de las tramas características asi como la seguridad en las wlan. En el Capítulo 2 se abordarán las ventajas y desventajas, planificación de las frecuencias,soluciones indoor,outdoor y los diferentes componentes de una red inalámbrica. En el Capítulo 3 se desarrollara con detalle un proyecto de aplicación de un enlace inalámbrico del modo bridge usando el estándar 802.11b en los locales comercial y central en la Empresa Municipal de Agua Potable y Alcantarillado de San Martín S.A. detallándose las etapas de dicho proyecto,pruebas,ingeniería del proyecto,análisis indoor y outdoor.Asimismo se plantean una serie de actividades que verificarán el desempeño de las redes construidas junto con los costos de las etapas respectivas. En el Capítulo 4 se desarrollara el estudio de factibilidad del proyecto y los factores a considerar como tambien el análisis DOFA como criterio de decisión en la implementación y su justificación financiera teniendo como proyección 5 años para cumplir las metas específicas de la empresa. En el Capítulo 5 se desarrollan las conclusiones y recomendaciones correspondientes así como los anexos correspondientes a las soluciones UMA y la normatividad vigente en nuestro país.

<p>This thesis investigates the IEEE 802.11b standard that describes radio communication for networks. The standard is carefully explained and the limitations of the standard are presented. To put the system in its context and to study the effects from the frequency translation, surrounding areas such as radio propagation and networks in general are presented. For radio communications the carrier frequency gives the basic properties for the application, long distance communication uses low frequencies and the opposite for short-range communication. The report investigates the possibilities to translate the frequency for an IEEE 802.11b system to move the limits of IEEE 802.11b Three alternative solutions are compared. A final solution evolves from one of them. The resulting solution is based on existing hardware and is ready for testing. One major conclusion is that 802.11b is a well developed standard where the development of the hardware is focussed on the physical size. This miniaturization makes alteration more complex. Finally other interesting wireless techniques that could give the desired properties and other possible further work are presented.</p>