The principal objectives of this research are: to investigate the performance of different fingerprint-based WiFi Indoor Positioning Systems (IPS), analyse historical long-term data signals, detection of signal change points and outliers; then present an enhanced method that generates temporal based fingerprints. The proposed method consists of analysing signal strength profiles over time and detecting points at which the profile behaviour changes. This methodology can be used to dynamically adjust the fingerprint based on environmental factors, and with this select the relevant Wireless Access Points (WAPs) to be used for fingerprinting. The use of an Exponentially Weighted Moving Average (EWMA) Control Chart is investigated for this purpose. A long-term analysis of the WiFi scenery is presented and used as a test-bed for evaluation of state-of-the-art fingerprinting techniques. Data was collected and analysed over a period of 18 months, with over 840 different WAPs detected in over 77,000 observations covering 47 different locations of varying characteristics. A fully functional IPS has been developed and the design and implementation is described in this thesis. The system allows the scanning and recording of WiFi signals in order to define the generation of temporal fingerprints that can create radio-maps, which then allow indoor positioning to occur. This thesis presents the theory behind the concept and develops the technology to create a testable implementation. Experiments and their evaluation are also included. Based on the timestamp experiments the proposed system shows there is still room level accuracy, with a reduction in radio-map size.

The effectiveness of location aware applications is dependent on the accuracy of the supporting positioning system. This work evaluates the accuracy of an indoors 802.11 positioning system based on signal strength fingerprinting. The system relies on an empirical survey of signal strength prior to positioning. During this survey, signal strength recordings are made at a set of positions across the environment. These recordings are used as training data for the system during positioning. In this thesis, two surveying methods, five positioning algorithms, and two spatial output averaging methods are trialled. Accuracy is determined by empirical testing in two separate environments: a 100m square domestic house and the 1,333m square third floor of the University of New South Wales Computer Science and Engineering building. In the two environments, the lowest mean distance errors are 1.25m and 2.86m respectively.

This thesis examines the problem of using 802.11 hotspots for vehicular Internet access. In this access paradigm, a user in a vehicle performs batch transfers by opportunistically communicating with roadside 802.11 access points while driving along a highway. Despite the short connection duration, a significant amount of data can be transferred. Because complete coverage is not needed, this method of Internet access provides a low-cost alternative to using cellular technology for applications that can tolerate some delay and require large data transfer such as sending or receiving music, movies, or digital photographs. Although vehicular opportunistic connections offer the potential to transfer a large of amount of data, utilizing this potential is non-trivial because existing transport and data-link layer network protocols were not designed for this use. This thesis presents an experimental analysis of transport and data-link layer protocol operation at a level of detail not previously explored. We identify ten problems that cause a reduction of up to 50% of the amount of data that could have been transferred in this scenario. Our primary finding is that transmission errors during connection setup and inadequate MAC data rate selection are the main causes of the under-utilization of the connection. Based on these findings we make preliminary recommendations for best practices for using vehicular opportunistic connections. In particular, we argue that overall throughput could be significantly improved if environmental information was available to the lower layer network protocols.

This thesis examines the problem of using 802.11 hotspots for vehicular Internet access. In this access paradigm, a user in a vehicle performs batch transfers by opportunistically communicating with roadside 802.11 access points while driving along a highway. Despite the short connection duration, a significant amount of data can be transferred. Because complete coverage is not needed, this method of Internet access provides a low-cost alternative to using cellular technology for applications that can tolerate some delay and require large data transfer such as sending or receiving music, movies, or digital photographs. Although vehicular opportunistic connections offer the potential to transfer a large of amount of data, utilizing this potential is non-trivial because existing transport and data-link layer network protocols were not designed for this use. This thesis presents an experimental analysis of transport and data-link layer protocol operation at a level of detail not previously explored. We identify ten problems that cause a reduction of up to 50% of the amount of data that could have been transferred in this scenario. Our primary finding is that transmission errors during connection setup and inadequate MAC data rate selection are the main causes of the under-utilization of the connection. Based on these findings we make preliminary recommendations for best practices for using vehicular opportunistic connections. In particular, we argue that overall throughput could be significantly improved if environmental information was available to the lower layer network protocols.

Multicast is an effective technology to save network bandwidth while transmitting data packets in WiFi networks. However, it lacks of a mechanism to recover lost packets. When interference or congestion occurs in wireless networks, the receiver cannot receive complete data. In this Thesis, we propose a multicast retransmission mechanism which integrates NACK in WiFi networks. Also, the sender can dynamically adjust retransmission parameters according to the network status reported from the receiver. To demonstrate our proposed mechanism, three parts are implemented on the Linux platform. First, the RTP header is added in each packet and the buffer is maintained in both the sender and the receiver before the sender can transmit data. Second, a module is installed in the wireless card driver to examine the CRC errors caused by interference. Then the sender can be notified by NACK such that the sender may know the reasons of packet loss and the numbers of dropped packets. Third, the sender utilizes RTCP to calculate RTT and derive RTO. The retransmission time is calculated based on RTO, interferences, and congestion. Finally, our measurement results show that the sender can effectively use multicast retransmission according to various background traffics. Besides, the number of retransmitted packets can be significantly reduced.

SAS is the leading airline in Scandinavia, and with the keywords comfort, safety and punctuality they look to provide their customers with an easy way to travel. In order to obtain this they have equipped many of their aircrafts with wireless networks (WiFi). To ensure continued airworthiness a method was required for investigating the electromagnetic compatibility of new components to be installed on the aircrafts, in other words whether or not they were at risk of interference from the wireless network and the portable devices connected to it. Earlier this had been taken care of by external companies, but SAS was looking for a way to do more of the work on their own in order to both simplify the procedure and decrease costs. In this project a model was developed for classification, analysis and follow-up documentation of a component to determine its compatibility status. This was achieved by studies of several documents where recommendations and regulations were listed. The information was then clarified and gathered into more easily observable forms, according to the wishes of SAS. The result of this work was presented in three documents. The first document described the three- step procedure which determined whether or not analysis was sufficient for a component, or if TPED testing was required. In the latter scenario, testing would still be performed externally. Document number two consisted of a component record where every tested and analysed component was to be listed after the compatibility status had been determined. Finally, document number three was a new chapter of SAS CAME-P regarding EMC management. / SAS är Skandinaviens ledande flygbolag. Med fokus på de tre nyckelorden komfort, säkerhet och punktlighet önskar de erbjuda sina resenärer ett enkelt sätt att resa. I enlighet med detta har företaget utrustat många av sina flygplan med trådlöst nätverk (WiFi). För att säkerställa en fortsatt flygduglighet krävdes en metod för att undersöka den elektromagnetiska kompatibiliteten för nya komponenter som så småningom skulle kunna komma att installeras ombord på dessa WiFi-utrustade flygplan, det vill säga huruvida komponenterna kunde tänkas störas av nätverket och de trådlösa enheter som kopplas upp mot detta. Tidigare skötte flygbolaget detta helt och hållet externt, men önskade nu en lösning för att göra en större del av arbetet på egen hand och på så vis både förenkla arbetet och minska kostnaderna. I detta arbete togs en modell fram för klassificering, analys och uppföljning av en komponent för att redogöra för dess kompatibilitetsstatus. Detta åstadkoms genom studie av ett flertal dokument där rekommendationer och riktlinjer stod listade. Informationen förtydligades sedan och sammanfördes i mer lättöverskådliga former enligt SAS önskemål. Resultatet av arbetet presenterades i tre dokument. Det första dokumentet beskrev den procedur i tre steg som avgjorde om analys var tillräcklig för att ansöka om myndighetsgodkännande eller om testning fortfarande var nödvändig. Om TPED-testning skulle bli aktuell skulle denna även i fortsättningen skötas externt. Dokument nummer två bestod av ett komponentregister där alla testade och analyserade komponenter skulle föras in när kompatibilitetsstatusen blivit känd. Det tredje och sista dokumentet var ett nytt kapitel till SAS CAME-P rörande EMC-hantering.

Wireless LANs are very common in any household or business today. It allows access to their home or business network and the Internet without using wires. Their wireless nature allows mobility and convenience for the user and that opens up a lot of new possibilities in mobile devices such as smartphones and tablets. One application that makes use of wireless LANs is positioning, which can be used in areas where Global Positioning Systems may have trouble functioning or not at all. However, a drawback of using wireless communication is that it is susceptible to eavesdropping and jamming. Once the wireless signal is jammed, an attacker can set up fake access points on different channels or frequencies to impersonate a legitimate access point. In this thesis, this attack is performed specifically to trick WiFi-based location services. The attack is shown to work on Skyhook, Google, Apple and Microsoft location services, four of the major location service providers, and on dual-band hardware. Some countermeasures to such an attack are also presented. The web is an important part of many people???s lives nowadays. People expect that their privacy and confidentiality is preserved when they use the web. Previously, web traffic uses HTTP which meant traffic is all unencrypted and can be intercepted and read by attackers. This is clearly a security problem so many websites now default to using a more secure protocol, namely HTTPS which uses HTTP with SSL, and forces the user to HTTPS if they connect to the no SSL protocol. SSL works by exchanging keys between the client and server and the actual data is protected using the key and the cipher suite that is negotiated between the two. However, if a network uses a proxy server, it works slightly different. The SSL connection is broken up into two separate ones and that creates the potential for man-in-the-middle attacks that allow an attacker to intercept the data being transmitted. This thesis analyzes several scenarios in which an adversary can conduct such a man-in-the-middle attack, and potential detection and mitigation methods.

Mobile phones have evolved from being devices just to make phone calls to become smartphones with added capabilities like surfing the network. Wireless communication has played a very important role in the evolution of smartphones. The work in this thesis aims to study the potential to reduce the energy consumption of the 3G communications by using a hybrid architecture. An idea first presented in the paper by Vergara and Nadjm-Tehrani [1]. This architecture consists of a group of nodes that communicate using WiFi or Bluetooth to forward their traffic using one node's 3G interface. In this thesis the named energy sharing scheme is implemented on Android mobile devices and experiments have been performed using a number of realistic traces to assess achievable gains and the energy footprint of the scheme itself. Even though communication technologies, screen features, multimedia capabilities, or processing power have been taken to the highest level, phones' batteries have not improved at the same speed. Nowadays battery lifetime has become a major issue with respect to cellular communication. With 3G communications Internet connection anytime and anywhere is provided to the terminals but this technology is optimized for peak performance whereas in underutilization it wastes a lot of energy. This makes it a big black hole from power consumption point of view when transmitting small amounts of data.

The effectiveness of location aware applications is dependent on the accuracy of the supporting positioning system. This work evaluates the accuracy of an indoors 802.11 positioning system based on signal strength fingerprinting. The system relies on an empirical survey of signal strength prior to positioning. During this survey, signal strength recordings are made at a set of positions across the environment. These recordings are used as training data for the system during positioning. In this thesis, two surveying methods, five positioning algorithms, and two spatial output averaging methods are trialled. Accuracy is determined by empirical testing in two separate environments: a 100m square domestic house and the 1,333m square third floor of the University of New South Wales Computer Science and Engineering building. In the two environments, the lowest mean distance errors are 1.25m and 2.86m respectively.

Trådlösa nätverk växer sig allt starkare och normen är nu mera att man i ett kontorslandskap eller hem skall kunna slå sig ner med sin laptop och jobba utan att behöva oroa sig om nätverksuttag eller sladdar. Även IP-telefoni och surfplattor är nu en naturlig del i flera användares dagliga liv, och just IP-telefoni ställer höga krav på det nätverk som denna är ansluten till. Därför har jag valt att i denna denna rapport titta närmare på den trådlösa tekniken 802.11 som är framtagen av standardiseringsorganisationen IEEE. Metoden jag valt att använda för att åstadkomma detta är att genomföra en mätning av ett befintligt trådlöst nät. Jag kommer därefter att undersöka denna data för att förhoppningsvis kunna lämna ett förslag på en bättre nätverksdesign. Som hjälpmedel för att genomföra denna mätning har jag utrustning från Ekahau, ett finsk företag vars huvudsyssla är just mätning, optimering och felsökning av trådlösa nät. Det jag kom fram till var att det tråd- lösa nätverket hade stora brister. Framförallt var täckning det stora bekymret, inte bara bristen på täckning utan ibland även för bra täckning vilket resulterat i sticky clients. Jag har därefter presen- terat en design som för att minimera kostnaderna och miljöpåverkan använder befintlig utrustning, dock kräver denna att det kompletteras med 9 stycken nya accesspunkter. / Wireless networks are growing ever more and the norm is now that in an office or home you can settle down with your laptop and work without having to worry about network outlets or wires. IP telephony and tablet are now more natural in many users daily lives, and especially IP telephony places high demands on the network to which it is connected. Therefore, I have chosen that in this report, look at the 802.11 wireless technology developed by the IEEE standardization organization. The method I chose to use to accomplish this is to perform a measurement of an existing wire- less network. I will then investigate this data in order to hopefully submit a proposal for a better network design. As a tool for carrying out this measurement, I have equipment from Ekahau, a Finnish company whose main aim is measurement, optimization and troubleshooting of wireless networks. What I found out was that the wireless network had major shortcomings. In particular, coverage was a matter of concern, not just the lack of coverage, but sometimes even for good cove- rage, resulting in sticky clients. I have then presented a design that, in order to minimize costs and environmental impact, uses existing equipment, but requires that it be supplemented with 9 new access points.