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The IEEE 802.11 standard has been widely adopted as a Wireless LAN (WLAN) technology. This widespread proliferation of the technology has lead to an increase in the number of users taking advantage of so-called "hot-spots" which leads to an increased demand on bandwidth provided by Access Points (APs) in the hot-spot. The logical solution is to deploy more overlapping access points in the same coverage area, thus increasing the capacity of the system by providing load balancing services. However, when a hot-spot is located in an outdoor environment, it becomes difficult to provide the AP with power which is traditionally carried over wired links thus causing the service provider to incur additional costs, not to mention the impossibility in some cases of delivering power to the AP. This problem can be overcome by using solar-panel powered APs which we will refer to as solar nodes (SNs). In this thesis we examine the load-balancing problem that arises when two or more SNs are co-located in the same coverage area. We propose and evaluate two algorithms for efficiently distributing the load among them (transferring stations (STAs) from SN to neighboring SNs) and increasing their lifetime by using power saving schemes that co-ordinate the wake/sleep patterns of the SNs based on traffic load. Finally, a Connection Admission Control (CAC) function is proposed that the SN should use in order to provide controlled access to services. We demonstrate through simulations that our proposals can significantly reduce the hardware requirements and cost of SNs and improve the service perceived by STAs in terms of transmission delay. / Thesis / Master of Applied Science (MASc)

Yes / This study presents a wideband multiple-input-multiple-output (MIMO) antenna for Wifi/WLAN/LTE applications. The antenna consists of two triangular patches as the radiating elements placed orthogonally to each other. Two T-slots and a rectangular slot were etched on the ground plane to improve return loss and isolation. The total dimension of the proposed antenna is 30 x 30 mm2. The antenna yields impedance bandwidth of 101.7% between 2.28 GHz up to 7 GHz with a reflection coefficient of < -10 dB, and mutual coupling of < -14 dB. The results including S-Parameters, MIMO characteristics with analysis of envelope correlation coefficient (ECC), total active reflection coefficient (TARC), capacity loss, channel capacity, VSWR, antenna gain and radiation patterns are evaluated. These characteristics indicate that the proposed antenna is suitable for MIMO wireless applications.

Wireless network devices, especially in ad hoc networks, are typically battery-powered. The growing need for energy efficiency in wireless networks, in general, and in mobile ad hoc networks (MANETs), in particular, calls for power enhancement features. The goal of this dissertation is to extend network lifetime by improving energy utilization in MANET routing. We utilize the ability of wireless network interface cards to dynamically change their transmission power, as well as the ability of wireless devices to read the remaining battery energy of the device to create a table of what we term "reluctance values," which the device uses to determine how to route packets. Choosing routes with lower reluctance values, on average and with time, leads to better utilization of the energy resources of the devices in the network. Our power-aware scheme can be applied to both reactive and proactive MANET routing protocols. As examples and to evaluate performance, the technique has been applied to the Dynamic Source Routing (DSR) protocol, a reactive routing protocol, and the Optimized Link State Routing (OLSR) protocol, a proactive routing protocol. Simulations have been carried out on large static and mobile networks. Results show improvements in network lifetime in static and certain mobile scenarios. Results also show better distribution of residual node energies at the end of simulations, which means that the scheme is balancing energy load more evenly across network nodes than the unmodified versions of DSR and OLSR. Average change in energy over time in the unmodified protocols show a steady increase with time, while the power-aware protocols show an increase in the beginning, then it levels for sometime before it starts to decrease. The power-aware scheme shows improvements in static and in coordinated mobility scenarios. In random mobility the power-aware protocols show no advantage over the unmodified protocols. / Ph. D.

Internetworking third generation (3G) technologies with wireless LAN (WLAN) technologies such as Universal Mobile Telecommunication Systems (UMTS) and IEEE 802.11, respectively, is an emerging trend in the wireless domain. Its development was aimed at increasing the UMTS network'­s capacity and optimizing performance. The increase in the number of wireless users requires an increase in the number of smaller WLAN cells in order to maintain an acceptable level of QoS. Deploying smaller cells in areas of higher mobility (e.g., campuses, subway stations, city blocks, malls, etc.) results in the user only spending a short period of time in each cell, which significantly increases the rate of handoff. If the user does not spend sufficient time in the discovered WLAN's coverage area, the application cannot benefit from the higher data rates. Therefore, the data interruption and performance degradation associated with the handoff cannot be compensated for. This counters the initial objective for integrating heterogeneous technologies, thus only handoffs that are followed by a sufficient visit to the discovered WLAN should be triggered. The conventional RF-based handoff decision method does not have the necessary means for making an accurate decision in the type of environments described above. Therefore, a location-aided handoff decision algorithm was developed to prevent the triggering of handoffs that result from short visits to discovered WLAN's ­ coverage area. The algorithm includes a location-based evaluation that runs on the network side and utilizes a user's location, speed, and direction as well as handoff-delay values to compute the minimum required visit duration and the user'­s trajectory. A WLAN coverage database is queried to determine whether the trajectory's end point falls within the boundaries of the discovered WLAN's coverage area. If so, the mobile node is notified by the UMTS network to trigger the handoff. Otherwise, the location-based evaluation reiterates until the estimated trajectory falls within the boundaries of the discovered WLAN'­s coverage area, or the user exits the coverage area. By taking into consideration more then merely RF-measurements, the proposed algorithm is able to predict whether the user'­s visit to the WLAN will exceed the minimum requirements and make the decision accordingly. This allows the algorithm to prevent the performance degradation and cost associated with unbeneficial/unnecessary handoffs. / Master of Science

Traditionally medium access control protocols for ad hoc networks have been designed for nodes using omni directional antennas. Through the use of directional antennas, it is possible to obtain higher efficiency. In this thesis we investigate the impact of these antennas on aggregate throughput and end-to-end delay. The use of omni-directional antennas not only results in lower power efficiency, but also decreases network efficiency due to interference caused by the transmission of packets in undesired directions. This thesis explores the effect of using smart antennas and proposes a signaling mechanism for forming the extended links using the network layer. For the performance assessment of the wireless networks using directional antennas, baseline models of phased array antenna and channel have been developed using the discrete event simulator OPNET ModelerTM 8.0. Simulation scenarios have been created for single hop as well as multihop networks. From the results of the simulation we observe that although the nodes forming the extended link experience decrease in end-to-end delay, the data successfully transmitted using extended link is correlated to the spatial distribution of nodes. / Master of Science

Made available in DSpace on 2016-04-04T18:31:21Z (GMT). No. of bitstreams: 1 Marcelo Aparecido Morales.pdf: 2213720 bytes, checksum: 6858d1301ee70451e07970bdb465607e (MD5) Previous issue date: 2008-02-15 / The IEEE 802.11 wireless local area network presents a MAC anomaly when stations with different bit rates are connected in the same Access Point. Stations with high SNR have worst performance than stations with low SNR. This condition is worse in PWLANs (Public Wireless Local Area Network) with users connecting with different bit rates. This paper proposes a policy that uses the SNR and the condition of propagation to control users Contention Window. With this policy it is possible to control the Bit Rate, which is not possible in the 802.11 networks. / Redes 802.11 apresentam uma anomalia quando existem esta??es com diferentes taxas conectadas a um mesmo ponto de acesso. Esta??es com boa SNR (Signal-to-Noise Rate) obt?m um desempenho pior que esta??es com pior SNR. Esta condi??o ? esperada de forma agravada em redes p?blicas com v?rios usu?rios se conectando a diferentes taxas. Neste trabalho ? proposta uma pol?tica atrav?s da varia??o da janela de conten??o, levando em considera??o a SNR e a condi??o de propaga??o do local. Com a pol?tica a ser apresentada ? poss?vel controlar a taxa de transmiss?o em fun??o da SNR, criando uma possibilidade n?o oferecida pela rede 802.11.

<p>This master’s thesis investigates the technology and security awareness associated with wireless networks (WLAN). It has been stated by the media and theories that many wireless networks are unprotected. This has sparked an interest to investigate the phenomenon in the Jonkoping region. The study is based on the following research questions:</p><p>- What security weaknesses are present with the WLAN-technology and how can these be avoided?</p><p>- How does the wireless infrastructure in the Jonkoping region look like?</p><p>- Why do companies implement the WLAN-technology?</p><p>- Are the companies aware of the risks involved with WLAN?</p><p>We conducted this study in three steps; the first step was to hack a wireless network in a controlled environment in order to investigate the weaknesses of the commonly used security measures. The second step of the study was to scan the wireless networks in Jonkoping, Gnosjo and Nassjo in order to create a picture of the wireless infrastructure of the region. The third step of the study was to contact companies that we found in the second step for interviews to investigate their awareness of the technology and its weaknesses.</p><p>We found that WLANs and their security measures have weaknesses. The commonly used WEP encryption can quite easily be broken and can lure users into a false sense of security. The study shows that companies are aware of this weakness, but use the encryption be-cause it offers a good level of usability and security. It is a compromise between usability and security. Usability is one of the major factors for companies when implementing wireless networks, companies strive for mobility, easy access and ease of use, which the WLAN technology offers. This has lead to an extended wireless infrastructure in cities within the region where one, with ease, can find wireless networks outside buildings. We have noticed an increase in the security awareness as our empirical findings differ from earlier research conducted in other cities. When these studies are compared you can see a trend where the number of unprotected networks decreases. Our contribution to increased wireless security is a checklist of possible security measures to minimize the security threats.</p> / <p>Denna magisteruppsats undersöker tekniken och säkerhetsmedvetandet gällande trådlösa nätverk (WLAN). Då det tidigare uppmärksammats i media och teori att många trådlösa nätverk står oskyddade har detta skapat intresse att undersöka fenomenet i Jönköpingsregionen. Studien baseras på följande frågeställningar:</p><p>- Vilka säkerhetsluckor finns i WLAN och hur kan dessa undvikas?</p><p>- Hur ser WLAN-infrastrukturen ut i Jönköpingsregionen?</p><p>- Varför implementerar företag WLAN-tekniken?</p><p>- Är företag medvetna om riskerna med trådlösa nätverk?</p><p>För att skapa en helhetsbild har vi genomfört studien i tre steg varav vi, i det första steget, genomfört dataintrång i en kontrollerad miljö för att undersöka svagheterna med säkerhetsfunktionerna som används i trådlösa nätverk. I det andra steget undersökte vi med hjälp av bärbar dator trådlösa nätverk i Jönköping, Gnosjö och Nässjö. Detta för att skapa oss en uppfattning om hur WLAN-infrastrukturen ser ut i dagsläget. Steg tre innebar intervjuer med företag som vi funnit i samband med steg två rörande deras medvetenhet om tekniken och dess brister.</p><p>Teorin och vår empiri gav oss underlag att dra slutsatser utifrån våra frågeställningar. Vi fann att WLAN och dess säkerhetsfunktioner har vissa sårbarheter. Den mest förekommande krypteringstekniken, WEP, kan dekrypteras tämligen enkelt och kan vagga in användarna i en falsk säkerhet. Studien visar att företagen är medvetna om detta, men att det handlar om en medveten kompromiss mellan användarvänlighet och säkerhet. Användarvänligheten står till grund för varför företagen väljer att implementera den trådlösa tekniken. Företag eftersträvar mobilitet, smidighet och enkel access, vilket den trådlösa tekniken erbjuder. Detta har lett till en utökad trådlös infrastruktur i städer runtom i regionen där man med lätthet kan hitta trådlösa nätverk utanför byggnader. Vi har noterat ett ökat säkerhetsmedvetande då våra empiriska resultat skiljer sig något från tidigare undersökningar i andra städer. När dessa ställs mot varandra anar man en trend där antalet oskyddade trådlösa nätverk minskar. Vårt bidrag till ökad trådlös säkerhet är en checklista med möjliga åtgärder för att minimera säkerhetsriskerna.</p>

Pagrindiniu įmonės tikslu laikomas įmonės vertės didinimas gali būti realizuojamas plečiant rinkos dalį, didinat parduodamų prekių ar paslaugų kiekį, taip pat didinant darbo organizavimo efektyvumą įmonėje. Vienas iš efektyvumo didinimo įmonėje sprendimų yra bevielio kompiuterių tinklo įmonėje diegimas. Naudojant bevielį kompiuterių tinklą pasiekiamas didesnis personalo mobilumas ir darbo efektyvumas, kai reikiamą informaciją darbuotojas gali gauti būdamas bet kurioje įmonės vietoje. Darbe atlikta bevielio tinklo diegimo metodų teorinė analizė, pasiūloma bevielio tinklo diegimo vertinimo metodika ir atliekamas metodikos taikymo tyrimas.Darbe pateikiama bevielio tinklo diegimo įmonėje metodika leidžia apskaičiuoti mobilumo naudą įmonei per papildomos vert���s sukūrimą ir kaštų sumažinimą, bei parinkti tinkamą bevielio tinklo architektūros ir saugumo sprendimus, atsižvelgiant į įmonės poreikius. Pristatomas modelis, leidžiantis įvertinti bevielio tinklo teikiamą naudą įmonėje. Bevielio kompiuterių tinklo architektūrinių sprendimų pritaikymo įmonei metodika formuluojama, remiantis atliktų eksperimentinių tyrimų rezultatais. / The main goal for a company is to increase its value which can be achieved by expanding the market share, increasing sales volume of its goods and services, improving labour productivity. One of the improvements aiming at achieving labour productivity is the implementation of wireless computer network. The use of wireless computer network gives a higher degree of mobility and efficiency for staff within the company, in particular when employee needs to access the information from any place in the territory of a company. This work contains from performed theoretic analysis of implementation methods of wireless network, the suggested methodology of Wireless Network evaluation and performed investigation of realised methodology of Wireless Network implementation in the company. The paper presents the methodology of wireless networks implementation in a company, evaluates the efficiency of wireless networks and suggests the possible architectural and security solutions for wireless networks implementation. Further more, the presented methodology enables to evaluate the benefits of mobility, in particular for added value creation and costs reduction, and allows choosing the appropriate architectural and security solutions of wireless computer network. The presented methodology is based on the results of experimental research.