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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Trådlös kommunikation för Anybus

Heigren, Robert, Otterdahl, Björn January 2007 (has links)
<p>The industry struggles with problems concerning physical damage to wires</p><p>and communication in remote areas. Introducing a wireless network can</p><p>provide a solution to these issues. However, introducing wireless</p><p>communication comes with a whole new line of problems that will be</p><p>covered in this report. By utilizing the wireless communication standard</p><p>IEEE 802.11 a product can easily be integrated into an existing wired</p><p>Ethernet network (IEEE 802.3).</p><p>An introduction to the standard IEEE 802.11 and a summary of existing</p><p>products utilizing the standard for embedded systems will be given</p><p>throughout the report. This report also tries to explain key parameters for</p><p>wireless communication in an industrial environment.</p><p>This project also consists of a design and an implementation part, where the</p><p>chosen IEEE 802.11 standard will be integrated into the existing wired</p><p>Anybus-S Ethernet module from the company HMS Industrial Networks.</p><p>The integration part of the project has resulted in a working prototype called</p><p>Anybus-S Ethernet Wireless that utilizes the IEEE 802.11b/g standard for</p><p>transferring data.</p><p>The project has been really fun to participate in and it has been successful in</p><p>the terms that a working prototype exists, and the authors have gained the</p><p>knowledge in the subject as intended.</p>
22

Wireless Security, a practical guide

Gjercek, Albin, Andersson, Alexander January 2012 (has links)
Wireless networks are continuing to grow around the world due to the advantages it offers and all the different services that it provides. In networking environments where the communication goes through a wireless connection, the importance of protecting the private information is a very significant task for network administrators. Beside the great benefits from having this type of network, the major issue of wireless communications is the weak security it provides. Companies and business organizations are more and more involved with the use of wireless networks because of the flexibility, mobility and the scalability it offers, but they are also concerned about the consequences of having a weaker security to protect their expensive investments and information. This thesis discusses the issues behind the security of wireless networks. It explains the background of the wireless networks and describes how the different security algorithms and encryptions work. The authors of this thesis decided to present some of the possible attacks that could occur in wireless networks and also give some security solutions to help others protect their network. The group that worked together on this project had the idea of investigating how secure the actual wireless algorithms and encryptions are. The approach of finding the necessary information for presenting the results and conclusions was to perform penetration tests on wireless networks that were implemented with the three famous security algorithms of WEP, WPA and WPA2. The penetrations tests were performed in lab environments and in home networks with the use of cracking tools. The group used the open source Linux based distribution called BackTrack 5. This operating system provided the group the different cracking tools that would help them perform their investigation. The purpose of performing the penetration tests was to find out the vulnerabilities that each of the security algorithms poses and therefore be able to determine which of them offers the best protection to a wireless network. After the penetration tests were done, the group came up with some solutions by configuring a wireless network with the strongest security options. The solutions were aimed to help others how to configure a specific wireless network in a simple but effective way. The results indicated that the weakest security algorithm would present some major issues for a wireless network. It included a greater possibility of experiencing different network attacks by configuring a wireless network with a weak security algorithm. Overall, this thesis provided the group the necessary information that was beneficial for them to understand how strong a wireless network actually is, and how a penetration test was performed.
23

SoftMAC in Heterogeneous Wireless Network

Li, Jinsong 12 May 2008 (has links)
Wireless networks are growing exponentially by the steady improvement of its speed and quality. IEEE 802.11-based Wireless Local Area Networking (WLAN) has been developed for mobile computing devices in LANs, in a short and limited range. IEEE 802.16 Wireless Metropolitan Area Network (WMAN) is designed for a line-of-sight (LOS) distance with QoS capability. The IEEE 802.11 standard has a totally different MAC layer compared to the IEEE 802.16 standard, normally they will communicate at the Network Layer by switches or routers. This thesis investigates the major design requirements for SoftMAC design, and will demonstrate a prototype that can meet the design requirements. It proves the possibility and flexibility of using SoftMAC to connect and control Heterogeneous Wireless Network, in order to fulfill seamless handover among multiple heterogeneous wireless interfaces. We will show that by adding the proposed SoftMAC on top of the traditional MAC layer, the mobile station cannot only perform handover between access points, but also essentially open a door to a wider range of application and services.
24

WLAN Interface Management on Mobile Devices

Falaki, Mohammad Hossein January 2008 (has links)
The number of smartphones in use is overwhelmingly increasing every year. These devices rely on connectivity to the Internet for the majority of their applications. The ever-increasing number of deployed 802.11 wireless access points and the relatively high cost of other data services make the case for opportunistic communication using free WiFi hot-spots. However, this requires effective management of the WLAN interface, because by design the energy cost of WLAN scanning and interface idle operation is high and energy is a primary resource on mobile devices. This thesis studies the WLAN interface management problem on mobile devices. First, I consider the hypothetical scenario where future knowledge of wireless connectivity opportunities is available, and present a dynamic programming algorithm that finds the optimal schedule for the interface. In the absence of future knowledge, I propose several heuristic strategies for interface management, and use real-world user traces to evaluate and compare their performance against the optimal algorithm. Trace-based simulations show that simple static scanning with a suitable interval value is very effective for delay-tolerant, background applications. I attribute the good performance of static scanning to the power-law distribution of the length of the WiFi opportunities of mobile users, and provide guidelines for choosing the scanning interval based on the statistical properties of the traces. I improve the performance of static scanning, by 46% on average, using a local cache of previous scan results that takes advantage of the location hints provided by the set of visible GSM cell towers.
25

Mobile IP Handover for WLAN

Falade, Olumuyiwa, Botsio, Marcellus January 2010 (has links)
The past few years have seen great increases in the use of portable devices like laptops, palmtops, etc. This has also led to the dramatic increase demand on wireless local area networks (WLAN) due to the flexibility and ease of use that it offers. Mobile IP and handover are important issues to be considered as these devices move within and between different networks and still have to maintain connectivity. It is, therefore, imperative to ensure seamless mobile IP handover for these devices as they move about. In this thesis we undertake a survey to describe the real processes involved in mobile IP handover in WLAN environment for different scenarios. Our work also identifies individual sources of delay during the handoff process, the sum total of which makes up the total latency. Other factors that could militate against the aim of having a seamless handoff in an inter-subnet network roaming were also considered as well as some proposed solutions. These factors are security, packet loss and triangle routing.
26

CMOS Power Amplifier for IEEE 802.11g/n standard (2.4GHz) in 65nm process

Yousaf, Malik Muzammil January 2010 (has links)
Today, the mobile communication systems can be found everywhere due to thelow cost and high degree integration level which is achievable with CMOS. Theuser can use a number of applications using only one device. The transmitteris one of the main blocks in communication systems for transmitting the signal,where the RF power a mplifier (PA) amplifies the RF signal to the r equiredoutput power so that signal can reach the r eceiver. Nowadays mostly transmitteremploys such modulation schemes which have high data rate and to amplify suchsignals, a linear PA is required. The efficiency of the PA should also be high, sothat it can provide high output power to load without consuming much poweritself.This thesis work describes the “CMOS Power Amplifier for IEEE 802.11g/nstandard (2.4GHz) in 65nm process”. The PA is a two stage amplifier biasedin Class AB mode with LC type input matching. The inter-stage matching iscarried out by the RF choke of the driver stage and the input capacitance of thepower stage. The output of the PA is power matched to the load. A linearizingtechnique is implemented to make PA more linear. The simulation results showsthat the designed PA gives 1dB compression point of +23.36dBm, a gain of26.82dB, a power added efficiency of 30%, a linear current of 122.30mA providing18dBm power to load and saturated output power of 24.45dBm.
27

Trådlösa nät och 3G för funktionshindrade

Diskay, Sebastian January 2003 (has links)
Genom hela arbetet har enkelhet och användbarhet varit ledorden. Detta för att man ska kunna implementera tjänster för en relativt liten målgrupp utan att behöva göra större investeringar. I linje med detta har möjligheter för att kunna erbjuda tjänsten till en större målgrupp och därmed få ned kostnaden per användare eftersökts. Rapporten börjar med en studie av 3G, WLAN och Bluetooth för att läsaren ska få en grund i de tekniker på vilka tjänsterna skulle kunna implementeras. Sedan diskuteras dagens tjänster och vilka önskemål om tjänster som framkommit från diskussioner med olika parter. Slutligen exemplifieras ett antal tjänster som skulle kunna tillämpas på dagens tekniker. Efter att ha läst rapporten skall läsaren ha fått en uppfattning hur mobila tjänster med hög överföringshastighet bör utformas för att underlätta kommunikation för funktionshindrade.
28

Implementation of an IEEE 802.11a transmitter in VHDL for Altera Stratix II FPGA

Brännström, Johannes January 2006 (has links)
The fast growth of wireless local area networks today has opened up a whole new market for wireless solutions. Released in 1999, the IEEE 802.11a is a standard for high-speed wireless data transfer that much of modern Wireless Local Area Network technology is based on. This project has been about implementing the transmitter part of the 802.11a physical layer in VHDL to run on the Altera Stratix II FPGA. Special consideration was taken to divide the system into parts based on sample rate. This report contains a brief introduction to Orthogonal Frequency Division Multiplexing and to the IEEE 802.11a physical layer as well as a description of the implemented system.
29

SoftMAC in Heterogeneous Wireless Network

Li, Jinsong 12 May 2008 (has links)
Wireless networks are growing exponentially by the steady improvement of its speed and quality. IEEE 802.11-based Wireless Local Area Networking (WLAN) has been developed for mobile computing devices in LANs, in a short and limited range. IEEE 802.16 Wireless Metropolitan Area Network (WMAN) is designed for a line-of-sight (LOS) distance with QoS capability. The IEEE 802.11 standard has a totally different MAC layer compared to the IEEE 802.16 standard, normally they will communicate at the Network Layer by switches or routers. This thesis investigates the major design requirements for SoftMAC design, and will demonstrate a prototype that can meet the design requirements. It proves the possibility and flexibility of using SoftMAC to connect and control Heterogeneous Wireless Network, in order to fulfill seamless handover among multiple heterogeneous wireless interfaces. We will show that by adding the proposed SoftMAC on top of the traditional MAC layer, the mobile station cannot only perform handover between access points, but also essentially open a door to a wider range of application and services.
30

WLAN Interface Management on Mobile Devices

Falaki, Mohammad Hossein January 2008 (has links)
The number of smartphones in use is overwhelmingly increasing every year. These devices rely on connectivity to the Internet for the majority of their applications. The ever-increasing number of deployed 802.11 wireless access points and the relatively high cost of other data services make the case for opportunistic communication using free WiFi hot-spots. However, this requires effective management of the WLAN interface, because by design the energy cost of WLAN scanning and interface idle operation is high and energy is a primary resource on mobile devices. This thesis studies the WLAN interface management problem on mobile devices. First, I consider the hypothetical scenario where future knowledge of wireless connectivity opportunities is available, and present a dynamic programming algorithm that finds the optimal schedule for the interface. In the absence of future knowledge, I propose several heuristic strategies for interface management, and use real-world user traces to evaluate and compare their performance against the optimal algorithm. Trace-based simulations show that simple static scanning with a suitable interval value is very effective for delay-tolerant, background applications. I attribute the good performance of static scanning to the power-law distribution of the length of the WiFi opportunities of mobile users, and provide guidelines for choosing the scanning interval based on the statistical properties of the traces. I improve the performance of static scanning, by 46% on average, using a local cache of previous scan results that takes advantage of the location hints provided by the set of visible GSM cell towers.

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