<p>Mobile payments are increasing in popularity in recent years. New mobile solutions are being developed in the form of new Internet capable mobile devices such as the IPhone and new wireless networks such as the LTE and WiMAX networks.</p><p>This report will present, explain and compare some of the most popular wireless networks that enable mobile payments, from a security point of view. The chosen networks are 3G with connection to GSM, and WLAN networks. The main security mechanisms involved in each network, and how they work will be studied. Security requirements and some of the most important threats each network faces will be presented and discussed. The main purpose of the report is to examine if mobile payments offer an acceptable level of security to the average user.</p>

<p>This thesis describes the interference problem between IEEE 802.11 and Bluetooth. These well established communication standards are often used together simultaneously. Since both standards operate in the ISM-band at 2.45 GHz, they interfere with each other. In addition to this, interference from e.g. microwave ovens, heating processes, electric motors and cordless phones also occurs on the ISM-band. Due to this interference problem, a model has been developed in MATLAB to further investigate these interferences and the effects for the user.</p><p>The interference is modelled using the well known Class-A model for impulsive noise. The interference model is parameterized in the model and therefore the noise source(s) is described by a set of parameters derived from real measurements. Models for IEEE 802.11 legacy/b and Bluetooth are based on work published on the user community of MATHWORKS. To get a measure of performance, results from the model are presented as BER (Bit Error Rates) and PER (Packet Error Rates). When Bluetooth is used as a voice link, sound quality can also be performance evaluated directly by simply listening to a voice output file. To be able to track down a specific problem cause, measuring tools have also been included in the model to gain insight into what is causing bit/packet error.</p><p>A model describing the interference problem has been developed describing the real world usage of the standards by the use of state machines. Due to the complexity of the problem, and also for the model to be user friendly, this thesis is not composed of a thorough mathematical derivation describing BER probability for different modulation forms. The derivations for these has already been done and is therefore summarized and compared to when the model is validated. The model has been developed as a proof of concept for further work to fully support the current and coming IEEE standards for IEEE 802.11 and Bluetooth.</p>

This paper is a study and comparison between the two Wireless LAN (WLAN) standards HiperLAN/2 and IEEE 802.11a. WLANs are used instead or together with ordinary LANs to increase mobility in for example an office. HiperLAN/2 is an European standard developed by ETSI and the IEEEs standard is American. A WLAN-card consists roughly of a Medium Access Control (MAC), Physichal layer (PHY) and an antenna. The antenna is the same for the different standards. Both standards operates at 5.4 GHz with a maximum transmission rate at 54 Mbit/s and they use OFDM to modulate the signal. This means that the physical layer in the two standards is similar. The differences between the standards are in the Medium Access Control (MAC) layer. HiperLAN/2 has a much more complex MAC since it is developed with the starting point in cellular phones. Therefore this MAC is not very similar to ETHERNET that is the protocol used by regular network. On the other hand it is built to be compatible with cellular phones and other applications. The 802.11a MAC is very much the same as in the 802.11b standard that is the most used standard at present. The difference is that 802.11a can send at much higher data rates. This MAC is build with starting point in ETHERNET so it has a similar interface to the computer. This makes it less complex. The different MACs can provide different services. The greatest difference is that 802.11a can use a distributed send mode where any STA can send if the medium is idle. This reminds a lot of ETHERNET but they use different methods to sense if the medium is idle. In HiperLAN/2 are all transmissions scheduled by the AP. 802.11a can operate in a similar way but at the moment this mode is not as fully developed as in HiperLAN/2. There are working groups in IEEE that works toward an improvement of 802.11a so it can use queues with different priorities, this is already implemented in HiperLAN/2. Another important issue in wireless environment is security. Both standards use encryption to protect their messages. The difference is that HiperLAN/2 changes their encryption key for every connection where 802.11a uses the same key the whole time. This gives HiperLAN/2 a better security with todays standard but thereare working groups dealing with implementing key-exchange functions and Kerberos use in 802.11a. Chapter 8 is a description of a program that we developed in C++. The program is used to monitor the different registers and ports a WLAN-card use. It is written for a 802.11b card and should be used together with Windows 2000. The source code can be found in appendix C.

Today’s wireless users expect great things from tomorrow’s wireless networks. These expectations have been fueled by hype about what the next generations of wireless networks will offer. The rapid increase of wireless subscribers increases the quality of services anytime, anywhere, and by any-media becoming indispensable. Integration of various networks such as CDMA2000 and wireless LAN into IP-based networks is required in these kinds of services, which further requires a seamless vertical handoff to 4th generation wireless networks. The proposed handoff algorithm between WLAN and CDMA2000 cellular network is implemented. The results of the simulation shows the behavior of the handoff and the time spent in WLAN or CDMA. The number of weak signal beacons determines whether a handoff is required or not. In this algorithm, traffic is classified into real-time and non real-time services.

Les xarxes d'àrea local sense fils (WLANs), principalment les basades en les diverses versions de les normes IEEE 802.11, i més concretament, aquelles operant en mode infraestructura (ús de punts d'accés o APs), són avui dia les tecnologies més populars per a l'accés ràdio de banda ampla a xarxes IP, ja sigui per a estendre petites xarxes LAN domèstiques (SOHO), o per a proporcionar accés d'Internet en espais públics. A més, amb l'arribada de productes amb el certificat Wi-Fi, els diferents fabricants de dispositius WLAN proporcionen un alt nivell d'interoperabilitat.No obstant això, la creixent densitat de punts d'accés WLAN ha començat a revelar els efectes negatius i les deficiències de les normes IEEE 802.11 inicials. Un dels factors clau del seu èxit, l'ús de la bandes de freqüència lliures (bandes ISM), és al mateix temps un dels seus grans inconvenients. Aquestes freqüències són de lliure accés al públic en general, i es defineixen dins d'una petita porció de l'espectre. En conseqüència, són generalment compartides entre diversos usuaris, dispositius de tecnologies diferents, etc.. A més, el control d'accés al medi definit per l'IEEE 802.11 (CSMA, o "escoltar abans de parlar") requereix una atenció especial a tots els problemes sorgits al voltant de les interferències.En aquest escenari, les xarxes WLAN IEEE no estan en condicions d'arribar a explotar tot el seu potencial. Malgrat aquest fet, unes polítiques intel·ligents sobre la gestió dels recursos ràdio (RRM) poden ajudar a reduir al mínim els efectes perjudicials de les interferències i d'una distribució desigual de la càrrega oferta. En aquesta tesi, es demostra que els mecanismes de RRM eficients són capaços de millorar notablement el rendiment d'una WLAN basada en l'IEEE 802.11.Aquesta tesi estudia la forma d'entendre els problemes de rendiment que són endèmics en les WLANs IEEE 802.11, així com les formes de minimitzar aquests efectes negatius per mitjà de la gestió de recursos ràdio. De fet, aquests problemes no són nous i han estat àmpliament estudiats des de l'aparició de xarxes de comunicacions mòbils, però les característiques particulars de les xarxes WLAN 802,11 requereixen nous enfocaments.Els mecanismes RRM en l'àmbit de les xarxes WLAN IEEE 802.11 són bàsicament destinats a reduir el grau de contenció i la interferència. Aquesta reducció es tradueix en una millor qualitat d'experiència (QoE), d'acord amb la percepció dels usuaris. Amb aquesta finalitat, RRM ha de proporcionar mecanismes eficients d'assignació de canals, algoritmes de selecció de modulació, control de potència i repartiment de càrrega. Atesa la naturalesa dinàmica de la propagació ràdio, i a causa de la mobilitat dels usuaris, els paràmetres que defineixen l'entorn sense fils varien amb el temps. Llavors, per tal de mantenir el rendiment en nivells acceptables, s'han de trobar mecanismes RRM que permetin una reconfiguració automàtica i dinàmica de la xarxa en resposta als canvis en el medi. En resum, podem construir el nostre escenari d'interès a partir de dispositius Wi-Fi intel·ligents capaços de cooperar, ja sigui de forma centralitzada o distribuïda, per tal de fer un millor ús dels minsos recursos ràdio.La nostra contribució als mecanismes RRM en xarxes WLAN s'inicia amb l'estudi i la caracterització de la interferència en l'àmbit particular de les xarxes IEEE 802.11. A continuació, desenvolupem un model de capacitat per a grans xarxes WLAN multi cel·la que té en compte tant l'efecte de la càrrega de la xarxa, com el de les interferències entre cel·les. El model també inclou l'efecte de l'adaptació automàtica de modulació que porten a terme molts dispositius. Aquestes estimacions de la capacitat són útils per a avaluar els beneficis d'un mecanisme RRM. Per exemple, aquestes estimacions són la base sobre la qual desenvolupem una innovadora solució per a la gestió de freqüències. Aquest mecanisme d'assignació de freqüències fa ús de tot l'espectre disponible (tant si es tracta de canals ISM solapats o no), ja que té en compte els efectes dels dos tipus d'interferència que trobem en xarxes IEEE 802.11: co-canal i per canal adjacent. Per tal de fer front a una distribució desigual de la càrrega, fet que es dóna típicament en els anomenats hotspots, es proposen dos mecanismes de repartiment de càrrega (un cop definit el concepte de càrrega): un enfocament distribuït gestionat per les estacions client, i un mecanisme de "cell breathing".Tots aquests mecanismes han de ser integrats en una arquitectura de gestió aglutinadora. En aquest sentit, s'han desenvolupat dues arquitectures de RRM: una arquitectura centralitzada, com a part del projecte UAMN, i un sistema distribuït. / WLANs, primarily the various versions of IEEE 802.11 standards, and more precisely, those operating in infrastructure mode, are nowadays the most popular technologies for providing broadband radio access to IP networks, whether to extend Small Office/Home Office (SOHO) network LANs or to provide Internet access in public places. Moreover, with the advent of Wi-Fi certified products, different competitive brands of WLAN devices are interoperable at a basic level of service.However, the increasing density of WLAN access points has started to reveal the negative effects and shortcomings of the original IEEE 802.11 standards. One of its key success factors, the use of unlicensed Industrial Scientific Medical (ISM) frequency bands, is at the same time one of its major drawbacks. These frequencies are freely available to the general public. On the other hand, such frequencies are defined within a small portion of the spectrum and are usually shared among several users. Besides, the medium access defined by the IEEE 802.11 (CSMA, or "listen before talk") requires a special attention to all interference issues.In this scenario, IEEE WLANs are unable to exploit all their potential. However, intelligent radio resource management (RRM) policies could be applied to minimize the harmful effects of interference and an uneven load distribution. Throughout this dissertation, it is shown that efficient RRM mechanisms are able to improve notably the performance of a legacy IEEE WLAN.This thesis explores ways of understanding the performance issues that are endemic to IEEE 802.11 WLANs, as well as ways of minimizing these negative effects by means of radio resource management. In fact, these problems are not new and have been studied extensively since the advent of mobile communications networks, but the particular characteristics of the 802.11 WLANs require new approaches.RRM mechanisms in the field of IEEE 802.11 WLANs are basically intended to reduce contention and interference. This reduction is translated into an improved Quality of Experience (QoE), as perceived by the users. To this end, RRM should provide efficient channel allocation mechanisms, modulation selection algorithms, power control and load balancing. Given the dynamic nature of radio propagation, and due to user mobility, the parameters that define the wireless environment vary in time. Therefore, in order to maintain the required performance, we should find mechanisms that allow a dynamic and automatic reconfiguration of the network in response to the changes in the environment. To sum up, we build our scenario of interest with intelligent Wi-Fi devices capable of cooperating either in a centralized or a distributed manner, in order to make a better use of the shared and scarce radio resources.Our contribution to RRM on WLANs starts with the study and characterization of interference in the particular field of IEEE 802.11 networks. Following, we develop a capacity model for large WLAN deployments that takes both the effect of carried traffic and inter-cell interference into account. The model also includes the effect of rate adaptation. These capacity estimations are useful to evaluate the benefits of a RRM mechanism, for example, it was used as the metric observed by a frequency management approach. This frequency assignment mechanism makes use of all the available spectrum (overlapping and non-overlapping ISM channels), since it takes the effects of both co-channel and adjacent-channel interference into account. In order to cope with the uneven load distribution usually found on hot-spots, two load balancing mechanisms are proposed after defining the concept of load: a client-driven approach, and a cell-breathing mechanism. All these mechanisms need to be integrated into a single architecture. In this regard, two radio resource management architectures are developed: a centralized architecture, as part of the UAMN project, and a distributed scheme.

The next-generation wireless communications have been envisioned to be supported by heterogeneous networks using various wireless access technologies. The popular cellular networks and wireless local area networks (WLANs) present perfectly complementary characteristics in terms of service capacity, mobility support, and quality-of-service (QoS) provisioning. The cellular/WLAN interworking is thus an effective way to promote the evolution of wireless networks. As an essential aspect of the interworking, resource allocation is vital for efficient utilization of the overall resources. Specially, multi-service provisioning can be enhanced with cellular/WLAN interworking by taking advantage of the complementary network strength and an overlay structure. Call assignment/reassignment strategies and admission control policies are effective resource allocation mechanisms for the cellular/WLAN integrated network. Initially, the incoming calls are distributed to the overlay cell or WLAN according to call assignment strategies, which are enhanced with admission control policies in the target network. Further, call reassignment can be enabled to dynamically transfer the traffic load between the overlay cell and WLAN via vertical handoff. By these means, the multi-service traffic load can be properly shared between the interworked systems. In this thesis, we investigate the load sharing problem for this heterogeneous wireless overlay network. Three load sharing schemes with different call assignment/reassignment strategies and admission control policies are proposed and analyzed. Effective analytical models are developed to evaluate the QoS performance and determine the call admission and assignment parameters. First, an admission control scheme with service-differentiated call assignment is studied to gain insights on the effects of load sharing on interworking effectiveness. Then, the admission scheme is extended by using randomized call assignment to enable distributed implementation. Also, we analyze the impact of user mobility and data traffic variability. Further, an enhanced call assignment strategy is developed to exploit the heavy-tailedness of data call size. Last, the study is extended to a multi-service scenario. The overall resource utilization and QoS satisfaction are improved substantially by taking into account the multi-service traffic characteristics, such as the delay-sensitivity of voice traffic, elasticity and heavy-tailedness of data traffic, and rate-adaptiveness of video streaming traffic.

Mobile payments are increasing in popularity in recent years. New mobile solutions are being developed in the form of new Internet capable mobile devices such as the IPhone and new wireless networks such as the LTE and WiMAX networks. This report will present, explain and compare some of the most popular wireless networks that enable mobile payments, from a security point of view. The chosen networks are 3G with connection to GSM, and WLAN networks. The main security mechanisms involved in each network, and how they work will be studied. Security requirements and some of the most important threats each network faces will be presented and discussed. The main purpose of the report is to examine if mobile payments offer an acceptable level of security to the average user.

The first part of the thesis consists of a theoretical overview of OFDM, the effects of different imperfections like carrier frequency offset, timing offset and phase noise followed by a short overview of the IEEE802.11a standard for WLAN. The second part consists of an overview of a number of different techniques for synchronization that have been published. A technique based on correlation in the time domain is chosen and implemented as a floaing-point model and later as a fixed-point model using Matlab, Simulink and Xilinx System Generator. The fixed-point model is then synthesized to an FPGA to verify that the design flow works and that a required clock frequency can be achieved.

Wireless communication is being developed in the last years day by day, there are several standards that talks about it. We are going to go through the IEEE standard 802.11 which talks about wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications. Looking this more carefully we will study MAC specifications and its environment. The work that ISY department at Institute of Technology of Linkoping University has proposed is to design a MAC sublayer implementation for WLANs using C language programming and testing it with the test environment called “test bench”. This test bench will simulate LLC sublayer and PHY layer, in this way, our MAC implementation will has to interact with it. Therefore we will simulate a wireless network where we are going to have a short number of stations and we are going to look at carefully the MAC sublayer response in an ad hoc network.

The next-generation wireless communications have been envisioned to be supported by heterogeneous networks using various wireless access technologies. The popular cellular networks and wireless local area networks (WLANs) present perfectly complementary characteristics in terms of service capacity, mobility support, and quality-of-service (QoS) provisioning. The cellular/WLAN interworking is thus an effective way to promote the evolution of wireless networks. As an essential aspect of the interworking, resource allocation is vital for efficient utilization of the overall resources. Specially, multi-service provisioning can be enhanced with cellular/WLAN interworking by taking advantage of the complementary network strength and an overlay structure. Call assignment/reassignment strategies and admission control policies are effective resource allocation mechanisms for the cellular/WLAN integrated network. Initially, the incoming calls are distributed to the overlay cell or WLAN according to call assignment strategies, which are enhanced with admission control policies in the target network. Further, call reassignment can be enabled to dynamically transfer the traffic load between the overlay cell and WLAN via vertical handoff. By these means, the multi-service traffic load can be properly shared between the interworked systems. In this thesis, we investigate the load sharing problem for this heterogeneous wireless overlay network. Three load sharing schemes with different call assignment/reassignment strategies and admission control policies are proposed and analyzed. Effective analytical models are developed to evaluate the QoS performance and determine the call admission and assignment parameters. First, an admission control scheme with service-differentiated call assignment is studied to gain insights on the effects of load sharing on interworking effectiveness. Then, the admission scheme is extended by using randomized call assignment to enable distributed implementation. Also, we analyze the impact of user mobility and data traffic variability. Further, an enhanced call assignment strategy is developed to exploit the heavy-tailedness of data call size. Last, the study is extended to a multi-service scenario. The overall resource utilization and QoS satisfaction are improved substantially by taking into account the multi-service traffic characteristics, such as the delay-sensitivity of voice traffic, elasticity and heavy-tailedness of data traffic, and rate-adaptiveness of video streaming traffic.