<p>The wide spread use of IEEE Wireless LAN 802.11 in battery operated mobile devices introduced the need of power consumption optimization while meeting Quality-of-Service (QoS) requirements of applications connected through the wireless network. The IEEE 802.11 standard specifies a baseline power saving mechanism, hereafter referred to as standard Power Save Mode (PSM), and the IEEE 802.11e standard specifies the Automatic Power Save Delivery (APSD) enhancement which provides support for real-time applications with QoS requirements. The latest amendment to the WLAN 802.11 standard is the IEEE 802.11n standard which enables the use of much higher data rates by including enhancements in the Physical and MAC Layer. In this thesis, different 802.11n MAC power saving and QoS optimization possibilities are analyzed comparing against existing power saving mechanisms.</p><p>Initially, the performance of the existing power saving mechanisms PSM and Unscheduled-APSD (UAPSD) are evaluated using the 802.11n process model in the OPNET simulator and the impact of frame aggregation feature introduced in the MAC layer of 802.11n was analyzed on these power saving mechanisms. From the performance analysis it can be concluded that the frame aggregation will be efficient under congested network conditions. When the network congestion level increases, the signaling load in UAPSD saturates the channel capacity and hence results in poor performance compared to PSM. Since PSM cannot guarantee the minimum QoS requirements for delay sensitive applications, a better mechanism for performance enhancement of UAPSD under dynamic network conditions is proposed.</p><p>The functionality and performance of the proposed algorithm is evaluated under different network conditions and using different contention settings. From the performance results it can be concluded that, by using the proposed algorithm the congestion level in the network is reduced dynamically thereby providing a better power saving and QoS by utilizing the frame aggregation feature efficiently.</p>

<p>This thesis describes the simulation of the proposed IEEE 802.11p Physical layer (PHY). A MATLAB simulation is carried out in order to analyze baseband processing of the transceiver. Orthogonal Frequency Division Multiplexing (OFDM) is applied in this project according to the IEEE 802.11p standard, which allows transmission data rates from 3 up to 27Mbps. Distinct modulation schemes, Binary Phase Shift Keying (BPSK), Quadrate Phase Shift Keying (QPSK) and Quadrature Amplitude modulation (QAM), are used according to differing data rates. These schemes are combined with time interleaving and a convolutional error correcting code. A guard interval is inserted at the beginning of the transmitted symbol in order to reduce the effect of Intersymbol Interference (ISI). The Viterbi decoder is used for decoding the received signal. Simulation results illustrate the Bit Error Rate (BER), Packet Error Rate (PER) for different channels. Different channel implementations are used for the simulations. In addition a ray-tracing based software tool for modelling time variant vehicular channels is integrated into SIMULINK. BER versus Signal to Noise Ratio (SNR) statistics are as the basic reference for the physical layer of the IEEE 802.11p standard for all vehicular wireless network simulations.</p>

<p>I datornätverk blir användandet av WLAN (trådlösa nätverk) allt vanligare tack vare sin smidighet. Det är framförallt bekvämare att använda trådlösa nätverk då man slipper allt kablage och ofta är oberoende av var man befinner sig för att använda nätverket. Trådlösa nätverk är dock inte helt problemfria. Den främsta anledningen till detta är att informationen färdas genom radiovågor istället för genom kablade nätverk. Detta gör att WLAN är i riskzonen för avlyssning, där informationen kan utsättas för obehörig åtkomst om den inte är väl skyddad. Detta problem är grunden till denna uppsats.</p><p>Den här uppsatsen är en utredning som har gått ut på att ta fram generella riktlinjer för hur myndigheter skall uppnå god säkerhet i WLAN. Anledningen till att vi ville ta fram generella riktlinjer åt myndigheter var på grund av en rapport vi fann genomförd av krisberedskapsmyndigheten (KBM) 2008. Denna uppmärksammade att myndigheter ofta hoppar på nya tekniker utan att ha tillräckligt kunskap nog om dem, och att säkerhetstänket ofta får låg prioritet vid införandet av nya system. Ytterligare en artikel skapade av KBM från 2007, pekar på att myndigheter även har bristande säkerhet i sina DNS-system.</p><p>Eftersom vi koncentrerade oss på WLAN funderade vi då på, om nu säkerhetstänket får så låg prioritet och är så dåligt ställt i myndigheternas DNS-system, hur är det då ställt med säkerheten i WLAN?</p><p>Vi konstaterade efter att vi gjort förfrågningar till flera myndigheter, att ytterst få myndigheter hade något WLAN eller planerade att införskaffa det. Anledning till detta tror vi var att myndigheter var skeptiska till att det går att få ett WLAN säkert och hade bristande kunskap inom området.</p><p>Vi tog fram de generella riktlinjerna genom en kvalitativ metodansats, där vi genomfört litteraturstudier, undersökning av myndigheters policys samt intervju av expert på WLAN.</p><p>Resultatet visade att myndigheter behöver både administrativa säkerhetsåtgärder, tekniska säkerhetsåtgärder samt en specifik fysisk säkerhetsåtgärd för att uppnå god säkerhet i WLAN.</p>

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The tremendous popularity of wireless technologies during the last decade has created a considerable expansion of wireless networks both in size and use. This fact, together with a great variety of mobile devices and numerous di®erent services that are becoming increasingly resourcedemanding, have attracted the attention of many researchers into the area of radio resource planning and optimization. Due to network complexity, these tasks require intelligent, automated approaches that are able to deal with many factors in order to enable design of high capacity networks with a high service quality at the lowest possible cost. This is a perfect application of optimization theory. In this thesis, mathematical optimization is considered as the main approach to designing and improving the performance of wireless networks such as Universal Mobile Telecommunications System (UMTS), Wireless Local Area Networks (WLANs) and ad hoc networks. Due to different underlying access technologies, the optimization goals, design parameters and system limitations vary by network type. Therefore, the goals of the presented work are to identify a relevant optimization problem for each type of network, to model the problem and to apply the optimization approach in order to facilitate wireless network planning and improve radio resource utilization. The optimization problems addressed in this thesis, in the context of UMTS networks, focus on minimizing the total amount of pilot power which, from the modeling point of view, is not just an amount of power consumed by a certain type of control signal, but also an indicator of the interference level in the network and means of controlling cell coverage. The presented models and algorithms enable °exible coverage planning and optimization of pilot power and radio base station antenna confiration in large networks. For WLANs, in the First part of the study, the access point placement and the channel assignment problems are considered jointly to maximize net user throughput and minimize co- and adjacent channel interference and contention. The second part of the study addresses the contention issue and involves, among the other decisions, optimization of access point transmit power. Due to the dynamic and infrastructureless nature of ad hoc networks, static resource planning is less suitable for this type of network. Two algorithmic frameworks which enable dynamic topology control for power-efficient broadcasting in stationary and mobile networks are presented. In both frameworks, the performance of the presented algorithms is studied by simulations.

Future Wireless Local Area Networks (WLANs) with high carrier frequencies and wide channels need a dense deployment of Access Points (APs) to provide good performance. In densely deployed WLANs associations of stations and handovers need to be managed more intelligently than today. This dissertation studies when and how a station should perform a handover and to which AP from a theoretical and a practical perspective. We formulate and solve optimization problems that allow to compute the optimal AP for each station in normal WLANs and WLANs connected via a wireless mesh backhaul. Moreover, we propose to use software defined networks and the OpenFlow protocol to optimize station associations, handovers and traffic rates. Furthermore, we develop new mechanisms to estimate the quality  of a link  between a station and an AP. Those mechanisms allow optimization algorithms to make better decisions about when to initiate a handover. Since handovers in today’s WLANs are slow and may disturb real-time applications such as video streaming, a faster procedure is developed in this thesis. Evaluation results from wireless testbeds and network simulations show that our architectures and algorithms significantly increase the performance of WLANs, while they are backward compatible at the same time.

Although evolving mobile technologies bring millions of users closer to the vision of information anywhere-anytime, device battery depletions hamper the quality of experience to a great extent. We argue that the design of energy-efficient solutions starts by energy-awareness and propose EnergyBox, a tool that provides accurate and repeatable energy consumption studies for 3G and WiFi transmissions at the user end. We recognize that the energy consumption of data transmission is highly dependable on the traffic pattern, and provide the means for trace-based iterative packet-driven simulation to derive the operation states of wireless interfaces. The strength of EnergyBox is that it allows to modularly set the 3G network parameters specified at operator level, the adaptive power save mode mechanism for a WiFi device, and the different power levels of the operation states for different handheld devices. EnergyBox enables efficient energy consumption studies using real data, which complements the device-dependent laborious physical power measurements. Using real application transmission traces, we have validated EnergyBox showing an accuracy range of 94-99% for 3G and 93-99% for WiFi compared to the real measured energy consumption by a 3G modem and a smartphone with WiFi.

As the demand of indoor Location-Based Services (LBSs) increases, there is a growing interest in developing an accurate indoor positioning and tracking system on mobile devices. The core location determination problem can be reformulated as a sparse natured problem and thus can be solved by applying the Compressive Sensing (CS) theory. This thesis proposes a compact received signal strength (RSS) based real-time indoor positioning and tracking systems using CS theory that can be implemented on personal digital assistants (PDAs) and smartphones, which are both limited in processing power and memory compared to laptops. The proposed tracking system, together with a simple navigation module is implemented on Windows Mobile-operated smart devices and their performance in different experimental sites are evaluated. Experimental results show that the proposed system is a lightweight real-time algorithm that performs better than other traditional fingerprinting methods in terms of accuracy under constraints of limited processing and memory resources.

As the demand of indoor Location-Based Services (LBSs) increases, there is a growing interest in developing an accurate indoor positioning and tracking system on mobile devices. The core location determination problem can be reformulated as a sparse natured problem and thus can be solved by applying the Compressive Sensing (CS) theory. This thesis proposes a compact received signal strength (RSS) based real-time indoor positioning and tracking systems using CS theory that can be implemented on personal digital assistants (PDAs) and smartphones, which are both limited in processing power and memory compared to laptops. The proposed tracking system, together with a simple navigation module is implemented on Windows Mobile-operated smart devices and their performance in different experimental sites are evaluated. Experimental results show that the proposed system is a lightweight real-time algorithm that performs better than other traditional fingerprinting methods in terms of accuracy under constraints of limited processing and memory resources.

The 5 GHz Wireless LAN (802.11a) is a popular standard for wireless indoor communications providing moderate range and speed. Combined with the emerging ultra Wideband standard (UWB) for short range and high speed communications, the two standards promise to fulfil all areas of wireless application needs. However, due to the overlapping of the two spectrums, the stronger 802.11a signals tend to interfere causing degradation to the UWB receiver. This presents one of the main technical challenges preventing the wide acceptance of UWB. The research work presented in this thesis is to propose a low cost RF receiver front-end filter topology that would resolve the narrowband (NB) interference to UWB receiver while being operable in both 802.11a mode and UWB mode. The goal of the dual mode filter design is to reduce cost and complexity by developing a fully integrated front-end filter. The filter design utilizes high Q passive devices and Q-enhancement technique to provide front-end channel-selection in NB mode and NB interference rejection in UWB mode. In the 802.11a NB mode, the filter has a tunable gain of 4 dB to 25 dB, NF of 8 dB and an IIP3 between -47 dBm and -18 dBm. The input impedance is matched at -16 dB. The frequency of operation can be tuned from 5.15 GHz to 5.35 GHz. In the UWB mode, the filter has a gain of 0 dB to 8 dB across 3.1 GHz to 9 GHz. The filter can reject the NB interference between 5.15 GHz to 5.35 GHz at up to 60 dB. The Q of the filter is tunable up to a 250 while consuming a maximum of 23.4 mW of power. The fully integrated dual mode filter occupies a die area of 1.1 mm2.