<p>The work described in this report is within the area of three-dimensional (3D) radio channel modeling for mobile communications. The focus was towards rural areas, because radio coverage of rural areas is more costly when using higher frequencies, comparing UMTS to GSM. In addition seasonal and environmental variations are strongest here. The model used was a 3D <i>radar mode</i>l, comprised of a 2D vertical Tx-Rx-plane component and a 3D components to include off-axis scattering. The latter components are estimated using bistatic radar techniques. The model is able to provide an accurate estimation of the path loss (signal level), and is also able to estimate time dispersion and angular dispersion, taking into account off-axis contributions. Radio frequencies around 2 GHz were selected, as these are the most important frequency bands for 3. generation mobile systems, even though the envisaged approach supports radio planning for GSM 900 and WLAN systems.</p><p>A novel approach to the modeling of scattering from random rough surfaces for 3D channel modeling was developed. This amplitude/phase model is simple and accurate compared to conventional models. It makes no inherent assumption about the degree of roughness, making it suited to model all surfaces. The model outperforms the conventional models Plane surface, SPM, Kirchoff and Oren with respect to accuracy by 1.5 to 10 dB depending on the degree of roughness.</p><p>An experimental methodology to characterise random rough surfaces was developed. The work characterised natural surfaces such as asphalt, grass, agriculture, and forest, each of them having a different degree of roughness. Variations due to weather and seasonal changes were taken into account. Typical surface height variations estimated were 10 mm for asphalt, 25 mm for grass, 100 mm for ploughed field and 500 mm for forest. Snow reduced the apparent roughness of ploughed field by 50 %, water on grass increased the reflection coefficient by 50 %.</p><p>An analysis of the implications of the results on 3D channel modeling was performed using a demonstration model. The analysis included a comparison between 2D and 3D model prediction for different area types and land use classes. Also the prediction sensitivity to seasonal and weather variations and model parameter variations were inspected. A 3D model is necessary when the 2D component is attenuated more than typically 15 dB relative to free space, depending on area and land usage. In the network planning example Lillehammer (N) this attenuation of at least 15 dB existed in 40 % of all locations. Weather and seasonal variations may change the mean predicted value by up to 4-5 dB.</p>

The ability to construct software, call it a functional ciphertext, which can be remotely executed in encrypted form as an entirely self-contained unit, has the potential for some interesting applications. One such application is the construction of autonomous mobile agents capable of entering into certain types of legally binding contracts on behalf of the sender. At a premium in such circumstances is the ability to protect secret cryptographic keys or other secret information, which typically is necessary for legally binding contracts. Also important is the ability to do powerful computations, that are more than just one-off secure function evaluations. The problem of constructing computation systems that achieve this, has been attempted by many to little or no avail. This thesis presents three similar cryptographic systems that take a step closer to making such encrypted software a reality. First is demonstrated how one can construct mappings from finite automata, that through iteration can do computations. A stateless storage construction, called a Turing platform, is defined and it is shown that such a platform, in conjunction with a functional representation of a finite automaton, can perform Turing universal computation. The univariate, multivariate, and parametric ciphers for the encryption of multivariate mappings are presented and cryptanalyzed. Cryptanalysis of these ciphers shows that they must be used very carefully, in order to resist cryptanalysis. Entirely new to cryptography is the ability to remotely and securely re-encrypt functional ciphertexts made with either univariate or multivariate encryption. Lastly it is shown how the ciphers presented can be applied to the automaton representations in the form of mappings, to do general encrypted computation. Note: many of the novel constructions in this thesis are covered by a patent application.

The work described in this report is within the area of three-dimensional (3D) radio channel modeling for mobile communications. The focus was towards rural areas, because radio coverage of rural areas is more costly when using higher frequencies, comparing UMTS to GSM. In addition seasonal and environmental variations are strongest here. The model used was a 3D radar model, comprised of a 2D vertical Tx-Rx-plane component and a 3D components to include off-axis scattering. The latter components are estimated using bistatic radar techniques. The model is able to provide an accurate estimation of the path loss (signal level), and is also able to estimate time dispersion and angular dispersion, taking into account off-axis contributions. Radio frequencies around 2 GHz were selected, as these are the most important frequency bands for 3. generation mobile systems, even though the envisaged approach supports radio planning for GSM 900 and WLAN systems. A novel approach to the modeling of scattering from random rough surfaces for 3D channel modeling was developed. This amplitude/phase model is simple and accurate compared to conventional models. It makes no inherent assumption about the degree of roughness, making it suited to model all surfaces. The model outperforms the conventional models Plane surface, SPM, Kirchoff and Oren with respect to accuracy by 1.5 to 10 dB depending on the degree of roughness. An experimental methodology to characterise random rough surfaces was developed. The work characterised natural surfaces such as asphalt, grass, agriculture, and forest, each of them having a different degree of roughness. Variations due to weather and seasonal changes were taken into account. Typical surface height variations estimated were 10 mm for asphalt, 25 mm for grass, 100 mm for ploughed field and 500 mm for forest. Snow reduced the apparent roughness of ploughed field by 50 %, water on grass increased the reflection coefficient by 50 %. An analysis of the implications of the results on 3D channel modeling was performed using a demonstration model. The analysis included a comparison between 2D and 3D model prediction for different area types and land use classes. Also the prediction sensitivity to seasonal and weather variations and model parameter variations were inspected. A 3D model is necessary when the 2D component is attenuated more than typically 15 dB relative to free space, depending on area and land usage. In the network planning example Lillehammer (N) this attenuation of at least 15 dB existed in 40 % of all locations. Weather and seasonal variations may change the mean predicted value by up to 4-5 dB.

Univ., Diss.--Wien, 2001. / Literaturverz. S. 254 - 271.

Zugl.: Erlangen, Nürnberg, Univ., Diss., 2009

The Internet evolves rapidly, both in terms of the applications that use it and the networks that carry the traffic. This creates many important research tasks, both to adapt the networks that carry the traffic to work well together with the Internet protocols and to make the protocols robust to tolerate various underlying networks. A key issue is error handling, in this thesis both error correction for both underlying optical networks and integrated in the Internet protocols are studied. The results show that error control should not be considered in isolation: by combining it with traffic control we find that it is possible to implement new services in elegant ways that are well suited for deployment in the Internet. The traffic in the Internet is increasingly being carried over optical links which offer large capacity. When optical fibers are deployed in access networks, the components need to be cheap and an important factor is sharing of the fibers between several users. One technology that can help in providing these advantages is optical code division multiple access (CDMA). If low-complexity components are used, noise will be a significant problem and there is a need for error control to keep the error rates at an acceptable level. Error control for an optical CDMA network is one of the topics in this thesis. Our results show that there is a strong correlation between the error rates and the number of active users, which indicates the need for traffic control. Moreover, the performance is significantly improved by error correction and soft decoding. In wireless networks, packet loss caused by transmission errors is a well-known problem. In particular for the transmission control protocol (TCP), the performance is severely degraded by losses that are not caused by congestion. In this thesis, end-to-end forward error correction (FEC) is considered as a solution. A further advantage of end-to-end FEC is that it can also improve TCP performance for large bandwidth-delay product paths, where TCP is also known to perform badly. The results show that the error control has to be designed with the requirements of the traffic control in mind. The requirement on the network service is very different for a service like IP-telephony compared to web surfing; hence new traffic control methods are needed. For conversational applications it is important to have predictable performance during a session. For this purpose probe-based admission control can be used, but a problem with this approach is that it cannot isolate different applications with differing requirements on the loss rate. A solution is to combine the admission control with FEC to protect the ongoing sessions and provide consistent quality. Based on these ideas, a service architecture that can be deployed without upgrading the network is proposed and evaluated. The last part of this thesis also shows how this host based scheme could evolve into more complex schemes as network support is provided. / QC 20101019

Sammanfattning Detta examensarbete har genomförts på företaget Axe'L Dataservice. Mitt uppdrag var att implementera ett trådlöst nätverk åt företaget GUNSHILL AB. GUNSHILL AB bedriver mjölk- och köttproduktion och använder ett robot-mjölksystem som heter Lely. Detta system styrs via applikationer som installeras i Android- eller iPhone-enheter. Det trådlösa nätverket hade som mål att täcka mjölkproduktions-anläggningen, på ungefär trehundrafemtio kvadratmeter totalt. I samband med analysen av det trådlösa nätverket, installerade vi ett övervakningssystem. Detta används framförallt som ett testverktyg för att övervaka accesspunkterna under implementeringen samt ge en inblick till företaget GUNSHILL AB om hur användbart och effektivt övervaknings-systemet är. Denna rapport redovisar processen för de genomförda implementeringarna samt beskriver en analys av IEEE 802.11n-teknologin i förhållande till Ubiquiti-utrustningen som används i detta projekt. Resultaten av detta examensarbete uppfyller de krav som företaget GUNSHILL AB hade ställt upp. Det implementerade trådlösa nätverket täcker trehundrafemtio kvadratmeter och levererar en Internet-hastighet upp till 6.4 Mbit/s, vilket motsvarar ungefär 90.6 % av den ursprungliga Internet-hastigheten som är 7 Mbit/s. / Abstract This thesis has been performed at the company Axe'L Data Service. My assignment was to implement a wireless network for the company GUNSHILL ​​AB. GUNSHILL ​​AB, works with milk- and meat production, and use a robotic milking system called Lely. This system is controlled through application software installed on Android or iPhone platforms, specifically mobile phones. The wireless network implemented at GUNSHILL AB, has about tree hundred fifty square meter Wi-Fi coverage. In addition to the wireless system, we deployed a monitoring system as a tool for measuring performance of the access points and monitoring them. This thesis summarizes and goes through the entire process of the wireless- and monitoring system deployment, and performs analysis of the IEEE 802.11n technology based on the technology primarily in Ubiquiti features for 802.11n devices. The conclusion of this thesis is that the project meets the requirements of GUNSHILL ​​AB as expected. The implemented wireless network system covers three hundred fifty square meters and delivers a wireless Internet connection with a speed of 6.4 Mbit/s, which resembles, approximately 90.6 % of the initial speed provided by the ISP (7 Mbit/s).

<p>This thesis examines the possibility of installing a wireless communication system based on multiple antennas, on an Unmanned Aerial Vehicle (UAV). The communication system is based on MIMO technology. This technology uses the fact that we can make use of several antennas at the transmitter and the receiver to create independent signal path which in turn can increase the roboustness of the communication link. Advantages and disadvantages of this new system arediscussed. However, this report concludes that the benefits of MIMO outweights the disadvantages.</p><p>Furthermore a simulation environment for the MIMO system is designed and implemented, based on a specific scenario. Moreover, the results from the simulation also points to a benefit of the MIMO technology.</p>

<p>Quality of Service is a set of mechanisms created for differentiating users and data flows. Provisioning the QoS in service provider networks is always interesting for their business departments for they can offer and sell diverse services and to make more money. This thesis QoS for DSL subscribers of Pardis Online - the private ISP in Iran. The size of the network, the certain network connectivity limitations the ISP has in addition to the complexity of the services it provides, necessitate a comprehensive study to elucidate the different service types and requirements and then choosing a specific implementation of QoS in order to meet the ISP’s need. The internet bandwidth in the region that ISP operates is very expensive and the users suffer from the lack of bandwidth so the limited internet links are usually congested in the network. This document concludes with proposing a layered QoS that guarantees that the total bandwidth of an area in congested times is distributed to the users in that area proportionate to the subscribed band width. The resulting proposals are tested in the Lab and their performance under the simulated traffic is monitored and analyzed.</p>

<p>The up growing wireless communication field always need such a system which is simple but more reliable for multiple applications. To fulfill these demands the modern receiver RF frontend can play an important role. A successful design could be a better solution, not only simple but also modern receiver architecture topology is necessary.The main objective of this dissertation is to design a simple RF-Front end for both multi-band multi-systems Global Navigation Satellite System (GNSS i.e. GPS and Galileo) receiver which</p><p>will provide civil signals on multiple frequencies, similar to those currently available for only military purpose and finally implement and test the receiver front end. Different topologies have been investigated and finally the direct digitization RF front end receiver topology is chosen for simplicity, cost and performance. The entire RF front receiver consists of a broad band LNA, a broad band pass filter and a band stop filter. This kind of receiver needs a minimum feasible sampling frequency which is 434 MHz for designed methodology.A simple receiver RF front end for GNSS application is designed to demonstrate and it has been implemented and tested. The receiver is yield the minimum power consumption which is 26mA</p><p>current from 3V power supply.Although, there are no such a specifications for combined future GPS/Galileo receiver, the</p><p>simple design performance is satisfactory and it will be an interesting future work from commercial point of view.</p>