This thesis presents a model for the ACK-clock inner loop, common to virtually all Internet congestion control protocols, and analyzes the stability properties of this inner loop, as well as the stability and fairness properties of several window update mechanisms built on top of the ACK-clock. Aided by the model for the inner-loop, two new congestion control mechanisms are constructed, for wired and wireless networks. Internet traffic can be divided into two main types: TCP traffic and real-time traffic. Sending rates for TCP traffic, e.g., file-sharing, uses window-based congestion control, and adjust continuously to the network load. The sending rates for real-time traffic, e.g., voice over IP, are mostly independent of the network load. The current version of the Transmission Control Protocol (TCP) results in large queueing delays at bottlenecks, and poor quality for real-time applications that share a bottleneck link with TCP. The first contribution is a new model for the dynamic relationship between window sizes, sending rates, and queue sizes. This system, with window sizes as inputs, and queue sizes as outputs, is the inner loop at the core of window-based congestion control. The new model unifies two models that have been widely used in the literature. The dynamics of this system, including the static gain and the time constant, depend on the amount of cross traffic which is not subject to congestion control. The model is validated using ns-2 simulations, and it is shown that the system is stable. For moderate cross traffic, the system convergence time is a couple of roundtrip times. When introducing a new congestion control protocol, one important question is how flows using different protocols share resources. The second contribution is an analysis of the fairness when a flow using TCP Westwood+ is introduced in a network that is also used by a TCP New Reno flow. It is shown that the sharing of capacity depends on the buffer size at the bottleneck link. With a buffer size matching the bandwidth-delay product, both flows get equal shares. If the buffer size is smaller, Westwood+ gets a larger share. In the limit of zero buffering, it gets all the capacity. If the buffer size is larger, New Reno gets a larger share. In the limit of very large buffers, it gets 3/4 of the capacity. The third contribution is a new congestion control mechanism, maintaining small queues. The overall control structure is similar to the combination of TCP with Active Queue Management (AQM) and explicit congestion notification, where routers mark some packets according to a probability which depends on the queue size. The key ideas are to take advantage of the stability of the inner loop, and to use control laws for setting and reacting to packet marks that result in more frequent feedback than with AQM. Stability analysis for the single flow, single bottleneck topology gives a simple stability condition, which can be used to guide tuning. Simulations, both of the fluid-flow differential equations, and in the ns-2 packet simulator, show that the protocol maintains small queues. The simulations also indicate that tuning, using a single control parameter per link, is fairly easy. The final contribution is a split-connection scheme for downloads to a mobile terminal. A wireless mobile terminal requests a file from a web server, via a proxy. During the file transfer, the Radio Network Controller (RNC) informs the proxy about bandwidth changes over the radio channel, and the current RNC queue length. A novel control mechanism in the proxy uses this information to adjust the window size. In simulation studies, including one based on detailed radio-layer simulations, both the user response time and the link utilization are improved, compared TCP New Reno, Eifel and Snoop, both for a dedicated channel, and for the shared channel in High-Speed Downlink Packet Access. / QC 20100830

The current Internet design is based on a best-effort service, which combines high utilization of network resources with architectural simplicity. As a consequence of this design, the Internet is unable to provide guaranteed or predictable quality of service (QoS) to real-time services that have constraints on end-to-end delay, delay jitter and packet loss. To add QoS capabilities to the present Internet, the new functions need to be simple to implement, while allowing high network utilization. In recent years, different methods have been investigated to provide the required QoS. Most of these methods include some form of admission control so that new flows are only admitted to the network if the admission does not decrease the quality of connections that are already in progress below some defined level. To achieve the required simplicity a new family of admission control methods, called end-to-end measurement-based admission control moves the admission decision to the edges of the network. This thesis presents a set of methods for admission control based on measurements of packet loss. The thesis studies how to deploy admission control in an incremental way: First, admission control is included in the audiovisual real-time applications, without any support from the network. Second, admission control is enabled at the transport layer to differentiate between elastic and inelastic flows, by embedding the probing mechanism in UDP and using the inherent congestion control of TCP. Finally, admission control is deployed at the network layer by providing differentiated scheduling in the network for probe and data packets, which then allows the operator to control the blocking probability for the inelastic flows and the average throughput for the elastic flows. The thesis offers a description of the incremental steps to provide QoS on a DiffServ-based Internet. It analyzes the proposed schemes and provides extensive figures of performance based on simulations and on real implementations. It also shows how the admission control can be used in multicast sessions by making the admission decision at the receiver. The thesis provides as well two different mathematical analyses of the network layer admission control, which enable operators to obtain initial configuration parameters for the admission decision, like queue sizes, based on the forecasted or measured traffic volume. The thesis ends by considering a new method for overload control in WLAN cells, closely based on the ideas for admission control presented in the rest of the articles. / QC 20100826

Telemarknaden i Sverige har under de senaste åren ställts inför nya utmaningar som inte bara är ett resultat av avregleringen utan även av kundernas ökade krav på produkter och tjänster. Överlevnaden för den före detta monopolisten beror på hur väl de kan tillgodose kundernas krav och aktivt bemöta de övriga aktörerna i branschen. Därmed blev frågeställningen att undersöka vilka faktorer som är väsentliga för att de före detta monopolistiska företagen ska kunna överleva på dagens marknad och syftet med arbetet blev att utvärdera och analysera denna strategiska process. Vi har valt att göra en kundundersökning med syfte att kunna besvara vår problemställning och därmed valdes kundperspektivet. Med tanke på att Sverige bara har ett teleföretag som har blivit avreglerat, nämligen TeliaSonera, blev det naturligt att vi utgick ifrån just detta företag. Kundundersökningen gjordes med privatkunder i åldern 20 – 50 år. För att kunna ställa relevanta frågor i enkäten gjorde vi en omfattande förstudie som inkluderade artiklar i dagspress, offentliga rapporter och tidigare undersökningar, samt ett samtal med TeliaSoneras marknadsanalytiker. Det som vi kom fram till i vårt arbete är att om ett företag ska kunna överleva på en konkurrensutsatt marknad borde det ha både hög marknadsfokus och hög kundfokus. För att uppnå denna kombination krävs det att företaget är medveten och uppmärksam på vad som händer på marknader, hur konkurrenterna agerar, teknologiska utvecklingen och samtidigt ha kunden och dess önskningar och krav i centrum.

Denna uppsats syftar till att redogöra för den institutionella utveckling som skett i Kina under mellan år 2002-2008 och ta reda på hur svenska företag inom telekombranschen påverkas av den nya institutionella kontexten. För att undersöka Kinas ekonomiska, politiska och sociala institutionella utveckling och se effekterna hos svenska företag gjordes en statistisk jämförelse av institutionella faktorer mellan åren 2002 och 2008 samt företagsintervjuer med tre svenska företag i Shanghai under februari 2009. Resultatet visar att det blivit avsevärt dyrare för utländska företag att verka i Kina som resultat av många institutionella förändringar som skett de senaste åren, bl.a. har många incitament för utländska bolag slopats och marknaden är nu mer rättvis mellan utländska och inhemska företag. Undersökningen visar även på en fortsatt långsam utveckling av politiska och sociala faktorer såsom korruption, patentskydd och byråkratisk kvalitet. Dessa förändringar kompenseras dock alltjämt av en enorm ekonomisk tillväxt som driver på efterfrågan av produkter.  Slutsatsen är att svenska företag som arbetar inom telekombranschen är etablerade i Kina pga. den stora inhemska efterfrågan snarare än i jakt på billig tillverkning. Trots de högre kostnader som drabbar företag och en institutionell kontext som allt mer liknar länder i väst, accepteras dessa nya förutsättningar för att få ta del av Kinas enorma marknad.

Measurements are important to specify and verify properties for components, modules and systems. The specifications for a certain figure of merit are usually given in a numerical value or a two dimensional plot. However, there are some devices, like power amplifiers with certain figure of merits that depends on two or more working conditions, requiring a three dimensional plot. This thesis presents a measurement method including graphical user interface of three parameters gain, efficiency and distortion when two-tone or WCDMA signals are used as an input to the PA.

The demand of small size electronic systems has been increasing for several decades. The physical size of systems is reduced due to advancements in integrated circuits. With reduction in size of electronic systems, there is also an increasing demand of small and low cost antennas. Patch antennas are one of the most attractive antennas for integrated RF front end systems due to their compatibility with microwave integrated circuits. To fulfil the demand of integrated RF front end systems, a design of microstrip patch antenna with optimum performance at 70GHz is investigated. The procedure could be extended to design other planar antennas that act in a similar way. In this work, three different design methods to design patch antennas for applications at 70GHz are investigated that include use of analytical models, numerical optimization, and numerical variation of dimensions. Analytical models provide a basic understanding of the operation of a patch antenna and they also provide approximate dimensions of a patch antenna for a targeted frequency without using numerical simulations. However, as the operating frequencies of RF systems reach mm-wave frequencies, we expect that the accuracy of analytical models become less accurate. For example, the excitation of substrate modes and effect of ground size are not predicted in simple analytical models. Due to these expected limitations of the analytical design methods, the accuracy of these models is investigated by numerical electromagnetic field simulations. In this work, CST Microwave Studio Transient Solver is used for that purpose. In order to make sure that the appropriate settings of the solver are applied, the simulation settings such as mesh density, boundary conditions and the port dimensions are investigated. The simulation settings may affect computation time and convergence of the results. Here, in this work, the accuracy of the simulator for a specific design of inset feed rectangular patch antenna is verified. The patch dimensions obtained from analytical calculations are optimized at 70GHz by using the optimizer of the transient solver. The patch dimensions obtained from optimizer are verified by varying the patch dimensions in equidistant steps around the found result of the optimizer. In a rectangular microstrip patch antenna design, the use of a width of 1.5 times the length is an approximate rule of thumb [1] for low dielectric constant substrates. It is also investigated how the performance properties of a microstrip patch antenna are affected by varying the width to length ratio of the patch. There are occasions where a different ratio is required because of space limitations, or to change the input impedance. The patch designs having various width to length ratios were optimized with the feed location. The analytically calculated dimensions provided good initial values of the rectangular patch antenna for further optimization using more accurate techniques. The design have been optimized at 70GHz for the investigated mesh density, boundary conditions and the port dimensions. The numerical variation of dimensions is found to be most reliable among the investigated design methods but it is more complicated with many parameters.

Syncore Technologies har tagit fram en digital telemetri mottagare som använder sig av USBperiferi anordning som ska kunna etablera oavbruten kommunikation mot sin värddator.Den tidigare designen av USB applikationen till digitala mottagaren är utvecklat av ett annatföretag. Problemet med den designen är att den kan stanna av under överföringen. Ett krav förden nya designen av USB gränssnittet är att den ska kunna etablera ett konstant data flödeutan att under en längre tid stanna av mitt under överföringen. Syftet med detta arbete är attordna en stabil överföring mellan mottagare och dator. Gruppen har valt att användanuvarande kretsuppsättning och utveckla egen mjukvara. Dessutom att satsa på de delar avUSB systemet som tar hand om data överföringen till och från kretsuppsättningen.I teoridelen tas endast upp hur USB systemet tar hand om dataflödet, det tas inte upp självaUSB protokollet. FIFO handskakning används för att koppla ett externt FIFO. Främstanvänds i denna rapport FULL handskakning som är en variant av FIFO handskakning. Denanvänds för långsam eller varierande överföringshastighet. GPIF engine är en tillståndsmaskinsom sköter handskakningsprocessen mellan den anslutna USB anordningen till USB värden.Mikrokontrollern är skriven i programspråket C, testapplikationen är skriven i C++ medandata generator koden i FPGA är skrivet i VHDL. Gruppen har använt sig av tillverkarnaskodexempel och API för att utforma de olika programmen. GPIF engine har utnyttjats för attfå fram fungerande GPIF inställningar för mikrokontrollern. Vid felsökning av hårdvara harolika mätpunkter använts vid båda korten för att mäta handskakning och överföring mellanmikrokontrollern och FPGA. Debugger i Visual Studio användes för testapplikationen ochvector waveform i Quartus användes vid felsökning av Counter programmet. Tester utfördessedan för att testa prestanda av mikrokontrollern vid mottagning och sändning av data. Tretester utfördes, överföring via seriella porten UART, slingan mellan FPGA ochmikrokontroller, mottagning av strömmande data i olika hastigheter.Fungerande kod till mikrokontrollern har tagits fram både för överföring via seriella portenoch överföring mellan mikrokontrollern och FPGA. Överföringshastigheten viamikrokontrollern och FPGA uppnådde inte helt kraven. Anledningen är att testapplikationenär skriven på så sätt att data inte kan mottas och behandlas tillräckligt snabbt.

This thesis is a project carried out at the “Centre for RF measurements Technology“at the University of Gävle. The first aim was basically the characterization of different industrial indoor environments to get a model that describes dispersive features of each environment.   The results of previous measurements campaign on three industrial environments as steel mill, storage paper and industrial process mill are used. Also new Power Delay Profile (PDP) on corridor and laboratory has been developed.   Measurements for three frequency bands are done (183-683 MHz, 1640-2140MHz and 2200-2700MHz) and for line-of-sight (LOS) and non-line-of-sight (NLOS) industrial and laboratory scenaries cases are presented.   All these models have been compared with other existing models as Saleh-Valenzuela Model, Two Cluster Model and Indoor Power Delay Profile Model (IPDP Model) and fit-line, typical deviation are shown.   Finally we present a study of the different systems used in the industry and the best suited system to the conditions is chosen.

In todays GSM network more and more interfaces are run over IP instead of classic synchronized networks. This rises new issues to be solved, for example handling of jitter that use of IP networks introduces. The jitter can be handled by a jitter buffer which ensures that the packets are forwarded in evenly spaced intervals. In GSM, data is requested a certain time in advance before delivery to a cellphone. This "time in advance" needs to be adjusted according to the delay of the channel. For an IP network this delay varies (jitter), which means that it would be beneficial to have an algorithm which continuously adjusts how long in advance the packets should be requested. The adjustment is made according to current channel delay and jitter size. In this thesis work a model of a general IP network has been developed and isthen used for development of two algorithms for jitter buffer handling. Once the algorithms have been developed they are evaluated and compared to each other and previous solutions to the problem. One of the algorithms is new and the other is an already existing algorithm that has been extended. The simplified conclusion is that the behaviors of both algorithms are very similar. They mainly have small packet loss but sometimes the packets are requested earlier than needed and therefore are kept in the buffer a bit longer than necessary. When comparing the two developed algorithms with previous solutions it is visible that they improve the buffer handling a great deal.

Mobile communications are a changing and really competitive market. Companies try to release new products and upgrade the old ones as soon as possible. And in this context it is where Ericsson Test Environment makes available to its customer one of the most comprehensive GSM test environments in the world. The test site at customer disposal provides a good environment for testing purpose and it allows them to improve and develop their products in really interesting time terms. To make this possible, a huge GSM network is enclosed inside its facilities and this entails some problem, mainly in the radio environment. The main aim of this thesis work is to study the radio network from an EMC point of view, how all this equipment interacts to each other and to propose possible improvements in order to make a test environment more competitive. Moreover, it will be valued electric magnetic field in the plant with the intention to find out if is possible to warrantee an operation free of disruption in the equipment.