Divorce for the Unworthy: Specific Grounds for Divorce

Transmission power control is essential in CDMA systems in order to reduce the near-far effect and to optimize the bandwidth utilization, which is critical when variable data rates are used. One remaining problem is oscillations in the output powers due to round-trip delays in the power control loops together with the power up-down command device. The oscillations are naturally quantified using discrete-time describing functions, which are introduced and applied. More importantly, Time Delay Compensation (TDC) is proposed to mitigate the oscillations. It is also formally proven that TDC result in a stable overall system, with power control errors that converges to a defined bounded region. These bounds are tighter, compared to when not employing TDC. Simulations illustrate the oscillations and the significant performance gains using TDC

The International Court of Justice: Amendment of the Statute and New International Law

Transmission power control is an important means to manage the radio resources in wireless communications. The performance, however, may be reduced due to time delays as in any controlled system. Most controllers to date are designed without considering time delays, which may result in oscillatory or unstable systems. To overcome these problems, time delay compensation (TDC) is introduced. The main idea is to adjust the measurements [e.g., signal-to-interference ratio (SIR)] to include the effects of issued but not yet applied power control commands. TDC thereby improves the stability and performance of an arbitrary power control algorithm. The benefits are illustrated by simulations using some popular power control algorithms

Classifying Corruption

Time delays reduces the performance of any controlled system. If neglected in the design phase, the system may even become unstable when using the designed controller. Several power control strategies have been proposed in order to improve the capacity of cellular radio systems, but time delays are usually neglected. Here, it is shown that the problems can be handled by considering the time delays in the design phase in order to choose the appropriate parameter values. Most popular algorithms can be seen as special cases of an integrating controller. This structure is extended first to a proportional integrating (PI)-controller and then further on to a general linear controller of higher orders. Corresponding design procedures are outlined based on techniques, such as pole placement, from the field of automatic control. The PI-controller is a very appealing choice of structure, with better performance compared to an I-controller and less complex than a higher order controller. The benefits are further illuminated by network simulations

Upholding the Dignity and Best Interest of Children: International Law and the Corporal Punishment of Children

When the systems evolved from analog to digital, the performance was improved by the use of power control on the one hand and different modulations and coding schemes on the other. Condensing the available information we are able to propose a new concept of power control. The concept is applicable to real systems, since it uses the available measurements for estimating parameters necessary for the power control. It also supports the use of an adequate quality measure together with a quality specification supplied by the operator. We will use frequency hopping GSM as an example and the resulting control algorithm is ready for implementation in the software in the base stations where the output powers are computed. No modifications are needed in the GSM standard, the mobile terminals, the radio interfaces or in the base station transmitters. Finally we provide simulation results confirming the benefits of using the new concept for power control

Massive MIMO performance evaluation based on measured propagation data

Massive MIMO, also known as very-large MIMO or large-scale antenna systems, is a new technique that potentially can offer large network capacities in multi-user scenarios. With a massive MIMO system, we consider the case where a base station equipped with a large number of antenna elements simultaneously serves multiple single-antenna users in the same time-frequency resource. So far, investigations are mostly based on theoretical channels with independent and identically distributed (i.i.d.) complex Gaussian coefficients, i.e., i.i.d. Rayleigh channels. Here, we investigate how massive MIMO performs in channels measured in real propagation environments. Channel measurements were performed at 2.6 GHz using a virtual uniform linear array (ULA) which has a physically large aperture, and a practical uniform cylindrical array (UCA) which is more compact in size, both having 128 antenna ports. Based on measurement data, we illustrate channel behavior of massive MIMO in three representative propagation conditions, and evaluate the corresponding performance. The investigation shows that the measured channels, for both array types, allow us to achieve performance close to that in i.i.d. Rayleigh channels. It is concluded that in real propagation environments we have characteristics that can allow for efficient use of massive MIMO, i.e., the theoretical advantages of this new technology can also be harvested in real channels.Comment: IEEE Transactions on Wireless Communications, 201

On Imprisoned Curves and b-length in General Relativity

This paper is concerned with two themes: imprisoned curves and the b-length functional. In an earlier paper by the author, it was claimed that an endless incomplete curve partially imprisoned in a compact set admits an endless null geodesic cluster curve. Unfortunately, the proof was flawed. We give an outline of the problem and remedy the situation by providing a proof by different methods. Next, we obtain some results concerning the structure of b-length neighbourhoods, which gives a clue to how the geometry of a spacetime is encoded in the pseudo-orthonormal frame bundle equipped with the b-metric. We also show that a previous result by the author, proving total degeneracy of a b-boundary fibre in some cases, does not apply to imprisoned curves. Finally, we correct some results in the literature linking the b-lengths of general curves in the frame bundle with the b-length of the corresponding horizontal curves.Comment: 26 pages, 7 figures, LaTeX 2e with AMSLaTeX 1.2 and AMSFonts, submitted to J. Math. Phy

Markbaserade sensorer för insamling av skogliga data : en förstudie

En förutsättning för skoglig planering på alla nivåer är att man har en god uppfattning om tillståndet i den stående skogen. K valiten på de beslut som fattas kommer därför att vara direkt beroende av mängden och kvaliten på den information som samlats in. Sensorer som radar, lidar och olika typer av digitala kameror används idag med framgång för fjärranalys där skogen avbildas från ovan. Föreliggande arbete syftar till att belysa de tekniska förutsättningarna för att utnyttja modem sensorteknik även för markbaserade mätningar. Detta skulle i så fall öppna möjligheter att automatisera fångsten av skogliga data som därmed skulle bli kostnadseffektivare samtidigt som nya typer av data skulle bli tillgängliga. På ett tidigt stadium valdes följande tekniker ut för att närmare studeras med avseende på lämplighet att ingå i ett inventeringskoncept: • Lidar. Lidar är en laserbaserad teknik för att mäta avstånd och riktning till objekt. Laserns fördelar gentemot andra typer av sensorer är att mycket hög vinkelupplösning kan erhållas på signalen. Laser baserade sensorer framstår därför som mycket lämpliga för olika typer av scanning eller avståndsmätning. Nackdelen är att laserstrålen måste ha fri sikt för att kunna registrera ett objekt samt att det i dagsläget handlar om dyr och avancerad teknik. • Fotogrammetri i digitala bilder. Om avståndet till objektet i en bild och kamerans inre geometri är kända kan geometriska mätningar av exempelvis stamdiametrar göras i bilden. Genom att använda digitala bilder och bildanalys borde det vara möjligt att skapa program som mer eller mindre automatiskt detekterar och mäter diametrar på de stammar som är synliga i en bild. Objektavstånden tas lämpligen ut genom separat avståndsmätning med lidar eller genom stereomatchning av två eller flera bilder. • Radar. Radarsignalen använder betydligt lägre frekvenser än laser, vilket ger den intressanta egenskaper i skogsuppskatt ningssammanhang då man kan se igenom objekt mindre än halva våglängden. Nackdelen med lågfrekventa signaler är att man får en för dålig vinkelupplösning om man försöker att genom scanning ta ut vinkel och avstånd till de enskilda stammarna. Radar verkar däremot vara en mer framkomlig väg om man avser att hämta information ur den totala retursignalen. En viss uppfattning om diameter fördelningen skulle i så fall kunna fås genom att studera skillnaden i retursignalen från olika våglängder. • Ultraljud. Ultraljud kan användas enligt samma principer som radar. Fördelarna med ultraljudssensorer är att det finns enkla och billiga standardkomponenter. Nackdelen är att signalen dämpas under fården genom luften och måste därför kalibreras för förändringar i luftens temperatur och fuktighet. Inventeringens uppläggning har också betydelse för de olika teknikernas användbarhet. Om man inventerar enligt principen för tvåfassampling ställs olika krav på utrustningen beroende på om det är det stora primära samplet eller det mer noggranna sekundära samplet man samlar in. Vid insamlingen av det primära samplet försöker man samla in stora mängder data som är korrelerat med den variabel som man önskar mäta för att få ett så lågt representativt fel som möjligt. Generellt kan man därför säga att kvantiteten data är viktigare än kvaliteten på det samma vid insamling av det primära samplet. Detta gör att tekniker som samlar in data kostnadseffektivt men med låg precision blir intressanta, exempelvis radar och ultraljuds sensorer som registrerar ekon kontinuerligt medan utrustningen förs längs en linje. Om man däremot vill mäta in det sekundära samplet med sensorer krävs utrustning som mäter med hög precision på den enskilda provytan, vilket talar för tekniker som lidar och fotogrammetri i digitala bilder. Ett kanske mer realistiskt alternativ är annars att inventera det primära samplet med automatiska kostnadseffektiva metoder medan det sekundära samplet mäts in med traditionella manuella metoder.This MSc thesis was done at the Department of Forest Resources and Geomatics SLU, Umeå during the fall 1996 and spring 1997. A requirement for accurate forestry planning at all levels is knowledge about the condition of the forests today. The quality of the decisions made will therefore be proportional to the quality and amount of information collected. Sensors like radar, lidar and different types of digital cameras are today used quite successfully for remote sensing from aircraft or satellites. The purp ose of the thesis is to make a feasibility-study about ground-based use of these kinds of sensors in order to rationalise and improve forest inventory work. Following techniques where selected for a closer study oftheir qualities as ingredients in an inventory concept: • Lidar. Lidar is an abbreviation for light detection and ranging and is a laser­ hased technique to measure distance and reflection of an object. Compared to other kinds of sensors the lidar has a very high angular resolution. Therefor it is well suited for scanning and ranging where high accuracy is required. The disadvantage of the method isthat a clear sight to the object is needed and that the technique must still be considered advanced and expensive. • Photogrammetry in digital images. If the distance to the object and the intemal geometry of the camera is known for an image, measurements of for example tree diameters or the shape of the whole trunk can be made. By using digital pietmes and image processing it seerus possible to develop programs that more or less automatically detects and measure the desired variables. • Radar. The radar-based sensors are using much lower frequencies than the laser. This gives radar the characteristic of being able to see through objects half the size of the wavelength or less. This could be very valuable if radar are supposed to be used for forest inventory work since there will be a problem with undergrowth covering stems if methods that demands visual sight will be used. The disadvantage with using the appropriate wavelengths is that the angular resolution will be to low for scanning where the purpose is to measure each stem individually. If on the other hand the total sum of the signals in a seanned sector is analysed in order to extract information about the standing volume, radar seems like a very feasible technique for developing an effective forest inventory concept. • Ultras o nie. Ultrasonic can be used by the same theories as for radar. The advantage for ultrasonic compared to radar is that there is a supply of comparatively cheap and simple standard components. The disadvantage is that how much the signal will be reduced while transmitting through the air depends to a high grade of the atmospheric humidity and temperature, which means that calibration must be made. Another negative characteristic of ultrasonic is that the signal is sensitive for wind. The methods of in ventory used al so have an effect on the feasibility of the techniques. If double sampling is used there will be different requirements for the equipment depending on if it is data from the large primary sample or the more accurate secondary sample being collected. When collecting the primary sample i t' s necessary to collect a large amount of data to prevent errors that originates from the representation of the population. The quality of the collected data will therefore be less important. This means that techniques that collects large arnounts of data with high cost-efficiency but lacks in precision will be interesting, for example radar or ultra-sonie sensors that collects data continuously while moving. On the other hand if the purpose is to collect the secondary sample, equipment that measures with high accuracy, like lidar or photogrammetry in digital pictures will be required. Another, maybe more realistic alternative, is to use a cost-efficient sensor-hased technique to collect data from the primary sample and then use traditional manual circular plot sampling for the secondary sample