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All cellular radio systems depend on well performing radio resource management algorithms to efficiently utilize available resources. These algorithms make their decisions based on some sort of resource quantity. In the uplink of a WCDMA system, the total received power at the base stations is a natural choice of such a quantity. Unfortunately this quantity cannot be measured with enough accuracy to be used by resource management algorithms. One way of getting around this problem is to estimate a closely related quantity, namely the uplink noise rise. In this paper, we propose and evaluate four different methods to estimate the noise rise. The estimates are insensitive to users bit rate and use data readily available in the system. The best performing method estimates, on average, the uplink noise rise with an error of less than 1 dB for practical load scenarios.

The global communications systems critically relyon control algorithms of various kinds. In wireless communications systems, power control algorithms play an important role for efficient resource utilization. This survey article discusses relevant aspects of power control with emphasis on practical issues, using an automatic control framework. Generally, power control of each connection is distributedly implemented as cascade control, with an inner loop to compensate for fast variations and an outerloop focusing on longer term statistics. These control loops are interrelated via complex connections, which affect important issues such as capacity, load and stability. Therefore, both local and global properties are important. The concepts and algorithms are illustrated by simple examples and simulations.

A framework for positioning, navigation and tracking problems using particle filters (recursive Monte Carlo methods) is developed. Automotive and airborne applications, approached in this framework, have proven a numerical advantage over classical Kalman filter based algorithms. Here the use of non-linear measurement models and non-Gaussian measurement noise is the main explanation for the improvement in accuracy, and models for relevant sensors are surveyed.

The main protocol for flow and congestion control on the Internet is the Transmission Control Protocol, TCP. This protocol was constructed and developed based on heuristic arguments, and its main purpose is to prevent network congestion. Because of changes in the character of the Internet traffic, TCP does not work as well as when it was designed - a problem that has been addressed by researchers in different ways. In this contribution, the bad performance of TCP will be illustrated using queue occupation. Simulations have been made using a simple simulation testbed implemented in the Matlab tools Simulink and StateFlow, as well as a more complex environment in a simulator developed at Berkeley called ns-2. It is seen that a modified TCP implementation yields significant performance improvements.

When operating a cellular radio system nearly at full capacity, admitting yet another user may jeopardize the stability of the system as well as the performance of the individual users. Therefore, proper admission control is crucial. The core idea in this work is to predict the relative load of the system, given that a user is admitted. Then, the user will be admitted if the predicted load in the specific cell, and in its neighbors, is below some threshold. This provide an interesting alternative to algorithms based on hard capacity, which might be utilizing the resources inefficiently in order to be robust. The proposed uplink admission control algorithm utilizes measurements readily available in the system. Simulations indicate performance improvements. Furthermore, multi-services are naturally handled, and availability of high data-rate services are automatically limited with respect to coverage, compared to services of lower data-rate.

Closed-loop power control is considered as an important component in the management of radio resources in cellular radio systems. The algorithms are typically based on feedback information, which for practical reasons is outdated. These time delays in the system, hamper the performance and might even result in unstable systems. Several power control strategies have been proposed in order to improve the capacity of cellular radio systems, but time delays are usually neglected. Here, time delay compensation is introduced as a means to improve the dynamical behavior of power controlled cellular systems, despite time delays. The improvements are validated both in theory with respect to global convergence and stability and in some illuminating simulations.

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 primary goal of cellular radio systems is to provide communications services to a large number of mobile users. Due to the dramatic increase in number ofusers and their demand for more advanced services, the available resources haveto be utilized efficiently. Closed-loop power control is considered as an important component in this resource management. For practical reasons, the powers have to be computed locally for each connection, though performance and stability depend on how the different connections interact. We consider the power control problem as a decentralized control system, consisting of interconnected local control loops. Methods from control theory are used to analyze existing algorithms locally and to design controllers with improved performance. Thereby, performance degradation due to time delays and nonlinearities, can be handled by careful controller design. On a global level, we provide results on stability and convergence of the designed controllers. The results are illustrated by simulations using both small and large-scale simulation environments.

The primary goal of cellular radio systems is to provide communications services to a large number of mobile users. Due to the dramatic increase of this market, the available resources have to be utilized efficiently. Closed-loop power control is considered as an important component in these resource management algorithms. Here, relevant aspects on power control are discussed, using an automatic control framework. Generally, power control strategies are implemented as cascade control, with an inner loop to compensate for fast variations and an outer loop focusing on longer term statistics. Issues as capacity, load and stability are discussed and related to whether it is possible to accommodate the requirements of all users or not. The operation of such algorithms are illustrated by simulations.

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.

Stability is a fundamental property desirable for any controlled system. We briefly review the root locus and describing function techniques, which are tools for stability analysis, and show how they can be applied to power control algorithms in cellular radio networks. The root locus method is used to find stability limits on controller parameters, and describing functions for predicting the presence of oscillations in the system. Thus these methods can be used to support the design phase, when deciding upon the appropriate controller parameters. These tools are demonstrated for various control algorithms and when different smoothing filters are applied. The analysis reveals that the distributed power control (DPC) algorithm, which works fine under ideal circumstances, yields an unstable system when subject to a small time delay. Furthermore, it is concluded that the performance with respect to stability is better when the measurements are averaged by an exponential forgetting filter than by the moving average filter.

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.

The problem to track time-varying parameters in cellular radio systems is studied, and the focus is on estimation based only on the signals that are readily available. Previous work have demonstrated very good performance, but were relying on analog measurement that are not available. Most of the information is lost due to quantization and sampling at a rate that might be as low as 2 Hz (GSM case). For that matter a maximum likelihood estimator have been designed and exemplified in the case of GSM. Simulations indicate good performance both when most parameters are varying slowly, and when subject to fast variations as in realistic cases. Since most computations take place in the base stations, the estimator is ready for implementation in a second generation wireless system. No update of the software in the mobile stations is needed.

The problem to track time-varying parameters in cellular radio systems is studied. The focus is on estimation based only on the signals that are readily available. Previous work has demonstrated very good performance relying on analog measurement. In a real system most of the information is lost due to quantization and sampling at a rate that might be as low as 2 Hz (GSM case). Therefore a different approach is required and for that matter a maximum likelihood estimator has been designed and exemplified in the case of GSM. The needed probability functions of the measurements cannot be described analytically. Instead point-mass approximations can be obtained from Monte-Carlo simulations for each point in a grid covering the interesting parameter space. The proposed algorithm can be tuned to track both slowly and fast varying parameters individually. Since most computations take place in the base stations, the estimator is ready for implementation in a second generation wireless system. No update of the software in the mobile stations is needed.

When employing power control algorithms in real systems there are anumber of problems that have to be considered, of which some are addressed in this work. It is probably impossible to solve the problems using a linear controller, and as an extension, various nonlinear components and their applicability are discussed. Problems due to hardware and external constraints have been identified in previous work, and here anti-reset windup techniques are reviewed and employed. Previous proposals can be seen as special cases. Sometimes it is desirable to employ several algorithms in parallel, and then use a device to state priorities, i.e., to switch between the algorithms. The applicability of switches and selectors are described and exemplified as proposed solutions to the low interference problem, where a C/I balancing algorithm causes a user to use a too low a power. The benefits of using the proposed nonlinear components are further illustrated by network simulations.

The problem to track time-varying parameters in cellular radio systems is studied, and the focus is on estimation based only on the signals that are readily available. Previous work have demonstrated very good performance, but were relying on analog measurement that are not available. Most of the information is lost due to quantization and sampling at a rate that might be as low as 2 Hz (GSM case). For that matter a maximum likelihood estimator have been designed and exemplified in the case of GSM. Simulations indicate good performance both when most parameters are varying slowly, and when subject to fast variations as in realistic cases. Since most computations take place in the base stations, the estimator is ready for implementation in a second generation wireless system. No update of the software in the mobile stations is needed.

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.

The problem to track time-varying parameters in cellular radio systems is studied. The focus is on estimation based only on the signals that are readily available. Previous work have demonstrated very good performance relying on analog measurement. In a real system most of the information is lost due to quantization and sampling at a rate that might be as low as 2 Hz (GSM case). Therefore a different approach is required and for that matter a Maximum Likelihood Estimator has been designed and exemplified in the case of GSM. The needed probability functions of the measurements cannot be described analytically. Instead point-mass approximations can be obtained from Monte-Carlo simulations for each point in a grid covering the interesting parameter space. The proposed algorithm can be tuned to track both slowly and fastly varying parameters individually. Since most computations take place in the base stations, the estimator is ready for implementation in a second generation wireless system. No update of the software in the mobile stations is needed.

Many algorithms in communications systems can be considered as control loops, where the computed quantities depend on feedback information. A common scheme is to use increase/decrease signaling for bandwidth efficiency. Furthermore, the feedback information is delayed. The time delay itself, and even more pronounced in combination with nonlinearities, such as the increase/decrease mechanism, may cause oscillations and instabilities in the system. In this work, analysis methods based on root locus and describing functions are discussed. Design and tuning of algorithms are employed using pole placement techniques. Particular examples include clock synchronization in ADSL modems, control of available bit rate in data networks and, as studied in this project, distributed implementation of power control in cellular radio systems. The relevance of the methods is further illuminated by simulations.

Stability is a fundamental property desirable for any controlled system. We briefly review the root locus and describing function techniques, which are tools for stability analysis, and show how they can be applied to power control algorithms in cellular radio networks. The root locus method is used to find stability limits on controller parameters, and describing functions for predicting the presence of oscillations in the system. Thus these methods can be used to support the design phase, when deciding upon the appropriate controller parameters. These tools are demonstrated for various control algorithms and when different smoothing filters are applied. The analysis reveals that the distributed power control (DPC) algorithm, which works fine under ideal circumstances, yields an unstable system when subject to a small time delay. Furthermore, it is concluded that the performance with respect to stability is better when the measurements are averaged by an exponential forgetting filter than by the moving average filter.

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.

Power control algorithms in cellular radio networks are analyzed. This is basically a MIMO problem where the controlled input is the powers used by the transmitters, and the measurements consist of signal to interference ratios for each receiver. These algorithms can, for each single connection and neglecting the cross couplings, be interpreted as a feedback system. The main contribution here is to analyze a generic control algorithm, which covers some important suggested classical control theory methods such as the root locus and describing function. The results include the important conclusion that unavoidable time delays and nonlinearities (saturation and quantization) in the feedback loop can cause a considerable loss in the stability margin. The results are supported by simulations.

Detta examensarbete har haft som syfte att undersoka om skogsbruksplanerings­ metoden "Avdelningsfritt skogsbruk" kan tillämpas med tillfredsstallande resultat i sodra Sverige. Studien utfordes pa Asa skogsvårdsgård ägd av skogsvårdsstyrelsen i Kronobergs Ian. Fastigheten ar belagen strax soder om Asa ca 30 km norr om Växjö. En pilotstudie har tidigare utforts i Vilhelmina (Holmgren & Thuresson 1995, 1996). Vid skogsbruksplanering ar det viktigt att habra data om skogen att basera beslut pa. Lika viktigt ar dock att veta noggrannheten hos de skattningar som gjorts for olika skogsbruksplaneringsvariabler. Dessutom ar heltackande data en forutsattning for skogsbruksplanering. Pa grund av kostnaden for insamling av objektiva data har skogsbruksplanering hittills baserats pa subjektiva skattningar pa bestandsniva, mojligen kalibrerade med hjalp av objektivt provytematerial. Lamplig skotsel av dessa hestand bestams ocksa subjektivt. Dessa hestand anses vara homogena avseende viktiga variabler for skogsbruksplanering, t ex volym, standortsindex mm och forvantas besta for lang tid. Detta ar en forenkling av verkligheten. Med hjalp av kriging och Geografiska Informations System (GIS) kan man gora heltackande skattningar av viktiga skogsbruksplaneringsvariabler fran objektiva skattningar pa provytor. Dessa skattningar atfOljs dessutom av varden for dessa skattningars noggrannhet, nagot som saknas vid subjektiva skattningar. Kriging ar en geostatistisk metod utvecldad fran borjan inom gruvindustrin, men fullt mojlig att tillampa pa alla variabler som uppvisar spatial autokorrelation, d v s variabler vars varde fOr en viss punkt uppvisar likheter med varden for punkter som ligger nara geografiskt. Metoden utnyttjar information (semivariogram) om hur korrelerade varden, for en viss variabel, ar pa olika avstand. Informationen anvands till att med hjalp av ett vagt medelvarde skatta varden for punkter utan information. Vikterna for de olika observationerna bestams sa att varians, Forest management planning aims at fulfilling the overall goals for the forest owner. The economic optimal scheduling of treatments in spatially discrete forest stands, the time dimension, has been thoroughly investigated in research. The spatial dimension is less investigated. Normally, spatially discrete stands are defined as treatment units. These are inventoried using subjective methods with unknown precision. As an alternative to this conventional way to describe the forest, the present investigation used kriging for estimating forest characteristics spatially continuously using georeferenced sample plots. Using stratification by age, several variables interesting for forest management planning displayed spatial autocorrelation, even though the estate was thoroughly managed. No hardwood variables displayed the autocorrelation necessary for using kriging.

In radio resource management for cellular networks a trade-off has to be made between the congestion level, related to the cell coverage and the intercell interference, and the Quality of Service (QoS), or data rates of the users. This is implemented by using a fast inner power control algorithm and an outer rate control algorithm, working on a slower time scale. Due to the distributed nature of the network, both the information and the control are distributed. Measurements of the congestion and the QoS are used in the control algorithms and this introduces a nonlinear feedback. Another complicating factor is that filtering, computations and information exchange in the network introduce time delays. In this paper we propose a general high order model as a cascade system with an outer and inner control loop. The control algorithms use distributed information available in the network. The full system model includes the nonlinear feedback from congestion and QoS measurements, time delays and time-scale modeling. We provide sufficient conditions for stability and convergence of the system. Our primary analysis tool is input output theory., Parts of the material is previously published in Proceedings of the 50th IEEE Conference on Decision and Control 2011 and Proceedings of IEEE Global Communications Conference 2011. QC 20120413