Future wireless communications expect to experience a spectrum shortage problem. One practical solution is spectrum sharing. This thesis studies precoding strategies to allocate communication resources for spectrum sharing in multi-user wireless systems from a game-theoretic perspective. The approaches for the precoding games are developed under different constraints. It is shown that the precoding game with spectral mask constraints can be formulated as a convex optimization problem and a dual decomposition based algorithm can be exploited to solve it. However, the problem is non-convex if users also have total power constraints. This study shows that an efficient sub-optimal solution can be derived by allocating the bottleneck resource in the system. The sub-optimal solution is proved to be efficient and can even achieve an identical performance to that of the optimal solution in certain cases, but with significantly reduced complexity. / Communications

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Made available in DSpace on 2014-12-17T14:55:06Z (GMT). No. of bitstreams: 1 RummeniggeRD.pdf: 785767 bytes, checksum: 0bba3130cce258f9fafc7849fe6507ce (MD5) Previous issue date: 2008-02-15 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / In this work, we propose the Interperception paradigm, a new approach that includes a set of rules and a software architecture for merge users from different interfaces in the same virtual environment. The system detects the user resources and provide transformations on the data in order to allow its visualization in 3D, 2D and textual (1D) interfaces. This allows any user to connect, access information, and exchange information with other users in a feasible way, without needs of changing hardware or software. As results are presented two virtual environments builded acording this paradigm / Neste trabalho, ? apresentado o paradigma Interperceptivo, uma nova abordagem que inclui um conjunto de regras e uma arquitetura de software que une usu?rios de interfaces diferentes no mesmo ambiente virtual. O sistema detecta os recursos do usu?rio e realiza transforma??es nos dados para sua visualiza??o nas interfaces 3D, 2D e textual (1D). Isto permite que qualquer usu?rio conecte, acesse todas as informa??es, e troque informa??es com os outros usu?rios de um modo flex?vel, sem necessitar de altera??es no hardware e sofware. Como resultados s?o apresentados dois ambientes virtuais constru?dos segundo este paradigma

Employment of the multiple-antenna transmitters/receivers in communication systems is known as a promising solution to provide high-data-rate wireless links. In the multi-user environments, the problems of signaling and fairness for multi-antenna systems have emerged as challenging problems. This dissertation deals with these problems in several multi-antenna multi-user scenarios. In part one, a simple signaling method for the multi-antenna broadcast channels is proposed. This method reduces the MIMO broadcast system to a set of parallel channels. The proposed scheme has several desirable features in terms of: (i) accommodating users with different number of receive antennas, (ii) exploiting multi-user diversity, and (iii) requiring low feedback rate. The simulation results and analytical evaluations indicate that the achieved sum-rate is close to the sum-capacity of the underlying broadcast channel. In part two, for multiple-antenna systems with two transmitters and two receivers, a new non-cooperative scenario of data communication is studied in which each receiver receives data from both transmitters. For such a scenario, a signaling scheme is proposed which decomposes the system into two broadcast or two multi-access sub-channels. Using the decomposition scheme, it is shown that this signaling scenario outperforms the other known non-cooperative schemes in terms of the achievable multiplexing gain. In particular for some special cases, the achieved multiplexing gain is the same as the multiplexing gain of the system, where the full cooperation is provided between the transmitters and/or between the receivers. Part three investigates the problem of fairness for a class of systems for which a subset of the capacity region, which includes the sum-capacity facets, forms a polymatroid structure. The main purpose is to find a point on the sum-capacity facet which satisfies a notion of fairness among active users. This problem is addressed in the cases where the complexity of achieving interior points is not feasible, and where the complexity of achieving interior points is feasible. In part four, $K$-user memoryless interference channels are considered; where each receiver sequentially decodes the data of a subset of transmitters before it decodes the data of the designated transmitter. A greedy algorithm is developed to find the users which are decoded at each receiver and the corresponding decoding order such that the minimum rate of the users is maximized. It is proven that the proposed algorithm is optimal. The results of the parts three and four are presented for general channels which include the multiple-antenna systems as special cases.

Employment of the multiple-antenna transmitters/receivers in communication systems is known as a promising solution to provide high-data-rate wireless links. In the multi-user environments, the problems of signaling and fairness for multi-antenna systems have emerged as challenging problems. This dissertation deals with these problems in several multi-antenna multi-user scenarios. In part one, a simple signaling method for the multi-antenna broadcast channels is proposed. This method reduces the MIMO broadcast system to a set of parallel channels. The proposed scheme has several desirable features in terms of: (i) accommodating users with different number of receive antennas, (ii) exploiting multi-user diversity, and (iii) requiring low feedback rate. The simulation results and analytical evaluations indicate that the achieved sum-rate is close to the sum-capacity of the underlying broadcast channel. In part two, for multiple-antenna systems with two transmitters and two receivers, a new non-cooperative scenario of data communication is studied in which each receiver receives data from both transmitters. For such a scenario, a signaling scheme is proposed which decomposes the system into two broadcast or two multi-access sub-channels. Using the decomposition scheme, it is shown that this signaling scenario outperforms the other known non-cooperative schemes in terms of the achievable multiplexing gain. In particular for some special cases, the achieved multiplexing gain is the same as the multiplexing gain of the system, where the full cooperation is provided between the transmitters and/or between the receivers. Part three investigates the problem of fairness for a class of systems for which a subset of the capacity region, which includes the sum-capacity facets, forms a polymatroid structure. The main purpose is to find a point on the sum-capacity facet which satisfies a notion of fairness among active users. This problem is addressed in the cases where the complexity of achieving interior points is not feasible, and where the complexity of achieving interior points is feasible. In part four, $K$-user memoryless interference channels are considered; where each receiver sequentially decodes the data of a subset of transmitters before it decodes the data of the designated transmitter. A greedy algorithm is developed to find the users which are decoded at each receiver and the corresponding decoding order such that the minimum rate of the users is maximized. It is proven that the proposed algorithm is optimal. The results of the parts three and four are presented for general channels which include the multiple-antenna systems as special cases.

Studien avsåg att olika aspekter för att skapa underlag för utvecklingen med att förbättra fleranvändning. Syftet var, utöver de olika aspekterna, att på konceptuell nivå utvärdera hur fleranvändning kan utföras tekniskt samt undersöka hur användarna påverkas av denna förändring. Detta har utförts genom flertalet workshops och intervjuer. Vid två tillfällen har också författarna till rapporten utbildats i hur systemet är uppbyggt och hur det används. Utifrån detta har värdekriterier värderats mot olika tekniker. De teknikerna är Mutex, Semaphores och Oracle Tuxedo. På det sättet har olika aspekter beaktats och konceptuella modeller har målats upp. De olika teknikerna lever alla upp till de tekniska kraven som ställts, som programmeringsspråket C# och en databas från Oracle. I samverkan mellan användare och utvecklare har nivån på lösningen tagits fram, vad den ger användarna för nytta samtidigt som det inte är för komplicerat. Dessutom har det ställts krav angående prestandan, att den inte får försämras väsentligt. Användarna får ett liknande arbetssätt med minskade krav på samordning. Det medför att de kan samarbeta med de datamängder de behöver. Den lösning som passade bäst utifrån dessa kriterier var Mutex. / This paper is intended to study different aspects and take them in consideration to create a foundation for the developers to improve a multi-user environment. The purpose was to evaluate how to develop multi-user systems at a conceptual level with the technical aspects and describe how the users were affected by this. The study is based on multiple workshops and interviews. The writers have also been educated on how the system is used by the users and how the system was built, at two separate occasions. Based on this, criterias were made and these were valued against different techniques. These techniques are Mutex, Semaphores and Oracle Tuxedo. The criterias were considered and conceptual models were made to visualize the solution. The different techniques all live up to the constraints from the hardware and software of the case study, like the programming language C# and a database from Oracle. In a cooperation between the developers and users have the level of the solution been defined, where the solution ease the problems enough and still not too complex to implement. There have also been a few directions on the performance of the system. The solution should not be affecting the performance significantly. The users’working methods are not going to be particularly affected. The main part of the cooperation are not as needed as before. They can work in the same dataset concurrent in the datasets they required. On this basis the best technique to use in this case was Mutex.