In this paper, an idea of using space-time block coding (STBC) in multi-user cooperative diversity has been exploited to improve the performance of the transmission in wireless local area networks. The theoretical and simulation results show that, using STBC approaches can always achieve the better performance than existing techniques without introducing the space-time coding. By analyzing the throughput and frame error ratio (FER) of the two different STBC cooperative schemes, we find the trade-off between throughput and reliability. The location of the relay is crucial to the performance, which supposes a rule for future crosslayer design.

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In the high-end research process of wireless systems and in the race for the development of the new technologies, MIMO (Multiple Input, Multiple Output) is getting more attention now days. It has a high potential usage in the 3G and 4G communications and beyond. The MIMO based system has got the ability to increase the data throughput in spectrum-limited conditions. With the increase and complexity of wireless applications, the spectrum efficiency improvement in the physical layer will be saturated. MIMO is predicted to be one of the major features for the next generation wireless networking. This thesis work is a part of an ongoing project of the Generic MIMO decoder design carried out at the research laboratory, LESTER at Lorient, France. I was involved in the study of MIMO concepts, orthogonal and Space-time codes and later involved in the design and optimization of the architecture for the core operator for the ML decoder used in the reception of the MIMO system,which is presented in this report work.

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Energy usage has become an important issue in wireless communication systems. The energy-intensive nature of wireless communication has spurred concern over how best systems can make the most use of this non-renewable resource. Research in energy-efficient design of wireless communication systems show that one of its challenges is that the overall performance of the system depends, in a coupled way, on the different submodules of the system i.e. antenna, power amplifier, modulation, error control coding, and network architecture. Network architecture implementation strategies offer protocol software implementors an opportunity of incorporating low-power strategies into the design of the network protocols used for data communication. This dissertation proposes a methodology that would allow a software protocol implementor to analyze the power consumption of a wireless communication system. The foundation of this methodology lies in the understanding of the formal specification of the wireless interface network architecture which can be used to predict the performance of the system. By extending this hypothesis, a protocol implementor can use the formal specification to derive the power consumption behaviour of the wireless system during a normal operation (transmission or reception of data). A high-level formalism like state-transition graphs, can be used to track the protocol processing behaviour and to derive the associated continuous-time Markov chains. Because of their diversity, Markov reward models(MRM) are used to model the power consumption associated with the different states of a specified protocol layer. The models are solved analytically using the Mobius performance and dependability tool. Using the MRM accumulation and utilization measures, a profile of the power consumption is generated. Results from the experiments on the protocol layers show the individual power consumption and utilization of the different states as well as the accumulated power consumption of different protocol layers when compared. Ultimately, the results from the reward model solution can be used in the energy-efficient design of wireless communication systems. Lastly, in order to get an idea of how wireless communication device companies handle issues of power consumption, we consulted with the wireless module engineers at Siemens Communication South Africa and present our findings on current practices in energy efficient protocol implementation.

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Ideas are formed in a process of idea generation that includes creation, development, and communication of new ideas. Drawing has been used as a support for ideation for centuries. Today, computerized tools are commonly used for drawing. Such tools form a user interface between the human and the resulting drawing presented on the screen. The interface may come between the user and the drawing in a disruptive way also affecting the ideation process. Using controlled laboratory studies, this thesis investigates the consequences of drawing with different user interfaces in two types of tasks: creative drawing tasks (based on a standardized test of creativity) and non-creative drawing tasks (i.e. shape-tracing tasks where no new idea is created). The goal was to identify and evaluate the consequences of the several issues originating from the use of different input devices, the functionality of the graphical user interfaces, the formulation of the drawing task, and the user’s previous experience. The results showed that drawing tasks are oriented toward quality of outcomes and that higher input accuracy led to higher quality of outcomes of both creative and non-creative drawing tasks. This came with a trade-off between the quantity and quality. In ideation, less accurate input devices facilitated significantly more ideas but these were of lower quality. In non-creative tracing, higher speeds caused lower quality of outcomes. The users subjectively preferred higher accuracy, also when an inaccurate user interface offered an eraser function. However, using the eraser allowed avoiding reinterpretations of ideas and led to ideation strategies characterized by laborious drawing that negatively affected the quality and quantity of the ideas produced. For non-creative drawing, the more difficult the shapes were, the lower the tracing accuracy. In the thesis a new framework for interaction analysis is introduced that improves the theoretical and practical understanding of computerized drawing tasks and the phenomena resulting from different aspects of the user interface design of computerized drawing tools. This thesis demonstrates that the inaccuracy of computerized tools cannot only make our drawings less aesthetically pleasing but also negatively affect ideas that are created in the process.