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In recent years, multiple-input multiple-output (MIMO)systems appear to be very promising since they can provide highdata rates in environments with sucient scattering byexploiting the spatial domain. To design a real MIMO wirelesssystem and predict its performance under certain circumstances,it is necessary to have accurate MIMO wireless channel modelsfor dierent scenarios. This thesis presents dierent models forindoor MIMO radio propagation channels based on 5.2 GHz indoorMIMO channel measurements.The recent research on MIMO radio channel modeling isbriey reviewed in this thesis. The models are categorized intonon-physical and physical models. The non-physical modelsprimarily rely on the statistical characteristics of MIMOchannels obtained from the measured data while the physicalmodels describe the MIMO channel (or its distribution) via somephysical parameters. The relationships between dierent modelsare also discussed.For the narrowband case, a non line-of-sight (NLOS)indoor MIMO channel model is presented. The model is based on aKronecker structure of the channel covariance matrix and thefact that the channel is complex Gaussian. It is extended tothe line-of-sight (LOS) scenario by estimating and modeling thedominant component separately.As for the wideband case, two NLOS MIMO channel modelsare proposed. The rst model uses the power delay prole and theKronecker structure of the second order moments of each channeltap to model the wideband MIMO channel while the second modelcombines a simple single-input single-output (SISO) model withthe same Kronecker structure of the second order moments.Monte-Carlo simulations are used to generate indoor MIMOchannel realizations according to the above models. The resultsare compared with the measured data and good agreement has beenobserved. / <p>NR 20140805</p>

<div>Millimeter-wave (mmWave) bands have become the most promising candidate for enlarging the usable radio spectrum in future wireless networks such as 5G. Since frequent and location-specific blockages are expected for mmWaves, the challenge is understanding the propagation characteristics of mmWave signals and accordingly predicting the channel state information. This research direction has garnered great attention worldwide from industry, academia, and government. However, the majority of current research on mmWave communications has focused on urban areas with high population densities, with very few measurement campaigns in suburban and rural environments. These environments are extremely important for future wireless applications in areas including residential welfare, digital agriculture, and transportation. To fill in this research gap, we developed broadband mmWave channel sounding systems and carried out intensive measurement campaigns at 28 GHz, covering clear line-of-sight as well as non-line-of-sight scenarios over buildings and foliage clutters, to fully characterize the mmWave propagation in suburban and rural environments.</div><div><br></div><div>Moreover, the accuracy provided by traditional statistical models is insufficient for next-generation wireless networks with higher-frequency carriers, because they are unable to predict abrupt channel changes caused by site-specific blockages. To overcome this issue, we explored the possibility of utilizing site-specific geographic features such as buildings and trees in improving mmWave propagation models. A new channel modeling methodology highlighting site-specific parameter evaluation based on easily obtainable data sources (e.g., LiDAR) was proposed for accurate, fast, and automated channel state predictions. Accordingly, an overall root mean square error (RMSE) improvement of 11.79 dB was achieved in a one-building blockage scenario and a regional RMSE improvement of over 20 dB was observed in a coniferous forest. This approach also enables channel simulations for large-scale system performance evaluation, demonstrating a powerful and promising approach for planning and tuning future wide-area wireless networks. The simulation results showed that network densification alone is not enough for closing the digital gap, especially with mmWaves because of the impractical number of required towers. They also backed up supplementary solutions including private data relays, e.g., via drones and portable towers.</div>

Traditional sales systems have been disrupted by technological developments. In order to  adapt, companies are changing the way they interact with their customers in business-to-business markets. In the last three decades, multi-channel strategies have spurred the proliferation of different sales channels and new ways of managing sales systems. The purpose of this research was to investigate what should be considered when managing multi-channel sales systems with the objective of increasing sales efficiency. The study has investigated current utilisation of multi-channel sales systems in the context of a business-to-business setting in industrial companies that are involved in the Swedish automotive industry. Multi-channel sales systems can be utilised to achieve many different objectives. However, this research pays specific attention on how to improve sales efficiency by utilising multi-channel sales systems in the context of a business-to-business setting. The research employed an explorative case study, where semi-structured and structured interviews were conducted at a case company and at companies that are first or second tier suppliers in the Swedish automotive industry. The qualitative data were analysed using thematic analysis. The empirical findings indicate that the most prevalent measure for increasing sales efficiency is to prioritise and allocate customers based on economic attractiveness. Furthermore, the key issues that impede sales efficiency in multi-channels sales system are misaligned sales activities, deficient prioritisation procedures, insufficient promotion of customer value and inadequate focus on customers. The findings highlight key areas to address and may provide guidelines for the design and management of multi-channel sales systems with the specific purpose of obtaining sales efficiency. The implications of this research are mainly practical and are aimed at supporting sales managers, or individuals in similar positions engaged in multi-channel sales system design and management, in obtaining sales efficiency. Managers should focus on aligning sales activities across the whole  sales system, allocate customers according to prioritisation and stay in line with market developments by understanding customer behaviours and perceptions.

Ever faster data transmission in wireless communication is desired to satisfy emerging markets for various media services, such as voice, picture and video calls, multimedia messaging, music and video downloads, and even television. With the explosive increase in the use of mobile devices such as cellular phones, PDAs, GPS, and laptop computers, power consumption has become a prime consideration in the design of mobile communication systems. In order to reliably maintain a high rate of transmission and low power consumption, it is imperative that the receiver obtains as much knowledge as possible about the current state of the channel. A more accurate model of wireless communication channels will indisputably help in obtaining more knowledge about the transient channel state, providing a more accurate and efficient reproduction of the transmitted signal, and decreased power consumption by the receiver. With careful choice and consideration of the channel model, systemic optimization based on the selected channel model will improve the system performance of the transmitter and receiver through better encoding and decoding, as well as through better control of transmitted signal's power level. This thesis focuses on understanding the physical and statistical characteristics of wireless channels, and investigates how to represent wireless channels using simple mathematical models. This thesis initially studied a simple time-varying stationary channel, i.e.a multipath fiat fading channel without terminal motion, which is typically used for indoor wireless communication. With an introduction of stochastic differential equations, we derived a first-order AR stochastic process to represent this stationary channel. For a general multipath fiat fading channel with terminal motion, the traditional Clarke's model was then extended by incorporating the effects of fluctuations in the component phases and analyzed statistically. The resulting theoretical power spectrum was shown to fit practical measured spectra, in contrast to the traditional theoretical fiat fading channel spectra (Jakes' spectrum in [19]) . Finally, we developed a state-space model that represents a wireless channel using these modified spectral characteristics. This was achieved by developing a relationship between the state-space model and the theory of a rational transfer function. A novel method for designing a rational transfer function for linear systems was then proposed. In this method, the rational transfer function is represented via the Observable Canonical Form (OCF) to obtain the state-space model, which can be used to represent and simulate a fiat fading wireless channel. The presented state-space approach is simple and provides rapid computation. The present AR and state-space models provide valuable contributions that can be integrated with other algorithms for better system optimization of wireless communication networks. / Thesis / Doctor of Philosophy (PhD)

The objective of this master's thesis is to analyse trends in distribution in the German market and evaluate their importance in the retail environment. The first chapter of the thesis deals with the issue of distribution from a theoretical perspective. Analysis of the German economy and retail environment serves as a basis for further elaboration of the thesis. In the German market is growing the importance of the e-commerce and there is a tendency of integration of distribution channels. The current situation and trends in distribution channels as well as the trends of the future are outlined on the basis of secondary data. The analysis is completed by qualitative research, which determines the potential use of current trends.

This cumulative dissertation consists of four papers that investigate retailer switching and identify potential and threat of cross-channel retail services (CCRS) for retail businesses. The first, conceptual paper compares different theories and models of retail quality. It derives the concept of retailer aspects as a framework to measure retailer quality and further discusses how CCRS can serve as a tool to enhance those retailer aspects. The second paper discusses results from a consumer panel survey and quantifies the influence of satisfaction with retailer aspects on retailer switching during webrooming behavior. The findings of this second paper present the two retailer aspects assurance of delivery and competitive product pricing as key determinants for retailer switching. The third paper defines CCRS and outlines a conceptual classification scheme for CCRS assessments – the CCRS Pentagon. The fourth paper quantifies the impact of CCRS adoption and retailer aspect preferences on CCRS-induced retailer switching based on a second consumer panel survey. Results from this second study affirm the existence of CCRS-induced retailer switching. The paper concludes that CCRS can serve as a retailer’s lock-in mechanism, but that the availability of CCRS in retail environments also threatens retail businesses. In sum, the dissertation provides academic contributions and suggestions for further academic research as well as practical implications and management tools for application in retail businesses.:I. Introduction II. Enhancing Multi-Channel Retail Quality through Cross-Channel Services III. What Drives Competitive Webrooming? The Roles of Channel and Retailer Aspects IV. Cross-Channel Retail Services: A Service Classification Along The Retail Function V. Service-induced Retailer Switching – Power of Cross-Channel Retail Services VI. Conclusion Appendix A: Estimated parameters in baseline-category logit model Appendix B: Conditional marginal effects and conditional probability Appendix C: T-Tests for retailer aspects per service example

This thesis examines various signal processing techniques that are required for establishing efficient (near optimal) communications in multiuser multiple-input multiple-output (MIMO) environments. The central part of this thesis is dedicated to acquisition of information about the MIMO channel state - at both the receiver and the transmitter. This information is required to organize a communication set up which utilizes all the available channel resources. Realistic channel model, i.e., the spatial channel model (SCM), has been used in this study, together with modern long-term evolution (LTE) standard. The work consists of three major themes: (a) estimation of the channel at the receiver, also known as tracking; (b) quantization of the channel information and its feedback from receiver to the transmitter (feedback quantization); and (c) reconstruction of the channel knowledge at the transmitter, and its use for data precoding during communication transmission. / Communications

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.