Analysis of the Local Quasi-Stationarity of Measured Dual-Polarized MIMO Channels

It is common practice in wireless communications to assume strict or wide-sense stationarity of the wireless channel in time and frequency. While this approximation has some physical justification, it is only valid inside certain time-frequency regions. This paper presents an elaborate characterization of the non-stationarity of wireless dual-polarized channels in time. The evaluation is based on urban macrocell measurements performed at 2.53 GHz. In order to define local quasi-stationarity (LQS) regions, i.e., regions in which the change of certain channel statistics is deemed insignificant, we resort to the performance degradation of selected algorithms specific to channel estimation and beamforming. Additionally, we compare our results to commonly used measures in the literature. We find that the polarization, the antenna spacing, and the opening angle of the antennas into the propagation channel can strongly influence the non-stationarity of the observed channel. The obtained LQS regions can be of significant size, i.e., several meters, and thus the reuse of channel statistics over large distances is meaningful (in an average sense) for certain algorithms. Furthermore, we conclude that, from a system perspective, a proper non-stationarity analysis should be based on the considered algorithm

Dual-Polarized Ricean MIMO Channels: Modeling and Performance Assessment

In wireless communication systems, dual-polarized (DP) instead of single-polarized (SP) multiple-input multiple-output (MIMO) transmission is used to improve the spectral efficiency under certain conditions on the channel and the signal-to-noise ratio (SNR). In order to identify these conditions, we first propose a novel channel model for DP mobile Ricean MIMO channels for which statistical channel parameters are readily obtained from a moment-based channel decomposition. Second, we derive an approximation of the mutual information (MI), which can be expressed as a function of those statistical channel parameters. Based on this approximation, we characterize the required SNR for a DP MIMO system to outperform an SP MIMO system in terms of the MI. Finally, we apply our results to channel measurements at 2.53 GHz. We find that, using the proposed channel decomposition and the approximation of the MI, we are able to reproduce the (practically relevant) SNR values above which DP MIMO systems outperform SP MIMO systems.Comment: submitted to the IEEE Transactions on Communication

Developing guidelines for riverfront developments for Malaysia

Rivers and water are important resources for human life, the environment and national development. In Malaysia, the importance of rivers as the focal point of cities was established from the early times of civilisation and will remain so. Population growth, economic growth, urbanisation and increased technology have transformed many Malaysian river systems from water industries into non water industries. Due to these changes, the functions of riverfront areas have also changed and the current pattern of riverfront development in Malaysia now focuses more on mixed-use development and recreation. To date, numbers of riverfront development projects are being developed in Malaysia for recreation, residential and mixed-use. Unfortunately, in most cases, the developments identified are not successful, having cost effects more than their economic value. Example are increases in water pollution indexes and rates of juvenile problems. The focus of this study was to identify the attributes of riverfront development, in order to develop guidelines for riverfront development for Malaysia. The findings of this study were based on interviews conducted with Government officers, Property developers, and the Waterfront community from three case study areas (qualitative phase), and from questionnaires mailed and e-mailed to property development companies listed under Bursa Malaysia (quantitative phase). The findings identified 18 attributes to be used in assisting developers when undertaking riverfront projects in the future. The attributes identified were then recommended to be used as guidelines of best practices of riverfront development in Malaysia

Структурно-динамические режимы образования золото-сульфидно-кварцевой минерализации в Сюльбанской золоторудной зоне (бассейн среднего течения реки Витим)

Приведено описание важнейших разломно-трещинных структур Уряхского рудного поля, определяющих размещение золотосульфидно-кварцевой минерализации, и диаграмм трещиноватости горных пород. Реконструированы планы силового поля на предрудном и рудном этапах формирования структуры рудного поля. Показаны различия масштабов рудовмещающих структур, образованных в Каралонском и Уряхском рудных полях. В сравнительном аспекте обсуждаются результаты изучения структурно-динамических режимов образования золотого оруденения на северном фланге Сюльбанской золоторудной зоны и формулируются выводы

Организация бережливого производства в здравоохранении

В данной статье изучены принципы концепции бережливого производства, а так же приведены особенности и организация бережливого производства в здравоохранении

Налогообложение материальной выгоды физического лица от экономии на процентах

Рассмотрено понятие материальной выгоды, особенности материальной выгоды от экономии на процентах. Проанализирован порядок исчисления НДФЛ по материальной выгоде. Проведены расчеты НДФЛ при беспроцентном займе и займе с процентом ниже минимальной ставки. Проведено сравнение чистой материальной выгоды

Non-stationary dual-polarized radio channels : characterization, modeling, and performance

The performance of wireless multi-antenna communication systems is heavily influenced by the multiple-input multiple-output (MIMO) channel over which transmission takes place. In order to understand the behavior of transmission schemes and improve their performance, accurate channel models are essential. The statistical modeling of wireless channels has been thoroughly studied in the literature, and there exist accurate models, e.g., the WINNER model. However, current models are very limited regarding the temporal behavior of the channel and the consideration of differently polarized antennas, even though the exploitation of the polarization domain can allow for an increased spectral efficiency as well as reduced antenna array sizes. The aim of this thesis is the investigation and the understanding of the impact of realistic channels for radio communication on the performance of multi-polarized MIMO systems. An analysis is made possible by channel measurements at 2.53 GHz. The wireless channel is inherently non-stationary, i.e., the statistical description of the channel changes over time. Changing channel statistics result in time variations of the performance of wireless communication systems. In order to understand the time evolution of the performance of wireless systems, an investigation of the channel non-stationarity is indispensable. We propose a methodology which yields a case-specific definition of regions inside which the channel can be treated as a stationary random process. The resulting local quasi-stationarity (LQS) regions allow for a maximal performance degradation of selected algorithms due to mismatched, e.g., outdated, channel statistics. Based on this methodology and existing methods, an extensive measurement-based analysis of the non-stationarity of single-polarized (SP) and dual-polarized (DP) MIMO channels is performed. Exemplarily, a channel estimation and a beamforming technique are considered. The non-stationarity analysis reveals that the LQS regions are highly dependent on the considered algorithm. The use of the polarization domain of the channel has the potential to provide performance gains, e.g., in terms of spectral efficiency. In order to enable such gains, understanding the impact of the statistical channel parameters on the performance is essential. To this end, a simple but general spatial channel model is developed. This model is analytically tractable and takes into account the presence of dominant components, e.g., due to a line-of-sight connection. Based on this model, an approximation of the (ergodic) achievable rate of SP and DP MIMO systems is derived, which is a function of correlation matrices of the channel. This allows for a direct evaluation of the impact of typical channel properties on the performance without resorting to extensive numerical evaluations. Furthermore, this work investigates when an SP or a DP MIMO system should be used to maximize the achievable rate. A signal-to-noise ratio (SNR) threshold above which DP MIMO systems outperform SP MIMO systems is obtained. This SNR threshold is characterized analytically, in terms of statistical channel parameters, as well as based on measurements. The analysis shows that this threshold lies at realistic SNR values, while it is usually lower when the channel exhibits stronger dominant components