OFDM and Spatial Diversity

2017 ◽  
pp. 169-178
Author(s):  
K. C. Raveendranathan
Keyword(s):  
Spatial Diversity

MIMO Systems in a Composite Fading and Generalized Noise Scenario: A Review

2020 ◽  
Vol 14 ◽  
Author(s):  
Keerti Tiwari
Keyword(s):  
System Performance ◽  
Performance Enhancement ◽  
Channel Model ◽  
Mimo Systems ◽  
Mimo System ◽  
Spatial Diversity ◽  
Spatial Multiplexing ◽  
Channel Models ◽  
Efficient System ◽  
Composite Channel

: Multiple-input multiple-output (MIMO) systems have been endorsed to enable future wireless communication requirements. The efficient system designing appeals an appropriate channel model, that considers all the dominating effects of wireless environment. Therefore, some complex or less analytically acquiescent composite channel models have been proposed typically for single-input single-output (SISO) systems. These models are explicitly employed for mobile applications, though, we need a specific study of a model for MIMO system which can deal with radar clutters and different indoor/outdoor and mobile communication environments. Subsequently, the performance enhancement of MIMO system is also required in such scenario. The system performance enhancement can be examined by low error rate and high capacity using spatial diversity and spatial multiplexing respectively. Furthermore, for a more feasible and practical system modeling, we require a generalized noise model along with a composite channel model. Thus, all the patents related to MIMO channel models are revised to achieve the near optimal system performance in real world scenario. This review paper offers the methods to improve MIMO system performance in less and severe fading as well as shadowing environment and focused on a composite Weibull-gamma fading model. The development is the collective effects of selecting the appropriate channel models, spatial multiplexing/detection and spatial diversity techniques both at the transmitter and the receivers in the presence of arbitrary noise.

scholarly journals Drivers of Macrophyte and Diatom Diversity in a Shallow Hypertrophic Lake

Water ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1569
Author(s):  
Kateřina Šumberová ◽  
Ondřej Vild ◽  
Michal Ducháček ◽  
Martina Fabšičová ◽  
Jan Potužák ◽  
...  
Keyword(s):  
Fish Farming ◽  
Spatial Diversity ◽  
Spatiotemporal Variability ◽  
Water Level Fluctuations ◽  
Nutrient Requirements ◽  
Diatom Assemblages ◽  
Climatic Extremes ◽  
Growing Seasons ◽  
High Species Richness ◽  
Different Parts

We studied macrophyte and diatom assemblages and a range of environmental factors in the large hypertrophic Dehtář fishpond (Southern Bohemia, Czech Republic) over the course of several growing seasons. The spatial diversity of the environment was considered when collecting diatoms and water samples in three distinct parts of the fishpond, where automatic sensor stations continually measuring basic factors were established. Macrophytes were mapped in 30 segments of the fishpond littoral altogether. High species richness and spatiotemporal variability were found in assemblages of these groups of autotrophs. Water level fluctuations, caused by the interaction of fish farming management and climatic extremes, were identified as one of the most important factors shaping the structure and species composition of diatom and macrophyte assemblages. The distance of the sampling sites from large inflows reflected well the spatial variability within the fishpond, with important differences in duration of bottom drainage and exposure to disturbances in different parts of the fishpond. Disturbances caused by intensive wave action are most probably a crucial factor allowing the coexistence of species with different nutrient requirements under the hypertrophic conditions of the Dehtář fishpond. Due to a range of variables tested and climatic extremes encountered, our study may be considered as a basis for predictive model constructions in similar hypertrophic water bodies under a progressing climate change.

scholarly journals Study on Time Reversal Maximum Ratio Combining in Underwater Acoustic Communications

2021 ◽  
Vol 11 (4) ◽  
pp. 1509
Author(s):  
Anbang Zhao ◽  
Caigao Zeng ◽  
Juan Hui ◽  
Keren Wang ◽  
Kaiyu Tang
Keyword(s):  
Time Reversal ◽  
Signal To Noise Ratio ◽  
Spatial Diversity ◽  
Single Element ◽  
Noise Power ◽  
Theoretical Derivation ◽  
Underwater Acoustic ◽  
Maximum Ratio Combining ◽  
Weight Coefficients ◽  
Output Snr

Time reversal (TR) can achieve temporal and spatial focusing by exploiting spatial diversity in complex underwater environments with significant multipath. This property makes TR useful for underwater acoustic (UWA) communications. Conventional TR is realized by performing equal gain combining (EGC) on the single element TR output signals of each element of the vertical receive array (VRA). However, in the actual environment, the signal-to-noise ratio (SNR) and the received noise power of each element are different, which leads to the reduction of the focusing gain. This paper proposes a time reversal maximum ratio combining (TR-MRC) method to process the received signals of the VRA, so that a higher output SNR can be obtained. The theoretical derivation of the TR-MRC weight coefficients indicates that the weight coefficients are only related to the input noise power of each element, and are not affected by the multipath structure. The correctness of the derivation is demonstrated with the experimental data of the long-range UWA communications conducted in the South China Sea. In addition, the experimental results illustrate that compared to the conventional TR, TR-MRC can provide better performance in terms of output SNR and bit error rate (BER) in UWA communications.

scholarly journals The Impact of RDP Measures on the Diversification of Agriculture and Rural Development—Seeking Additional Livelihoods: The Case of Poland

Agriculture ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 253
Author(s):  
Mirosław Biczkowski ◽  
Aleksandra Jezierska-Thöle ◽  
Roman Rudnicki
Keyword(s):  
Rural Development ◽  
Rural Areas ◽  
Spatial Scales ◽  
Development Program ◽  
Spatial Diversity ◽  
Agricultural Activities ◽  
Synthetic Index ◽  
Two Measures ◽  
The Impact ◽  
The Eu

The paper’s main aim is to assess the measures implemented within the Rural Development Program (RDP) 2007–2013 in Poland. This programme is dedicated to the diversification of business activities in rural areas and rural livelihood and, thus, the improvement of the multifunctionality of rural areas. The analysis covered two measures from Axis 3, Improvement of the quality of life in rural areas and diversification of rural economy: M311, diversification into non-agricultural activities; and M312, Establishment and development of micro-enterprise. The study and the discussion are presented from a geographical perspective and, in a broader context, take into account several conditions (natural, urban, agricultural and historical) and the spatial diversity of the allocation of European Union (EU) funds. Models of a policy of multifunctional rural development, implemented after accession to the EU, are presented. The research’s spatial scope covers Poland’s territory on two spatial scales: the system of regions (16 NUTS2 units) and poviats (314 LAU level 1 units). The analysis covers all the projects implemented in Poland under the two measures of Axis 3 of the RDP 2007–2013. A set of conditions was prepared for all LAU1 units, forming the background for assessing the impact of the EU funds on the development of non-agricultural activities. To determine the relationship between the RDP measures and the selected groups of conditions, a synthetic index and a correlation index are used. They are also used to determine the mutual relations between the two analyzed activities in terms of the spatial scales used. Access to the EU funds (RDP) has considerably enlarged the opportunities for accelerating agricultural modernisation and restructuration towards multifunctional development, as well as the opportunities for implementing new development and work methods in the countryside in Poland. The attractiveness of the two studied RDP measures varied across regions. The beneficiaries’ activity depended on the local potential (resources), culture and tradition of the region, and size and potential of the farm. In the areas where agriculture is deeply rooted, beneficiaries were more willing to engage in ventures tapping into the resources available in their farms. Thus, they create additional livelihood of income and workplaces for household members. In turn, the beneficiaries from the areas where farms are smaller and economically weaker often undertake activities related to setting up a new business (outside farming).

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