This paper considers computational costs that occur when a cognitive radio system changes channels for a secondary user. The theoretical gain was estimated to find ways to optimize computations, ...based on knowledge about the conditional state of the cognitive radio system. The analysis of the unnormalized matrix of transition probabilities made it possible to formulate two rules for filling the matrices. The authors studied the structure of the matrix of transition probabilities for three channels and tried to identify the relationship between its elements and symmetry for the matrix dimensions - 24 to 24 elements. The proposed technique allows replacing the calculation of the product of N real numbers with one rewriting of the real number and reduces the multiplication operations. The results of the work can serve as methods for optimizing computational costs in cognitive radio systems or similar systems, this is due to the need to perform computations on devices that do not have enough free resources.
This paper deal with the numerical evaluation of the wireless channel estimation based on machine learning approach in the multiuser multiantenna downlink system. As sounding sequence in frequency ...domain, the CSI-RS sequence are used. The convolution neural network is applied for the task of channel estimation in frequency domain using LS channel estimation on CSI-RS pilots signals. Training data set is generated using the open source 5G channel model QuaDRiGa for static scenario. CNN-based channel estimation algorithm is trained with the data from LS channel estimation and the true channels to obtain the parameters of CNN. CSIRS resource is configured according to 5G NR standard. Numerical results for selected user demonstrate the better performance of the learning-based channel estimation compared the least squares channel estimation method in the frequency response domain and MSE of channel estimation. The accuracy of channel estimate is improved with increase of training epoch and with reducing the learning rate. The obtained results show that machine learning-based channel estimation methods can be used for channel estimation in modern 5G networks or other networks as an alternative to existing methods.
Pulmonary artery denervation (PADN) procedure has not been applied to patients with residual chronic thromboembolic pulmonary hypertension (CTEPH) after pulmonary endarterectomy (PEA).
This study ...sought to assess the safety and efficacy of PADN using remote magnetic navigation in patients with residual CTEPH after PEA.
Fifty patients with residual CTEPH despite medical therapy at least 6 months after PEA, who had mean pulmonary artery pressure ≥25 mm Hg or pulmonary vascular resistance (PVR) > 400 dyn‧s‧cm
based on right heart catheterization were randomized to treatment with PADN (PADN group; n = 25) using remote magnetic navigation for ablation or medical therapy with riociguat (MED group; n = 25). In the MED group, a sham procedure with mapping but no ablation was performed. The primary endpoint was PVR at 12 months after randomization. Key secondary endpoint included 6-min walk test.
After PADN procedure, 2 patients (1 in each group) developed groin hematoma that resolved without any consequences. At 12 months, mean PVR reduction was 258 ± 135 dyn‧s‧cm
in the PADN group versus 149 ± 73 dyn‧s‧cm
in the MED group, mean between-group difference was 109 dyn‧s‧cm
(95% confidence interval: 45 to 171; p = 0.001). The 6-min walk test distance was significantly increased in the PADN group as compared to distance in the MED group (470 ± 84 m vs. 399 ± 116 m, respectively; p = 0.03).
PADN in patients with residual CTEPH resulted in substantial reduction of PVR at 12 months of follow-up, accompanied by improved 6-min walk test.
This paper deals with an analytical model aimed at calculating the probability of false detection of a synchronizing code word (preamble). Several variants of synchronization of the signal sections ..."noise - preamble" and "alternation - preamble" using mathematical and simulation modeling are considered. The results obtained make it possible to estimate the probability of false detection of preambles in a channel with noise and noise with alternation. The proposed methodology allows comparing the effectiveness of various synchronization algorithms and the use of code words of different lengths.
The structure of clathrate hydrates with tetraisoamylammonium polyacrylate salt incorporated as guest has been studied in this work. Also, quantitative studies on the stability changes of the ...clathrate hydrates with different degrees of cross-linking of the guest polymer (varied from 0 to 3%) have been conducted. A single crystal X-ray diffraction study of a crystal of the hydrate with linear (uncross-linked) tetraisoamylammonium polyacrylate as guest reveals a hexagonal structure (space group P6̅m2, a = 12.15 Å, c =12.58 Å at 100 K) with 39 host framework water molecules per one guest monomeric unit. Powder X-ray diffraction analyses confirm the identity of the above crystal structure of the hydrate with linear guest polymer and the crystal structure of the hydrates with cross-linked guest (hexagonal, a = 12.25 Å, c =12.72 Å at 276 K). In order to quantitatively determine the stability differences of the hydrates with the included guests having various degrees of cross-linking of the anionic chain, a series of differential scanning calorimetry measurements of the fusion enthalpy of the hydrate samples has been carried out. On the basis of the results obtained, a structural model describing the decrease in the stability of the clathrate hydrates with tetraisoamylammonium polyacrylate guest as a function of the degree of cross-linking of the guest polymer has been suggested.
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