Modelling Multilayer Communication Channel in Terahertz Band for Medical Applications

In this work we present a multi-layer channel model for terahertz communication that incorporates both layers of human body tissues and textile layers. Many research works tackled communication channel modelling in human body alone while some other research focused on textile characterization/modelling alone. There is a real gap in connecting these different models. To investigate this, a multi-layer channel model for terahertz communication is developed, this model assumes external textile layer stacked over layers of human body tissues. The electromagnetic properties of the different layers are extracted from previous works that used time domain spectroscopy (TDS) in the terahertz band to characterize each of the considered layers. The model is implemented as a flexible MATLAB/Octave program that enables the simulation of layers with either fixed or random depths. This paper aims to pave the way to connecting patients’ in-body nano-nodes with off-body (on-cloth) nano-nodes by building such a combined channel model. This helps in many applications especially in the medical field. For example, having connected nano-nodes can help in diagnosing diseases, monitoring health by sending information to the external environment, treatment (e.g., increasing or decreasing a certain dose depending on the monitoring), etc. The obtained results show how the THz signal can be affected when it propagates through heterogeneous mediums (i.e., human body tissues and textile). Various types of path-loss has been calculated for this purpose and verified by comparison with results from previous research on separate models of human body and textile.

Adaptive Combined Channel Network Coding for Cooperative Relay Aided Cognitive Radio Networks

Cognitive radio (CR) is one of the emerging technologies for 4G/5G applications. Cooperative relay communications and network coding are some techniques that helped in enhancing the CR applications. This paper considers a primary broadcasting system for multimedia video streaming applications that broadcasts data to the primary users and to an aiding cooperative relay CR secondary system. The cooperative overlay secondary system can use many error control coding techniques for point-to-point data retransmissions such as channel coding, network coding, and combined coding techniques to enhance the system performance under variable channel conditions. This work proposes a novel adaptive combined channel network coding (AC2NC) technique for data retransmissions. The new AC2NC first analyses the channel feedback information and then selects the best retransmission coding technique based on the targeted bandwidth or transmission time optimization. This is instead of using a single static channel or network coding technique with dynamic channel conditions. The proposed AC2NC improves the system throughput, decreases the retransmission time, and avails more spectrum access opportunities for the secondary system’s own data transmissions. The AC2NC relative bandwidth and time saving opportunities for CR users can exceed 90% under certain channel conditions versus some static coding techniques.

COMBINED CHANNEL PROCESSING TECHNOLOGY BASED ON MULTI-LAYER TEMPLATES

Рассмотрена технология изготовления дополнительных элементов систем охлаждения ракетных двигателей в форме местных углублений, расположенных на имеющихся фрезерованных каналах на наружных поверхностях камер сгорания и реактивного сопла. Такая проблема требует решения в перспективных изделиях с повышенной теплонапряженностью зоны горения топлива. Проведен анализ конструкции и возможностей обработки дополнительных элементов охлаждения в донной части и на боковых поверхностях узких каналов с ограниченным доступом инструмента в зону удаления припуска. Изучены новые конструкции инструмента для комбинированной обработки с использованием шаблонов различной конструкции и обоснована возможность их использования для изготовления углублений в каналах. Предложены новые способы комбинированной локальной обработки углублений с несимметричной геометрией сечения, форма которых обоснована в процессе отработки технологичности конструкции создаваемых двигателей, что ранее считалось неосуществимым или чрезмерно трудоемким. Исследована возможность многоместной обработки локальных углублений для дополнительного охлаждения в каналах на участках с переменным профилем камер сгорания современных и перспективных изделий по многослойным шаблонам. Здесь разработанные комбинированные технологии дают наибольший эффект и способствуют повышению ресурса двигателей новых поколений до уровня, обеспечивающего многократное увеличение количества безотказных пусков космических систем, что значительно снижает затраты на изготовление ракетных двигателей новых поколений The article considers the technology of manufacturing additional elements of rocket engine cooling systems in the form of local recesses located on the existing milled channels on the outer surfaces of the combustion chambers and the jet nozzle. This problem requires solutions in promising products with high heat stress of the fuel combustion zone. We analyzed the design and processing capabilities of additional cooling elements in the bottom part and on the side surfaces of narrow channels with limited tool access to the allowance removal zone. We studied new tool designs for combined processing using templates of various designs and justified the possibility of their use for making recesses in channels. We propose new methods of combined local processing of recesses with an asymmetric cross-section geometry, the shape of which is justified in the process of testing the manufacturability of the design of the created engines, which was previously considered impossible or excessively labor-intensive. We investigated the possibility of multi-site processing of local recesses for additional cooling in channels in areas with a variable profile of the combustion chambers of modern and promising products using multilayer templates. Here, the developed combined technologies give the greatest effect and contribute to increasing the resource of new-generation engines to a level that provides a multiple increase in the number of trouble-free launches of space systems. This significantly reduces the cost of manufacturing new-generation rocket engines