<abstract xmlns="http://www.w3.org/1999/xhtml">The Doppler effect in 2×2, 3×3, 4×4 MIMO wireless communication systems with channel estimation is studied. The orthogonal pilot signal approach is used for the channel estimation, where the Hadamard sequences are used for piloting, along with the eight alternative orthogonal sets similar to the Walsh set. MIMO transmissions are simulated for 10 cases of the frame length and pilot symbols per frame by no Doppler shift to 1100 Hz Doppler shift with a step of 100 Hz. Based on the simulation, it is ascertained that MIMO transmissions of shorter frames are less sensitive to the Doppler effect. Despite increasing the number of antennas does not mitigate the Doppler effect, and the bit-error rate performance of 4×4 MIMO systems worsens faster than that of 2×2 MIMO systems, it is better to use the maximum number of antennas. The Doppler effect does badly worsen the performance at highway and express train speeds (100 km/hr, and faster), leaving only possibility to further shorten transmissions. This, however, decreases the data rate, but the respective accuracy-versus-data-rate tradeoff must be acceptable.</abstract>

Doppler Effect in 2 × 2 to 4 × 4 Mimo Systems of Wireless Communication with Orthogonal Pilot Channel Estimation

<abstract xmlns="http://www.w3.org/1999/xhtml">Jamming of GNSS signals is lately treated as essential threat for GNSS users. It is especially dangerous in the face of common usage of GPS-like systems in everyday life, and the great belief of everyday users in the truth of devices indications. In spite of the legal prohibition of using them, jammers are commonly accessible, especially in the Internet. Last years showed however that such threat generated purposely also some governments, what is clearly visible in armed conflicts, and during military exercises. Of course this creates the great threat for civilian users if will be in the vicinity.Applications and services based upon GNSS are becoming increasingly embedded in modern society, so community have now become critically dependent upon their correct operation. This refers positioning first of all, but telecommunications networks, power grids, financial transactions, whole world of logistics are dependant as well. The main users of GNSS, both professional and non-professional smartphones users are not prepared on such situation, and usually have no technical possibilities to detect of jamming. For operators of critical installations, for example seaports, or airfields, the detection of jamming cases is extremely important. It can be provided with special devices, which are usually based on specific antennas, and deep analysis of signal. In this paper experiments in detection of the jamming with helical antennas are discussed</abstract>

Possibilities of Detection of the Jamming of the GNSS Receiver with the Helical Antenna

<abstract xmlns="http://www.w3.org/1999/xhtml">Tracking of small objects in any given airspace is an integral part of modern security systems. In these systems, there are embedded methods that employ the techniques based on either radio waves, or acoustic signals, or light radiation. The computer vision operation, springing from the light radiation-based technique, has prompted interest in its research. This operation has the advantage of being less expensive than radars and acoustic systems. In addition, it can solve complex security problems by detecting and tracking humans, vehicles, and flying objects. Therefore, this article evaluates the usefulness of the varying computer vision algorithms for tracking of small flying objects.</abstract>

Tracking of Unmanned Aerial Vehicles Using Computer Vision Methods: A Comparative Analysis

<abstract xmlns="http://www.w3.org/1999/xhtml">The article is a presentation, and detailed description of a mobile, vehicular robot whose task is to support the alarm sub-unit. The project was created in response to the increasing need for monitoring, and recognition of the areas. The robot’s interface was created with the use of integrated development environments for Python. The software implementation was possible due to a minicomputer Raspberry Pi 4 B. The robot’s frame is made out of components which are based on the main chassis. The robot is equipped with compatible sensors and cameras. Those, combined with the interface, are able to give a real-time preview of the area in which the robot is in.This particular vehicular robot is designed to eliminate the risks caused by tasks of alarm sub-unit, by giving the real-time preview, and analysis of the currently watched area. In addition, it can be used to inspect soldiers in the containment zones, and to help with the identification of unknown objects.</abstract>

Mobile Wheeled Robot to Support the Task of the Alarm Sub - Unit

<abstract xmlns="http://www.w3.org/1999/xhtml">The paper determines a non-classical Bittner operational calculus model, in which the derivative is understood as an -symmetric difference <italic>Dm,n</italic>{<italic>x</italic> (<italic>k</italic>)} := {<italic>x</italic> (<italic>k</italic>+<italic>m</italic>)− <italic>x</italic> (<italic>k</italic>− <italic>n</italic>). By considering an operation <italic>Dm,n,b</italic>{<italic>x</italic> (<italic>k</italic>)} := {<italic>x</italic> (<italic>k</italic>+<italic>m</italic>)− <italic>b</italic> (<italic>k</italic>)<italic>x</italic> (<italic>k</italic>− <italic>n</italic>), the formulated model has been generalized.</abstract>

An Operational Calculus Model with the (<italic>m,n</italic>) - Symmetric Difference

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Maritime Technical Journal

 Scientific Journal of Polish Naval Academy has been published since 1959 (in electronic version since 2004). Every year four volumes are published. In this Journal Authors publish their original and previously unpublished scientific articles in the area of technical sciences in English. All the articles contain Polish summaries and key words. All the articles are reviewed by two reviewers. The list of reviewers is published once a year. The Journal has online and printed versions. Why subscribe and read  In the Journal one can find original scientific articles from technical fields, mainly Mechanical Engineering, Electrical Engineering, Geodesy and Cartography. ‘Scientific Journal of Polish Naval Academy’ is an excellent platform for exchanging knowledge and experiences for scientists and experts. Each new issue of the Journal contains articles which present high quality research results of Polish specialists and is an excellent source of professional knowledge for the recipients.  Why submit  Our Journal offers review procedure and short deadlines between sending of the article and approval for publication. All articles are available in Open Access.  The journal has no article processing charges (APCs) and submission processing charges.  Archiving  Sciendo archives the contents of this journal in Portico - digital long-term preservation service of scholarly books, journals and collections.  Plagiarism Policy  The editorial board is participating in a growing community of Similarity Check System's users in order to ensure that the content published is original and trustworthy. Similarity Check is a medium that allows for comprehensive manuscripts screening, aimed to eliminate plagiarism and provide a high standard and quality peer-review process. 

Maritime Technical Journal

Volume 223 (2020): Issue 4 (December 2020)

Doppler Effect in 2 × 2 to 4 × 4 Mimo Systems of Wireless Communication with Orthogonal Pilot Channel Estimation

Possibilities of Detection of the Jamming of the GNSS Receiver with the Helical Antenna

Tracking of Unmanned Aerial Vehicles Using Computer Vision Methods: A Comparative Analysis

Mobile Wheeled Robot to Support the Task of the Alarm Sub - Unit

An Operational Calculus Model with the (m,n) - Symmetric Difference

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