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  • Author: A. Skorodumovs x
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After a satellite has been launched, it is impossible to reprogram the hardware modulator. Therefore, a nanoRTU FPGA-based controller (AAC Microtec) in a modified modulation scheme may be programmed as a modem backend for softwaredefined radio (SDR) in the satellite communication system in order to adjust the balance of data rate vs. link reliability, enable coding or encryption system, change communication protocols, etc. For this purpose, a low-power radiation-tolerant reprogrammable satellite modem back-end has been realized for the satellite-to-Earth communication. This paper describes realization of a low data rate modulator based on a robust and reliable symmetric differential phase shift keying (SDPSK) modulation scheme combined with a raised cosine pulse shaping filter in nanoRTU, and presents results of its testing

The software-defined radio (SDR) solutions inpart flexibility to the satellite applications when the devices are physically inaccessible after the launch. The nanoRTU FPGA-based controller (AAC Microtec) may be programmed to serve as a software-defined differential phase shift keying (SDPSK) modem backend to be used in satellites for communication with the Earth. The modem consists of two units - a modulator and a demodulator. A fully functional symmetric SDPSK modulator for nanoRTU FPGA has already been implemented. The next step of the modem implementation is the development of demodulator. In order to implement such facilities, the existing demodulation techniques should be reviewed in order to propose the appropriate method in which the demodulator would be capable of demodulating a signal, and, at the same time, would be resource-efficient. The author describes a valid method of specific SDPSK signal demodulation for the nanoRTU FPGA.

Abstract

Health issues for elderly people may lead to different injuries obtained during simple activities of daily living. Potentially the most dangerous are unintentional falls that may be critical or even lethal to some patients due to the heavy injury risk. In the project “Wireless Sensor Systems in Telecare Application for Elderly People”, we have developed a robust fall detection algorithm for a wearable wireless sensor. To optimise the algorithm for hardware performance and test it in field, we have designed an accelerometer based wireless fall detector. Our main considerations were: a) functionality – so that the algorithm can be applied to the chosen hardware, and b) power efficiency – so that it can run for a very long time. We have picked and tested the parts, built a prototype, optimised the firmware for lowest consumption, tested the performance and measured the consumption parameters. In this paper, we discuss our design choices and present the results of our work.

Methods for Processing and Interpretation of AIS Signals Corrupted by Noise and Packet Collisions

The authors deal with the operation of Automatic Identification System (AIS) used in the marine traffic monitoring to broadcast messages containing information about the vessel: id, payload, size, speed, destination etc., meant primarily for avoidance of ship collisions. To extend the radius of AIS operation, it is envisaged to dispose its receivers on satellites. However, in space, due to a large coverage area, interfering factors are especially pronounced - such as packet collision, Doppler's shift and noise impact on AIS message receiving, pre-processing and decoding. To assess the quality of an AIS receiver's operation, a test was carried out in which, varying automatically frequency, amplitude, noise, and other parameters, the data on the ability of the receiver's ability to decode AIS signals are collected. In the work, both hardware- and software-based AIS decoders were tested. As a result, quite satisfactory statistics has been gathered - both on the common and the differing features of such decoders when operating in space. To obtain reliable data on the software-defined radio AIS receivers, further research is envisaged.