Development of digital modem equipment for next generation tropospheric stations and small satellite radio communication systems
The structural and functional principles of modem equipment construction for over-the-horizon communication were developed. Time adaptation algorithms for changing conditions of over-the-horizon communication station, based on fuzzy conclusion algorithms were developed. Algorithms of frequency adaptation for initialization and continuous operation modes were developed. Algorithms to receive energy estimations of the channel and their statistical parameters were developed. Cross-level interaction algorithms, structure and parameters of physical system level of over-the-horizon communications were developed. System synchronization methods using OFDM modulation were developed. Individual blocks(modulators, demodulators, encoders and decoders with straight error correction) VHDL prototypes for adaptive modulation and coding were developed. Experimental studies on model sample based on development boards on FPGA and SDR and by simulation were held. Analytical description of link parameters for small spacecraft and mathematical models for "satellite-earth" and "earth-satellite" links, were done with conducted simulation and potential calculation. The structural and schematic diagrams of nano-satellite subsustem function units and functional unit control software were developed. Experimental samples of functional nano-satellite communication subsystem assemblies were created and their study was held.