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Master DonNTU Nesterenko Ann

Master DonNTU Nesterenko Ann
University: Donetsk National Technical University
Faculty: Computer Information Technologies and Automation
Speciality: Telekommunication Systems and Networks
Theme of master's work: The research of phase synchronization methods and facilities in the satellite channel
Scientific Supervisor: Ph.D. professor A. Voroncov
Аutobiography Author's abstracts

Аbstract of the Master's theme work

The research of phase synchronization methods and facilities in the satellite channel

Actuality

Satellite communication systems (SСS) are widespread among the systems of information transmission. It is possible to get access to the communication services with their help wherein the use of surface or wireless channels is not economically feasible or just technically impossible. SСS are also used for organization of the channel connection between geographically remote regions or countries with undeveloped communication infrastructure. In SCS a possibility of servicing plenty subscribers located on long distances is provided. The expenses for organization of connection are not depending on distance. SСS consists of space and ground segments. Quality of service for subscriber depends on a satellite operator and receiving earth station (ES), which characteristics could be easily improved.

The peculiarity of SСS is a necessity of working under the conditions of comparatively low relation signal/noise, conditioned by a considerable distance from transmitter to receiver and by the limited satellite power. During the weak signal propagation process through the satellite channel it is inevitably exposed to distortions in the atmosphere, Dopler’s shift and high level compression of information. The result is strong distortion of signal in receiver.

The quantity of the distorted symbols must be very small to use the two staged over jamming encoding and modulation with low coherence. QPSK modulation (Quaternary Phase Shift Keying) is mainly used to provide the best compromise between transmitted power and signal band width.

Loss of phase synchronization results in plenty of errors at QPSK demodulation stage, where information is carried by the phase of signal. To get the synchronous main oscillation it is necessary to provide a compromise between tracking error decreasing in synchronous mode and time decreasing establishment in synchronous mode.

Aim

To increase noise immunity of receiver in a satellite channel and improve its characteristics by decreasing the errors quantity at the input of QPSK demodulator.

Conclusion

Receiving satellite channel of ES works under the conditions of comparatively low signal/noise ratio and use the two-staged protective coding which allows detection and correction of errors. As for as QPSK modulation is used, the information is carried by the phase of signal. Without renewal of phase synchronization there will be plenty of errors at the exit of demodulator and loss of other types of synchronization.

To provide low error rate, the amount of the distorted symbols at the input of demodulator in receiver must be minimized. For this purpose PLL converters are used. But phase synchronization comes true (не понятно) in the coherent demodulator with the Kostas’ loop because the converter heterodyne is needed to carry the carrier to the range of low frequency only. Demodulation can be divided in two parts: demodulation itself and forming of supporting oscillation.

In a demodulator it is suggested to use a PI-regulator instead of LPF in a chain before GDV that allows correct restoring the phase of signal. In further researches it is planned to plug in a chain between transformer of intermediate-frequency and QPSK by a demodulator another link – chart of FATF. This modernization will allow to decrease the amount of errors at the input of demodulator, that will make its noise immunity characteristics stronger.

Literature

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© Nesterenko Ann, 2011