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SYSTEM OF FREQUENCY PROVIDING OF HF COMMUNICATION CHANNELS BASED ON THE NEW DIGITAL SOUNDER
ON USRP PLATFORM
Ivanov Dmitry Vladimirovich,
Volga State University of Technology, vise-rector, doctor of science, Russia, Yoshkar-Ola, lvanovDV@volgatech.net
Ivanov Vladimir Alexeevich,
Volga State University of Technology, head of department, doctor of science, Russia, Yoshkar-Ola, lvanovVA@volgatech.net
Ryabova Natalya Vladimirovna,
Volga State University of Technology, head of department, doctor of science, Russia, Yoshkar-Ola, RyabovaNV@volgatech.net
Elsukov Alexey Alexandrovich,
Volga State University of Technology, post-graduate student, Russia, Yoshkar-Ola, ElsukovAA@volgatech.net
Ryabova Mariya Igorevna,
Volga State University of Technology, senior lecturer, PhD, Russia, Yoshkar-Ola, miryabova@mail.ru
Chernov Andrey Alexeevich,
Volga State University of Technology senior lecturer, PhD, Russia, Yoshkar-Ola, ChernovAS@volgatech.net
Studied the possibility of creating on USRP platform receiving terminal Ionosonde continuous chirp signal and to obtain compared results with the data of ionospheric sounding analog chirped probe. Created on USRP platform receiving terminal chirp ionosonde showed a higher noise immunity, lack of congestion own signal, the possibility of simultaneous studies of the characteristics of direct and global propagation. Developed an algorithm providing frequency HF communication systems based on panoramic radio sensing using a device sold by technology SDR. As a result of experiments conducted on the radio a length of about 3000 km is established that the application of the developed approaches in the trunk radio enhances the probability of error-free reception of test messages from 54% to 84% of cases in the daytime and from 46% to 90% at night. The first values correspond to the case selection OWC by long-term prognosis. Selecting the OWC as a result of sensing link can significantly reduce the power of the connected signal. In the experiments quite often there have been cases where the choice of OWC using the SDR Ionosonde communication system operating signal power 5W had reliability of communication at the level of 97%. The experimental results showed that during tests of various radio technical systems HF band monitoring of ionospheric radio links using chirp probes allows about 10 times to reduce their terms, as well as improve the reliability and informative test results. Thus, this Ionosonde is a modern tool for providing frequency HF communication systems probed the link.
For citation:
Ivanov D.V., Ivanov V.A., Ryabova N.V., Elsukov A.A., Ryabova M.I., Chernov A.A. System of frequency providing of HF communication channels based on the new digital sounder on USRP platform. T-Comm. 2015. Vol. 9. No.3. Рр. 86-88.
T-Comm Tом 9. #3-2015
Keywords: sounding, USRP, Chirp signal, ionogram, HF communications systems.
The work was supported by RFBR projects № 13-07-00371; 13-02-00524; 15-07-05280; 15-07-05294; state order of the Ministry of Education and Science of the Russian Federation № 3.2695.2014/K, № 8.2697.2014/K, № 227b, № 2247.
Recently actively developing trend called software-defined radio (SDR), which is capable of realizing universal radio system. One of the most flexible hardware implementations of SDR is a family of universal programmable transceivers (USRP) by Fttus Research company j I], The functionality of some communication and radar systems, implemented on the platform USRP, were investigated and proven to be promising. Unsolved actual scicntific task is to program implementation and research on the platform devices that perform other functions. In particular, it is urgent task of creating a USRP and open source software GNU Radio based Network Ionosonde continuous chirp signal, which requires the development of a model of the radio channel and on its basis primary processing algorithm probing signals in USRP receiver.
Objective: To study the possibility of creating on USRP platform receiving terminal Ionosonde continuous chirp signal and to obtain compared results with the data of ionospheric sounding analog chirped probe.
Analog and SDK (platform USRP) Chirp Ionosonde.
Analog chirp ionosonde VSUT described in detail in [2]. Appearance receiving terminal Ionosonde is shown in Figure I.
Figure 1. The receiving terminal of hardware-software complex chirp ionosonde with analog receiver
It includes: analog receiver ¡com IC-R75 {and or IC-R78), HF and GPS antenna, chirp synthesizer [2,3j and a personal computer (PC) with special software. leom IC-R75 takes chirp signals in the range 1.5-30MGts. PC using sound card makes digitization and calculation of the amplitude of the signal at the difference frequency to 1500Hz. It also generates all the necessary commands to operate the equipment.
Figure 2 shows a block diagram based on SDR technology chirp sounder to operate in modes of oblique (OS) [1, 3] and single point vertical (VS) sounding [4, 5] channels HF communications. When the VS is used transmission / reception by M — sequence. Comprehensive sounding chirp signal is generated in the personal computer. In USRP device, it is transferred to the operating frequency with a digital up converter (DUC) and converted to analog (DAC) and supplied to the power amplifier and then through an electronic switch to the antenna. Reflected from the ionosphere signal is received by the same antenna and fed through a switch on the USRP, realizing the digital receiver. The signal processing is to filter the received chirp signal of station interference and compression in the frequency domain and to visualize it as ionograms.
Time-frequency synchronization is provided USRP on signals GPS. Analysis bandwidth delay is 0-0.2s, which allows us to investigate both direct and circumnavigation signals.
figure 2, Block diagram of SDR Ionosonde continuous chirp signal on a universal hardware platform type USRP
Comparison of Ionograms oblique sounding of the ionosphere. Fig. 3 shows ionograms obtained simultaneously analog (a) and digital (b) Ionosonde in experiments on the track of Cyprus — Yoshkar-Ola. Analysis Ionograms showed that fully digital signal processing on the principle of "the ADC to the antenna" allows to get a higher interference immunity (ionogram digital receiver has less interfering signals) without overloading the receiver by "strong" own signals (digital ionogram has no additional tracks above the trace mode IF1) that each of the implementations Ionosonde has its own advantages and disadvantages. However, the digital receiver has lower sensitivity (on ionograms (b) recorded fewer traces of the desired signal than ionogram (a)). In addition, the digital chirp signal reception allows to simultaneously investigate the direct and circumnavigation signals.
Frequency ensure HF communications systems.
We start from the fact that the communication system operates in the frequency channels with a bandwidth of 3.6 kHz. The average frequency is the operating frequency channel of the system at any given time. In addition, the channel is characterized by three key parameters: the signal / noise ratio, scattering delay, scattering (Doppler) frequency. Modems HF communications are characterized by maximum values of the same parameters.
Obviously, if the parameters exceed the limits of the channel parameters of the modem, the channel ceases to be a conditionally, In this case it is necessary to move to work in the other channel (conditionally) or use a different modem, for which the parameters of this channel will be acceptable.
Variability of the ionosphere and the noise level require adaptation of the communication system to the conditions of ionospheric propagation of radio waves on the lines and the level of interference. This procedure ts most effective when the decision is made on the results of sensing the entire set of possible channels. We can say that the sounding of ionospheric line HF communications by continuous chirp signal is equivalent to a serial sensing all possible channels. At the same time, however, it is important to relate the measured parameters when probing with the parameters of the narrowband channel.
T-Comm Tом 9. #3-2015
