Multiuser Access in Systems of Differentially Coherent Information Transmission Based on Chaotic Radio Pulses
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ser Access in Systems of Differentially Coherent Information Transmission Based on Chaotic Radio Pulses A. S. Dmitrieva*, T. I. Mokhsenia, and C. M. Sierra-Terana a
Kotelnikov Institute of Radio Engineering and Electronics, Russian Academy of Sciences, Moscow, 125009 Russia *e-mail: [email protected] Received March 27, 2020; revised March 27, 2020; accepted April 6, 2020
Abstract—The possibility of organizing multiuser access based on the differentially coherent information transmission scheme using chaotic radio pulses as data carriers has been demonstrated. Some theoretical estimates were made for the maximum number of subscribers and the information capacity of a multiuser system. Computer-aided modeling was performed to validate the obtained theoretical results. Keywords: information transmission, chaotic radio pulses, multiuser access. DOI: 10.1134/S106378502007007X
Methods of differentially coherent information transmission with broadband analog noisy (noiselike) signals have been studied since the 1950s [1–3]. However, the development of these methods was hindered for a long time by the difficulties associated with the formation of analog signals as such. The situation began to change with the appearance and development of principles for the formation of noiselike signals of the radio and microwave range on the basis of dynamic chaos. The first differentially coherent information transmission scheme of transceivers with chaotic data carriers (differential chaotic shift keying, DCSK) was proposed in [4–6]. The idea of DCSK consists in that a bit with a duration T is transmitted by means of a sequential pair of identical chaotic signal fragments with a duration T/2 each (to transmit “1”) or a chaotic signal followed by its antipodal signal of the same durations (to transmit “0”). In the DCSK scheme, broadband lines of time delays equal to T/2 are used. They are difficult for small-size implementation, and this appreciably limits the practical applicability of this scheme. However, the DCSK scheme is popular in theoretical studies. Thus, for example, after the DCSK scheme was introduced, both the authors themselves and those who followed them proposed modifications thereof, including variants aimed at increasing the transmission speed [7], improving the stability in multipath channels [8], and organizing multiuser access [9]. In recent papers [10–13], an alternative scheme of differentially coherent information transmission based on chaotic radio pulses (DC2, direct chaotic differential communication) (Fig. 1) free from the problem of long delay times was proposed. In contrast to the
DCSK scheme, the time of delays in a receiver and a transmitter in this scheme is determined by decay time τ of the autocorrelation function of a chaotic signal instead of the duration of a bit. In order of magnitude, τ = 1/ΔF, where ΔF is the band of a chaotic signal. For example, if the band of a chaotic signal is equal to 1 GHz, the autocorrelation time is ~1 ns and the distance passed by an electromagnetic wave in a free space
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