The active introduction of Orthogonal Frequency Division Multiplexing (OFDM) technology is now beginning to be widely used in wireless transmission systems, television, radio communication, and radio broadcasting. The efficiency of using a dedicated frequency band at a constant high transmission rate allows you to combat interference arising from the transmission of a useful information on the radio channel. A method of improving quality of information transmission in communication systems with orthogonal frequency multiplexing is described. It is shown that with an increase in the number of receiving and transmitting antennas, the noise immunity increases significantly. An experiment was carried out to change the number of receiving-transmitting antennas and the signal-to-noise ratio, and the dependence of the appearance of an error on the number of transmitting antennas was obtained. The work investigated the software model of MIMO OFDM (modulators and demodulators). As a result of the analysis, the dependence of the appearance of the error frequency on the probability of the error was obtained. This showed that the use of OFDM and MIMO places increased demands on channel estimation.
The efficiency of traffic transmission through wireless communication networks is currently of considerable interest from a research point of view. This is due to the rapid growth of Internet resources, the convergence of technologies for transmitting heterogeneous traffic, the increased mobility of subscribers of communication networks, as well as the growth in the number of different client applications using mobile data transmission. In this paper, we investigate the impact of the growth of client applications on the transmission of mobile traffic. The study shows that the mobile terminal traffic is stable. It is more variable than a random series, because it consists of frequent reversals, but does not have long-term memory, since the Hurst index ranges from 0.3 to 0.5. The distribution of intervals between the arrival of TCP packets is described by the exponent. The distribution of packet lengths for TCP traffic shows that the bulk of the traffic is carried in long packets (1300–2500 bytes). The immutability of the statistical characteristics of traffic when installing several client applications in comparison with the characteristics obtained in previous studies (with a small number of client applications) indicates the immutability of the quality of service. Therefore, the growth of client applications does not affect the transmission of mobile traffic.
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