Экспериментальное исследование системы передачи на основе FBMC/OQAM

Introduction. This paper investigates a transmission system based on FBMC/OQAM multiplexing. This system is characterized by a high spectral efficiency, thereby attracting interest as an alternative transmission method in future wireless mobile communication standards. However, a disadvantage of the system is the high complexity of signal processing. There are numerous publications that study the FBMC/OQAM system from a theoretical perspective. This paper presents an experimental study of a transmission system based on FBMC/OQAM.Aim. Verification of a transmission system based on FBMC/OQAM multiplexing in a wireless channel.Materials and methods. Computer simulation modeling in Matlab and experimental research using Keysight and Rohde & Schwarz certified measuring instruments.Results. A model of synthesis and signal processing was developed, and a frame structure was proposed. The processing included synchronization, since the study was carried out in a wireless double-dispersive channel. Time synchronization was provided by the method of time-domain correlation. A preamble consisting of two symbols was used for CFO compensation. Channel estimation in FBMC/OQAM was conducted by pilot symbols spread over the time-frequency domain, a method with an auxiliary pilot to compensate for intrinsic interference, as well as Zero Forcing and a linear interpolator. As a result, dependences of the bit error rate on the Eb/N0 in various channels were obtained. An error rate of 10−4 was achieved under the Eb/N0 equal to 13.4 dB, 15.3 dB and 20.9 dB in the first, second and third channel, respectively.Conclusion. A FBMC/OQAM-based transmission system with a linear equalizer can operate without a cyclic prefix in a multipath wireless channel, providing comparable noise immunity to OFDM-CP. Long frames should be used to obtain greater spectral efficiency, due to the presence of a transition zone at the beginning and end of the FBMC/OQAM frame.Введение. Данная работа посвящена исследованию системы передачи на основе мультиплексирования FBMC/OQAM. Актуальность исследования связана с высокой спектральной эффективностью данной системы, благодаря которой она рассматривается как альтернативный метод передачи в будущих стандартах беспроводной мобильной связи. Однако недостатком системы является высокая сложность обработки сигналов. Среди отечественных и зарубежных публикаций встречается множество работ с теоретическим исследованием системы FBMC/OQAM. В данной статье представлены результаты экспериментального исследования системы передачи на ее основе.Цель работы. Верификация модели системы передачи данных на основе FBMC/OQAM в беспроводном канале связи.Материалы и методы. В работе используется метод имитационного компьютерного моделирования в среде Matlab и экспериментальное исследование с использованием сертифицированного измерительного оборудования Keysight и Rohde & Schwarz.Результаты. Была разработана модель формирования и обработки сигнала, а также предложена структура  кадра.  Покадровая  обработка  выполнялась  с  учетом  временной  и  частотной  синхронизации,  поскольку  исследование  проводилось  в  беспроводном  канале  с  частотно-временным  рассеянием.  Временная синхронизация обеспечивалась корреляционным методом во временной области. Для компенсации  рассогласования  опорных  генераторов  применялась  оценка  с  помощью  преамбулы,  состоящей из двух символов. В работе использовалась оценка канала методом Zero Forcing, а также эквалайзер с линейным  интерполятором.  Для  корректной  оценки  канала  в  FBMC/OQAM  использовались  пилотные символы, распределенные по всей частотно-временной сетке, а также метод с дополнительным пилотом для компенсации межканальной интерференции. В результате работы получены зависимости коэффициента битовых ошибок от отношения энергии, приходящейся на бит информации, к энергии шума в различных  каналах.  Достигнут  коэффициент  ошибок  10−4  при  отношениях  энергии,  приходящейся  на  бит информации, к мощности шума, равных 13.4 дБ в первом канале, 15.3 дБ во втором и 20.9 дБ в третьем. Заключение. Система передачи на основе FBMC/OQAM с линейным эквалайзером может работать без циклического  префикса  в  беспроводном  канале  связи  с  многолучевостью,  обеспечивая  сравнимую  с OFDM-CP  помехоустойчивость.  Для  получения  большей  спектральной  эффективности  необходимо  использовать длинные кадры, поскольку в начале и конце кадра FBMC/OQAM имеется переходная зона

UNEMPLOYMENT TRENDS DURING ECONOMY CRISIS 2014-2015 IN RUSSIA

The article lists factors affecting the socio-economic situation and questions concerning unemployment in Russia are discussed specifically. The purpose is to identify weak points in the labor market. Visual support reflects the dynamics of unemployment in Russia during economy crisis. Unemployment trends by federal districts, the causes of regional unemployment imbalances are examined. The novelty of the author’s approach is to forecast the unemployment rate for future periods with expert assessments to determine the risk of deviation of unemployment from trend. Data were analyzed in terms of unemployment level in Europe and comparison with Russian indicators was conducted. Based on the research, causes of unemployment in Russia and ways of its decline were discovered. Appropriate conclusions were made

Unemployment trends during economy crisis 2014-2015 in Russia

Abstract: The article lists factors affecting the socio-economic situation and questions concerning unemployment in Russia are discussed specifcally. The purpose is to identify weak points in the labor market. Visual support refects the dynamics of unemployment in Russia during economy crisis. Unemployment trends by federal districts, the causes of regional unemployment imbalances are examined. The novelty of the author’s approach is to forecast the unemployment rate for future periods with expert assessments to determine the risk of deviation of unemployment from trend. Data were analyzed in terms of unemployment level in Europe and comparison with Russian indicators was conducted. Based on the research, causes of unemployment in Russia and ways of its decline were discovered. Appropriate conclusions were made

Concepts of the physical level of the fifth generation communications systems

The most promising technologies of signal forming and multiple access have been considered from the viewpoint of bandwidth-time resource usage. They include the full duplex technology, subcarrier forming method using a comb filter bank, the non-orthogonal multiple access method, and the sparse code multiple access method. The main existing implementation schemes of full duplex communication based on the analog and digital proper transmitter in the reception channel are described. The filtering multifrequency signal system using a bank of comb filters is considered. The spectrum of such signal is shown to have a much weaker out-of-band radiation as compared to the existing subcarrier forming techniques. The non-orthogonal multiple access method and the sparse code multiple access method are investigated, and relationships of the bit error rates as a function of the signal-to-noise ratio for communications systems based on these methods are presented. It has been shown that the multiple access methods under consideration are more effective in the bandwidth-time resource usage as compared to the existing technologies