Hybrid optical-radio communication systems provide high-speed access within the “last mile” and can act as highly reliable broadband channels of SCADA software and hardware systems. They use optical channels as the main communication lines, and radio channels as backup, since the transmission quality of atmospheric optical channels is largely determined by weather conditions. To reduce the effect of atmospheric turbulence, it is proposed to use the option of spatial diversity with line-of-sight channels and containing a repeater. When the signal-to-noise ratio decreases in the optical channel below the selected threshold, switching to the radio link is to be performed. The paper provides the results of modeling the operation of a hybrid radio-optical line in SCADA systems, in which a new switching system for optical and radio-frequency channels using a repeater is proposed. The dependences of the outage probability of the optical channel and the system as a whole are obtained.
исследована модель многоскачковой радиооптической системы атмосферной связи, работающей с применением кооперативного разнесения с несколькими ретрансляторами в каждом из каналов. В качестве резервного используется радиоканал, задействуемый при снижении отношения сигнал/шум ниже заданного порога во всех оптических каналах. Выбор рабочего канала производится на основании анализа состояния канала по минимаксному критерию. При дальнейшем снижении отношения сигнал/шум до предельного порога наступает состояние отказа системы. Для описания статистики оптических каналов применена экспоненциальная модель Вейбулла, для радиоканала – m-распределение Накагами. Приведены выражения для расчета величины битовой ошибки и вероятности отказа гибридной системы и атмосферной оптической линии связи (АОЛС), для расчета использована обобщенная квадратурная функция Гаусса-Лагерра. Аналогично представлены выражения для радиоканала, основанные на вычислении коэффициентов полиномиального разложения. Показаны зависимости битовой ошибки от среднего отношения сигнал/шум в каналах для различных атмосферных условий передачи, а также для различных сочетаний числа каналов и ретрансляторов в каждом из них. Сделан вывод о превалирующем влиянии на качество связи числа ретрансляторов в канале по сравнению с общим количеством каналов разнесения. Приведены зависимости вероятности отказа гибридной системы и АОЛС. Сделан вывод о возможностях повышения качества связи в системах такого типа the article studies a model of a multi-hop radio-optical atmospheric communication system using cooperative diversity with several relays in each channel. A radio channel is used as a backup, which is activated when the signal-to-noise ratio drops below a specified threshold in all optical channels. The choice of the working channel made based on the analysis of the channel state information according to the min-max criterion. With a further decrease in the signal-to-noise ratio to the limit threshold, a system outage condition occurs. The exponential Weibull model is used to describe the statistics of optical channels, and the Nakagami m-distribution is used for the radio channel. Expressions for calculating the bit error rate and the probability of failure of the hybrid system and FSO are given, the generalized Gauss-Laguerre quadrature function is used for the calculation. The expressions for the radio channel based on the calculation of the coefficients of the polynomial expansion are similarly presented. The dependences of the bit error rate on the average signal-to-noise ratio in the channels for various atmospheric transmission conditions, as well as for various combinations of the number of channels and relays in each of them are shown. The conclusion is made about the prevailing influence on the quality of communication of the number of repeaters in the channel compared to the total number of diversity channels. Dependences of the probability of failure of the hybrid system and FSO are given. The conclusion is made about the possibilities of improving the quality of communication in systems of this type
The results of modeling the operation of a radio-optical communication system using a channel containing one or more relays are presented. The dependences of the bit error rate for systems with different numbers of relays are given.
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