Abstract
We performed analysis of effectiveness of various methods and criteria of space-time processing of the signals by an adaptive antenna array with a view to identifying the algorithm suitable for using in arrangement of space-time access to mobile communication systems. It was shown that all methods are based on the assessment of an integrated vector of weight coefficients, included in the reception tract of every antenna element and controlled by certain algorithms. It was shown that recursive procedures that make it possible to correct the vector of weight coefficients in the dynamic situation, including non-stationary signal-interference situation, are more constructive for using in problems of space-time access. This is especially important for communications with mobile subscriber stations and allows reducing the time for processing calling signals due to the rapid convergence of recursive procedures. A comparative analysis of Widrow-Hoff and Kalman-Bucy algorithms was conducted. It was shown that the Kalman-Bucy procedure, in addition to optimality, in complicated signal-interference situation is characterized by maximally short time of convergence to the sustainable state. The convergence of the procedure is ensured on the time interval, allocated for the action of calling signals of subscriber stations in a mobile network. We proposed the model for studying the influence of initial conditions on the effectiveness of space-time access by the parameter of the convergence rate of the algorithm for adaptive space-time signal processing in an antenna array. It is possible to approximate the vector value to the optimal due to configuration of the integrated vector of weight coefficient based on the use of the information about directions of arrival of calling signals of subscriber stations in a mobile network. The results of the calculations of the indicator of the signal/(interference + noise) ratio on the convergence pitch for different algorithms of an adaptive antenna array were obtained. It was shown that it was possible to improve essentially the transitive characteristics of the algorithms for a linear four-element adaptive antenna array due to the successful initial choice of the value of the integrated vector of weight coefficients. This made it possible to increase the value of the signal/ (interference + noise) ratio at the outlet of an antenna up to 4 dB
Highlights
In recent years, there has been a substantial development of wireless technologies of subscriber access, designed to improve the quality of services of wireless Internet and mobile communication systems
With the implementation of mobile connection technologies of the 5th generation, the load on the mobile connection lines is supposed to increase substantially by 2020, which is caused both by an increase in the number of users and by the emergence of new services related to high-speed data transmission
The main reasons for a decrease in performance of a mobile communication system and its throughput is the existence of inter-channel interference, caused by the increasing number of users, interferential freezing of signals, signals delay during the radio waves propagation, which is caused by multi-beams, as well as by users’ mobility
Summary
There has been a substantial development of wireless technologies of subscriber access, designed to improve the quality of services of wireless Internet and mobile communication systems. When using STA, non-linearity and limitations of a dynamic range have a significantly smaller influence The application of these methods makes it possible to save the parameters of useful signals, requirements for the communication channels, and communication modes without increasing the allocated frequency band. That is why scientific studies that deal with the development of the systemic scientific and technical solutions in terms of improving the performance of access in mobile communication systems are relevant This can be achieved through the use of antenna arrays and the methods for adaptive space-time signal processing while providing a desired quality of services and constancy of the basic algorithms of mobile network functioning
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