I.I. Lavrenyuk1, S.B. Makarov2, S.V. Zavjalov3

1−3 Peter the Great St. Petersburg Polytechnic University (Saint-Petersburg, Russia)

One of the most promising methods for solving the problem of increasing the efficiency of using the frequency resource of modern wireless communication systems is the application of signals with controlled intersymbol interference. Such artificial interference can be introduced in both the time and frequency domains, thus providing tools for increasing the symbol rate of information transmission and/or for controlling the occupied bandwidth. Accordingly, for effective detection of signals with artificial interference on the receiver side, it is necessary to apply detection algorithms that compensate for the influence of intersymbol interference, otherwise it is logical to expect an increase in energy losses. From the point of view of the practical application of this approach, the main obstacle and limitation is the extremely high computational complexity of existing algorithms for detection such signals. As a result, it becomes necessary to develop and study algorithms that provide a compromise between the energy efficiency of such a system and the computational complexity of the implementation of a signal detection scheme with artificial interference. This paper discusses the application of a relatively simple (from the point of view of computational complexity) algorithm with decision feedback and optimization of the observation interval for single-frequency signals with time-controlled interference. The signals are built on the basis of the known forms of amplitude pulses of the form of a square root of the raised cosine, as well as on the basis of the forms of pulses obtained as a result of solving the optimization problem. Variants for coherent and incoherent detection algorithms with feedback are considered, a moderate increase in energy efficiency is demonstrated while maintaining the computational complexity at a low level for relatively moderate levels of intersymbol interference in the signal. The paper gives an estimate of the BER performance for FTN signaling when applying algorithms of coherent and noncoherent processing with decision feedback with the optimal values of the observation interval at increased message transmission rates R > 1/T. Shown that it possible to ensure stable detection of binary signals with artificial interference up to symbol rates exceeding the Nyquist limit by a factor of ~2.85.

The optimal values of the observation interval for a wide range of transmission rates depend on the duration of the shaping pulses, but little depend on the transmission rate, both in the case of using coherent and noncoherent reception algorithms.

The effect of grouping errors, leading to a sharp decrease in the BER performance, begins to affect at transmission rates higher than R = 1.42/T in the region of small values of the signal-to-noise ratio and is more pronounced when using coherent processing algorithms.

Lavrenyuk I.I., Makarov S.B., Zavjalov S.V. Error-rate performance for signals with controlled intersymbol interference when applying  detection algorithms of symbol-by-symbol processing with decision feedback. Radiotekhnika. 2021. V. 85. № 11. P. 146−162.  DOI: https://doi.org/10.18127/j00338486-202111-19 (In Russian)

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