MODERN METHODS OF RADIOCOMMUNICATION CHANNEL ESTIMATION IN CONDITIONS OF MULTIPATH
The article discusses modern methods for estimating a mobile radio channel under conditions of multipath propagation of signals used in OFDM systems, based on the placement of pilot (experimental) data. For systems with orthogonal frequency multiplexing, the main types of positioning of pilot signals are shown, and allocation diagrams are displayed. Key varieties of data interpolation in OFDM are presented: linear, binary, discrete Fourier transform DFT, and interpolation using the MMSE minimum mean square error method. A block diagram is given and the principle of operation of the DFT interpolation is considered using discrete Fourier transform algorithms for N points. Modeling the estimation methods of mobile radio communication channel in the OFDM system with N s =64 subcarriers, N p =8 pilot symbols, signal modulation - QPSK was carried out. The Jake model with the Doppler frequency f d = 10 -4 and the number of beams L = 4 was used as a multipath radio channel. Evaluation of the effectiveness of the considered methods is carried out according to the dependences of bit and mean-square errors on the signal-to-noise ratio. The advantages of DFT interpolation over other types of approximations are presented. Results and conclusions are given in the conclusion of the article