Current Estimation of Impulse Response for OFDM Systems in Channels with Intersymbol Interference

The determination of the impulse response of a communication channel is necessary for organizing optimal processing of received signals, which indicates the relevance of studying OFDM systems and their modifications for channels with intersymbol interference. Taking these circumstances into account, the purpose of the study is formulated as estimation of the impulse response of the communication channel with minimization of the estimation error.

In this work, methods of least squares and regularization are used to compute the impulse response, while the estimation is performed with the selection of optimal OFDM test signals. At the initial stage, estimation of the impulse response is carried out by the least squares method for known OFDM test signals. An important aspect of the computational process is the proper choice of the regularization parameter value to minimize the systematic bias of the regularized estimates.

Results. In the course of solving the scientific problem experimental studies have been obtained that confirm the effectiveness of the proposed method for estimating the impulse response in combination with optimal test signals, demonstrating a small deviation of the estimated values.

Scientific novelty of the work is determined by the proposed algorithm for dynamically varying communication channels with on-line estimation, which provides continuous refinement of the channel impulse response and improves the quality of signal reception.

The practical significance of the developed algorithm lies in the fact that it can be used to estimate the impulse response in OFDM systems and their modifications: N OFDM, which involves the use of non orthogonal channel allocation techniques; COFDM technology (Coded Orthogonal Frequency Division Multiplexing), which implements additional coding with forward error correction; OFDMA technology (Orthogonal Frequency Division Multiple Access), which ensures joint use of a single frequency simultaneously by several network users in the presence of intersymbol interference in the communication channel.

The obtained experimental results demonstrate a significant improvement in the quality of coherent signal reception when using the proposed algorithms for impulse response estimation in combination with the selected test signal combinations in OFDM systems with intersymbol interference.

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