Abstract
In this work, an estimation algorithm based on the compressive sensing (CS) technique is proposed for an orthogonal frequency division multiplexing (OFDM) system applied to multi-path time-varying channels. A fitting polynomial is used to approximate each channel path, and full-band training symbols are adopted. The variation of the channel response can then be evaluated according to the observation on the inter-carrier interference (ICI) from the determinate signals. The CS-based technique is introduced to explore the sparsity of the double-selective channel and the usage of high-order fitting polynomials is allowed. The orthogonal matching pursuit (OMP) algorithm is designed to cooperate with the fitting polynomial model, and more accurate channel estimation results can be provided compared to those provided by conventional least-square (LS) algorithms. When multiple transmission antennas are required, the advantage of the proposed polynomial-fitting OMP (PF-OMP) algorithm is more obvious as more transmission antennas are used.
Highlights
Because of its high spectral efficiency and robustness against multi-path frequency-selective channel [1], orthogonal frequency division multiplexing (OFDM) is widely used in many communication systems
Rather than using a randomly constructed measurement matrix as with the conventional compressive sensing (CS) techniques, a VOLUME 7, 2019 structured measurement matrix is adopted in the proposed orthogonal matching pursuit (OMP) algorithm, which consists of the prediction for the inter-carrier interference (ICI) patterns that are derived from the cooperation of the full-band training symbols and the polynomial-approaching time-varying channel model
The channel estimation schemes are applied to an OFDM system where N = 64 and NCP = 16
Summary
Because of its high spectral efficiency and robustness against multi-path frequency-selective channel [1], orthogonal frequency division multiplexing (OFDM) is widely used in many communication systems. Rather than using a randomly constructed measurement matrix as with the conventional CS techniques, a VOLUME 7, 2019 structured measurement matrix is adopted in the proposed OMP algorithm, which consists of the prediction for the ICI patterns that are derived from the cooperation of the full-band training symbols and the polynomial-approaching time-varying channel model. If the channel response is time invariant in a single OFDM symbol duration, Htm will be a diagonal matrix, and each element of Y can only receive the signal from the corresponding elements of X, which means that the orthogonality can be maintained. SYSTEM MODEL CONSTRUCTION For the conventional channel estimation in the time-invariant environment, the pilot tones are usually inserted between the subcarriers that contain the data signals, and the pilots and data signals coexist in the same OFDM symbol. One of the most popular methods is the LS algorithm, and the LS estimation result is denoted as CNDt
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