We consider joint estimation of carrier frequency offset (CFO) and channel impulse response (CIR) for orthogonal frequency division multiplexing (OFDM) with pilot symbols. A new method based on compressed sensing is proposed. It has been shown that the CIR can be represented as a 1-block sparse signal by using a dictionary constructed by concatenating subspaces of CFO values taken from a search space. Recovery of both CFO and CIR is accomplished by the block orthogonal matching pursuit algorithm. The proposed method uses only one OFDM training block and does not require any initialization. The performance of the proposed method is compared against the well-established pilot based estimators: Moose, Classen, the maximum likelihood estimator, and the p-algorithm. Numerical results show that the performance of the proposed method does not depend on the value of the CFO. We also give worst-case upper bounds for the mean squared error of the CIR estimate for a sparse multipath channel.

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Özetçe -Bu çalışmada OFDM sistemleri için pilot sembole dayalı seyrek kanal kestirimi incelenmiştir. Pilot sembolü kullanarak yapılan kanal kestirimi, seyrek bir kanal için sıkıştırılmış algılama problemine dönüştürülmüştür. Farklı dogrusal modülasyon alfabelerinden pilot semboller üretilerek seyrek kanal algılama dizeyleri oluşturulmuştur. Sıkıştırılmış algılama analizinde kullanılan ortak evreuyumlulugu algılama dizeyleri için bulunmuştur. Karşılaştırmalı algılama başarımları kanal kestirim hatalarının ortalamasının karesi alınarak verilmiştir.Anahtar Kelimeler-Seyrek kanal kestirimi, sıkıştırılmış algılama, OFDM.Abstract-In this work pilot based sparse channel estimation for OFDM is investigated. Channel estimation using pilot symbols is cast into a compressed sensing problem for a sparse channel. Sensing matrices are constructed using pilot symbols from different linear modulation alphabets. Mutual coherence of these sensing matrices are computed. The channel estimation performances of different sensing matrices are given as mean squared errors.