A carrier offset in OFDM system simulation is generally considered to be slowly time-varying, so that, over short simulation periods, it may be considered to be a constant quantity. However, depending on system mobility, carrier frequency, and communication duration, time-varying carrier offsets caused by Doppler effects can be significant in a real physical environment. Few researchers have addressed this in their works. Of those who have addressed this, many present simplified, vague, or inaccurate time-varying carrier offset models. In this paper, we present a more realistic time-varying carrier offset model and present expressions for carrier offset correction that maximize the signal-to-interference ratio (SIR). We also provide guidelines for when the application of the time-varying carrier offset model is crucial for correct OFDM system evaluation.

A carrier offset in OFDM system simulation is generally considered to be slowly time-varying, so that, over short simulation periods, it may be considered to be a constant quantity. However, depending on system mobility, carrier frequency, and communication duration, time-varying carrier offsets can be significant in a real physical environment. Few researchers have addressed this in their works. Those few who have, present simplified, vague, or inaccurate time-varying carrier offset models. The main goal of this paper is to present an accurate time- varying carrier offset model, and to provide guidelines for when the application of this model is crucial for correct OFDM system evaluation.

Satisfactory operation of orthogonal frequency-division multiplexing (OFDM) requires carrier frequency estimation with precision on the order of 1 to 2% of the subcarrier spacing. Numerous pilot-aided and blind algorithms that achieve this precision have been proposed. Blind algorithms are generally more complex than the pilot-aided algorithms. In this paper, we propose a novel low-complexity blind algorithm that takes advantage of a key property of the in-band OFDM power spectral density (PSD). To date, OFDM PSD research and modelling has mainly been directed towards reducing the out-of-band radiation. Here, we turn our attention to the in-band portion of the spectrum and show that it has an oscillatory variation. We show how this property can be used for carrier frequency tracking. Computer simulations show that the proposed algorithm works well in high-noise, frequency-selective channels.