I. Introduction
Orthogonal frequency division multiplexing (OFDM) is an efficient transmission technique for high speed data transmission. OFDM is already used or standardized in several wireline and wireless applications such as Digital Audio Broadcasting (DAB), Digital Video Broadcasting (DVB), universal mobile telecommunication system (UMTS), and wireless local area networks (WLAN's) [1]–[3]. The principle weakness of OFDM is its sensitivity to carrier frequency offset (CFO) caused by Dopper shifts and/or oscillator instabilities [4]. A CFO results in a shift of the received signal spectrum in the frequency domain. The CFO can be divided into an integer and a fractional part with respect to the OFDM subcarrier spacing . If the integer part of the CFO equals and the fractional part is zero, then the received subcarriers are shifted by in the frequency domain: the subcarriers are still mutually orthogonal, but the received data symbols, which are mapped to the OFDM spectrum, are in the wrong positions in the demodulated spectrum, resulting in a BER of. 5 [5]. In this paper, we concentrate on the estimation of the integer part of the CFO, i.e. the frequency ambiguity resolution. We assume that the fractional part of the CFO can be correctly estimated with another algorithm, and is corrected before the estimation of the integer CFO.