Fast Accurate and Simple Carrier Acquisition Algorithm for OFDM Systems

In all wireless systems, the first operation that must take place at the receiver is the acquisition of the carrier and timing. OFDM systems are particularly sensitive to carrier offsets since this introduces inter-carrier interference and loss of signal power. An algorithm, termed MODSC, is devised in this paper which can estimate the Local Oscillator (LO) offset in a fast and efficient manner. The carrier offset can be brought to within one half the carrier spacing within 1 to 10 OFDM frames. By inserting a null in the center carrier, carrier acquisition can be easily accomplished by locating this null in the FFT bins at the receiver. The offset of this null from the designed position indicates the local oscillator offset in units of number of sub-carriers. An additional Guard Interval Based (GIB) algorithm is used to estimate the offset within one half the inter-carrier spacing. Together, the MODSC and GIB completely estimates the LO offset.