A difference method of the gravity center with double pilots for the MC-CDMA system

A difference carrier detector with two pilots adapting to a fast fading channel is presented. At the transmitter, two pilots of equal frequency distance to the carrier with one placed on the left and one on the right of the carrier are used. At the receiver, the pilots expand to two Doppler bands due to multi-path transmission and Doppler shift. The pilot signals are passed through two narrow band filters and down-converted to base band with the local carrier. The frequency offset between the local carrier and the transmitter one is obtained when the difference of the gravity centers of the two pilot spectrum is computed.