Estimation of frequency offset in a communication system

Abstract

Frequency offset of a receiver employing frequency or phase shift keying is estimated by performing a pair-wise weighted summation of consecutive received training symbols, where each weighting factor is related to the ratio of the corresponding training symbols that were originally transmitted (known a priori). Specifically, the following sum is evaluated for the n symbol training sequence (y1, y2, . . . , yn) which is received when the training sequence (x1, x2, . . . , xn) is transmitted: ∑ k = 2 n ⁢ ⁢ y k · y k - 1 * · a k * = g · ⅇ j2 ⁢ ⁢ πΔ ⁢ ⁢ f ⁢ ⁢ T where g is a real constant and αk is defined by xk=αk·xk−1, αk* is the conjugate of αk, and T is the symbol period. Since the values of xk are predetermined, and αk can be determined by dividing two of these values, the preceding sum is readily calculated and yields an estimate for Δf by performing a single summation and placing the result in polar format.

Dependencies are inferred from the claim text.