1. A fine timing method comprising: calculating first timing metric values based on cross-correlation between a received signal and M training sequences; identifying within a time period a set of X first timing metric values spaced according to a certain pattern which set of X first timing metric values has a greatest summation; and determining a beginning of a data frame based on the identified set of X first timing metric values, wherein the first timing metric values are calculated based on multiplication of M 1 (d) and M 1 (d+P·L), where M 1 (d) represents a cross-correlation function between the received signal and the M training sequences, L stands for the length of one training sequence, P is a predetermined positive integer and 1≤P≤M−2, X equals to M−P.