1. A method for performing joint time synchronization and carrier frequency offset estimation in a wireless communication system, comprising: on a transmitting side: performing frequency domain spreading and interleaving on input data by using a predetermined spreading factor (SF) to generate a frequency domain multiple repetition training symbol; performing Inverse Discrete Fourier Transformation (IDFT) on the generated frequency domain multiple repetition training symbol to generate a first time domain comb shaped training symbol; reversely copying the generated first time domain comb shaped training symbol to a second time domain training symbol such that a complete central-symmetric comb-shaped training sequence is formed in the time domain; and on a receiving side: detecting an average power of received non-zero signals to judge the coming of the training sequence, and performing coarse frame synchronization; performing joint fine frame synchronization and carrier frequency offset estimation based on the received training sequence; and compensating for the carrier frequency offset based on the carrier frequency offset estimation result to eliminate the carrier frequency offset.