Method for joint time synchronization and frequency offset estimation in OFDM system and apparatus of the same

An apparatus for performing joint time synchronization and carrier frequency offset estimation in a wireless communication system, the apparatus comprising:

• a transmitter including:
• a variable spreading factor (SF) control unit to set a variable spreading factor;
• a frequency domain spreading and interleaving unit to spread and interleaving input data in frequency domain by using the spreading factor (SF) to generate a frequency domain training symbol;
• an Inverse Discrete Fourier Transformation unit to transform the frequency domain training symbol to generate a first time domain training symbol;
• a symbol reverse repetition unit to reverse copying the generated first time domain training symbol to a second time domain training symbol such that a central-symmetric comb-shaped training sequence is formed;
• a receiver including:
• a power detection and coarse frame synchronization unit to detect the power of received data and performing coarse frame synchronization on the received data when the training sequence is detected;
• a joint fine frame synchronization and carrier frequency offset estimation unit to perform joint fine frame synchronization and carrier frequency offset estimation on the received data based on the received training sequence.

A method of generating a training sequence for joint time synchronization and carrier frequency offset estimation in a wireless communication system, comprising:

• generating a spreading factor (SF);
• spreading and interleaving selected complex points on a constellation to generate a frequency domain training symbol;
• performing Inverse Discrete Fourier Transformation (IDFT) on the generated frequency domain training symbol to obtain a first time domain training symbol;
• and
• reversely repeating the generated first time domain training symbol to a second time domain training symbol such that a central-symmetric comb-shaped training sequence is formed.