Frequency and frame synchronisation for OFDM

摘要

The present invention is a method and device for synchronization at OFDM-systems. A signal is read into the synchronization block in the time domain, i.e. before fourier transforming of the signal via the FFT-processor, according to Figure 1. In the synchronization block the frame clock for start and input of data in the FFT-processor is regained. For OFDM-reception it is very important that this input starts at the right point of time to make possible detection of data. The point of time for the input to the FFT-processor is therefore adjusted in relation to the regained frame clock. When the frame clock has been regained the frequency error can be estimated, which is also performed in the synchronization block. The frequency error is utilized in a control loop for feed back to an oscillator which generates a complex rotating vector which is multiplied by the input signal for compensation of the frequency error. The invention can be utilized at OFDM-system with guard space or OFDM-system with pulse forming. <IMAGE>