Frame synchronization method and device for OFDM system

Abstract

The invention relates to a frame synchronization method for an OFDM system, which comprises the following steps: (a) carrying out self-correlation operation on a received signal sequence to obtain self-correlation results corr_auto (k); (b) selecting points at two sides of the peak value equal to a preset self-correlation decision threshold threshold_auto, respectively remarking the two points ask1 and k2, and finding the middle point k3 of the k1 and k2; (c) carrying out subsection cross-correlation operation on a signal sequence arranged between (k3-kfix) and (k3+kfix) and a local synchronous signal sequence, normalizing the result to obtain a normalized subsection cross-correlation result corr_cross(k), wherein the kfix is slightly larger than haft of the maximum multi-path time delay; and (d) taking the first peak point of subsection cross-correlation decision threshold threshold_cross in the subsection cross-correlation result corr_cross(k), adjusting the position of the received signal sequence according to the initial position of the frame, and outputting the received signal after synchronization. In the invention, the frame synchronization method not only can work in multi-path channel, but also can fight against larger carrier frequency offset.

Description

technical field [0001] The present invention relates to the communication field, in particular to a frame synchronization method and device for an OFDM (Orthogonal Frequency Division Multiplexing, Orthogonal Frequency Division Multiplexing) system. Background technique [0002] Frame synchronization is to make the time slot pulses of the receiving and sending ends of the communication system correspond to and keep consistent, so as to ensure that each channel is correctly transmitted and received, and there will be no confusion between the sending and receiving channels. [0003] CMMB (China Mobile Media Broadcasting, China Mobile Multimedia Broadcasting) system adopts OFDM (Orthogonal Frequency Division Multiplexing, Orthogonal Frequency Division Multiplexing) technology, which is an OFDM system. The OFDM system has high spectrum utilization rate and anti-multipath interference ability Strong and other advantages, but the OFDM system has high requirements for frame synchron...

AI Technical Summary

Problems solved by technology

This autocorrelation algorithm has a strong resistance to interference such as carrier frequency offset, but the autocorrelation curve of the received signal obtained by this method changes gently around the peak, which is the so-called flat-top effect, making it difficult for Gaussian noise. Accurately detect the starting position of the frame in large cases

[0005] It can be seen that the existing frame synchronization methods in OFDM systems using correlation algorithms cannot effectively counteract the impact of carrier frequency offset and multipath channels at the same time, so they cannot meet the frame synchronization requirements of systems using OFDM technology such as CMMB systems

Images