Method and apparatus for modulating-demodulating OFDM multi-carrier-wave signal time frequency

Abstract

Training symbols with cyclic prefix are inserted to each basic part of head in phase of signal modulation. 0 is inserted to guard space of each OFDM symbol in basic frame. Discrete pilot carrier and continuous pilot carrier are setup inside OFDM symbol. Number of pilot carrier inside each OFDM symbol is equal. In phase of signal modulation, time synchronization and frequency correction are carried out based on tanning symbols. The invention also discloses equipment for the said modulation and demodulation method. The invention can carry out quick timing synchronous correction in time domain, and carry out quick estimating and correcting frequency deviation as well as can reduce signal transmission power.

Description

technical field [0001] The invention relates to the field of wireless transmission, in particular to a method and device for time-frequency modulation and demodulation of OFDM multi-carrier signals. Background technique [0002] Digital TV broadcasting is currently a research and application hotspot in the field of broadcasting. Many countries have launched their own digital TV broadcasting systems. The main industry standards include the Advanced Television System Committee (ATSC) digital TV standard in North America, the European Digital Video Broadcasting (DVB-T) standard, Terrestrial Integrated Services Digital Broadcasting (ISDB-T) standard in Japan and Satellite Digital Multimedia Broadcasting (DMB-T) in China T) standard. [0003] European DVB-T standard, Japanese ISDB-T standard and Chinese DMB-T standard all adopt Orthogonal Frequency Division Multiplexing (OFDM) multi-carrier modulation technology. OFDM is an efficient data transmission method. Its basic idea is ...

AI Technical Summary

Problems solved by technology

However, OFDM technology also has disadvantages: the method of OFDM technology to distinguish each sub-channel is to use the strict orthogonality between each sub-carrier, frequency offset and phase noise will deteriorate the orthogonality between each sub-carrier, only 1% Frequency deviation will reduce the signal-to-noise ratio by 30dB

[0005] However, this scheme has the following disadvantages: Since the guard interval is much smaller than the symbol length of OFDM, that is, the PN sequence is much smaller than the OFDM symbol, in order to achieve better synchronization performance, the current practice is to correlate multiple PN sequences Value summation, but this will increase the complexity of the calculation, resulting in slower synchronization speed; similarly, frequency offset estimation and correction also have the problem of more complex calculation and slower speed

In addition, inserting PN in the guard interval may also introduce interference

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