Time-frequency estimation method of OFDM (Orthogonal Frequency Division Multiplexing) structure of satellite CMMB (China Mobile Multimedia Broadcasting) system

Abstract

The invention discloses a time-frequency estimation method of an OFDM (Orthogonal Frequency Division Multiplexing) structure of a satellite CMMB (China Mobile Multimedia Broadcasting) system, wherein a frequency domain pilot symbol and a time domain pilot symbol are orderly inserted into an original data symbol to form an OFDM symbol, and the OFDM symbol is transmitted as a transmission signal. By the time-frequency estimation method provided by the invention, the OFDM structure of the satellite CMMB system can simultaneously balance the multipath interference of the frequency domain and compensate the Doppler interference of the time domain, and solves the technical problem that the conventional system cannot simultaneously perform time domain channel estimation and frequency domain channel estimation in single channel estimation mode, so that the system has more optimal channel estimation precision, the effect of channel compensation and balancing is improved greatly, and finally, the transmission performance of the system in satellite multipath channel environment is improved remarkably.

Description

technical field [0001] The invention belongs to the technical field of mobile communication, and relates to a time-frequency estimation method of the satellite CMMB system OFDM system. Background technique [0002] In 2009, the China Mobile Multimedia Broadcasting (CMMB) technical research working group released the standard "Mobile Multimedia Broadcasting Part 9: Satellite Distribution Channel Frame Format, Channel Coding and Modulation", which is used in the satellite mobile broadcasting communication system In , an Orthogonal Frequency Division Multiplexing (OFDM) transmission system will be adopted. [0003] The OFDM system belongs to a multi-carrier communication system. It has a higher spectrum utilization rate than the general system and strong anti-interference performance. These advantages make it widely used in terrestrial wireless mobile communications, and in satellite mobile communication systems. also received more and more attention. However, the harsh satel...

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Problems solved by technology

[0005] (1) Establish a time-domain channel estimation method of the training sequence, and "train" the channel response characteristics through the training sequence, so as to obtain specific channel response information, and then realize channel estimation; but this method needs to execute a computationally complex Deconvolution matrix operation, and because the training sequence does not change for a long time, the obtained channel characteristics are only suitable for constant parameter channels or quasi-stationary channels, not suitable for deep fading, fast fading and random parameter channel of mobile satellite multimedia broadcasting channels. channel and other characteristics, and the frequency domain information of the channel cannot be obtained

[0006] (2) A channel estimation method based on frequency-domain pilots. This method inserts distributed pilot information into frequency-domain data symbols, and estimates channel response characteristics through pilot information, thereby obtaining frequency-domain response information of the channel. The advantage of this method is that it can track the rapid change of channel frequency domain response; but this method is only suitable for statistical channel response under slow fading conditions, for fast fading channels with large Doppler frequency offset, due to the lack of channel Time-domain characteristic information - Doppler frequency offset and the phase error caused by it, its application performance will be greatly reduced

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