OFDM system carrier frequency offset estimation method and system based on pilot frequency

Abstract

The invention relates to an OFDM system carrier frequency offset estimation method and system based on pilot frequency. The method of the invention includes that firstly calculation of three formulas is carried out according to two output data of a continuous multi-carrier system of each carrier position sequence set Ck in multiple carriers, thus obtaining pilot frequency accumulated value Mk. The first output data is a mth sample value in the carrier position sequence set Ck corresponding to an ith multi-carrier output symbol, the sequence set of the first formula is conjugation of the firstoutput data, and the sequence set of the second formula is conjugation of the second output data. Then maximum of the pilot frequency accumulated value Mk is obtained, and parameter k value in the maximum Mk value is taken as the carrier frequency offset obtained by estimation. The invention solves the problem that interference is produced in integral multiple carrier frequency offset estimation when residual sampling clock frequency offset is larger, is applicable to continuous pilot frequency (DVB-T, CMMB) system with known fixed position and known data and is also applicable to pilot frequency (such ISDB-T) system with known fixed position and unknown data.

Description

technical field [0001] The present invention relates to digital communication systems, in particular to OFDM systems. Background technique [0002] Carrier recovery is a prerequisite for reliable information transmission in digital communication systems. In a single-carrier system, the carrier frequency offset will only cause certain attenuation and phase rotation to the received signal, which can be overcome by methods such as equalization. However, for an Orthogonal Frequency Division Multiplexing (OFDM) system that requires sub-carriers to maintain strict synchronization, the consequences of carrier frequency offset will be far more serious than single-carrier systems. If no measures are taken to prevent such inter-carrier interference ( ICI) will have a very serious impact on the system performance, and no matter how the signal transmission power of the OFDM system is increased, the system performance cannot be significantly improved. [0003] figure 1 is the OFDM sys...

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Problems solved by technology

[0022] (2) Integer carrier frequency offset will affect the phase of received data;

[0023] (3) Fractional carrier frequency offset not only directly affects the amplitude attenuation and phase rotation of received data, but also introduces inter-channel interference (ICI)

[0051] Although R k The energy value is larger, but due to this phase (11) the R k The value distribution is relatively scattered (1, 4 quadrants in 2K mode, 1, 2, 3, 4 quadrants in 8K mode), so It is not enough to clearly distinguish the maximum value from the second maximum value, that is, it cannot be used as a basis for reliably judging the estimated value of integer multiple carrier frequency offset

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