Method and system for estimating residual fractional frequency offset

A technology of frequency offset estimation and residual frequency offset, which is applied in multi-frequency code systems, baseband system components, shaping networks in transmitters/receivers, etc., can solve problems such as inability to correctly estimate residual frequency offsets, and achieve reduction Effects that affect, increase processing, and improve correctness and system stability

Inactive Publication Date: 2011-10-19
SICHUAN PANOVASIC TECH +1
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  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0012] 2. Influence of Doppler frequency shift on frequency offset estimation
Then the residual frequency offset f calculated by the existing technology r will traverse [f r -f d , f r +f d ], the residual frequency offset cannot be estimated correctly

Method used

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  • Method and system for estimating residual fractional frequency offset
  • Method and system for estimating residual fractional frequency offset
  • Method and system for estimating residual fractional frequency offset

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Embodiment 1

[0048] The method for estimating residual fractional multiple frequency offset of the present invention includes the steps of residual frequency offset calculation, Doppler estimation and accumulation. The residual frequency offset calculation is in [f r -f d , f r +f d ] range, obtain the residual frequency offset estimates of the maximum and minimum boundaries, where f r is the residual fractional frequency offset, f d is the maximum Doppler frequency shift, and eliminates the distortion point and phase overflow point caused by the dynamic multipath channel by setting the frequency deviation threshold. Because once the estimated value of the residual frequency offset in the calculation of the residual frequency offset is obtained, if there is no greater Doppler frequency shift, the statistical boundary will not be updated, so the locked frequency offset will not change. Therefore, when the maximum Doppler shift becomes small, the estimator will fail in the subsequent pr...

Embodiment 2

[0063] Such as Figure 5 As shown, the system for estimating the residual fractional frequency offset of the present invention includes a frequency offset calculation unit, a Doppler estimation unit and an accumulation unit, which are respectively used for the residual frequency offset calculation, Doppler estimation and accumulation in Embodiment 1 operation. Where Dpilot and Dpilot_delay are analyzed scattered pilot data of adjacent odd (or even) OFDM symbols, and symbol_num is OFDM symbols. In the frequency offset calculation unit, there is a threshold decision device that receives the input of the scattered pilot modulus and the scattered pilot phase. The received discrete pilot data Dpilot and Dpilot_delay of adjacent odd (or even) OFDM symbols are first calculated by the Cordic (coordinate rotation digital calculation) module to calculate the modulus and phase angle, and store the obtained modulus and phase angle in in RAM. The modulus is used to eliminate the distort...

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Abstract

The invention relates to a method and a sytem for estimating residual fractional frequency offset. The method comprises the following steps: residual frequency offset computing, Doppler estimation and accumulation; according to the difference of a dispersed pilot frequency module value and a dispersed pilot frequency phase angle, obtaining a residual frequency offset estimation value of maximum and minimum borders so as to eliminate a distortion point and a phase spill point caused by a dynamic multi-path channel; during the catching state of the Doppler estimation, reducing a border value through adding a decay factor in each time slot; judging whether to unlock according to the frequency offset border update quantity wherein the decay is not carried out under a locked state; and during the accumulation, accumulating OFDM symbols and the output of the each-time Doppler estimation to be compensated to a time domain end. In the residual fractional frequency offset estimation method disclosed by the invention, the processing of the Doppler frequency offset is increased, the influence of the Doppler frequency offset to a system is reduced, therefore, the residual fractional frequency offset in the dynamic multi-path channel can be accurately estimated, and the accuracy of the residual fractional frequency offset estimation and the stability of the system are improved.

Description

technical field [0001] The present invention relates to a method and a system for estimating a residual fractional multiple frequency offset, in particular to a method and a system for estimating a residual fractional multiple frequency offset in a CMMB system. Background technique [0002] The OFDM (Orthogonal Frequency Division Multiplexing) modulation technology used in CMMB (China Mobile Multimedia Broadcasting) has the advantages of strong anti-fading ability and simple implementation, and can well resist frequency selective fading caused by multipath effect . The disadvantage is that OFDM is very sensitive to carrier frequency offset. Carrier frequency offset includes: integer frequency offset and fractional frequency offset (FFO). The integer multiple frequency offset is an integer multiple of the subcarrier spacing. Although the integer multiple frequency offset will not destroy the orthogonality between subcarriers, it will cause the cyclic shift of the receiver d...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H04L27/26H04L25/02H04L25/03
Inventor 谢翔武畅吉磊李玉柏
Owner SICHUAN PANOVASIC TECH
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