Carrier Frequency Offset Estimator Based on Unique Word Cross-correlation

Carrier Frequency Offset Estimator Based on Unique Word Cross-correlationRiga Technical UniversityLatviaArturs AboltinsContentsCommunication system description;Carrier frequency offset (CFO);Estimation algorithms;Demonstration at work;Performance characteristics;

Communication system with block-wise time domain signal

Possible contents of the data fieldComplex-valued (QAM, QPSK, BPSK, ) samplesDiscrete unitary transform of samplesDiscrete Fourier Transform (OFDM-like)Parametric transform

Parametric communication systemsPossible contents of UW fieldFor frequency offset estimation any determined (non-random) sequence can be used.

Since the same sequences are reused for other tasks (channel estimation, timing estimation), Chu-Zadoff sequences are chosenUp conversion

Carrier frequency

Down conversion

Impact of carrier frequency offset

CFO estimation methodsNon-data aided (blind)Data aided (auto-correlation AC)Data directed (cross correlation - XC)

Auto correlation

problemPopular in OFDM for fractional CFO estimationk

Cross correlation

kProposed XC based algorithms1. Average increment based method

3. Method for CAZAC sequences

2. Least squares based method

Synchronizer at work

SNR characteristics

AWGN channelFrequency selective channelDependence on CFO