Carrier Frequency Offset Estimator Based on

Arturs Aboltins
Carrier Frequency Offset
Estimator Based on Unique Word
Riga Technical University
Communication system description;
Carrier frequency offset (CFO);
Estimation algorithms;
Demonstration at work;
Performance characteristics;
Communication system with blockwise time domain signal
Possible contents of the data field
1. Complex-valued (QAM, QPSK, BPSK, …) samples
2. Discrete unitary transform of samples
• Discrete Fourier Transform (OFDM-like)
• Parametric transform
• …
Parametric communication systems
Possible contents of UW field
For 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 chosen
Up conversion
Carrier frequency
Down conversion

Impact of carrier frequency offset
CFO estimation methods
• Non-data aided (blind)
• Data aided (auto-correlation – AC)
• Data directed (cross – correlation - XC)
Meyr, H., Moeneclaey, M., & Fechtel, S. A.
(1998). Digital Communication Receivers:
Synchronization, Channel Estimation, and
Signal Processing. Signal Processing (p. 827).
Auto correlation
Popular in OFDM for fractional CFO estimation
Cross correlation
Proposed XC based algorithms
1. Average increment based method
2. Least squares based method
3. Method for CAZAC sequences
Synchronizer at work
SNR characteristics
AWGN channel
Frequency selective channel
Dependence on CFO

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