Carrier Frequency Offset Estimator Based on Unique Word Cross-correlation Riga Technical University Latvia Arturs Aboltins
Contents Communication 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 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)
Auto correlation problem Popular in OFDM for fractional CFO estimation k
Cross correlation k
Proposed XC based algorithms 1. Average increment based method 3. Method for CAZAC sequences 2. Least squares based method
Synchronizer at work
SNR characteristics AWGN channel Frequency selective channel
Dependence on CFO