1. Carrier Frequency Offset Estimator Based on Unique Word Cross-correlation Riga Technical University Latvia Arturs Aboltins

2. Contents Communication system description; Carrier frequency offset (CFO); Estimation algorithms; Demonstration at work; Performance characteristics;

3. Communication system with block- wise time domain signal

4. 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

5. 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

6. Up conversion Carrier frequency

7. Down conversion

8. Impact of carrier frequency offset

9. CFO estimation methods Non-data aided (blind) Data aided (auto-correlation – AC) Data directed (cross – correlation - XC)

10. Auto correlation problem Popular in OFDM for fractional CFO estimation k

11. Cross correlation k

12. Proposed XC based algorithms 1. Average increment based method 3. Method for CAZAC sequences 2. Least squares based method

13. Synchronizer at work

14. SNR characteristics AWGN channel Frequency selective channel

15. Dependence on CFO