Joint timing and frequency synchronization in coherent optical OFDM systems

doi:10.1007/s12200-019-0868-7

Front. Optoelectron.

2019, Vol. 12

Issue (1) : 4-14 https://doi.org/10.1007/s12200-019-0868-7

REVIEW ARTICLE

Joint timing and frequency synchronization in coherent optical OFDM systems

Xinwei DU^1,^2,³, Pooi-Yuen KAM¹, Changyuan YU³(

)

¹. Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117583, Singapore
². National University of Singapore (Suzhou) Research Institute, Suzhou 21512, China
³. Department of Electrical and Information Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China

Download: PDF(1127 KB) HTML
Export: BibTeX | EndNote | Reference Manager | ProCite | RefWorks

Abstract

In this paper, we review our joint timing and frequency synchronization algorithms in coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems. We first present a timing estimation method by designing the pattern of the training symbol, whose timing metric has a sharp and clear peak, to ensure accurate timing offset (TO) estimation performance. Then we provide both data-aided (DA) and blind (BL) approaches to estimate the carrier frequency offset (CFO). For the DA algorithm, we utilize the same training symbol structure as the timing estimation does, while for the BL algorithm, we utilize the zero-subcarrier power (ZSP) to achieve full-range CFO estimation. Note that our joint timing and frequency synchronization approaches require only one OFDM symbol, which ensure not only the data transmission efficiency, but also the TO and CFO estimation performance. A modified BL ZSP algorithm is proposed to further improve the CFO estimation performance by taking the power average over a series of OFDM symbols. The effectiveness of the TO estimation algorithm, and both the DA and BL CFO estimation algorithms are verified and demonstrated in both simulations and experiments.

Keywords timing offset (TO) carrier frequency offset (CFO) coherent optical orthogonal frequency division multiplexing (CO-OFDM) zero-subcarrier power (ZSP)

Corresponding Author(s): Changyuan YU

Online First Date: 15 April 2019 Issue Date: 29 April 2019

Cite this article:

Xinwei DU,Pooi-Yuen KAM,Changyuan YU. Joint timing and frequency synchronization in coherent optical OFDM systems[J]. Front. Optoelectron., 2019, 12(1): 4-14.

URL:

https://academic.hep.com.cn/foe/EN/10.1007/s12200-019-0868-7
https://academic.hep.com.cn/foe/EN/Y2019/V12/I1/4

Fig.1 Amplitude spectrum. (a) Without CFO; (b) with

ε = 0.2

Fig.2 (a) Amplitude spectrum with

ε = 10

; (b) power of zero-subcarrier vs. various integral CFOs for compensation, with the actual CFO of 0

Fig.3 (a) Transmitter and (b) receiver of a CO-OFDM system. S/P: serial to parallel, CP: cyclic prefix, Mod./Demod.: modulator/demodulator, ADC: analog to digital converter, Comp: compensation, Equal.: equalization, LO: local oscillator

Fig.4 Timing metrics of Schmidl’s, Minn’s, Park’s and proposed methods, with

τ = 10

and (a) no AWGN; (b) SNR= 5 dB

Fig.5 (a) Probability of correct timing estimation vs. SNR with

τ = 10

; (b) BER comparison of Schmidl’s, Minn’s, Park’s and the proposed methods vs. received optical power

Fig.6 (a) CFO estimation error variance vs. OSNR under different CFOs; (b) BER vs. OSNR with and without CFO compensation

Fig.7 (a) Estimation error variance; (b) BER vs. normalized CFO under the OSNR of 12 and 18 dB

Fig.8 Estimation error variance (a) vs. the number of symbols used for power average; (b) vs. number of zero-subcarriers, with the CFO of 5 GHz.

Fig.9 Estimation error variance (a) vs. SNR under AWGN channel with CFO of 5 GHz; (b) vs. the transmission distance, with the CFO of 5 GHz, CLW of 100 kHz and dispersion parameter is 17 ps/nm/km, at 15 dB SNR

1	WShieh, I Djordjevic. OFDM for Optical Communications. Burlington: Academic Press, 2009
2	WShieh, C Athaudage. Coherent optical orthogonal frequency division multiplexing. Electronics Letters, 2006, 42(10): 587–589 https://doi.org/10.1049/el:20060561
3	SHara, R Prasad. Multicarrier Techniques for 4G Mobile Communiations. Norwood, MA: Artech House, 2003
4	TPollet, M Van Bladel, MMoeneclaey. BER sensitivity of OFDM systems to carrier frequency offset and wiener phase noise. IEEE Transactions on Communications, 1995, 43(2–4): 191–193 https://doi.org/10.1109/26.380034
5	HAbdzadeh-Ziabari, W PZhu, M N SSwamy. Joint maximum likelihood timing, frequency offset, and doubly selective channel estiamtion for OFDM systems. IEEE Transactions on Vehicular Technology, 2018, 67(3): 2787–2791 https://doi.org/10.1109/TVT.2017.2728008
6	D DLin, R A Pacheco, T J Lim, D Hatzinakos. Joint estimation of channel response, frequency offset, and phase noise in OFDM. IEEE Transactions on Signal Processing, 2006, 54(9): 3542–3554 https://doi.org/10.1109/TSP.2006.879265
7	J Jvan de Beek, MSandell, P OBorjesson. ML estimation of time and frequency offset in OFDM systems. IEEE Transactions on Signal Processing, 1997, 45(7): 1800–1805 https://doi.org/10.1109/78.599949
8	T MSchmidl, D C Cox. Robust frequency and timing synchronization for OFDM. IEEE Transactions on Communications, 1997, 45(12): 1613–1621 https://doi.org/10.1109/26.650240
9	HMinn, M Zeng, V KBhargava. On timing offset estimation for OFDM systems. IEEE Communications Letters, 2000, 4(7): 242–244 https://doi.org/10.1109/4234.852929
10	BPark, H Cheon, CKang, DHong. A novel timing estimation method for OFDM systems. IEEE Communications Letters, 2003, 7(5): 239–241 https://doi.org/10.1109/LCOMM.2003.812181
11	XDu, J Zhang, ZXu, CYu. A novel timing estimation method for coherent optical OFDM systems. In: Proceedings of Asia Communications and Photonics Conference. Optical Society of America, 2015, paper AS4F. 5
12	XDu, J Zhang, YLi, CYu, P Y Kam. Efficient joint timing and frequency synchronization algorithm for coherent optical OFDM systems. Optics Express, 2016, 24(17): 19969–19977 https://doi.org/10.1364/OE.24.019969 pmid: 27557272
13	SCao, S Zhang, CYu, P YKam. Full-range pilot-assisted frequency offset estimation for OFDM systems. In: Proceedings of Optical Fiber Communication Conference/National Fiber Optic Engineers Conference. Optical Society of America, 2013, paper JW2A. 53
14	XZhou, K Long, RLi, XYang, Z Zhang. A simple and efficient frequency offset estimation algorithm for high-speed coherent optical OFDM systems. Optics Express, 2012, 20(7): 7350–7361 https://doi.org/10.1364/OE.20.007350 pmid: 22453415
15	JWu, M Tang, LXu, SZhu, J Cheng, ZFeng, LZhang, XWang, R Lin, LDeng, SFu, P P Shum, D Liu. A robust and efficient frequency offset correction algorithm with experimental verification for coherent optical OFDM system. Journal of Lightwave Technology, 2015, 33(18): 3801–3807 https://doi.org/10.1109/JLT.2015.2445923
16	D KKim, S H Do, H K Lee, H J Choi. Performance evaluations of the frequency detectors for orthogonal frequency division multiplexing. IEEE Transactions on Consumer Electronics, 1997, 43(3): 776–783 https://doi.org/10.1109/30.628707
17	Y JHuang, S W Wei. Modified guard band power detection for coarse carrier frequency offset receovery in OFDM system. Wireless Personal Communications, 2008, 45(2): 163–173 https://doi.org/10.1007/s11277-007-9406-9
18	XDu, J Zhang, C,Yu P Y.Kam Blind carrier frequency offset estimation for coherent optical OFDM systems. In: Proceedings of Advanced Photonics (IPR, NOMA, Sensors, Networks, SPPCom, SOF). Optical Society of America, 2016, paper SpW2G.3
19	PZhu, J Li, HZhao, YTian, Y Chen, ZWu, ZChen, Y He. An iterative frequency offset estimation method for coherent optical OFDM system. IEEE Photonics Technology Letters, 2017, 29(11): 877–880 https://doi.org/10.1109/LPT.2017.2693378
20	JJignesh, B Corcoran, CZhu, ALowery. Simple optoelectronic frequency-offset estimator for coherent optical OFDM. Optics Express, 2017, 25(25): 32161–32177 https://doi.org/10.1364/OE.25.032161 pmid: 29245880

[1]	Jean TEMGA,Deming LIU,Minming ZHANG. Improved pilot data aided feed forward based on maximum likelihood for carrier phase jitter recovery in coherent optical orthogonal frequency division multiplexing[J]. Front. Optoelectron., 2014, 7(4): 493-500.
[2]	Changyuan YU,Pooi-Yuen KAM,Shengjiao CAO. Carrier recovery in coherent receiver of optical orthogonal frequency division multiplexing system[J]. Front. Optoelectron., 2014, 7(3): 348-358.

Viewed

Full text

Abstract

Cited

Shared

Discussed