Adaptive Channel Estimator Design for OFDM-Based Wireless Communication Systems. Reporter : Yen-Ming Huang Date : 2012 . 11 . 22 . Outline. Motivation Introduction Interpolation Criterion in Frequency Domain Interpolation Criterion in Time Domain
Reporter : Yen-Ming Huang
Date : 2012 . 11 . 22
Based on the estimated CIR within CP length
In practical, the temperature and the bandwidth are known to receiver. Therefore, we may have the information of noise in advance.
The real and the imaginary part of noise follow Gaussian probability distribution.
Rayleigh probability derived from complex Gaussian variables is exploited.
Although the larger value of threshold can achieve more complete noise reduction, the taps with slight channel energy will be removed possibly.
There are two main causes of distortion associated with the carrier frequency. One is the non-coherent up and down frequency conversion accompanied with an unavoidable difference due to physically inherent nature of the transceiver oscillators. The other is caused by Doppler shift due to the transceiver mobility.
CP-Based Estimator :
LOS-Based Estimator :
Most of the maximum Doppler offset can be compensated with the proper schemes in the Rician fading channel. Broadly speaking, the LOS component usually emerges on the first arrival propagation path, and the Rician factor enlarges its weight diminishing the affection of scattered components.
Owing to the performance of linear interpolation highly depends on pilots, noise reduction on them makes an improvement as expected.
Although more MAWs mitigate the effect of noise evidently, it means the requirement of constant in several time-slots must to be satisfied.
When the rise of velocity such that the technique of Moving Average is unsuitable to use especially at high SNR, DFT-based transition is an alternative way. By inherent time domain processing, the goal of noise reduction on pilots can be achieved.
In order to make the frequency domain interpolation more robust to such large delay spread scenario, the time domain interpolation may be performed prior to the frequency domain interpolation.
 J. J. van de Beek, 0. Edfors, M. Sandell. S. K. Wilson and P. 0. Borjesson, “On channel estimation in OFDM systems,” Proc. IEEE Vehicular Technology Conf. vol. 2, Jul. 1995, pp. 815-819.
 X. Hou, Z. Zhang, and H. Kayama, “Low-Complexity Enhanced DFT-based Channel Estimation for OFDM Systems with Virtual Subcarriers,” in Proc. IEEE PIMRC’07, Sep. 2007.
 Szu-Lin Su, Yung-Chuan Lin, Chieh-Chih Hsu, and Gene C. H. Chuang, “A DFT-based Channel Estimation Scheme for IEEE 802.16e OFDMA Systems,”International Conference on Advanced Communication Technology, (ICACT10), IEEE Press, 2010, pp.775-779.
 J. van de Beek, M. Sandell, and P. Börjesson, “ML estimation of timing and frequency offset in OFDM systems,” IEEE Trans. Signal Processing, vol. 45, no. 7, pp. 1800–1805, Jul. 1997.
 F. Classen and H. Meyr, “Frequency synchronization algorithms for OFDM systems suitable for communication over frequency selective fading channels,” in Proc. IEEE VTC’94, Stockholm, Sweden, Jun. 1994, pp. 1655–1659.
 L. Yang, G. Ren, and Z. Qiu, “A novel Doppler frequency offset estimation method for DVB-T system in HST environment,” IEEE Trans. Broadcasting, vol. 58, no. 1, pp. 139–143, Mar. 2012.
 F. Foroughi, J. Lofgren, and O. Edfors, "Channel estimation for a mobile terminal in a multi-standard environment (LTE and DVB-H)," in Signal Processing and Communication Systems, 2009. ICSPCS 2009. 3rd International Conference, pp. 1-9, 2009.
 F. Foroughi, F. Sharifabad, and O. Edfors, “Low complexity channel estimation for LTE in fast fading environments for implementation on Multi-Standard platforms,” in proc. IEEE Vehicular Tech. Conf., Ottawa, September 2010.
Thanks for your attention.