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1Wireless Communication Technologies

Summary

OFDM is a bandwidth efficient modulation technique that is tolerant to channel

disturbance such as delay spread multipath and impulse noise.

The principle of OFDM is to split high-rate data-streams into number of lower r

ate streams that are transmitted simultaneously over a number of sub-carriers.

To demodulate the OFDM subcarriers, it has to perform at least two synchroniz

ation tasks: symbol timing and frequency synchronization.

Frequency offset destroys the orthogonality between tones. It is important to ob

tain an accurate estimate of carrier frequency in order to minimize degradation.

OFDM has a higher PAPR than concentional single carrier systems. These attri

butes require that special attention be paid to the linearity of power amplifiers, o

r be taken to decrease the PAPR.

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References

[1] R. v. Nee, R. Prasad, OFDM for Wireless Multimedia Communications, Artech House Publishers, 2000.

[2] L-H Li, F-L Lin, and H-R Chuang, “Complete RF-System Analysis of Direct Conversion Receiver (DCR) for 802.11a WLAN OFDM System,” IEEE Transactions on Vehicular Technology, Vol. 56, No 4, pp.1696-1703, July 2007.

[3] T. Pollet, M. van Bladel and M. Moeneclaey, “BER Sensitivity of OFDM Systems to Carrier Frequency Offset and Wiener Phase Noise,” IEEE Trans. On Comm., Vol. 43, No. 2/3/4, pp. 191-193, Feb.-Apr. 1995.

[4] Anuj Batra, “Multi-band OFDM Physical Layer Proposal (ppt: 03267r1P802-15_TG3a-Multi-band-OFDM-CFP-Presentation),” IEEE P802.15 Working Group for Wireless Personal Area Networks, 2003. Available: http: //grouper.ieee.org/groups/802/15/pub/2003/Jul03/.

[5] I. Arsic, V. Stankovic, D. Drajic and Z. Nikolic, “Performance of the OFDM System,” IEEE TELSIKS 2001, Niš, Yugoslavia, pp. 767-768, September 19-21, 2001.

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References

[6] U. Tureli, H. Liu, M. D. Zoltowski, “OFDM blind carrier offset estimation: ESPRIT,” IEEE Trans. Commun, vol. 48, no. 9, pp. 1459-1461, Sep. 2000.

[7] A. Ren, Q. Yin, Y. Meng, “Carrier Frequency Offset Estimation for OFDM systems”, Circuits and Systems, 2005. ISCAS 2005. IEEE International Symposium on 23-26 May 2005 Page(s):3019 – 3022, Vol. 4.

[8] F.-L. Lin, S.-F. Chen, and H.-R. Chuang, “Computer Simulation of Nonlinear Effects of RF Power Amplifiers based on EVM and ACPR for Digital Wireless Communications”, Electronics Letter, vol. 36, no. 1, pp. 77-79, Jan. 2000.

[9] R. E. Ziemer, R. L. Peterson, Introduction to Digital Communication, Prentice Hall, Inc., 2001.

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