Similar articles

Abstract: As one of the most important components of the wideband wireless access technique, orthogonal frequency division multiplexing (OFDM) has a high usage rate of spectrum and combats inter-symbol interference (ISI) in multi-path fading channel. However, when there are frequency offsets during the signal transmission, the inter-carrier interference (ICI) is introduced, which significantly degrades the performance. The existing ICI self-cancellation schemes such as PCC-OFDM are not optimum to minimize the interference considering both noise and ICI. In this paper, a new metric named SINR (signal-to-interference-and-noise ratio) is proposed. We discuss the optimization issue when a constant frequency offset exists and in time-varying channels. The optimum weighting-coefficient-pair (OWCP) is obtained, which maximizes SINR theoretically through the alternant iteration algorithm. Simulations show that the performance of OWCP-OFDM is better than that of PCC-OFDM, especially when the frequency offset is large. Although the ICI self-cancellation scheme suffers bandwidth inefficiency, from the simulation results we can also see that the performance of OWCP-OFDM is much better than that of the standard OFDM systems with the same bandwidth efficiency when a frequency offset exists. Moreover, since the redundant modulation provides the capability to suppress ICI as well as a receiving SNR gain, it can be considered as exchanging the bandwidth for SNR.

[1] Ahn, J., Lee, H.S., 1993. Frequency domain equalization of OFDM signal over frequency nonselective Rayleigh fading channels. Electron. Lett., 29(16):1476-1477.

[2] Al-Dhahir, N., 1996. Optimum finite-length equalization for multicarrier transceivers. IEEE Trans. on Commun., 44(1):56-64.

[3] Armstrong, J., 1999. Analysis of new and existing methods of reducing intercarrier interference due to carrier frequency offset in OFDM. IEEE Trans. on Commun., 47(3):365-369.

[4] Cimini, L.Jr., 1985. Analysis and simulation of a digital mobile channel using orthogonal frequency-division multiplexing. IEEE Trans. on Commun., 33(7):665-765.

[5] Li, R., Stette, G., 1995. Time-limited orthogonal multicarrier modulation schemes. IEEE Trans. on Commun., 43(234):1269-1272.

[6] Li, Y., Cimini, L.J.Jr., 2001. Bounds on the interchannel interference of OFDM in time-varying impairments. IEEE Trans. on Commun., 49(3):401-404.

[7] Muschallik, C., 1996. Improving an OFDM reception using an adaptive Nyquist windowing. IEEE Trans. on Consum. Electron., 42(3):259-269.

[8] Robertson, P., Kaiser, S., 1999a. Analysis of the Loss of Orthogonality Through Doppler Spread in OFDM Systems. Proc. GLOBECOM, 1b:701-706.

[9] Robertson, P., Kaiser, S., 1999b. The Effects of Doppler Spreads in OFDM(A) Mobile Radio Systems. Proc. VTC, 1:329-333.

[10] Russell, M., Stuber, G.L., 1995. Interchannel Interference Analysis of OFDM in a Mobile Environment. Proc. VTC, 2:820-824.

[11] Zhao, Y.P., Haggman, S.G., 2001. Intercarrier interference self-cancellation scheme for OFDM mobile communication systems. IEEE Trans. on Commun., 49(7):1185-1191.