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Comparison of BER Performance in OFDM Using Different Equalization Techniques

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Author(s): Anuj Kanchan | Shashank Dwivedi

Journal: International Journal of Engineering and Advanced Technology
ISSN 2249-8958

Volume: 1;
Issue: 6;
Start page: 139;
Date: 2012;
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Keywords: Orthogonal Frequency Division Multiplexing (OFDM) | multipath propagation | fading channel | inter symbol interference (ISI).

ABSTRACT
The effects of frequency-selective channel conditions, for example fading caused by multipath propagation, can be considered as constant (flat) over an OFDM sub-channel if the sub-channel is sufficiently narrow-banded (i.e., if the number of sub-channels is sufficiently large). This makes frequency domain equalization possible at the receiver, which is far simpler than the time-domain equalization used in conventional single-carrier modulation. In OFDM, the equalizer only has to multiply each detected sub-carrier (each Fourier coefficient) in each OFDM symbol by a constant complex number, or a rarely changed value.Some of the sub-carriers in some of the OFDM symbols may carry pilot signals for measurement of the channel conditions (i.e., the equalizer gain and phase shift for each sub-carrier). Pilot signals and training symbols (preambles). Here we modelled OFDM system with equalizers. Two different equalizers, namely Zero Forcing (ZF) and Minimum Mean Square Error (MMSE), along with different tapping are used. The modulation with multicarrier is employed, which provides advantages like inter symbol interference (ISI) reduction, high reliability, and better performance in multi-path fading. These equalizers are adopted to remove the ISI generated in the transmitted data under various fading environments. The results show that, with MMSE and ZFE equalizers, the bit error rate (BER) performance is improved. Further, the BER performance of MMSE is superior to ZFE equalizer.
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