OFDM (Orthogonal Frequency DivisionMultiplexing) is a multicarrier technique to increase the data rate of wireless channel. In OFDM, bandwidth is divided into many narrow bands whose carriers are orthogonal to one another. Implementation of OFDM deals with application of Fast Fourier Transform (FFT) to modulation and demodulation processes to generate carriers orthogonal to each other. In conventional system, IFFT (Inverse Fast Fourier Transform) is used at transmitter side and FFT is used in receiver side. There is need to append cyclic prefix at transmitter side to reduce the Inter symbol Interference (ISI) and to increase spectral efficiency. Recently there is proposition of Wavelet transform to generate sub channels with added advantage of flexibility of transform and high suppression in side lobes .This paper provides overview of performance of DWT (Discrete Wavelet Transform) based OFDM system as compared to FFT based OFDM system to reduce Inter carrier Interference caused due to sampling frequency offset in AWGN (Additive White Gaussian Noise) channel.

Orthogonal Frequency Division Multiplexing (OFDM) is an emerging multi-carrier modulation scheme. OFDM is sensitive to the carrier frequency offset (CFO) which may be caused due to difference in the carrier frequencies of transmitter and receiver. A well-known problem of OFDM is its sensitivity to frequency offset which occur due to the mismatch between transmitter and receiver local oscillator. Doppler shift and frequency offset introduces inter-carrier interference (ICI) in the OFDM symbol. Inter-carrier interference (ICI) is still a major concern OFDM system. It degrades the system performance significantly in multipath fading channels. Estimation of CFO are performed by using various methods, i.e. training sequence based and using pilot symbol. In this project work, we have done the estimation of CFO using pilot based. At the receiver, after serial to parallel conversion of the received signal, the cyclic prefix is removed first and then fed to an FFT block for de-multiplexing the multi-carrier signals. Following the FFT block, the pilot signals are extracted from the demultiplexed samples. The CFO estimation at pilot subcarriers is performed by MMSE. We send a pilot signal to the receiver, the pilot transmitted to receiver is separately and it compares the phases of all subcarriers at each OFDM symbol. When pilot is send only one input is known and others are zero then CFO is estimated by using set of equations After signal demodulation at the signal demapper, the information binary data is reconstructed at the receiver output. In this project, we focused on the estimation and reduction of CFO using MMSE and ZF techniques. The result shows the implementing equalization techniques like Zeroforcing (ZF) and Minimum mean square error (MMSE) for AWGN and Rayleigh fading channels. It improves the BER performance of the AWGN and Rayleigh channel. Index Term-OrthogonalFrequency Division Multiplexing (OFDM), Carrier Frequency Offset (CFO), Zero Forcing (ZF), Minimum Mean Square Error (MMSE).

orthogonal frequency division multiplexing (OFDM) is a form of multicarrier transmission technique used in today's modern wireless network's to achieve high speed data transmission with good spectral efficiency. OFDM offers advantages like Immunity to ISI, timing jitter and robust performance in multi path fading. Due to these advantages OFDM attracted a lot of attention in modern wireless networks like Digital audio broadcasting (DAB), Digital video broadcasting (DVB), Wireless local area network (WLAN), WiMAX etc.However the main drawback of OFDM system is that it is highly sensitive to the frequency offset among the subcarriers. The carrier frequency offset occurs due to mismatch in local oscillator frequency at the transmitter or receiver or by the Doppler phenomenon in mobile channels. This carrier frequency offset degrades the performance of OFDM system by introducing intercarrier interference (ICI). In this paper trained adaptive filtering based technique is proposed to mitigate the effect of intercarrier interference in OFDM system, which leads to the improvement in the performance of the system. Performance analysis of the system is carried out in terms of bit error rate (BER), intercarrier interference power (ICI) and carrier to interference ratio. (CIR)

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Orthogonal frequency division multiplexing is one of the potential scheme used in broadband communication systems to support high speed data transmission capability with excellent performance in multipath fading channel. The major benefit of OFDM scheme lies in its capability to convert frequency selective fading channel into flat faded channel, and its large spectral efficiency. However one of the negative aspect of OFDM system is its sensitive nature to the frequency offset present amongst the subcarriers. This Carrier frequency offset introduces Inter Carrier Interference (ICI), and this redundant ICI degrade the system performance. In this paper, first the authors have analyzed the error performance of QPSK modulated OFDM system in the existence of carrier frequency offset for Rayleigh multipath channel. Then Inter Carrier Interference power (ICI) and Carrier to Interference ratio (C/I) is analyzed for varying frequency offset. The authors have examined the increasing nature of Inter Carrier Interference (ICI) power and decreasing nature of Carrier to Interference ratio for varying frequency offset. Root Raised Cosine pulse shape based technique is proposed for the reduction of ICI and optimum value of roll-off factor is obtained for the minimum value of ICI.