International Journal of Science, Engineering and Computer Technology

Ramandeep ¹, Rajesh Kumar ¹, Munna Devi ¹

Affiliations
1 Department of ECE, MITM, Jevra, Hisar, Haryana, IN

Abstract

The channel estimation techniques for OFDM systems based on pilot arrangement are investigated. The channel estimation based on comb type pilot arrangement is studied through different algorithms for both estimating channel at pilot frequencies and interpolating the channel. The estimation of channel at pilot frequencies is based on LS and LMS while the channel interpolation is linear interpolation, second order interpolation, low-pass interpolation, spline cubic interpolation, and time domain interpolation. Time-domain interpolation is obtained by passing to time domain through IDFT, zero padding and going back to frequency domain through DFT. In addition, the channel estimation based on block type pilot arrangement is performed by sending pilots at every sub-channel and using this estimation for a specific number of following symbols. We have also implemented decision feedback equalizer for all sub-channels followed by periodic block-type pilots. We have compared the performances of all schemes by measuring bit error rate with 16QAM, QPSK, DQPSK and BPSK as modulation schemes, and multipath rayleigh fading and AR based fading channels as channel models.

Keywords

Channel Estimation Techniques, OFDM Systems.

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Ramandeep ¹, Rajesh Kumar ¹, Munna Devi ¹

Affiliations
1 Department of ECE, MITM, Jevra, Hisar, Haryana, IN

Abstract

The future wireless mobile communication systems will be required to support high-speed transmission rate. Direct sequence code-division multiple access (DS-CDMA) and multicarrier (MC- CDMA) are two important CDMA schemes for high rate wireless communication. Multi-carrier code division multiple access (MCCDMA) has been considered as a strong candidate for next generation wireless communication system due to its excellent performance in multi-path fading channel and simple receiver structure. However, like all the multi-carrier transmission technologies such as OFDM, the inter-carrier interference (ICI) produced by the frequency offset between the transmitter and receiver local oscillators or by Doppler shift due to high mobility causes significant BER (bit error rate) performance degradation in MC-CDMA system. Many ICI cancellation methods such as windowing and frequency domain coding have been proposed in the literature to cancel ICI and improve the BER performance for multi-carrier transmission technologies. In this paper, my main objective is to evaluate the Inter channel Interference which include the Signal to Interference Ratio (SIR) and Inter Carrier Interference (ICI) in a MC DS CDMA wireless system.

Keywords

DSCDMA, MC-CDMA, ICI,OFDM, BER.

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