Performance comparison of several channel estimation techniques in the downlink of LTE systems was performed based upon the algorithm’s complexity which varies according to the density of the channel matrix. In this study has been presented a proposed channel estimation technique whose complexity is invariant with the number of multipath components in fast fading channels. The proposed channel estimator is derived by a review of the mathematical model of the received OFDM signal in the down link of LTE systems its performance is evaluated using the mean squared error as the performance metric of interest. Also a study of the effect of the proposed channel estimation technique on the bit error rate performance of the downlink of LTE systems is also investigated numerically through simulation

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An Analytical technique is developed to evaluate the error rate performances of quadrature phase shift keying (QPSK) and 16-ary phase shift keying (16-ary PSK) in a land mobile satellite communication channel. A regenerative repeater is considered. The effects of satellite nonlinearity and mobile channel on the performances of both systems have been considered. A frequency non-selective fading has been assumed. The combined effect of the traveling wave tube (TWT) power amplifier which exhibits AMfAM and AMfPM cnwersions and the multipath fading and shadowing of the mobile channel in addition to lhe additive white Gaussian noise (AWGN) are taken into consideration in the analysis. The effect of TWT back-off from saturation which determines the degree of nonlinearity has also been taken into account. An expression for the error probabilities for both systems are derived and computed numerically.

Convolutional Encoder Convolutional r a Decoder V A A C , b Block Interleaver Block Deinterleaver ■■•■■••■•■1101 eft) Pulse Shaping Filter Matched Filter Channel Estimatorh r(r) v' ABSTRACTThis paper analyzes the performance of an interleaved convolutional coded BPSK with perfect channel state information and coherent detection, assuming perfect synchronization. Analytical results for the pairwise error event probability using the characteristic function technique is derived. An approximate bit error probability is obtained by summing the probabilities of the dominant error events.