A Detailed Study of Channel Estimation and BER Optimization in presence of AWGN and Rayleigh Channel of OFDM System

Orthogonal Frequency Division Multiplexing is an important one field communication and that uses parallel information series. Contrast and single carrier adjustment are basic aspects of this technique where OFDM has many favourable circumstances are risky to work on this technique. It is robust, easy to use, and strength to safe the processing channel from distortions. It provides safety from multipath, much lesser computational many-sided characteristic. OFDM has some significant to execute it in commonly using media transmission frameworks. OFDM standard tolerate Packet misfortune, Bit trouble, Bit Error Rate (BER), Signal to Noise Ratio (SNR), Calculation of PAPR, Power Spectrum estimation. This dissertation is targeted to show the comparison of AWGN and Rayleigh channel by using fading process for particularity in superior performance with individual values of spectrums as well as by their scattering plots. In this dissertation each and every signal of these terms are examined and all the four parameters are thought about utilizing AWGN and Rayleigh fading channel by changing the period of a portion of the subcarriers utilizing QPSK in OFDM regulation. The representation of outputs is finished through MATLAB programming

A CME based channel estimation approach for MIMO-OFDM systems

A pilot-assisted, conditional model-order estimation (CME) based channel estimation algorithm is presented. The algorithm is proposed for MIMO-OFDM systems and can detect both channel frequency responses and number of multi-path taps. In addition, the modified CME estimator is also verified its capacity in determining the nonzero taps. The performance of the proposed approach is compared to the popular minimum description length (MDL) algorithm for estimation of the number of channel paths, by means of simulation in the context of a 2x2 MIMO-OFDM transceiver system. Result indicates that the new algorithm is superior in channel order estimation to the MDL algorithm in MMO-OFDM system over a noisy frequency selective fading channel. ©2009 IEEE

SÉQUENCE D’APPRENTISSAGE OPTIMALE POUR L’ESTIMATION DU CANAL MIMO-OFDM

Le canal de propagation MIMO OFDM est généralement estimé en utilisant une séquence d'apprentissage connue au niveau du récepteur. L’augmentation du nombre des sous porteuses pilotes par bloc OFDM engendre une amélioration de la qualité d'estimation du canal mais aussi une perte en termes de débit utile. De même, la diminution du nombre des sous porteuses pilotes augmente le débit utile mais dégrade la qualité d'estimation du canal. Une question qui se pose concerne le choix de l’espacement optimal des sous porteuses pilotes pour avoir une bonne estimation du canal sans diminuer significativement le débit utile de transmission. Dans cet article nous avons proposé un algorithme de recherche de l’emplacement optimal des pilotes

Performance Analysis and Enhancement of Multiband OFDM for UWB Communications

In this paper, we analyze the frequency-hopping orthogonal frequency-division multiplexing (OFDM) system known as Multiband OFDM for high-rate wireless personal area networks (WPANs) based on ultra-wideband (UWB) transmission. Besides considering the standard, we also propose and study system performance enhancements through the application of Turbo and Repeat-Accumulate (RA) codes, as well as OFDM bit-loading. Our methodology consists of (a) a study of the channel model developed under IEEE 802.15 for UWB from a frequency-domain perspective suited for OFDM transmission, (b) development and quantification of appropriate information-theoretic performance measures, (c) comparison of these measures with simulation results for the Multiband OFDM standard proposal as well as our proposed extensions, and (d) the consideration of the influence of practical, imperfect channel estimation on the performance. We find that the current Multiband OFDM standard sufficiently exploits the frequency selectivity of the UWB channel, and that the system performs in the vicinity of the channel cutoff rate. Turbo codes and a reduced-complexity clustered bit-loading algorithm improve the system power efficiency by over 6 dB at a data rate of 480 Mbps.Comment: 32 pages, 10 figures, 1 table. Submitted to the IEEE Transactions on Wireless Communications (Sep. 28, 2005). Minor revisions based on reviewers' comments (June 23, 2006