In this paper, a novel noise power and SNR estimator based on one OFDM preamble is proposed. The estimator, unlike others, performs noise power estimation at the front-end of the receiver. The proposed estimator is compared with previously published SNR estimators - none of which are front end estimator. The estimator makes use of two identical halves property of time synchronization preamble used in WiMAX systems IEEE802.16, 2004 and relies on autocorrelation of the same. SUIChannels are used for simulations in this work. The current estimator is compare with Reddy estimator and Subspace based estimator in terms of normalized mean square error (NMSE) and estimated SNR .It is observed that current estimator gives SNR estimates better than Reddy and subspace estimators. Complexity of the system is decreased because current estimator makes use of one OFDM preamble. © 2008 IEEE.