A Frequency and Timing Period Acquisition Technique for OFDM Systems

Hiroshi NOGAMI  Toshiro NAGASHIMA  

IEICE TRANSACTIONS on Communications   Vol.E79-B   No.8   pp.1135-1146
Publication Date: 1996/08/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Radio Communication
orthogonal frequency division multiplexing (OFDM),  frequency offset,  timing period offset,  acquisition technique,  pilot symbol,  PN sequence,  multipath fading,  

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Orthogonal frequency division multiplexing (OFDM) has been receiving a lot of attention in the field of broadcasting because of its ruggedness under multipath environments. One of important issues to realize high quality reception of OFDM signals is to correct frequency and timing offsets between the transmitter and receiver so that orthogonality of the carriers can be maintained. This paper discusses a frequency and timing period acquisition technique for OFDM systems. A new offset estimation technique is introduced that detects both the frequency and timing peirod offsets at the same time by using only one pilot symbol with its suitable frequency assignment. A pseudo noise (PN) sequence is also introduced to assign these frequencies of the pilot symbol so that the frequency acquisition range can be widened. Numerical examples are given to show the estimate variances of the proposed frequency and timing period estimator over both additive white Gaussian noise (AWGN) and multipath fading channels. Also the bit error rate (BER) performance for an open loop acquisition system is examined.