ISSN : 1796-2021
Volume : 1    Issue : 6    Date : September 2006

Automatic Detection of the Guard Interval Length in OFDM System
Li Zou
Page(s): 28-32
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Orthogonal Frequency Division Multiplexing (OFDM) has been increasingly used in wireless
broadband communication systems. Guard interval (GI) is used in OFDM system to reduce
inter-symbol interference (ISI). As selection of the length of guard interval depends on the channel
condition, the length of guard interval will change dynamically. Thus there must be a way to
synchronize this parameter between the transmitter and the receivers. Traditional OFDM systems
require a transmitter to notify its receivers using additional signal and thus result additional
bandwidth. In addition, this complicates the initiation process for an OFDM receiver as it has to
search through all the possible values of GI length to find the parameter used by the transmitter. To
address this problem, this paper gives a low-complexity method, which can detect the length of
guard interval at the receiver without any guard interval length information from the transmitter. The
introduction of this method will reduce the additional signaling and simplifies OFDM systems. Both
theoretical analysis and simulation results show that the proposed method has good performance.
The proposed method can give accurate measure of GI length under both AWGN and Rayleigh
Channel even when SNR is as low as 3dB.

Index Terms
OFDM, Guard Interval