  The WIMAX technology based on air interface standard 802.16 wireless MAN is
configured in the same way as a traditional cellular network with base stations
using point to multipoint architecture to drive a service over a radius up to
several kilometers. The range and the Non Line of Sight (NLOS) ability of WIMAX
make the system very attractive for users, but there will be slightly higher
BER at low SNR. The aim of this paper is the comparative study of different
guard time intervals effect for improving BER at different SNR under digital
modulation (QPSK, 16QAM and 64QAM) techniques and different communication
channels AWGN and fading channels Stanford University Interim (SUI 1) of an
WIMAX system. The comparison between these effects with Reed-Solomon (RS)
encoder with Convolutional encoder (half) rated codes in FEC channel coding
will be investigated. The simulation results of estimated Bit Error Rate (BER)
displays that the implementation of interleaved RS code (255,239,8) with (half)
rated Convolutional code of 0.25 guard time intervals under QPSK modulation
technique over AWGN channel is highly effective to combat in the Wimax
communication system. To complete this performance analysis in Wimax based
systems, a segment of audio signal is used for analysis. The transmitted audio
message is found to have retrieved effectively under noisy situation.
