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In modern world wireless communication systems are involved in every part of life. WiMAX is the upcoming wireless system which uses IEEE standard 802.16. By using WiMAX technology we can overcome the limitations of the existing wireless communication like short coverage area, lack of security and low data rate. WiMAX is an eminent technology that provides broadband and IP connectivity on “last mile” scenario. It offers both line of sight and non-line of sight wireless communication. Orthogonal Frequency division multiple access is used by WiMAX on its physical layer. Orthogonal frequency division multiple accesses use adaptive modulation technique such as (BPSK, QPSK, 16-QAM, 64-QAM) on the physical layer of WiMAX and it uses the concept of cyclic prefix that adds additional bits at the transmitter end. The signal is transmitted through the channel and it is received at the receiver end. Then the receiver removes these additional bits in order to minimize the inter symbol interference, to improve the bit error rate and to reduce the power spectrum.