Performance Analysis and Enhancement of Adaptive modulation in WiMAX System/ IEEE 802.16 physical layer

Abstract

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. Orthogonal frequency division multiple accesses use adaptive modulation technique such as Quadrature Phase Shift Keying (QPSK), Quadrature amplitude Modulation (QAM). 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. This analysis is useful for performance evaluation of different Modulation technique used in WIMAX. Cyclic prefix is used to reduce the data errors caused by multipath reception. Here we estimate the channel to know the condition for adaptation in data rate. Channel estimation is used because amplitude and phase shift causes error in wireless channel. Then using Adaptive equalizer bit error rate for all modulation techniques are improved. Here we used with and without decision feedback equalizer to change the bit error rate. Least mean square algorithm is used for implementation of equalizer. LMS algorithm is used with decision feedback and without decision feedback. Here we used adaptive modulation technique analyzing the channel condition by investigating the received data. We just change the modulation technique by analyzing the received bits and accordingly changing the modulation technique as the code bits sent through feedback channel.