The mobile WiMAX system is based on the IEEE 802.16m standard which is used to develop an advanced air interface (AAI) to meet the requirements for IMT-Advanced next generation networks , which are able to provide high speed access and are used to provide a rate of broadband data for low mobility scenarios up to 1 Gbit/sec. This paper investigates the application of link adaptation techniques (AM and AMC) to the downlink for the IEEE 802.16m-depending on the mobile WiMAX networks to achieve spectral efficiency gain. Also, by use of link adaptation it is possible to combine the MIMO technique with link adaptation in order to maximize the throughput. This paper considers six various MCS for link adaptation in order to find the largest throughput improvement. The working thresholds of the SNR for the various combinations of modulation, coding and MIMO will be determined through utilizing the ITU pedestrian channel model. Therefore, through employing a system level simulation, the performance evaluation results explain that the adaptive modulation and coding (AMC) system is noticeably superior compared to the systems that utilize fixed modulation (FM) or adaptive modulation (AM) schemes with regard to the spectral efficiency.