With the exploding grow up of mobile users and the release of new wireless applications, radio resource management is principally considered. The Quality of Service (QoS) requirements for the high bandwidth applications such as video conferencing, Voice over IP (VoIP), audio and video streaming and File Transfer Protocol (FTP) have been taking as a major interest for the design of the wireless systems. IEEE 802.16 standard based (WiMAX) is considered one of the important Broadband Wireless Access (BWA) technologies that can satisfy the requirements of heterogeneous traffic. It can be great solution for providing internet access instead of traditional wired broadband networks such as DSL and T1 services. WiMAX systems can be able to provide high peak data rates, mobility service, and high spectral efficiency. So it has encouraged several researchers from both commerce and academia as a result of its high data rate. In this paper the problem of dissipated part of allocated bandwidth in WiMAX network has been taking as a major concern for the design and development of the modified version of scheduling scheme. The purpose of this paper is to evaluate the performance of the jitter in the WiMAX network in Point to Multipoint (PMP) mode. Through using a modified version of MAC construction, simulation results indicate that the proposed scheme can decrease from ten to twenty percent of the average jitter as well as maximizing throughput and minimizing system delay.