Evaluating the Impact of Various Modulation Schemes on WiMAX Quality of Service

Abstract

In order to effectively analyze the QoS performance of WiMAX (Worldwide Interoperability of Microwave Access), it is important to identify different types of modulation techniques that can lead to an increase in performance. Low throughput, high packet loss rate, delayed round trip time (RTT) for packets, increased retransmissions, and increased collisions are the main attributes to look for when analyzing poor network performance. The IEEE 802.16 technology (WiMAX) is a promising technology for prosviding last-mile connectivity by radio link due to its large coverage area, low cost of deployment and high speed data rates. The mobile WiMAX technology was drafted by the International Technological University (ITU) in late 2007. Officially, the IEEE 802.16e revisions promote standards for broadband wireless access systems and currently focus on performance through the PHY and MAC layers of the OSI model. However, the maximum number of channels defined in the current system may cause a potential bottleneck and limit the overall system capacity. We use the OPNET Modeler to simulate IEEE 802.16e WiMAX performance on a network with 35 mobile nodes and seven base stations. We construct a WiMAX deployment with scheduling type ertPS (extended real-time polling service) and different types of digital modulation and coding for both downlink (DL) and Uplink (UL) service flows. We made an assessment of the network performance based on WiMAX throughput and load in bits per second against different modulation schemes. WiMAX delay results are plotted over time (seconds). WiMAX network performance shows no signs of queuing with ertPS and QPSK½. The use of improper implementation of digital modulation and coding causes noticeable queuing to occur. WiMAX delay is significantly affected when forward error-correcting methods are enabled.