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Using Simulation to Design WiMAX Devices and Networks WiMAX is a new standard for “last-mile” wireless technology that can deliver broadband connectivity anywhere, anytime, and for virtually any device. WiMAX equipment manufacturers include both established players (such as Intel, Samsung, Motorola, and NEC) and startups. Network operators are expected to adopt WiMAX rapidly to enable new mobile services such as multimedia streaming, videoconferencing, internet telephony, and location-based services. In order for WiMAX to realize its potential, equipment manufacturers must consider several key factors during product development. This article discusses how modeling and simulation can help developers. Broadband networks carry several types of traffic including data, voice, and video, with varying quality-of-service (QoS) requirements. The WiMAX standard defines five service classes to handle different traffic types, but the equipment manufacturer determines the algorithms that manipulate the traffic to meet specific requirements. The WiMAX device must differentiate traffic types, and ideally still provide the operator with the flexibility to adjust QoS thresholds. This flexibility allows operators to allocate bandwidth dynamically to applications based on user demand. Equipment manufacturers can leverage network simulation to predict the resource consumption of various application types and to optimize their QoS algorithms. Simulation also enables manufacturers to improve admission control algorithms. WiMAX admission control policies ensure that only authorized users access the network, and that no call or session is dropped due to resource constraints. The algorithms must balance operation robustness against the consumption of signaling bandwidth. With network modeling, users can compare algorithms long before actual implementation. Since WiMAX must co-exist with current mobile network technologies, its devices and networks must interoperate with them. A common way to make this happen is by employing multi-mode devices. They can be a real challenge for vendors because legacy networks may operate in different frequency bands, have different power and signaling requirements, and use different modulation schemes. Hybrid networks that incorporate WiMAX and legacy technologies can be simulated in software, with a wide variety of configurations, to identify interoperability issues quickly. A popular way to develop simulations is by using tools such as OPNET Modeler®, a network modeling and simulation tool for designing wired and wireless protocols, devices, and technologies. OPNET Modeler supports the design of network devices and the testing of their behavior in virtual networks of realistic scale and complexity. It allows designs to be verified using simulation in real-world environments, which typically cannot be replicated in a test laboratory. OPNET’s WiMAX technology model was developed with input from over 50 wireless industry leaders, including Motorola, Samsung, NEC, and France Telecom. The model adheres to the guidelines and specifications published by the WiMAX Forum. WiMAX is a new wireless technology that will be a major factor in future communication networks. Simulation tools such as OPNET Modeler allow equipment developers to cut costs and accelerate time-to-market. They can test and compare algorithms, identify problems in networks, and ensure co-existence of WiMAX with legacy technologies. Akshay Seshadrinathan is a Product Marketing Manager at OPNET Technologies in Bethesda, MD. You can reach him at aseshadrinathan@opnet.com. |