WiMax, like DSL/cable is standards based and enables vendors to interoperate with one another. The IEEE standard 802.16 was specified for Worldwide Interoperability for Microwave Access (WiMax). This standard has been further revised for 2-11GHz fixed (802.16.a-2004) and 2-6GHz portable (802.16e) wireless solutions.
The WiMax Forum has been chartered with taking the standards (IEEE/ETSI) and implementing interoperable solutions for WiMax. The forum is comprised of a group of diverse companies, ranging from silicon vendors to equipment manufacturers to wireless carriers, all having a stake in the deployment of WiMax. The WiMax Forum conducts a number of interoperability events, to bring vendors on common ground. There will also be a WiMax certification for interoperability with multiple vendors, similar to the TR-067 Interoperability tests for DSL or WiFi certification.
Typical WiMax equipment would contain a baseband-PHY processor and the MAC network processor besides memory and other peripherals. WiMax uses Orthogonal Frequency Division Multiplexing (OFDM) for modulation in its physical layer, which bundles data over narrowband carriers transmitted in parallel at different frequencies. The same technique has been used as Discrete Multi-tone Modulation (DMT) in ADSL. OFDM makes WiMax scalable for a fluctuating user base, since the spectrum can be dynamically reallocated (range: 1.25-20 MHz) with variations in the number of subscribers. In addition, OFDM improves resilience to interference and outdoor environment, and improves the signal to noise ratio at the terminals.
There are a number of challenges facing WiMax including: