Apr 18, 2009

The World of WiMAX

You might start asking, "What is WiMAX anyway and what can I get from it?" Well, if you're the type of person that travels a lot to remote areas and is always in a dire need of Hi-speed Internet access, then WiMAX is for you. WiMAX stands for Worldwide Interoperability for Microwave Access. It is also known as IEEE 802.16 and by the term WirelessMAN (Wireless Metropolitan Area Network).

A group known as the WiMAX Forum was formed in April 2001 to oversee and promote the interoperability and conformance of the said standard. The WiMAX Forum is the only organization exclusively devoted to certify the Broadband Wireless Access products and makes sure that different vendor systems work effortlessly with one another. All those who pass the interoperability and conformance test acquire the "WiMAX Forum Certified" mark on their products and are allowed to put the mark on their marketing materials. The Forum also warned that some manufacturers stating that their product is "WiMAX-ready" or "WiMAX-compliant" are not "WiMAX Forum Certified".

In principle, WiMAX is very different to Wi-Fi. The media access controller of Wi-Fi is using contention access where all subscriber stations that intend to pass data to the access point are competing for the access point's attention on an arbitrary basis. This significantly reduces the throughput of the nodes as their distance to the access point increases since closer nodes tend to repeatedly interrupt their transmission. This makes VOIP and IPTV service very difficult to implement and maintain using Wi-Fi especially when there are a significant number of users involved. The WiMAX media access controller uses a different approach. A WiMAX subscriber station needs only to compete once and this only happens during the initial entry to the network. The base station then assigns a time slot and other subscriber stations are not allowed to transmit during that time slot and wait for their turn. The time slot can enlarge or constrict; yet it still remains assigned to the subscriber station. The scheduling algorithm used by the WiMAX base station can handle overload with ease and remains stable. This makes WiMAX very efficient.

The original WiMAX standard uses the 10 to 66 GHz range and in 2004, added the 2 to 11 GHz range. Most parts of the additional frequency range are already unlicensed internationally although a few still need domestic licenses. WiMAX also uses a relatively stronger encryption algorithm since this was a major concern after the initial Wi-Fi implementation. WiMAX also aims to come up of a solution for nodes without any direct line of sight. The 5-6 Ghz spectrum is considered to be the most reasonable range that can provide the optimum performance and cost effectiveness for point to multi point deployments. The details on the implementations and performance of WiMAX in non-line of sight situations are still unclear since it is still in the experimental stage. Recent development of WiMAX includes full mesh networking capability where a WiMAX node acts as a base station and a subscriber station at the same time.

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