Worldwide Interoperability for Microwave Access (WiMAX) is a wireless communication system that allows computers and workstations to connect to high-speed data networks (such as the Internet) using radio waves as the transmission medium with data transmission rates that can exceed 120 Mbps for each radio channel. The WiMAX system is defined in a group of IEEE 802.16 industry standards and its various revisions are used for particular forms of fixed and mobile broadband wireless access.
WiMAX is primarily used as a wireless metropolitan area network (WMAN). Derived from wireless metropolitan area networks (WMAN), WiMAX can provide broadband data communication access services ranging from urban to rural settings.
Used throughout the world, WiMAX broadband competes with DSO, cable modem and optical broadband connections by offering applications which include consumer broadband wireless Internet services, interconnecting lines (leased lines), and transport of digital television (IPTV) services.
Figure 1 depicts a number of the applications compatible/suitable for the wireless WiMAX systems including broadband Internet access, telephone access services, television service access and mobile telephone services.
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The 802.16 system was initially designed for fixed location nomadic service in order to provide communication services to more than one location. While nomadic service may be provided to many locations, it typically requires the transportable communication device to be in a fixed location during the usage of communication services.
Developed for mobile service, the 802.16e specification adds mobility management, extensible authentication protocol (EAP), handoff (call transfer), and power saving sleep modes.
WiMAX has several different physical radio transmission options which allows it to be deployed in areas with different regulatory and frequency availability requirements. Moreover, the system was designed with the ability to be used in licensed or unlicensed frequency bands using narrow or wide frequency channels.
Figure 2 illustrates a variety of uses that WiMAX networks can provide including point-to-point links, residential broadband and high-speed business connections. As shown, the point to point (PTP) connection may be independent from all other systems or networks. The point to multipoint (PMP) system allows a radio system to provide services to multiple users. WiMAX systems can also be established as mesh networks allowing the WiMAX system to forward packets between base stations and subscribers without having to install communication lines between base stations.
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WiMAX systems are composed of subscriber stations, base stations, interconnecting switches, and databases. Subscriber stations receive and convert radio signals into user information, while base stations are the radio part of a radio transmission site (cell site). Base stations convert signals from subscriber stations into a form that can be transferred into the wireless network. Interconnecting switches and transmission lines transfer signals between base stations and other systems (such as the public telephone network or the Internet). Databases are collections of data that is interrelated and stored in memory (disk, computer, or other data storage medium). WiMAX systems typically contain several databases that hold subscriber information, equipment configuration, feature lists and security codes.
Figure 3 illustrates the key components of a WiMAX radio system. The major components of a WiMAX system include; a subscriber station (SS), a base station (BS) and interconnection gateways to datacom (e.g. Internet), telecom (e.g. PSTN) and television (e.g. IPTV). An antenna and receiver ( subscriber station) in the home or business converts the high frequency (microwave) radio signals into broadband data signals for distribution. In Figure 2 WiMAX system is being used to provide television and broadband data communication services. When used for television services, the WiMAX system converts broadcast signals to a data format (such as IPTV) for distribution to IP set top boxes. When WiMAX is used for broadband data, the WiMAX system also connects the Internet through a gateway to the Internet. This example also shows that the WiMAX system can reach distances of up to 50 km for fixed point to point operation.
To develop a cost effective, high-speed data transmission WMAN system, the IEEE created the 802.16 industry specification. The original 802.16 systems were a line of sight system that operates in the 10 GHz to 66 GHz of radio spectrum. To allow the 802.16 systems to operate in the 2 GHz to 11 GHz bands, the 802.16A specification was created.
The radio channel bandwidth of a WiMAX system can be very wide (e.g. greater than 20 MHz) and the radio access technology uses dynamically assigned burst transmission. This allows WiMAX systems to provide data transmission rates that can exceed 120 Mbps .
To help ensure WiMAX products perform correctly and are interoperable with each other, the WiMAX Forum was created. The WiMAX Forum is a non-profit organization that certifies products conform to the industry specification and interoperate with each other. WiMAX™ is a registered trademark of the WiMAX Alliance and the indication that the product is WiMAX Certified™ indicates products have been tested and should be interoperable with other products regardless of who manufactured the product.
Because the fundamental technology used in the 802.16 system is similar to 802.11 (wireless LAN), which is similar to 802.3 (Ethernet), wired or wireless LANs systems can be connected to a WiMAX system as an extension. In some cases, the WiMAX system can be operated independently to provide direct data connections between all the computers that can connect to the WiMAX system.
