The emerging IEEE 802.16 standard, commonly known as Wi-Fi MAX, promises to bring last-mile wireless broadband Internet access capable of carrying data-intensive applications, such as VoIP and streaming video, to metropolitan area networks as well as suburban and rural communities. WiMAX is considered a disruptive technology, designed as an alternative to fixed-line DSL and coaxial technologies, and with its 802.16e revision, cellular networks as well.
Worldwide Interoperability for Microwave AXcess will operate over licensed and unlicensed frequencies using non-line-of-sight (NLOS) and non-line-of-sight technologies, extending broadband coverage to cities and towns wirelessly through a metropolitan area network. Furthermore, due to its long-range capabilities and ease of deployment, wimax is the only technology that is likely to bridge the digital divide, connecting underdeveloped regions and sparsely populated rural areas much more cost-effectively than deploying wired infrastructure.
WiMAX and Wi-Fi compared
The widespread adoption of wireless LAN in the business community, as well as the emergence of Wi-Fi hotspots in public areas, airports, hotels, and cafes, has been of great importance in bringing mobility to both businessmen and consumers. Thanks to open standards guided by the 802.11 committee and the WiFi Alliance, WiFi technology is taking root in our society. WiMAX plans to take WiFi one step further.
While the two technologies may sound the same, from their inception they are designed for totally different applications. WiFi is a short-range standard that was primarily designed as an extension to the local area network (LAN) to provide end-user mobility. It operates on unlicensed frequencies and has a range of about 100 meters, depending on obstructions. Typically, an access point will be connected to a fixed line network, either a wired LAN or a cable/DSL broadband connection, and the range can be extended by adding more access points at appropriate distances.
WiMAX, on the other hand, is designed to function as a transport network, or wireless Internet service provider (WISP), covering entire cities and regions with broadband Internet access comparable to DSL. Coverage under optimal conditions could reach 50 kilometers, but in reality it is more than 5 km for users with NLOS customer premises equipment (CPE), or up to 15 km with a CPE connected to an external line-of-sight antenna.
As the older and more established technology, 802.11 WiFi has been used in a mesh topology to cover larger areas, such as university campuses and town halls, for example, to connect police vehicle terminals to their database. The emerging 802.16 WiMAX will be more suitable for larger deployments and will actually complement private Wi-Fi networks by offering cheaper and more secure Internet access for voice and data applications.
The WiMAX standards: fixed, nomadic and mobile
The 802.16 standard developed by the IEEE envisions a fixed wireless broadband network operating in the spectrum range of 10 GHz to 66 GHz. Originally, only licensed spectrum was addressed in this range, and line-of-sight multipath technology was tried by adopting OFDM as standard. Later revisions added the 2 GHz to 11 GHz band to the spectrum and added support for non-line-of-sight technologies and quality of service (QoS) techniques, a prerequisite for time-sensitive applications such as voice and video.
The revision known as 802.16-2004(d) brought together all the previous revisions and then added some. Most of these original issues dealt with the media and physical access control layers, and resulted in a standard list of optional and mandatory elements by which vendors could design their products.
The resulting fixed WiMAX standard has a data rate of up to 40 Mbps, support for half and full duplex transmission, improved QoS, and the incorporation of multiple polling techniques, ultimately reducing packet collisions and overhead.
Base stations must support several different topologies, such as wired backhauling, microwave point-to-point connections, and the ability of the WiMAX base station to backhaul itself by reserving a portion of the bandwidth for that purpose.
By design, 802.16d would serve the residential and small business markets by offering broadband wireless access with speeds comparable to DSL. Enterprise markets could be served at T1/E1 data speeds.
While this version of WiMax is called fixed, it’s nomadic in all the news. Users of a private indoor WiFi network could seamlessly switch to the public WiFi network when moving outdoors, and their hardware will determine the best available network. Devices on the WiMAX data network would include laptops, PDAs, and smartphones equipped with an embedded WiMAX-compatible PC card or chip, which use the spectrum for voice, data, video, and music transfers.
Nomadic WiMAX provides limited mobility in the sense that the coverage range is handled by the same base station.
WiMAX goes mobile
With the adoption of the 802.16e revision in late 2005, all the excitement has focused on Mobile WiMAX, a technology designed to compete with cellular networks.
With significant support from manufacturers such as Intel, Motorola, Siemens and Nokia, among others, mobile WiMAX is based on open standards and is supposed to be 4 times faster than 3G cellular technologies (EVDO, HSDPA). Significant cost savings can be achieved for voice applications by making calls over the Internet using VoIP.
802.16e provides fast and seamless handovers between base stations, with a cell radius of approximately 3 miles, similar to cellular networks. The standard was ratified in late 2005 and real-world applications began to appear in 2007, with more robust development expected throughout 2008.
Because this technology is such a big threat to the legacy telecommunications industry, it’s no surprise that Sprint Nextel is going to implement WiMAX instead of EVDO on its 4G network. Sprint has been buying up much of the WiMAX spectrum and recently announced a partnership with Nokia to roll out WiMAX to four Texas cities in mid-2008. This isn’t its first WiMAX network, and telcos around the world have been doing the same thing. .
The 802.16 standards are a work in progress and as such are subject to change and revision. As the standards work their way into the technology, the WiMAX Forum committee hopes to do what the WiFi Alliance did for the 802.11 standards, promoting interoperability between components through testing and offering WiMAX certification to providers that meet the standards. 802.16.
It should be noted that many of the WiMAX implementations at the time of this writing are proprietary and therefore do not necessarily follow the recommendations of the IEEE or WiMAX Forum. Wireless broadband ISP Clearwire Communications has more than 200,000 subscribers in 375 cities and calls its service a “WiMAX-class solution, using state-of-the-art non-line-of-sight wireless technology.” Other early adopters of pre-WiMAX technology are moving forward, providing wireless broadband access to the residential consumer and small business market, with many businesses jumping on board with evolving standards to ensure interoperability and consistency. compatibility with previous versions of devices and applications.