The emerging IEEE 802.16 standard, commonly known as WiMAX, promises to provide last-mile wireless broadband Internet access capable of transporting data-intensive applications, such as VoIP and video streaming, 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 phone networks too.

Worldwide Interoperability for Microwaves AXcess will operate on licensed and unlicensed frequencies using non-line-of-sight (NLOS) and line-of-sight technologies, extending broadband coverage to cities and towns wirelessly over a metropolitan area network. Furthermore, due to its far-reaching capabilities and ease of deployment, wimax is the only technology close to bridging the digital divide, connecting underdeveloped regions and sparsely populated rural areas much more cost-effectively than deploying a wired infrastructure.

WiMAX and WiFi comparison

The widespread adoption of wireless LAN in the business community, as well as the appearance of WiFi access points in public areas, airports, hotels and cafes, has been of great importance in providing mobility to both business people 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 appear the same, from their conception they are designed for totally different applications. WiFi is a short-range standard that was primarily designed as an extension of the local area network (LAN) to provide mobility to the end user. It operates on unlicensed frequencies and has a range of about 100 meters, depending on obstructions. Typically, an access point will connect to a fixed line network, be it a wired LAN or a cable / DSL broadband connection, and the range can be expanded by adding more access points at the appropriate distances.

WiMAX, on the other hand, is designed to function as a carrier network, or a wireless Internet service provider (WISP), covering entire cities and regions with broadband Internet access comparable to DSL. Coverage in optimal conditions could go up to 50 kilometers, but is actually more like 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 oldest and most established technology, 802.11 WiFi has been used in a mesh topology to cover larger areas such as university campuses and municipalities, for example, to connect terminals in police vehicles to its database. The emerging 802.16 WiMAX will be better suited for larger deployments and will indeed complement private WiFi networks by offering cheaper and more secure Internet access for voice and data applications.

WiMAX standards: fixed, nomadic and mobile

The 802.16 standard developed by the IEEE provides for a fixed wireless broadband network operating in the spectrum range from 10 GHz to 66 GHz. Originally, only licensed spectrum in this range was addressed, and line-of-sight multipath technology it was addressed by adopting OFDM as the standard. Subsequent revisions added the 2 GHz to 11 GHz band to the spectrum and incorporated 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 patch known as 802.16-2004 (d) rolled up all the previous patches and then added a few. Most of these original issues concerned the physical and media access control layers, and resulted in a standard list of mandatory and optional items 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 cable backhauling, microwave point-to-point connections, and the ability of the WiMAX base station to fall back on itself by reserving a portion of the bandwidth for that purpose.

By design, 802.16d would suit residential and small business markets that offer broadband wireless access with speeds comparable to DSL. Enterprise markets could be served at T1 / E1 data rates.

While this version of WiMax is called fixed, it is actually nomadic. Users of a private indoor WiFi network can seamlessly transition to the public WiMAX network when moving outdoors, and their hardware determines the best available network. Devices on the WiMAX data network would include laptops, PDAs and smartphones equipped with an onboard WiMAX-capable PC chip or card, which use 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 802.16ea revision in late 2005, all the hype has been on Mobile WiMAX, a technology designed to compete with cellular networks.

With the greatest 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 when making calls over the Internet via VoIP.

802.16e provides fast and smooth transfers 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 are starting to appear in 2007, with more robust development expected throughout 2008.

Because this technology is a threat to the legacy telecommunications industry, it is no wonder that Sprint Nextel is implementing WiMAX instead of EVDO on its 4G network. Sprint has been purchasing much of the WiMAX spectrum and recently announced a partnership with Nokia to roll out WiMAX in four Texas cities in mid-2008. This is not its first WiMAX network, and telecommunications companies around the world have been doing the same. .

The 802.16 standards are a work in progress and as such are subject to change and revision. As the standards committee works on the technology, the WiMAX Forum hopes to do what the WiFi Alliance did for 802.11 standards, promoting interoperability between components through testing and offering WiMAX certification to vendors that comply with 802.16 standards.

It should be noted that many of the WiMAX implementations at the time of writing are proprietary and therefore do not necessarily follow the IEEE or WiMAX Forum recommendations. Wireless broadband ISP Clearwire Communications has more than 200,000 subscribers in 375 cities and calls its service a “WiMAX-class solution, utilizing next-generation wireless technology without line of sight.” Other early adopters of pre-WiMAX technology are moving forward, providing wireless broadband access to residential consumers and the small business market, and many businesses are jumping on the bandwagon of evolving standards to ensure interoperability and compatibility with previous versions of devices and applications.