WiMAX


Worldwide Interoperability for Microwave Access is a family of wireless broadband communication standards based on the IEEE 802.16 set of standards, which provide physical layer and media access control options.
The WiMAX Forum was formed in June 2001 to promote conformity and interoperability, including the definition of system profiles for commercial vendors. The forum describes WiMAX as "a standards-based technology enabling the delivery of last mile wireless broadband access as an alternative to cable and DSL".
WiMAX was initially designed to provide 30 to 40 megabit-per-second data rates, with the 2011 update providing up to 1 Gbit/s for fixed stations. IEEE 802.16m or Wireless MAN-Advanced was a candidate for 4G, in competition with the LTE Advanced standard. WiMAX release 2.1, popularly branded as WiMAX 2+, is a backwards-compatible transition from previous WiMAX generations. It is compatible and interoperable with TD-LTE. Newer versions, still backward compatible, include WiMAX release 2.2 and WiMAX release 3.

Terminology

WiMAX refers to interoperable implementations of the IEEE 802.16 family of wireless-networks standards ratified by the WiMAX Forum. WiMAX Forum certification allows vendors to sell fixed or mobile products as WiMAX certified, thus ensuring a level of interoperability with other certified products, as long as they fit the same profile.
The original IEEE 802.16 standard was published in 2001.
WiMAX adopted some of its technology from WiBro, a service marketed in Korea.
Mobile WiMAX is the revision that was deployed in many countries and is the basis for future revisions such as 802.16m-2011.
WiMAX was sometimes referred to as "Wi-Fi on steroids" and can be used for a number of applications including broadband connections, cellular backhaul, hotspots, etc. It is similar to Long-range Wi-Fi, but it can enable usage at much greater distances.

Uses of WiMAX

The scalable physical layer architecture that allows for data rate to scale easily with available channel bandwidth and range of WiMAX make it suitable for the following potential applications:
WiMAX can provide at-home or mobile Internet access across whole cities or countries. In many cases, this has resulted in competition in markets which typically only had access through an existing incumbent DSL operator.
Additionally, given the relatively low costs associated with the deployment of a WiMAX network, it is now economically viable to provide last-mile broadband Internet access in remote locations.

Middle-mile backhaul to fiber networks

Mobile WiMAX was a replacement candidate for cellular phone technologies such as GSM and CDMA, or can be used as an overlay to increase capacity. Fixed WiMAX is also considered as a wireless backhaul technology for 2G, 3G, and 4G networks in both developed and developing nations.
In North America, backhaul for urban operations is typically provided via one or more copper wire line connections, whereas remote cellular operations are sometimes backhauled via satellite. In other regions, urban and rural backhaul is usually provided by microwave links. WiMAX has more substantial backhaul bandwidth requirements than legacy cellular applications. Consequently, the use of wireless microwave backhaul is on the rise in North America and existing microwave backhaul links in all regions are being upgraded. Capacities of between 34 Mbit/s and 1 Gbit/s are routinely being deployed with latencies in the order of 1 ms.
In many cases, operators are aggregating sites using wireless technology and then presenting traffic on to fiber networks where convenient. WiMAX in this application competes with microwave radio, E-line and simple extension of the fiber network itself.

Triple-play

WiMAX directly supports the technologies that make triple-play service offerings possible. These are inherent to the WiMAX standard rather than being added on as carrier Ethernet is to Ethernet.
On May 7, 2008, in the United States, Sprint Nextel, Google, Intel, Comcast, Bright House, and Time Warner announced a pooling of an average of 120 MHz of spectrum and merged with Clearwire to market the service. The new company hoped to benefit from combined services offerings and network resources as a springboard past its competitors. The cable companies were expected to provide media services to other partners while gaining access to the wireless network as a Mobile virtual network operator to provide triple-play services.
Some wireless industry analysts, such as Ken Dulaney and Todd Kort at Gartner, were skeptical how the deal would work out: Although fixed-mobile convergence had been a recognized factor in the industry, prior attempts to form partnerships among wireless and cable companies had generally failed to lead to significant benefits for the participants. Other analysts at IDC favored the deal, pointing out that as wireless progresses to higher bandwidth, it inevitably competes more directly with cable, DSL and fiber, inspiring competitors into collaboration. Also, as wireless broadband networks grow denser and usage habits shift, the need for increased backhaul and media services accelerate, therefore the opportunity to leverage high bandwidth assets was expected to increase.

Aviation

The Aeronautical Mobile Airport Communication System is a wireless broadband network for the airport surface intended to link the control tower, aircraft, and fixed assets. In 2007, AeroMACS obtained a worldwide frequency allocation in the 5 GHz aviation band. As of 2018, there were 25 AeroMACS deployments in 8 countries, with at least another 25 deployments planned.

Support for TDD and FDD

IEEE 802.16REVd and IEEE 802.16e standards support both time-division duplexing and frequency-division duplexing as well as a half duplex FDD, that allows for a low cost implementation.

Connecting

Devices that provide connectivity to a WiMAX network are known as subscriber stations.
Portable units include handsets ; PC peripherals ; and embedded devices in laptops, which are now available for Wi-Fi services. In addition, there is much emphasis by operators on consumer electronics devices such as Gaming consoles, MP3 players and similar devices. WiMAX is more similar to Wi-Fi than to other 3G cellular technologies.
The WiMAX Forum website provides a list of certified devices. However, this is not a complete list of devices available as certified modules are embedded into laptops, MIDs, and other private labeled devices.

Gateways

WiMAX gateway devices are available as both indoor and outdoor versions from manufacturers including Vecima Networks, Alvarion, Airspan, ZyXEL, Huawei, and Motorola. The list of WiMAX networks and WiMAX Forum provide more links to specific vendors, products and installations.
Many of the WiMAX gateways that are offered by manufactures such as these are stand-alone self-install indoor units. Such devices typically sit near the customer's window with the best signal, and provide:
  • An integrated Wi-Fi access point to provide the WiMAX Internet connectivity to multiple devices throughout the home or business.
  • Ethernet ports to connect directly to a computer, router, printer or DVR on a local wired network.
  • One or two analog telephone jacks to connect a land-line phone and take advantage of VoIP.
Indoor gateways are convenient, but radio losses mean that the subscriber may need to be significantly closer to the WiMAX base station than with professionally installed external units.
Outdoor units are roughly the size of a laptop PC, and their installation is comparable to the installation of a residential satellite dish. A higher-gain directional outdoor unit will generally result in greatly increased range and throughput but with the obvious loss of practical mobility of the unit.

External modems

can provide connectivity to a WiMAX network through a dongle. Generally, these devices are connected to a notebook or net book computer. Dongles typically have omnidirectional antennas which are of lower gain compared to other devices. As such, these devices are best used in areas of good coverage.

Mobile phones

HTC announced the first WiMAX enabled mobile phone, the Max 4G, on November 12, 2008. The device was only available to certain markets in Russia on the Yota network until 2010.
HTC and Sprint Nextel released the second WiMAX enabled mobile phone, the HTC Evo 4G, March 23, 2010 at the CTIA conference in Las Vegas. The device, made available on June 4, 2010, is capable of both EV-DO and WiMAX as well as simultaneous data & voice sessions. Sprint Nextel announced at CES 2012 that it will no longer be offering devices using the WiMAX technology due to financial circumstances, instead, along with its network partner Clearwire, Sprint Nextel rolled out a 4G network having decided to shift and utilize LTE 4G technology instead.

Technical information

The IEEE 802.16 standard

WiMAX is based upon IEEE 802.16e-2005, approved in December 2005. It is a supplement to the IEEE Std 802.16-2004, and so the actual standard is 802.16-2004 as amended by 802.16e-2005. Thus, these specifications need to be considered together.
IEEE 802.16e-2005 improves upon IEEE 802.16-2004 by:
  • Adding support for mobility. This is seen as one of the most important aspects of 802.16e-2005, and is the basis of mobile WiMAX.
  • Scaling of the fast Fourier transform to the channel bandwidth in order to keep the carrier spacing constant across different channel bandwidths. Constant carrier spacing results in a higher spectrum efficiency in wide channels, and a cost reduction in narrow channels. Also known as scalable OFDMA. Other bands not multiples of 1.25 MHz are defined in the standard, but because the allowed FFT subcarrier numbers are only 128, 512, 1024 and 2048, other frequency bands will not have exactly the same carrier spacing, which might not be optimal for implementations. Carrier spacing is 10.94 kHz.
  • Advanced antenna diversity schemes, and hybrid automatic repeat-request
  • Adaptive antenna systems and MIMO technology
  • Denser sub-channelization, thereby improving indoor penetration
  • Intro and low-density parity check
  • Introducing downlink sub-channelization, allowing administrators to trade coverage for capacity or vice versa
  • Adding an extra quality of service class for VoIP applications
SOFDMA and OFDM256 are not compatible thus equipment will have to be replaced if an operator is to move to the later standard.