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WiMAX

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WiMAX logo
WiMAX logo

WiMAX is an acronym that stands for Worldwide Interoperability for Microwave Access, a certification mark for products that pass conformity and interoperability tests for the IEEE 802.16 standards.

Products that pass the conformity tests for WiMAX are capable of forming wireless connections between them to permit the carrying of internet packet data. It is similar to WiFi in concept, but has certain improvements that are aimed at improving performance and should permit usage over much greater distances.

IEEE 802.16 is working group number 16 of IEEE 802, specializing in point-to-multipoint broadband wireless access.

Technical advantages over WiFi

Because IEEE 802.16 networks use the same LLC layer (standardized by IEEE 802.2) as other LANs and WANs, it can be both bridged and routed to them.

An important aspect of the IEEE 802.16 is that it defines a MAC layer that supports multiple physical layer (PHY) specifications. This is crucial to allow equipment makers to differentiate their offerings. This is also an important aspect of why WiMAX can be described as a "framework for the evolution of wireless broadband" rather than a static implementation of wireless technologies. Enhancements to current and new technologies and potentially new basic technologies incorporated into the PHY (physical layer) can be used. A converging trend is the use of multi-mode and multi-radio SoCs and system designs that are harmonized through the use of common MAC, system management, roaming, IMS and other levels of the system. WiMAX may be described as a bold attempt at forging many technologies to serve many needs across many spectrums.

The MAC is significantly different from that of Wi-Fi (and ethernet from which Wi-Fi is derived). In Wi-Fi, the MAC uses contention access—all subscriber stations wishing to pass data through an access point are competing for the AP's attention on a random basis. This can cause distant nodes from the AP to be repeatedly interrupted by less sensitive, closer nodes, greatly reducing their throughput. By contrast, the 802.16 MAC is a scheduling MAC where the subscriber station only has to compete once (for initial entry into the network). After that it is allocated a time slot by the base station. The time slot can enlarge and constrict, but it remains assigned to the subscriber station meaning that other subscribers are not supposed to use it but take their turn. This scheduling algorithm is stable under overload and oversubscription (unlike 802.11). It is also much more bandwidth efficient. The scheduling algorithm also allows the base station to control Quality of Service by balancing the assignments among the needs of the subscriber stations.

A recent addition to the WiMAX standard is underway which will add full mesh networking capability by enabling WiMAX nodes to simultaneously operate in "subscriber station" and "base station" mode. This will blur that initial distinction and allow for widespread adoption of WiMAX based mesh networks and promises widespread WiMAX adoption.

The original WiMAX standard, IEEE 802.16, specifies WiMAX in the 10 to 66 GHz range. 802.16a added support for the 2 to 11 GHz range, of which most parts are already unlicensed internationally and only very few still require domestic licenses. Most business interest will probably be in the 802.16a standard, as opposed to licensed frequencies. The WiMAX specification improves upon many of the limitations of the Wi-Fi standard by providing increased bandwidth and stronger encryption. It also aims to provide connectivity between network endpoints without direct line of sight in some circumstances. The details of performance under non-line of sight (NLOS) circumstances are unclear as they have yet to be demonstrated. It is commonly considered that spectrum under 5-6 GHz is needed to provide reasonable NLOS performance and cost effectiveness for PtM (point to multi-point) deployments. WiMAX makes clever use of multi-path signals but does not defy the laws of physics.

Uses for WiMAX

WiMAX is a wireless metropolitan area network (MAN) technology that can connect IEEE 802.11 (Wi-Fi) hotspots with each other and to other parts of the Internet and provide a wireless alternative to cable and DSL for last mile (last km) broadband access. IEEE 802.16 provides up to 50 km (31 miles) of linear service area range and allows connectivity between users without a direct line of sight. Note that this should not be taken to mean that users 50 km (31 miles) away without line of sight will have connectivity. Practical limits from real world tests seem to be around "3 to 5 miles" (5 to 8 kilometers). The technology has been claimed to provide shared data rates up to 70 Mbit/s, which, according to WiMAX proponents, is enough bandwidth to simultaneously support more than 60 businesses with T1-type connectivity and well over a thousand homes at 1Mbit/s DSL-level connectivity. Real world tests, however, show practical maximum data rates between 500kbit/s and 2 Mbit/s, depending on conditions at a given site.

It is also anticipated that WiMAX will allow interpenetration for broadband service provision of VoIP, video, and Internet access—simultaneously. Most cable and traditional telephone companies are closely examining or actively trial-testing the potential of WiMAX for "last mile" connectivity. This should result in better pricepoints for both home and business customers as competition results from the elimination of the "captive" customer bases both telephone and cable networks traditionally enjoyed. Even in areas without preexisting physical cable or telephone networks, WiMAX could allow access between anyone within range of each other. Home units the size of a paperback book that provide both phone and network connection points are already available and easy to install.

There is also interesting potential for interoperability of WiMAX with legacy cellular networks. WiMAX antennas can "share" a cell tower without compromising the function of cellular arrays already in place. Companies that already lease cell sites in widespread service areas have a unique opportunity to diversify, and often already have the necessary spectrum available to them (i.e. they own the licenses for radio frequencies important to increased speed and/or range of a WiMAX connection). WiMAX antennae may be even connected to an Internet backbone via either a light fiber optics cable or a directional microwave link. Some cellular companies are evaluating WiMAX as a means of increasing bandwidth for a variety of data-intensive applications. In line with these possible applications is the technology's ability to serve as a very high bandwidth "backhaul" for Internet or cellular phone traffic from remote areas back to a backbone. Although the cost-effectiveness of WiMAX in a remote application will be higher, it is definitely not limited to such applications, and may in fact be an answer to expensive urban deployments of T1 backhauls as well. Given developing countries' (such as in Africa) limited wired infrastructure, the costs to install a WiMAX station in conjunction with an existing cellular tower or even as a solitary hub will be diminutive in comparison to developing a wired solution. The wide, flat expanses and low population density of such an area lends itself well to WiMAX and its current diametrical range of 30 miles. For countries that have skipped wired infrastructure as a result of inhibitive costs and unsympathetic geography, WiMAX can enhance wireless infrastructure in an inexpensive, decentralized, deployment-friendly and effective manner.

Another application under consideration is gaming. Sony and Microsoft are closely considering the addition of WiMAX as a feature in their next generation game console. This will allow gamers to create ad hoc networks with other players. This may prove to be one of the "killer apps" driving WiMAX adoption: WiFi-like functionality with vastly improved range and greatly reduced network latency and the capability to create ad hoc mesh networks.

Product release

Cities of Los Angeles, New York, Boston, Dalian, Chengdu in 2005

As of 2005, major cities in the USA such as Los Angeles, New York, Chicago, Boston, Providence (Rhode Island), and San Francisco are served by Towerstream. Seattle is served by Sprint and Speakeasy.net. In China, Dalian and Chengdu are implementing pre-WiMAX networks that will be upgradeable when certification testing begins in late 2005. In Chile, Entel announced that will start offering WiMax in 2006. Current Towerstream, Speakeasy, and other deployments are of proprietary systems including Airspan Networks, Aperto, Alvarion VL OFDM, and Dragonwave. Trial deployments have been mostly outside of the U.S. due to limited spectrum availability. Sprint has announced that they will begin trials of pre-certified WiMAX systems. Towerstream will also introduce WiMAX systems to follow their highly successful pre-WiMAX network servicing businesses, educational facilities and government entities.

At the July 2005 WiMAX Forum meeting in Vancouver, BC, WiMAX systems began certification testing. Disney took part in the Proof of Concept (POC) display. This showed real simultaneous multi-media capabilities.

PCMCIA, FPGA

Beyond these metro area rollouts, WiMAX is like Wi-Fi in that you can "roll your own". Several vendors have some form of product now (2004), usually in a pre-standards-compliance stage so multivendor interoperability within a single network segment can't be reasonably expected. Several companies are planning rollouts of compliant chipsets in FPGAs in 2005 and ASICs the following year which will shrink the digital electronics suitable for PCMCIA and MiniPCI type of form factors. Intel is expected to be a major driver towards price reduction. Taken at face value, Intel claims to be able to drive the price per user to zero over the next 3-4 years. That is due to embedding WiMAX into the system processors and board architectures for laptop, PDA and other devices. Of course, the price is not zero as premium features drives acceptance of premium 'Intel Inside' driven designs. But as a competitive positioning strategy, the ability to embed multi-mode WiMAX/WiFi/cellular into consumer and IT products should create a compelling argument for WiMAX's acceptance.

WiBro:South Korean version

Perhaps the most telling deployments for WiMAX will be for the WiBro mobile derivative: WiBro has South Korean government support with the requirement for each carrier to spend over $1 billion US for deployments. The Koreans sought to develop WiBro as a regional and potentially international alternative to 3.5-4G systems. But given the lack of self developed momentum as a standard, WiBro has joined WiMAX and agreed to harmonize with the similar OFDMA 802.16e version of the standard. What makes WiBro roll outs, which will start in April of 2006, a good 'test case' for the overall WiMAX effort is that it is mobile, well thought out for delivery of wireless broadband services, and the fact that the deployment is taking place in a highly sophisticated, broadband saturated market. WiBro will go up against 3G and very high bandwidth wire line services rather than as gap-filler or rural under-served market deployments as is often exampled as the 'best fit' markets for WiMAX. WiBro goes much more "in your face" in direct competition with 3G and high bandwidth wired services which pose tough competition.

Targeting Network SPs not Consumers

Early products are likely to be aimed at network service providers (SPs) and businesses, not consumers. It has the potential to enable millions more to have wireless Internet connectivity, cheaply and easily. Proponents say that WiMAX wireless coverage will be measured in square kilometers while that of Wi-Fi is measured in square meters. According to WiMAX promoters, each WiMAX node or "base station" would enable high-speed Internet connectivity between homes and businesses in a radius of up to 50 km (31 miles). (It should be noted that these claims, especially that such distances can be achieved without LOS (line of sight), represent, at best, a theoretical maximum under ideal circumstances. The technical merit of these claims has yet to be tested in the real world.) These base stations will eventually cover an entire metropolitan area, making that area into a WMAN and allowing true wireless mobility within it, as opposed to hot-spot hopping required by Wi-Fi. Its proponents are hoping that the technology will eventually be used in notebook computers and PDAs. True roaming cell-like wireless broadband, however, will require 802.16e.

Qualcomm acquires Flarion

The acquisition of Flarion [1] by mobile wireless heavyweight Qualcomm and the re-posturing of their systems and OFDM patent portfolios as being central to OFDMA/802.16e developments has broadened the level of interest in the emerging field of OFDM wireless. Some question the motives of Qualcomm: is this an attempt to stall adoption of WiMAX? Or is this more a recognition by Qualcomm that OFDM will likely become a predominant core technology for 4G and beyond wireless systems?

Intel Wimax Collaborations w/ Nokia, Intel in 2005

In June, Nokia and Intel Corporation announced a cooperation to accelerate the development, adoption and deployment of (IEEE 802.16e) Areas of development include mobile clients, network infrastructure, industry-enabling efforts and market development. For mobile devices and notebook platforms, base station strategies to help deploy a WiMAX network infrastructure that will provide adequate and reliable coverage.

Motorola Inc. and Intel Corporation announced on October, 2005, their plan to collaboratively adoption of mobile WiMAX based on the proposed IEEE 802.16e standard, for both fixed and wireless broadband applications. Interoperability testing of Motorola mobile devices, network equipment, and customer premises equipment with Intel products.

Standards

WiMAX Forum logo
WiMAX Forum logo

The current 802.16 standard is IEEE Std 802.16-2004, approved in June 2004. It renders the previous (and 1st) version 802.16-2001 obsolete, along with its amendments 802.16a and 802.16c.

IEEE Std 802.16-2004 addresses only fixed systems. An amendment 802.16e is in the works which adds mobility components to the standard. This amendment is expected to be published in February 2006.

  • 802.16-2004 IEEE Standard for Local and metropolitan area networks Part 16: Air Interface for Fixed Broadband Wireless

IEEE 802.16e

IEEE 802.16-2005, approved December, 2005, (formerly named 802.16e), the WiMAX mobility standard, is an improvement on the modulation schemes stipulated in the original WiMAX standard. It allows for fixed wireless and mobile Non Line of Sight (NLOS) applications primarily by enhancing the OFDMA (Orthogonal Frequency Division Multiplexing Access).

Many think that by stipulating a new modulation method called Scalable OFDMA (SOFDMA), 802.16-2005 will make the older 802.16-2004 which uses OFDM-256 obsolete. However, several manufacturers plan for a migration path from the older version of the standard to the more robust, mobile modulation scheme. In any case, manufacturers are working through the WiMAX Forum to achieve compatibility between similar system profiles.

SOFDMA will improve upon OFDM256 for NLOS applications by:

SOFDMA and OFDMA256 are not compatible so most equipment will have to be replaced. However, some manufacturers are attempting to provide a migration path for older equipment to OFDMA256 compatibility which would ease the transition for those networks which have already made the SOFDMA investment.

  • [2] SR Telecom. IEEE 802.16e Standard: What will it mean for fixed wireless applications.

Similar technologies

UMTS is a direct competitor to WiMAX. UMTS has been deployed in Europe and elsewhere mostly by Mobile Telephone operators. The HSDPA technology enables downlink with data transmission up to 8-10 Mbit/s. In July 2005 EU frequency allocation for WiMAX was blocked by France and Finland, where manufacturers have invested heavily in UMTS technology.

Unlike earlier broadband wireless access (BWA) iterations WiMAX is highly standardized which should reduce costs. However, since Chipsets are custom-built for each broadband wireless access manufacturer, this adds time and cost to the process of bringing a product to market, and this won't be changed by WiMAX.

WiMAX's equivalent or competitor in Europe is HIPERMAN. WiMAX Forum, the consortium behind the standardization, is working on methods to make 802.16 and HIPERMAN interoperate seamlessly. Products developed by the WiMAX Forum members need to comply to pass the certification process.

Korea's telecoms industry has developed its own standard, WiBro. In late 2004, Intel and LG Electronics have agreed on interoperability between WiBro and WiMAX.

See also


WiMax Equipment Manufacturers

WiMAX Test Equipment Companies

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