WiMAX

WiMAX is defined as Worldwide Interoperability for Microwave Access by the WiMAX Forum [1], formed in April 2001 to promote conformance and interoperability of the standard IEEE 802.16, also known as WirelessMAN. 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."
IntroductionThe IEEE 802.16 media access controller (MAC) is significantly different from that of IEEE 802.11 Wi-Fi MAC. 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. And this makes services, such as VoIP or IPTV which depend on a determined level of quality of service (QoS) difficult to maintain for large numbers of users.
In 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 over-subscription (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. WiMAX/802.16's use of OFDMA and scheduled MAC allows wireless mesh networks to be much more robust and reliable.
The original WiMAX standard, IEEE 802.16, specifies WiMAX in the 10 to 66 GHz range. 802.16a, updated in 2004 to 802.16-2004, 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 802.16-2004 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 WiMAXWiMAX is a framework for wireless development based on a forward-looking core set of technologies. More recently 3GPP cellular's 4G, 802.22 Cognitive Radio RAN (Rural Area Network), and 802.20, the High Speed Mobile Broadband Wireless Access (MBWA) Working Group, have shifted toward use of similar constructs of multi-channel scalable OFDM, HARQ, FEC, MIMO-AAS and other complementary technologies as are part of WiMAX. WiMAX is designated as the 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. However, the field of uses is broader and overlaps those for mobile WAN (wide area networks) and WLANs. 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 inter-penetration 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 price-points 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 "back-haul" 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 back-hauls 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.
Spectrum Allocations for WiMAXThe 802.16 specification applies across a wide swath of RF spectrum, but specification is not the same as permission to use. There is no uniform global licensed spectrum for WiMAX. In the US, the biggest segment available is around 2.5GHz, and is already assigned, primarily to Sprint Nextel. Elsewhere in the world, the most likely bands used will be around 3.5GHz, 2.3/2.5GHz, or 5GHz, with 2.3/2.5 GHz probably being most important in Asia.
There is some prospect that some of a 700MHz band might be made available for WiMAX use, but it is currently assigned to the analog TV and awaits the complete rollout of HD digital TV before it can become available, likely by 2009. And, in any case, there will be other uses suggested for that spectrum if and when it actually becomes open.
It seems likely that there will be several variants of 802.16, depending on local regulatory conditions and thus on which spectrum is used. Even if everything but the underlying radio frequencies is the same. WiMAX equipment will not, therefore, be as portable as it might have been. And perhaps even less so than WiFi, whose assigned channels in unlicensed spectrum varies more than a little from jurisdiction to jurisdiction.
Product release
2005As 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 Canada, the University of Winnipeg has spearheaded a WiMax project in Winnipeg called LearningCITI and in Vancouver, BC by MetroBridge Networks. 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 it will start offering WiMax in 2006. Current Towerstream, Speakeasy, MetroBridgeand other deployments are of proprietary systems including Airspan Networks, Aperto, Alvarion VL OFDM, Redline Communications, 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 and MetroBridge 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. April 2005: Intel start shipping its highly integrated WiMAX chip, formerly codenamed "Rosedale" [3].
2006On January 20, 2006, Colombian company Telecom launched PRE-WiMAX on the city of Bucaramanga. In May 2006 the company Orbitel launched the first "WiMAX Forum Certified" network of Colombia and LatinAmerica on the city of Cali. Other Colombian cities such as Bogotá and Medellín have planned to launch WiMAX in 2006. Over 150 WiMAX and pre-WiMAX certified systems trials are now reported to be under way (WiMAX Forum). On March 20, 2006, UK start-up Urban Wimax launched the UK's first standards-based WiMAX network in Westminster. They will be targeting SMEs looking for symmetrical broadband connections. On March 31, 2006, a joint venture between Rogers Communications and Bell Canada announced availability of a national wireless broadband network based on pre-WiMAX standards that would cover over 100 urban and rural areas across Canada. At the time of the announcement, this deployment was one of the largest of its kind in the world. Among the more prodigious efforts to date are the roll-outs of WiBro/WiMAXm in South Korea: this is a well funded effort to provide service that will evolve from 'simple mobility' to full mobility that is harmonized with 802.16e-2005. Taiwan has similarly allocated 2.3 GHz spectrum and provided government support for WiMAX efforts which are expected to start trials in the second half of 2006. Numerous regional and national efforts have shown early success: Yozan has increased the plans to roll out WiMAX in Japan, a bellwether for wireless developments. Pakistan plans [4] [5] to implement the "World's Biggest WiMAX Network".
FIXED AND MOBILEApril 2006 is seeing the first releases of two, mutually incompatible, versions of WiMAX creating a challenge for everyone in the industry, namely, picking the version that will fare best in the long run. 802.16-2004 WiMAX only supports fixed access, but products are already available. 802.16e WiMAX supports mobile and fixed access but products are still at least a year away.
In one of the most significant WiMAX deployments to date, regional service provider Arialink Broadband, says it is building out a broadband wireless network for all of Muskegon County, Mich., using 802.16e equipment from Samsung Corp. Competition from wired technologies (DSL, cable modem, fiber-to-the-home) and from wireless technologies (Wi-Fi, 3G including WCDMA, HSDPA, EV-DO, TD-CDMA, and proprietary solutions like Qualcomm's FLASH-OFDM) has made it a very broad connectivity market.
Recently announced in Red Herring.com, Clearwire, - a so called 'start-up' - is looking to invest about $1 billion in funds to build its own WiMAX network. Towerstream, has continued to service large cities in the United States, testing and installing WiMAX certified equipment as it is officially released.
The WiMAX Forum member companies and products to complete certification and interoperability testing include Airspan's MacroMAX base station and EasyST subscriber station solution, Axxcelera's ExcelMax base station, Sequans Communications' SQN1010-RD subscriber station solution, Siemens AG WayMAX@vantage base station and subscriber station solutions, Aperto's Packetmax 5000 base station, Redline Communication's RedMAX base station and subscriber unit, Proxim Wireless Tsunami MP16 3500, and Wavesat's miniMAX subscriber station solution.
PCMCIA, FPGABeyond these metro area rollouts, WiMAX is similar to Wi-Fi in that the consumer can "roll your own". April 2006 has many companies moving into the WiMAX arena. Intel continues to be a major driver in the worldwide implementation towards the proliferation and 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 which increases exponentially with each successful deployment.
WiBro: South Korean versionPerhaps 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 US$1 billion 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 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. Telecom Italia, the dominant telephony and internet service provider in Italy has announced it will test, together with Korean Samsung Electronics, a WiBro network service, starting with the Winter Olympic Games 2006, held in Turin.
Targeting network service providers, not consumersEarly 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).
These claims, especially that such distances can be achieved without LOS (line of sight), represent, at best, a theoretical maximum under ideal circumstances. They have 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 FlarionThe acquisition of Flarion [6] 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 with Nokia, Motorola in 2005In 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 collaborative 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.
StandardsThe 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 802.16eIEEE 802.16-2005, approved December, 2005 (formerly named but still best known as 802.16e or Mobile WiMAX). The WiMAX mobility standard, is an improvement on the modulation schemes stipulated in the original (fixed) WiMAX standard. It allows for fixed wireless and mobile Non Line of Sight (NLOS) applications primarily by enhancing the OFDMA (Orthogonal Frequency Division Multiple 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:
Improving NLOS coverage by utilizing advanced antenna diversity schemes, and hybrid-Automatic Retransmission Request (hARQ) Increasing system gain by use of denser sub-channelization, thereby improving indoor penetration Introducing high-performance coding techniques such as Turbo Coding and Low-Density Parity Check (LDPC), enhancing security and NLOS performance Introducing downlink sub-channelization, allowing administrators to trade coverage for capacity or vice versa Improving coverage by introducing Adaptive Antenna Systems (AAS) and Multiple Input Multiple Output (MIMO) technology Eliminating channel bandwidth dependencies on sub-carrier spacing, allowing for equal performance under any RF channel spacing (1.25-14 MHz) Enhanced Fast Fourier Transform (FFT) algorithm can tolerate larger delay spreads, increasing resistance to multipath interference 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 SOFDMA compatibility which would ease the transition for those networks which have already made the OFDMA256 investment.
[7] SR Telecom. IEEE 802.16e Standard: What will it mean for fixed wireless applications. [edit]Similar technologiesUMTS is a direct competitor to WiMAX. UMTS has been deployed in Europe and elsewhere mostly by Mobile Telephone operators. The HSDPA technology enables down-link 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.
The most recent UMTS 3GPP+ efforts are development of 4G systems based on OFDM rather than CDMA. The 3GLTE/HSOPA platform will be based on MIMO-OFDM basically similar to WiMAX/802.16e-2005. This is both a great endorsement that WiMAX represents the 'framework for the wireless broadband revolution' and a great threat of competition that is free to 'embrace and extend' the new set of wireless technologies. 3.5-3.9G cellular are sufficiently worthy of being labeled 'wireless broadband' and will be competition to WiMAX in several markets. Taking the 'glass half full' position: WiMAX was early to adopt the 'right set' of emerging technologies and is now on course to capture a share of a growing and diverse market for wireless products and WBB based or extended services.
Convergence is more than an industry buzzword: it is taking place both at the rudimentary levels of standards development and component and systems designs and at the macro levels of company acquisitions, telecommunications reform legislation and spectrum regulation. A major factor of the success of WiMAX has to do with the socio-economic and political factors. First you have to get the framework for the evolution of technology on the right path. But that also has to be aligned with the broader macro trends that favor development and international adoption. For numerous reasons WiMAX appears to align quite well.
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 inter-operate 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.

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