WiMax Guide

Light Reading
Light Reading

2005 will probably be the year in which WiMax sinks or swims as the next big thing in telecom technology. For that reason, plenty of people are going to need a quick and easy way of getting up to speed on what WiMax is and why it's stirring up so much interest.

This report aims to provide that quick and easy guide, by answering questions that are most frequently asked about WiMax. In the report's initial form, answers to eight basic questions are given, one per page. But the idea is that readers can ask further questions on the message board attached to this article. If you want to send a private message, please email [email protected] and include "WiMax Guide" in the subject field. Frequently posed questions will be answered by adding pages to this report.

For those that just want a high-level understanding of WiMax, here are the key points:

  • WiMax is a broadband access technology that delivers high-speed, carrier-grade Ethernet data communications by wireless over city-sized distances.
  • Its main use initially will be to deliver broadband Internet connections to buildings by wireless and to provide links between WLAN hotspots and carriers’ core IP networks (backhaul); later, individual user devices such as PCs will be connected direct, and, eventually, mobile devices.
  • Its big attractions are expected to be the usual Ethernet and wireless virtues of low costs, flexibility, ease of rollout and use, and interoperability.
  • However, WiMax is not expected to be fully commercialized until about 2006.

Industry opinions are divided over WiMax's prospects, judging by early results of a poll being conducted on Unstrung, Light Reading's sister Website covering wireless technologies. So far, 48 percent of respondents say WiMax will "emerge as a credible wireless replacement for DSL/cable" and exactly the same percentage say it will "splutter onto the market with minimal impact."

To take the poll yourself and see the full, up-to-date results, please click on this link.

Here's a hyperlinked list of the questions and answers in this report:

Webinar Archives on WiMax

Paid Research Reports on WiMax

— Tim Hills, Freelance Telecommunications Writer and Journalist

Need to know more about the latest developments in WiMax? check out the coming Light Reading Live! conference:

WiMax – Why Now?
at the W Hotel, Union Square, New York City, on Tuesday, January 20, 2005

This one-day event, hosted by Rick Thompson, Heavy Reading Analyst at Large, will provide qualified attendees from Light Reading's global audience an education in how WiMax will fit into their networking development plans for 2005 and beyond.

  • For more information, click here
  • To register, click here
  • Sponsorship opportunities are still available. Direct all inquiries to [email protected].

Loosely, WiMax is a standardized wireless version of Ethernet intended primarily as an alternative to wire technologies (such as cable modems, DSL, and T1/E1 links) to provide broadband access to customer premises. This application is often called wireless last/first-mile broadband because the transmission distances involved are typically of this order and the engineering problem is to bridge the final gap between the customer premises and the telco’s or service provider’s main network. The technology is specified by the Institute of Electrical and Electronics Engineers Inc. (IEEE), as the IEEE 802.16 standard.

More strictly, WiMax is the Worldwide Microwave Interoperability Forum, a non-profit industry body dedicated to promoting the adoption of this technology and ensuring that different vendors’ products will interoperate. WiMax will do this through developing conformance and interoperability test plans, selecting certification laboratories, and hosting interoperability events for 802.16 equipment vendors. But WiMax is such a convenient term that people tend to use it for the 802.16 standard and technology themselves, although strictly it applies only to systems that meet specific conformance criteria laid down by the WiMax Forum.

The 802.16 standard is large, complicated, and evolving, and offers many options and extensions, so interoperability is a major issue that must be addressed. In particular, one extension known as 802.16a became the focus of a lot of industry attention because it should be the easiest and most useful to implement. So it is likely that when people talk loosely of WiMax they are referring to the technology for fixed wireless specified by 802.16a and its later version 802.16d.

802.16 is one of a family of technologies being standardized by the IEEE (with other bodies, such as the European Telecommunications Standards Institute (ETSI), whose Hiperman standard is harmonized with 802.16) to create wireless versions of Ethernet that can operate over distances from a few meters to tens of kilometers -- from personal area networks (PANs), through local area networks (LANs) and metropolitan area networks (MANs), to wide area networks (WANs). 802.16 is the MANs member of the family.

WiMax is expected to offer initially up to about 40-Mbit/s capacity per wireless channel for both fixed and portable applications, depending on the particular technical configuration chosen. This should be enough, the WiMax Forum says, to support hundreds of businesses with T-1-speed connectivity and thousands of residences with DSL-speed connectivity.

What excites the industry is the combination of potential low cost and flexibility that WiMax promises. In principle, WiMax broadband networks can be built quickly and (compared to wireline systems) relatively cheaply by installing just a few wireless base stations mounted on buildings or poles to provide coverage to the surrounding area. The use of wireless eliminates the costly trenching and cabling of new wire/fiber networks, and Ethernet itself has a long history of achieving lower equipment costs than competing technologies. Although WiMax base stations, currently around $8,000, aren’t cheap for those used to paying under $100 for a WLAN access point, they are much cheaper for carriers than 3G cellular base stations.

And WiMax networks should scale well, as extra channels and base stations can be added incrementally as bandwidth demand grows.

WiMax can support both voice and video as well as Internet data. Its first application will be to provide wireless broadband access to buildings, either in competition to existing wired networks or alone in currently unserved rural or thinly populated areas. And it can also be used to connect WLAN hotspots to the Internet.

But WiMax is intended also to provide broadband connectivity mobile devices. It won’t be as fast in this application, but expectations are for about 15-Mbit/s capacity in a 3km cell coverage area.

Semiconductor vendors like Intel envisage WiMax-enabled chips appearing in PCs and other end-user equipment by 2006, and in PDAs and mobile phones by 2007 or 2008, raising the prospect of a mass market of users developing as it has for WLAN local Ethernet. If this happens, users could really cut free from today’s Internet access arrangements and be able to go online at broadband speeds almost wherever they like from within a "MetroZone," as the WiMax Forum puts it.

WLAN (or WiFi) is just an Ethernet local area network (LAN) that uses wireless instead of wires to connect PCs together and to on-premises servers, which are themselves connected by wire or fiber to, say, the Internet. WLAN is really designed to be local, and its low-power wireless doesn’t usually reach much more than 100 meters (and vastly less if walls get in the way -- typically about 30 m). The idea is that users can take their PC from one side of the room to another, or from one building to another, provided they can get near enough to a WLAN wireless base station there. But the PC must be very near to a base station for WLAN to work. So WLAN is basically an indoors technology with a very short range.

WiMax pretty much eliminates these constraints because it is designed to work over distances of up to 50 km and to create wireless metropolitan area networks (WMANs). So unlike WLAN, it’s intended to work outdoors and over fairly long distances, although the distances used in practice will be much less than the maximum. This means it is a more complex technology and has to handle issues of importance to carriers and service providers, such as quality-of-service (QOS) guarantees and carrier-class reliability. It is not intended to replace WLANs; instead, the two technologies complement each other.

WiMax is still a work in progress. The standard that specifies the technology is IEEE 802.16, but this is actually an expanding group of standards and revisions. The first came out in April 2002, but specified wireless frequencies were so high (in the range from 10 to 66 GHz) that it could be used only when the WiMax base station and the client have an unimpeded line of sight between them, as obstructions like walls and buildings cut off the radio waves. This is a weakness for the target urban/suburban environment, and causes problems even in rural areas. So an amendment to the standard, called 802.16a, emerged in January 2003 and extended the technology down to lower frequencies (down to 2 GHz), which do not need an unimpeded line of sight. Later revisions are consolidated in 802.16d (for fixed wireless), and a further amendment, 802.16e, is to cover connections for mobile devices.

A WiMax network has a number of base stations and associated antennas communicating by wireless to a much larger number of client devices (or subscriber stations) – a point-to-multipoint configuration. Base stations are either directly wired to the Internet or use WiMax links to other base stations that are so connected. Client devices initially are generally small, building-mounted antenna/transceiver systems to which in-building LANs (such as WLANs) are connected. But future clients – depending on the frequency bands used – will often be integrated into end-user devices, such as notebook PCs and, eventually, mobile devices, such as PDAs and smartphones.

Each base station provides wireless coverage over an area called a cell. Although the maximum radius of a cell is theoretically 50 km (depending on the frequency band chosen), typical deployments will use cells of radii from 3 to 10 km. As with conventional cellular mobile networks, the base-station antennas can be omnidirectional, giving a circular cell shape, or directional to give a range of linear or sectoral shapes for point-to-point use or for increasing the network’s capacity by effectively dividing large cells into several smaller sectoral areas.

A lot of effort has gone into making the wireless technology very robust and flexible so it will work well in a range of different environments around the world. This was a major area of work in the development of the 802.16a version. For example, it can withstand the effects of multiple radio reflections (or echoes) from buildings and other obstacles in the transmission path – a major problem in built-up environments. Different channel sizes and methods of providing two-way communications are supported so that the technology can accommodate different national regulatory and technical requirements. And, importantly, WiMax supports smart antenna systems, which are rapidly becoming less expensive and are very effective in reducing the effects of radio interference and the wireless power needed. This is done by using four antennas at the base station instead of just one. Each of the four antennas transmits and receives the same data signal, but at slightly different times. By clever signal processing, the best signal can always be extracted. To get the same performance with a single antenna, vastly more wireless power would be needed, increasing costs and the problems of interference and cell planning.

A further bonus of WiMax is that it supports mesh networks. This means that WiMax-enabled devices can act as relays, passing signals from one device to another until they reach a WiMax base station from which they can enter the wired Internet. Relaying like this greatly extends the potential range of an access point, and allows networks to grow in an organic fashion.

WiMax is based on a version of 802.16 uses radiowaves in the range from 2 to 11 GHz. At these frequencies, radiowaves can penetrate some way into buildings, and can bend and reflect around obstacles to some extent, so the base station and client antennas do not need a clear line of sight between them, which is much more practical in an urban environment. But there is also another significant consequence due to the nature of spectrum regulation.

Different versions of WiMax are defined at these lower frequencies, partly as a result of differing national regulations governing wireless spectrum. For example, a frequency at 3.5 GHz requires a wireless operating license and will have the full 50km range (although most uses will probably be around 6 to 10 km). However, those at 2.4 or 5 GHz do not require a license in most regulatory jurisdictions, because these frequency bands allow unlicensed use. In these bands, WiMax operates at a much lower wireless power and has a very limited range (roughly the same as for WLAN, which also uses these frequency bands). But it does mean that unlicensed low-power mesh networks can be constructed. Combined with the mesh capability, unlicensed, DIY, low-power WiMax could (once prices fall sufficiently) begin to spread through the suburbs and villages as a grownup alternative to WLAN-supplied broadband.

As with any new technology, there are issues facing WiMax.

A big one for service providers is that WiMax is just Ethernet. That is, it's only a tiny part of what is needed to make broadband applications work. A lot will have to be done to application-layer and other standards to ensure that end services can interoperate satisfactorily.

Another issue is the bandwidth a user can expect. In theory, depending on which technical options are used and on the system configuration, under ideal conditions a single 802.16 base-station channel can support from 32 to 135 Mbit/s. But, in practice, about 40 Mbit/s for cell radii of between 3 to 10 km looks much more realistic. Furthermore, as with all Ethernet technologies, this bandwidth is shared by all the simultaneous users of a base station, so there is a trade-off between the number of base-station users and the bandwidth available to each of them.

Security is being strengthened, as it is a very big issue when using wireless over longer outside transmission paths. Currently WiMax uses Data Encryption Standard (DES) or Triple DES, but the stronger Advanced Encryption Standard (AES) will be incorporated by the time full-scale commercialization begins.

A very practical issue is that the 802.16 standards are deliberately constructed to allow considerable vendor product differentiation and innovation. Although the WiMax branding will ensure basic interoperability between different vendors’ products, this will not necessarily extend to the finer points of ensuring optimum transmission efficiency, for example.

Despite (or perhaps, because of) the flexibility built into WiMax’s requirements for radio spectrum, there are big practical and policy issues still to be tackled by spectrum regulators if WiMax is to flourish. There is, for example, the theoretical possibility that 2.4GHz-band WiMax might interfere with WLAN in some countries, depending on the exact frequencies allocated and used. Because national spectrum allocations and regulations differ so considerably (despite the international harmonization work of the ITU), there are as of yet no global frequency bands to which equipment could conform to maximize vendors’ economies of scale and hence, minimize equipment prices. And national spectrum regulations can currently deny service providers access to spectrum suitable for WiMax.

The WiMax Forum hopes that global harmonization can be achieved by 2006 on at least the following bands for broadband wireless applications:

  • License-Exempt 5GHz: Especially bands between 5.25 and 5.85 GHz.
  • Licensed 3.5GHz: Mainly between 3.4 and 3.6 GHz (but some new allocations are between 3.3 and 3.4 GHz and between 3.6 and 3.8 GHz). Many countries (but not the U.S.) have allocated bands between 3.4 and 3.6 GHz.
  • Licensed 2.5GHz: U.S., Mexico, Brazil, and some Southeast Asian countries have allocated bands between 2.5 and 2.69 GHz.

It is possible also that bands below 1 GHz, released as the result of the move to digital TV, might be used for WiMax eventually.

But probably the biggest issue of all is that WiMax is a new infrastructure technology that will have to be extensively rolled out if it is to fulfill its promise, as low equipment prices will depend on large volumes, especially at the client/CPE end of the business. And this is where things get a little sticky, as extensive new-technology infrastructures are not nowadays usually high up on CEOs’ how-to-boost-your-share-price tip sheets. This is especially true for vertically integrated incumbent telcos, which have spent billions of dollars recently building 3G mobile networks that will eventually be trespassing on some of the same market for broadband IP applications as WiMax. And these same telcos are also having to come to grips with the need to invest in broadband copper enhancements and increased fiber in their access networks. WiMax might well be one distraction too many.

Even the WiMax Forum admits that more work needs to be done on the WiMax business case. A presentation given by Dr. Mo Shakouri, WiMax Forum board member and VP of marketing, at WiMax Con in October 2004, gave an example business case for the U.S. market. While concluding the business case was “satisfactory” for the scenarios considered, he pointed out that WiFi hotspot and mobile backhaul – two obvious early applications – will not support a standalone business, and that the fastest payback would come from mobile Internet. However, the latter was affected by the availability of integrated WiMax user devices, and more additional analysis on projected WiMax-enabled devices (including smartphones and PDAs) over the next five years was needed.

The obvious answer is anyone seeking to compete with the incumbent telco and cable operator for broadband and broadband-based applications such as VOIP. So WiMax could well be the technology that breaks the local-loop monopoly for, say, adventurous and well funded ISPs wanting to differentiate themselves and escape from their dependence on the local telco. But fixed-line carriers and service providers generally, including incumbents and CLECs, could find WiMax very attractive for parts of their networks and for specific applications, such as backhaul from remote sites, such as cellular base stations.

There is also a wider picture, in which WiMax becomes an enabler of a more seamless mode of communications, essentially built on Ethernet. In this, WiMax provides blanket Ethernet coverage of an urban, suburban, or rural area to make broadband ubiquitous. Individual devices, such as notebook PCs and PDAs, will be able to use both WLAN and WiMax. WLAN in hotspots (which may in turn be connected to carriers core IP networks by WiMax backhaul), and WiMax when away from a WLAN hotspot or when WiMax’s QOS capabilities are required for applications such as video.

However, an intriguing question is where this potentially seamless WiMax world leaves mobile operators, especially those implementing 3G. Portable WiMax-enabled devices could easily outperform 3G devices for many bandwidth-intensive applications, especially those oriented towards business, where a common Ethernet environment would be very attractive.

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