WiMAX: The Critical Wireless Standard

2. Introduction

The past few months have seen a storm of debate about the economics and return on investment of Wi-Fi hotspots. What almost all the arguments entirely ignore is the standard lurking on the horizon, which will turn current assumptions on their head. This is the 802.16x wireless metropolitan area network (WMAN) specification, which is being developed and promoted by the WiMAX industry group, whose most powerful members are Intel and Nokia. As with Wi-Fi, the WiMAX label has now become widely acceptable as a name for the standard itself.

Intel has called 802.16 “the most important thing since the Internet itself”, and even allowing for a dose of self-serving, it is not talking entirely in hyperbole.

In July, WiMAX showed off its first system profiles and interoperability tests at the WCA annual conference in Washington DC, in a significant step towards making the 802.16a standard, ratified by the IEEE in March, a commercial technology.

While a fully mobile version of WiMAX is in the wings, this first release will cover fixed wireless, and its supporters are focusing in particular on broadband last mile in unwired areas, and on backhaul for hotspots. Intel will start to make WMAN chips this year and we should see WiMAX products early in 2004.

These vendors are finally giving broadband wireless the teeth it needs, with a standards base, to take on wired options for the last mile and for long distance networking. The WiMAX (Worldwide Interoperability for Microwave Access) group was actually set up two years ago by Nokia, Ensemble and the OFDM Forum, but gained a new lease of life in April when it was revived by Nokia in collaboration with Intel and added five new members, with nine more joining in May.

The non-profit group takes a similar role to the Wi-Fi Alliance in WLANs, backing development of wireless Man products based on 802.16 and working on standards certification and interoperability testing.

The initial version of the standard operates in the 10-66GHz frequency band and requires line of sight towers, but the 802.16a extension, ratified in March, uses the lower frequency of 2-11GHz, easing regulatory issues, and does not require line of sight. It boasts a 31 mile range compared to Wi-Fi’s 200-300 yards, and 70Mbps data transfer rates.

WiMAX president Margaret Labrecque says that collaborating on mass market products will achieve similar economies of scale to those seen in Wi-Fi WLAN devices. She says base stations will cost under $20,000 and support 60 enterprise customers with T1-class connections.

Systems based on the mobile version of the standard, which should ship towards the end of next year, about six months after fixed wireless products, will be able to achieve long distance wireless networking and will have far greater potential than Wi-Fi hotspots to provide ubiquitous coverage to rival that of the cellular network.

There is a plethora of wireless standards emerging in 2003 from the IEEE and IETF, but only WiMAX addresses all the key elements that are needed to make high end wireless a reality, and which existing proprietary last mile and broadband wireless access (BWA) technologies have failed fully to provide – a single standard for fixed broadband access and mobility, wireless WLAN backhaul, low cost of deployment, high scalability and the support of vendors with the power to drive the standard forward rapidly.

Intel is the foremost among these vendors and it is no coincidence that Labrecque is an Intel employee. As the head of Intel’s investment arm, Intel Capital, Sriram Viswanathan – the most eloquent of WiMAX’s supporters – says: “802.11 is the first key disruption. 802.16 is the next.”

In this research paper we examine the significance and potential impact of WiMAX, the obstacles in its path and its technological functions. We also look at how it interoperates and potentially clashes with other wireless standards in the WLAN and cellular markets, and its ability to replace wired systems in last mile and enterprise markets.

3. The 802.16a Standard

WiMAX – Not just another standard

Broadband wireless access provides more capacity at lower cost than DSL or cable for extending the fibre networks and supporting multimedia and fast internet applications in the enterprise or home. But it has been held back by the lack of a standard, so that solutions have been based on proprietary, single-vendor efforts. Standardization through the IEEE 802.16 specification raises the potential to:

• Stall wired broadband and make wireless the key platform of the future •

Extend the range of Wi-Fi so that the myth of ubiquitous wireless can become a reality

Provide an alternative or complement to 3G

• Provide an economically viable communications infrastructure for developing countries and mobile blackspot regions in developed nations

Markets for WiMAX

The greatest media excitement about WiMAX has centred on its potential mobility and its role as a backhaul or even replacement for public Wi-Fi. However, its initial raison d’etre and still its primary focus is on broadband fixed wireless access for homes and businesses. This sector is populated by a horde of mainly American niche players with expensive equipment using various versions of smart antennas, OFDM and sometimes mesh to provide often effective alternatives to wired communications. ArrayComm, Alvarion, IPWireless, Navini and Beamreach are high profile names, though the majority of these specialists will refocus their products around WiMAX in the coming year (see later chapter).

Business users

Only 5 percent of commercial structures worldwide are served by fibre networks, the main method for the largest enterprises to access broadband, multimedia data services. In the wired world, these networks are extended to the business or residence via cable or DSL, both expensive options because of the infrastructure changes required. DSL typically operates at 128Kbps to 1.5Mbps and slower on the upstream.

Enterprises can use WiMAX instead of T1 for about 10 percent of the cost, while SMEs can

be offered fractional T1 services. Base stations will cost under $20,000 and support 60 enterprise customers with T1-class connections.

Last mile to the home

A low cost alternative could end the wars between the cable and ADSL operators and really make the broadband home revolution happen.

Hotspots

Wi-Fi hotspot operators may be able to build a spot for a few thousand dollars’ worth of equipment, but then they need to anchor it to the public network, and this is normally done with expensive T1 or DSL. WiMAX backhaul could significantly reduce hotspot costs, although there is also the potential for Wi-Fi to be bypassed altogether by WiMAX ‘hotzones’.

Remote regions

The most lucrative market for the proprietary BWA vendors has been remote regions, especially in developing countries but also in rural areas of the US, where there is no wired or cellular infrastructure nor the will or cash to invest in building it. The main alternative to BWA in this market is satellite. Still early in its lifecycle – and potentially a powerful technology to integrate with WiMAX – satellite has severe limitations of upstream bandwidth, spectrum availability and also suffers from high latency.

China

One of the most potentially lucrative markets for remote region BWA is, of course, China, and discussions have been held between the Chinese government and IEEE with a view to making 802.16 the Chinese national standard for fixed broadband wireless access at 3.5GHz. Chinese operators are already rolling out WiMAX base stations even before standard, low cost silicon is ready, and Alvarion recently supplied this type of equipment to China Unicom for a network covering, initially, six cities.

Background and 802.16

Although the 802.16 project started as far back as 1998, the body of work was done in 2000- 2003 in an open consensus process. The aim was to make broadband wireless access more widely and cheaply available through a standard for wireless metropolitan area networks.

The overall vision for 802.16 is that carriers would set up base stations connected to a public network. Each base station would support hundreds of fixed subscriber stations, probably mounted on rooftops. The base stations would then use the standard's medium access control layer (MAC) - a common interface that makes the networks interoperable - to nearly instantaneously allocate uplink and downlink bandwidth to subscribers according to their needs.

802.16 MANs could also anchor 802.11 hotspots, which serve as wireless local area networks (LANs), as well as servicing end users directly. With the mobile standard, users will be able to use the WMAN base station to communicate via handsets as they move within the 50 mile range.

The first version of the standard, 802.16, was published in April 2002 and addressed fixed, line of sight connections for the ‘first mile/last mile’ link. It focused on efficient use of various licensed frequencies in the 10-66GHz bandwidth.

802.16 standards have never taken a lowest common denominator approach. Unlike Wi-Fi, few proprietary vendors of equivalent equipment can outdo the performance of WiMAX. It 802.16 standards have never taken a lowest common denominator approach. Unlike Wi-Fi, few proprietary vendors of equivalent equipment can outdo the performance of WiMAX. It

Although, even with the upcoming mobile version of standard, WiMAX cannot be as wide area as 2G/3G, it delivers far higher rates and, with sufficiently widespread deployment, could significantly cut into the usage of cellular networks in many areas.

The next version of the standard, 802.16a, published in April 2003, is the one that has really kick-started WiMAX into being adopted as the dominant wireless broadband technology. This is also for fixed wireless but extends the range of WiMAX from 31 to 50 miles and operates in the low frequency 2-11GHz spectrum and so can be adopted by unlicensed operators. It uses point-to-multipoint or (optionally) mesh topologies and does not require line of sight. Specifically, it uses licensed bands at 3.5GHz and 10.5GHz internationally and 2.5-2.7GHz in the US; and unlicensed 2.4GHz and 5.725-5.825GHz.

An important aspect of 802.16x is that it defines a MAC (media access control) layer that supports multiple physical layer (PHY) specifications. This is critical to allow equipment makers to differentiate their offerings – for instance with novel approaches to smart antenna use – without becoming non-interoperable; and to customize the equipment for the frequency band in use.

Next on the agenda are: •

802.16c/d, published in Jan 2003, address interoperability by providing detailed system profiles and specifying combinations of options, as the basis for compliance and interoperability tests. The WiMAX Forum presented the first of these tests at the WCA conference in July 2003 and further work will be done by this body and the IEEE throughout this year. The ‘c’ protocol relates to protocols, test suite structures and test purposes while ‘d’ fixes errata and protocols not covered in ‘c’, and creates the system profiles.

• 802.16e, which adds mobility to the standard and really throws down the gauntlet to cellular. This element of the standard has the particular interest of Nokia, which can see a new revenue stream at both base station and handset level. The draft will be ready in August or September 2003.

• Probably, an important new project to enable handoff between Wi-Fi and WiMAX (see page 18).

Technical specifications of 802.16a

802.16 operates at up to 124Mbps in the 28MHz channel (in 10-66GHz), 802.16a at 70Mbps in lower frequency, 2-11GHz spectrum.

Fundamental technologies in 802.16a

OFDM

Support for OFDM (orthogonal frequency division multiplexing), which can continue to be implemented in various ways by different operators (the precise variant of OFDM can often

be their key differentiator).

OFDM is well established and is incorporated in some new generation carrier services as well as being fundamental to digital TV. It transmits multiple signals simultaneously across one cable or wireless transmission path, within separate frequencies, with the orthogonal element spacing these frequencies to avoid interference. It is also supported in the 802.11a WLAN standard.

802.16a has three PHY options: an OFDM with 256 sub-carriers – the only option supported in Europe by the ETSI, whose rival HiperMAN standard is likely to be subsumed into WiMAX; OFDMA, with 2048 sub-carriers; and a single carrier option for vendors that think they can beat multipath problems in this mode. OFDM will almost certainly become dominant in all wireless technologies including cellular and its industry body, the OFDM Forum, is a founder member of WiMAX Forum.

Support for Smart Antenna

Smart antenna mechanisms are one of the most important methods of improving spectral efficiency in non-cellular wireless networks. 802.16 standards allow vendors to support a variety of these mechanisms, which can be a key performance differentiator.

Dynamic frequency selection in unlicensed spectrum

Mesh

Mesh Mode is an optional topology for subscriber-to-subscriber communication in non-line of sight 802.16a. It is included in the standard to allow overlapping, ad hoc networks in the unlicensed spectrum and extend the edges of the WMAN’s range at low cost. Mesh support has recently been extended into the licensed bands too.

Figure 1 :Mesh networking

Source: Proxicast Although it has highly complex topology and messaging, mesh is a good alternative to the

usual NLOS, as it scales well and addresses license exempt interference. It allows a community to be densely seeded with WiMAX connections at low cost, with robust communications as there are multiple paths for traffic to take (see diagram).

Spectral efficiency

This is critical to support difficult user environments with hundreds of users per channel at high bandwidth and a mixture of continuous and burst traffic.

Protocol independent core

WiMAX can transport IPv4, IPv6, Ethernet or ATM and others, supporting multiple services simultaneously and with quality of service.

Bandwidth on demand (frame by frame)

Quality of Service

The ‘b’ extension to 802.16 is concerned with quality of service (QoS), which enables NLOS operation without severe distortion of the signal from buildings, weather and vehicles. It also supports intelligent prioritisation of different forms of traffic according to its urgency.

Mechanisms in the Wireless MAN MAC provide for differentiated QoS to support the different needs of different applications. For instance, voice and video require low latency but tolerate some error rate, while most data applications must be error-free, but can cope with latency. The standard accommodates these different transmissions by using appropriate features in the MAC layer, which is more efficient than doing so in layers of control overlaid on the MAC.

Adaptive Modulation

Many systems in the past decade have involved fixed modulation, offering a trade-off between higher order modulation for high data rates, but requiring optimal links, or more robust lower orders that will only operate at low data rates. 802.16a supports adaptive modulation, balancing different data rates and link quality and adjusting the modulation method almost instantaneously for optimum data transfer and to make most efficient use of bandwidth.

FDD and TDD

The standard also supports both frequency and time division duplexing (FDD and TDD) to enable interoperability with cellular and other wireless systems. FDD, the legacy duplexing method, has been widely deployed in cellular telephony. It requires two channel pairs, one for transmission and one for reception, with some frequency separation between them to mitigate self-interference. In regulatory environments where structured channel pairs do not exist, TDD uses a single channel for both upstream and downstream transmissions, dynamically allocating bandwidth depending on traffic requirements.

Security

802.16 also includes measures for privacy and encryption: authentication with x.509 certificates and data encryption using DES in CBC (cipher block chaining) mode with hooks defined for stronger algorithms like AES.

WiMAX leadership

Since the new-look WiMAX Forum was formed in April, the momentum behind 802.16a has gathered force and the standard has progressed with remarkable speed. Strong leadership is vital in the continuing evolution and rapid adoption of WiMAX and will help to set it apart from other mobile standards which are beset by politics.

There are significant names missing from WiMAX so far – its initial focus on last mile is indicated by the bias of the membership towards fixed wireless, OFDM specialists (the 802.16 specification is built on an implementation of OFDM from Wi-Lan of Canada), rather than enterprise focused suppliers or mobile carriers. Some major vendors will be taking the usual gamble of trying to establish such market presence for their proprietary solutions as to sideline the industry standard – Motorola with its Canopy broadband fixed wireless platform springs to mind. But these companies will join – Cisco being a critical target – and in the meantime, the really impressive aspect of WiMAX has been its clear focus and unity of purpose.

So far, perhaps because of its fairly low numbers, with most of these being smaller companies, it has avoided the complex politics and hidden agendas of most industry bodies – though this comes at the cost of a direction that is highly dominated by Intel and Nokia.

Chip advances

The main obstacles to long distance wireless are limitations on battery power and power efficiency. Regulations keep power levels low and the range of Wi-Fi signals short to avoid overcrowding of airwaves. But advances in fast digital signal processors mean that weak, jumbled signals can be deciphered, lengthening the distance that is practical for a transmission, as well as improving distance and speed potential. Battery improvements will also be vital to make a WiMAX cellphone a practicality.

Nokia is working on battery and handset chip designs to this end, citing two years as the likely timescale, while Intel is increasingly involved in next generation battery and processing power for mobile devices, including digital radios that can intelligently move to the most efficient available network – cellular, Wi-Fi, Bluetooth, WiMAX or UWB.

Currently, it looks as if Intel will entirely dominate the WiMAX chip market. Fujitsu and STMicroelectronics are also creating silicon but nearly all the next generation developments in radio and wireless processor chips that will be important to fixed and mobile 802.16 are being led by Intel, as is the political agenda.

HIPERMAN

An alternative standard to 802.16a is the European Telecommunication Standards Institute’s BRAN HA (Broadband Radio Access Networks HiperAccess) or HiperMAN. This is likely to

be subsumed into 802.16a. April, Nokia and Siemens Information and Communication Mobile said they would coordinate an effort to integrate the two standards to achieve a single worldwide standard combining the best of both specifications and provide a migration path from current proprietary products to an IP-optimised solution.

ETSI has two specifications, Hiperaccess, which operates above 11GHz, and HiperMAN for below 11GHz, which will be harmonized with 802.16a OFDM.

This illustrates the advantage WiMAX has derived from its strong and single minded focus, which has enabled it to largely avoid the political upheavals that have disrupted other efforts such as Wi-Fi and Mobile-Fi.

Contrast the political fiasco that scuppered the fast Wi-Fi standard, 802.11a, with the clarity of the 802.16a process. 802.11a had some technological shortcomings, notably its lack of Contrast the political fiasco that scuppered the fast Wi-Fi standard, 802.11a, with the clarity of the 802.16a process. 802.11a had some technological shortcomings, notably its lack of

In contrast, WiMAX has set out from the start to harmonize 802.16 and HiperMan, and the specifications it showcased in July demonstrated that unification. All this with remarkably little political in-fighting – the difference between leaving standards bodies to sort out their own futures, and putting a technology in the hands of vendors with a clear commercial objective, and deadline.

Operators

For mobile operators, there is a doubled edged sword. WiMAX is particularly disruptive because no physical last mile installation is required and the base stations will cost under $20,000 using commodity standard hardware. As with Wi-Fi hotspots, fixed and mobile operators will have an equal interest in extending their networks through WiMAX, and also ensuring that any revenues lost to 3G and wired services are at least preserved within the company. But WiMAX also gives the opportunity for small, alternative operators to enter the game.

License exempt wireless ISPs will start to offer WiMAX fixed wireless service. There are already about 1,800 such WISPs in the US, many just focused on Wi-Fi but some already eyeing the metro area. Before WiMAX, such operators had to either use Wi-Fi, or turn to proprietary BWA gear to provide features that Wi-FI lacks such as QoS.

As the FCC and equivalent authorities in other parts of the world become more friendly to freeing up new spectrum, more broadband WISPs will spring up, especially if the US administration gives into pressure to open up some unused MMDS wireless broadband spectrum.

Figure 2: Worldwide sub-11GHz subscriber base - 802.16a and proprietary

4.5 MidEast/Africa

4.0 Asia

3.5 Europe Americas

3.0 s (millions) 2.5

iber 2.0

Source: Intel Capital

WiMAX operates in a mixture of licensed and unlicensed spectrum, and the initial products will be focused on 2.5GHz and 3.5GHz licensed and 5.8GHz unlicensed bands (though the full standard supports a far wider range of bands). The licensed spectrum gives operators the chance to apply for franchises for fixed wireless broadband provision, especially in rural and remote areas, and to build the infrastructure with low cost, commodity hardware - something Intel is promoting assiduously as a means to increase investment in Centrino- enabled PCs (it now has a director of rural broadband access).

The unlicensed aspect means that independents have the chance to provide backhaul services for hotspots, which have the potential to create a nationwide wireless network. If the operators can control this, as they have been trying to do with Wi-Fi, they will be able to offer parallel, integrated services and achieve a stopgap as they struggle towards ubiquitous 3G – one with lower margins than cellular perhaps, but swifter ROI on lower upfront investment. They certainly have the power and resource to take control from alternative network suppliers, but they may also be condemning their 3G investments to stillbirth.

But the genie is out of the bottle now, and while the operators hesitate, the equipment makers are driving ahead, Intel in the vanguard, and Nokia, which has supported WiMAX from its earliest days, looking forward to the mobile standard and to the chance to add a new form of base station business to its ailing networks unit.

The vendors

Recently, a much publicized article in The Wall Street Journal pointed out how Wi-Fi has already slipped out of the hands of the start-ups. Unlike in other technology booms, none of those start-ups looks set to grow up to be a dominant player; instead, the established giants have sidestepped to take control of the new sector, Intel and Cisco in particular.

The same process is likely to happen in WiMAX, certainly at the chip and hardware level. In fact, the main question is whether anybody can stop Intel and Nokia completely dominating this market, blocking entry to everybody else with their aggressive early action.

Of course, the availability of low cost equipment will help to make the business models of some of the BWA specialists more viable, and partnership with Intel could ensure the survival of companies such as Alvarion.

However, cheap components will also lower barriers to entry and cause a shakeout in which many of the less well funded developers of smart antenna, OFDM systems will perish. Similarly, as WiMAX becomes a mainstream option for last mile and rural BWA, it is likely to attract the attention of large operators looking for new revenue streams and some of the alternative and niche operators may be pushed out too.

As well as Intel, the first WiMAX products are likely to come from: •

Enterprise WLAN maker Proxim, which has WiMAX equipment in the labs •

Ensemble Communications

• Flarion, the Cisco-backed last mile player, which has a trial running in South Korea of wireless broadband gear using its smart antenna technology and supporting 802.16a. Korea is seen as the territory where wireless broadband is adopted most • Flarion, the Cisco-backed last mile player, which has a trial running in South Korea of wireless broadband gear using its smart antenna technology and supporting 802.16a. Korea is seen as the territory where wireless broadband is adopted most

• Fujitsu Microelectronics will be first with silicon. It is developing an 802.16a device that integrates the physical and media access control layers, which will include an ARM9 processor and will be ready later this year. The chip will cost about $300. Fujitsu will work with multiple providers of front end devices and recommend those compatible with its device.

• Taiwan-based Gen-WAN Technology has launched broadband wireless network equipment using 802.16a, offering base stations, fixed and mobile terminals, repeaters and network management systems. It will market its system, called BWIA, initially for public safety and military purposes, where WiMAX offers more reliable signals than cellular in emergency situations.

• Wi-Lan, one of the critical start-ups in WiMAX, has come to market with pre- standard system-on-chip solutions and will support the full standard soon. Its patented Wideband OFDM technology is included in the 802.16a standard and it has a manufacturing and development agreement with Fujitsu Microelectronics.

• Broadcom and Texas Instruments are also making noises about WiMAX and are expected to get into the market alongside Intel and Fujitsu. This is a sector where the chipmakers will define the core set of capabilities and control the core functions so that they take the primary role in driving proliferation of 802.16.

• The first Intel technology partners from the BWA arena, which will use the upcoming Intel products in their previously proprietary base stations, are Alvarion and Aperto Networks. Alvarion has an important contract to supply China Unicom with WiMAX equipment for its initial roll-out in six cities.

• AirTap Communications is one of the early entrants into the market for WiMAX networks in the US, serving SMEs and large enterprises in a range of metro districts.

4. Relationship With Other Wireless Technologies

Figure 3: The mobile standards compared

3G Wi-Fi:

WiMAX: Mobile-Fi:

802.16 802.20 Max speed

2Mbps 54Mbps 100Mbps 16Mbps

Coverage

Several miles

300 feet

50 miles

Several miles

Airwave

Licensed Unlicensed Either Licensed

Advantages

Range,

Speed, price

Speed, range Speed,

Short range

Interference

High price

expensive

issues?

Wi-Fi

The WiMAX Forum is keen to present 802.16 as complementary to the local area IEEE standard, 802.11 or Wi-Fi. In many ways, this is right—802.16a, as we have seen, provides

a low cost way to backhaul Wi-Fi hotspots and WLAN points in businesses and homes, and as uptake of Wi-Fi increases, the requirement for this backhaul will grow too.

But there is conflict too. WiMAX makes redundant the efforts of Wi-Fi specialists to extend the reach of their favourite technology and also places 802.11 into a far smaller role than its supporters have, often unrealistically, carved out for it. This is the opportunity for wireless technologies finally to grow up and offer the speed, multimedia support and ubiquity that Wi- Fi can never deliver.

The newer standard holds all the real power. By providing a backbone for hotspots, based on standards rather than the various proprietary WLAN expansion technologies out there, it makes the idea of a ubiquitous wireless network to rival cellular far more realistic than it ever was with Wi-Fi alone, despite the claims of the enthusiasts. The equipment makers are eyeing it keenly – amid all the doubts about the sustainability of the hotspot boom, anything that offers them a new product line plus helps to preserve the interest in Wi-Fi is to be welcomed.

802.16 is a highly complex standard which contains, from day one, many of the features that are being retrofitted, with various degrees of clumsiness and baggage, into Wi-Fi, which was originally conceived to be very simple and is now taking on a burden of responsibility beyond its technological reach.

WiMAX has the advantage of not being – at least until Intel has a long distance Centrino – a consumer technology. Although this has kept its profile lower than Wi-Fi’s, it has not suffered from the over-hype and its development is freer of vendor politics and posturing than its short distance cousin’s.

“We are trying to avoid referring to them by their letter," says 802.16 working group chair Dr Roger Marks. "At the moment we're not really going out to create something that you would sell to consumers. 802.16 is about base stations that connect the core networks as part of “We are trying to avoid referring to them by their letter," says 802.16 working group chair Dr Roger Marks. "At the moment we're not really going out to create something that you would sell to consumers. 802.16 is about base stations that connect the core networks as part of

And while 802.16 was conceived as a back end technology, 802.16e has the capacity to be adapted for individual computers, and has the QoS features to support voice - hence the interest from Intel and its Centrino plans.

WiMAX has various features that make it suitable to the longer distance, although some like QoS may be incorporated into 802.11, which has failed to come up with specifications of its own in this area with any credibility. The 802.16a spec uses various physical layer (PHY) variants but the dominant one is a 256-point orthogonal frequency division multiplexed (OFDM) carrier technology, giving it greater range than WLANs, which are based on 64- point OFDM.

Another key difference of 802.16 is its use of time slots, allowing greater spectral efficiency for quality of service capabilities.

Margaret Labrecque, president of WiMAX, said that vendor collaboration on mass market products will achieve similar economies of scale to those seen in Wi-Fi WLAN devices, and

a far lower cost alternative to wired broadband, or T1 circuits in enterprise sites. Systems based on the mobile version of the standard, which should ship towards the end of

next year, about six months after fixed wireless products, will be able to achieve long distance wireless networking and will have far greater potential than Wi-Fi hotspots to provide ubiquitous coverage to rival that of the cellular network. Whether used directly or as backhaul for Wi-Fi, WiMAX fills the gaps in the hotspot system, and possibly enables it to challenge the cellular network as it cannot realistically do right now, whatever the hype says.

See the appendix for a full comparison of Wi-Fi and WiMAX.

Extended Wi-Fi

Some companies are still sticking with Wi-Fi rather than WiMAX as a metro area wireless standard. There are various approaches to extending Wi-Fi’s range and capacity, but all are based on proprietary extensions. Their supporters take the view that they can offer a solution now, particularly to the enterprise, but with the speed of development of WiMAX, this argument will not hold weight for very long.

There are many vendors that aim to work around Wi-Fi’s distance and capacity limitations and its weaknesses when operating in a point-to-multipoint or mesh mode – required to compete with broadband wireless access solutions. There is even likely to be an IEEE activity to create a standard for a meshing version of 802.11x. In theory, this could really shake up the hotspot infrastructure market, although all the arguments in favour of ‘mutant Wi-Fi’ centre on its availability now, giving operators a quick solution especially should WiMAX get delayed. But a mesh Wi-Fi standard will certainly take longer than WiMAX to hit the streets, especially if it fails to get a major vendor behind it.

Of the currently available solutions to extended Wi-Fi, Vivato is the most high profile. Although it has focused mainly on the enterprise with its wireless switching products, it has recently targeted operators with a 2.4GHz outdoor switch that boosts Wi-Fi using smart Of the currently available solutions to extended Wi-Fi, Vivato is the most high profile. Although it has focused mainly on the enterprise with its wireless switching products, it has recently targeted operators with a 2.4GHz outdoor switch that boosts Wi-Fi using smart

Some small operators are taking the Wi-Fi route too, in an effort to deploy fixed wireless rapidly. Broadband Central is accelerating its roadmap to offer broadband fixed wireless via 802.11x, expanding from its original 11 states to a further 11. The company sets up central Wi-Fi broadcast access point masts that give a one mile radius of Wi-Fi, and then set up customer locations with an antenna.

Other Wi-Fi extenders take the approach of fiddling with the media access control layer rather than directing beams in a more efficient way, Vivato’s approach and that of many BWA specialists too. Some of these have got prices down to less than initial WiMAX equipment is likely to be, around $300 per subscriber (though WiMAX, starting around $500, is sure to drop to this level rapidly). However, given that these are proprietary technologies from start-ups and still have some limitations compared to WiMAX, it seems unlikely that many operators will choose them rather than waiting 6-9 months for 802.16.

The most constructive approach is that Wi-Fi and WiMAX are strongest when working together however. Some mobile operators are looking at offering a single PCMCIA card for roaming between 802.11 and broadband services – Walker Wireless of New Zealand will offer one for IPWireless, but the big device makers will be developing cards for Wi- Fi/WiMAX, and of course, the debut of an Intel roaming card in the Centrino range will revolutionize the roaming hotspot user’s experience. In the end, the technologies will coexist in a creative way, with WiMAX increasingly the dominant partner, and the non-standard alternatives will fade into the background.

Figure 4: Performance of some common wireless technologies

Channel

Max data

Max Bps/Hz

20MHz 54Mbps 2.7

3.5, 7, 14MHz; 3, 6MHz

EDGE, (GPRS+)

200KHz 384Kbps 1.9

CDMA2000

1.25MHz 2Mbps 1.6

Cellular Technologies

The US Federal Communications Commission is freeing up more airwaves for metropolitan wireless networks by loosening restrictions on spectrum now held by Sprint, WorldCom, the Catholic Church and universities. Such moves threaten the asset value of the 3G carrier’s spectrum licenses, since potentially competitive services can now be run over unlicensed bands (although in the US, this is to forget that 25 percent of the cellular operators’ spectrum was given away free in the early 1990s).

The FCC's head Powell is staying neutral in the fight over whether to go all unlicensed, but is working to open up large chunks of spectrum for all comers. Inspired by the success of Wi-Fi, the FCC plans to open up a huge amount for unlicensed use, recently adding

255MHz to bring the unlicensed total to 664MHz. By comparison, the early version of Wi-Fi ran on just 83MHz. Europe is acting more slowly, but all territories will gradually take a similar direction and free up larger amounts of unlicensed spectrum, sacrificing licensing revenue for the government to the expected stimulus to business and the economy of better mobile communications.

WiMAX is a serious threat to 3G because of its broadband capabilities, distance capabilities and ability to support voice effectively with full QoS. This makes it an alternative to cellular in

a way that Wi-Fi can never be, so that while operators are integrating Wi-Fi into their offerings with some alacrity, looking to control both the licensed spectrum and the unlicensed hotspots, they will have more problems accommodating WiMAX. But as with Wi- Fi, it will be better for them to cannibalise their own networks than let independents do it for them, especially as economics and performance demands force them to incorporate IP into their systems. Handset makers such as Nokia will be banking on this as they develop smartphones that support WiMAX as well as 3G.

WiMAX can slash the single biggest cost of deployment: access charges for linking a hotspot to a local phone or cable network. A high frequency version of 802.16 would allow entrepreneurs to blast a narrow, data-rich beam between antennas miles apart – an idea that independents have tried before without success, for instance, Teligent and Winstar, which went bankrupt in the late 1990s.

A standards-based long distance technology will avoid many of the problems of high upfront costs, lack of roaming and unreliability that those ahead of their time pioneers encountered, but it will still need to gain market share rapidly before 3G takes an unassailable hold. Given the current slow progress of 3G, especially in Europe, and the unusually streamlined process of commercialising WiMAX, the carriers are indulging in wishful thinking when they say nothing can catch up with cellular.

Handoff project

In September, significant steps should be taken towards a standard that could turn the wireless communications industry on its head and assure the dominance of the WiMAX metro area standard.

This is the proposed Handoff Project of the IEEE, which was set in motion in March and which will hold its second major meeting on 8-9 September in Denver, Colorado.

The Handoff Executive Committee Study Group has a mandate to consider the viability of developing a standard for a common handoff framework for all 802 standards – WiMAX, Wi- Fi, short range technologies such as UWB – and also for IEEE wired networking standards.

The committee is headed by David Johnston, an Intel employee, Ajay Rajkumar from Lucent and Nokia’s Michael Williams – as usual, the leadership of the key groups indicates the vendors that are putting the greatest time and investment into the work and therefore see it as most critical to their strategies going forward. There will also be work on handoff between WiMAX and cellular networks, an area where Lucent has been a pioneer.

Such a standard, though in its very early stages and likely to take several years to come to fruition, would make all the arguments about different wireless standards irrelevant. Transmissions could be seamlessly passed between the most appropriate local, metro area Such a standard, though in its very early stages and likely to take several years to come to fruition, would make all the arguments about different wireless standards irrelevant. Transmissions could be seamlessly passed between the most appropriate local, metro area

Such a scenario will truly fulfil the promise that is currently enshrined in the far more limited roadmap towards 4G, the marriage of IP and cellular. Incorporate WiMAX into that mix too, and wireless communications could really become ubiquitous and robust for data and multimedia use.

The work would allow for devices with interfaces to multiple 802 networks to roam between them. Key issues to be addressed, according to the committee, are compatibility with other work on handoff, particularly the more basic projects on the Wi-Fi side, 802.11k and 802.11f; interworking with upper layer protocols, especially IPv6 and IPv4; and security.

At the first meeting in May, the main concern was defining the scope of the project, for instance, that work will focus only on the bottom two layers, the physical (PHY) and the medium access control (MAC). The September meeting will make big decisions on technological approaches such as how to build layer 2 constructs to reduce handoff latency and support real time applications; and

Also important is monitoring of handoff work in other standards groups, especially the Internet Engineering Taskforce’s WLAN projects, the 3GPP cellular body and other IEEE groups, particularly 802.11x; as well as work being done on layer 3 and above by the 3GPP and other bodies.

Johnson of Intel sees security as the biggest potential hurdle. “Security is a complex issue addressed elsewhere (linksec, 802.1x, 802.10, 802.11i, EAP). Trying to include security procedure in handoff specifications would hugely expand the scope and conflict with other groups,” he said. “But a handoff standard must not undermine security so the work should include validating that it is compatible with existing 802 security architectures.” The solution is likely to be to exclude security specifications from the standard but ensure that the final technology is compatible with other bodies’ security work.

Mobile-Fi

Standards battles are normally conducted in dusty committees and arouse little interest among technology purchasers until the vendors move the specifications into real products and real marketing wars. The IEEE’s wireless standards are proving an exception to this. The relative speed with which these standards are being ratified and commercialised and the intense public interest in Wi-Fi and its relatives mean that the various 802.xxx specifications of the usually shadowy IEEE are being thrust into the spotlight.

Perhaps the most key factor, though, is that the big vendors see, for the first time since the Internet boom, a genuine brand new source of revenue, and one at a sufficiently early stage that they stand a chance of stamping their control upon it. In the case of the youngest IEEE mobile standard, 802.20 or Mobile-Fi, however, some powerful names are feeling threatened rather than excited, which makes it probable that this particular specification will not be allowed to achieve the importance of its Wi-Fi and WiMAX cousins.

The big names are gathering behind two IEEE standards that, for all their claims of being complementary, are heading for a collision that involves more than bickering in technical committees, but could instead be the cover for a serious battle for influence over the The big names are gathering behind two IEEE standards that, for all their claims of being complementary, are heading for a collision that involves more than bickering in technical committees, but could instead be the cover for a serious battle for influence over the

But 802.20 has three critical weaknesses – WiMAX is starting to take on some of its remit; WiMAX has stronger and more aggressive support from key vendors; and the mobile operators, while relatively friendly towards 802.16, are hostile to 802.20.

802.20 technology

The stated mission of IEEE 802.20 is to develop a packet-based air interface optimised for transport of IP services, that will enable “worldwide deployment of affordable, ubiquitous, always-on and interoperable mobile broadband wireless access networks that meet the needs of business and residential markets”.

Broadband wireless services: Service provider

802.16e

Evolving from fixed wireless ISPs

802.20 Start-up wireless operator or evolving cellular operator 3G Cellular voice operator adding data support

Technology

802.16e

Extension to 802.16a MAC and PHY Optimised to integrate with fixed stations

Packet oriented Low latency

New PHY and MAC Optimised for packet data and smart antennas Optimised for full mobility at high speed

Packet oriented Low latency

3G W-CDMA or CDMA2000 Evolution of voice-optimised GSM and CDMA Circuit oriented, though evolving to packets on the downlink High latency data architecture

Spectrum

802.16e

Licensed bands between 2GHz and 6GHz

Licensed bands below 3.5GHz 3G Licensed bands below 2.7GHz

The metropolitan area 802.20 standard will operate in licensed bands below 3.5GHz and promises to support far more simultaneous users than cellular systems, with greater spectral efficiencies and lower latency. Mark Klerer, former chair of the 802.20 working group and an executive director at Flarion, the standard’s main technical contributor, said Mobile-Fi will The metropolitan area 802.20 standard will operate in licensed bands below 3.5GHz and promises to support far more simultaneous users than cellular systems, with greater spectral efficiencies and lower latency. Mark Klerer, former chair of the 802.20 working group and an executive director at Flarion, the standard’s main technical contributor, said Mobile-Fi will

As with Wi-Fi and WiMAX, Mobile-Fi follows the IEEE model of designing a new PHY (physical layer or layer 1 protocol) and MAC (media access control or layer 2 protocol) around the IP packet (layer 3). Cellular 3G technologies are also incorporating IP by retrofitting their technologies and looking to full IP integration with 4G, but they use a circuit- rather than packet-based approach. The circuit-based route involves high latency and poor reliability, which have forced 3G adaptations into cumbersome workarounds such as spoofing and translation, and a centralized network architecture that goes against the nature of distributed IP.

Two IEEE camps

This emerging standard – it will not be ratified until late 2004, if then - increasingly seems to

be positioned against the mobile version of WiMAX, 802.16e, which has strong interest from Nokia. Although the two come from different technical starting points and solve slightly different problems, the broadening remit of WiMAX threatens to make 802.20 redundant. Initially 802.16e was positioned as providing ‘lightly mobile’ support for users moving between fixed metro points. But its brief is expanding and early speculation that the two would be aligned to create a single umbrella specification now seems ill-founded.

Instead of the two camps coming together, as the IEEE itself would encourage, the big backers of 802.20, Motorola and Cisco, are getting restive and seem determined to try to put their preferred standard in a dominant position, improving their own place in the mobile market at the same time. Such an approach will be disastrous. WiMAX has a huge headstart on Mobile-Fi –even its ‘e’ version is at least a year ahead of its rival, and the industry support behind it is gathering pace rapidly. Also, it is a technology that can be accommodated relatively easily by the mobile operators.

By contrast, Mobile-Fi will be incorporated in products after WiMAX is already adopted – the standard will not be ratified until the end of 2004 - and it is seen as deeply threatening by the powerful cellular industry, with several 3G players having taken recent and possibly effective steps to squash it.

So why do these two groups not seek to work together on a broad specification for different types of mobile broadband wireless connections, rather than competing? The politics are symbolic of some of the most fundamental clashes going on in today’s technology business, with stakes massively high as vendors seek to create a new market for themselves after the buffeting of the recent recession.

So we have Intel ranged against Motorola in almost every area – in IEEE, in the UWB standards battle, and in the cellular world. Once at arm’s length from each other, the two chip giants have locked horns this year and are using every weapon, including the important one of standards processes, to try to be the alpha male in mobile communications. The contrasting financial results of the second quarter threw their current positions into painful So we have Intel ranged against Motorola in almost every area – in IEEE, in the UWB standards battle, and in the cellular world. Once at arm’s length from each other, the two chip giants have locked horns this year and are using every weapon, including the important one of standards processes, to try to be the alpha male in mobile communications. The contrasting financial results of the second quarter threw their current positions into painful

The other big names behind the two would-be standards are Nokia, on the WiMAX side, and Cisco, which backs Flarion, the key technology driver behind 802.20. Once again, we see an epic battle represented within the walls of the IEEE. The traditional enterprise networking supplier, moving rapidly into wireless and even smartphones, but finding itself threatened by rivals from the telecoms world; and the upstart, the handset maker daring to fancy itself as a vendor of enterprise mobile solutions and bringing its operator allies along for the ride.

Overlap with WiMAX

All these politics have polarized the IEEE projects this year. In March, the standards body ratified 802.16a, the non-line of sight, fixed wireless version of WiMAX, and kicked off the 802.20 process. At this stage, Intel and Nokia had only just decided to put their full weight behind WiMAX and both technologies were still obscure. They were positioned, quite realistically at the time, as complementary. WiMAX had come from a background of addressing last mile requirements using fixed wireless, while 802.20 was seeking to standardize various efforts to provide a fully mobile broadband solution using IP. Even the mobile variant of WiMAX, 802.16e, was still widely seen as an extension to a fixed wireless standard rather than a fully mobile standard in its own right.