Relationship With Other Wireless Technologies

Wireless Technologies
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 serious investments and it will be a different kind of business, so we don't really need to identify the separate amendments." 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 antennas and proprietary enhancement technology to operate over WiMAX-class distances, around 50km, though only at Wi-Fi speeds and in point-to-point mode.

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.

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