Something is stirring in the radio airwaves above towns and cities in America, Europe and Asia.

Hundreds of local communities, municipalities and city councils are deploying broadband radio networks based on the 802.11 or ‘Wi-Fi’ radio standard using ‘mesh’ technology to link together multiple Wi-Fi cell sites or ‘hot-spots’.

“It is early days, but this is a growing business,” says Mark Whitton, general manager of Nortel’s wireless Lan (local area network) operations. Ron Sege, chief executive of California-based Tropos Networks, the leading Wi-Fi mesh network infrastructure provider, agrees. “Our business is growing quickly across the board,” he says.

Tropos is one of a handful of private startups that have pioneered the emerging market for Wi-Fi mesh systems. These new large scale Wi-Fi mesh networks - dubbed ‘muni,’ ‘metro’ or ‘urban’ networks - are another factor helping to reshape the world’s telecommunications markets. Proponents argue that in many situations where it is difficult or impossible to rollout hard wired broadband networks, the economics of Wi-Fi mesh networks are compelling.

In the US, nearly 50 municipalities were already offering metro-scale broadband wireless by last autumn and the number is growing rapidly. According to some estimates, up to 750 towns and cities across the US plan to provide their citizens with wireless broadband access by the end of next year.

Many of these towns and cities are deploying municipal Wi-Fi mesh networks in order to provide their citizens with reliable, low cost broadband access, others like San Mateo in California and Oklahoma City have deployed networks in order to improve communications for emergency service crews.

Where Wi-Fi mesh networks have already been deployed, subscriber take-up rates have generally exceeded expectations and most city managers report they are pleased with the results.

While most early deployments have been in relatively small towns such as Chaska, a small town south of Minneapolis with a population of just 18,000 (see story below), the latest batch of cities to announce plans to deploy Wi-Fi mesh networks include giants such as New York, Boston and Chicago.

Almost without exception, proponents of muni Wi-Fi mesh networks see them as complementing rather than replacing traditional communications technologies.

They have however, met with fierce resistance in some US markets from established mobile carriers. In Philadelphia, for example, the city’s plans to spend $10m rolling out a Wi-Fi mesh network to cover a 135-square mile area have been roundly condemned by Verizon Communications, the nation’s biggest telecommunications group.

Concerned about the potential impact on their broadband operations, the telecommunications and cable industries helped push through a Pennsylvania state law late last year that could prevent cities in the state deploying their own high-speed networks. The bill, which specifically exempted Philadelphia, has prompted similar legislation in at least 11 other states.

These bills have outraged municipal Wi-Fi proponents, who argue that cities must retain the right to enter the market in order to ensure ubiquitous cheap broadband access for their citizens. At a time when US regulators and legislators are growing increasingly concerned that the US could be falling behind Asia and Europe in broadband penetration, analysts suggest it is unlikely that Washington will intervene to stop cities such as Philadelphia providing alternative, affordable broadband.

While cable and DSL providers typically charge between $30 and $45 a month for broadband access, Philadelphia is expected to charge subscribers $20 a month or less. Outside the US, big cities ranging from Taipei, Taiwan’s capital, to Amsterdam have announced ambitious plans to build extensive Wi-Fi mesh networks and many other cities are building extended Wi-Fi ‘hot zones’ blanketing downtown areas or business districts with Wi-Fi radio coverage.

Taipei’s $70m project to build what could become the world’s largest Wi-Fi mesh network is perhaps the most ambitious incorporating about 10,000 wireless access points and covering an area of about 272 square kilometers where 90 per cent of the city’s 2.65m population lives.

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IDC, the market research firm, argued in a recent report on mesh networking in Western Europe that wireless mesh networking will be, “the next step in Wi-Fi development”. The research firm noted that, “because mesh networks are quick and easy to deploy and, more importantly, significantly reduce the need for wiring the backbone, wireless mesh architectures can have a positive impact on extending the reach of Wi-Fi zones”.

However IDC also added that while there are already a number of wireless mesh deployments in the US, “European interest in mesh topology for creating large wireless networks has just started to take off and most deployments are still in their early stages”. In Europe, where Alcatel, the French telecommunications equipment group has formed a partnership with BelAir, Wi-Fi mesh networking is currently mainly used in metropolitan areas where it serves as either an alternative for broadband services to end users or is used to create local government networks. Only four of the existing mesh networks in Europe provide public wireless access services.

Meanwhile although IDC says established hotspot providers have yet to announce publicly the usage of mesh for creating large-scale hot-spots, it is likely that operators have already started to look at this option.

Wireless mesh architectures are also useful for large enterprises, corporate or academic campuses. In areas that are more difficult to wire, mesh provides advantages in extending wireless coverage, says Martine Lapeer, chief technology officer of Alcatel’s Mobile Communications division. “It is a good niche product,” she says but agrees with others that it is not a serious rival to cellular networks, not least because voice over Wi-Fi is unlikely to be able to offer the same quality of service guarantees.

“Over time, mesh nodes will be integrated within the wired as well as traditional Wi-Fi networks,” predicts IDC. “Nortel for example, has already positioned mesh as an extension to its existing W-Lan (Wireless Local Area Network) product portfolio. In addition, switch vendor Trapeze Networks has revealed plans to use its management system for integrating mesh solutions into traditional W-Lan and Lan networks.” To date the market for Wi-Fi mesh network infrastructure has been dominated by a handful of startups including Tropos, BelAir and California-based Fireside.

Other companies including Pronto Networks provide gateway and service software for Wi-Fi systems. Although wireless mesh is now mainly offered by start-up companies, IDC expects established network vendors to follow Nortel and Motorola and announce their own mesh solutions, or co-operate with one of the mesh start-ups in the near future.

Meanwhile, other companies such as Santa Clara-based Azaire Networks make it easier for mobile operators to deploy ‘converged’ networks combining multiple IP access technologies. “Hybrid networks combining technologies including Wi-Fi and cellular are the way forward,” says Bill Howe, Azaire’s chief executive.

He believes that the market will eventually evolve to the point where the most appropriate radio technology will be used for the task at hand and points to the emergence of dual-mode Wi-Fi/Cellular handsets as evidence of this trend.

“Over time, mesh networks will be integrated with wired as well as traditional Wi-Fi networks,” argued the IDC report. In the meantime, interest is growing in the next member of the wireless radio standard family - WiMax, the emerging wireless technology that aims to deliver broadband connectivity over large geographic areas.

Initially most experts believe WiMax will be used to provide high capacity ‘backhaul’ services to Wi-Fi hotspots and mesh networks. But most Wi-Fi mesh network infrastructure vendors are preparing to offer WiMax as an alternative mesh radio carrier - a move that could eventually drive down the cost of mesh networking while extending both their range and capacity.