Meshed Roofnets


Technology Review has a story on MIT’s Roofnet, a mesh networking project creating self-organizing wireless networks with cheap Linux computers and Wi-Fi cards.

Each computer and roof-mounted antenna at students’ apartments and MIT buildings is a node on the network (map). The interconnection topology is constantly changing. “We want to understand how a whole bunch of computers with short-range radios can self-configure a network, forming order out of chaos,” says computer science professor Robert Morris, who coordinates the project.

The network has now more than 30 nodes in a 4-square kilometer area surrounding the MIT campus. “We hope to reach a hundred nodes within a few months,” he says.

Each Roofnet node uses an 802.11b wireless networking card installed on a cheap PC running Linux and the routing software. A coaxial cable connects the wireless card to an omnidirectional antenna. The user then connects the PC to the Roofnet node. The total cost of the equipment for each node is $685.

Research groups at universities such as Carnegie Mellon, Rice, UCLA, and the University of Illinois at Urbana-Champaign, and at companies such as Nokia, Intel, and Microsoft are developing similar mesh systems.

Community-owned wireless networks in New York, San Francisco, Seattle, London, and other cities usually use DSL for their backbone. Mesh networks like Roofnet might provide an alternative, perhaps in combination with “last mile” wireless backbones like 802.16a.

Mesh networking has been around for a while. Nokia abandoned their Rooftop Wireless. Other mesh networking approaches include:

  • LocustWorld has had moderate success across the UK. For a while in 2002, there was discussion that mesh networks could pose a threat to the future of 3G technology.

    FastLine (FAQ), is reportedly the first ISP to use Mesh networking in the United States. They use MeshAP from LocustWorld. A rural town of 4,500 people, is served, according to the Shrevport Times.

  • Half Moon Bay, near San Francisco, has deployed 8 to 10 Wi-Fi hot spots using Tropos network. Two of the hot spots have land-line connections to carry the data to the Internet backbone, the rest use mesh-like interconnections.

    The Intel-funded Tropos 5110 is a mesh-based Wi-Fi network for outdoor installations. It can be mounted on external structures such as buildings or lampposts and is used for citywide police data communications and wireless public access.

Mesh networking may be particularly well suited where multiple portable devices are interconnected. The connected soldier could use low power UWB, for example, and hop through multiple handhelds before reaching a backbone connection.

Although no mesh networking was used, a Wireless Caravan cruised down the West Coast earlier this year. They used EPIA M-Series boards from VIA Technologies. While travelling at highway speeds, the servers streamed music via Icecast, provided anonymous FTP uploads and downloads, as well as IRC, Jabber and other communication services between the cars.

Portland has roughly 130,000 miles of unused (dark) fiber optic cable between it and Seattle, most of which was laid by telcom providers who went out of business and no longer own it. Perhaps an AP every ten miles could be relayed through mesh networks on light poles every 1/2 mile or so. Directional antennas could send 5.8 Ghz & 5.9 Ghz (Intelligent Transporation System) down a linear roadway. Handy for tracking cargo, too.

Get Homeland Security to pay for it – they’ll fund anything.

Fleishman & Higgins on WDS


Glenn Fleishman has an article on Wireless Distribution Systems on O’Reilly’s Wireless DevCenter. Wireless bridging connects two Access Points together, point to point (or multipoint).

Products like the Linksys’ WGA54G Wireless-G Game Adapter and WET 54G Wireless Ethernet Adapter provide wireless bridging to games and computers. Proxim’s Tsunami MP.11 ($300) provides similar bridging for the “last mile”. Bridging does not integrate local Wi-Fi access. It just provides a point-to-point link.

Wireless repeaters combines an AP with backhaul, sharing the same WiFi channel for both local access and the backhaul link. WDS coordinates activities in a “standardized” way. Except there’s really no standard.

I’m still confused why the backhaul doesn’t interfere with local access. I guess it’s a matter of time-sharing, where multiple boxes act like one big Access Point. Maybe someone can clear that up for me.

Fleishman explains:

Wireless Distribution System (WDS) allows packets to pass from one wireless access point to another, just as if the access points were ports on a wired Ethernet switch. WDS bypasses the kind of magical kludgery that Linksys offered with its WET11 bridge or with the WAP11 in pairs or as a bridge/AP combination

The excitement about this technology comes from three factors: a WDS gateway can act as an AP and a bridge in a single box; WDS is standard, although interoperability isn’t being tested by manufacturers yet; and WDS is cheap, with Buffalo offering its WLA-G54 for as little as $100 street price. In the past, expensive enterprise devices either involved standalone bridges or pricey combined units that worked only with other proprietary gear.


You might want to use WDS in a variety of common scenarios that would otherwise require expensive or unnecessary Ethernet cabling. If you needed two access points to serve your house, for instance, and didn’t want to run Ethernet between them, WDS is an able substitute.

It’s also a cheaper and simpler way to provide blanket coverage. Attach some sectorized antennas on opposite ends of an open courtyard or park and use WDS to avoid having to put a backbone between the two units.

WDS-enabled access points broadcast MAC messages across all connected nodes allowing all clients to see all adapters on all connected wireless and wired networks.

Small Net Builder site may have the definitive explaination of WDS and wireless bridging and Wireless Distribution Systems.

Tim Higgins explains:

Wireless bridging, i.e. connecting two wired networks via a wireless link has gotten to be a very confusing subject. In this NTK, we’re going to try to untangle the mess that wireless networking companies have made of this product area, help you choose the right products for your application, and show you how to set them up properly.

Higgins also has indepth reviews of WDS-enabled products such as the Buffalo AirStation (WBRG54) ($118), Buffalo’s Compact WLA2-G54 ($149), D-Link’s DWL-900AP+ and others.

Another contender for WDS might be Netgear’s single-band WGT624 108 Mbps Wireless Firewall Router. It uses Atheros 108Mbps 802.11g products and is slated to begin shipment next month at street pricing around $120 with a WDS upgrade planned in a month or two.

Intel + South Korea = WiMax


South Korea’s KT Corp. and Intel have agreed to cooperate in wireless telecommunications, digital home networking and broadband convergence network through joint marketing and research and development efforts.

The agreement was reached during Intel Chief Executive Craig Barrett’s visit to South Korea. Among the projects slated to be carried out at the research center include Ultra Wideband (UWB) and WiMax (802.16a), Intel said in a statement.

South Korea, a country of 48 million people, is the world leader in multi-user online games, helped by tens of thousands of PC salons where people can get affordable high-speed Internet access. About 65 percent of households have broadband. KT serves about half of them.

KT Corp. competes with Hanaro Telecom and Korea Thrunet for high speed access.

Wireless competition includes market leader SK Telecom with 17.86 million mobile subscribers, KT’s mobile unit, KTF, with 10.49 million and LG with 4.8 million subscribers. All three are looking to generate more sales from wireless data services and games.

KT, the largest fixed-line, high-speed Internet service carrier in Korea, was privatized last year with operating profits growing 43 percent this year. They recently announced a 50-megabits-per-second broadband service.

Korea is testing a variety of “4G” technologies. KT Corp and Hanaro Telecom are testing Navini’s Ripwave 2.3 GHz system. Intel is an investor in Navini.

South Korea is the most wired country on the planet, with cheap broadband access available almost everywhere. Unlimited broadband access starts at $25/month ( 16) for 2Mbps, 8Mbps costs around $34 ( 21) a month. More than 60 per cent of households have broadband access, and those without it can head down to one of the bangs found in every shopping mall and street.

Perhaps a $300, Korean-built Outdoor Access Point with a 802.16a backbone could reach subscribers too far for VDSL service. That would help CoMeta, too. A self-contained Pronto box might include a Navini/802.16a card for the backhaul with 802.11a/g for the local area.

Broadband leadership has moved to Korea. Intel must utilize their experience and expertise if it is to stay competitive.

Portable Playstation Specs


Although Playstation Portable, known formally as the PSP, won’t be available until the fourth quarter of 2004, it could shake up the handheld market. Specs include:

An LCD about 4.5 inches wide, with 480 x 272-dot resolution; a 60-mm-diameter disk system; and a proprietary Sony system called Universal Media Disc (UMD), all powered by the PSP engine consisting of two MIPS R4000 CPUs. WiFi is included as standard equipment.

The two processors operate in the range of 1 MHz to 333 MHz at 1.2 volts. Advanced Video Coding (H.264) was adopted as the video coding format for PSP. The 6-centimeter-diameter UMD system, has a 1.8-Gbyte capacity using a red laser and two-layered-disk structure, can store the equivalent of about two hours of video content that’s of the same quality as DVD images.

In a year, $200 DVD-quality wireless handhelds, similar to the Archos Multimedia handheld, will hit the streets. They’ll be hungry.

BTW, Microsoft may offer a wireless Xbox adapter this Christmas. It will compete with the Linksys’ WGA54G Wireless-G Game Adapter and similar products.

Further out, Sony plans a grid-connected “cell” console in 2005. IBM will make the processor and is currently taking supercomputing to the next level with the development of a chip capable of handling one trillion operations per second.

Intel Connects the Dots


EE Times has an interesting story on Intel’s wireless stategy to use CMOS.

In early May, Intel Corp.’s chief technology officer, Pat Gelsinger, offered his connect-the-dots vision of a wireless world with ubiquitous, seamless connectivity from network to network and from air interface to air interface. From Wi-Fi to cellular to ultrawideband, Gelsinger’s theoretical nomad could roam freely without ever enduring the inconvenience of a network disconnect.

Gelsinger’s vision rested on two radical underpinnings. The first was that the proposed wireless connectivity would essentially be free. The second was that Intel would be providing it. In vanilla CMOS.

That’s right. A 35-year-old PC-oriented processor company with no radio-frequency expertise was going to usurp RF behemoths like Philips, Motorola, Analog Devices, STMicroelectronics, Intersil’s wireless-LAN division (now a part of GlobespanVirata) and Broadcom, as well as specialists such as Atheros, Bermai, IceFyre and XtremeSpectrum.

Some have speculated that Gelsinger was still high on the March launch of Intel’s Centrino WLAN platform.

Ironically, Centrino doesn’t actually contain any Intel RF expertise per se: The radio comes from Philips and the baseband from Symbol Technologies. But that doesn’t bother Gelsinger, who claims ownership of all aspects of Centrino. “We own the product-which means we brought an awful lot of the RF expertise to make it a product, even though many of the core technologies come externally,” Gelsinger told EE Times.

Besides, the CTO is confident that the work currently under way at Intel Labs’ R&D division in Hillsboro, Ore., will substantiate his RF-in-CMOS predictions over the coming years, despite industry skepticism-primarily from RF incumbents-that borders on hysteria.

Gelsinger outlined how the building blocks were being put in place to realize the vision of what the company calls “Radio Free Intel.”

From the researchers’ point of view, their day of vindication came with the presentation of an all-digital-CMOS 10-GHz agile-RF frequency synthesizer at the 2003 Symposia on VLSI Technology and Circuits in Kyoto, Japan, in early June. The phase noise in this device, which is based on a 5-GHz CMOS voltage-controlled oscillator (VCO), was specified as -120 dBc at a 1-MHz offset. “That’s when the world stood up and took notice,” said Steve Pawlowski, an Intel Fellow who leads the Hillsboro R&D group along with Kevin Kahn, communications and interconnect labs director.

At one time, “If I was doing a 5-GHz radio with a 500-MHz CMOS process, that was next to impossible. Now I have a 5-GHz CMOS process.” Moore’s Law also provided the multiple gigaflops of processing power to enable such functions as software-defined radios with reconfigurable architectures and smart antennas, and the clout to do RF processing in CMOS.

Wireless talent had to be recruited, which became a bigger issue than anticipated. Many RF engineers perceived Intel as a PC company where their talents would be eclipsed by the success of the processor and computing group. No one had a reason to move-“especially not to the Pacific Northwest from San Diego and the Bay Area,” Pawlowski said. “When we first started, we looked for senior talent,” he said. “All told us that ‘CMOS isn’t the technology. You want III-V materials [silicon germanium, gallium arsenide and so on].”

So Pawlowski and Kahn turned to university professors. “We told them what we were doing and offered them research grants to work on it,” said Pawlowski. Intel also gave students the chance to come in-house and implement those designs that looked promising.

The idea worked out. “The results are much better than what we would have gotten had we gone looking for the best-and-brightest RF guy,” said Pawlowski. “The students were pretty fresh.”

The university grants continue, with Gelsinger’s group alone issuing 400 per year. Instead of acquiring startups, Gelsinger is sticking with a simpler strategy of funding research and dispersing dollars among companies devising technologies that could help in the dissemination of Wi-Fi. “I can give a research grant of $50,000 to five different researchers and have them solve my problems,” he said. “I now have five of the top people on the planet working for me for $250,000. If I buy one company I’ll have to at least spend a few million.”

Intel expects that Centrino–a bundle that includes a Pentium-M processor, a wireless chip and a chipset–will become more widespread. Especially as 90 nanometer process technology becomes mainstream and radio parts get integrated with the processor. Intel will come out with a Wi-Fi chip that can connect to 802.11a and 802.11b networks in the third quarter. A similar chip compatible with 802.11b and 802.11g technology is set to arrive in the fourth quarter.

Related Daily Wireless articles include Teresa Meng’s Journey, Meshing Around at Intel, Sensor Nets, Intel’s wireless plans, Intel Researching the Last Mile, Craig Barret on China, Berkeley’s Wireless Research Center and Behind the Curtain at Intel Labs.