PacketHop kills access-points model of wireless network

By John Cox
Network World, 08/22/05

Software that creates a wireless mesh network with the need for conventional access points will be launched next month by start-up PacketHop.

TrueMesh software works on Windows XP and allows laptops and tablets to create an instant wireless network that dynamically routes data among the computers forming the mesh. It's as if each wireless device incorporated its own wireless LAN access point.

The company has been working on the product for nearly three years. One addition has been to create a public-key infrastructure for managing digital certificates among mobile clients that might be constantly moving and reconnecting.

PacketHop also created a public-safety collaboration application, a management console, and a software gateway that links remote PacketHop mesh networks over conventional WANs.

NICs based on 802.11 can communicate directly in what's called ad hoc mode, though typically wireless LAN clients communicate by connecting to an access point that is wired to a nearby Ethernet switch.

Several companies have introduced fixed access points that have two or more radios and routing algorithms to create an outdoor wireless mesh. These companies include BelAir, Nortel, Strix, and Tropos. Firetide and Strix have access points that can create an indoor mesh.

But PacketHop seems to be unique in creating what it terms a mobile mesh, which forms and reforms as wireless notebooks and tablets come within range of each other. These clients can also connect to any fixed conventional wireless LAN access point.

That means that police, fire and emergency crews are able to create an instant wireless network at any location. As more laptops and tablets are brought to the scene, the mesh algorithms can create more routes for video streams, text messages, and photos.

To maximize distances, PacketHop recommends the use of high-powered radio cards. Typically, these cards run at 30 to 50 milliwatts, but some cards run at 100 milliwatts or more.

A recent police department pilot also made use of directional antennas and a radio amplifier, both mounted in the squad cards. PacketHop executives say the higher-power 11b/g cards have a range of 1,000 to 2,000 feet, compared to typical indoor WLAN ranges of around 300 feet. In the pilot, the special antenna and amplifier boosted the range to nearly a mile.

Throughput in 802.11 networks drops in steps as the radios get farther apart. It declines as mesh clients route, or hop, through several radios to send or receive a message. PacketHop says its algorithms optimise throughput, so that after four or five hops, the throughput loss stabilizes at about 60 percent to 70 percent of what it was at the outset. Maximum throughput for the increasing popular 11g NICs is about 20 to 23Mbits/s, so users can expect something in the mid to high teens for a mesh with more than four or five hops.

The PacketHop software is expected to ship in September: Each client costs about $2,000; the management console with gateway software costs $25,000.

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