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A Bluetooth network topology with class

Technology startup Intransit Networks (Seattle, WA) is going after the mobile asset tracking market. They will combine off-the shelf radio frequency ID tags, Bluetooth radios, wireless Internet connections via public carriers, and their proprietary software to help enterprises keep track of high-value assets.

Technology they have under development and under patent includes a technique for "geo-fencing" of low power radios (such as Bluetooth) to detect assets being stolen, step-power filtering to enhance battery life of low power radios, and a technique for tracking the orientation of assets to support 3-D graphical displays of the current position of a collection of assets. Perhaps the most innovative element of the Intransit approach is the use of so-called "Class-Switched Networks."

The best way to describe a class-switched network is to first describe what it is not. Bluetooth radio networks form based on physical proximity, as do ad-hoc networks under the IEEE 802.11 standard. A node looking for a home transmits a signal looking for authorization from another node close enough to establish a connection. Bluetooth nodes have the additional capacity to seek specific services that may (or may not) be available on any in-range node.

Class-switched networks go one step further with a "service search" technique. In addition to supporting the specific services in the Bluetooth standard, each node in a Class-switched network also has a designated class. As Intransit explains their architecture, each class forms an intranet, reducing overall network traffic by isolating nodes from irrelevant packets. In a manufacturing environment, for example, one could envision a "RawMaterials" class, a "WorkInProcess" class, a "FinishedGoods" class, and so on.

Bluetooth nodes in such a network only connect with other nodes in their class or a node of class "Master." This Master class routes data between the other classes and has the ability to connect to the Internet. The communication channel available to a Master class node can range from a low-bandwidth cellular phone to a DSL line or better.

An administrator can change the class of each node based on business process needs without physically changing the network node. A node embedded in a returnable shipping container, for example, can change from class "InTransit" to "QAHold" to "WorkInProcess" to "retail floor" as it moves through a supply chain.

While the discussion of Class-switched networks currently centers around Bluetooth infrastructure, the architecture works on any radio backbone that supports ad-hoc (peer-to-peer) networks. For example, Bluetooth may work fine to track tools, components, and pallets indoors, but the range and bandwidth probably cannot support a cargo transfer yard where intermodal shipping containers need to communicate their entire contents and the area to be covered is measured in acres. Such an environment might work perfectly well with 802.11 radios operating in ad-hoc mode.

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This was last published in April 2001

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