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Routing Breakthrough Promises Larger Wireless Nets

The Wi-Fi revolution increasingly depends on ad hoc mesh networks to provide smooth connectivity to nodes in motion. Currently, these handy devices only achieve connectivity within a "bubble" established by a centralized RF transmitter. Ad hoc networking would extend that fixed coverage by allowing transmissions to hop from one device to another until a centralized RF node is reached. But they require a complex routing algorithm that adds overhead.

A new wireless-network-routing approach, based on a method called high-speed path propagation (HSPP), posits a solution to those scaling problems. In the approach, devised at Order One Networks Inc. (Toronto), the network overhead associated with routing and addressing does not mushroom as the number of nodes increases. That opens up the possibility for indefinitely large networks.

"The dirty little secret of ad hoc networking is that you can't scale beyond a thousand nodes," said David Davies, a partner with the company. The problem occurs with virtually all current routing protocols for wireless networks.

The reason is the need for a node to query the entire network before it sends a message to some other node. Called flooding, that operation becomes more cumbersome as the number of nodes in the network increases.

Ad hoc networks are used for mobile wireless applications where no fixed network infrastructure exists. Data hops from a source node to neighbors within range; those nodes then forward the data to their neighbors. Since the network topology is constantly changing, establishing a path requires a node to know the location of all nodes in the network, resulting in flooding. But that operation places a large administrative overhead on the nodes that is particularly burdensome for battery-powered mobile devices.

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