VCs have invested several billion dollars in about two dozen WiMAX chip and network device makers and a small number of service providers led by Clearwire, perhaps the largest WiMAX carrier in the world based on subscriber count.

Clearwire, which has about 350,000 subscribers in the U.S., absorbed a whopping $1.25 billion in venture funding before going public in March 2007.

That spending spree was followed by a relative drought in the last year as the rapid emergence of cellular broadband and meshed WiFi caused VCs to hedge their bets.

While Clearwire aims for nationwide coverage in the U.S. and broad deployment in Europe, both DigitalBridge and Enforta possess slightly more modest aspirations.

Two-year-old DigitalBridge is targeting smaller towns that are underserved by DSL and cable modem access providers in a limited number of U.S. states, mostly in the midwestern United States.

"We consider ourselves part of the Sprint and Clearwire ecosystem so we will not build in any of the markets they are going into," said Kelley Dunne, CEO of DigitalBridge.

Sprint Nextel is in the early stages of deploying Xohm, its nationwide WiMAX network.

Sprint and Clearwire in July announced  a plan to combine their efforts and build a single nationwide WiMAX network, rather than two.

That deal was scuttled four months later, but analyst Tim Farrar, president of Telecom Media and Finance Associates, believes that the Sprint/Clearwire deal will be revisited.

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