As part of the deal, BCE will be Clearwire’s exclusive partner for VoIP and certain other IP services in the US. BCE’s chief executive Michael Sabia will also join Clearwire’s board.

Kirkland, Washington-based Clearwire is headed up by the telecom industry pioneer Craig McCaw, who founded McCaw Cellular, which later became AT&T Wireless Service, and was acquired in February 2004 by Cingular Wireless for $41bn.

Clearwire is principally known as a telecom operator, but it has been receiving a lot of attention for its innovative wireless broadband service, which delivers internet access through a modem box plugged into an electrical socket in a home. The service can transmit voice and data at speeds comparable to DSL and cable, and requires no fiber-optic cables or copper wires, making it ideal for communities that don’t have high-speed internet access.

The technology is an early version of WiMax, a standard that promises to deliver internet access to large areas, in contrast to the shorter-range Wi-Fi access found in coffeehouses, offices, homes, and other locations.

Clearwire’s decision to roll out an internet phone service mimics a number of other start-ups such as Vonage, as well as larger players like America Online, which earlier this week announced plans to launch a VoIP service within a month.

This latest investment in Clearwire brings the total raised by it to more than $300m. Previous investors include DCM-Doll Capital Management, Enterasys Networks, Globespan Capital Partners, and Star Ventures.

Clearwire is expected to use the new financing to further expand its company’s network across new US cities. It is already in four US markets and expects to be in about 20 US cities by the end of the year.