A Silicon Valley startup re-ignited plans to offer free wireless Internet service in San Francisco, rekindling failed attempts by Google Inc. and Earthlink Inc., the company said Friday.

Wireless networking startup Meraki Networks Inc. plans to deliver the ambitious project by the end of the year by convincing San Francisco residents to set up free radio repeaters on their rooftops and in their homes. The wireless internet will be supported by advertising.

Since starting its tests about six months ago, Meraki has given away about 500 repeaters which are enough to provide high-speed wireless, or Wi-Fi, access to about 40,000 people in San Francisco neighborhoods covering an estimated 2-square-mile area.

The company raised an extra $20 million from venture capitalists which it said is now enough money to set up free Wi-Fi in San Francisco's remaining 47 square miles.

Meraki said it will deliver download speeds of 1 megabit per second, which is three times as fast as the speed for free access proposed in the city's original plan.

San Francisco Mayor Gavin Newsom says he will back Meraki's plans to expand in the city. His spokesman Nathan Ballard said in a statement the company will publicize and grow the network without the bureaucracy and politics that challenged our last effort to bring free Wi-Fi to San Francisco.

Newsom has been pushing for three years for citywide Wi-Fi, he added.

An earlier attempt was made by search engine giant Google and EarthLink to offer free city-wide Wi-Fi access in San Francisco but failed after EarthLink pulled out. The two had planned to install transmitters on street poles and other public property which was an expensive approach and involved more bureaucratic red tape.