Two things beloved by San Francisco resident Galen Pewtherer just couldn't get along: his Edwardian-style house and wireless Internet access.

In 2008, Mr. Pewtherer tried to replace his old-fashioned cable Internet connection with a Wi-Fi network that he could share with other tenants in his building. "It turned out to be impossible," says the 38-year-old program manager at Cisco Systems Inc. "We couldn't get signal in or out of one room."

That...