Mobile broadband penetration now reaches one-quarter (25%) of all U.S. households; primarily with cell phones, Smartphones and other hand-held wireless devices according to a recent survey by research firm TNS.

Rather than replacing fixed line broadband (DSL and cable), the survey of 120,000 American households finds a significant overlap in the penetrations of fixed and mobile broadband technologies.

TNS says that in the 67% of households that already have fixed broadband, 29% also have mobile broadband, compared to 25% across the nation as a whole. In other words, households that already have a DSL or cable connection in their home are more likely to subscribe to a mobile broadband than households that don't subscribe to cable or DSL broadband.

Not surprisingly, researchers have found that households with both services have higher incomes, are more likely to be married with children, and spend the most on telecommunications. Households with only mobile broadband access tend to be younger, full or part-time students and are more budget conscious.

This suggests that homes with a fixed broadband connection have greater disposable income and therefore can afford to layer on a mobile broadband connection.

Discuss in Digital Home's Landline and High Speed Internet Forum .