AT&T isn't alone in making big spending bets on the smartphone and its spending plans may force competitors to quicken costly network upgrades.

On Wednesday, Sprint, which has seen its finances revitalized by an October merger announcement with Softbank of Japan said it will buy U.S. Cellular's Midwest assets, in a deal that is evidence of the company's improved industry standing.

Already, Sprint is now seen as having the finances to complete a wireless network upgrade -- called Network Vision -- and use heavily subsidized unlimited iPhone data plans to draw in users, in two smartphone market bets that once had analysts handicapping the company's bankruptcy.

Quietly, as the telecom industry has consolidated in a string of deals that makes Sprint and MetroPCS-TMobile better competitors to AT&T and Verizon, while tower operators such as American Tower ( AMT), SBA Communications ( SBAC) and Crown Castle ( CCI) have also been buying up assets to serve growing wireless networks.

AT&T's spending plans may have a windfall on tower operators, says Piper Jaffray analyst Christopher Larsen. "Today's announcement translates to more cell sites... The installations will leverage fiber connections to the towers, which is good for fiber- based players," writes Larsen in a note to clients that highlights American Tower, SBA Communications and Crown Castle as beneficiaries.

All told, AT&T's spending signals that money is still gushing into the wireless market as a swath of industries brace for continued consumer demand for smartphones, tablets and other mobile devices.

While AT&T's plans may tip forecasts of infrastructure spending positive -- averting a cliff that may hit other sectors - there's good reason to expect other large carriers will plow billions more into wireless and fiber networks, in coming years.

See why Dish Network's Earnings Revive DirecTV Deal Talk.

-- Written by Antoine Gara in New York

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