According to Jefferies analyst George Notter, "2012 could be the first year in recent memory where all of the major wireless operators in North America are all spending aggressively at the same time.”

As you might well guess, service providers are cautious about capital investment in fixed networks, in larger part because the financial return is unclear to possibly negative.

North American capex is expected to grow 7.3 percent in the aggregate for 2012, but  wireline spending is expected to decline 5.8 percent year over year, while wireless spending grows 20.6 percent,  Notter said.

Investment ideally is directly related to expectations about potential financial return. If so, U.S. telcos expect greater returns from wireless service than from fixed networks. Despite the fact that cost per potential user is far lower for a wireless network than for a fixed network, investment in mobile assets has climbed since 1996.

In 2011, the wireline industry invested nearly $27 billion and, from 1996 through2011, it invested approximately $640 billion. In total, U.S. telcos and cable companies have invested about $1.1 trillion, according to the USTA.

The wireless segment of the business therefore was responsible for about $460 billion over the same period. In 2011 total service provider capital investment was about $66 billion, according to the U.S. Telecom Association (News - Alert).

The USTA data shows that cable companies made 19 percent of the investments, while telcos invested about 41 percent of capex in fixed networks and about 40 percent in wireless networks. But investment in fixed networks has dropped dramatically from the peak years of the telecom and Internet bubble in the years leading up to, and including 2000.

Those investment trends are no accident. By some estimates, including those of the International Telecommunications Union, global mobile revenue is about 4.5 times bigger than fixed network revenue, and it has been that way for several years. In a literal sense, the global telecommunications business has become a largely mobile business, with some important fixed line applications and revenue sources.