On a conference call Tuesday, Gerard Hallaren of TownHall Investment Research said the carrier is investing disproportionately in its wired network even as its wireless service lags behind other carriers. AT&T would have to invest an additional US$5 billion to bring its cellular service up to the level of its biggest competitor, Verizon Wireless, Hallaren said.

Figures on wireless investment between 2006 and September 2009 show the difference between the carriers, according to TownHall: AT&T made $21.6 billion in capital expenditures on its wireless network, compared with $25.4 billion for Verizon, Hallaren said. That worked out to $308 per subscriber for AT&T, well below the $353 spent by Verizon, he said. This shortfall is reflected in poor results for AT&T on some measures, such as reliability, in studies by Consumer Reports and PC World, according to TownHall.

AT&T said the capital expense figures on which TownHall based its analysis paint an incomplete picture of the carrier's commitments to wireless. Counting spectrum purchases and acquisitions along with network capital expenses, AT&T invested about US$19 billion in its wireless infrastructure just in 2008 and the first three months of 2009, said company spokeswoman McCall Butler.

In addition, the carrier disputed Hallaren's interpretation of its reported investments in wired and wireless networks. Using regulatory filings by AT&T, Hallaren said wireless services contribute 57 percent of AT&T's operating income but the company only makes 34 percent of its capital investments in that network. The wired side of the business, including the emerging U-Verse fast broadband and video service, takes up 65 percent of the carrier's network capital expenditure but contributes only 35 percent of its operating income, according to TownHall.

Those figures ignore significant investments by AT&T in its backhaul network, the wired links that carry the fast-growing traffic from the wireless network onto faster wired infrastructure and the Internet.