Wireless broadband is on a fast track, finally. 3G services, a future consideration for so long, are now a rapidly expanding reality. And, if you believe Sprint's recent proclamation, 4G soon will be on the way. Also, fixed wireless and municipal Wi-Fi are fast spreading the wireless word. With UMTS, EV-DO, Mobile WiMAX and Wi-Fi, there's a technology flavor for every wireless broadband situation.

But as much as a quality wireless broadband experience is a function of robust access bandwidth, well-developed applications and cutting-edge devices, there is much more happening beyond the access realm at the network transport layer to enable that quality experience.

Regardless of whatever generation the radio access network has advanced to, the wireless broadband experience is only as good as the backhaul technology that supports it, and if backhaul bandwidth is limited or inefficient, then customers will not benefit from what 2.5G, 3G or 4G services have to offer. For wireless service providers eyeing innovative new applications like music and video as the answers to ongoing revenue challenges, encountering a bottleneck as traffic is backhauled through the network can be devastating.

“All of the ones and zeros in the air have to come back down to the ground somehow,” said Ted Shields, president and CEO of engineering and market research firm GeoResults. According to Shields, there are 140,000 cellular tower sites in the U.S., and the number of sites nationwide is growing about 6% each year. According to various other sources, more than 90% of these towers are fed with backhaul based on traditional, copper-based TDM infrastructure. Only about 6% of the towers in the U.S. are fed with fiber-based backhaul.

Traditionally, TDM infrastructure has provided suitable bandwidth for most mobile carriers' backhaul needs. In most cases, mobile carriers have used TDM-based T-1s circuits to backhaul traffic from base stations at the edge of the network. However, these leased lines have come at considerable expense, costing at least several hundred dollars per line and representing about 30% or more of the mobile carrier's bottom-line expense budget, according to many industry experts. In its research, GeoResults assumed an average T-1 line cost of about $00 per month.

“TDM for cellular backhaul is still growing, but that is really the most expensive way of providing it,” said Eitan Schwartz, vice president at RAD Data Communications USA.

“T-1s are outrageously expensive to lease,” said Michael Arden, principal analyst at ABI Research. “With Ethernet, that expense will be a lot less.”

The revenue that ILECs realized from providing backhaul amounted to about $10 billion in 2005 and could be $18 billion by 2011, Arden said. Shields, of GeoResults, said that in the next few years alone, the market in total could be worth $40 billion.