4G Spurs Wireless Backhaul

Wireless backhaul of traffic from mobile towers to switching facilities has never been the preferred technology in the U.S. market, as popular as it has proven elsewhere. Instead, T1 lines have been the overwhelming favorite.  Obviously,  all that has to change when fourth-generation networks fire up and must backhaul hundreds of megabits per second worth of traffic rather than several megabits per second.

 

Sprint Nextel executives already have noted that backhaul facilities are slowing the deployment of new WiMAX networks in Washington, D.C. and Baltimore.

 

Much attention has therefore been devoted to Ethernet over fiber and Ethernet over copper as potential solutions. But radio suppliers are quite active as well, especially now that route diversity and protection is starting to be seen as more important.

 

Today, it would not be typical for every single tower to have a protection mechanism. More frequently, traffic is aggregated from a number of local towers and then backed up by some sort of ring or mesh at the aggregation point.

 

Clearwire, though, has been a major proponent of wireless backhaul, and Sprint also seems to be actively engaged in that approach as well. In fact, Clearwire CTO John Saw says the company can deploy its planned mobile WiMAX network in the U.S. for far less than traditional cellular deployments thanks to its work on microwave backhaul and the use of a flat-IP architecture throughout its network.

 

Recurring costs for backhaul facilities are where the savings are. Once the radio equipment is installed and running, the recurring cost is relatively mild, representing annual fees for microwave licenses. Non-licensed frequencies also can be used, but are not favored by service providers.

 

The key change is the amount of backhaul bandwidth. Instead of using T1 lines costing hundreds of dollars of month, the new 4G networks might need to buy optical facilities costing thousands of dollars a month. As pleasant a thought as that might be for access providers, it can seriously disrupt a wireless operator's business plan.

 

Right now, about 90 percent of Clearwire backhaul is provided by wireless links, the company says. In fact, Clearwire already operates what is probably the largest wireless backhaul network in the United States.

 

The operator runs the microwave links in licensed 18 GHz and 24 GHz bands, as well as some unlicensed 5.8 Ghz backhaul.

 

Historically, many service provider technologists and engineers have worried about microwave connections in terms of reliability, compared to copper or optical facilities. These days, though radio equipment is highly reliable, atmospheric conditions remain a concern. Proper engineering and more mesh-like networks can alleviate those concerns.

 

Clearwire already relies on wireless backhaul. And Sprint seems to be confident it also can build wireless backhaul networks with reliability and performance identical to wired SONET networks.

 

All of that might be important someday for other service providers, not simply end users. Wireless always has been the great hope for service providers who want an affordable mass market access alternative to the incumbent telephone company. WiMAX and LTE networks might just provide what contestants always have hoped for: a reliable, high-bandwidth and affordable way to bypass incumbent telco access loops.

 

If that happens, wireless backhaul will likely prove to be a key enabler.