Sprint Corp. (NYSE: S) isn't waiting for blanket 4G coverage in cities before switching on its new Long Term Evolution (LTE), instead aiming for street-level coverage that it deems useful for potential users.

4G on the street
Bob Azzi, senior vice president of Networks at Sprint, talked to Light Reading Mobile about the operator's LTE strategy Friday in the wake of its initial launch in 15 markets.

"We weren't planning to wait until we had all our cell sites covered," explained Azzi. Instead the cities went live "when we determined that we had a sufficient footprint that enough people could find it in enough places."

Azzi says Sprint uses LTE propagation tools to look at coverage before launch and doesn't "have a firm percentage" on how much of a market is covered before launch. "We focus on street-level coverage ... although it obviously has in-building coverage in there as well," Azzi says.

Rather than launch on a specific percentage, Azzi explains, the operator's teams look at whether the coverage available will "prove a useful enough experience for our customers for us to launch it."

This helps explain how the July 15 launch went from the initially announced five cities to 15. "We went from five to 15 quickly because we saw, 'Hey, these are ready.'"

It also explains how Sprint users in cities such as Atlanta and Houston aren't always finding the new 4G service. There are threads on Sprint User Forums searching for the 4G signals.

Sprint plans to quickly fill in the gaps in launched markets. "They'll find the LTE coverage in more and more places over the next several months," Azzi reassures.

In the meantime, Azzi says the operator's High Rate Packet Data (HRPD or eHRPD) handover mechanism between LTE and CDMA is working reliably on the operator's initial LTE smartphones.

Where next?
The Sprint network SVP won't say where exactly 4G services will be launched next. "We've got all sorts of candidates," he notes. "We won't stop until until we have a footprint that covers our CDMA cell sites."

The process is expected to be complete by the end of 2013.

The operator is on track to have 12 to 15 LTE devices on the market by the end of 2012. Azzi can't say if any of those gadgets will be a tablet.

Ericsson, Georgia & Texas style
Sprint has divided its LTE deployment among three suppliers: Alcatel-Lucent (NYSE: ALU), Ericsson AB (Nasdaq: ERIC) and Samsung Corp. The Swedish vendor is in all the initial 15 cities in Georgia and Texas.

"The first set of sites are from Ericsson," confirms Azzi. But, he adds, "there's nothing in particular to conclude from that. None of the suppliers are ahead or behind in the plan, if you will."

Azzi explains that the timing in getting the sites up and running has much to do with having the fiber backhaul in place in support of LTE, among other factors.

What's a market anyway?
Like other operators, Sprint bases the markets in which it deploys LTE on cellular maps defined by the Federal Communications Commission (FCC) , but not always strictly to the letter.

"We don't stick to it religiously, but we think that it's a good starting point," Azzi explains.

How fast is Sprint's LTE?
Sprint says it offers peak download speeds of 25 Mbit/s with averages of 6-to-8 Mbit/s. Uploads clock in at 2 to 3 Mbit/s. Speeds are "based on testing of deployed sites prior to launch," the operator says.

Map it!
See the LTE markets on the map below:


View Sprint 4G LTE Markets in a larger map

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— Dan Jones, Site Editor, Light Reading Mobile