Verizon Wireless on Thursday attributed recent service disruptions on its 4G LTE network to "growing pains" associated with building out an advanced network.
"Being a pioneer comes with growing pains," Verizon said in a statement. "The recent issues that affected our customers' 4GLTE service were unforeseen despite careful, diligent planning, deployment and ongoing upgrade programs."
Verizon's network has experienced three separate disruptions this month: on Dec. 7; Dec. 21; and again on Wednesday.
During those incidents, Verizon said it "proactively moved" customers from 4G LTE to 3G, though for a brief period on Wednesday, "4GLTE customers could not connect to the 3G Network as quickly as we would have liked."
What happened? "Each incident has been different from a technical standpoint," Verizon said. "Our engineers have successfully diagnosed those past triggering events, and they have not re-occurred."
Verizon's statement did not go into full detail, but in an interview with GigaOm, Mike Haberman, vice president of network engineering for Verizon Wireless, said the problems were associated with something known as the IP Multimedia Subsystem (IMS), or Verizon's service delivery core.
As GigaOm explained, IMS has been in use for years, but Verizon is the first to use it for a 4G LTE network. That has produced some problems, like the widespread outage that hit the company's network back in April. This time around, there were three separate incidents.
"The first outage on Dec. 7 was caused by the failure of a back-up communications database," GigaOm reported. "The second, last week, was the result of an IMS element not responding properly, while Wednesday's outage was caused by two IMS elements not communicating properly."
Essentially, some phones just kept trying to sign in to 4G without success until Verizon forced them to drop down to 3G.
Verizon said it is taking a number of steps to prevent similar outages in the future. That includes: "geographic segmentation, which enables us to isolate, contain and rectify network performance issues, and maintain service to the majority of customers when an issue does develop; and software fixes that we have developed, tested and applied regularly—and will continue to do so. Both will improve performance and reliability."
"We will not rest until our 4GLTE network performs at the very highest levels that our customers have come to expect from us," the company concluded.
The trouble comes several weeks after Verizon celebrated the one-year anniversary of its 4G LTE network. The service is now available in 190 markets, up from 38 at launch. PCMag gave the network high praise during our 2011 Fastest Mobile Networks test: "We found that Verizon's new 4G LTE network is much faster than other mobile Web options, with speeds that often exceed home Internet connections," PCMag analysts concluded.
To boost that network, Verizon has made a number of spectrum purchases in recent weeks, including PCS and AWS spectrum in various U.S. markets from Leap Wireless for $188 million. Leap in turn bought 12 MHz of 700 MHz A block spectrum in Chicago from Verizon Wireless for $204 million.
That came days after Verizon paid three of the nation's top three cable companies $3.6 billion for 122 spectrum licenses in the AWS band. As part of the deal, Comcast will get $2.3 billion for the spectrum, Time Warner will get $1.1 billion, and Bright House will get $189 million.
More recently, meanwhile, Cox agreed to sell its 20-MHz spectrum licenses to Verizon for $315 million as part of a deal to resell each other's services.
For more, see "What is LTE?" from PCMag's sister site ExtremeTech.com.