Few things are more aggravating than having your cell phone signal drop out in the middle of a call. But, according to the J.D. Power and Associates 2010 U.S. Wireless Call Quality Performance Study -- Volume 2 -- it seems to be happening more.

The latest survey shows problem rates related to dropped calls have increased notably from six months ago among wireless customers who are most likely to switch providers.

Seven problem areas

The semiannual study measures wireless call quality, based on seven problem areas that impact overall carrier performance: dropped calls; static/interference; failed call connection on the first try; voice distortion; echoes; no immediate voicemail notification; and no immediate text message notification.

Call quality issues are measured as problems per 100 (PP100) calls, where a lower score reflects fewer problems and higher call quality. Performance was examined in six regions: Northeast; Mid-Atlantic; Southeast; North Central; Southwest; and West.

The study finds that 14 percent of customers say they "definitely will" or "probably will" switch wireless providers in the next 12 months and that these customers experience a particularly high rate of call-related problems. The rate of call quality problems among customers who say they "definitely will" switch their current wireless provider is more than four times higher than problem rates among customers who say they "definitely will not" switch in the next 12 months (29 PP100 vs. 7 PP100, respectively).

Why they switch

Specifically, dropped calls are primarily driving the high switching rate, compared with other call quality issues. For example, problem rates average 20 PP100 among customers who say they "definitely will" switch carriers within the next year and also say they had at least one dropped call. Furthermore, the rate of dropped call problems among customers who say they "definitely will" switch has increased by 33 percent from six months ago.

In comparison, among those wireless customers who experience calls that are not connected on the first try, the average problem rate is 11 PP100, up slightly from 10 PP100 six months ago.

"With an increasingly competitive environment and the complexity of services often used in conjunction with cell phones steadily on the rise, carriers that offer superior network quality may improve their likelihood of attracting new customers and increasing customer retention," said Kirk Parsons, senior director of wireless services at J.D. Power and Associates. "In fact, improving network quality and, in turn, retaining the customers most likely to switch are beneficial financial incentives for wireless carriers, as customers who are more likely to switch tend to spend an average of $82 per month and make or receive 127 calls per month, while those who aren't considering switching spend $78 and make or receive 104 calls per month, on average."

Regional rankings

For a 12th consecutive reporting period, Verizon Wireless ranks highest in both the Northeast and Mid-Atlantic regions. The company achieves fewer customer-reported problems with dropped calls, initial connections and interference, compared with the regional averages. Verizon Wireless also ranks highest in the West region and ranks highest in the Southeast region in a tie with both Sprint Nextel and T-Mobile.

In the North Central region, U.S. Cellular ranks highest for a 10th consecutive reporting period. Compared with the regional average, it has fewer customer-reported problems with dropped calls, failed initial connections, interference and echoes.

In the Southwest region, T-Mobile ranks highest, due mainly to lower reported PP100 ratings in voice-centric dimensions such as interference, echoes and voice distortion, compared with the regional averages.

"Wireless customers rely on their phones to do everything from providing them with driving directions to sending picture messages, as well as placing calls, so carriers must provide their customers with problem-free experiences to keep them satisfied," said Parsons. "Wireless customers have higher expectations than ever before of their phones and the networks on which they operate."

Complaints roll in

ConsumerAffairs.com hears tons of complaints about dropped calls. A sampling includes:

• Verizon Wireless customer Victoria of Dublin, CA, who writes, "I was told that I can use my cell phone from coast to coast and that they have more towers so less dropped calls. But I even got dropped talking to Verizon Tech; they had to call me back on a landline phone."

• Yvette of Vicksburg, MS, tells us, that when she opened her T-Mobile account, "the service wasn't great to begin with but got worse as time went by. Dropped calls, loss of signal for no reason right in the middle of calls etc. I finally decided to switch to another cell phone company."

• "My husband and I began experiencing a very high amount of dropped calls on our Nextel mobile phones," wrote Christina, of Baltimore. "Finally after four months of not being able to make a cell call without it being dropped, I called to cancel."

Additional study findings

• Wireless usage patterns continue to evolve, as fewer calls are made or received and customers use their devices more often for text messaging, which increasingly is the preferred method for communication. The study finds that wireless customers receive 144 text message notifications per month -- 29 percent more text message notifications than reported one year ago.

• PP100 scores continue to be higher among smartphone customers than among traditional handset customers -- 13PP100 vs. 9PP100. However, both rates are lower than those reported six months ago.

• Among the top 27 U.S. markets, the PP100 score is lowest among wireless customers in the Tampa, Fla., area (5 PP100), and highest among wireless customers in Charlotte, N.C. (19 PP100).

The study, based on responses from 26,595 wireless customers, was conducted between January and June 2010.