Overall wireless network problem incidence has increased from 2011, driven primarily by issues with data services including mobile Web and email, according to the J.D. Power and Associates (http://www.jdpower.com/) "2012 U.S. Wireless Network Quality Performance Study."

Now in its 10th year, this semiannual study evaluates wireless customers' most recent usage activities in three areas that impact network performance: calling, messaging and data. Overall network performance is based on 10 problem areas that affect the customer experience: dropped calls; calls not connected; audio issues; failed/late voicemails; lost calls; text transmission failures; late text message notifications; Web connection errors; email connection errors; and slow downloads.

Network performance issues are measured as problems per 100 (PP100) network connections, where a lower score reflects fewer problems and better network performance. Carrier performance is examined in six regions: Northeast; Mid-Atlantic; Southeast; North Central; Southwest; and West.

The study finds that data-related issues, including mobile Web and email problems, have steadily grown more prevalent since the beginning of 2011. For example, during the first half of 2011, problem incidence for mobile Web connections, excessively slow mobile Web loading and email connection errors averaged 16 PP100. This rate increased significantly during the Volume 1 reporting period for the 2012 study (July to December 2011), to an average of 19 PP100.

Among these three data-related issues, problem incidence of slow download speeds increased the most, from 19 PP100 during the first half of 2011 to 21 PP100 between July and December 2011. Problem rates for other network quality areas, such as calling or text messaging, remain unchanged. The increase in data-related problems may be attributable to shifts in where wireless customers are using their devices and in the types of services they are accessing.

"The ways and places wireless customers use their devices have changed considerably during the past several years," sys Kirk Parsons, senior director of wireless services at J.D. Power and Associates. "For instance, in 2012, 58% of all wireless calls are made indoors -- where wireless connections can be harder to establish and maintain -- compared with only 40% in 2003. In addition, the rapid expansion of smartphone usage has also changed the ways in which wireless customers use their devices, which also impacts network quality."

According to Parsons, smartphone users send high volumes of calls, text messages and emails, which strains carrier networks more than does using traditional handsets or feature phones. Increased frequency of mobile video downloads also further exacerbates network strain. On average, between July and December 2011, wireless customers indicate that they connected to the mobile Web or used mobile email 20 times within a 48-hour period, which translates to 300 mobile Web connections per month, on average. This is an increase from 285 times per month, on average, during the previous six months.

"Based on varying degrees of consistency with overall network performance, it's critical that wireless carriers continue to invest in improving both the voice quality and data connection-related issues that customers continue to experience," says Parsons.

He adds that wireless network providers may realize financial benefits by providing high-performing networks. Among customers who switch to a new carrier to obtain better network coverage, average monthly spending is US$17 higher, compared with customers who switch for other reasons.

For a 15th consecutive reporting period, Verizon Wireless ranks highest in the Northeast region. Verizon Wireless achieves fewer customer-reported problems with dropped calls, initial connections, transmission failures and late text messages, compared with regional average. Verizon Wireless also ranks highest in the Mid-Atlantic, Southeast, Southwest and West regions.

In the North Central region, U.S. Cellular ranks highest for a 13th consecutive reporting period. Compared with the regional average, U.S. Cellular has fewer customer-reported problems with dropped calls, failed initial connections, audio problems, failed voice mails and lost calls.

The 2012 U.S. Wireless Network Quality Performance Study -- Volume 1 is based on responses from 27,438 wireless customers. The study was fielded between July and December 2011.