J.D. Power and Associates is reporting in their U.S. 2011 Wireless Network Quality Performance Study that performance levels for networks differ greatly depending on whether devices are used for voice, text, or data. Voice calls are the most challenging for wireless customers, followed by data. For data, slow downloads are the biggest complaint over connection failures or email problems. The same type of complaints are associated with calls, as audio quality has eclipsed dropped calls as the top concern. “Based on the varying degree of consistency with overall network performance, it’s…