Perennial problems are caused for network operators by the operating system software upgrades released by handset manufacturers; these sometimes profoundly degrade the user experience. As stated above, the subscriber will tend to blame the operator for any impairment to the performance of their handset, even if the handset manufacturer's software upgrade caused the impairment.
Simulator tests form a crucial part of a safe roll-out programme for such software upgrades. Using a simulator, the operator can run a series of automated tests to measure the performance and stability of the new software build in a wide variety of network conditions and use cases. The results obtained can be compared with the results of previous benchmark tests to show whether performance is impaired by the new software. Such benchmark tests may be followed by small-scale statistical field trials, before finally allowing a full network-wide deployment.
Hardware performance underlies the user's experience of a handset. But what the user sees are applications, and their subjective judgements about the quality of a network are normally based on their experience of using their favourite applications (see Figure 3).
Figure 3: the application types most commonly used on smartphones.