Many see drive testing–the process of testing cellular systems and equipment by literally driving around with live mobile devices in a car or van—as the ultimate test of a cell phone or base station. However, drive testing incurs significant costs and liabilities while offering very little in terms of repeatability. For many years, testing and R&D labs have dreamed of “virtual drive testing” or the laboratory-based repeatable replication of live field environments. But the methods were always just out of reach of available technology. While current and emerging wireless technologies (specifically LTE and LTE-Advanced) compound the complexity required of virtual drive testing, the very factors that make it more difficult to create field conditions also make it more important to replicate those conditions. With this as a market driver, the industry has recently been able to deliver virtual drive-testing solutions that are both accurate and repeatable.
Although drive testing is valuable at every step in the wireless-service chain, it is often for different reasons. Network operators use it to fine-tune while “live,” to ensure that soon-to-be-deployed mobile devices don’t drain network resources under specific conditions, or to evaluate the performance of a mobile device. Mobile-device and silicon-device manufacturers use it to ensure competitive device performance in the field. Meanwhile, infrastructure vendors evaluate the capabilities of base-station products under varying radio conditions.
The common thread in all of this testing is the fact that a live network, operating under real-world conditions, is completely unpredictable. This very aspect of a live network leads to a lack of repeatability and devalues the results of testing. When an issue is discovered, the only way to objectively evaluate new software or an antenna design is to replicate the same conditions under which the bug was found.
The three steps required for successful virtual drive testing are:
1. To capture (record) field conditions from a physical drive route.
2. To convert the captured data into a form that is usable by available test equipment.
3. To convert that data into an effect imposed on cellular signals in the lab.
While this is an oversimplification, there are critical details and potential pitfalls that must be addressed at each stage of the process.