A test device may be a portable test device that can perform over the air measurements to determine synchronization errors between clusters in a cellular network. The test device can generate a graphical user interface that can show a map of the boundary area between clusters, locations of base stations in the boundary area, locations where over the air measurements were taken by the test device, an indication of whether cells are in synchronization for each measurement location, and a table of actual measurements and derived parameters pertaining to cell phase synchronization, interference and other performance metrics.