Dr. Kaoru Ishikawa, a Japanese quality control statistician, invented the fishbone diagram. Therefore, it may be referred to as the Ishikawa diagram. The fishbone diagram is an analysis tool that provides a systematic way of looking at effects and the causes that create or contribute to those effects. Because of the function of the fishbone diagram, it may be referred to as a cause-and-effect diagram. The design of the diagram looks much like the skeleton of a fish. Therefore, it is often referred to as the fishbone diagram.
Network optimization is commonly close related to root-cause analysis. Lets take for example identifying cause of dropped call that triggered by low signal strength.
Ping Pong handover is shown from the successful handover back to old cell within pre-defined time of total handover, e.g. less than 10 seconds. Since not all BSS vendors provide such performance counters it might be identified by simple metric that shall be expressed as total successful handover over number of call or connection, e.g. more than 200% indicates ping pong handover.