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.
Fishbone diagram is suggested to group all possible problem causes into common major categories which labeled on the ‘bone’ of the ‘fish’, e.g. 4M (methods, machines, materials, manpower); 4P (place, procedure, people, policies); 4S (surroundings, suppliers, systems, skills).
Refer to those categories, we might define all categories that more related to cellular environment to be specifically dropped call. An fishbone for dropped call analysis can be figured as it has categories of surroundings, antenna/feeder, hardware module, mobile subscriber, and software system.
An extensive analysis base on drive test and on site verification, alarm data inspection, configuration and radio parameter assessment, and network performance data analysis have to be performed to see overall causes relation and judge ‘most likely cause’.
At this point, we will possible to define root cause base on its priority on which we are going to validate through step by step proofing and finally found and decide the real root cause.