For telecom operators, base station is one of the most important mobile networkrncomponent from which messages are sent and received directly to/from users. The basernstation consists of different hardware and software components. Any of theserncomponents could experience various types of faults (critical, major and minor) that mayrncause partial or full failure of the base station until correction is made. Base station outagernresults in its usersâ€™ service interruption or quality degradation that in turn brings to thernoperator churn of users/services and loss of revenue. Therefore, outage is needed to bernmonitor and its cause should be identified timely for timely maintenance actions. rnTo reduce maintenance time and cost, different advanced outage root cause analysisrnmethods have been studied and applied. However, there are limited studies in the contextrnof Ethiopia. The objective of this thesis is to present root cause analysis of base stationrnoutage for Addis Ababa using Bayesian network empowered by trouble ticket, log file,rnand history alarm. rnResults show that application of root causes analysis can be achieved to identify,rncategorize and define appropriate supportive action for base station outage. Byrnanalyzing, the base station outage based on collected history alarm, log file and troublernticket data can compute probability distribution and provide a priority checking. Forrninstance, the result from historical data collected for year shows that the performancernof Bayesian network with an accuracy of 94%.