The rapid growth of mobile service users is forcing telecom operators to invest in newrninfrastructure. However, looking for techniques for optimum network utilization that canrnoptimize the interoperability features among different technologies has the potential to reducerninvestment costs for the deployment of infrastructure. Optimizing the circuit switched inter radiornaccess technology between universal mobile telephone system (UMTS) and global system forrnmobile (GSM)) handover success rate failure allows the operator to use the ubiquitous 2Grnnetwork to provide service in the coverage discontinuity of the 3G network, as well as loadrnsharing between the networks.rnIn this thesis, based on the circuit switched inter radio access technology (CS IRAT) 3G-to-2Grnhandover success rate report data of the Addis Ababa network, a problematic sample IRATrnnetwork has been chosen, and the handover is optimized for the sample network and interpretedrnfor the whole Addis Ababa network. First, with the help of Pareto techniques, the root cause ofrnthe handover (HO) failure rate is analyzed using two months report data, and it is found thatrnphysical channel failure is the main cause of the IRAT handover failure. Second, a samplernnetwork (study area) is selected based on the HO success rate and the number of handoverrnattempts (success rate of 70% and number of attempts > 10,000 per day). Then methods to solvernthe root cause of the problems were suggested (adjusting the neighbor relations and tuning therntarget 2G network handover threshold) based on the different literature reviewed and the effectsrnof the parameters on the IRAT handover. With Atoll (planning tool), the sample network (realrnnetwork) identified is designed using engineering parameters of the network obtained from EhtiornTelecom. Finally, using the sample network as an input, the neighbor relation is redefined andrnthe handover coverage of the network is optimized. It is found that the handover coverage area (arnpossible location where a handover could occur) shrinks with the increase in the target 2Grnnetwork handover thresholds, which will lead to first a decrease in the total number of handoverrnattempts and, second, from the total, an increase in the success of those attempted handovers,rnsince the 2G cell gets stronger. The above two conditions result in an improvement in handoverrnsuccess rate since it is the ratio of successful handovers to the total number of handovers.