When GSM was introduced in the early 90's, it was an over specified system. Nowadays it is that the whole range of services is widely in , and in addition performance is degrading due the rapidly increased number of mobile , numbering over 2.9 billion subscribers the world today. The performance of cellular is the most important issue concerning operators. The main goal is to keep satisfied with the delivered quality of . In order to achieve the best performance, providers have to monitor and optimize network continuously. A Network System (NMS) with an online is responsible for the collection of data on networks. For greater effectiveness, operators systems that do a lot more than collect and raw data. These systems are easier to use and advantage of all the data provided by NMS. In paper we summarize measurements that were out to evaluate the performance of the 's Air-Interface (Um). We developed a new Quality of Service (QoS) indicator that be provided to business development on a monthly basis. It would represent overall impact of the quality of service on . For these measurements, an operative network was utilized. The parameters (performance metrics) on a daily basis for were those with a direct impact on subscribers.