## 3 Results
### Fault Identification  
Since the first and second data sources have two different views of the network and the events within the network, the type of detected fault from these two sources differ. Drive testing accurately identifies fault location and cause when a data source (performance support system) cannot respond appropriately. These two data sources are complementary to each other. When there are complaints from subscribers in an area, an expert is used to improve the accuracy of the solution provided.  
As mentioned in the third section, it is necessary to examine the key performance indicators discussed in the second section for the short call scenario. Identifying the reason for blocking a call request using measurable parameters and features is not achieved in the drive test. Therefore, according to the findings of the second section, it is necessary to comment on the problems of the traffic sector and signaling sector for the desired area. Related indicators to request blocking in the signaling sector include congestion in the traffic and signaling channels, the success rate in accessing the traffic and signaling channels, and interruption in the signaling channel.  
\begin{table}
\begin{tabular}{l l} \hline \hline
**The Number of Available Data Sources** & **Used Method** \\ \hline Only source number 1 reports an fault. & Check the problem \\ Source number 1 and 2 report an fault & \\ \hline Source number 1 and 3 are not available & Trust first source \\ \hline Source number 1, 2 and 3 are available & Trust first and second sources \\ \hline \hline \end{tabular}
\end{table}
Table 9: Checking different situations in combining information according to available data sources.  
Among the drive test data, there were eight blocked call requests. The results of comparing these requests with the indicators of the busiest hours of the same day are shown in the Table 10.  
It is evident that records 1, 6, and 8 did not have signaling problems, and the reason for the call blocking problem was related to the indicators of the traffic department. Thus, records 2, 3, 4, and 5 were almost healthy in establishing traffic department calls, and there was no need to perform traffic checks on the blocked calls. It was possible to identify the fault by the method of determining the cause and using the performance support system data.  
In this section, after introducing the third category of information, called subscriber complaints, we discussed the issue of combining different available information sources to identify the fault and also to analyze its cause. In this process, the main focus is on two sources of information, performance support systems and drive testing to identify the fault. A significant percentage of the complaints raised by subscribers is not a priority in solving network problems, and, from an economic pint of view, and even a technical point of view, are not cheap to resolve. Complaints from subscribers are only used to help the expert in identifying the cause of a fault that occurred in the system. Further investigations and analysis of subscribers' complaints to determine their importance in expressing the problem and helping to solve it are proposed as one suggestion for future work in this research. As mentioned before, the two information sources of drive test and performance support system data complement each other in fault detection and identify its cause. The combination of these two sources of information to identify the reason for the blocking of a call request in the drive test was investigated in this section, and how to find the cause of the fault in the field test, by using the method of identifying the fault caused in the data of the performance support system, was discussed.