Network performance and fault detection in a PSTN using non-intrusive methods

The paper presents a new approach for managing QoS in telecommunication systems based on Non-Intrusive Methods for performance evaluation of a Public Switched Telephone Network. These methods use devices called INMDs (In-service Non-intrusive Measurement Devices), which measure a series of significant parameters for the evaluation of network performance, analysing signals of telephone calls in progress; in this way measurements are continuously performed on the network without having to interrupt the service. Previous studies have shown the advantages and limits of this measurement method in relation to the diagnostic capabilities of single INMDs without considering the possibility of coordinating the measurement information collected by several INMDs, which would make malfunctioning detection more efficient. The method proposed by the authors is based on the presence in the management network of a mesh of INMDs that can be connected by means of data services (connections). The performance of the INMD mesh has been evaluated by means of a simulation tool called COQUE (COmmunication QUality Evaluation), which allows estimation of the performance obtainable and a reasonable guess of the trade-off between the costs and benefits obtainable with INMD techniques. The results obtained in a case study are interesting, as in a high percentage of cases malfunctioning is not only detected but also located. Moreover, the proposed case study indicates the possibility of programmable techniques that can further improve the performance of the method.