Analysis of the error extension mechanisms within the European plesiochronous digital hierarchy

Within the last 20 years, digital networks have become a major part of both national and international telecommunications. The authors are not aware of published attempts to investigate the error generating mechanism and the types of errors that exist in real networks or how they propagate through the multiplex hierarchy. Theoretical studies have thus been initiated, and equipment has been deployed, to capture error events occurring across a wide range of network technologies with the intention of determining the consequences for hierarchical arrangements of asynchronous multiplexers. The paper describes a computer model developed to analyse the effect of errors on a digital network, and a good agreement between practical measurement and the theoretical analysis is obtained. Although the study is focused on the existing European digital hierarchy, the techniques are equally applicable to any asynchronous or synchronous network. Results are presented which raise questions on the assumptions made by the relevant CCITT bodies regarding the way in which errors propagate through the existing CEPT hierarchy.