The impact of crosstalk in an Unbundled Environment on ATM and IP

In recent years DSL has become the dominant network access technology, at the same time many countries are unbundling their access networks. This unbundling represents a risk for DSL deployment in that control and management of the services deployed becomes more problematical. Crosstalk is the most important source of noise/interference on the line. Consequently, its impact must be taken into account in an unbundled environment. A crucial aspect of a transmission technology is how it affects higher layers of the protocol stack. ATM and IP are quoted as the preferred protocols for transmission over DSL. Crosstalk interferers can worsen the performance, especially when combined with impulse noise. Both of these protocols were designed for contention based environments, thus the impact of errors at the DSL layer on higher level protocols and services has to be determined precisely. Different applications have different requirements on lower layers. Voice requires low latency and tolerable error rate, whereas data requires lossless transfers where errors can only be overcome by retransmission. If ATM/IP is used as a link protocol it will be important to have information about the cell/packet error performance. This paper presents results of study of an ADSL system for different bit rates and framing on the DSL level. The current work gives details about the error rates of data streams impaired by impulse noise and crosstalk from interferers alien to ADSL, such as HDSL and ISDN. In ATM the performance metrics used are cell/header error rates.