Transmission quality of service

ITU-T recommendation E.171 specifies that an international connection shall have no more than 12 links in tandem. These links are apportioned so that four links are in the calling party's country, four links are used in the international connection and four links are in the called party's country. This then requires the design of national networks having no more than four links in tandem, to ensure the networks meet the transmission quality of service objectives. This is shown diagrammatically in Figure 4.17. The transmission quality deteriorates when more links are added in tandem. Post dialing delay increases when more tandem switches are added, the transmission impairments of bit error rates, pulse jitter and wander increase as more digital systems are connected serially in the transmission path.

Figure 4.17

Link allocation for an international connection

Figure 4.17

Link allocation for an international connection

0 0

Post a comment