Editor's Note: This note describes key aspects of telecommunications network architecture in Africa.
The transit network is almost nonexistent. In many countries, the transit functions are implemented in local exchanges or switches and are located principally in the capital and in two or three main cities.
The transmission network has an unusual topology. When SDH rings are set up, they are used to connect telephone switches and their RCUs within the same urban center or region.
The networks still reflect choices of technology made in the 1990s. The number of small digital switches operated is higher than what could be achieved using modern technology. With the best technology available today, most of these networks could be equipped with only one or two digital switches. The scope of inefficiencies resulting from this technology legacy is large. To reach remote rural areas, subscriber concentration systems (TDMAs) are installed. These systems serve from 8 to 256 subscribers and use time division multiplexing technology, known as TDMA. TDMA cost per line is particularly high.
Fiber-optic systems are not yet widely rolled out. In many cases, the level of demand does not justify the rollout of broadband transmission systems. However, more and more operators are beginning to replace their microwave transmission links with fiber-optic cables.
Finally, in some countries, domestic satellite networks are used to extend coverage to isolated areas (rain forest, islands, and desert).