Mobile Backhaul

2.2 Legacy Backhaul Networks

2.2.1 Backhaul Basic Technologies

Most existing backhaul networks have been built to serve 2nd generation mobile networks (e.g. GSM or CDMA networks), or to serve combined 2nd and 3rd generation mobile networks (e.g. for the GSM and WCDMA networks in the same area). In addition there are a few backhaul networks serving just 3rd generation mobile networks.

These MBH networks are often built based on TDM transport technologies, i.e. mainly based on PDH and SDH/Sonet transport equipment, especially on lower tiers of the networks. Backhaul connections with these technologies are of fixed bandwidth, and they can be changed only by node reconfigurations locally or, with newer equipment, remotely by a network management system. Transport capacities in these networks are 1.5 or 2 Mbit/s or their multiples, 8 Mbit/s, 34 and 45 Mbit/s, and in upper tiers of the networks 155 Mbit/s and its multiples (620 Mbit/s, 2.5 Gbit/s etc) – the TDM bit rates are discussed in more detail in Chapter 05.

Some backhaul networks built specifically for 3rd generation mobile networks (WCDMA) also contain some ATM equipment e.g. for traffic concentration, especially on the aggregation and backbone network tiers. This equipment can improve capacity utilization efficiency compared to TDM, but on the other hand it adds another network layer to be managed and maintained, thus increasing network operational costs. ATM equipment has similar physical interfaces as PDH and SDH equipment ...