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The cellular backhaul network is the terrestrial network that connects cell sites with the mobile switching center (MSC) in the core network.
Cellular backhaul traffic is carried by lines up to hundreds of kilometers long across multiple hops of copper, microwave, satellite, or fiber infrastructure. Because cellular traffic is compressed, overall traffic in the backhaul network is relatively low. A typical 2G base station serving an average population of 1000 subscribers requires a connection of only a few megabits (or a few E1/T1 lines).
To implement and operate backhaul networks, operators may either lease capacity from fixed line operators, or own it. When using owned capacity for backhaul infrastructure, microwave links are the most commonly used technology. Microwave technology is relatively inexpensive for low to medium capacity links, but it is difficult to scale up in support of the increased capacity demands of newer cellular technologies.
Aggregation and switching equipment is deployed in several levels of aggregation sites or hubs that concentrate the traffic coming from the lower network levels. In a traditional 2G TDM network, aggregation is performed by TDM access cross-connects, whereas in newly-deployed 3G networks, a packet switching solution based on ATM/IP technologies is used to concentrate traffic.
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