7.7 Resilience in the Controllers and the Core Interface
Controllers and gateways are often connected to the aggregation tier. Resilience in the aggregation network is provided e.g. by the functionality of MPLS and IP as discussed in sections 7.4 and 7.5.
Lower layers also (Sonet/SDH and fibre/wavelengths) may support resilience. These were addressed in Chapter 05.
7.7.1 BSC and RNC and Their Site Solutions
2G and 3G/HSPA BTSs are attached to a single controller element (BSC or RNC) in the radio access network. Controllers present a single point of failure in the system architecture. So the controller elements need to be highly reliable. BTSs can be rehomed to another controller, but this is accomplished by configuration in the management plane, and is not intended for protection but rather for radio network expansions. To assure high availability, controllers are built on fault tolerant platforms.
A controller site solution needs to be as highly resilient as the controller itself. Otherwise the failure of a site device will lead to an event similar to that of the failure of the controller. Security gateways and higher tier aggregation nodes also serve a high amount of BTSs. These nodes, as well as the links connecting to the elements need to have a high availability.
The architecture of the mobile network elements is not covered in 3GPP. What kind of resilience, unit redundancy, protection switching, load sharing and routing these elements support is an implementation issue. The ...