ce because it is another broadcast copy of the serving signal. In conventional reuse systems (but not in CDMA), the repeater can shift the frequency so that it com- municates with the base station on one set of frequencies but communicates with user terminals on a different set. In CDMA systems, where the repeater is communicating with the base station on the same frequency used for communication with user termi- nals, the connection to the serving base station must be well isolated from the repeater serving antenna. 4.7 The Base-Station Controller (BSC) The brain of the base station is the base-station controller (BSC) that directs the oper- ation of the entire base station. Each sector of the cell has its own antenna faces and its own radio equipment, and they all come together at the BSC. As we will discuss in Chap. 7 GSM systems can have a single BSC control several cells. The BSC coordinates pages and mobile originations, sets up and tears down wireless telephone calls, selects radio resources for each call, and manages the handoff process. When a handoff stays within the domain of one BSC, the BSC can perform the switch- ing for the handoff. The BSC also connects the base stations to the MSC through pipes that carry the dig- itally encoded voice and data from the subscriber calls. 9 The connection from MSC is called backhaul, and the network of base stations served by a single MSC has a backhaul network connecting the base stations to their MSC. We describe the back- haul network design in Chap. 35. Somewhere along the way they skipped nanocells. Before repeater technology was in use, the original AMPS installation in Pittsburgh, Pennsyl- vania, seamlessly covered a very hilly area and two difficult tunnels, Fort Pitt and Squirrel Hill. This was a major feat of engineering that took a lot of work to accomplish. Repeaters could have made this job a lot easier. 9In the old days, we had a set of dedicated trunks, described in Chap. 13. Today, the interfaces aggregate calls and packetize data SO that the term t