 base station to another. A softer handoff (see Sec. 8.7) is done completely within the base station, so the MSC has no role to play. A hard handoff involves the MSC in communication with two base stations, a dis- connect and reconnect, and any associated statistical bookkeeping. When the hard handoff is from one MSC to another, there is a lot more calculation to determine if it is a handoff forward, a handoff back, or a path minimization, as described in Sec. 15.1. A soft handoff (see Sec. 8.7) keeps the MSC very busy. The switch designer has to de- cide where the workload goes, but some part of the MSC has to compare each frame from all the soft-handoff sources on the reverse link and select the best one. This frame- comparison activity is an ongoing effort unlike call processing, where the work ends when the call begins. cdmaOne calls can spend one-third of their time in soft handoff, so this is a major MSC resource issue. The MSC processor is such an important part of the system that it should have com- fortable performance margins. If a link runs out of capacity, then a few subscribers get lousy service for a few seconds. If a packet handler gets backed up, then a few sub- scribers get slow Internet response. However, if the MSC processor gets behind in its workload, then the entire system is in trouble. 24.2 The Flow of Bits Through the Switch There is a limit to how many connections a switch can have. Wires in an analog switch have evolved into time division multiplexers in a digital switch, but the principle is the same. Any switch technology can handle some maximum bit throughput, some maxi- mum number of simultaneous voice connections. All the data pipes from all the base stations come into the MSC. Each base station needs one or more DS-1 or E-1 links, and the sum total of these is a major part of the total facilities load of the MSC. The voice trunks to the public switched telephone network (PSTN) are also part of the switch-throughput picture. If subscriber demand is primarily voice calls, then these