CDMA Soft Capacity

A capacity limit is the maximum amount of service (such as data transmission rate) or number of customers that a system can provide services to at a defined level of service. The CDMA system has a soft capacity limit as the system operator can dynamically change the defined level of service to change the maximum number of customers (capacity limit) that can obtain service from the system. This allows the service provider to temporarily increase the system capacity in exchange for a reduction in the quality of voice.

A CDMA service provider can increase the number of customers on a CDMA mobile communication system by reducing the audio quality through increased speech compression. This lowers the average data rate per user, reducing interference, increasing the maximum number of users.

This figure shows that a soft capacity limit allows for the gradual decay of voice quality in a communication system when additional users are added in a system. To provide service to more customers than is the capacity limit (over capacity) in a CDMA system, users in the system are provided with lower bit rates (higher speech compression). As a result, assigning lower bit rates to users as service demand increases trades off voice quality for increases in system capacity.

CDMA Soft Capacity Limit Diagram