There are various techniques for adapting the transmission rate of an application while maintaining the perceived quality at the receiver at acceptable levels. Shared channel systems can use this rate adaptation capability to increase the number of concurrent applications in the system. This can be achieved by appropriately modifying the rate of the already running applications when a new connection arrives in the system. We present an analytical model for a class of algorithms for channel sharing by rate adaptive applications. We provide means for calculating performance measures related to the quality of reception of an application. We also present the design of algorithms that ensure fair channel sharing while keeping the application performance within acceptable levels.