Call admission in power controlled CDMA systems

In power controlled CDMA systems, the number of users that each cell can support is limited by the total interference received at each base station and will vary with time. When a system is congested, admitting a new call can only make the link quality worse for ongoing calls and may result in call dropping. Thus, a system needs a call admission policy for new call requests to maintain acceptable connections for existing users. We use a weighted combination of call blocking and call dropping probabilities as a system performance measure. We study a transmitted power based call admission control (TPCAC) scheme that protects ongoing calls and a received power based call admission control (RPCAC) scheme that blocks new calls when the total received at a base station exceeds a threshold. The proposed schemes are evaluated by simulation of a one dimensional system and the RPCAC scheme is found to offer significant performance improvements.