A channel assignment scheme for reducing call blocking rate in a DS-CDMA cellular system

We propose a channel assignment scheme for reducing call blocking rate in a base station (BS) of DS-CDMA cellular systems. The proposed scheme can be applied to the case where the reverse link capacity is enough, but all traffic channels are in a busy state. The proposed scheme takes advantage of the feature of soft handoff in which a mobile station holds its communication link even if one of the two communication links is released. The scheme estimates the mean and variance of the total received power level measured at the BS before assigning a traffic channel for a new call request. The BS makes a decision based on the estimated values whether the new call request will be accepted or not. If it is decided that the capacity of the reverse radio link is enough, but the traffic channel is not available, then the BS increases the value of the soft handoff parameter T_DROP to release the traffic channel of mobile stations located in the soft handoff area. The BS assigns the released traffic channel to a new call or a handoff call. The performance of the proposed channel assignment scheme is evaluated by computer simulation. The results show that the call blocking rate for new calls and handoff calls is reduced