Effects of overhead on the throughput and delay performance of mobile satellite communications using the Slotted CDMA ALOHA systems are examined. Computer simulation is carried out using measured propagation data, and throughput performances for the different propagation characteristics are compared. The packet delay performance is evaluated along with the altitude of satellite when ARQ (automatic repeat request) scheme is introduced for error control. Also proposed are the Adaptive Data Rate Slotted CDMA ALOHA. This method is that the technique that data rate is changed every packet by the situation of the propagation path is applied to the Slotted CDMA ALOHA. The improving throughput, delay time and data rate are shown in case of high traffic.