Performance evaluation for spread-spectrum multiple-access communication systems

The performance of the spread-spectrum multiple-access communication system is analyzed assuming that channel access from each terminal (station) is random. By distinguishing the retransmission traffic load from the freshly originating traffic load, a more accurate formula for message delay can be derived. By comparing the performance between this communication system and the FDMA, this system is shown to have higher usage efficiency of the channel bandwidth. Moreover, the processing gain optimizing the system performance is obtained as the function of the mean offered load. Using this fact, we consider the group random access scheme where all terminals are grouped according to their utilization forms if possible. Then each group uses the separate channel whose bandwidth is determined in accordance with the offered load, and its performance is evaluated.