Effects of Time-Variations in Wireless Channels on the Two Different Fade-Resistant CDMA Systems

There are two code division multiple access (CDMA) systems which are capable of adapting to the time-varying nature of radio channels efficiently. In one of these systems, information symbols are transmitted simultaneously and in the other system, information symbols are chip-interleaved before transmission. Both systems exploit temporal variations in the channels so efficiently that depending on the signal-to-noise ratio values, using the estimated channel coefficients they are capable of outperforming the conventional system with perfect channel state information (CSI). In this correspondence, we analyze the relative performance behavior of these two promising fade-resistant CDMA systems. We show that both fade-resistant transmission systems exhibit identical performance when the system load is high. However, when the system load is light, the chip-interleaved system slightly outperforms the system that transmits information symbols simultaneously due to higher self-interference in the latter.