In this paper, we investigate two packet scheduling schemes over the downlink of DS/CDMA systems to support packet data service. These schemes are the code division multiplexing (CDX)-based packet scheduling and the time division multiplexing (TDX)-based packet scheduling. To evaluate each scheme more effectively, we derive the throughput gain of the downlink as a performance measure based on the power constraint equation. In addition, the packet transmission delay of each scheme is derived and compared each other when the packet lengths of the concurrent data users are independently and identically distributed according to the exponential distribution. As the downlink capacity is quite related to the orthogonality factor, our analysis shows from the results that the throughput gain and the transmission delay are highly dependent on this factor. Furthermore, it is shown that the TDX scheduling scheme in CDMA downlink affords better performances than the CDX scheduling scheme, except when the orthogonality factor is around 1.

In this paper, a hybrid FDMA/CDMA system and a wideband CDMA (W-CDMA) system in the frequency selective Rayleigh fading are considered. The bit error rate (BER) and coded symbol error rate performance of a coherent BPSK RAKE receiver under the various number of receiver fingers are derived and evaluated. In addition, a multiple access control (MAC) protocol based on packet-switched network is proposed and computer simulation is performed. Then, the results of performance evaluation are compared. The numerical analysis shows that the performance of the hybrid system is better than that of the W-CDMA in situation when the RAKE receiver complexities are kept constant in both systems. As noted, when each system has as many fingers as paths, the performance of the full-fingered W-CDMA is best. The 2- or 3-subspectrum FCDMA, however, has almost the same performance compared with the full-fingered W-CDMA when we applied the proposed MAC protocol to the system.