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.

We propose an iterative tuning process of blind/group-blind detector based on constant modulus property of digitally modulated signal. By adopting the iterative tuning process after applying blind/group-blind detectors, significant gains are attained compared to the original blind/group-blind detectors. The signal to interference and noise ratio (SINR) approaches to ideal MMSE detector even with reasonably small number of data samples.

Motivated by the result in [12] we present a new block iterative multiuser detection algorithm utilizing the constant modulus (CM) property of data symbols. The proposed iterative detector is developed based on a constrained least square (LS) cost function and CM projection. It can be seen as an extension of least squares constant modulus algorithm [1] in a sense that it minimizes the CM and the LS cost functions iteratively. Simulation study shows that even for a reasonably small number of symbols, say around 100 received symbols, the proposed iterative detector approaches the performance of ideal MMSE detector and considerably outperforms the conventional blind detectors, such as subspace blind method [7] or MOE detector [5].

The bit error rate (BER) performance of a fast frequency-hopped frequency division multiple access (FH-FDMA) system is evaluated with diversity combining receivers. The clipper receiver and the normalized envelope detection (NED) receiver which show better performance than other diversity combining receivers under n = 1 band multitone interference (MTI) are chosen as combining alternatives. From simulation results, n = 1 band MTI is the most destructive multitone interference strategy for the FH-FDMA system. As the number of groups increases, eventually becoming a FHMA system, the worst case performance of FH-FDMA with the clipper receiver improves monotonically, while that of the NED receiver hardly improves when the effect of the interference is relatively large. From the viewpoint of BER performance, the FHMA system with the clipper receiver is the most effective solution among the FH-FDMA systems in the presence of the worst case band MTI.

The Joint CDMA/PRMA (JCP) protocol, proposed by Brand and Aghvami, is modified to increase the capacity for mobile communication systems. To reduce multiuser interference, the modified JCP uses an access channel additionally to the traffic channels, on which each mobile terminal reserves a unique slot and code. Furthermore, the modified JCP employs receiver-based code scheme. In the case of voice-only traffic, the throughput increases by up to 15% compared to that of the conventional JCP, when Ploss is 0.01. Also, for the mixed traffic case, the throughput increases about 20%.

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.

The uplink performance of WCDMA with voice and World Wide Web (WWW) traffic over Dedicated Channel (DCH)/Common Packet Channel (CPCH) is investigated. The probability of voice packet dropping and average data packet delay are obtained by system level simulation. The system level simulation is conducted based on received Signal-to-Interference Ratio (SIR) with imperfect power control. In addition, we show that the performance of CPCH in terms of probability of data packet dropping is superior to that of DCH for transmitting WWW traffic. Furthermore, we obtain the supportable number of voice users when the target probability of voice packet dropping is set to be 10-2. The supportable number of data users is also found around knee area of average data packet delay.