Performance of Generalized Receiver Employed by Broadband Multicarrier DS-CDMA System Using Space-Time Spreading-Assisted Transmit Diversity

In this paper the multicarrier direct-sequence code-division multiple access (MC DS-CDMA) using space-time spreading assisted transmit diversity is investigated in the context of broadband wireless communi-cations systems constructed based on the generalized approach to signal processing in noise over frequency-se-lective Rayleigh fading channels. We consider the issue of parameter design for the sake of achieving high-ef-ficiency communications in various dispersive environments. In contrast to the conventional MC DS-CDMA wireless communication system employing the time (T)-domain spreading only, in the present paper the broad-band wireless MC DS-CDMA wireless communication schemes employ both the time (T)-domain and frequen-cy (F)-domain spreading, i.e., employ the TF-domain spreading. The bit-error rate (BER) performance of the space-time spreading assisted broadband MC DS-CDMA wireless communications system is investigated for down-link transmissions associated with the single user and multiuser generalized detectors and is compared with that of the single user correlation detector and the multiuser decorrelating detector. Our study demonstra-tes that with appropriately selecting the system parameters, the broadband MC DS-CDMA wireless communi-cation system using the space-time spreading assisted transmit diversity constitutes a promising downlink tran-smission scheme. This scheme is capable to support ubiquitous communications over diverse communication environments without the BER performance degradation

Performance Analysis of Hybrid ALOHA/CDMA RFID Systems with Quasi-decorrelating Detector in Noisy Channels

In this paper we investigate the tag identification performance of ahybrid Aloha/CDMA radio frequency identification (RFID) system withquasi-decorrelating detector (QDD). Motivated from the fact that theQDD outperforms the conventional decorrelating detector (DD) innoisy network scenarios, we study and propose using QDD as one ofthe most promising candidates in the structure of RFID readers.Performance analysis in terms of bit error rate and the RFID systemefficiency is considered. Computer simulations are also performed,and the obtained results of QDD-based structure are compared withthose of DD-based one to confirm the correctness of the designsuggestion.

Robust Multiuser Detection in Synchronous DS-CDMA System with MRC Receive Diversity over Nakagami-m Fading Channel

This paper presents the robust multiuser detection in synchronous direct sequence-code division multiple access (DS-CDMA) systems with Maximal Ratio Combiner (MRC) receive diversity over frequency-nonselective, slowly fading Nakagami-m channels in a non-Gaussian environment. Average probability of error is derived for decorrelating detector over single path Nakagami-m fading channel. A new M-estimator proposed to robustify the detector is studied and analyzed. Simulation results show that the new M-estimator outperforms linear decorrelating detector, the Huber, and the Hampel estimator based detectors.