Recently, blind multi-user detection has become an important topic in code division multiple access (CDMA) systems. Direct-Sequence Spread Spectrum (DSSS) signals are well-known due to their low probability of detection, and secure communication. In this article, the problem of blind multi-user detection is studied in variable processing gain direct-sequence code division multiple access (VPG D...

Allocation of processing gain for data users using variable processing gain (VSG) in presence of voice users in cellular direct sequence (DS)-CDMA is considered. Optimal processing gain for data is determined while maintaining voice QoS (quality of service) in terms of outage probability. Optimal processing gain for data is allocated satisfying a constraint on voice outage probability. Effects ...

In recent years, there has been considerable interest in the use of CDMA in mobile communications. Bit error rate is one of the most important parameters in the evaluation of CDMA systems. In this paper, we develop a technique to find an accurate approximation to the probability of bit error for asynchronous direct–sequence code division multiple–access (DS/CDMA) systems by modeling the multipl...

An asynchronous multicarrier (MC) direct-sequence (DS) code-division multiple-access (CDMA) scheme for the uplink of the mobile communication system operating in a frequency selective fading channel is analyzed. Bit error rate performance of the system with either equal-gain combining or maximum-ratio combining is obtained. Numerical results indicate that the system performs better than that of...

We characterize the user capacity, i.e., the maximum number of supportable users at a common SIR target level for a fixed processing gain, of a single-cell symbol asynchronous CDMA system. We show that the user capacity of an asynchronous system is the same as the user capacity of a synchronous system; that is there is no loss in user capacity due to asynchrony. Optimum signature sequences are ...

In this paper, an efficient multiuser detection scheme with low decision delay is proposed for asynchronous variable processing gain (VPG) DS/CDMA systems in mobile radio channels without any restrictions on processing gains. An equivalent synchronous single bit rate DS/CDMA system is first formulated to break up the detection problem into the blocks of finite length called processing windows. ...

In this paper we consider a single-user adaptive receiver for interference suppression in asynchronous direct sequence code division multiple access (DSCDMA) communication systems with large processing gains. We propose an decomposed adaptive jilter structure for which each decomposed filter can be updated either in coupled way or in uncoupled waywith itsprevious filters. Performance results fo...

We consider packet DS-CDMA systems with a connectionless architecture where no dedicated connection is kept between users and the system. Users have to access the system using the same signature sequence and have to be acquired each time they need to send packets. Due to the asynchronous nature of the system, multiple users can be accommodated even when a single signature is available. However,...