In this article we identify some of the key problems that may be encountered when designing a broadband multiple access system with bandwidth on the order of tens or even hundreds of megahertz. We commence with a comparative discussion in terms of the characteristics of three typical code-division multiple access schemes: single-carrier directsequence CDMA (SC DS-CDMA), multicarrier CDMA (MC-CD...

In this paper, we propose a block signal detection scheme, which combines frequency-domain equalization and signal detection scheme developed for the multiple-input multiple-output (MIMO) multiplexing, for the reception of the multi-code direct sequence code division multiple access (DSCDMA) signals. The proposed signal detection scheme is described first. Then, we evaluate, by computer simulat...

In this paper we show how orthogonality constraints for DSCDMA spreading sequences yield directly to OFDM sequences. Having shown this duality we do a comparison of performances between these two waveforms in a multipath fading channel context. The comparison includes the MC-CDMA approach. We show how the cyclic prefix solution can be used for DSCDMA in order to propose an MMSE optimal despread...

This paper considers the problem of blind demodulation of multiuser information symbols in a direct-sequence code-division multiple access (DSCDMA) environment. Channel estimation and symbol detection in presence of both multiple access interference (MAI) and intersymbol interference (ISI) is carried out with second order statistics methods from the received data. This problem is similar to Dir...

The performance of a coherent rake receiver of DSCDMA systems is significantly affected by the accuracy of channel estimation. The performance of the channel estimator can be improved by employing a channel estimation filter (CEF) whose impulse response is adjusted according to the channel condition. In this paper, we consider the design of an adaptive channel estimator for DSCDMA systems with ...

| We analyze a slotted DSCDMA system to guarantee QoS requirements for realtime tra c [1]. A Markovian analysis for realtime tra c and an equilibrium point analysis (EPA) for non-realtime tra c are applied in a heterogeneous environment. Packet losses for realtime tra c, delay times for non-realtime tra c, and wireless link utilization are derived.

We consider the problem of multiuser detection for DSCDMA in doubly-selective (timeand frequency-selective) channels, and propose a time-varying multiuser detector (TVMUD) to solve this problem. Using a basis expansion model (BEM) to model the doubly-selective channel and the TVMUD, we derive a closed-form expression for the BEM coefficients of the TV-MUD as a function of the BEM coefficients o...

A random transmit power control (TPC) is applied to DSCDMA/TDD packet mobile radio, which controls the transmit power so as to intentionally vary the received signal power in order to obtain the large capture effect. The uplink capacity with the random TPC in a frequencyselective fading channel is evaluated by computer simulation. The simulation results show that the random TPC provides larger ...

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...