Multiuser detection allows for the eecient use of bandwidth in Code Division Multiple Access (CDMA) channels through mitigation of near-far eeects and multiple-access noise limitations. The decorrelating detector, developed by Lupas, is a linear multiuser detector that is asymptotically optimal in terms of near far resistance when certain communication parameters are completely known to the det...

The function of medium access control (MAC) protocol and the capacity of physical layer sufficiently affect the system performance in the wireless networks. In this research, we propose a MAC protocol based on direct sequence code division multiple access (DS-CDMA) for the wireless networks to guarantee quality-of-service (QoS) which depend on physical layer information, named the cross layer t...

CDMA (code division multiple access) provides higher capacity, flexibility, scalability, reliability and security than conventional FDMA (frequency division multiple access) and TDMA (time division multiple access). It has already been widely deployed in the second generation cellular communication systems and was proposed for the emerging and future wireless systems, including the third genera...

In this paper, we study the design of space time spreading matrices that are modulation matrices for communications over multiple-antenna block fading channels. We assume the channel is known to the receiver only and find necessary and sufficient conditions on the space time spreading matrices for the separation of demodulation and decoding at the receivers without loss of optimality. From the ...

A fixed bandwidth expansion can be achieved either by coding or spreading, while each have different effect on the resultant signal space. Coding increases both Shannon and Fourier bandwidth whereas spreading only increases the Fourier bandwidth. In this document we are looking for the optimum combination of coding and spreading, in a Code Division Multiple Access (CDMA) system, that minimizes ...

We present a framework for iterative multiuser joint decoding of code-division multiple-access (CDMA) signals, based on the factor-graph representation and on the sum-product algorithm. In this framework, known parallel and serial, hard and soft interference cancellation algorithms are derived in a unified way. The asymptotic performance of these algorithms in the limit of large code block leng...

Direct sequence code division multiple access (DSCDMA) is a popular wireless technology. This system suffers from Multiple Access Interference (MAI) caused by Direct Sequence users and Near –far effect. Multi-User Detection schemes are used to detect the users’ data in presence of MAI and Nearfar problem. In this dissertation, we present comparative study between linear multiuser detectors and ...

Code division multiple access (CDMA) has been proposed for use in ber and free space optical communications. Sophisticated new receivers for CDMA are based on coherent reception, that is, reception where the phases of all the many users are known or can be tracked. While coherent detection is a reasonable assumption in many radio frequency systems, semiconductor lasers suffer from serious phase...

A multistep linear prediction approach is presented for blind channel estimation, multiuser interference (MUI) suppression, and detection of asynchronous short-code direct sequence code division multiple access signals in multipath channels. Only the spreading code of the desired user is assumed to be known; its transmission delay may be unknown. We exploit the recently proposed multistep linea...