In spread spectrum systems employing parity bit selected spreading sequences, parity bits generated from a linear block encoder are used to select a spreading code from a set of mutually orthogonal spreading sequences. In this thesis, turbo receivers for SS-PB systems are proposed and investigated. In the transmitter, data bits are rst convolutionally encoded before being fed into SS-PB modulator. In fact, the parity bit spreading code selection technique acts as an inner encoder in this system without allocating any transmit energy to the additional redundancy provided by this technique. The receiver implements a turbo processing by iteratively exchanging the soft information on coded bits between a SISO detector and a SISO decoder. In this system, detection is performed by incorporating the extrinsic information provided by the decoder in the last iteration into the received signal to calculate the likelihood of each detected bit in terms of LLR which is used as the input for a SISO decoder. In addition, SISO detectors are proposed for MC-CDMA and MIMO-CDMA systems that employ parity bit selected and permutation spreading. In the case of multiuser scenario, a turbo SISO multiuser detector is introduced for SS-PB systems for both synchronous and asynchronous channels. In such systems, MAI is estimated from the extrinsic information provided by the SISO channel decoder in the previous iteration. SISO multiuser detectors are also proposed for the case of multiple users in MC-CDMA and MIMO-CDMA systems when parity bit selected and permutation spreading are used. Simulations performed for all the proposed turbo receivers show a signi cant reduction in BER in AWGN and fading channels over multiple iterations.

A new algorithm is proposed which provides a sub-optimum near-far resistant pattern for correlation with a known signal in a spread-spectrum multiple access environment with additive white gaussian noise (AWGN). Only the patterns and respective delays of the K-1 interfering users are required. The technique does not require the inversion of a cross-correlation matrix. The technique can be easily extended to as many users as desired using a simple recursion equation. The computational complexity is O(K²) for each user to be decoded. It is shown that this method provides the same results as the "one-shot" method proposed by Verdu and Lupas. Also shown is a new array architecture for implementing this new solution using delta-sigma modulation and a correlator for non-binary patterns that takes advantage of the digitized Al: signals. Simulation results are presented which show the algorithm and correlator to be implementable in VLSI technology. This approach allows processing of the received signal in real-time with a delay of O(.K) bit periods per user. A modification of the algorithm is examined which allows further reduction of complexity at the expense of reduced performance. / Graduation date: 1992

In spread spectrum systems employing parity bit selected spreading sequences, parity bits generated from a linear block encoder are used to select a spreading code from a set of mutually orthogonal spreading sequences. In this thesis, turbo receivers for SS-PB systems are proposed and investigated. In the transmitter, data bits are rst convolutionally encoded before being fed into SS-PB modulator. In fact, the parity bit spreading code selection technique acts as an inner encoder in this system without allocating any transmit energy to the additional redundancy provided by this technique. The receiver implements a turbo processing by iteratively exchanging the soft information on coded bits between a SISO detector and a SISO decoder. In this system, detection is performed by incorporating the extrinsic information provided by the decoder in the last iteration into the received signal to calculate the likelihood of each detected bit in terms of LLR which is used as the input for a SISO decoder. In addition, SISO detectors are proposed for MC-CDMA and MIMO-CDMA systems that employ parity bit selected and permutation spreading. In the case of multiuser scenario, a turbo SISO multiuser detector is introduced for SS-PB systems for both synchronous and asynchronous channels. In such systems, MAI is estimated from the extrinsic information provided by the SISO channel decoder in the previous iteration. SISO multiuser detectors are also proposed for the case of multiple users in MC-CDMA and MIMO-CDMA systems when parity bit selected and permutation spreading are used. Simulations performed for all the proposed turbo receivers show a signi cant reduction in BER in AWGN and fading channels over multiple iterations.

Ultra-Wideband impulse radio (UWB-IR) technology is an attractive method on multi-user for high data rate transmitting structures. In this thesis, we use the ultra wideband (UWB) signal that is modulated by the time-hopping spread spectrum technique in a wireless multiple access environments, and discuss the influences of multiple access interference. We discuss two parts of the influences of multiple access interference in this thesis. The first, we analyze the multiple access interferences on the conventional correlation receiver, and discuss the influences by using the time hopping code on different multiple access structures. The second, we know that the performances of user detection and system capacity would be degraded by the conventional correlation receiver in the multiple access channels. The Probabilistic Data Association(PDA) multi-user detection technology can eliminate multiple access interferences in this part. We will use this method to verify the system performance through the computer simulations, and compare to other multi-user detectors with convention correlation receivers. Finally, the simulation results show that the performance of the PDA multi-user detections is improved when the system is full loaded.

This thesis addresses handoff issues in a WCDMA system with space-time block coded transmit antenna diversity. Soft handoff has traditionally been used in CDMA systems because of its ability to provide an improved link performance due to the inherent macro diversity. Next generation systems will incorporate transmit diversity schemes employing several transmit antennas at the base station. These schemes have been shown to improve downlink transmission performance especially capacity and quality. This research investigates the possibility that the diversity obtained through soft handoff can be compensated for by the diversity obtained in a transmit diversity system with hard handoff. We analyze the system for two performance measures, namely, the probability of bit error and the outage probability, in order to determine whether the improvement in link performance, as a result of transmit diversity in a system with hard handoffs obviates the need for soft handoffs.

Thesis (Ph. D.)--University of Missouri-Columbia, 2002. / Typescript. Vita. Includes bibliographical references (leaves 189-194). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2002. / Typescript. Vita. Includes bibliographical references (leaves 189-194). Also available on the Internet.

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In spread spectrum systems employing parity bit selected spreading sequences, parity bits generated from a linear block encoder are used to select a spreading code from a set of mutually orthogonal spreading sequences. In this thesis, turbo receivers for SS-PB systems are proposed and investigated. In the transmitter, data bits are rst convolutionally encoded before being fed into SS-PB modulator. In fact, the parity bit spreading code selection technique acts as an inner encoder in this system without allocating any transmit energy to the additional redundancy provided by this technique. The receiver implements a turbo processing by iteratively exchanging the soft information on coded bits between a SISO detector and a SISO decoder. In this system, detection is performed by incorporating the extrinsic information provided by the decoder in the last iteration into the received signal to calculate the likelihood of each detected bit in terms of LLR which is used as the input for a SISO decoder. In addition, SISO detectors are proposed for MC-CDMA and MIMO-CDMA systems that employ parity bit selected and permutation spreading. In the case of multiuser scenario, a turbo SISO multiuser detector is introduced for SS-PB systems for both synchronous and asynchronous channels. In such systems, MAI is estimated from the extrinsic information provided by the SISO channel decoder in the previous iteration. SISO multiuser detectors are also proposed for the case of multiple users in MC-CDMA and MIMO-CDMA systems when parity bit selected and permutation spreading are used. Simulations performed for all the proposed turbo receivers show a signi cant reduction in BER in AWGN and fading channels over multiple iterations.