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Turbo Receiver for Spread Spectrum Systems Employing Parity Bit Selected Spreading SequencesMirzaee, Alireza 25 January 2012 (has links)
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.
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Proposed implementation of a near-far resistant multiuser detector without matrix inversion using Delta-Sigma modulationMyers, Timothy F. 29 April 1992 (has links)
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
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Turbo Receiver for Spread Spectrum Systems Employing Parity Bit Selected Spreading SequencesMirzaee, Alireza 25 January 2012 (has links)
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.
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Ultra WideBand Impulse Radio in Multiple Access Wireless CommunicationsLai, Weei-Shehng 25 July 2004 (has links)
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.
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Handoff issues in a transmit diversity systemJaswal, Kavita 17 February 2005 (has links)
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.
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Coverage vs. capacity analysis for CDMA cellular networks /Jiang, Hai, January 2002 (has links)
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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Coverage vs. capacity analysis for CDMA cellular networksJiang, Hai, January 2002 (has links)
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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Direct sequence spread spectrum cellular radioKchao, Camroeum 12 1900 (has links)
No description available.
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Multiuser detection in TH-UWB communication systemsHosseini, Iraj Unknown Date
No description available.
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Turbo Receiver for Spread Spectrum Systems Employing Parity Bit Selected Spreading SequencesMirzaee, Alireza 25 January 2012 (has links)
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.
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