Electronic signal processing techniques have assumed a prominent role in the design of fibre-optic communication systems. However, state-of-the-art systems operate at per-channel data rates of 100 Gb/s, which constrains the class of communication algorithms that can be practically implemented. Relative to LDPC-like codes, product-like codes with syndrome-based decoding have decoder dataflow requirements that are smaller by more than two orders of magnitude, which strongly motivates the search for powerful product-like codes. This thesis presents a new class of high-rate binary error-correcting codes, staircase codes, whose construction combines ideas from convolutional and block coding. A G.709-compliant staircase code is proposed, and FPGA-based simulation results show that performance within 0.5 dB of the Shannon Limit is attained for bit-error-rates below 1E-15. An error-floor analysis technique is presented, and the G.709-compliant staircase code is shown to have an error floor below 1E-20. Using staircase codes, a pragmatic approach for coded modulation in fibre-optic communication systems is presented that provides reliable communications to within 1 bit/s/Hz of the capacity of a QAM-modulated system modeled via the generalized non-linear Schrodinger equation. A system model for a real-world DQPSK receiver with correlated bit-errors is presented, along with an analysis technique to estimate the resulting error floor for the G.709- compliant staircase code. By applying a time-varying pseudorandom interleaver of size 2040 to the output of the encoder, the error floor of the resulting system is shown to be less than 1E-20.

Electronic signal processing techniques have assumed a prominent role in the design of fibre-optic communication systems. However, state-of-the-art systems operate at per-channel data rates of 100 Gb/s, which constrains the class of communication algorithms that can be practically implemented. Relative to LDPC-like codes, product-like codes with syndrome-based decoding have decoder dataflow requirements that are smaller by more than two orders of magnitude, which strongly motivates the search for powerful product-like codes. This thesis presents a new class of high-rate binary error-correcting codes, staircase codes, whose construction combines ideas from convolutional and block coding. A G.709-compliant staircase code is proposed, and FPGA-based simulation results show that performance within 0.5 dB of the Shannon Limit is attained for bit-error-rates below 1E-15. An error-floor analysis technique is presented, and the G.709-compliant staircase code is shown to have an error floor below 1E-20. Using staircase codes, a pragmatic approach for coded modulation in fibre-optic communication systems is presented that provides reliable communications to within 1 bit/s/Hz of the capacity of a QAM-modulated system modeled via the generalized non-linear Schrodinger equation. A system model for a real-world DQPSK receiver with correlated bit-errors is presented, along with an analysis technique to estimate the resulting error floor for the G.709- compliant staircase code. By applying a time-varying pseudorandom interleaver of size 2040 to the output of the encoder, the error floor of the resulting system is shown to be less than 1E-20.

In this thesis, we investigate partner selection schemes in multiuser cooperative networks. In networks, cooperative partners adopt coded cooperation to forward signals. Among the literature, two classes of two namely, centralized partner selections and distributed partner selections, have been proposed to select appropriate relays. Centralized partner selection is able to achieve the global optimization than distributed partner selection. However, centralized partner selections require high complexity, and global channel state information, which demands large amount of overhead and waste radio resources. Especially when the size of network increases, the cost to search appropriate relay for each user dramatically increases. Hence, we consider distributed partner selection scheme in the thesis. Among the existing work, fixed priority selection algorithm is a distributed partner selection algorithm strategy; where partner assignment is based on node indices do not include any channel information. To enhance performance, we exploit the geographical information of all users. Different from other distributed partner selection schemes, we adopt the method of Carrier Sense Multiple Access to exchange local information. We proposed coverage search algorithm, nearest source search algorithm and nearest middle-point search algorithm, the serve as the criteria of partner selection. The contributions of this thesis are to raise SNR, increase the probability that the achievable rate is great than the data rate in the distributed partner selection scheme, and enhance system performance.

In this thesis, a novel pre-coded direct-sequence code division multiple access (DS-CDMA) associated with the multiple-input multiple-output (MIMO) antennas, along with Alamouti¡¦s space-time block code (ST-BC) is considered. In the transmitter, the idea of hybrid pre-coded is exploited; it can be employed to counteract the inter-symbol interference (ISI) introduced by the channel fading duo to multipath propagation, and can be used to exacting the full information of channel impulse response (CIR) in the receiver for semi-blind channel estimation. Under this transceiver framework, we develop a semi-blind adaptive MIMO-CDMA receiver, based on the linearly constrained constant modulus (LCCM) criterion, for symbol recovery. Furthermore, to reduce the complexity of receiver design, the framework of the generalized sidelobe canceller (GSC) associated with the recursive least-squares (RLS) algorithm is adopted, and the gradient approach is applied to track the desired user¡¦s amplitude, simultaneously, and is named as the GSC-CM-IQRD-RLS algorithm. Via computer simulations, the superior performance and the advantages of proposed scheme is verified; it outperforms the conventional LCMV-based algorithm, and slightly better than the convention CM-GSC-RLS receiver, with the paid of spectral efficient.

This thesis proposes a framework for combined source-channel coding under power and bandwidth constrained noisy channel. The framework is then applied to progressive image coding transmission using constant envelope M-ary Phase Shift Key (MPSK) signaling over an Additive White Gaussian Channel (AWGN) channel. First the framework for uncoded MPSK signaling is developed. Then, it’s extended to include coded modulation using Trellis Coded Modulation (TCM) for MPSK signaling. Simulation results show that coded MPSK signaling performs 3.1 to 5.2 dB better than uncoded MPSK signaling depending on the constellation size. Finally, an adaptive TCM system is presented for practical implementation of the proposed scheme, which outperforms uncoded MPSK system over all signal to noise ratio (Es/No) ranges for various MPSK modulation formats. In the second part of this thesis, the performance of the scheme is investigated from the channel capacity point of view. Using powerful channel codes like Turbo and Low Density Parity Check (LDPC) codes, the combined source-channel coding scheme is shown to be within 1 dB of the performance limit with MPSK channel signaling.

This dissertation describes the development of a novel gamma-ray imaging system concept and presents results from Monte Carlo simulations of the new design. Current designs for large field-of-view gamma cameras suitable for homeland security applications implement either a coded aperture or a Compton scattering geometry to image a gamma-ray source. Both of these systems require large, expensive position-sensitive detectors in order to work effectively. By combining characteristics of both of these systems, a new design can be implemented that does not require such expensive detectors and that can be scaled down to a portable size. This new system has significant promise in homeland security, astronomy, botany and other fields, while future iterations may prove useful in medical imaging, other biological sciences and other areas, such as non-destructive testing. A proof-of-principle study of the new gamma-ray imaging system has been performed by Monte Carlo simulation. Various reconstruction methods have been explored and compared. General-Purpose Graphics-Processor-Unit (GPGPU) computation has also been incorporated. The resulting code is a primary design tool for exploring variables such as detector spacing, material selection and thickness and pixel geometry. The advancement of the system from a simple 1-dimensional simulation to a full 3-dimensional model is described. Methods of image reconstruction are discussed and results of simulations consisting of both a 4 x 4 and a 16 x 16 object space mesh have been presented. A discussion of the limitations and potential areas of further study is also presented.

Ever since the proposal of turbo code in 1993, there has been extensive research carried out to improve both the performance and spectrum efficiency. One of the methods used to improve the spectrum efficiency was to combine turbo code with a trellis-coded modulation scheme, called turbo trellis-coded modulation (TTCM). The scheme is used in various applications such as deep-space communication, wireless communication and other fields. It is a well established fact that an increase in an interleaver size of a TTCM system results in an improved performance in the bit error rate (BER). In this thesis repeat-punctured turbo trellis-coded modulation (RPTTCM) is proposed. In RPTTCM, the effect of repeat-puncture is investigated on a TTCM system, repetition of the information bits increases the interleaver size, followed by an appropriate puncturing scheme to maintain the respective code rate. The TTCM and RPTTCM systems are simulated in an Additive White Gaussian Noise (AWGN) channel. To understand how the RPTTCM scheme will perform in a wireless channel, the Rayleigh flat fading channel (with channel state information known at the receiver) will be used. The BER performance bound for the TTCM scheme is derived for AWGN and Rayleigh flat fading channels. Thereafter repeat-punctured is introduced into the TTCM system. The BER performance bound is then extended to include repeat-puncturing. The performances of the TTCM and RPTTCM systems are then compared. It was found that the RPTTCM system performed better at high signal-to-noise ratio (SNR) in both AWGN and Rayleigh flat fading channels. The RPTTCM scheme achieved a coding gain of approximately 0.87 dB at a BER of for an AWGN channel and 1.9 dB at a BER of for a Rayleigh flat fading channel, for an information size of N=800. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2010.

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A method for designing low-density parity-check (LDPC) codes for bandwidth-efficient high-order coded modulation is proposed. Code structure utilizes the multi-edge-type LDPC code ensemble to achieve an improved match between codeword bit protection ca- pabilities and modulation bit-channel capacities over existing LDPC coded modulation techniques. The multi-dimensional EXIT vector field for the specific multi-edge parame- terization is developed for the analysis and design of code ensembles. A multi-dimensional EXIT decoding convergence condition is derived to enable efficient optimization. Code design results in terms of ensemble thresholds and finite-length Monte-Carlo simulations indicate that the new technique improves on the state-of-the-art performance, with sig- nificantly lower design and implementation complexity.