Cooperative communication allows for single users in multi user wireless network to share their antennas and achieve virtual antenna transmitters, which leads to transmit diversity. Coded Cooperation introduced channel coding into cooperative diversity over traditional pioneer cooperative diversity methods which were based on a user repeating its partner's transmitted signals in a multi-path fading channel environment in order to improve Bit Error Rate (BER) performance.. In this dissertation the Coded Cooperation is simulated and the analytical bounds are evaluated in order to understand basic cooperation principles. This is done using Rate Compatible Punctured Convolutional Codes (RCPC). Based on the understanding of these principles a new protocol called Cross Layer Hybrid Automatic Repeat reQuest (ARQ) 2 Cooperative Diversity is developed to allow for improvements in BER and throughput. In Cross Layer Hybrid ARQ 2 Cooperation, Hybrid ARQ 2 (at the data-link layer) is combined with cooperative diversity (at the physical layer), in a cross layer design manner, to improve the BER and throughput based on feedback from the base station on the user's initial transmissions. This is done using RCPC codes which partitions a full rate code into sub code words that are transmitted as incremental packets in an effort to only transmit as much parity as is required by the base station for correct decoding of a user's information bits. This allows for cooperation to occur only when it is necessary unlike with the conventional Coded Cooperation, where bandwidth is wasted cooperating when the base station has already decoded a user's information bits. The performance of Cross Layer Hybrid ARQ 2 Cooperation is quantised by BER and throughput. BER bounds of Cross Layer Hybrid ARQ 2 Cooperation are derived based on the Pairwise Error Probability (PEP) of the uplink channels as well as the different inter-user and base station Cyclic Redundancy Check (CRC) states. The BER is also simulated and confirmed using the derived bound. The throughput of this new scheme is also simulated and confirmed via analytical throughput bounds. This scheme maintains BER and throughput gains over the conventional Coded Cooperation even under the worst inter-user channel conditions. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2008.

Multiple-input multiple-output (MIMO) technology has emerged as a popular technique for enhancing the reliability and capacity of wireless communication systems. In this dissertation, we analyze the spatial modulation (SM) MIMO technique and investigate possible extensions to this scheme. To date, there has been no literature reporting on the theoretical performance of M-ary quadrature amplitude modulation (M-QAM) SM with maximum likelihood (ML) based detection. The first objective of this dissertation is to present an asymptotic bound to quantify the average bit error rate (BER) of M-QAM SM with ML detection over independent and identically distributed (i.i.d) Rayleigh flat fading channels. The analytical frameworks are validated by Monte Carlo simulation results, which show the derived bounds to be tight for high signal-to-noise ratio (SNR) values. The ML based SM detector is optimal, since it offers the best detection performance. However, this technique is not practical due to its high computational complexity. The second objective of this dissertation is to introduce a novel SM detection scheme, termed multiple-stage (MS) detection. Performance and complexity comparisons with existing SM detectors show two main benefits of MS detection: near optimal BER performance and up to a 35% reduction in receiver complexity as compared to the ML based detector. Conventional SM schemes are unable to exploit the transmit diversity gains provided by the MIMO channel. The third objective of this dissertation is to propose Alamouti coded spatial modulation (ACSM), a novel SM based scheme with transmit diversity. The ACSM technique combines SM with Alamouti space-time block coding (STBC), thereby improving the diversity aspect and overall system performance of conventional SM. A closed form expression for the average BER of real constellation ACSM over i.i.d Rayleigh flat fading channels is derived and Monte Carlo simulations are used to verify the accuracy of this analytical expression. The BER performance of ACSM is compared to that of SM and Alamouti STBC. Simulation results show that the new scheme outperforms SM and Alamouti STBC by approximately 5.5 dB and 1.5 dB respectively, albeit at the cost of increased receiver complexity. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2010.

Computer speech recognition techniques were investigated. This investigation included a study of the hearing and speech process. An algorithm was developed that used nine features to identify the phonemes in speech signals. Two of these features, the total energy and the number of zero crossings in a specific section of the speech signal, were obtained directly from the digitized speech signal. The other features, frequency energy bands and formant frequencies, were measured from a spectral analysis of the signal. A Hewlett Packard mini-computer was used for the development of the necessary software in FORTRAN. For the testing of the algorithm ten words, "zero" through to "nine" were used. / Thesis (M.Sc.)-University of Natal, 1985.

A single chip line-rasterizer that overcomes the major bottleneck in graphics display systems has been designed by the author on a 4408 element gate array marketed by Plessey Semiconductors limited. The rasterizer was fabricated by Plessey using their 2 micron, double-level metal ISO CMOS process, in the United Kingdom. Two identifiable bottlenecks in the redraw speed on a general graphics display system are video memory bandwidth and rasterization speed (in dots produced per second). The rasterizer described here is capable of working in parallel with other rasterizers to overcome the rasterization bottleneck. Systems incorporating it are flexible and expandable. The rasterizer requests a primitive from a host or master part of the system. Once it has a primitive to work on, it begins rasterization. The rasterizer queues requests to write dots to the video memory part of the system. The device accepts two ordered pairs of 16-bit numbers as start-of-line and end-of-line coordinates, on an 8-bit bus; the dot addresses are in the form of two 16-bit numbers on a 32-bit bus. Simulation with CLASSIC showed that the device could be clocked at up to 8 MHz and would then produce dots at between 2 MHz and 4 MHz (dependent on the type of line) after the initial analysis overheads. This means that any video memory bandwidth may be fully used with this device and any improvements in memory bandwidth may be taken advantage of in a system using the parallel rasterization scheme. The Plessey test engineers exercised the device to prove the success of the fabrication. Further tests were performed by the author. In these, the rasterizer was seen to gather data correctly. The rasterization of a range of different types of lines, manhattan and general, short and long and lines of different direction, was tested. The various algorithm terminations were verified and all branches exercised. The flow control on the pixel bus was checked. The device used for all the tests, performed correctly at 10 MHz (design specification 8 MHz) which corresponds to a maximum rasterization speed of 5 MHz for 0° and 90° lines and between 2.5 MHz and 3.3 MHz for general lines. The results show that the rasterizer performance will allow full use of the memory bandwidth of the system and hence overcome the major bottleneck in many graphics display systems. / Thesis (M.Sc.)-University of Natal, 1987.

Techniques of colour measurement and colour reproduction are important in a wide range of commercial and social activities in most modern economies. Their study thus constitutes one of the major areas of interest to the CIE. The project described in this thesis began as an outgrowth of studies of new types of light sources and of the colorimetry of colour-TV systems; plus a conviction that modern TV cameras can operate effectively with a wide range of different illuminating spectra. It was soon evident that two important prerequisites for this research were: an understanding of the processes of human colour vision; and a knowledge of the standard, international, colorimetric terminology of the CIE. These topics are discussed fully in the text. Also included is a review of modern gas-discharge lamps, the~y properties, and their applications. Both high-pressure (HID) types and low-pressure (fluorescent-tube) types are considered. Because of the need to measure the colours of surfaces and their TV reproductions as accurately as possible, various forms of colorimeter were examined, leading to the choice of a spectrophotometer system for this work. The design, construction, and evaluation of an original spetrophotometer system (the UND Spectrophotometer) are described fully in the text. Finally, attention is given to the operation of a television system under nonstandard lighting. Twelve different light sources were evaluated as TV ((taking" illuminants, using both subjective and colorimetric methods of assessment. The experimental results tend to confirm that colorimetric methods are unsuited to colour reproduction evaluation, and that subjective methods are more meaningful. A subjective scale of colour reproduction performance was established, and it was found to correlate closely with the CIE general colour rendering index (Ra) for the various test lamps. The work reported herein predates similar experiments with TV lighting by other workers, and it includes a wider range of light sources. In spite of differences in experimental technique, however, there is broad agreement with their general results. / Thesis (M.Sc.Eng.)-University of Natal, Durban, 1987.

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.

Speech recognition systems fall into four categories, depending on whether they are speaker-dependent or independent of speaker population and on whether they are capable of recognizing continuous speech or only isolated words. A study was made of most methods used in speech recognition to date. Four speech recognition techniques for speaker-dependent isolated word applications were then implemented in software on an IBM PC with a minimum of interfacing hardware. These techniques made use of short-time energy and zero-crossing rates, autocorrelation coefficients, linear predictor coefficients and cepstral coefficients. A comparison of their relative performances was made using four test vocabularies that were 10, 30, 60 and 120 words in size. These consisted of 10 digits, 30 and 60 computer terms and lastly 120 airline reservation terms. The performance of any speech recognition system is affected by a number of parameters. The effects of frame length, pre-emphasis, window functions, dynamic time warping and the filter order were also studied experimentally. / Thesis (M.Sc.-Electronic Engineering)-University of Natal, 1990.

Steganography is classified as the art of hiding information. In a digital context, this refers to our ability to hide secret messages within innocent digital cover data. The digital domain offers many opportunities for possible cover mediums, such as cloud based hiding (saving secret information within the internet and its structure), image based hiding, video and audio based hiding, text based documents as well as the potential of hiding within any set of compressed data. This dissertation focuses on the image based domain and investigates currently available image based steganographic techniques. After a review of the history of the field, and a detailed survey of currently available JPEG based steganographic systems, the thesis focuses on the systems currently considered to be secure and introduces mechanisms that have been developed to detect them. The dissertation presents a newly developed system that is designed to counter act the current weakness in the YASS JPEG based steganographic system. By introducing two new levels of randomization to the embedding process, the proposed system offers security benefits over YASS. The introduction of randomization to the B‐block sizes as well as the E‐block sizes used in the embedding process aids in increasing security and the potential for new, larger E‐block sizes also aids in providing an increased set of candidate coefficients to be used for embedding. The dissertation also introduces a new embedding scheme which focuses on hiding in medium frequency coefficients. By hiding in these medium frequency coefficients, we allow for more aggressive embedding without risking more visual distortion but trade this off with a risk of higher error rates due to compression losses. Finally, the dissertation presents simulation aimed at testing the proposed system performance compared to other JPEG based steganographic systems with similar embedding properties. We show that the new system achieves an embedding capacity of 1.6, which represents round a 7 times improvement over YASS. We also show that the new system, although introducing more bits in error per B‐block, successfully allows for the embedding of up to 2 bits per B‐block more than YASS at a similar error rate per B‐block. We conclude the results by demonstrating the new systems ability to resist detection both through human observation, via a survey, as well as resist computer aided analysis. / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2010.

The effect of amplifier non-linearity on the performance of a CDMA communications system / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2009.

Transmit diversity usually employs multiple antennas at the transmitter. However, many wireless devices such as mobile cellphones, Personal Digital Assistants (PDAs), just to name a few, are limited by size, hardware complexity, power and other constraints to just one antenna. A new paradigm called cooperative communication which allows single antenna mobiles in a multi-user scenario to share their antennas has been proposed lately. This multi-user configuration generates a virtual Multiple-Input Multiple-Output system, leading to transmit diversity. The basic approach to cooperation is for two single-antenna users to use each other's antenna as a relay in which each of the users achieves diversity. Previous cooperative signaling methods encompass diverse forms of repetition of the data transmitted by the partner to the destination. A new scheme called coded cooperation [15] which integrates user cooperation with channel coding has also been proposed. This method maintains the same code rate, bandwidth and transmit power as a similar non-cooperative system, but performs much better than previous signaling methods [13], [14] under various inter-user channel qualities. This dissertation first discusses the coded cooperation framework that has been proposed lately [19], coded cooperation with Repeat Convolutional Punctured Codes (RCPC) codes and then investigates the application of turbo codes in coded cooperation. In this dissertation we propose two new cooperative diversity schemes which are the Repeat-Punctured Turbo Coded cooperation and coded cooperation using a Modified Repeat-Punctured Turbo Codes. Prior to that, Repeat-Punctured Turbo codes are introduced. We characterize the performance of the two new schemes by developing the analytical bounds for bit error rate, which is confirmed by computer simulations. Finally, the turbo coded cooperation using the Forced Symbol Method (FSM) is presented and validated through computer simulations under various inter-user Signal-to-Noise Ratios (SNRs). / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, 2008.