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Table of Contents
An Adaptive Receiver for STBC in Frequency Selective Channel with Improved Robustness and Pilot Requirements
Optimal Power Control of a Three-Shaft Brayton Cycle Based Power Conversion Unit
Universal Decremental Redundancy Compression With Fountain Codes
An Adaptive Receiver for STBC in Frequency Selective Channel with Improved Robustness and Pilot Requirements by J. Mathew, H. Xu and F. Takawira
Abstract: The semi-blind recursive least squares (RLS) based adaptive receiver has been designed to perform joint interference suppression and equalization for space time block codes (STBC) in a frequency and time selective channel. In order to decrease pilot requirements in the training block, this paper introduces a linear predictor (LP) algorithm to do a forward prediction of the channel coefficients based on a smaller pilot block. We then introduce a QR-decomposition (QRD) based algorithm to improve the performance of the receiver at higher Doppler frequencies. The simulation results show that the addition of the LP does not affect the frame error rate (FER) of the overall system. Linear prediction requires a smaller number of pilot symbols in order to provide the channel estimates for a given burst. Hence the LP increases the overall throughput of the system by decreasing the pilot symbols required. The simulation results show that this is a more effective method for improving the system performance as the overall FER of the combined QRD-LP receiver is decreased significantly. Finally, by comparing the QRD based receiver and the RLS based receiver at higher Doppler frequencies, we verify that the QRD receiver has superior FER performance under these conditions.
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Optimal Power Control of a Three-Shaft Brayton Cycle Based Power Conversion Unit by K.R. Uren, G. Van Schoor and C.R. Van Niekerk
Abstract: This paper discusses the development of a control system that optimally controls the power output of a Brayton-cycle based power conversion unit. The original three shaft design of the Pebble Bed Modular Reactor (PBMR) power plant is considered. The power output of the system can be manipulated by changing the helium inventory to the gas cycle. The helium inventory can be manipulated in four ways: Injecting helium at the high-pressure side of the system by means of a booster tank; extracting helium at the high-pressure side of the system; injecting helium at the low pressure side of the system and lastly opening and closing the bypass control valve. The control system has to intelligently generate set point values for each of the four helium manipulation mechanisms to eventually control the power output. In this paper two control strategies are investigated namely PID control and Fuzzy PID (FPID) control. The FPID control strategy is a linear type Fuzzy controller, but can progressively be made nonlinear if nonlinearities exist in the system. An optimal control system is derived by applying an optimisation technique to the gain constants of the controllers. A Genetic Algorithm (GA) is used to optimise the gain constants of both the PID and FPID controllers. The GA uses the ITAE performance index as an objective function.
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Universal Decremental Redundancy Compression With Fountain Codes by F.P.S. Luus, A. McDonald and B.T. Maharaj
Abstract: A new universal noise-robust lossless compression algorithm based on a decremental redundancy approach with Fountain codes is proposed. The binary entropy code is harnessed to compress complex sources with the addition of a preprocessing system in this paper. Both the whole binary entropy range compression performance and the noise-robustness of an existing incremental redundancy Fountain code compression technique are exceeded. A new autocorrelation-based symbol length estimator, the Burrows-Wheeler block sorting transform (BWT) and Move-to-Front transformation (MTF) with a new entropy ordered MTF indices transformation reduces the binary entropy of a universal data source. The preprocessed input source is coded with a new modified incremental degree LT-code (Luby Transform) and a low-complexity decremental redundancy algorithm is used to compress the Fountain-coded source. The improved compression and robustness against transmission errors with our novel incremental degree puncturing decremental redundancy algorithm is shown. The universal (complex memory source) compression performance of the proposed system is shown to achieve appreciable compression.
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