Log-domain iterative sphere decoder with symbol sorting

In this paper the authors propose modified branch and pruning metrics for the sphere decoder to facilitate the use of apriori information in the sphere decoder. The proposed sphere decoder operates completely in the log-domain. Additionally the effect of order in which the symbols are decoded on the computational requirements of the decoder are investigated with the authors proposing a modification of the sorted QR decomposition (SQRD) algorithm to incorporate apriori information. The modified SQRD algorithm is shown to reduce the average number of computations by up to 95%. The apriori sphere decoder is tested in an iterative multiple input multiple output (MIMO) decoder and shown to reduce the bit error rate (BER) by an order of magnitude or provide approximately a one decibel improvement.http://www.saiee.org.za/DirectoryDisplay/DirectoryCMSPages.aspx?name=Publications#id=1588&dirname=ARJ&dirid=337am2016Electrical, Electronic and Computer Engineerin

Spectral occupation of TV broadcast bands : measurement and analysis

The findings of a TV broadcast spectrum measurement campaign, performed at six different locations on the Hatfield campus of the University of Pretoria, are presented. Since the use of television white spaces (TVWS) could help to alleviate the impending spectrum crunch, the motivation for the study was to identify possibly unused bands for use by emerging technologies, such as cognitive radio, and also to address the hidden node problem associated with spectrum sensing (SS). This was achieved by comparing measured data to both actual TV channel allocations and a geo-location database (GLDB) for the Tshwane metropolitan area (city of Pretoria). Localised measurements indicated that a number of TVWS opportunities existed, with between 216 and 376 MHz of spectrum found to be potentially available for secondary usage. However, a comparison with TV channel allocations (256 MHz free) and the GLDB (96 MHz free) highlighted the effect of the hidden node problem.The Sentech Chair in Broadband Wireless Multimedia Communications at the University of Pretoria, South Africa, the National Research Foundation (NRF) and the Independent Communications Authority of South Africa (ICASA).http://elsevier.com/locate/measurement2017-11-30hb2016Electrical, Electronic and Computer Engineerin

The effect of soil carbon on symboitic nitrogen fixation and symbiotic Rhizobium populations in soil with Trifolium repens as host plant

Soil organic carbon (SOC) is the main attribute of high-quality soil. The amount of nitrogen fixed by Rhizobium symbiotically with Trifolium repens (white clover) is ultimately determined by the quality of the soil environment. The effect of SOC on the total number of symbiotic and saprophytic rhizobia was determined. Subsequently, the amount of nitrogen (N) fixed was assessed by using the N difference technique. Most Rhizobium was detected between a SOC content of 2.03% to 3.80% in both inoculated and non-inoculated soils. Inoculation increased the number of rhizobia in soil. Most N was fixed in the soil with the lowest SOC content. Although the amount of N fixed increased as the level of SOC decreased, the efficiency of N fixation decreased proportionally to SOC. Subsequently, more N was rhizodeposited. It was concluded that symbiotic rhizobia introduced by the inoculant were more efficient than free-living rhizobia in soils with higher carbon content, which highlights the importance of inoculation in improving the sustainable production of T. repens pastures.http://tandfonline.com/loi/tarf20nf201

The quantification of biological nitrogen fixation by Trifolium repens as affected by soil organic matter

Management of the soil environment must receive special attention. Future research will not only be on increasing soil quality, but also on rectifying problems caused by our abusive past practices. Soil organic C is the main factor that influences soil quality, which will in turn determine sustainability and profitability.http://www.elsenburg.co

Iterative decoding of space-time-frequency block coded mimo concatenated with LDPH codes

In this dissertation the aim was to investigate the usage of algorithms found in computer science and apply suitable algorithms to the problem of decoding multiple-input multipleoutput (MIMO) space-time-frequency block coded signals. It was found that the sphere decoder is a specific implementation of the A* tree search algorithm that is well known in computer science. Based on this knowledge, the sphere decoder was extended to include a priori information in the maximum a posteriori probability (MAP) joint decoding of the STFC block coded MIMO signals. The added complexity the addition of a priori information has on the sphere decoder was investigated and compared to the sphere decoder without a priori information. To mitigate the potential additional complexity several algorithms that determine the order in which the symbols are decoded were investigated. Three new algorithms incorporating a priori information were developed and compared with two existing algorithms. The existing algorithms compared against are sorting based on the norms of the channel matrix columns and the sorted QR decomposition. Additionally, the zero forcing (ZF) and minimum mean squared error (MMSE) decoderswith and without decision feedback (DF) were also extended to include a priori information. The developed method of incorporating a priori information was compared to an existing algorithm based on receive vector translation (RVT). The limitation of RVT to quadrature phase shift keying (QPSK) and binary shift keying (BPSK) constellations was also shown in its derivation. The impact of the various symbol sorting algorithms initially developed for the sphere decoder on these decoders was also investigated. The developed a priori decoders operate in the log domain and as such accept a priori information in log-likelihood ratios (LLRs). In order to output LLRs to the forward error correcting (FEC) code, use of the max-log approximation, occasionally referred to as hard-to-soft decoding, was made. In order to test the developed decoders, an iterative turbo decoder structure was used together with an LDPC decoder to decode threaded algebraic space-time (TAST) codes in a Rayleigh faded MIMO channel. Two variables that have the greatest impact on the performance of the turbo decoder were identified: the hard limit value of the LLRs to the LDPC decoder and the number of independently faded bits in the LDPC code.Dissertation (MEng)--University of Pretoria, 2013.gm2014Electrical, Electronic and Computer Engineeringunrestricte

Captive the life of our static buildings

This research project investigates the possibility of a public programme-overlay at the Union Buildings, situated on Meintjieskop on the western edge of the Pretoria inner city. The design of the Buildings was commissioned to Sir Herbert Baker to celebrate the newly formed Union of South Africa in 1910. The buildings were completed in 1913 and this research project attempts to commemorate the centenary of this landmark. The buildings’ current state does not allow for public participation and this seems unfortunate for both the public and the buildings. This dissertation attempts to reintroduce the Union Buildings to South Africans, the Pretoria public as well as international tourists by recording the memory of the buildings. The intervention is an interpretative archive to the life of the Union Buildings. The static, stereotomic nature of the buildings has ironically been shaped and forced into many different symbolic meanings through the ever-changing political and cultural dynamics of South Africa. The life of the buildings has been interpreted into five distinguishing symbolic-eras: Birth, Union, Oppression, Democracy and Power. The new intervention attempts to make these layered eras public. This project will also explore the relationship between architecture and craft. This study understands that architecture is more than ever becoming a two dimensional experience and this is believed to be a direct result of the dimension in which it is explored - between pen and paper. The investigation will contest this current condition in which architecture finds itself. Moreover the focus of this study will be to explore architecture in its final dimension, thus exploring the relationship between architecture and craft. In the true sense this is a study of the tekton.Dissertation (MArch(Prof))--University of Pretoria 2012.ArchitectureMArch(Prof)Unrestricte

A reduced complexity soft-input soft-output MIMO detector combining a sphere decoder with a Hopfield network

In this paper, a reduced complexity soft-input soft-output MIMO detector is presented. The detector is intended to be used in conjunction with an error correction code. The detector combines a Sphere Decoder with a Hopfield network to calculate a max-log-map approximation. It is then combined with the error correction code in an iterative structure (turbo). The code used is a quasi-cyclic non-binary LDPC code. The simulation results demonstrate that with less computational complexity, the proposed system’s performance equals that of an optimal sphere decoder based detector

A Reduced Complexity Soft-Input Soft-Output MIMO Detector Combining a Sphere Decoder with a Hopfield Network

In this paper, a reduced complexity soft-input soft-output MIMO detector is presented. The detector is intended to be used in conjunction with an error correction code. The detector combines a Sphere Decoder with a Hopfield network to calculate a max-log-map approximation. It is then combined with the error correction code in an iterative structure (turbo). The code used is a quasi-cyclic non-binary LDPC code. The simulation results demonstrate that with less computational complexity, the proposed system’s performance equals that of an optimal sphere decoder based detector

Nodulation potential of four Trifolium repens cultivars under field conditions

Four Trifolium repens (white clover) cultivars were evaluated under field conditions to determine the potential of these cultivars to sucessfully develop Rhizobium-associated root nodules. Nodulation of T. repens is often poor, because of suboptimal environmental conditions or absence of host-specific rhizobia. The cultivars Huia, Haifa, Ladino and Regal were selected, as these are popular cultivars available in South Africa. Thousand seed mass (TSM) of each cultivar was measured to determine viability of seed and the possible interaction between TSM and nodulation. Mean TSM values of the cultivars differed significantly, with Huia having the highest TSM followed by Haifa, Ladino and Regal. Biomass production was also measured as an indicator of nitrogen fixation efficiency. The cultivar Huia, with the highest TSM values, resulted in the highest biomass production. Nodulation indices were determined from the size, number and colour of the nodules. All plants, regardless of cultivar, formed nodules within 8 weeks. It was concluded that TSM had no effect on nodulation. Planting date with associated temperature effects and the intrinsic cultivar effect also had no influence on nodulation. It was therefore concluded that nodulation potential of the four cultivars tested was similar under environmental conditions that prevailed during the study.http://www.tandfonline.com/loi/tarf20nf201