Browsing by Author "Du Toit, F. J."

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    A fountain code forward error correction strategy for SensLAB applications
    (Stellenbosch : Stellenbosch University, 2014-04) Du Toit, F. J.; Wolhuter, R.; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.
    ENGLISH ABSTRACT: The discovery of sparse graph codes, used in forward error correction strate- gies, has had an unrivaled impact on Information theory over the past decade. A recent advancement in this field, called Fountain codes, have gained much attention due to its intelligent rate adaptivity, and lend itself to applications such as multicasting and broadcasting networks. These particular properties can be considered valuable in a wireless sensor network setting as it is capable of providing forward error correction, and the added conceptual network protocol related extensions. A wireless sensor network testbed in France, called SensLAB, provides an experimental facility for researchers to develop and evaluate sensor network protocols, aside from a simulation environment. Tremendous value can be added to the SensLAB community if an appropriate forward error correction design, such as Fountain codes, is deemed feasible for use on such a platform. This thesis investigates the use of Fountain codes, in a binary erasure channel environment, as a forward error correction strategy for the distribution of reliable data content over the SensLAB platform. A short message length LT code using two different decoding mechanisms were developed and evaluated for possible implementation. Furthermore, a short message length Raptor code was developed by using supplementary theory and optimisation techniques that permit scalability in terms of the message size. The results favoured the Raptor code design as it performs close to near optimal while still satisfying the rateless- and universality property, at low computational complexity.
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    Ruminal protein and fibre degradability of lucerne hay as affected by regrowth period and dairy breed
    (South African Society for Animal Science, 2011) Cruywagen, C. W.; Muller, C. J. C.; Du Toit, F. J.
    The chemical composition of roughages constantly changes while it grows towards maturity. The effective dry matter (DM), crude protein (CP) and neutral detergent fibre (NDF) degradabilities of lucerne hay (LH), harvested after regrowth periods of 4, 5 or 6 weeks, were determined in ruminally cannulated Holstein and Jersey cows by using the in sacco nylon bag technique. The degradabilities of DM and NDF across breeds differed between the LH harvested after the regrowth periods of 4, 5 and 6 weeks. Increasing the regrowth period of LH from 4 to 6 weeks significantly reduced effective DM degradability (k p = 0.08) from 59.0% to 51.2% and NDF degradability from 30.8% to 21.2%. Crude protein degradability tended to decrease with advancing maturity, with values of 77%, 73% and 74% after 4, 5 and 6 weeks' regrowth, respectively. Effective degradability of DM, CP and NDF did not differ between Holstein and Jersey cows. The results from this study suggest that LH harvested after a shorter regrowth period is of a higher quality in terms of DM, CP and NDF degradability which decreases as the plants mature.