We introduce a new across-peer rate allocation algorithm with successive refinement to improve the video transmission performance in P2P networks, based on the combination of multiple description coding and network coding. Successive refinement is implemented through layered multiple description codes. The algorithm is developed to maximize the expected video quality at the receivers by partitioning video bitstream into different descriptions depending on different bandwidth conditions of each peer. Adaptive rate partition adjustment is applied to ensure the real reflection of the packet drop rate in the network. Also the granularity is changed to the scale of atomic blocks instead of stream rates in prior works. Through simulation results we show that the algorithm outperforms prior algorithms in terms of video playback quality at the peer ends, and helps the system adjust better to the peer dynamics.

Network coding (NC) is an optimal data dissemination technique where intermediate nodes linearly combine incoming packets. To recover a network-coded message, a sink must use a Gaussian elimination decoder, but this high-complexity decoder may not be acceptable in resource-constrained applications like sensor networks. A good alternative to Gaussian elimination is for the sink to apply the well-known belief propagation (BP) algorithm; however, the performance and complexity of BP decoding is dependent on the statistics of the linearly-combined packets. In this work, we propose two protocols that address this issue by applying fountain coding paradigms to network codes. For a two-source, single-relay, and single-sink network, named the Y-network, if the relay can network-code incoming packets while maintaining the key properties of the fountain code, then BP decoding can be applied efficiently to recover the original message. Particularly, the sink should see a Soliton-like degree distribution for efficient BP decoding. The first protocol, named Soliton-like rateless coding (SLRC), recognizes that certain encoded packets are essential for BP decoding to perform well. Therefore, the relay protects these important packets by immediately forwarding them to the sink. It can be shown analytically that the proposed scheme is resilient to nodes leaving the transmission session. Through simulations, the SLRC scheme is shown to perform better than buffer-and-forwarding, and the Distributed LT code. Although SLRC achieves good performance, the degree distribution seen by the sink is non-optimal and assumes that a large number of packets can be buffered, which may not always be possible. Extending SLRC, we propose the Improved Soliton-like Rateless Coding (ISLRC) protocol. Assuming a resource-constrained relay, the available resources at the relay are effciently utilized by performing distribution shaping; packets are intelligently linearly combined. The aggregate degree distribution for the worst case is derived and used in performing an asymptotic error analysis using an AND-OR tree analysis. Simulation results show that even under the worst case scenario of ISLRC, better performance can be achieved compared to SLRC and other existing schemes. / Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2011-10-07 21:13:03.862

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We define new metrics for linear codes over the ring Fq[u]/(ut) via an Fq-module monomorphism on linear codes over Fq. The construction generalizes the Gray map, Gray weight, and Lee weight; and the technique allows us to find some new optimal linear codes and their weight enumerator polynomial.

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Recent years have seen dramatic growth in Internet usage and an increasing convergence between Internet and wireless communications. There has also been renewed interest in iteratively decoded low-density parity-check (LDPC) codes due to their capacity approaching performance on AWGN channels.

A Research Report submitted to the Faculty of Health Sciences, University of the Witwatersrand in partial fulfillment for the degree of Master of Science in Medicine: Bioethics and Health Law Faculty of Health Sciences University of the Witwatersrand, Johannesburg, South Africa. January 2017 / Doctors serving in public health services in Kenya under the employment of the Government went on strike in December 2011 and September 2012. The strikes were national and doctors withdrew all their services including attending to emergencies in hospitals. The reasons for the strikes were poor salaries, poor working conditions and poor state of public health services. The aim of this research was to analyse legal and ethical aspects of the strikes by doctors in Kenya and to explore ways to minimize harm to patients and society. The research examined the circumstances and contexts of the strike to enable an understanding of the status of health services and the nature of the demands by doctors. Kenyan laws relating to strikes were analysed to ascertain legal compliance or violations during the strikes. Obligations of the medical profession and ethical codes and rules of conduct for doctors were discussed in relation to the strike. Ethical theories of deontology, consequentialism and virtue ethics were applied to establish moral justification or lack thereof. Analysis of the legal provisions of the Labour Relations Act No.14 of 2007 revealed that it did not provide adequate processes for resolving trade disputes involving workers and employers in essential services. Suggestions were made on some ways to improve the conciliation process to foster appropriate resolution of disputes before strike action becomes necessary. Examination of the reasons for the strikes and status of public health services revealed that there were compelling reasons and circumstances for the strike action by doctors. It was acknowledged that harm and benefits resulted from the strikes. Some grounds for moral justification of the strikes were discussed and found valid. However, comprehensive justification of the strikes was difficult, considering the professional and ethical obligations of doctors to society and to patients. In particular the withdrawal of emergency services made it difficult to find moral justification for the doctors‟ strikes. Failure to provide emergency services expunged any moral justification for strike action. / MT2017

The problem of the efficient use of Hybrid Automatic-Repeat-reQuest (Hybrid-ARQ) in wireless communication has attracted a considerable amount of research. In this thesis, the use and implementation of turbo codes as the Forward Error Correction (FEC) code for Hybrid-ARQ is investigated. The major accomplishments of the research include both the analysis and implementation of turbo Hybrid-ARQ. The thesis begins by obtaining a tractable bound for the performance of turbo codes with M-ary Quadrature-Amplitude-Modulation (M-ary QAM). The research considers the design problem of turbo coded Hybrid-ARQ optimized for AWGN and fading channels. The design problem of turbo Hybrid-ARQ in wideband channels is considered and an optimization strategy is proposed based on Orthogonal-Frequency-Division- Multiplexing (OFDM). The research also presents a novel rate scalable encoder structure that optimal selects a disparate but optimal pair of component codes given the channel conditions. A second part of the thesis considers the implementation of turbo Hybrid-ARQ in Very Large Scale Integration (VLSI ) systems. A design for a single architecture for Type-I and Type-II turbo Hybrid-ARQ is suggested in addition to approaches for improving performance of the Soft-Output-Viterbi-Algorithm(SOVA) decoder core. The research also proposes a SOVA decoder architecture that exploits reliability information to select between the SOVA and bi-directional SOVA.