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.

To reach EU’s climate and energy target an integrated electricity market is considered to be required (Klessmann, et al., 2011; Boie, et al., 2014; Becker, et al., 2013). As a result the European Commission decided to form a set of rules, named the Network Codes, to create a single European market (ENTSO-E, 2013b). The Network Codes will affect Distribution- and Transmission System Operators, grid users and production units as well as all the other actors on the electricity market (Eurelectric, n.d.a). Concerns regarding what the Network Codes’ actual consequences are have been expressed within the line of business (Swedish Energy, 2013a). Therefore the purpose of this master’s thesis was to determine and furthermore illustrate the consequences the Network Codes will have, in current version, for a Swedish non-transmission system connected electricity company and determine what actions need to be taken. The purpose has been addressed by conducting interviews, document studies and by utilizing a change management model, the Intervention Strategy Model, introduced by Paton & McCalman (2000). The structured approach that is the nature of the model was used when determining the consequences the Network Codes enforce and what actions a non-transmission system connected electricity company has to take to cope with them. To further facilitate the determination of these actions this study was conducted on a non-transmission system connected electricity company, in this thesis named Electricity Company A. The investigation of the concerns expressed within the line of business illustrated that the concerns were diverse but a majority of them might be incorporated into either of the following groups, simulation models, demand side aggregator and information handling. Out of these groups information handling was by far the area of greatest concern with issues primarily connected to the Distribution System Operator. Consequently this thesis focused on the Distribution System Operator’s perspective. The analysis of the area of greatest concern, presented in two flow charts, clearly showed the increased amount of communication enforced by the Network Codes. This increased information handling results in numerous possible organisational consequences for the Distribution System Operator, for example might new systems be required and some existing systems be used with or without adaption. Furthermore, the extra workload could possibly be handled by the existing personnel, in some cases after complementary education, but it might also require new personnel. Finally the Network Codes open up for the possibility for the Distribution System Operator to define certain details which may be conducted individually or in cooperation with other Distribution System Operators. Which of these possible consequences that will affect a specific company is, however, dependent on its preconditions. The study on Electricity Company A reveals that the numerous actions required to handle the new communication were not as significant as the line of business might have feared. For Electricity Company A, primarily a new system is needed to handle the real-time values and some of the existing systems need to be updated. Additionally the combined extra work load might require extra personnel for Electricity Company A even though the individual work assignments are fairly small. The actions required should be fairly similar for companies of approximately equal size but might be more extensive for smaller non-transmission system connected electricity companies. All companies need, however, to conduct an individual analysis to determine which specific actions are required for them. The conclusions of this thesis aspired, and partly succeeded, to be generalizable on a European level. One example of this is the usage of the Intervention Strategy Model which proved applicable for determining which specific actions are required for all European electricity companies. Furthermore the concerns presented and the possible consequences of the increased information handling found, are generalizable but not complete for all European electricity companies. This thesis focused on one part of the complex Network Codes’ consequences and consequently further research is needed to fully understand the consequences for the electricity business in total.

Consider a network which consists of noiseless point to point channels. In this network, the source node wants to send messages to a specific set of sink nodes. If an intermediate node v has just one input channel then the received symbol by that node can be replicated and sent to the outgoing channels from v. If v has at least two incoming channels then it has two options. It can either send the received symbols one-by-one, one symbol in each time unit, or v can transmit a combination of the received symbols. The former choice takes more time compared to the latter option, which is called network coding. In the literature, it has been shown that in a single source finite acyclic network the maximum throughput can be achieved by using linear network codes. Significant effort has been made to efficiently construct good network codes. In addition, a polynomial time algorithm for constructing a linear network code on a given network was introduced. Also an algorithm for constructing a linear multicast code on an acyclic network was introduced. Finally, a method for finding a representation matrix for the network matroid of a given network G was also introduced. This matrix can be used to construct a generic code. In this thesis we first provide a review of some known methods for constructing linear multicast, broadcast and dispersion codes for cyclic and acyclic networks. We then give a method for normalization of a non-normal code, and also give a new algorithm for constructing a linear multicast code on a cyclic network. The construction of generic network codes is also addressed. / Graduate / 0984 / 0544 / esmaeili@uvic.ca

The conception of turbo codes by Berrou et al. has created a renewed interest in modern graph-based codes. Several encouraging results that have come to light since then have fortified the role these codes shall play as potential solutions for present and future communication problems. This work focuses on both practical and theoretical aspects of graph-based codes. The thesis can be broadly categorized into three parts. The first part of the thesis focuses on the design of practical graph-based codes of short lengths. While both low-density parity-check codes and rateless codes have been shown to be asymptotically optimal under the message-passing (MP) decoder, the performance of short-length codes from these families under MP decoding is starkly sub-optimal. This work first addresses the structural characterization of stopping sets to understand this sub-optimality. Using this characterization, a novel improved decoder that offers several orders of magnitude improvement in bit-error rates is introduced. Next, a novel scheme for the design of a good rate-compatible family of punctured codes is proposed. The second part of the thesis aims at establishing these codes as a good tool to develop reliable, energy-efficient and low-latency data dissemination schemes in networks. The problems of broadcasting in wireless multihop networks and that of unicast in delay-tolerant networks are investigated. In both cases, rateless coding is seen to offer an elegant means of achieving the goals of the chosen communication protocols. It was noticed that the ratelessness and the randomness in encoding process make this scheme specifically suited to such network applications. The final part of the thesis investigates an application of a specific class of codes called network codes to finite-buffer wired networks. This part of the work aims at establishing a framework for the theoretical study and understanding of finite-buffer networks. The proposed Markov chain-based method extends existing results to develop an iterative Markov chain-based technique for general acyclic wired networks. The framework not only estimates the capacity of such networks, but also provides a means to monitor network traffic and packet drop rates on various links of the network.

Denna rapport syftar till att utvärdera de för- och nackdelar den svenska gasmarknadsmodellen har relativt de shippermodeller som finns i Europa, där modellernas lämplighet att stimulera ökad konkurrens i synnerhet beaktas. Därtill behandlas de krav som nuvarande och kommande EU-lagstiftning ställer och vilka konsekvenser detta får för Sveriges del. Studien ska ge underlag för en bedömning om den svenska modellen är välfungerande eller om en förändring kan motiveras, och i så fall i vilken riktning. Till fördel för nuvarande svenska modell lyfts lättförståelighet och lägre motpartsrisk vid kapacitetsbokning fram. Även pristransparensen bedöms vara bättre till följd av att gas och transport faktureras separat. Transportkostnad fram till den svenska gränsen ingår likväl fortfarande i gaspriset. En shippermodell å andra sidan, bedöms skapa bättre förutsättningar för konkurrens och därmed öka incitamenten för utländska aktörer att ta sig in på den svenska marknaden. Dels ges aktörerna möjlighet att konkurrera om transport, dels skulle modellen överenstämma med de modeller utländska aktörer har på sina hemmamarknader. Många aktörer menar att den svenska modellen fungerar tillfredsställande i sin nuvarande utformning och att val av marknadsmodell inte är viktigast för utvecklandet av naturgasmarknaden. Mot bakgrund av detta samt de fördelar modellen har och den svenska marknadens ringa storlek, så framstår det som ett rimligt alternativ att behålla den. Vad gäller EU:s harmoniseringsarbete är det två nätkoder som i nuläget är mest aktuella, CMP och CAM, där CAM får konsekvenser för kapacitetsbokning i gränspunkter ellanentry/exit-zoner. Gränspunkten mellan Sverige och Danmark är i nuläget undantaget från CAM men åsikterna om huruvida detta är möjligt framöver eller inte går isär, ytterligare införselpunkter kan komma att skapa problem. Därtill vet vi inte i nuläget vilka konsekvenser kommande lagstiftning kan få för Sverige. Ett modellbyte kan således bli oundvikligt i slutändan. Vid ett byte är vår rekommendation är att undersöka möjligheten att övergå till en hel shippermodell, där både transmissions- och distributionsnät inkluderas i entry/exitzonen. Att ha en avvikande modell är tidskrävande, primärt för Energimarknadsinspektionen och Swedegas, till följd av EU:s harmoniseringsarbete som utarbetas för en shippermodell då detta är den vanligaste lösningen i Europa i allmänhet. Vi tror dessutom att en sådan lösning skulle gynna konkurrensen på marknaden, inte minst på hushållsmarknaden till följd av att kunden enbart får en kontaktpunkt oavsett om gasleverantör och distributionsbolag befinner sig inom samma koncern eller inte. / This report aims to evaluate the advantages and disadvantages of the Swedish gas market model in comparision to shipper models, which are common in the EU in general. The models’ suitability to stimulate competition is especially considered. In addition, the requirements of present and future EU legislation sets and the resulting consequences for Sweden are covered in the report. The study will provide a basis for assessing whether the Swedish model is well functioning or if a change is needed, and if so in which direction. Advantages of the Swedish model are that it is easy to understand and that it has a lower counterparty risk when it comes to capacity reservation. Also, the price transparency is considered to be better since the gas and transport charges are invoiced separately. Transportation cost to the Swedish border is nevertheless still included in the gas price. A shipper model on the other hand, is expected to create a more competitive market and to increase incentives for foreign players to enter it. The players are given the opportunity to compete for transportation and the model would also match the models foreign players face in their home markets, thus lowering the entry barriers. Many respondents think that the Swedish model works well in its present form and that the choice of market model is not of highest importance for the development of the natural gas market. In light of this, the benefits of the current model and the Swedish market's small size, it seems like a reasonable option to keep it. As for the EU harmonization, there are two network codes that are currently most relevant, CMP and CAM. The CAM network code has implications for capacity reservation in the cross-border points between different entry/exit-zones. The point between Sweden and Denmark is currently excluded from CAM, but opinions regarding whether this is possible in the future or  not differ. Additional entry points might create problems. In addition, at this point we do not know what impact future legislation may have. A model change can thus be inevitable in the  end.   If changing, our recommendation is to investigate the possibility of switching to a full shipper model where both the transmission and distribution networks are included in the entry/exit-zone. Having a model that differs from the rest of EU is time consuming, primarily for EI and Swedegas, since the harmonization efforts made by the EU are tailored for a shipper model since this is the prevailing system in Europe in general. We also believe that such a solution would benefit market competition. This is particularly true for the residential market because the customer only gets one contact point, whether gas suppliers and distribution companies are in the same Group or not.

Network coding was introduced as a means to increase throughput in communication networks when compared to routing. Network coding can be used not only to communicate messages from some nodes in the network to other nodes but are also useful when some nodes in a network are interested in computing some functions of information generated at some other nodes. Such a situation arises in sensor networks. In this work, we study three problems in network coding. First, we consider the functional source coding with side information problem wherein there is one source that generates a set of messages and one receiver which knows some functions of source messages and demands some other functions of source messages. Cognizant of the receiver's side information, the source aims to satisfy the demands of the receiver by making minimum number of coded transmissions over a noiseless channel. We use row-Latin rectangles to obtain optimal codes for a given functional source coding with side information problem. Next, we consider the multiple receiver extension of this problem, called the functional index coding problem, in which there are multiple receivers, each knowing and demanding disjoint sets of functions of source messages. The source broadcasts coded messages, called a functional index code, over a noiseless channel. For a given functional index coding problem, the restrictions the demands of the receivers pose on the code are represented using the generalized exclusive laws and it is shown that a code can be obtained using the confusion graph constructed using these laws. We present bounds on the size of an optimal code based on the parameters of the confusion graph. For the case of noisy broadcast channel, we provide a necessary and sufficient condition that a code must satisfy for correct decoding of desired functions at each receiver and obtain a lower bound on the length of an error-correcting functional index code. In the second problem, we explore relation between network function computation problems and functional index coding and Metroid representation problems. In a network computation problem, the demands of the sink nodes in a directed acyclic multichip network include functions of the source messages. We show that any network computation problem can be converted into a functional index coding problem and vice versa. We prove that a network code that satisfies all the sink demands in a network computation problem exists if and only if its corresponding functional index coding problem admits a functional index code of a specific length. Next, we establish a relation between network computation problems and representable mastoids. We show that a network computation problem in which the sinks demand linear functions of source messages admits a scalar linear solution if and only if it is matricidal with respect to a representable Metroid whose representation fulfils certain constraints dictated by the network computation problem. Finally, we study the usage of the sum-product (SP) algorithm for decoding network codes. Though lot of methods to obtain network codes exist, the decoding procedure and complexity have not received much attention. We propose a SP algorithm based decoder for network codes which can be used to decode both linear and nonlinear network codes. We pose the decoding problem at a sink node as a marginalize a product function (MPF) problem over the Boolean smearing and use the SP algorithm on a suitably constructed factor graph to perform decoding. We propose and demonstrate the usage of trace back to reduce the number of operations required to perform SP decoding. The computational complexity of performing SP decoding with and without trace back is obtained. For nonlinear network codes, we define fast decidability of a network code at sinks that demand all the source messages and identify a sufficient condition for the same. Next, for network function computation problems, we present an MPF formulation for function computation at a sink node and use the SP algorithm to obtain the value of the demanded function.

Reliable and energy-efficient delivery of multimedia to mobile terminals in dynamic networks is a very challenging problem. In this thesis, we focus on a cooperative extension to the Digital Video Broadcasting – Handheld (DVB-H) standard, forming a cooperative broadcast network whereby terminal-to-terminal cooperation creates a distributed form of multi-input-multi-output (MIMO) that supplements existing fixed network infrastructure. First, we develop a novel and computationally-efficient hierarchical Markov model that is able to accurately perform a cross-layer packet error mapping between the physical and transport layers of the DVB-H/IPDC (IP DataCast) protocol stack. We then construct a discrete-event simulator in MATLAB® that incorporates all of the necessary modules to conduct dynamic multiterminal network simulations. Next, the convergence of cooperative wireless communication, Raptor application layer forward error correction (AL-FEC) and Network Coding (NC) is examined. Originally proposed for broadcasting over the Internet, the application of Raptor codes to wireless cooperative communications networks has been limited to date, but they have been mandated for use in DVB-H. Network coding is used to reduce energy consumption by opportunistically recombining and rebroadcasting required combinations of packets. Two novel coding-enabled cooperative relaying protocols are developed for multicast and multiple unicast file distribution scenarios that are transparent, fully distributed, and backwards compatible with today's systems. Our protocols are able to exploit several different forms of diversity inherent to modern wireless networks, including spatial diversity, radio interface diversity, and symbol diversity. Extensive simulations show that our protocols simultaneously achieve breakthroughs in network energy efficiency and reliability for different terminal classes and densities, allowing greatly improved user experiences. / Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2010-08-03 19:45:54.943