Industrie-4.0 bringt eine wachsende Nachfrage an Netzwerkprotokollen mit sich, die es erlauben, Informationen vom Produktionsprozess einzelner Maschinen zu erfassen und verfügbar zu machen. Drahtlose Übertragung erfüllt hierbei die für industrielle Anwendungen benötigte Flexibilität, kann in herausfordernden Industrieumgebungen aber nicht immer zeitnahe und zuverlässige Übertragung gewährleisten. Die Beiträge dieser Arbeit behandeln schwerpunktmäßig Protokollentwurf und Protokollevaluation für industrielle Anwendungsfälle. Zunächst identifizieren wir Anforderungen für den industriellen Anwendungsfall und leiten daraus konkrete Entwufskriterien ab, die Protokolle erfüllen sollten. Anschließend schlagen wir Protokollmechanismen vor, die jene Entwurfskriterien für unterschiedliche Arten von Protokollen umsetzen, und die in verschiedenem Maße kompatibel zu existierenden Netzwerken und existierender Hardware sind: Wir zeigen, wie anwendungsfallspezifische Priorisierung von Netzwerkdaten dabei hilft, zuverlässige Übertragung auch unter starken Störeinflüssen zu gewährleisten, indem zunächst eine akkurate Vorschau von Prozessinformationen übertragen wird. Für deren Fehler leiten wir präziser Schranken her. Ferner zeigen wir, dass die Fairness zwischen einzelnen Maschinen durch Veränderung von Warteschlangen verbessert werden kann, wobei hier ein Teil der Algorithmen von Knoten innerhalb des Netzwerks durchgeführt wird. Ferner zeigen wir, wie Network-Coding zu unserem Anwendungsfall beitragen kann, indem wir spezialisierte Kodierungs- und Dekodierungsverfahren einführen. Zuletzt stellen wir eine neuartige Softwarearchitektur und Evaluationstechnik vor, die es erlaubt, potentiell proprietäre Protokollimplementierungen innerhalb moderner diskreter Ereignissimulatoren zu verwenden. Wir zeigen, dass unser vorgeschlagener Ansatz ausreichend performant für praktische Anwendungen ist und, darüber hinaus, die Validität von Evaluationsergebnissen gegenüber existierenden Ansätzen verbessert. / As smart factory trends gain momentum, there is a growing need for robust information transmission protocols that make available sensor information gathered by individual machines. Wireless transmission provides the required flexibility for industry adoption but poses challenges for timely and reliable information delivery in challenging industrial environments. This work focuses on to protocol design and evaluation aspects for industrial applications. We first introduce the industrial use case, identify requirements and derive concrete design principles that protocols should implement. We then propose mechanisms that implement these principles for different types of protocols, which retain compatibility with existing networks and hardware to varying degrees: we show that use-case tailored prioritization at the source is a powerful tool to implement robustness against challenged connectivity by conveying an accurate preview of information from the production process. We also derive precise bounds for the quality of that preview. Moving parts of the computational work into the network, we show that reordering queues in accordance with our prioritization scheme improves fairness among machines. We also demonstrate that network coding can benefit our use case by introducing specialized encoding and decoding mechanisms. Last, we propose a novel architecture and evaluation techniques that allows incorporating possibly proprietary networking protocol implementations with modern discrete event network simulators, rendering, among others, the adaption of protocols to specific industrial use cases more cost efficient. We demonstrate that our approach provides sufficient performance and improves the validity of evaluation results over the state of the art.

We consider the problem of secure communications in a Gaussian two-way relay network where two nodes exchange confidential messages only via an untrusted relay. The relay is assumed to be honest but curious, i.e., an eavesdropper that conforms to the system rules and applies the intended relaying scheme. We analyze the achievable secrecy rates by applying network coding on the physical layer or the network layer and compare the results in terms of complexity, overhead, and efficiency. Further, we discuss the advantages and disadvantages of the respective approaches.

Preventing the success of active attacks is of essential importance for network coding since even the infiltration of one single corrupted data packet can jam large parts of the network. The existing approaches for network coding schemes preventing such pollution attacks can be divided into two categories: utilize cryptographic approaches or utilize redundancy similar to error correction coding. Within this paper, we compared both paradigms concerning efficiency of data transmission under various circumstances. Particularly, we considered an attacker of a certain strength as well as the influence of the generation size. The results are helpful for selecting a suitable approach for network coding taking into account both security against pollution attacks and efficiency.

Le codage réseau est apparu comme une technique alternative au routage au niveau de la couche réseau permettant d'améliorer le débit et d'optimiser l'utilisation de la capacité du réseau. Récemment, le codage réseau a été appliqué au niveau de la couche physique des réseaux sans-fil pour profiter de la superposition naturelle des signaux effectuée par le lien radio. Le codage réseau peut être vue comme un traitement interne du réseau pour lequel différentes techniques de relayage peuvent être utilisées. Cette thèse étudie un ensemble de traitements ayant des compromis variés en terme de performance et complexité. Nous considérons le canal bidirectionnel à relais, un modèle de canal de communication typique dans les réseaux coopératifs, où deux terminaux s'échangent mutuellement des messages par l'intermédiaire d'un relais. La communication se déroule en deux phases, une phase à accès multiple et une phase de broadcast. Pour ce scénario, nous analysons, dans une première partie, une stratégie de "decode-and-forward". Nous considérons, pour cette étude, des alphabets de taille finie et nous calculons les probabilités moyennes d'erreur de bout-en-bout en se basant sur la métrique d'exposant d'erreur du codage aléatoire. Puis, nous dérivons les régions des débits atteignables par rapport à une probabilité d'erreur maximale tolérable au niveau de chaque nœud. Dans une deuxième partie de la thèse, nous proposons deux schémas de codage réseau pratiques, avec complexité réduite, qui se basent sur la stratégie de relayage "compress-and-forward" (CF). Le premier schéma utilise un codage en réseau de points imbriqués (nested lattices). Le deuxième schéma est une version améliorée qui permet d'atteindre des débits de données supérieurs pour l'utilisateur qui a les meilleures conditions canal. Nous construisons les régions des débits atteignables par les deux schémas proposés tout en optimisant la répartition du temps alloué à chacune des deux phases de transmission. Après l'étude du régime asymptotique, nous analysons le schéma de codage CF avec des réseaux de points de dimension finie. Nous nous concentrons sur le problème de la transmission analogique où la distorsion est optimisée. Enfin, nous étudions l'application d'un schéma de codage, basé sur la stratégie CF avec des réseaux de points imbriqués, pour le canal bidirectionnel à canaux parallèles. Ainsi, nous présentons deux régions de débits atteignables selon la technique de traitement, conjoint ou séparé, des sous-canaux par le relais. / Network coding has emerged as an alternative technique to routing that enhances the throughput at the network layer. Recently, network coding has been applied at the physical layer to take advantage of the natural signal superposition that occurs in the radio link. In this context, the physical-layer network coding can be seen as an in-network processing strategy for which multiple forwarding schemes can be proposed. This thesis investigates a set of processing schemes tailored to the network coding at the physical layer with various compromises between performance and complexity. We consider a two-way relay channel, a typical communication system in cooperative networks, where two terminals communicate with each other via a relay node. This communication occurs during two transmission phases, namely a multiple-access phase and a broadcast phase. For TWRC scenario, we first analyze a decode-and-forward strategy with finite size alphabets. We calculate the end-to-end average error probabilities based on random coding error exponents. Then, we derive the achievable rate regions with respect to a maximal probability of error allowed at each terminal. Next, we propose two low-complexity and practical schemes based on compress-and-forward relaying strategy. The first scheme employs nested lattice coding. The second is an improved version which enables higher data rates for the user experiencing the best channel conditions. We present an information-theoretic framework to reconstruct the achievable rate regions of both schemes by considering optimal time division between both transmission phases. After the asymptotic regime analysis, we study single-layer lattice coding scheme with finite dimension lattices. We focus on the analog transmission problem where the distortion is optimized. Finally, we investigate single-layer lattice coding scheme for parallel Gaussian two-way relay channel. We present two achievable rate regions based on whether the relay processes all the sub-channels jointly or separately.

Avec le nombre croissant d’appareils intelligents à faible puissance, au cours ces dernières années, la question de l’efficacité énergétique a joué un rôle de plus en plus indispensable dans la conception des systèmes de communication. Cette thèse vise à concevoir des schémas de transmission distribués à faible consommation d’énergie pour les réseaux sans fil, utilisant la théorie des jeux et le codage réseau instantanément décodable (IDNC), qui est une sous-classe prometteuse du codage réseau. En outre, nous étudions le modèle de l'échange coopératif de donnée (CDE) dans lequel tous les périphériques coopèrent en échangeant des paquets codés dans le réseau, jusqu’à ce qu’ils récupèrent tous l’ensemble des informations requises. En effet, la mise en œuvre du CDE basé sur l’IDNC soulève plusieurs défis intéressants, notamment la prolongation de la durée de vie du réseau et la réduction du nombre de transmissions afin de répondre aux besoins des applications temps réel. Par conséquent, contrairement à la plupart des travaux existants concernant l’IDNC, nous nous concentrons non seulement sur le délai, mais également sur l’énergie consommée. En premier lieu, nous étudions le problème de minimisation de l’énergie consommée et du délai au sein d’un petit réseau IDNC coopératif, entièrement connecté et à faible puissance. Nous modélisons le problème en utilisant la théorie des jeux coopératifs de formation de coalitions. Nous proposons un algorithme distribué (appelé “merge and split“) permettant aux nœuds sans fil de s’auto-organiser, de manière distribuée, en coalitions disjointes et indépendantes. L’algorithme proposé garantit une consommation d’énergie réduite et minimise le délai de complétion dans le réseau clustérisé résultant. Par ailleurs, nous ne considérons pas seulement l'énergie de transmission, mais aussi la consommation de l'énergie de calcul des nœuds. De plus, nous nous concentrons sur la question de la mobilité et nous analysons comment, à travers la solution proposée, les nœuds peuvent s’adapter à la topologie dynamique du réseau. Par la suite, nous étudions le même problème au sein d’un réseau large et partiellement connecté. En effet, nous examinons le modèle de CDE multi-sauts. Dans un tel modèle, nous considérons que les nœuds peuvent choisir la puissance d’émission et change ainsi de rayon de transmission et le nombre de voisin avec lesquels il peut entrer en coalition. Pour ce faire, nous modélisons le problème avec un jeu à deux étages; un jeu non-coopératif de contrôle de puissance et un jeu coopératif de formation de coalitions. La solution optimale du premier jeu permet aux joueurs de coopérer à travers des rayons de transmission limités en utilisant la théorie des jeux coopérative. En outre, nous proposons un algorithme distribué “merge and split“ afin de former des coalitions dans lesquelles les joueurs maximisent leurs utilités en termes de délai et de consommation d’énergie. La solution proposée permet la création d’une partition stable avec une interférence réduite et une complexité raisonnable. Nous démontrons que la coopération entre les nœuds au sein du réseau résultant, permet de réduire considérablement la consommation d’énergie par rapport au modèle coopératif optimal qui maintient le rayon de transmission maximal. / With significantly growing number of smart low-power devices during recent years, the issue of energy efficiency has taken an increasingly essential role in the communication systems’ design. This thesis aims at designing distributed and energy efficient transmission schemes for wireless networks using game theory and instantly decodable network coding (IDNC) which is a promising network coding subclass. We study the cooperative data exchange (CDE) scenario in which all devices cooperate with each other by exchanging network coded packets until all of them receive all the required information. In fact, enabling the IDNC-based CDE setting brings several challenges such us how to extend the network lifetime and how to reduce the number of transmissions in order to satisfy urgent delay requirements. Therefore, unlike most of existing works concerning IDNC, we focus not only on the decoding delay, but also the consumed energy. First, we investigate the IDNC-based CDE problem within small fully connected networks across energy-constrained devices and model the problem using the cooperative game theory in partition form. We propose a distributed merge-and-split algorithm to allow the wireless nodes to self-organize into independent disjoint coalitions in a distributed manner. The proposed algorithm guarantees reduced energy consumption and minimizes the delay in the resulting clustered network structure. We do not only consider the transmission energy, but also the computational energy consumption. Furthermore, we focus on the mobility issue and we analyse how, in the proposed framework, nodes can adapt to the dynamic topology of the network. Thereafter, we study the IDNC-based CDE problem within large-scale partially connected networks. We considerate that each player uses no longer his maximum transmission power, rather, he controls his transmission range dynamically. In fact, we investigate multi-hop CDE using the IDNC at decentralized wireless nodes. In such model, we focus on how these wireless nodes can cooperate in limited transmission ranges without increasing the IDNC delay nor their energy consumption. For that purpose, we model the problem using a two-stage game theoretical framework. We first model the power control problem using non-cooperative game theory where users jointly choose their desired transmission power selfishly in order to reduce their energy consumption and their IDNC delay. The optimal solution of this game allows the players at the next stage to cooperate with each other through limited transmission ranges using cooperative game theory in partition form. Thereafter, a distributed multihop merge-and-split algorithm is defined to form coalitions where players maximize their utilities in terms of decoding delays and energy consumption. The solution of the proposed framework determines a stable feasible partition for the wireless nodes with reduced interference and reasonable complexity. We demonstrate that the co-operation between nodes in the multihop cooperative scheme achieves a significant minimization of the energy consumption with respect to the most stable cooperative scheme in maximum transmission range without hurting the IDNC delay.

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

An ever increasing demand for instant and reliable information on modern communication networks forces codewords to operate in a non-asymptotic regime. To achieve reliability for imperfect channels in this regime, codewords need to be retransmitted from receiver to the transmit buffer, aided by a fast feedback mechanism. Large occupancy of this buffer results in longer communication delays. Therefore, codewords need to be designed carefully to reduce transmit queue-length and thus the delay experienced in this buffer. We first study the consequences of physical layer decisions on the transmit buffer occupancy. We develop an analytical framework to relate physical layer channel to the transmit buffer occupancy. We compute the optimal code-rate for finite-length codewords operating over a correlated channel, under certain communication service guarantees. We show that channel memory has a significant impact on this optimal code-rate. Next, we study the delay in small ad-hoc networks. In particular, we find out what rates can be supported on a small network, when each flow has a certain end-to-end service guarantee. To this end, service guarantee at each intermediate link is characterized. These results are applied to study the potential benefits of setting up a network suitable for network coding in multicast. In particular, we quantify the gains of network coding over classic routing for service provisioned multicast communication over butterfly networks. In the wireless setting, we study the trade-off between communications gains achieved by network coding and the cost to set-up a network enabling network coding. In particular, we show existence of scenarios where one should not attempt to create a network suitable for coding. Insights obtained from these studies are applied to design a distributed rate control algorithm in a large network. This algorithm maximizes sum-utility of all flows, while satisfying per-flow end-to-end service guarantees. We introduce a notion of effective-capacity per communication link that captures the service requirements of flows sharing this link. Each link maintains a price and effective-capacity, and each flow maintains rate and dissatisfaction. Flows and links update their respective variables locally, and we show that their decisions drive the system to an optimal point. We implemented our algorithm on a network simulator and studied its convergence behavior on few networks of practical interest.

In this study, the effect of implementing Network Coding on the aggregated throughput in Wireless Mesh Networks, was examined. Wireless Mesh Networks (WMNs) are multiple hop wireless networks, where routing through any node is possible. The implication of this characteristic, is that messages flow across the points where it would have been terminated in conventional wireless networks. User nodes in conventional wireless networks only transmit and receive messages from an Access Point (AP), and discard any messages not intended for them. The result is an increase in the volume of network traffic through the links of WMNs. Additionally, the dense collection of multiple RF signals propagating through a shared wireless medium, contributes to the situation where the links become saturated at levels below their capacity. The need exists to examine methods that will improve the utilisation of the shared wireless medium in WMNs. Network Coding is a coding and decoding technique at the network level of the OSI stack, aimed to improve the boundaries of saturated links. The technique implies that the bandwidth is simultaneously shared amongst separate message flows, by combining these flows at common intermediate nodes. The number of transmissions needed to convey information through the network, is decreased by Network Coding. The result is in an improvement of the aggregated throughput. The research approach followed in this dissertation, includes the development of a model that investigates the aggregated throughput performance of WMNs. The scenario of the model, followed a typical example of indoors WMN implementations. Therefore, the physical environment representation of the network elements, included an indoors log–distance path loss channel model, to account for the different effects such as: power absorption through walls; and shadowing. Network functionality in the model was represented through a network flow programming problem. The problem was concerned with determining the optimal amount of flow represented through the links of the WMN, subject to constraints pertaining to the link capacities and mass balance at each node. The functional requirements of the model stated that multiple concurrent sessions were to be represented. This condition implied that the network flow problem had to be a multi–commodity network flow problem. Additionally, the model requirements stated that each session of flow should remain on a single path. This condition implied that the network flow problem had to be an integer programming problem. Therefore, the network flow programming problem of the model was considered mathematically equivalent to a multi–commodity integer programming problem. The complexity of multi–commodity integer programming problems is NP–hard. A heuristic solving method, Simulated Annealing, was implemented to solve the goal function represented by the network flow programming problem of the model. The findings from this research provide evidence that the implementation of Network Coding in WMNs, nearly doubles the level of the calculated aggregated throughput values. The magnitude of this throughput increase, can be further improved by additional manipulation of the network traffic dispersion. This is achieved by utilising link–state methods, rather than distance vector methods, to establish paths for the sessions of flow, present in the WMNs. / Thesis (M.Ing. (Computer and Electronical Engineering))--North-West University, Potchefstroom Campus, 2012.

In this study, the effect of implementing Network Coding on the aggregated throughput in Wireless Mesh Networks, was examined. Wireless Mesh Networks (WMNs) are multiple hop wireless networks, where routing through any node is possible. The implication of this characteristic, is that messages flow across the points where it would have been terminated in conventional wireless networks. User nodes in conventional wireless networks only transmit and receive messages from an Access Point (AP), and discard any messages not intended for them. The result is an increase in the volume of network traffic through the links of WMNs. Additionally, the dense collection of multiple RF signals propagating through a shared wireless medium, contributes to the situation where the links become saturated at levels below their capacity. The need exists to examine methods that will improve the utilisation of the shared wireless medium in WMNs. Network Coding is a coding and decoding technique at the network level of the OSI stack, aimed to improve the boundaries of saturated links. The technique implies that the bandwidth is simultaneously shared amongst separate message flows, by combining these flows at common intermediate nodes. The number of transmissions needed to convey information through the network, is decreased by Network Coding. The result is in an improvement of the aggregated throughput. The research approach followed in this dissertation, includes the development of a model that investigates the aggregated throughput performance of WMNs. The scenario of the model, followed a typical example of indoors WMN implementations. Therefore, the physical environment representation of the network elements, included an indoors log–distance path loss channel model, to account for the different effects such as: power absorption through walls; and shadowing. Network functionality in the model was represented through a network flow programming problem. The problem was concerned with determining the optimal amount of flow represented through the links of the WMN, subject to constraints pertaining to the link capacities and mass balance at each node. The functional requirements of the model stated that multiple concurrent sessions were to be represented. This condition implied that the network flow problem had to be a multi–commodity network flow problem. Additionally, the model requirements stated that each session of flow should remain on a single path. This condition implied that the network flow problem had to be an integer programming problem. Therefore, the network flow programming problem of the model was considered mathematically equivalent to a multi–commodity integer programming problem. The complexity of multi–commodity integer programming problems is NP–hard. A heuristic solving method, Simulated Annealing, was implemented to solve the goal function represented by the network flow programming problem of the model. The findings from this research provide evidence that the implementation of Network Coding in WMNs, nearly doubles the level of the calculated aggregated throughput values. The magnitude of this throughput increase, can be further improved by additional manipulation of the network traffic dispersion. This is achieved by utilising link–state methods, rather than distance vector methods, to establish paths for the sessions of flow, present in the WMNs. / Thesis (M.Ing. (Computer and Electronical Engineering))--North-West University, Potchefstroom Campus, 2012.

Cooperative relaying is a promising diversity achieving technique to provide reliable transmission, high throughput and extensive coverage for wireless networks in a variety of applications. Two-way relaying is a spectrally efficient protocol, providing one solution to overcome the half-duplex loss in one-way relay channels. Moreover, incorporating the multiple-input-multiple-output (MIMO) technology can further improve the spectral efficiency and diversity gain. A lot of related work has been performed on the two-way relay network (TWRN), but most of them assume perfect channel state information (CSI). In a realistic scenario, however, the channel is estimated and the estimation error exists. So in this thesis, we explicitly take into account the CSI error, and investigate its impact on the performance of amplify-and-forward (AF) TWRN where either multiple distributed single-antenna relays or a single multiple-antenna relay station is exploited. For the distributed relay network, we consider imperfect self-interference cancellation at both sources that exchange information with the help of multiple relays, and maximal ratio combining (MRC) is then applied to improve the decision statistics under imperfect signal detection. The system performance degradation in terms of outage probability and average bit-error rate (BER) are analyzed, as well as their asymptotic trend. To further improve the spectral efficiency while maintain the spatial diversity, we utilize the maximum minimum (Max-Min) relay selection (RS), and examine the impact of imperfect CSI on this single RS scheme. To mitigate the negative effect of imperfect CSI, we resort to adaptive power allocation (PA) by minimizing either the outage probability or the average BER, which can be cast as a Geometric Programming (GP) problem. Numerical results verify the correctness of our analysis and show that the adaptive PA scheme outperforms the equal PA scheme under the aggregated effect of imperfect CSI. When employing a single MIMO relay, the problem of robust MIMO relay design has been dealt with by considering the fact that only imperfect CSI is available. We design the MIMO relay based upon the CSI estimates, where the estimation errors are included to attain the robust design under the worst-case philosophy. The optimization problem corresponding to the robust MIMO relay design is shown to be nonconvex. This motivates the pursuit of semidefinite relaxation (SDR) coupled with the randomization technique to obtain computationally efficient high-quality approximate solutions. Numerical simulations compare the proposed MIMO relay with the existing nonrobust method, and therefore validate its robustness against the channel uncertainty. / Graduate