The Quality of Service (QoS) routing approach is gaining an increasing interest in the Internet community due to the new emerging Internet applications such as real-time multimedia applications. These applications require better levels of quality of services than those supported by best effort networks. Therefore providing such services is crucial to many real time and multimedia applications which have strict quality of service requirements regarding bandwidth and timeliness of delivery. QoS routing is a major component in any QoS architecture and thus has been studied extensively in the literature. Scalability is considered one of the major issues in designing efficient QoS routing algorithms due to the high cost of QoS routing both in terms of computational effort and communication overhead. Localized quality of service routing is a promising approach to overcome the scalability problem of the conventional quality of service routing approach. The localized quality of service approach eliminates the communication overhead because it does not need the global network state information. The main aim of this thesis is to contribute towards the localised routing area by proposing and developing some new models and algorithms. Toward this goal we make the following major contributions. First, a scalable and efficient QoS routing algorithm based on a localised approach to QoS routing has been developed and evaluated. Second, we have developed a path selection technique that can be used with existing localized QoS routing algorithms to enhance their scalability and performance. Third, a scalable and efficient hierarchical QoS routing algorithm based on a localised approach to QoS routing has been developed and evaluated.

Os objetivos desta monografia foram analisar as propriedades de topologias de redes complexas, analisar as potencialidades e comparar desempenho de softwares gratuitos de geração de topologias e simular roteamento de tráfego em redes de telecomunicações. As principais topologias analisadas foram a regular, aleatória e livre de escala. As propriedades topológicas incluem o grau nodal, a distribuição de grau, o coeficiente de agrupamento, o comprimento médio do caminho, além do efeito mundo pequeno. Foram avaliadas as potencialidades de três ferramentas gratuitas de geração e análise de redes, o B-A, Pajek e NetLogo. Como exemplos de aplicação em redes de telecomunicações, com destaque para redes ópticas utilizando técnica de multiplexação por divisão de comprimento de onda, foram implementados os seguintes algoritmos de roteamento de tráfego: roteamento fixo com alocação de comprimento de onda sequencial fixa e roteamento adaptativo com alocação de comprimento de onda menos usado, mais usado, aleatória e busca exaustiva. O desempenho dos algoritmos de roteamento e alocação de comprimentos de onda de modo nas topologias analisadas foram comparados. / The purposes of this master\'s thesis are to analyze the properties of complex network topologies, analyze and compare the performance of free software for generating topologies and simulate traffic routing in telecommunication networks. The main topologies analyzed were the regular, random and scale-free. The topological properties include the nodal degree, the distribution degree, clustering coefficient, average path length and small-world effect. The performance of the free softwares B-A, Pajek and Netlogo were evaluated. As examples of application in telecommunication networks, especially for optical networks using wavelength division multiplexing technique, the following routing traffic algorithms were implemented: Fixed routing with first-fit wavelength assignment and adaptive routing with least used wavelength assignment, most used, random and exhaustive search. The performance of algorithms for routing and wavelength allocation employed in the analyzed topologies was compared.

The routing strategy used in today's Internet is best-effort service, where all data packets are treated equally. This type of service is not suited for applications such as video conferencing, and video on demand, that requires the availability of certain resources (such as bandwidth) to be guaranteed for them to function properly. The routing in this context, called Quality-of-Service (QoS) Routing, is the problem of finding suitable paths that meet the application's resource requirements. The majority of proposed QoS routing schemes operate by maintaining the global state of the network, and using this knowledge to compute the QoS route. However, all these schemes suffer from the inherent drawback of scalability, because of the need for each node to collect state information about the complete network. The other type of QoS routing schemes do not maintain network state information, but instead flood the network with QoS connection establishment requests. This type of scheme suffers from excessive message overhead during QoS connection establishment. In this thesis, we present a new QoS routing algorithm that is a combination of the above-mentioned two schemes (i.e., global state and flooding based). The algorithm aims at minimizing the message overhead associated with these two schemes and still maintaining the positive aspects of both of them. The basic idea of the algorithm is: to reach to a destination, the path(s) will always pass through a specific set of intermediate nodes. The algorithm discovers such intermediate nodes (limited by a hop count threshold value needed to reach there). When a QoS connection request arrives at a node, it selects the feasible path leading to the intermediate node for the requested destination. The QoS connection establishment message (or routing message) is forwarded along this path. When the message arrives at the intermediate node, the further path is decided through same logic. To decide the path that leads to the intermediate node, the algorithm maintains the link state related to these intermediate nodes, and link state updates are restricted only with regard to these intermediate nodes. Because of this restriction in link state updation, one has less message overhead, compared to the global state based routing scheme. Further, the algorithm tries to group these intermediate nodes in such a way that the routing message need be sent to only one of the grouped intermediate nodes, and still makes sure that all the possible paths are covered. Therefore, one has a reduced message overhead because of grouping.

Os objetivos desta monografia foram analisar as propriedades de topologias de redes complexas, analisar as potencialidades e comparar desempenho de softwares gratuitos de geração de topologias e simular roteamento de tráfego em redes de telecomunicações. As principais topologias analisadas foram a regular, aleatória e livre de escala. As propriedades topológicas incluem o grau nodal, a distribuição de grau, o coeficiente de agrupamento, o comprimento médio do caminho, além do efeito mundo pequeno. Foram avaliadas as potencialidades de três ferramentas gratuitas de geração e análise de redes, o B-A, Pajek e NetLogo. Como exemplos de aplicação em redes de telecomunicações, com destaque para redes ópticas utilizando técnica de multiplexação por divisão de comprimento de onda, foram implementados os seguintes algoritmos de roteamento de tráfego: roteamento fixo com alocação de comprimento de onda sequencial fixa e roteamento adaptativo com alocação de comprimento de onda menos usado, mais usado, aleatória e busca exaustiva. O desempenho dos algoritmos de roteamento e alocação de comprimentos de onda de modo nas topologias analisadas foram comparados. / The purposes of this master\'s thesis are to analyze the properties of complex network topologies, analyze and compare the performance of free software for generating topologies and simulate traffic routing in telecommunication networks. The main topologies analyzed were the regular, random and scale-free. The topological properties include the nodal degree, the distribution degree, clustering coefficient, average path length and small-world effect. The performance of the free softwares B-A, Pajek and Netlogo were evaluated. As examples of application in telecommunication networks, especially for optical networks using wavelength division multiplexing technique, the following routing traffic algorithms were implemented: Fixed routing with first-fit wavelength assignment and adaptive routing with least used wavelength assignment, most used, random and exhaustive search. The performance of algorithms for routing and wavelength allocation employed in the analyzed topologies was compared.

With the ever-growing demand for higher data rate in next generation communication systems, researchers are pushing the limits of the existing architecture. Due to the stochastic nature of communication channels, most systems use some form of adaptive methods to adjust the transmitting parameters and allocation of resources in order to overcome channel variations and achieve optimal throughput. We will study four cases of adaptive transmission and dynamic resource allocation in collaborative systems that are practically significant. Firstly, we study hybrid automatic repeat request (HARQ) techniques that are widely used to handle transmission failures. We propose HARQ policies that improve system throughput and are suitable for point-to-point, two-hop relay, and multi-user broadcast systems. Secondly, we study the effect of having bits of mixed SNR qualities in finite length codewords. We prove that by grouping bits according to their reliability so that each codeword contains homogeneous bit qualities, the finite blocklength capacity of the system is increased. Thirdly, we study the routing and resource allocation problem in multiple collaborative networks. We propose an algorithm that enables collaboration between networks which needs little to no side information shared across networks, but rather infers necessary information from the transmissions. The collaboration between networks provides a significant gain in overall throughput compared to selfish networks. Lastly, we present an algorithm that allocates disjoint transmission channels for our cognitive radio network in the DARPA Spectrum Collaboration Challenge (SC2). This algorithm uses the real-time spectrogram knowledge perceived by the radios and allocates channels adaptively in a crowded spectrum shared with other collaborative networks.

The Quality of Service (QoS) routing approach is gaining an increasing interest in the Internet community due to the new emerging Internet applications such as real-time multimedia applications. These applications require better levels of quality of services than those supported by best effort networks. Therefore providing such services is crucial to many real time and multimedia applications which have strict quality of service requirements regarding bandwidth and timeliness of delivery. QoS routing is a major component in any QoS architecture and thus has been studied extensively in the literature. Scalability is considered one of the major issues in designing efficient QoS routing algorithms due to the high cost of QoS routing both in terms of computational effort and communication overhead. Localized quality of service routing is a promising approach to overcome the scalability problem of the conventional quality of service routing approach. The localized quality of service approach eliminates the communication overhead because it does not need the global network state information. The main aim of this thesis is to contribute towards the localised routing area by proposing and developing some new models and algorithms. Toward this goal we make the following major contributions. First, a scalable and efficient QoS routing algorithm based on a localised approach to QoS routing has been developed and evaluated. Second, we have developed a path selection technique that can be used with existing localized QoS routing algorithms to enhance their scalability and performance. Third, a scalable and efficient hierarchical QoS routing algorithm based on a localised approach to QoS routing has been developed and evaluated.

<p>Network on Chip is a scalable and flexible communication infrastructure for the design of core based System on Chip. Communication performance of a NoC depends heavily on the routing algorithm. Deterministic and adaptive distributed routing algorithms have been advocated in all the current NoC architectural proposals. In this thesis we make a case for the use of source routing for NoCs, especially for regular topologies like mesh. The advantages of source routing include in-order packet delivery; faster and simpler router design; and possibility of mixing non-minimal paths in a mainly minimal routing. We propose a method to compute paths for various communications in such a way that traffic congestion is avoided while ensuring deadlock free routing. We also propose an efficient scheme to encode the paths.</p><p>We developed a tool in Matlab that computes paths for source routing for both general and application specific communications. Depending upon the type of traffic, this tool computes paths for source routing by selecting best routing algorithm out of many routing algorithms. The tool uses a constructive path improvement algorithm to compute paths that give more uniform link load distribution. It also generates different types of traffics. We also developed a simulator capable of simulating source routing for mesh topology NoC. The experiments and simulations which we performed were successful and the results show that the advantages of source routing especially lower packet latency more than compensate its disadvantages. The results also demonstrate that source routing can be a good routing candidate for practical core based SoCs design using network on chip communication infrastructure.</p>

Made available in DSpace on 2016-04-04T18:31:40Z (GMT). No. of bitstreams: 1 Paulo Cesar Barreto da Silva.pdf: 3934588 bytes, checksum: cbbb71074cd6c370e06fd00f5d3eabce (MD5) Previous issue date: 2014-02-05 / New optical wavelength division multiplexing (WDM) networks are expected to utilize multiple bit rate channels. Moreover, each individual channels may carry over 200 Gb/s and occupy a bandwidth that exceeds the 50-GHz WDM fixed grid. In this scenario, spectral efficiency becomes an important issue and new channel allocation schemes need to be considered. An attractive solution for this problem is the utilization of a WDM grid with variable channel spacing, in the so-called elastic optical network (EON) approach. The main goal of this work is to propose algorithms to solve the spectral efficiency issue in emerging optical WDM networks. Such proposals are divided in two classes. The first one consists of allocating different spectral blocks for channels with different bit rates; this is named as the spectrum block division (SBD) scheme. The second class of our proposals is based on EON schemes. In this case, not only the enhancement of a previously reported algorithm, the Maximize Total Link Spectrum Consecutiveness (MTLSC) algorithm, is considered but also a new algorithm, the Shortest Path with Maximum number of Free Frequency Slot Units (SPMFF) is proposed. Another contribution of this work is the development of an EON simulator, called EONSim, based on JAVA programming language. This simulator was properly tested and reproduced the results of literature papers within a very good accuracy. All of our results were obtained with the aid of EONSim and suggest that the proposed algorithms yield a bandwidth occupation gain that varies from 7 to 18% higher than the one provided by traditional first-fit (FF) algorithms. Such algorithms also provide a blocking probability that is 2 to 8% lower than in FF strategy. On the other hand, it is found that algorithms with higher spectral efficiency use an average number of hops that is up to 16% higher than those necessary for algorithms that do not take bandwidth into account in channel allocation. / Novas redes ?pticas de multiplexa??o por divis?o de comprimento de onda (Wavelength Division Multiplexing, WDM) podem utilizar v?rios canais com taxas diferentes de bits. Al?m disso, cada um dos canais individuais pode transportar mais de 200 Gb/s e ocupar uma largura de banda que excede a grade fixa de 50 GHz da rede WDM. Neste cen?rio, a efici?ncia espectral torna-se uma quest?o importante e novos esquemas de aloca??o de canais precisam ser considerados. Uma solu??o atrativa para este problema ? a utiliza??o de uma rede WDM com espa?amento de canal vari?vel, na abordagem chamada rede ?ptica el?stica (EON). O principal objetivo do presente trabalho ? propor algoritmos para resolver a quest?o da efici?ncia espectral em redes ?pticas WDM emergentes. Tais propostas s?o divididas em duas classes. A primeira consiste em alocar diferentes blocos de espectro para canais com diferentes taxas de bits, o que ? apontado como esquema de divis?o de blocos de espectro (Spectrum Block Division, SBD). A segunda classe ? baseada em esquemas de EON. Neste caso, n?o s? o aperfei?oamento de um algoritmo previamente descrito por WANG (2012), o algoritmo Maximize Total Link Spectrum Consecutiveness (MTLSC), ? considerado, mas tamb?m um novo algoritmo, o Shortest Path with Maximum number of Free Frequency Slot Units (SPMFF) ? proposto. Outra contribui??o deste trabalho ? o desenvolvimento de um simulador de EON, chamado EONSim, com base na linguagem de programa??o JAVA. Este simulador foi devidamente testado e foram reproduzidos os resultados de WANG (2012) dentro de uma precis?o muito boa. Todos os resultados foram obtidos com a ajuda de EONSim e sugerem que os algoritmos propostos produzem um ganho de ocupa??o de banda, que varia de 7 a 18% mais elevada do que a fornecida pelo tradicional algoritmo First Fit (FF). Tais algoritmos tamb?m proporcionam uma probabilidade de bloqueio, que ? de 2 a 8% mais baixa do que na estrat?gia FF. Por outro lado, verifica-se que os algoritmos de melhor ocupa??o espectral utilizam um n?mero m?dio de saltos at? 16% mais elevado do que os necess?rios para os algoritmos de menor caminho, que n?o levam em conta a largura de banda de atribui??o de canal.

QoS routing is one of the major building blocks for supporting QoS in communication networks and, hence, a necessary component of future communication networks. Bandwidth- Constrained Routing Algorithm (BCRA) may help to satisfy QoS requirements such as end-to-end delay, delay-jitter etc when WFQ-like (Weighted Fair Queuing) scheduling mechanisms are deployed. The existing algorithms for bandwidth constrained routing suffer from high message overhead and have a high computational and space complexity. The work presented in the thesis, therefore, focuses on the different techniques that an be used to reserve bandwidth for a unicast connection with low protocol overhead in terms of number of messages. We have compared the performance of the proposed routing algorithms using simulation studies with other bandwidth constrained routing algorithms. The call blocking ratio and message overhead have been used as the performance metric to compare the proposed algorithm with the existing ones. We present three source routing algorithms for unicast connections satisfying the band- width requirement. The first two routing algorithms are based on the partitioning of the network. The link-state broadcasts are limited to the partition. In the first algorithm, the source node queries the other partitions for the state information on a connection request and computes the path based on the information received from the other partitions. The second algorithm is based on state aggregation. The aggregated state of other partitions is maintained at every node. The source node finds a feasible path based on the aggregated information. The path is expanded in every partition, if required, at the time of resource reservation. The third QoS routing algorithm uses the Distance Vector Tables to find a route for a connection. If the shortest path satisfies the bandwidth requirement, then it is selected; otherwise a random deviation is taken at the point where bandwidth requirement is not satisfied and shortest path algorithm is again followed. In all the three algorithms presented, the packets carry the entire path information to the destination node. Therefore, no per connection information is required to be maintained at the intermediate nodes. Simulation results indicate that the proposed algorithms indeed help educing the protocol overhead considerably, and at the same time they give comparable or better performance in terms of resource utilization across a wide range of workloads.

Recent advances in VLSI technology, and wireless communication have enabled the development of tiny, low-cost sensor nodes that communicate over short distances. These sensor nodes, which consist of sensing, data processing, and wireless communication capabilities, suggest the idea of sensor networks based on collaborative effort of a large number of sensor nodes. Sensor networks hold the promise for numerous applications such as intrusion detection, weather monitoring, security and tactical surveillance, distributed computing, and disaster management. Several new protocols and algorithms have been proposed in the recent past in order to realize these applications. In this thesis, we consider the problem of routing in Wireless Sensor Networks (WSNs). Routing is a challenging problem in WSNs due to the inherent characteristics which distinguish these networks from the others. Several routing algorithms have been proposed for WSNs, each considering a specific network performance objective such as long network lifetime (ChangandTassiulas,2004), end-to-end delay guarantees (T.Heetal,2003), and data fusion (RazvanCristescuetal,2005) etc. In this thesis, we utilize the Potential-based Routing Paradigm to develop routing algorithms for different performance objectives of interest in WSNs. The basic idea behind the proposed approach is to assign a scalar called the potential to every sensor node in the network. Data is then forwarded to the neighbor with highest potential. Potentials cause the data to flow along certain paths. By defining potential fields appropriately, one can cause data to flow along preferred paths, so that the given performance objective is achieved. We have demonstrated the usefulness of this approach by considering three performance objectives, and defining potentials appropriately in each case. The performance objectives that we have considered are (i) maximizing the time to network partition, (ii) maximizing the packet delivery ratio, and (iii) Data fusion. In an operational sensor network, sensor nodes’ energy levels gradually deplete, leading eventually to network partition. A natural objective is to route packets in such a way that the time to network partition is maximized. We have developed a potential function for this objective. We analyzed simple network cases and used the insight to develop a potential function applicable to any network. Simulation results showed that considerable improvements in time to network partition can be obtained compared to popular approaches such as maximum lifetime routing, and shortest hop count routing. In the next step, we designed a potential function that leads to routes with high packet delivery ratios. We proposed a “channel-state aware” potential definition for a simple 2-relay network and performed a Markov-chain based analysis to obtain the packet delivery ratio. Considerable improvement was observed compared to a channel-state-oblivious policy. This motivated us to define a channel-state-dependent potential function for a general network. Simulation results showed that for a relatively slowly changing wireless network, our approach can provide up to 20% better performance than the commonly-used shortest-hop-count routing. Finally, we considered the problem of correlated data gathering in sensor networks. The routing approach followed in literature is to construct a spanning tree rooted at the sink. Every node in the tree aggregates its data with the data from its children in order to reduce the number of transmitted bits. Due to this fact, the total energy cost of the data collection task is a function of the underlying tree structure. Noting that potential based routing schemes also result in a tree structure, we present a potential definition that results in the minimum energy cost tree under some special conditions. Specifically, we consider a scenario in which sensor nodes’ measurements are quantized to K values. The task at the sink is to construct a histogram of measurements of all sensor nodes. Sensor nodes do not directly send their measurements to sink. Instead, they construct a temporary histogram using the data from its children and forward it to its parent node in the tree. We present a potential definition that results in the minimum energy cost tree under some conditions on sensor nodes’ measurements. We include both the transmission energy cost as well as the energy cost associated with the aggregation process.