This study discusses the routing optimization techniques and algorithms for communication networks. Preventing data loss on overloaded communication links and utilizing link bandwidths efficiently are the main problems of traffic engineering. Load balancing and routing problems are solved using both by heuristics such as genetic algorithms, and simulation techniques. These algorithms work on destination-based or flow-based routing techniques and mainly change the link weight system or try to select the best routes set upon K-routes routing table respectively to optimize network utilization. In this study, first a definition of the network routing optimization problem will be made. Then the heuristics to solve the problem will be discussed and finally an analysis of these heuristics will be made on sample network models. This thesis includes a discussion about the performance of different optimization heuristics working as a part of the centralized network load balancing systems.

Die Angebote auf dem Verkehrsmittelmarkt werden immer differenzierter: Innovative Lösungen wie Bike- oder Carsharing- Konzepte schließen aus Angebotsperspektive zunehmend die Lücke zwischen dem reinen Individualverkehr (IV) und dem klassischen öffentlichen Verkehr (ÖV). Ein Umsteigen auf Bus und Bahn kommt jedoch für Autofahrer nur dann in Frage, wenn die gewohnten Mobilitätsmuster im Hinblick u.a. auf Fahrtzeiten, Routen und zusätzliche Erledigungen auch mit dem ÖV gleichermaßen komfortabel möglich sind. Smartphones bieten in diesem Zusammenhang die Möglichkeit, auch von unterwegs aus Routen mit Bus, Bahn, Leihrädern und Carsharing so flexibel und spontan zu planen, dass das Navigieren durch den öffentlichen Verkehr deutlich komfortabler und übersichtlicher wird. Außerdem kann das Abrufen von Informationen über Smartphones dazu beitragen, in öffentlichen Räumen ein Gefühl der Privatheit und der Sicherheit zu erzeugen. Somit wird der Zugang zum öffentlichen Verkehr durch Routenplanungs-Apps für viele Menschen vereinfacht. Das InnoZ hat im Projekt „cairo“ über zwei Jahre die Nutzeranforderungen an ein mobiles Routing für den öffentlichen Verkehr untersucht und dabei auch Änderungen im Zeitverlauf erfasst. Insgesamt konnten damit nicht nur generelle Anforderungen an die technische Ausgestaltung der Routing-App ausgewertet, sondern auch konkrete Informationsbedarfe nach Orten, Wegen oder Verkehrsmitteln bestimmt werden. Die Ergebnisse dieser Studie werden im vorliegenden Baustein vorgestellt. / During recent years, the mobility service market has diversified: Innovative solutions like bike- and carsharing concepts increasingly fill the gap between individual car transport, and public transport. Most car owners, though, will only change to public transport, if travelling becomes as comfortable as car trips in terms of travelling routines, times, activities, and routes. In this context, smartphones indeed facilitate the access to public transport by enabling a flexible and spontaneous planning of bus, train, bike rental and carsharing trips “on the go”. Moreover, smartphones can enhance the feeling of security and privacy in public spaces in general. As a consequencee, navigating through the public transport network becomes much easier and comfortable for many user groups. Within the “cairo” project, researchers at InnoZ have assessed user preferences on mobile routing over a period of two years, and could therefore also detect changes over time. Apart from general requirements on technical functions, actual information needs with regards to location, transport modes, or routes have been a central subject of research. The results of this study are summarized in this Baustein.

The exponential growth of Internet applications has created new challenges for the control and administration of large-scale networks, which consist of heterogeneous elements under dynamically changing traffic conditions. These emerging applications need guaranteed service levels, beyond those supported by best-effort networks, to deliver the intended services to the end user. Several models have been proposed for a Quality of Service (QoS) framework that can provide the means to transport these services. It is desirable to find efficient routing strategies that can meet the strict routing requirements of these applications. QoS routing is considered as one of the major components of the QoS framework in communication networks. In QoS routing, paths are selected based upon the knowledge of resource availability at network nodes and the QoS requirements of traffic. Several QoS routing schemes have been proposed that differ in the way they gather information about the network state and the way they select paths based on this information. The biggest downside of current QoS routing schemes is the frequent maintenance and distribution of global state information across the network, which imposes huge communication and processing overheads. Consequently, scalability is a major issue in designing efficient QoS routing algorithms, due to the high costs of the associated overheads. Moreover, inaccuracy and staleness of global state information is another problem that is caused by relatively long update intervals, which can significantly deteriorate routing performance. Localized QoS routing, where source nodes take routing decisions based solely on statistics collected locally, was proposed relatively recently as a viable alternative to global QoS routing. It has shown promising results in achieving good routing performance, while at the same time eliminating many scalability related problems. In localized QoS routing each source¿destination pair needs to determine a set of candidate paths from which a path will be selected to route incoming flows. The goal of this thesis is to enhance the scalability of QoS routing by investigating and developing new models and algorithms based on the localized QoS routing approach. For this thesis, we have extensively studied the localized QoS routing approach and demonstrated that it can achieve a higher routing performance with lower overheads than global QoS routing schemes. Existing localized routing algorithms, Proportional Sticky Routing (PSR) and Credit-Based Routing (CBR), use the blocking probability of candidate paths as the criterion for selecting routing paths based on either flow proportions or a crediting mechanism, respectively. Routing based on the blocking probability of candidate paths may not always reflect the most accurate state of the network. This has motivated the search for alternative localized routing algorithms and to this end we have made the following contributions. First, three localized bandwidth-constrained QoS routing algorithms have been proposed, two are based on a source routing strategy and the third is based on a distributed routing strategy. All algorithms utilize the quality of links rather than the quality of paths in order to make routing decisions. Second, a dynamic precautionary mechanism was used with the proposed algorithms to prevent candidate paths from reaching critical quality levels. Third, a localized delay-constrained QoS routing algorithm was proposed to provide routing with an end-to-end delay guarantee. We compared the performance of the proposed localized QoS routing algorithms with other localized and global QoS routing algorithms under different network topologies and different traffic conditions. Simulation results show that the proposed algorithms outperform the other algorithms in terms of routing performance, resource balancing and have superior computational complexity and scalability features. / Umm AlQura University, Saudi Arabia

Organizations providing home care services are inclined to optimize their activities in order to meet the constantly increasing demand for home care. In this context, home care providers are confronted with multiple, often conflicting, objectives such as minimizing their operating costs while maximizing the service level offered to their clients by taking into account their preferences. This paper is the first to shed some light on the trade-off relationship between these two objectives by modeling the home care routing and scheduling problem as a bi-objective problem. The proposed model accounts for qualifications, working regulations and overtime costs of the nurses, travel costs depending on the mode of transportation, hard time windows, and client preferences on visit times and nurses. A distinguishing characteristic of the problem is that the scheduling problem for a single route is a biobjective problem in itself, thereby complicating the problem considerably. A metaheuristic algorithm, embedding a large neighborhood search heuristic in a multi-directional local search framework, is proposed to solve the problem. Computational experiments on a set of benchmark instances based on reallife data are presented. A comparison with exact solutions on small instances shows that the algorithm performs well. An analysis of the results reveals that service providers face a considerable trade-off between costs and client convenience. However, starting from a minimum cost solution, the average service level offered to the clients may already be improved drastically with limited additional costs. (authors' abstract)

We present a hybrid optimization algorithm for mixed-integer linear programming, embedding both heuristic and exact components. In order to validate it we use the periodic vehicle routing problem (PVRP) as a case study. This problem consists of determining a set of minimum cost routes for each day of a given planning horizon, with the constraints that each customer must be visited a required number of times (chosen among a set of valid day combinations), must receive every time the required quantity of product, and that the number of routes per day (each respecting the capacity of the vehicle) does not exceed the total number of available vehicles. This is a generalization of the well-known vehicle routing problem (VRP). Our algorithm is based on the linear programming (LP) relaxation of a set-covering-like integer linear programming formulation of the problem, with additional constraints. The LP-relaxation is solved by column generation, where columns are generated heuristically by an iterated local search algorithm. The whole solution method takes advantage of the LP-solution and applies techniques of fixing and releasing of the columns as a local search, making use of a tabu list to avoid cycling. We show the results of the proposed algorithm on benchmark instances from the literature and compare them to the state-of-the-art algorithms, showing the effectiveness of our approach in producing good quality solutions. In addition, we report the results on realistic instances of the PVRP introduced in Pacheco et al. (2011) [24] and on benchmark instances of the periodic traveling salesman problem (PTSP), showing the efficacy of the proposed algorithm on these as well. Finally, we report the new best known solutions found for all the tested problems. (authors' abstract)

International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / An agile RF routing system has been developed which utilizes phasing techniques to direct signal power to any one of four orthogonally mounted antennae, or either set of two antennae mounted 180° apart on a launch vehicle. The system has been integrated into a telemetry transmitter and has shown superior performance to traditional methods of antennae switching. The unit is self-correcting to maintain maximum RF power at the desired antenna port(s) across a dynamic mission environment. Due to its low loss and high reliability, this method of antennae switching provides a robust RF link.

Wireless Mesh Networks (WMNs) are bringing revolutionary change in the field of wireless networking. It is a trustworthy technology in applications like broadband home networking, network management and latest transportation systems. WMNs consist of mesh routers, mesh clients and gateways. It is a special kind of wireless Ad-hoc networks. One of the issues in WMNs is resource management which includes routing and for routing there are particular routing protocols that gives better performance when checked with certain parameters. Parameters in WMNs include delay, throughput, network load etc. There are two types of routing protocols i.e. reactive protocols and proactive protocols. Three routing protocols AODV, DSR and OLSR have been tested in WMNs under certain parameters which are delay, throughput and network load. The testing of these protocols will be performed in the Optimized Network Evaluation Tool (OPNET) Modeler 14.5. The obtained results from OPNET will be displayed in this thesis in the form of graphs. This thesis will help in validating which routing protocol will give the best performance under the assumed conditions. Moreover this thesis report will help in doing more research in future in this area and help in generating new ideas in this research area that will enhance and bring new features in WMNs. / Wireless Mesh Networks (WMNs) bringar revolutionerande förändring inom området för trådlösa nätverk. Det är en pålitlig teknik i tillämpningar såsom bredband hemma nätverk, nätverkshantering och senaste transportsystem. WMNs består av mesh routrar, kunder mesh och gateways. Det är en speciell typ av trådlöst ad-hoc-nätverk. En av frågorna i WMNs är resurshushållning som inkluderar routing och routing det finns särskilda routingprotokoll som ger bättre prestanda vid kontroll med vissa parametrar. Parametrar i WMNs omfatta dröjsmål, genomströmning, belastningen på nätet etc. Det finns två typer av routingprotokoll dvs reaktiva protokoll och proaktiva protokoll. Tre routingprotokoll AODV, DSR och OLSR har testats i WMNs under vissa parametrar som är försenade, genomströmning och belastningen på nätet. Testning av dessa protokoll kommer att utföras i den optimerade Network Evaluation Tool (OPNET) Modeler 14.5. De erhållna resultaten från OPNET kommer att visas i denna avhandling i form av grafer. Denna uppsats kommer att bidra till att godkänna vilka routingprotokoll kommer att ge bäst resultat enligt den antagna förhållanden. Dessutom kommer denna uppsats rapport kommer att bidra till att göra mer forskning i framtiden på detta område och bidra till att generera nya idéer inom detta forskningsområde som kommer att öka och att nya funktioner i WMNs. / +46762749245

As the semiconductor technology scales into deeper sub-micron domain, billions of transistors can be used on a single system-on-chip (SOC) makes interconnection optimization more important roughly for two reasons. First, congestion, power, timing in routing and buffering requirements make inter- connection optimization more and more challenging. Second, gate delay get- ting shorter while the RC delay gets longer due to scaling. Study of interconnection construction and optimization algorithms in real industry flows and designs ends up with interesting findings. One used to be overlooked but very important and practical problem is how to utilize over- the-block routing resources intelligently. Routing over large IP blocks needs special attention as there is almost no way to insert buffers inside hard IP blocks, which can lead to unsolvable slew/timing violations. In current design flows we have seen, the routing resources over the IP blocks were either dealt as routing blockages leading to a significant waste, or simply treated in the same way as outside-the-block routing resources, which would violate the slew constraints and thus fail buffering. To handle that, this work proposes a novel buffering-aware over-the- block rectilinear Steiner minimum tree (BOB-RSMT) algorithm which helps reclaim the “wasted” over-the-block routing resources while meeting user-specified slew constraints. Proposed algorithm incrementally and efficiently migrates initial tree structures with buffering-awareness to meet slew constraints while minimizing wire-length. Moreover, due to the fact that timing optimization is important for the VLSI design, in this work, timing-driven over-the-block rectilinear Steiner tree (TOB-RST) is also studied to optimize critical paths. This proposed TOB-RST algorithm can be used in routing or post-routing stage to provide high-quality topologies to help close timing. Then a follow-up problem emerges: how to accomplish the whole routing with over-the-block routing resources used properly. Utilizing over-the- block routing resources could dramatically improve the routing solution, yet require special attention, since the slew, affected by different RC on different metal layers, must be constrained by buffering and is easily violated. Moreover, even of all nets are slew-legalized, the routing solution could still suffer from heavy congestion problem. A new global router, BOB-Router, is to solve the over-the-block global routing problem through minimizing overflows, wire-length and via count simultaneously without violating slew constraints. Based on my completed works, BOB-RSMT and BOB-Router tremendously improve the overall routing and buffering quality. Experimental results show that proposed over-the-block rectilinear Steiner tree construction and routing completely satisfies the slew constraints and significantly outperforms the obstacle-avoiding rectilinear Steiner tree construction and routing in terms of wire-length, via count and overflows. / text

在如同全IP網路(ALL-IP Network)這類的分封交換網路(packet-switching network)中提供具時效性的服務(time-sensitive services)必須嚴格的控制時間。路由規劃是網路管理中重要的一環，所以這類網路的路由規劃必須考慮網路延遲。然而就我們目前所知，多數的傳統路由演算法並不以傳輸延遲(path delay)為主要考量因素；例外少數有考量延遲時間的演算法也僅限於鍊結延遲(link delay)，而未考慮節點延遲(node delay)。此乃肇因於以往頻寬的成本極為昂貴，因而造成演算法設計者在設計時會儘可能有效利用頻寬，如此免不了會犧牲傳遞速度。在過去幾年間，由於光通訊技術的提升，網路頻寬的成長速度遠遠已超過路由器(router)處理能力的成長。在這樣不對等的成長比例驅使下，節點延遲，亦即路由器處理封包時所耗時間，在傳輸延遲中所佔的比例亦隨之快速增長。也因此我們認為，在為高速封包交換網路設計路由演算法時，必須同時考量鍊結延遲和節點延遲。在本論文中，我們設計了一個訊務流為基礎的路由演算法(flow-based routing algorithm)，KLONE，來驗證我們的論點。在規劃路由時，KLONE會把發生在鍊結和節點上的延遲時間一併列入計算，並以全體延遲時間為主要考量。透過我們反覆的測試實驗，我們發現其較之於常用的OSPF演算法，可以在效能上有30%的勝出。藉此，我們的論點得到初步的證實。 / Providing time sensitive services becomes an essential task for some packet-switching networks such as All-IP networks, which will carry all the traffics supported by both circuit-switching and packet-switching networks. To fulfill this demand, such networks require a delay sensitive routing mechanism to provide time-related QoS for delay sensitive services. However, most of traditional routing algorithms do not take delay time as a major concern. Only a few are designed for time sensitive services. These time sensitive routing algorithms are designed at the time when the link bandwidth is the only scarce resource. As the bandwidth of communication links grows rapidly in recent years due to the advance of optical communication technologies, link bandwidth is no longer the only scarce resource. The processing speed of nodes, for example, routers, becomes another critical source of delay time. In this thesis, we designed a new flow-based routing algorithm, the KLONE algorithm, which takes average delay time as its minimization objective and takes both nodes and links as delay components. Through an intensive evaluation using simulation method, we demonstrate that a routing algorithm that considers both link and node delay might outperform the traditional OSPF algorithm.

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