A heuristic for fault-tolerance provisioning in multi-radio hybrid wireless-optical broadband access network

The wireless-optical broadband-access network (WOBAN) architecture has been proposed as a flexible and cost-effective solution for future access networks. However, for WOBANs to provide geographically continuous wireless coverage it is necessary to integrate fault-tolerance in the design of such networks. In this paper we develop a heuristic algorithm to solve the problem of planning a wireless and optical fault-tolerant multi-radio WOBAN, considering any fault-tolerance scenario (e.g. some nodes/links/region only), while making an efficient reuse of spectrum

A Multi-Objective Optimization Approach for Fault-Tolerance Provisioning in Multi-Radio Hybrid Wireless-Optical Broadband Access Networks

Wireless-optical broadband-access networks (WOBANs), currently being deployed at the access section, should integrate fault-tolerance in their design so that geographically continuous wireless coverage can be provided without service breaks. In this paper we propose a joint wireless and optical fault-tolerance planning approach for WOBANs having multiple radios in each router. The problem is formalized, as a multi-objective optimization problem, and a heuristic is proposed to solve this problem. Two fault-tolerance planning scenarios, where gateways are arranged differently in the risk groups, are analysed. It is shown that multi-radio routers can be exploited to improve the performance of WOBANs, providing wireless and optical fault-tolerance. Results also indicate that, when using our approach, a small increase in the number of radios can significantly decrease the total capacity required to provide any degree of fault-tolerance.This work was supported by the Foundation for Science and Technology from Portugal within CEOT (Center for Electronic, Optoelectronic and Telecommunications) and by the project PTDC/EEA-TEL/71678/2006

Backup Radio Placement for Optical Fault Tolerance in Hybrid Wireless-Optical Broadband Access Networks

Master'sMASTER OF ENGINEERIN

DYNAMIC ROUTING WITH CROSS-LAYER ADAPTATIONS FOR MULTI-HOP WIRELESS NETWORKS

In recent years there has been a proliferation of research on a number of wireless multi-hop networks that include mobile ad-hoc networks, wireless mesh networks, and wireless sensor networks (WSNs). Routing protocols in such networks are of- ten required to meet design objectives that include a combination of factors such as throughput, delay, energy consumption, network lifetime etc. In addition, many mod- ern wireless networks are equipped with multi-channel radios, where channel selection plays an important role in achieving the same design objectives. Consequently, ad- dressing the routing problem together with cross-layer adaptations such as channel selection is an important issue in such networks. In this work, we study the joint routing and channel selection problem that spans two domains of wireless networks. The first is a cost-effective and scalable wireless-optical access networks which is a combination of high-capacity optical access and unethered wireless access. The joint routing and channel selection problem in this case is addressed under an anycasting paradigm. In addition, we address two other problems in the context of wireless- optical access networks. The first is on optimal gateway placement and network planning for serving a given set of users. And the second is the development of an analytical model to evaluate the performance of the IEEE 802.11 DCF in radio-over- fiber wireless LANs. The second domain involves resource constrained WSNs where we focus on route and channel selection for network lifetime maximization. Here, the problem is further exacerbated by distributed power control, that introduces addi- tional design considerations. Both problems involve cross-layer adaptations that must be solved together with routing. Finally, we present an analytical model for lifetime calculation in multi-channel, asynchronous WSNs under optimal power control

Dynamic frequency assignment fiber-wireless access networks

Dissertação de mestrado, Engenharia Informática, Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2014This dissertation focuses on the Fiber-Wireless (FiWi) access networks, more specifically on the problem of assigning frequencies to maintain connectivity and acceptable standards of service quality in face of changes in the pattern of traffic flows in the network. Mainly realized on radio and fiber technologies, these networks form an hybrid architecture comprising an optical section and a wireless section that provides a feasible paradigm for high bandwidth and ubiquity at new access network areas. In these FiWi scenarios, in particular when multi-radio and multi-channel configurations are used, an effective frequency assignment should be done to radios so that higher throughput and low delay can be obtained and the best of such architectures is achieved. However, traffic conditions may change over time, meaning that radio channel configurations may be outdated and new reconfigurations can be done to improve network performance. To cope with the increasing demand for bandwidth, fiber to the home/premises/building (FTTX) technologies were massively deployed at the back-end. These technologies are characterized by the huge bandwidth capacity and the absence of active devices on the network plant, which is an advantage for power saving. On the other hand, at the front-end, wireless mesh networks (WMN) are expected to provide mobility and converge different wireless technologies to provide high-speed and huge bandwidth connectivity to the end user. In this dissertation, the frequency reassignment problem in the context of FiWi access networks is discussed and a state-of-art on the subject is proposed. Also, two methodologies for frequency reconfiguration planning are proposed along with their mathematical formalization, and are evaluated by simulation. In one of the strategies, NBR, the algorithm prioritizes channel assignment according to the relative position of nodes and their gateways, while in the other, RBR, nodes are processed as their routes toward the gateways are traversed. A discrete event simulation model to evaluate the performance of the proposed frequency reassignment algorithms was developed using OMNeT++ framework. Simulation results showing that RBR is the algorithm that better exploits channel reconfigurations are presented and discussed

Modeling and Optimization of Next-Generation Wireless Access Networks

The ultimate goal of the next generation access networks is to provide all network users, whether they are fixed or mobile, indoor or outdoor, with high data rate connectivity, while ensuring a high quality of service. In order to realize this ambitious goal, delay, jitter, error rate and packet loss should be minimized: a goal that can only be achieved through integrating different technologies, including passive optical networks, 4th generation wireless networks, and femtocells, among others. This thesis focuses on medium access control and physical layers of future networks. In this regard, the first part of this thesis discusses techniques to improve the end-to-end quality of service in hybrid optical-wireless networks. In these hybrid networks, users are connected to a wireless base station that relays their data to the core network through an optical connection. Hence, by integrating wireless and optical parts of these networks, a smart scheduler can predict the incoming traffic to the optical network. The prediction data generated herein is then used to propose a traffic-aware dynamic bandwidth assignment algorithm for reducing the end-to-end delay. The second part of this thesis addresses the challenging problem of interference management in a two-tier macrocell/femtocell network. A high quality, high speed connection for indoor users is ensured only if the network has a high signal to noise ratio. A requirement that can be fulfilled with using femtocells in cellular networks. However, since femtocells generate harmful interference to macrocell users in proximity of them, careful analysis and realistic models should be developed to manage the introduced interference. Thus, a realistic model for femtocell interference outside suburban houses is proposed and several performance measures, e.g., signal to interference and noise ratio and outage probability are derived mathematically for further analysis. The quality of service of cellular networks can be degraded by several factors. For example, in industrial environments, simultaneous fading and strong impulsive noise significantly deteriorate the error rate performance. In the third part of this thesis, a technique to improve the bit error rate of orthogonal frequency division multiplexing systems in industrial environments is presented. This system is the most widely used technology in next-generation networks, and is very susceptible to impulsive noise, especially in fading channels. Mathematical analysis proves that the proposed method can effectively mitigate the degradation caused by impulsive noise and significantly improve signal to interference and noise ratio and bit error rate, even in frequency-selective fading channels

Optical-WiMAX Hybrid Networks

The emergence of bandwidth-intensive Internet services, such ascircuit-quality voice transfer and interactive video gaming, createa high demand for a very qualified next-generation access network.In addition to high bandwidth, these future access networks shouldalso provide improved network availability, flexibility, mobility,reliability, failure protection, quality of service (QoS) supportand cost-effective access. The integration between optical networksand Worldwide Interoperability for Microwave Access (WiMAX) is apromising solution for future access networks. Accordingly, a fewdifferent architectures and MAC protocol components have recentlybeen proposed for the integration between the Ethernet PassiveOptical Network (EPON) and WiMAX. However, the proposedarchitectures contain several drawbacks. Moreover, the EPON-WiMAXhybrid does not yet contain a comprehensive Medium Access Control(MAC) protocol and a mechanism for Quality of Service (QoS) support.Finally, this work introduces the Resilient Packet Ring (RPR)standard, which aims to build high-performance metro edge and metrocore ring networks that interconnect multiple access networks. Theobjective of this thesis is to examine the integration of opticalstandards, such as RPR and EPON, with the WiMAX standard.Subsequently, this integration will be applied to the areas ofarchitecture and MAC Protocol as a promising solution for not onlyaccess networks but also for metro networks.The first part of the thesis examines the EPON-WiMAX integration asa solution for the access network. Specifically, the proposedsolution includes new EPON-WiMAX hybrid network architectures thatare suitable for both urban and rural environment requirements, andit also introduces a joint MAC protocol for these architectures. Theproposed architectures are reliable and provide extended networkcoverage; in particular, reliability is achieved by applying aprotection scheme to the most critical portion of the EPON part ofthe architecture. Additionally, the network coverage of thearchitecture is extended by inserting an intermediate networkbetween the front end and the backhaul network of the traditionalEPON-WiMAX architecture. Subsequently, we propose a comprehensivejoint MAC protocol for the proposed EPON-WiMAX architecture; thisprotocol provides a per-stream quality-of-service guarantee andimproves the network utilization. Also, the proposed joint MACprotocol includes an admission controller, a scheduler and abandwidth allocator.While the first part of the thesis strives to improve the hybridnetwork reliability through protection in the EPON part and extendthe network coverage through innovative methods, the second partattempts to maintain and enhance these objectives by adding areliable technology to the integrated network. Specifically, thissection examines the way in which the RPR network can be integratedwith the proposed EPON-WiMAX architecture to form an RPR-EPON-WiMAXhybrid network, which can be a solution for both access and metronetworks. The proposed architecture is reliable due to thedependability of the RPR standard and the protection mechanismemployed in the EPON network. Moreover, the architecture contains ahigh fault tolerance against node and connection failure. In thesecond part, the joint MAC protocol for the RPR-EPON-WiMAX hybridnetwork includes a multi-level dynamic bandwidth allocationalgorithm, a distributed admission control, a scheduler, and arouting algorithm. This MAC protocol aims to maximize the advantagesof the proposed architecture by distributing its functionalitiesover the parts of the architecture and jointly executing the partsof the MAC protocol

Switching Equipment Location/Allocation in hybrid PONs

Our research goal is to investigate the FTTX (Fiber-to-the Home/Premises/Curb) passive optical network (PON) for the deployment of BISAN (Broadband Internet Subscriber Access Network) to exploit the opportunities of optical fiber enabled technologies as well as of passive switching equipment. Indeed, the deployment of FTTX PON is the most OPEX-friendly scenario, because it allows for completely passive access networks through minimizing the number of active components in the network. Previously, most FTTX PON architectures are designed based on the principle of either time division multiplexing (TDM) technology or wavelength division multiplexing (WDM) technology. We focus on designing the best possible architectures of FTTX PON, specifically hybrid PONs, which embraces both TDM and WDM technology. A hybrid PON architecture is very efficient as it is not limited to any specific PON technology, rather it is flexible enough to deploy TDM/WDM technology depending on the type (i.e unicast/multicast) and amount of traffic demand of the end-users. The advantages of a hybrid PON are of two folds: (i) it can offer increased data rate to each user by employing WDM technology, (ii) it can provide flexible bandwidth utilization by employing TDM technology. In this thesis, we concentrate on determining the optimized covering of a geographical area by a set of cost-effective hybrid PONs. We also focus on the greenfield deployment of a single hybrid PON. It should be worthy to mention that while investigating the deployment of hybrid PONs, the research community around the world considers the specifications of either the physical layer or the optical layer. But an efficient planning for PON deployment should take into account the constraints of the physical and optical layers in order that both layers can work together harmoniously. We concentrate our research on the network dimensioning and the selection as well as the placement of the switching equipment in hybrid PONs with the intention of considering the constraints of both physical and optical layers. We determine the layout of an optimized PON architecture while provisioning wavelengths in a hybrid PON. We also propose to select the switching equipment depending on the type (unicast/multicast) of traffic demand. Finally, we determine the best set of hybrid PONs along with their cascading architecture, type and location of their switching equipment while satisfying the network design constraints such as the number of output ports of the switching equipment and maximum allowed signal power loss experienced at each end user’s premises. In this thesis, we propose two novel schemes for the greenfield deployment of a single hybrid PON. The first scheme consists of two phases in which a heuristic algorithm and a novel column generation (CG) based integer linear programming (ILP) optimization model are proposed in the 1st and 2nd phase respectively. In the second scheme, a novel integrated CG based ILP cross layer optimization model is proposed for the designing of a single hybrid PON. We also propose two novel schemes to deal with the greenfield deployment of multiple hybrid PONs in a given geographical area. These two schemes determine the best set of cost-effective hybrid PONs in order to serve all the end users in a given neighborhood. The first scheme executes in four phases in which two heuristic algorithms, a CG based ILP model and an ILP optimization model are proposed in the 1st, 2nd, 3rd and 4th phase respectively. In the second scheme, an ILP model as well as a CG based ILP model, another ILP model as well as another CG based ILP model, a CG based ILP model and an ILP optimization model are proposed during four consecutive phases. Our proposed scheme can optimize the design of a set of hybrid PONs covering a given geographic area as well as the selection of the best cascading architecture 1/2/mixedstage) for each selected PON. It minimizes the overall network deployment cost based on the location of the OLT and the ONUs while granting all traffic demands. The scheme emphasizes on the optimum placement of equipment in a hybrid PON infrastructure due to the critical dependency between the network performances and a proper deployment of its equipment, which, in turn depends on the locations of the users. It is a quite powerful scheme as it can handle data instances with up to several thousands ONUs. On the basis of the computational results, the proposed scheme leads to an efficient automated tool for network design, planning, and performance evaluation which can be beneficial for the network designers