Application-Oriented Flow Control: Fundamentals, Algorithms and Fairness

This paper is concerned with flow control and resource allocation problems in computer networks in which real-time applications may have hard quality of service (QoS) requirements. Recent optimal flow control approaches are unable to deal with these problems since QoS utility functions generally do not satisfy the strict concavity condition in real-time applications. For elastic traffic, we show that bandwidth allocations using the existing optimal flow control strategy can be quite unfair. If we consider different QoS requirements among network users, it may be undesirable to allocate bandwidth simply according to the traditional max-min fairness or proportional fairness. Instead, a network should have the ability to allocate bandwidth resources to various users, addressing their real utility requirements. For these reasons, this paper proposes a new distributed flow control algorithm for multiservice networks, where the application's utility is only assumed to be continuously increasing over the available bandwidth. In this, we show that the algorithm converges, and that at convergence, the utility achieved by each application is well balanced in a proportionally (or max-min) fair manner

Consensus problems in networks of agents with switching topology and time-delays

In this paper, we discuss consensus problems for networks of dynamic agents with fixed and switching topologies. We analyze three cases: 1) directed networks with fixed topology; 2) directed networks with switching topology; and 3) undirected networks with communication time-delays and fixed topology. We introduce two consensus protocols for networks with and without time-delays and provide a convergence analysis in all three cases. We establish a direct connection between the algebraic connectivity (or Fiedler eigenvalue) of the network and the performance (or negotiation speed) of a linear consensus protocol. This required the generalization of the notion of algebraic connectivity of undirected graphs to digraphs. It turns out that balanced digraphs play a key role in addressing average-consensus problems. We introduce disagreement functions for convergence analysis of consensus protocols. A disagreement function is a Lyapunov function for the disagreement network dynamics. We proposed a simple disagreement function that is a common Lyapunov function for the disagreement dynamics of a directed network with switching topology. A distinctive feature of this work is to address consensus problems for networks with directed information flow. We provide analytical tools that rely on algebraic graph theory, matrix theory, and control theory. Simulations are provided that demonstrate the effectiveness of our theoretical results

Resource allocation in networks from a connection-level perspective (Asignación de recursos en redes desde la perspectiva de las conexiones)

En esta tesis, se analizan varios problemas de asignación recursos que surgen en el estudio de los sistemas de telecomunicaciones. En particular, nos centramos en las redes de datos, de los cuales el ejemplo más importante es la Internet global. En este tipo de redes, el recurso escaso que debe ser asignado es la cantidad de ancho de banda de cada conexión curso. Esta asignación realiza en tiempo real por los protocolos subyacentes, que técniamente se encuentran divididos en varios niveles o capas. Desde este punto de vista, la red puede ser pensada como un sistema de control a gran escala, donde cada entidad debe seguir un conjunto dado de leyes de control, a fin de encontrar una asignación adecuada de recursos. Desde el influyente trabajo de Kelly et. al., este problema se ha expresado en términos económicos, dando lugar a la teoría conocida como Network Utility Maximization (maximización de utilidad en redes). Este marco ha demostrado ser una herramienta valiosa para analizar los mecanismos existentes y diseño de protocolos nuevos que mejoran el comportamiento de la red. Proporciona además un vínculo crucial entre el tradicional análisis por capas de los protocolos de red y las técnicas de optimización convexa, dando lugar a lo que se denomina análisis multi-capa de las redes. En este trabajo nos centramos en el análisis de la red desde una perspectiva a nivel de conexiones. En particular, se estudia el desempeño de eficiencia y justicia en la escala de conexiones de varios modelos de asignación de recursos en la red. Este estudio se realiza en varios escenarios: tanto single-path como multi-path (redes con múltiples caminos) así como escenarios cableados e inalámbricos. Se analizan en detalle dos problemas importantes: por un lado, la asignación de los recursos realizada por los protocolos de control de congestión cuando se permiten varias conexiones por usuario. Se identifican algunos problemas del paradigma actual, y se propone un nuevo concepto de \emph{equidad centrada en el usuario}, desarrollando a su vez algoritmos descentralizados que se pueden aplicar en los extremos de la red, y que conducen al sistema a un global adecuado. El segundo problema importante analizado aquí es la asignación de los recursos realizada por los algoritmos de control de congestión cuando trabajan sobre una capa física que permite múltiples velocidades de transmisión como es el caso en las redes inalámbricas. Se demuestra que los algoritmos usuales conducen a ineficiencias importantes desde el punto de vista de las conexiones, y se proponen mecanismos para superar estas ineficiencias y mejorar la asignación de los recursos prestados por dichas redes. A lo largo de este trabajo, se aplican varias herramientas matemáticas, tales como la optimización convexa, la teoría de control y los procesos estocásticos. Por medio de estas herramientas, se construye un modelo del sistema, y se desarrollan leyes de control y algoritmos para lograr el objetivo de desempeño deseado. Como paso final, estos algoritmos fueron probados a través de simulaciones a nivel de paquetes de las redes involucradas, proporcionando la validación de la teoría y la evidencia de que pueden aplicarse en la práctica

QoS constrained cellular ad hoc augmented networks

In this dissertation, based on different design criteria, three novel quality of service (QoS) constrained cellular ad hoc augmented network (CAHAN) architectures are proposed for next generation wireless networks. The CAHAN architectures have a hybrid architecture, in which each MT of CDMA cellular networks has ad hoc communication capability. The CAHAN architectures are an evolutionary approach to conventional cellular networks. The proposed architectures have good system scalability and high system reliability. The first proposed architecture is the QoS constrained minimum-power cellular ad hoc augmented network architecture (QCMP CAHAN). The QCMP CAHAN can find the optimal minimum-power routes under the QoS constraints (bandwidth, packet-delay, or packet-error-rate constraint). The total energy consumed by the MTs is lower in the case of QCMP CAHAN than in the case of pure cellular networks. As the ad hoc communication range of each MT increases, the total transmitted power in QCMP CAHAN decreases. However, due to the increased number of hops involved in information delivery between the source and the destination, the end-to-end delay increases. The maximum end-to-end delay will be limited to a specified tolerable value for different services. An MT in QCMP CAHAN will not relay any messages when its ad hoc communication range is zero, and if this is the case for all MTs, then QCMP CAHAN reduces to the traditional cellular network. A QoS constrained network lifetime extension cellular ad hoc augmented network architecture (QCLE CAHAN) is proposed to achieve the maximum network lifetime under the QoS constraints. The network lifetime is higher in the case of QCLE CAHAN than in the case of pure cellular networks or QCMP CAHAN. In QCLE CAHAN, a novel QoS-constrained network lifetime extension routing algorithm will dynamically select suitable ad-hoc-switch-to-cellular points (ASCPs) according to the MT remaining battery energy such that the selection will balance all the MT battery energy and maximizes the network lifetime. As the number of ASCPs in an ad hoc subnet decreases, the network lifetime will be extended. Maximum network lifetime can be increased until the end-to-end QoS in QCLE CAHAN reaches its maximum tolerable value. Geocasting is the mechanism to multicast messages to the MTs whose locations lie within a given geographic area (target area). Geolocation-aware CAHAN (GA CAHAN) architecture is proposed to improve total transmitted power expended for geocast services in cellular networks. By using GA CAHAN for geocasting, saving in total transmitted energy can be achieved as compared to the case of pure cellular networks. When the size of geocast target area is large, GA CAHAN can save larger transmitted energy

Load Balancing Dynamic Source Routing Protocol Based on Multi-Path Routing

A HWMP improved routing protocol (HWMMRP) is proposed in this paper. The protocol adopts the integrated link state routing criterion algorithm LCCM providing small overhead, with factors such as bandwidth, queue length and noise interference fully considered. In order to solve the problem of the tree routing mechanism being easily congested at the root node, a multi-path multi-gateway shunting mechanism is applied. A multipath routing mechanism is also incorporated in the reactive routing mode. Both the new criteria and the protocol are simulated in the NS-2 environment, and are compared with comparable protocols. The experimental results show that our protocol can effectively avoid node congestion, and provides a better dynamic load balancing capability as well as a better performance than the standard HWMP and AODV protocols

Quality of service-aware routing and admission control for mobile ad hoc networks

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Quality of service-aware routing and admission control for mobile ad hoc networks

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Scalable reliable on-demand media streaming protocols

This thesis considers the problem of delivering streaming media, on-demand, to potentially large numbers of concurrent clients. The problem has motivated the development in prior work of scalable protocols based on multicast or broadcast. However, previous protocols do not allow clients to efficiently: 1) recover from packet loss; 2) share bandwidth fairly with competing flows; or 3) maximize the playback quality at the client for any given client reception rate characteristics. In this work, new protocols, namely Reliable Periodic Broadcast (RPB) and Reliable Bandwidth Skimming (RBS), are developed that efficiently recover from packet loss and achieve close to the best possible server bandwidth scalability for a given set of client characteristics. To share bandwidth fairly with competing traffic such as TCP, these protocols can employ the Vegas Multicast Rate Control (VMRC) protocol proposed in this work. The VMRC protocol exhibits TCP Vegas-like behavior. In comparison to prior rate control protocols, VMRC provides less oscillatory reception rates to clients, and operates without inducing packet loss when the bottleneck link is lightly loaded. The VMRC protocol incorporates a new technique for dynamically adjusting the TCP Vegas threshold parameters based on measured characteristics of the network. This technique implements fair sharing of network resources with other types of competing flows, including widely deployed versions of TCP such as TCP Reno. This fair sharing is not possible with the previously defined static Vegas threshold parameters. The RPB protocol is extended to efficiently support quality adaptation. The Optimized Heterogeneous Periodic Broadcast (HPB) is designed to support a range of client reception rates and efficiently support static quality adaptation by allowing clients to work-ahead before beginning playback to receive a media file of the desired quality. A dynamic quality adaptation technique is developed and evaluated which allows clients to achieve more uniform playback quality given time-varying client reception rates

LINK ADAPTATION IN WIRELESS NETWORKS: A CROSS-LAYER APPROACH

Conventional Link Adaptation Techniques in wireless networks aim to overcome harsh link conditions caused by physical environmental properties, by adaptively regulating modulation, coding and other signal and protocol specific parameters. These techniques are essential for the overall performance of the networks, especially for environments where the ambient noise level is high or the noise level changes rapidly. Link adaptation techniques answer the questions of What to change? and When to change? in order to improve the present layer performance. Once these decisions are made, other layers are expected to function perfectly with the new communication channel conditions. In our work, we have shown that this assumption does not always hold; and provide two mechanisms that lessen the negative outcomes caused by these decisions. Our first solution, MORAL, is a MAC layer link adaptation technique which utilizes the physical transmission information in order to create differentiation between wireless users with different communication capabilities. MORAL passively collects information from its neighbors and re-aligns the MAC layer parameters according to the observed conditions. MORAL improves the fairness and total throughput of the system through distributing the mutually shared network assets to the wireless users in a fairer manner, according to their capabilities. Our second solution, Data Rate and Fragmentation Aware Ad-hoc Routing protocol, is a network layer link adaptation technique which utilizes the physical transmission information in order to differentiate the wireless links according to their communication capabilities. The proposed mechanism takes the physical transmission parameters into account during the path creation process and produces energy-efficient network paths. The research demonstrated in this dissertation contributes to our understanding of link adaptation techniques and broadens the scope of such techniques beyond simple, one-step physical parameter adjustments. We have designed and implemented two cross-layer mechanisms that utilize the physical layer information to better adapt to the varying channel conditions caused by physical link adaptation mechanisms. These mechanisms has shown that even though the Link Adaptation concept starts at the physical layer, its effects are by no means restricted to this layer; and the wireless networks can benefit considerably by expanding the scope of this concept throughout the entire network stack