Michel Diaz

W-NINE: a two-stage emulation platform for mobile and wireless systems

AbstractssMore and more applications and protocols are now running on wireless networks. Testing the implementation of such applications and protocols is a real challenge as the position of the mobile terminals and environmental effects strongly affect the overall performance. Network emulation is often perceived as a good trade-off between experiments on operational wireless networks and discrete-event simulations on Opnet or ns-2. However, ensuring repeatability and realism in network emulation while taking into account mobility in a wireless environment is very difficult. This paper proposes a network emulation platform, called W-NINE, based on off-line computations preceding online pattern-based traffic shaping. The underlying concepts of repeatability, dynamicity, accuracy, and realism are defined in the emulation context. Two different simple case studies illustrate the validity of our approach with respect to these concepts.

Cross-layer based congestion control for WLANs

Congestion control is a fundamental mechanism for the stability of the Internet and is a central mechanism for TCP. However, this congestion control mechanism focuses mainly on the core network state and is blind to the characteristics of wireless and mobile access networks. Moreover, TCP window based congestion control ignores totally application layer QoS needs and entails throughput variations which are not compliant with application layer QoS constraints such as bandwidth, delay and jitter. The TCP-Friendly Rate Control protocol (TFRC) was originally designed in the context of wired networks. This protocol is one of the most convincing attempt to provide a congestion control mechanism adapted to multimedia flows, although limited in its capacity to fully address these issues. After an identification and evaluation of the subtle counterproductive interactions between the WLANs MAC layer and the transport layer, this paper shows a new approach towards congestion control for WLANs. This paper also introduces a specialization of TFRC (MTFRC: Mobile TFRC), which is adapted to wireless access networks. This TFRC specialization requires only slight changes to the standard TFRC protocol. Simulation results show substantial improvements for applications over TFRC in scenarios where the bottleneck situates on the MAC layer of the mobile nodes.

New generation of transport protocols for autonomous systems

Requirements and constraints of the communication services required by autonomous systems raise new challenges to the traditional transport protocol layer. Indeed, classical transport protocols (i.e. TCP and UDP) were well dimensioned for the standard distributed applications operating over best-effort network services. Today, more sophisticated transport protocols are required in order to self-configure and self-adapt to varying network resources (e.g. wireless network systems) guided by the requirements and preferences of both the autonomous systems and their applications. This new generation of transport protocols should follow a component-based and service-oriented approach intended to smoothly incorporate current and future protocol components and their specialization, based on the semantic associated to their functions and capabilities. Moreover, these transport protocols should be designed following an autonomic computing approach in order to incorporate autonomic managers in charge of continuous network monitoring, anomalies detection, selection and enforcement of correction strategies to adapt transport components. Furthermore, competing autonomic managers operating over shared and resource-limited networks should be coordinated by higher-level managers in order to better share the available resources. The autonomic management of these resources should be done based on the systems and applications requirements and priorities in order to offer a collaborative orchestrated transport service. This paper presents a framework for defining autonomic transport composite services aimed at providing the basis for designing and developing this new generation transport layer. This framework is intended to dynamically compose reusable transport components based on the semantic associated to each component and guided by the final service expected from the composite architecture. An ontology-driven and service-oriented architecture approach has been followed in order to integrate autonomous systems requirements as well as the characterization of autonomic transport components in order to guide the composition and the service selection processes.

A Novel Bandwidth Broker Architecture Based on Topology Aggregation in Delay|Bandwidth Sensitive Networks

Either in flow-based or class-based QoS architectures, controlling the admission of traffic entering the network becomes a crucial task in the new telecom services. The Bandwidth Broker BB architecture is one of the efficient admission control solutions. In this paper, we present a novel bandwidth broker architecture for scalable support of guaranteed services based on the concept of topology aggregation. Indeed, the bandwidth broker does not manage all the detailed information, about topology and reservation, stored in the admission control database. Instead, it uses an aggregated representation in order to decide if a new service request can be accepted or rejected. We demonstrate that the reduction of the amount of information managed by the bandwidth broker enhance the performance of the admission control function thereby increasing the overall call processing capability.

A cross-layer architecture to improve mobile host rate performance and to solve unfairness problem in WLANs

The evolution of the Internet has been mainly promoted in recent years by the emergence and proliferation of wireless access networks towards a global ambient and pervasive network accessed from mobile devices. These new access networks have introduced new MAC layers independently of the legacy “wire-oriented” protocols that are still at the heart of the protocol stacks of the end systems. This principle of isolation and independence between layers advocated by the OSI model has its drawbacks of maladjustment between new access methods and higher-level protocols built on the assumption of a wired Internet. In this paper, we introduce and deliver solutions for several pathological communication behaviors resulting from the maladjustment between WLAN MAC and higher layer standard protocols such as TCP/IP and UDP/IP. Specially, based on an efficient analytical model for WLANs bandwidth estimation, we address in this paper the two following issues: (1)xa0Performance degradation due to the lack of flow control between the MAC and upper layer resulting in potential MAC buffer overflow; (2)xa0Unfair bandwidth share issues between various type of flows. We show how these syndromes can be efficiently solved from neutral “cross layer” interactions which entail no changes in the considered protocols and standards.

Mobile TFRC: a congestion control for WLANs

Based on an identification and evaluation of the subtle counterproductive interactions between the WLANs MAC layer and the transport layer, this paper shows a new approach towards congestion control for WLANs. We introduce a specialization of TFRC (MTFRC: mobile TFRC), which is adapted to wireless access networks. This TFRC specialization requires only slight changes to the standard TFRC protocol. Simulation results show substantial improvements for applications over TFRC in scenarios where the bottleneck situates on the MAC layer of the mobile nodes.

Inter-domain QoS signaling under mobility

This paper deals with the problem of QoS signaling across multiples domains in a context of topological changes due to mobility. Data path changes caused by mobility can degrade severely the service continuity to mobile terminals considering the end-to-end QoS inter-domain path reestablishment. We propose an efficient NSIS-based scheme to allow end-to-end QoS path maintenance under mobility. The domains are controlled by central resource managers acting as bandwidth brokers. The scheme addresses two open issues in the area: (a) the integration of NSIS with Hierarchical Mobile IP including anchor points collaboration to QoS signaling, and (b) the use of NSIS in an hybrid on and o/f-path context, exploring the common off-path points to improve signaling. The signaling procedure aims to reduce the impact of mobility in the time to setup new QoS paths and the time to tear down unused resources.

Cross-layer based erasure code to reduce the 802.11 performance anomaly: when FEC meets ARF

Wireless networks have been widely accepted and deployed in our world nowadays. Consumers are now accustomed to wireless connectivity in their daily life due to the pervasiveness of the 802.11b/g and wireless LAN standards. Specially, the emergence of the next evolution of Wi-Fi technology known as 802.11n is pushing a new revolution on personal wireless communication. However, in the context of WLAN, although multiple novel wireless access technologies have been proposed and developed to offer high bandwidth and guarantee quality of transmission, some deficiencies still remain due to the original design of WLAN-MAC layer. In particular, the performance anomaly of 802.11 is a serious issue which induces a potentially dramatic reduction of the global bandwidth when one or several mobile nodes downgrade their transmission rates following the signal degradation. In this paper, we study how the use of adaptive erasure code as a replacement of the Auto Rate Feedback mechanism can help to mitigate this performance anomaly issue. Preliminary study shows a global increase of the goodput delivered to mobile hosts attached to an access point.

Optimization of WiMax modulation scheme with a cross layer erasure code

WIMAX (Worldwide Interoperability for Microwave Access) is a promising new networking technology that potentially offers high speed and wide area wireless access services that complement consistently the 3G and WiFi access networks capabilities. The standard proposes an adaptive modulation scheme which allows WiMax nodes to communicate from various modulation coding schemes according to the link quality. However, the standard does not define a detailed link adaptation algorithm and currently, the most largely used modulation adaptation technique is based on a channel quality lookup table. We argue that this method is not able to make the best adaptation decisions and delivers a sub-optimal goodput in numerous communication contexts. In this paper, we propose a novel cross layer based modulation adaptation mechanism which incorporates the use of adaptive erasure code with the physical layer information to significantly improve the goodput and transmission efficiency. Simulation results show that our proposal adapts more efficiently to real environments and achieves a significant gain on the goodput delivered to mobile nodes.

Path Prediction for Resource Reservation Between Mobile Nodes

End-to-end QoS can be achieved through resource reservations along the communication path between end points. Per flow or per aggregate signaling can be used to set up reservation states in routers or domains on the path. In a mobile environment this reservation process can be very cumbersome, given that (i) the time to set up the resources in the new path is not neglectable and (ii) the resources may not be available during the handover process. Advance reservations is a possible solution for this problem. This paper1 describes a procedure to compute a set of considered paths in a resource reservation, during a communication session when both hosts are mobile. We depart from a semi Markov user mobility model extracted from regular user movements. We combine both user models to generate a time evolution equation that allows computing the probability to be in a future path from a current path in a given time. We use this function to build an optimisation problem in a binary integer programming formulation. A target probability of lacking resources is used as a constraint to select a subset of paths based on a cost metric.