QoSatAr: a cross-layer architecture for E2E QoS provisioning over DVB-S2 broadband satellite systems

This article presents QoSatAr, a cross-layer architecture developed to provide end-to-end quality of service (QoS) guarantees for Internet protocol (IP) traffic over the Digital Video Broadcasting-Second generation (DVB-S2) satellite systems. The architecture design is based on a cross-layer optimization between the physical layer and the network layer to provide QoS provisioning based on the bandwidth availability present in the DVB-S2 satellite channel. Our design is developed at the satellite-independent layers, being in compliance with the ETSI-BSM-QoS standards. The architecture is set up inside the gateway, it includes a Re-Queuing Mechanism (RQM) to enhance the goodput of the EF and AF traffic classes and an adaptive IP scheduler to guarantee the high-priority traffic classes taking into account the channel conditions affected by rain events. One of the most important aspect of the architecture design is that QoSatAr is able to guarantee the QoS requirements for specific traffic flows considering a single parameter: the bandwidth availability which is set at the physical layer (considering adaptive code and modulation adaptation) and sent to the network layer by means of a cross-layer optimization. The architecture has been evaluated using the NS-2 simulator. In this article, we present evaluation metrics, extensive simulations results and conclusions about the performance of the proposed QoSatAr when it is evaluated over a DVB-S2 satellite scenario. The key results show that the implementation of this architecture enables to keep control of the satellite system load while guaranteeing the QoS levels for the high-priority traffic classes even when bandwidth variations due to rain events are experienced. Moreover, using the RQM mechanism the user’s quality of experience is improved while keeping lower delay and jitter values for the high-priority traffic classes. In particular, the AF goodput is enhanced around 33% over the drop tail scheme (on average)

Transform-domain analysis of packet delay in network nodes with QoS-aware scheduling

In order to differentiate the perceived QoS between traffic classes in heterogeneous packet networks, equipment discriminates incoming packets based on their class, particularly in the way queued packets are scheduled for further transmission. We review a common stochastic modelling framework in which scheduling mechanisms can be evaluated, especially with regard to the resulting per-class delay distribution. For this, a discrete-time single-server queue is considered with two classes of packet arrivals, either delay-sensitive (1) or delay-tolerant (2). The steady-state analysis relies on the use of well-chosen supplementary variables and is mainly done in the transform domain. Secondly, we propose and analyse a new type of scheduling mechanism that allows precise control over the amount of delay differentiation between the classes. The idea is to introduce N reserved places in the queue, intended for future arrivals of class 1

Improving Dependability of Real-Time Communication with Preplanned Backup Routes and Spare Resource Pool

Abstract. Timely recovery from network component failures is essential to the applications that require guaranteed-performance communication services. To achieve dependable communication, there have been several proposals that can be classified into two categories: reactive and proac-tive. The reactive approach tries to reroute traffic upon detection of a network link/node failure. This approach may suffer from contention and resource shortage when multiple connections need to be rerouted at the same time. The proactive approach, on the other hand, prepares a backup channel in advance that will be activated upon failure of the corresponding primary channel due to a broken link or node. The proactive approach, although it offers higher dependability, incurs higher routing overhead than the reactive approach. We propose a hybrid approach that reduces signaling overhead by de-coupling backup routing from resource provisioning. We also propose an efficient backup routing algorithm for the hybrid approach. Our in-depth simulation results show that the proposed approach can achieve the abil-ity of failure recovery comparable to the proactive scheme without the need for broadcasting the routing information.

Enabling wireless LAN troubleshooting

Particular WLAN pathologies experienced in realistic scenarios are hard to detect, due to the complex nature of the wireless medium. Prior work has employed sophisticated equipment, driver modifications, or even application-layer techniques, towards diagnosing such pathologies. The key novelty of our approach lies in the identification of metrics able to characterize the root causes of individual pathologies, while also being directly extractable from MAC-layer statistics available in today’s wireless equipment. Through the development of the proposed framework as application-layer software on top of commercial hardware and its experimental evaluation, we validate the efficiency and applicability of our approach. © Springer International Publishing Switzerland 2015