200,459 research outputs found
A Parallel Virtual Queue Structure for Active Queue Management
The performance of the Adaptive RED scheme is susceptible to bursty web traffic. In this paper a parallel virtual queue structure is proposed for active queue management at the bottleneck router. Real time connections such as web and UDP, and non-real time connections such as FTP are served in two different virtual queues with drop-tail and Adaptive RED policies, respectively. Both queues share the same physical buffer memory. Simulation shows that file delivery for the web traffic is greatly improved due to shorter packet delay and lower packet loss rate, and that the queue length variation for the FTP traffic is small. To improve the goodput of the non-real time connections, a modified Adaptive RED scheme with dynamic queue length thresholds is also proposed. This scheme is able to keep the packet dropping probability within a desired small region. Stability of the queue length under this scheme is studied through analysis and numerical computation
Uplink Channel Allocation Scheme and QoS Management Mechanism for Cognitive Cellular-Femtocell Networks
Cognitive radio and femtocell are promising technologies which can satisfy the requirements of future mobile communications in terms of dynamic spectrum sharing and high user density areas. Providing quality-of-service (QoS) guaranteed realtime services is challenging issue of future cognitive cellular-femtocell mobile networks. In this paper, we introduce a user’s QoS management mechanism used to protect SINR of macro users from QoS violation caused by femtocell users. We design a novel uplink channel allocation scheme (denoted as “flexible scheme”) for real-time connections. The scheme uses the information of interference level and channel occupancy collected at cognitive femtocell access points and their covering macro base station (MBS) and apply relevant selection criteria to select an appropriate channel which causes the minimums interference to macro users of the covering MBS. Performance results prove that comparing with femtocell-access-point (FAP)-based and MBS-based uplink channel allocation schemes, the novel “flexible scheme” can provide lower unsuccessful probability of new connection requests
Cross-layer design of multi-hop wireless networks
MULTI -hop wireless networks are usually defined as a collection of nodes
equipped with radio transmitters, which not only have the capability to
communicate each other in a multi-hop fashion, but also to route each others’ data
packets. The distributed nature of such networks makes them suitable for a variety of
applications where there are no assumed reliable central entities, or controllers, and
may significantly improve the scalability issues of conventional single-hop wireless
networks.
This Ph.D. dissertation mainly investigates two aspects of the research issues
related to the efficient multi-hop wireless networks design, namely: (a) network
protocols and (b) network management, both in cross-layer design paradigms to
ensure the notion of service quality, such as quality of service (QoS) in wireless mesh
networks (WMNs) for backhaul applications and quality of information (QoI) in
wireless sensor networks (WSNs) for sensing tasks. Throughout the presentation of
this Ph.D. dissertation, different network settings are used as illustrative examples,
however the proposed algorithms, methodologies, protocols, and models are not
restricted in the considered networks, but rather have wide applicability.
First, this dissertation proposes a cross-layer design framework integrating
a distributed proportional-fair scheduler and a QoS routing algorithm, while using
WMNs as an illustrative example. The proposed approach has significant performance
gain compared with other network protocols. Second, this dissertation proposes
a generic admission control methodology for any packet network, wired and
wireless, by modeling the network as a black box, and using a generic mathematical
0. Abstract 3
function and Taylor expansion to capture the admission impact. Third, this dissertation
further enhances the previous designs by proposing a negotiation process,
to bridge the applications’ service quality demands and the resource management,
while using WSNs as an illustrative example. This approach allows the negotiation
among different service classes and WSN resource allocations to reach the optimal
operational status. Finally, the guarantees of the service quality are extended to
the environment of multiple, disconnected, mobile subnetworks, where the question
of how to maintain communications using dynamically controlled, unmanned data
ferries is investigated
Energy-efficient wireless communication
In this chapter we present an energy-efficient highly adaptive network interface architecture and a novel data link layer protocol for wireless networks that provides Quality of Service (QoS) support for diverse traffic types. Due to the dynamic nature of wireless networks, adaptations in bandwidth scheduling and error control are necessary to achieve energy efficiency and an acceptable quality of service. In our approach we apply adaptability through all layers of the protocol stack, and provide feedback to the applications. In this way the applications can adapt the data streams, and the network protocols can adapt the communication parameters
Organic Design of Massively Distributed Systems: A Complex Networks Perspective
The vision of Organic Computing addresses challenges that arise in the design
of future information systems that are comprised of numerous, heterogeneous,
resource-constrained and error-prone components or devices. Here, the notion
organic particularly highlights the idea that, in order to be manageable, such
systems should exhibit self-organization, self-adaptation and self-healing
characteristics similar to those of biological systems. In recent years, the
principles underlying many of the interesting characteristics of natural
systems have been investigated from the perspective of complex systems science,
particularly using the conceptual framework of statistical physics and
statistical mechanics. In this article, we review some of the interesting
relations between statistical physics and networked systems and discuss
applications in the engineering of organic networked computing systems with
predictable, quantifiable and controllable self-* properties.Comment: 17 pages, 14 figures, preprint of submission to Informatik-Spektrum
published by Springe
An Authentication Protocol for Future Sensor Networks
Authentication is one of the essential security services in Wireless Sensor
Networks (WSNs) for ensuring secure data sessions. Sensor node authentication
ensures the confidentiality and validity of data collected by the sensor node,
whereas user authentication guarantees that only legitimate users can access
the sensor data. In a mobile WSN, sensor and user nodes move across the network
and exchange data with multiple nodes, thus experiencing the authentication
process multiple times. The integration of WSNs with Internet of Things (IoT)
brings forth a new kind of WSN architecture along with stricter security
requirements; for instance, a sensor node or a user node may need to establish
multiple concurrent secure data sessions. With concurrent data sessions, the
frequency of the re-authentication process increases in proportion to the
number of concurrent connections, which makes the security issue even more
challenging. The currently available authentication protocols were designed for
the autonomous WSN and do not account for the above requirements. In this
paper, we present a novel, lightweight and efficient key exchange and
authentication protocol suite called the Secure Mobile Sensor Network (SMSN)
Authentication Protocol. In the SMSN a mobile node goes through an initial
authentication procedure and receives a re-authentication ticket from the base
station. Later a mobile node can use this re-authentication ticket when
establishing multiple data exchange sessions and/or when moving across the
network. This scheme reduces the communication and computational complexity of
the authentication process. We proved the strength of our protocol with
rigorous security analysis and simulated the SMSN and previously proposed
schemes in an automated protocol verifier tool. Finally, we compared the
computational complexity and communication cost against well-known
authentication protocols.Comment: This article is accepted for the publication in "Sensors" journal. 29
pages, 15 figure
- …