64,197 research outputs found
Utilization-based delay guarantee techniques and their applications
Many real-time systems demand effective and efficient delay-guaranteed services
to meet timing requirements of their applications. We note that a system provides a
delay-guaranteed service if the system can ensure that each task will meet its predefined
end-to-end deadline. Admission control plays a critical role in providing delayguaranteed
services. The major function of admission control is to determine
admissibility of a new task. A new task will be admitted into the system if the deadline
of all existing tasks and the new task can be met. Admission control has to be efficient
and efficient, meaning that a decision should be made quickly while admitting the
maximum number of tasks.
In this dissertation, we study a utilization-based admission control mechanism.
Utilization-based admission control makes an admission decision based on a simple
resource utilization test: A task will be admitted if the resource utilization is lower than a
pre-derived safe resource utilization bound. The challenge of obtaining a safe resource
utilization bound is how to perform delay analysis offline, which is the main focus of this dissertation. For this, we develop utilization-based delay guarantee techniques to
render utilization-based admission control both efficient and effective, which is further
confirmed with our data.
We develop techniques for several systems that are of practical importance. We
first consider wired networks with the Differentiated Services model, which is wellknown
as its supporting scalable services in computer networks. We consider both cases
of providing deterministic and statistical delay-guaranteed services in wired networks
with the Differentiated Services model. We will then extend our work to wireless
networks, which have become popular for both civilian and mission critical applications.
The variable service capacity of a wireless link presents more of a challenge in providing
delay-guaranteed services in wireless networks. Finally, we study ways to provide delayguaranteed
services in component-based systems, which now serve as an important
platform for developing a new generation of computer software. We show that with our
utilization-based delay guarantee technique, component-based systems can provide
efficient and effective delay-guaranteed services while maintaining such advantages as
the reusability of components
Performance analysis of a Master/Slave switched Ethernet for military embedded applications
Current military communication network is a generation
old and is no longer effective in meeting the emerging
requirements imposed by the next generation military embedded applications. A new communication network based upon Full Duplex Switched Ethernet is proposed in this paper to overcome these limitations. To allow existing military subsystems to be easily supported by a Switched Ethernet network, our proposal consists in keeping their current centralized communication scheme by using an optimized master/slave transmission control on Switched Ethernet thanks to the Flexible Time Triggered (FTT) paradigm. Our main objective is to assess the performance
of such a proposal and estimate the quality of service we
can expect in terms of latency. Using the Network Calculus formalism, schedulability analysis are determined. These analysis are illustrated in the case of a realistic military embedded application extracted from a real military aircraft network, to highlight the proposal's ability to support the required time constrained communications
A Fair and Efficient Packet Scheduling Scheme for IEEE 802.16 Broadband Wireless Access Systems
This paper proposes a fair and efficient QoS scheduling scheme for IEEE
802.16 BWA systems that satisfies both throughput and delay guarantee to
various real and non-real time applications. The proposed QoS scheduling scheme
is compared with an existing QoS scheduling scheme proposed in literature in
recent past. Simulation results show that the proposed scheduling scheme can
provide a tight QoS guarantee in terms of delay, delay violation rate and
throughput for all types of traffic as defined in the WiMAX standard, thereby
maintaining the fairness and helps to eliminate starvation of lower priority
class services. Bandwidth utilization of the system and fairness index of the
resources are also encountered to validate the QoS provided by our proposed
scheduling scheme
A Simple and Robust Dissemination Protocol for VANETs
Several promising applications for Vehicular Ad-hoc Networks (VANETs) exist. For most of these applications, the communication among vehicles is envisioned to be based on the broadcasting of messages. This is due to the inherent highly mobile environment and importance of these messages to vehicles nearby. To deal with broadcast communication, dissemination protocols must be defined in such a way as to (i) prevent the so-called broadcast storm problem in dense networks and (ii) deal with disconnected networks in sparse topologies. In this paper, we present a Simple and Robust Dissemination (SRD) protocol that deals with these requirements in both sparse and dense networks. Its novelty lies in its simplicity and robustness. Simplicity is achieved by considering only two states (cluster tail and non- tail) for a vehicle. Robustness is achieved by assigning message delivery responsibility to multiple vehicles in sparse networks. Our simulation results show that SRD achieves high delivery ratio and low end-to-end delay under diverse traffic conditions
- …