Many network systems with distributed structure today such as streaming media systems and resource-sharing systems can be modeled as the distributed network service system with multiple service nodes. admission contro...
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ISBN:
(纸本)9781479931064
Many network systems with distributed structure today such as streaming media systems and resource-sharing systems can be modeled as the distributed network service system with multiple service nodes. admissioncontrol technology is an essential way to enhance such systems. Model-based optimization approach as Markov decision process (MDP) is a good way to be applied to analyze and compute the optimal admissioncontrol policy that maximizes performance of system. However, due to the "curse of dimensionality", computing such optimal admissioncontrol policy for practical distributed systems is a rather difficult task. Therefore, we describe the admissioncontrol process of the distributed network service system as a switching partially observable Markov decision process (SPOMDP) with two-level structure. The upper level decides whether to switch the operation mode of system, and the lower level decides to admit or block new service requests. According to the partially observable Markov decision process (POMDP) model, a distributed admission control algorithm is presented which the service nodes in system make decisions without the knowledge of other service nodes. The randomized policy is applied to optimize system performance, and the policy-gradient iteration algorithm is used to compute the optimal admissioncontrol policy. Then, an operation mode switching mechanism is presented to detect the change of system and determine the switch epoch of operation mode. Through the numerical experiments, we demonstrate the efficiency of the presented approach.
Low-power Wireless Networks (LWNs) have become increasingly available for mission-critical applications such as security surveillance and disaster response. In particular, emerging low-power wireless audio platforms p...
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ISBN:
(纸本)9780769542980
Low-power Wireless Networks (LWNs) have become increasingly available for mission-critical applications such as security surveillance and disaster response. In particular, emerging low-power wireless audio platforms provide an economical solution for ad hoc voice communication in emergency scenarios. In this paper, we develop a system called Adaptive Stream Multicast (ASM) for voice communication over multi-hop LWNs. ASM is composed of several novel components specially designed to deliver robust voice quality for multiple sinks in dynamic environments: 1) an empirical model to automatically evaluate the voice quality perceived at sinks based on current network condition;2) a feedback-based Forward Error Correction scheme where the source can adapt its coding redundance ratio dynamically in response to the voice quality variation at sinks;3) a Tree-based Opportunistic Routing (TOR) protocol that fully exploits the broadcast opportunities on a tree based on novel forwarder selection and coordination rules;and 4) a distributed admission control algorithm that ensures the voice quality guarantees when admitting new voice streams. ASM has been implemented on a low-power hardware platform and extensively evaluated through experiments on a testbed of 18 nodes.
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