In this paper, we propose, implement, and evaluate a simple yet powerful estimation method for the quality of service of a large-scale Wi-Fi network, which is achieved using our passive and low-complexity measurements. Specifically, our proposed method estimates a time-varying frame error rate at an access point (AP) by counting null function data frames, which are emitted periodically by stationary user equipments (UEs), such as mobile phones and tablets. We implemented our method as a user-level script and a production-level firmware. Our real-world measurements in an uncontrolled 1500-seat hall demonstrated that our method exhibited high scalability against the increase in the numbers of APs and UEs with the aid of its simple structure and was capable of detecting the quality-of-service loss induced by an unexpected dynamic frequency selection. INDEX TERMS IEEE 802.11, Wi-Fi, passive estimation, quality of service (QoS), frame error rate (FER), large-scale network. D. RETRY-RATIO-BASED THROUGHPUT ESTIMATION [20], [22] YASUHIRO OHISHI (M'19) received the B.E.
With rapid spread of virtualization technologies, Live migration which provides the ability to migrate a running virtual machine (VM) among physical hosts without interruption. Especially, Global Live Migration (GLM) which enables to migrate VM across the geographically-distributed Wide Area Networks (WANs) is an essential step towards development of the inter-cloud environment. However, GLM gets a bit complicated for network configuration compared with ordinary live migration. We have already proposed the GLM method which implements IP mobility support architecture with multiple interfaces to enable live migration among distributed sites consisting of different IP network segments. However, there is no sufficient consideration about the management of smooth handoff for the VM migration on the Internet. In this paper, we propose a mobility management system for GLM, and integrate into our developed nation-wide virtualization infrastructure. The proposed system enables VMs seamless handoff without any modification of the hypervisor while keeping network configuration of the migrating site. Performance evaluation shows the processing overhead of the proposed management system with GLM among multiple sites which are more than 600 km distant. As a result, we confirm that the proposed system provides smooth handoff for the VM on the widely-distributed environment if the proposed system is implemented.
In videoconferencing, which means a small group meeting, interactive distance learning and so on, there is a requirement to get required video at remote site freely and easily by local control of a remote camera. However, there is some delays between camera control operations at a remote site and actual video images displayed on a local screen. Delays are caused by network delays between sender and receiver and by video compression delays. To operate a remote camera interactively, a user must control the device considering these delays.In this paper, we describe these problems in the case of videoconferencing and develop a real-time camera control system to solve them. Our approach is not reduce delays but to show delays for users by some indication under current environment. With our proposed system, a user can easily operate a remote camera without considering network and compression delays. We use a new camera control protocol designed by us in our system. We describe a prototype system and its evaluation used in distance learning, too.
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