Myungsik Yoo

QoS performance of optical burst switching in IP-over-WDM networks

We address the issue of how to provide basic quality of service (QoS) in optical burst-switched WDM networks with limited fiber delay lines (FDLs). Unlike existing buffer-based QoS schemes, the novel offset-time-based QoS scheme we study in this paper does not mandate any buffer for traffic isolation, but nevertheless can take advantage of FDLs to improve the QoS. This makes the proposed QoS scheme suitable for the next generation optical Internet. The offset times required for class isolation when making wavelength and FDL reservations are quantified, and the upper and lower bounds on the burst loss probability are analyzed. Simulations are also conducted to evaluate the QoS performance in terms of burst loss probability and queuing delay. We show that with limited FDLs, the offset-time-based QoS scheme can be very efficient in supporting basic QoS.

Just-Enough-Time (JET): a high speed protocol for bursty traffic in optical networks

We investigate a high speed protocol called Just-Enough-Time (JET) based on a tell-and-go (TAG) protocol. It is suitable for bursty traffic where the duration of each burst is neither long enough to warrant circuit switching nor short enough to fit in a packet. The proposed JET protocol can efficiently utilize the bandwidth, reduce the latency and provide data transparency.

Optical burst switching for service differentiation in the next-generation optical Internet

In an effort to eliminate the electronic bottleneck, new optical switches/routers (hardware) are being built for the next-generation optical Internet where IP runs over an all-optical WDM layer. However, important issues yet to be addressed in terms of protocols (software) are how to develop a new paradigm that does not require any buffer at the WDM layer, as in circuit switching, and elimination of any layers between which exist mainly due to historical reasons. At the same time, such a paradigm should also efficiently support bursty traffic with high resource utilization as in packet switching. This article surveys design issues related to a new switching paradigm called optical burst switching, which achieves a balance between circuit and packet switching while avoiding their shortcomings. We describe how OBS can be applied to the next-generation optical Internet, and in particular how offset times and delayed reservation can help avoid the use of buffer, and support quality of service at the WDM layer.

Supporting multiple classes of services in IP over WDM networks

We consider the next generation optical Internet, where direct communication channels between IP entities are provided through an all-optical WDM layer. Since current IP provides only best effort service, supporting quality of service (QoS) has become a crucial issue. We propose a simple, yet efficient priority scheme to support basic QoS at the WDM layer of the optical Internet. Unlike existing approaches that depend on buffers (queues) and scheduling algorithms (e.g., fair queuing), our scheme does not mandate any buffer in the WDM layer in order to differentiate the services. The proposed scheme is based on the concept of using an offset time between a control (set-up) packet and the corresponding data burst as in optical burst switching (OBS). More specifically, by assigning different offset times to different classes, it is possible for a higher priority class to be isolated from lower priority classes. We quantify the offset time required for class isolation, and analyze the blocking probability of each class.

A novel switching paradigm for buffer-less WDM networks

Optical burst switching (OBS) is proposed to efficiently support IP over wavelength-division multiplexing (WDM). We describe various OBS protocols and in particular, one that can achieve high bandwidth utilization and low blocking probability in bufferless optical networks.

An in-Depth Survey of Visible Light Communication Based Positioning Systems

While visible light communication (VLC) has become the candidate for the wireless technology of the 21st century due to its inherent advantages, VLC based positioning also has a great chance of becoming the standard approach to positioning. Within the last few years, many studies on VLC based positioning have been published, but there are not many survey works in this field. In this paper, an in-depth survey of VLC based positioning systems is provided. More than 100 papers ranging from pioneering papers to the state-of-the-art in the field were collected and classified based on the positioning algorithms, the types of receivers, and the multiplexing techniques. In addition, current issues and research trends in VLC based positioning are discussed.

On an IP-centric optical control plane

This article presents an experimental study on adopting and integrating the existing IP protocols and mechanisms into an optical network control plane. Although there has been much research effort on the conceptual and functional requirements for the control of optical networks, this article focuses on the design and implementation of an optical control plane. The proposed control plane implements the key functions such as routing, signaling, protection/restoration, and quality of service.

Adaptive discontinuous reception mechanism for power saving in UMTS

We propose the ADRX (adaptive discontinuous reception) mechanism with the EPI (extended paging indicator) for power saving in the UMTS (Universal Mobile Telecommunications System). In the proposed mechanism, DRX period for each UE (user equipment) is individually and adaptively controlled by the EPI which is decided by node B considering the current traffic situation of each UE. Simulation results show significant improvement of power saving performance by the proposed mechanism as compared to the conventional fixed DRX

Efficient Video-on-Demand Streaming for Broadband Access Networks

We introduce three important factors for efficient video-on-demand (VoD) streaming strategy in broadband access networks such as a passive optical network (PON): an efficient streaming scheme for bandwidth savings, optimal use of deployed network bandwidth, and proactive use of user storage facilities. To achieve these goals, we propose efficient algorithms such as video adaptive streaming (VAST), video greedy adaptive streaming (VGAST), and video greedy adaptive streaming with proactive buffering (VGAST-PB). The VAST and VGAST algorithms use a patching scheme to save on network bandwidth for video streaming and increase the efficiency by adaptively changing the speed of patch streams and the patching window based on the time of the day and video popularity. VGAST-PB further improves the efficiency of VGAST by proactively buffering the popular videos. The proposed algorithms can be applied in fiber-to-the-x broadband access networks. To analyze the algorithms, we consider a typical 2.488 Gbps gigabit PON network providing VoD service to 512 households. We use a daily video request model and a video popularity model to determine the adaptive streaming speed and dynamic patching window. Numerical results show that, when the available network bandwidth is reduced below the required level due to background traffic, the efficient algorithms can con-siderably reduce the average user waiting time and the number of waiting requests.

TDOA-based indoor positioning using visible light

In this paper, we propose an indoor positioning system in which the visible light radiated from LEDs is used to locate the position of receiver. Compared to current indoor positioning systems using LED light, our system has the advantages of simple implementation, low cost, and high accuracy. In our system, a single photo diode receives pilot signals from LED panels on the ceiling. Then, the time differences of arrival of these pilot signals are used to estimate the position of the receiver. The system can be employed easily because it does not require embedding any ID to the pilot signal. In the paper, the estimation accuracy of the proposed system is analyzed through the simulation. The causes of estimation error are analyzed, and the estimation accuracy of the system in various conditions is shown by simulations.