NamUk Kim

Coordination of wavelength and time-window assignment in WDM-based TDM hybrid-PONs

In passive optical networks (PONs), the low effectiveness in terms of service utilization and network evolution have been important design issues. In this article, we introduce a hybrid access network architecture, so called scalable WDM-based Ethernet hybrid-PON (SWE-PON), which features a wavelength-division-multiplexed (WDM) feeder network using a combination of tunable laser device (TLD) and cyclic arrayed waveguide grating (AWG) and time-division-multiplexed (TDM) distribution network based on a reflective transmission mode. Necessary conditions needed to guarantee flawless packet transmission through normal WDM/TDM hierarchical PONs including the SWE-PON, are analyzed. We also propose a hierarchical fair time-window allocation mechanism which coordinates wavelength assignment and time-window bandwidth allocation so that high link utilization and fair bandwidth allocation are guaranteed in every multiplexing level.

Service differentiation scheme in OBS networks

In order to achieve service differentiation, especially loss differentiation, in optical burst switching (OBS) networks, we propose a dynamic fiber delay line (FDL) partitioning algorithm, which divides FDLs into several groups over a feed-forward output buffering architecture. In the proposed scheme, a plurality of traffic classes and FDL groups can be considered, and each FDL group is assigned to traffic classes, so that the target loss probabilities of classes are guaranteed. Also, the optimal number of FDLs for each FDL group by the proposed algorithm is decided in Poisson traffic environments. The extensive simulation results validate the effectiveness of the proposed dynamic FDL partitioning algorithm for the loss differentiation in OBS networks.

Analysis of effect of load-based excess bandwidth reservation on performances of differentiated services in E-PON

Performances of differentiated services in the upstream transmission of Ethernet passive optical network (E-PON) are affected by bandwidth reservation algorithm of an optical network unit, since data packets can be transmitted to an optical line termination only during the reserved transmission window. The effects of time-slot reservation on differentiated services are analysed and an adaptive class-based excess bandwidth reservation algorithm, called service quality pre-engagement (SQP), which reserves a time-slot based on the backlog queue and traffic arrival pattern of class is proposed. SQP applies the prediction-based bandwidth reservation to selected forward reservation classes (FRCs) which are determined by the introduced dynamic FRC selection. The proposed short-term service work-based time-slot reservation and long-term adaptive FRC selection optimise time-slot reservation according to traffic load of class. Analytic and simulation results show that this approach improves the performance of differentiated services, especially in terms of system buffer size, light-load penalty and service fairness, while guaranteeing high link utilisation and throughput.

Advanced multicast service scheduling mechanism with IGMP snooping in WDM-PON

In this paper, we deal with the multicast service management to efficiently support the broadcasting TV and the near real time high quality VoD (video on demand) service though the data communication networks. This is an emerging issue of the next generation network. Until now, several network architectures have been proposed but most of these have been concentrated on increase of the basic network bandwidth or induced the higher system complexity. The hybrid WDM-PON guarantees both kinds of traffic the independent and stable service by introducing the shared broadcast wavelength for multicast group traffic service. The proposed dynamic multicast group scheduling (DMGS) based on hybrid WDM-PON efficiently supports the common Internet traffic as well as the large number of multicast groups by maximizing the service share-index of registered multicast groups which uses the broadcast wavelength in real time

Performance enhancement of differentiated services in E PON: smaller buffer and efficient traffic service isolation

The performances of differentiated services in E-PON can be enhanced by the QoS based bandwidth reservation. With dynamic service tracking, the data buffer size and the light-load penalty are reduced with the reliable traffic isolation

Differentiated service in OBS networks using a dynamic FDL bank partitioning algorithm

In order to solve the differentiated service problem in optical burst switching (OBS) networks, we propose a dynamic fiber delay line (FDL) bank partitioning algorithm, which divides a FDL bank into several groups, using a feed-forward output buffering architecture. In the analysis, three classes and groups are considered for traffic and FDL, respectively, and each group is assigned to each class. This paper shows that the loss differentiation in OBS networks is easily accomplished in Poisson traffic environments when our dynamic algorithm is adopted.

Share Based-Channel Scheduling Algorithm for Multicast Video Delivery in WDM Optical Access Networks

One of the important issues of future convergence service design in access networks is the ability to support different kinds of video delivery services for high quality IP-TV and multicast Video on Demand (VoD). In this paper, we address how to efficiently allocate video transmission channels based on multicast management technology in shared wavelength division multiplexed-passive optical network (WDM-PON). The shared WDM-PON introduces a broadcast downstream wavelength to support multicast videos in the point-to-point WDM-PON. Based on the shared architecture and multicast management technologies, the proposed dynamic channel scheduling arbitrates transmission channels of videos. It uses the information of broadcast video share to maximize traffic share in the optical layer. By maintaining high video share, proposed algorithm supports the maximum number of high quality multicast videos without serious service interference to real-time videos, delay-able videos, and internet services. In addition, it also reduces the packet processing burden and buffer size of the optical line termination (OLT). The analytic and simulation results validate the effectiveness of the proposed algorithm.

Dynamic resource sharing protection using label stacking and burst multiplexing in optical burst switched networks

A protection and restoration mechanism is essential to provide reliable traffic transmission in networks, but it is not easy to apply existing protection mechanisms to optical burst-switching (OBS) networks, because of the unique properties of OBS. The authors introduce a 1:1 link-based protection that minimises burst losses by deflecting bursts until a source ingress router arbitrates a working path to a backup path when a link failure occurs. The authors also propose a genuine dynamic resource sharing (DRS) link protection in order to achieve high efficiency in network resource allocation and reliable protection simultaneously in OBS networks. DRS employs burst-multiplexing and label-stacking techniques in backup channel selection and always reserves an optimal number of backup channels according to the changes in traffic load in a working link and the quality of service (QoS) requirements of bursts. Simulation results show that the DRS can provide the same protection reliability with just half of the backup channels needed in a normal 1:1 protection in a light-load case, while guaranteeing the QoS requirements of class bursts. The authors show that this property also makes backup link sharing among a number of working links possible.

Evolutionary Optical Access Network: Port-share based Scalable WDM based Ethernet PON

Proposed scalable WDM based Ethernet PON aims to overcome small link capacity and ineffective link utilization of PONs by optimally combining TDM and WDM solutions while guaranteeing high port-share and flexibility required for evolutionary network.

Design and Analysis of Scalable WDM-Based Ethernet Hybrid-PON Architecture

To overcome the demerits of two passive optical networks; the small link capacity of the TDM-PON, and the ineffective link utilization of the WDM-PON; we propose a novel access network architecture featuring a WDM-based feeder network and a TDM-based distribution network. In this paper, we examine the design issues of the key constituent of SWE-PON (Scalable WDM-based Ethernet hybrid-PON) to validate its economic and practical feasibility. For flawless network operation, the wavelength tuning rule is investigated so that it does not collide between wavelengths from the tunable lasers belonging to the WDM coupler. Also, the potential problem between the tunable laser and the reflective operational device is analyzed in detail. From the numerical analysis and simulation, we demonstrate the variation of the network performance in terms of the upstream traffic delay and throughput of the ONU in accordance with the sharing structure of distribution network and the number of tunable laser devices (TLDs) at the feeder network.