Chien Aun Chan

Energy-efficiency of optical network units with vertical-cavity surface-emitting lasers.

The energy savings of 10 Gbps vertical-cavity surface-emitting lasers (VCSELs) for use in energy-efficient optical network units (ONUs) is critically examined in this work. We experimentally characterize and analytically show that the fast settling time and low power consumption during active and power-saving modes allow the VCSEL-ONU to achieve significant energy savings over the distributed feedback laser (DFB) based ONU. The power consumption per customer using VCSEL-ONUs and DFB-ONUs, is compared through an illustrative example of 10G-EPON for Video-on-Demand delivery. Using energy consumption models and numerical analyses in sleep and doze mode operations, we present an impact study of network and protocol parameters, e.g. polling cycle time, network load, and upstream access scheme used, on the achievable energy savings of VCSEL-ONUs over DFB-ONUs. Guidance on the specific power-saving mode to maximum energy savings throughout the day, is also presented.

Energy efficient content distribution for VoD services

The energy consumption of VoD services arising from storage and transport of video contents stored in different content placement locations is investigated. Our results provide insight into content placement strategies that improve energy efficiency.

Methodologies for assessing the use-phase power consumption and greenhouse gas emissions of telecommunications network services.

Internet traffic has grown rapidly in recent years and is expected to continue to expand significantly over the next decade. Consequently, the resulting greenhouse gas (GHG) emissions of telecommunications service-supporting infrastructures have become an important issue. In this study, we develop a set of models for assessing the use-phase power consumption and carbon dioxide emissions of telecom network services to help telecom providers gain a better understanding of the GHG emissions associated with the energy required for their networks and services. Due to the fact that measuring the power consumption and traffic in a telecom network is a challenging task, these models utilize different granularities of available network information. As the granularity of the network measurement information decreases, the corresponding models have the potential to produce larger estimation errors. Therefore, we examine the accuracy of these models under various network scenarios using two approaches: (i) a sensitivity analysis through simulations and (ii) a case study of a deployed network. Both approaches show that the accuracy of the models depends on the network size, the total amount of network service traffic (i.e., for the service under assessment), and the number of network nodes used to process the service.

Improving Energy Efficiency of Video on Demand Services

The energy consumption of the Internet is anticipated to be one of the main contributors to global energy consumption in the coming decades. As a result, renewed attention has been given to the energy efficient design and operation of network services. The video on demand (VoD) service is expected to be one of the most prominent services through the Internet in the near future. Due to the enormous energy consumption arising from storage and transport of movies, energy efficient design and operation of VoD systems are important considerations. In this paper, we formulate energy consumption models to analyze the energy consumption arising from storage and transport of movies in VoD systems. We consider five strategic content placement locations located at different levels of the video distribution network and we comparatively analyze the energy consumption of storage and transport when the movies are stored and delivered from these locations. Moreover, we derive thresholds for movie request arrival rates which determine whether replication of a movie in a given content placement location is energy efficient and whether turning ON a set of content storages located at a particular level of the network is energy efficient. By numerically analyzing the energy consumption models, we show that the energy efficiency of VoD services can be significantly improved by delivering movies from the most energy efficient content placement locations in the network. We show that this can be achieved by designing and operating VoD systems based on our derived thresholds which optimize the energy efficiency of VoD services for all user request arrival rates.

Remote Repeater-Based EPON With MAC Forwarding for Long-Reach and High-Split-Ratio Passive Optical Networks

The Ethernet passive optical network (EPON) is one of the most viable optical access technologies for the provision of broadband services to users. However, the scalability of EPON has become a limiting factor in realizing network architecture with large coverage and a high number of subscribers. EPONs with longer reach and higher split ratios have been successfully demonstrated by researchers to overcome the physical limitations of reach and split ratio of the standard PON architecture. Nevertheless, the 1 Gb/s bandwidth that is shared among a larger number of users degrades the efficiency of EPON especially in terms of the data rate utilized by each user. In this paper, we propose a simple active remote node (RN) with a media access control (MAC) forwarding scheme for an EPON network to achieve improved network performance and overcome bandwidth limitations arising from higher split ratios. The scheme works in conjunction with EPON protocols and does not modify the underlying functionalities of the network. The simulation results show a large improvement in latency (up to 90 ms of improvement) and up to 18% of enhancement in capacity or a 16% increase in the number of users with the use of the active RN structure.

Local-Traffic-Redirection-Based Dynamic Bandwidth Assignment Scheme for EPON With Active Forwarding Remote Repeater Node

The Ethernet passive optical network (EPON) has been considered as one of the most suitable next-generation optical access solutions. As a time-division multiplexing PON (TDM-PON) technology, the transmission media of EPON is shared among multiple users. Therefore, medium access control (MAC) protocol plays an important role in enabling a dynamic bandwidth assignment (DBA) mechanism that provides efficient and fair utilization of the PON resources. However, the DBA mechanism implemented in products is open for vendor customization. In this paper, we propose a novel local-traffic-prediction-based dynamic bandwidth assignment (LT-DBA) mechanism applicable in a remote-repeater-based EPON system with active forwarding. The LT-DBA aims to improve the bandwidth utilization and average packet delay performance of EPON in upstream transmission in comparison to conventional bandwidth assignment techniques such as static bandwidth assignment (SBA) and the interleaved polling algorithm (IPACT), leading to a more efficient PON system.

Active Remote Node with Layer Two Forwarding for Improving Performance of EPON

In this paper, we propose a simple active remote node (RN) with layer two forwarding scheme for EPON. The RN discards unwanted frames and redirects local-intra-subnet traffic to increase the network efficiency. We analyze and discuss the functionalities of the RN in detail and present simulations using an EPON structure of 16 ONUs with 4 splits to prove the feasibility of the scheme. The simulation results show a large improvement in latency and capacity with active RN structure. We also explain the use of EPON protocols such as MPCP and DBA is crucial in the implementation of this scheme.

Provision of Independent Services in WDM-Passive Optical Networks using Closely Separated Dual Baseband Channels

We demonstrate a simple scheme for the generation and separation of two independent high bandwidth baseband optical channels using a single laser and modulator for provision of independent services in WDM passive optical networks.

Dynamic Power Management at the Access Node and Customer Premises in Point-to-Point and Time-Division Optical Access

In order to achieve the maximum power-saving performance in optical access networks, all network elements including the access node or optical line terminal (OLT) and the optical network unit should be considered. In this paper, appropriate power-saving mechanisms are determined for each network element in point-to-point (PtP) and time-division-multiplexed passive optical network (TDM-PON) systems to maximize the achievable power-saving performance while satisfying the quality-of-service requirements for different applications. By applying these power-saving mechanisms in PtP and TDM-PON systems, it is found that 1) the power consumption of OLTs in the central office is reduced by up to 51% and 38%, respectively, and 2) the total power consumption per subscriber is reduced by up to 61.5% and 67%, respectively. Using simulations, the most energy-efficient optical access network technology for different Internet applications is also identified.

Generation and Separation of Closely Separated Dual Baseband Channels for Provisioning of Independent Services in WDM-PON

This letter presents a novel technique that enables simple provisioning of independent services in wavelength-division-multiplexed passive optical networks. The technique uses a single laser and modulator for generation and a periodic passive filter for separation of two closely separated baseband channels. We present experimental results of the bit-error-rate performance for the two 1.5-Gb/s independent service channels at a frequency separation of only 6 GHz.