Pulak Chowdhury

Building a Green Wireless-Optical Broadband Access Network (WOBAN)

Access networks consume a significant portion of overall Internet energy consumption. With the increase of bit-rate requirements in access networks, future-proof access technologies should be energy efficient. In this paper, we show how we can build a very high-throughput “green” hybrid wireless-optical broadband access network (WOBAN). We devise novel energy-saving techniques for WOBAN to improve its energy efficiency and network utilization. We present a mixed integer linear program (MILP) model, which acts as a benchmark for evaluating our techniques. We analyze the impact of energy-aware design and protocols on the performance of WOBAN over dynamic traffic profiles. Illustrative numerical examples show that, with suitable design parameters, we can efficiently reduce energy consumption in WOBAN without significantly impacting the network performance.

Green Provisioning for Optical WDM Networks

Since the Internet consumes a large (and increasing) amount of energy, “green” strategies are desirable to help service providers (SP) operate their networks and provision services more energy efficiently. We focus on green provisioning strategies for optical wavelength-division multiplexing networks. A number of approaches from component layer to network layer are discussed, which should help improve the energy efficiency of the networks. Then, we consider a typical optical backbone network architecture, and minimize the operational power for provisioning. Typically, operational power depends on strategy (e.g., optical bypass versus traffic grooming), operations (e.g., electronic domain versus optical domain), and route. We analyze the constituents of operational power in various scenarios, and discuss the opportunities for energy savings. We propose a novel auxiliary graph, which can capture the power consumption of each provisioning operation. Based on the auxiliary graph, we develop a power-aware provisioning scheme to minimize the total operational power. Performance evaluation shows that our scheme always needs the least operational power, with comparison to a direct-lightpath approach and a traffic-grooming approach. The result also suggests proportional power consumption by operations (network equipment) and end-node traffic grooming to fully exploit the power-saving potential of optical networks.

On the Design of Energy-Efficient Mixed-Line-Rate (MLR) Optical Networks

With increasing energy consumption of the Internet, it is now imperative to design energy-efficient network architectures and protocols. Optical technologies have significant promise in improving the energy efficiency of network infrastructures. Future optical backbone networks will be heterogeneous in nature where a single link may carry various line-rate signals. This mixed-line-rate (MLR) network architecture is shown to be cost effective in satisfying heterogeneous traffic demands. In this study, we present mathematical models that can act as references for designing energy- and cost-efficient MLR optical networks. We also perform a comparative study of the energy efficiency of MLR and special cases of MLR design, named as single-line-rate networks (where all the links have same line rates). We explore the scenarios where the MLR networks minimize energy consumption. Finally, we investigate the relationship between energy-minimized and cost-minimized MLR network design.

Hybrid wireless-optical broadband access network(woban) : prototype development and research challenges

The hybrid wireless-optical broadband access network is emerging as a promising technology to provide economical and scalable broadband Internet access. In this cross-domain network architecture, end users receive broadband services through a wireless, mesh front end that is connected to the optical backhaul through gateway nodes. In this article, we present the architecture and functional characteristics of a WOBAN prototype built in the Networks Lab at UC Davis. We discuss research challenges for hybrid networks based on our experimental observations.

Energy optimization in IP-over-WDM networks

The energy crisis and environmental protection are gaining increasing concern in recent years. ICT (Information and Communication Technology) has a significant impact on the total electricity consumption all over the world. Telecom networks, being an important part of ICT, consume significant energy since more network equipment is deployed annually. Specifically, in IP-over-WDM networks, energy is consumed by network elements at both IP and WDM layers. Routers in the IP layer are the largest energy consumer in this architecture, and current network infrastructures have no energy-saving scheme, so a large amount of energy is wasted when traffic load is low. In this paper, we propose a novel approach to save energy in IP-over-WDM networks by shutting down idle line cards and chassis of routers based on time-of-the-day network traffic variation. A method based on Mixed Integer Linear Programming (MILP) is proposed to ensure that the energy cost incurred by the IP routers and optical cross-connects is minimized by our approach. We also propose some possible approaches to minimize potential traffic disruption when the network elements are shut down.

On the energy efficiency of mixed-line-rate networks

We present an approach to evaluate energy efficiency of mixed-line-rate (MLR) optical networks. A comparative study of energy efficiency of MLR and single-line-rate (SLR) networks shows that MLR is more energy efficient than SLR networks.

Software-defined optical networks (SDONs): a survey

This paper gives an overview of software-defined optical networks (SDONs). It explains the general concepts on software-defined networks (SDNs), their relationship with network function virtualization, and also about OpenFlow, which is a pioneer protocol for SDNs. It then explains the benefits and challenges of extending SDNs to multilayer optical networks, including flexible grid and elastic optical networks, and how it compares to generalized multi-protocol label switching for implementing a unified control plane. An overview on the industry and research efforts on SDON standardization and implementation is given next, to bring the reader up to speed with the current state of the art in this field. Finally, the paper outlines the benefits achieved by SDONs for network operators, and also some of the important and relevant research problems that need to be addressed.

Energy-efficient content distribution over telecom network infrastructure

Energy consumption of content-delivery networks employing optical infrastructure is improved if some backbone nodes can also host content. In a typical scenario, up to 18% energy is saved using this approach vs. monolithic datacenter architecture.

Exploiting wireless connectivity for robustness in WOBAN

This article studies how next-generation optical access networks can exploit the properties of wireless connectivity to provide improved quality of service to users, and reports on a corresponding experimental prototype as well. Optical access networks using the passive optical network architecture are being increasingly deployed worldwide for fiber-to-the-home/business applications. While a PON can support higher data rates, it suffers from its tree architecture since it is vulnerable to a fiber cut on its tree¿s trunk, which will disrupt service to its users. However, by exploiting the properties of wireless connectivity, such as a wireless mesh in the front-end, the network can be made more robust. In case of a network element failure, an alternate path through the wireless-wireline integrated network may be selected, if it exists. Such a network can provide reliable high-capacity connectivity to untethered wireless devices which may be mobile as well. For such wireless-optical broadband access networks, we study a Risk-Aware Routing (RAR) algorithm to make it fault-tolerant and self-healing in case of failures. We also report on results from an experimental prototype developed in our laboratory.

Hybrid Wireless-Optical Broadband Access Network (WOBAN)

Hybrid wireless–optical broadband access network (WOBAN) is a promising architecture for future access networks. It combines the advantages of two diverse technologies – an optical back end drives a wireless mesh in the front end. It is a cost-effective solution compared to traditional optical access networks since fiber does not need to penetrate to the end user. WOBAN offers untethered flexibility due to its wireless mesh in the front end; yet it provides high transport capacity compared to traditional wireless solutions because of its optical back end. This chapter defines WOBAN, reviews different flavors of its architecture, and provides a comprehensive outline of various design models, coupled with efficient protocols to manage the network. It also argues why the combination of optical and wireless technologies should provide an improved solution for future network design.