Xiaowen Dong

IP Over WDM Networks Employing Renewable Energy Sources

With network expansion, the energy consumption and CO2 emissions associated with networks are increasing rapidly. In this paper we propose an approach for energy minimization in IP over WDM networks and furthermore propose the use of renewable energy to further reduce the CO2 emissions at a given energy consumption level. We develop a Linear Programming (LP) model for energy minimization in the network when renewable energy is used and propose a novel heuristic for improving renewable energy utilization. Compared with routing in the electronic layer, routing in the optical layer coupled with renewable energy nodes significantly reduces the CO2 emission of the IP over WDM network considered by 47% to 52%, and the new heuristic introduced hardly affects the QoS. In order to identify the impact of the number and the location of nodes that employ renewable energy on the non-renewable energy consumption of whole network, we also constructed another LP model. The results show that the nodes at the center of the network have more impact than other nodes if they use renewable energy sources. We have also investigated the additional energy savings that can be gained through Adaptive Link Rate (ALR) techniques where different load dependent energy consumption profiles are considered. Our optimized REO-hop routing algorithm with renewable energy and ALR results in a maximum energy saving of 85% (average of 65%) compared to a current network design where all nodes are statically dimensioned for the maximum traffic in terms of IP ports and optical layer and hence consume power accordingly. Furthermore, when all the nodes have access to typical levels of renewable power we show that the associated reduction in non-renewable energy consumption reduces the networks CO2 emissions by 97% peak, 78% average.

On the Energy Efficiency of Physical Topology Design for IP Over WDM Networks

The energy consumption of information and communications technology networks is increasing rapidly as a result of the Internet expansion in reach and capacity. In this paper, we investigate energy-efficient physical topologies for backbone IP over wavelength-division multiplexing (WDM) networks. We develop a mixed integer linear programming model to optimize the physical topology of IP over WDM networks with the objective of minimizing the network total power consumption. We consider the National Science Foundation network topology and compare its energy consumption with the energy consumption of optimized physical topologies under different IP over WDM approaches and nodal degree constraints. We study the physical topology optimization under a symmetric full-mesh connectivity traffic matrix and an asymmetric traffic demand, where data centers create a hot node scenario in the network. We also investigate the power savings obtained by deploying topologies that eliminate the need for IP routers, including a full-mesh topology and a star topology. Simulation results show that the full-mesh and star topologies result in significant power savings of 95% and 92%, respectively. Furthermore, the optimization of the physical topology is investigated considering the presence of renewable energy sources in the network. The results show that optimizing the physical topology increases the utilization of the renewable energy sources.

Energy-efficient core networks

In this paper, we optimize core networks to minimize the embodied energy and the operational energy and introduce two measures for energy minimization in core content distribution networks: data compression in optical networks and locality in P2P networks. We investigate the impact of taking the embodied energy of network devices into account in the physical topology optimization and compare it to optimizing the physical topology considering operational energy only. The results show significant embodied energy savings up to 59%, resulting in a total energy saving of 47%. We also investigate energy-efficient data compression for optical networks and how to achieve a trade-off between the power consumption of computational resources and memory required to compress and decompress data and the network power savings. The results show that optimizing the data compression ratios in IP over WDM networks considering the non-bypass approach has saved up to 55% of the networks power consumption. Furthermore, we evaluate the power consumption of BitTorrent, the most popular P2P content distribution protocol, over IP over WDM networks and compare it to client/server (C/S) systems. The results reveal that the power-minimized BitTorrent converges to locality in order to achieve lower power consumption, resulting in 36% power savings compared to the C/S model.

Energy efficiency of optical OFDM-based networks

Orthogonal Frequency Division Multiplexing (OFDM) has been proposed as an enabling technique for elastic optical networks to support heterogeneous traffic demands. In this paper, we investigate the energy efficiency of rate and modulation adaptive optical OFDM-based networks. A mixed integer linear programming (MILP) model is developed to minimize the total power consumption of optical OFDM networks. We differentiate between two optimization schemes: power-minimized and spectrum-minimized optical OFDM-based networks. The results show that while similar power consumption savings of up to 31% are achieved by the two schemes compared to conventional IP over WDM networks, the spectrum-minimized optical OFDM is 51% more efficient in utilizing the spectrum compared to the power-minimized optical OFDM.

Energy Efficient Optical Networks with Minimized Non-Renewable Power Consumption

Recent studies have shown that the Information and Communication Technology (ICT) industry is responsible for about 2% of the global emission of CO 2 and this percentage is expected to increase as the internet expands in bandwidth and reach. In this paper we propose a hybrid-power IP over WDM network where renewable energy is used to reduce the CO 2 emission of IP over WDM networks. A Linear Programming (LP) model and a novel heuristic are developed to minimize the non-renewable power consumption in the “hybrid-power” IP over WDM network. The performance of the network is studied considering two topologies, the NSFNET and the USNET. Compared with routing in the electronic layer, the results show that routing in the optical layer coupled with using renewable energy significantly reduces the CO 2 emissions of the IP over WDM network by up to 73% for the NSFNET and 69% for the USNET, and the proposed heuristic has little impact on the QoS. We also develop an LP model to identify the impact of the location of nodes employing renewable energy on the non-renewable power consumption of the network. The results show that the optimum location of nodes employing renewable energy is determined according to the output power of the renewable energy sources and the power consumption of the nodes.

Energy-efficient IP over WDM networks with data centres

The presence of data centres in IP over WDM networks can create a hot node scenario leading to a significant increase in the power consumption of data centre nodes. In this paper, we investigate the power consumption associated with transporting data between data centres and end-users in IP over WDM networks. We study two problems. Firstly, we optimize the location of the data centres in the IP over WDM network so as to minimize the power consumption. Secondly, we investigate introducing renewable energy to IP over WDM networks with data centres and evaluate the problem of whether to locate data centres next to renewable energy or to transmit renewable energy to data centres. The results show that optimizing the data centre locations in the presence of renewable energy sources can save up to 71% of the power consumption.

Renewable energy in IP over WDM networks

Recent studies have shown that the Information and Communication Technology (ICT) industry is responsible for about 2% of the global emission of CO2 and this percentage is expected to increase as the Internet expands in bandwidth and reach. In this paper, we propose the use of renewable energy in IP over WDM networks to minimize CO2 emissions. A Linear Programming (LP) model is proposed to optimize the use of renewable energy. A novel heuristic is developed for improving renewable energy utilization based on Multi-hop-bypass. Compared with the Non-bypass heuristic, simulation results indicate that the CO2 emissions of the hybrid power IP over WDM network are reduced significantly, by 45% ∼ 55%, and the new heuristic has little impact on the QoS. In order to identify the impact of the number and the location of nodes that employ renewable energy on the non-renewable energy consumption of the network, we also develop another LP model. Simulation results show that using renewable energy at nodes at the centre of the network maximizes the benefit.

Low Carbon Emission IP over WDM Network

In this paper we propose a low carbon emission IP over WDM network where renewable energy is used to reduce the CO2 emissions at a given energy consumption level. We develop a Linear Programming (LP) model to minimize the non-renewable energy consumption of the network and propose a novel heuristic for improving renewable energy utilization. Compared with routing in the electronic layer, the results show that routing in the optical layer coupled with renewable energy nodes significantly reduces the CO2 emission of the IP over WDM network by up to 94%, and the new heuristic introduced has little impact on the QoS. In order to identify the impact of the number and the location of nodes that employ renewable energy on the non-renewable energy consumption of the whole network, we also build another LP model. The results show that the nodes at the centre of the network have more impact than other nodes if they use renewable energy sources.

Green IP over WDM Networks: Solar and Wind Renewable Sources and Data Centres

In this paper we propose the use of renewable energy in IP over WDM networks to reduce the non-renewable energy consumption and consequently the CO2 emission. A Linear Programming (LP) model and a novel heuristic, REO-hop, are developed for improving renewable energy utilization. The results show that the non-renewable energy consumption can be reduced by up to 73%. We also study IP over WDM networks with data centres and investigate the problem of whether to locate data centres next to renewable energy or to transmit renewable energy to data centres. Taking into account the electrical power transmission losses the results show that by optimizing the data centre locations such that the networks power consumption is minimized up to 71% of the networks power consumption can be saved.

Hybrid-power IP over WDM network

In this paper we propose a “hybrid-power” IP over WDM network where renewable energy is used to reduce the CO2 emissions. A novel heuristic is proposed to improve renewable energy utilization. Compared with routing in the electronic layer, the results show that routing in the optical layer coupled with renewable energy significantly reduces the CO2 emission of the IP over WDM network considered by 47% to 52%, and the new heuristic introduced hardly affects the QoS. The results also show that the nodes at the centre of the network have more impact than other nodes if they use renewable energy sources.