Energy Efficiency In Optical Networks Research Articles

Energy-Efficient Regional Area Metropolitan Optical Access Network (RAMOAN) Using Modified Load Adaptive Sequence Arrangement (M-LASA) Methodology

Energy efficiency in optical networks is one of the important criteria to attain enhanced performance. Better energy efficiency can be attained in optical networks if the resources are properly scheduled. Polling sequences perform resource scheduling based on load requirements, and various methodologies have evolved in recent times for better efficiency. Load adaptive sequence arrangement (LASA) is one of the familiar and efficient methodologies adopted in various methodologies. However, the power consumption and idle time of optical network units are high which should be reduced to attain optimal network performances. Considering this, a modified LASA is presented in this research work for the regional area metropolitan optical access network (RAMOAN). The modified LASA is obtained by integrating the first-in-last-out polling sequence such that the proposed arrangement provides a better coverage radius, minimal power cost, maximum access reach, maximum energy saving, and minimal delay and energy cost. The better performance of the proposed approach is compared with traditional time and wavelength division multiplexed (TWDM), TWDM-protected, and RAMOAN with LASA through simulation analysis to validate the better performances of the proposed model.

ENERGY EFFICIENT TRANSMISSION USING OPTICAL ACCESS NETWORK: ISSUES AND CHALLENGES

Everlasting increase of connected devices and users in communication networks carry out enormous traffic volumes. This reason places the network in a position to fine tune the energy consumption in proposal and attentive operations. Optical transmission technologies are a momentous paradigm which brings down the overall energy consumption in communication networks. This advantage increases an interest on research to improve the energy saving opportunities of optical networks. Regardless of this most vibrant research few unanswered questions direct the researchers to set effort on resolving the issues in energy efficient optical networks. Shannon limit and parallelism to support higher capacities is essential in approaching optical systems also without reducing the network performance parameters such as latency, reliability and survivability, energy consumption of optical networks must be laid out as it affects quality of services. New generation network services like optical cloud and fixed mobile convergence have necessity to meet out the end-to-end energy optimization. All these factors enlighten research area towards energy efficiency in optical network transmission. This special research work reconnoiters and consolidates the earlier research models related to energy efficient transmission in optical networks

Online Scheduling Protocol Design for Energy-Efficient TWDM-OLT

The design of energy-efficient optical network units (ONUs) in passive optical networks (PONs) has been studied extensively in the literature. Time- and wavelength- division multiplexed PONs, a widely accepted future access technology, offer an additional opportunity to save energy at the OLT along with the existing energyefficient ONU design due to the idle periods (voids) created by scheduling. Existing proposals utilize few of the available wavelengths (active wavelengths) for scheduling, and energy efficiency is achieved by switching off the OLT receivers associated with the remaining wavelengths. In this paper we reason that, subject to a delay bound of the upstream data, the voids created due to scheduling in the active wavelengths remain unutilized and thus create ample opportunity for saving energy at the OLT. Further, we show that modifications of the conventional method provide a limited scope of utilizing these voids for energy efficiency. Thus, we deviate from the conventional methodology and propose a novel online scheduling protocol which aims at minimizing the number of voids in all wavelengths. Our results demonstrate a significant improvement in energy efficiency, as compared to existing proposals, without affecting the algorithmic complexity.

A Novel Approach to Reduce the Impact of Physical Layer Restrictions in Dynamically Switched Transparent Optical Networks

The dynamic switching of channels to adapt the capacity to the actually occurring traffic load is a promising method to improve the energy efficiency in optical networks. However, this approach is limited by the possible generation of optical power transients, which are able to disturb the transmission of the remaining channels. In transparent networks, spreading of transients can occur across several nodes. In this paper, we demonstrate the restrictions of the dynamic channel switching by the consideration of optical power transients and shows how to minimize these limitations.

Quality of Service Provisioning and Energy Minimized Scheduling in Software Defined Flexible Optical Networks

The over-provisioning of capacities in optical networks is not a sustainable approach in the long run. In this paper, we propose a software defined networking scheme for quality of service provisioning through energy efficient assignment of optical transponders, employing bandwidth variable distance adaptive modulation and coding. Our scheme enables avoiding over-provisioning of transponder capacity as well as short-term major changes in equipment allocation for networks with dynamic traffic. We make use of the seasonal auto-regressive integrated moving average model to forecast the statistics of network traffic for an arbitrary time span based on the requirements and the constraints of the service provider. The quality of service measure is defined as the probability of congestion at the core router ports. A stochastic linear programming approach is used to provide a solution for energy efficient assignment of optical transponders and electronic switching capacity while ensuring a certain level of quality of service to core routers. The scheduling of optical lightpath capacities is performed for the entire duration of time under consideration, whereas the scheduling of electronic switching capacities is performed based on the short-term dynamics of the traffic. Numerical results show up to 48% improvement in the energy efficiency of optical networks and 45% reduction in the number of optical lightpaths through the implementation of the proposed technique, compared to a design based on employing conventional fixed optical transponders and no traffic rerouting, where both schemes satisfy the congestion probability requirements.

Special issue on energy-efficient optical networks

Communication networks continue to experience an increase in traffic volumes, number of connected devices, and users. For this reason, the energy consumption due to the communication infrastructure became an important parameter to be carefully considered and optimized during both network design and live operations. In this paradigm, optical transmission technologies offer the possibility to significantly lower the overall energy consumption level of communication networks. For this reason, there is a growing interest on how to take advantage of the energy-saving opportunities provided by optical networks. In addition, there are also parallel research efforts targeting the improvement of the energy efficiency of optical networks themselves. Despite this very vibrant research area, there are still a number of open questions that need to be addressed and new research directions have been recently opened in the field of energy-efficient optical networks. For example, the energy consumption levels in an optical network cannot be lowered at the expenseof other networkperformanceparameters (e.g., connection survivability, latency, average component reliability levels). As a result, energy-efficient schemes in optical networks have now been tailored to limit their impact on the Quality of Service (QoS) level of the provisioned connections. New network architectures have also been considered

Delay guaranteed VoD services over group-based integrated fiber-wireless (FiWi) access networks with energy efficiency

In group-based fiber-wireless (FiWi) access networks, where wireless clients are divided into several groups according to their interested Internet services, VoD services will meet new challenges considering the diversity of video requesting probability for each wireless group. In this paper, we categorize wireless groups into “video-hot” group with great interest in VoD services and “video-cold” group with infrequent video requesting. For video requests from “video-hot” groups, we firstly propose an energy-efficient optical network unit (ONU) selection approach to reduce ONU power consumption by selecting a subset of ONUs to support such requests, then our previously proposed rebroadcast and patching scheme can be effectively applied. For video requests from “video-cold” groups, a batched multicasting scheme is presented for energy and bandwidth saving. Both of the VoD schemes mentioned in this study are with the aim to minimize worst-case playback delay (WPD) which is particularly important as Internet users. In view of that some ONUs may need to handle video requests from two kinds of group, optimal ONU channel assignment aims to minimize weighted overall WPD is also studied. The efficiency of the work is finally demonstrated by the simulations.

Minimizing Energy and Cost in Fixed-Grid and Flex-Grid Networks

Core networks offer high capacities, thanks mainly to the optical technologies they utilize, but they consume a non-negligible amount of energy. The traffic volume in metro and core networks is forecast to grow at very high rates, exceeding 30% per year for the next five years, and if the corresponding energy requirements grow analogously, they will sooner rather than later form a bottleneck for network communications. Thus, energy efficiency in optical networks is mandatory for the sustainability of the future Internet. The objectives of the current work are to identify the main causes of energy consumption for current fixed-grid wavelength division multiplexing and future flex-grid optical networks, and to propose and compare techniques for improving their energy efficiency. Toward this end, we carried out a comparative study of energy efficiency of flex-grid networks and fixed-grid single-line-rate and mixed-line-rate networks. Under realistic network scenarios, we calculated the energy consumption of the different components of the optical layer and demonstrated that by using energy-aware techniques in planning such networks, we can achieve significant power savings. Since energy prices are location dependent, especially in large networks, e.g., over continents, we show that accounting for such information can increase the cost savings.

Analysis of Performance Degradation in Sleep-Mode Enabled Core Optical Networks [Invited

Energy efficiency is an important target for the management of wavelength-division-multiplexing-based core optical networks. A possible power management strategy for energy-efficient optical networks consists in putting opto-electronic devices (transponders and regenerators) into a low power mode, called sleep or idle, or even turning them off, during low traffic periods. It has been shown that sleep-mode enabled transponders and regenerators yield to substantial energy savings; however, their nonnegligible wake-up time may degrade the network performance in terms of the blocking probability of the connections. Opaque networks, in which transponders are utilized at each node in the end-to-end path, are especially prone to such degradations since multiple network nodes may simultaneously exhaust their pool of transponders due to long wake-up times, increasing the blocking probability. On the other hand, these degradations are less severe in transparent networks. In this paper, we evaluate how the duration of the wake-up time affects the performance of the network in terms of blocking probability depending on its architecture (transparent, translucent, or opaque) and the dynamicity of the traffic. Additionally, we propose a novel routing algorithm to mitigate the blocking probability due to the wake-up time. The benefits of the proposed algorithm are highlighted through extensive results.

Design of energy efficient optical networks with software enabled integrated control plane

The growing energy consumption has posed new challenges for the future development of networks. Some earlier work has proposed solutions to improve energy consumption based on the existing control plane, for example, node/links sleeping. This study presents a new possibility to reduce network energy consumption by proposing a new integrated control plane structure utilising Software Defined Networking technologies. The integrated control plane increases the efficiencies of exchanging control information across different network domains, while introducing new possibilities to the routing methods and the control over quality of service (QoS). The structure is defined as an overlay generalised multi-protocol label switching (GMPLS) control model. With the defined structure, the integrated control plane is able to gather information from different domains (i.e. optical core network and the access networks), and enable energy efficiency networking over a wider area. In the case presented, the integrated control plane collects the network energy related information and the QoS requirements of different types of traffic. This information is used to define the specific group of traffic's (flow's) routing behaviours. With the flexibility of the routing structure, results show that the energy efficiency of the network can be improved without compromising the QoS for delay/blocking sensitive services.

Energy-efficient optical network units for OFDM PON based on time-domain interleaved OFDM technique.

We propose and experimentally demonstrate a new scheme to reduce the energy consumption of optical network units (ONUs) in orthogonal frequency division multiplexing passive optical networks (OFDM PONs) by using time-domain interleaved OFDM (TI-OFDM) technique. In a conventional OFDM PON, each ONU has to process the complete downstream broadcast OFDM signal with a high sampling rate and a large FFT size to retrieve its required data, even if it employs a portion of OFDM subcarriers. However, in our scheme, the ONU only needs to sample and process one data group from the downlink TI-OFDM signal, effectively reducing the sampling rate and the FFT size of the ONU. Thus, the energy efficiency of ONUs in OFDM PONs can be greatly improved. A proof-of-concept experiment is conducted to verify the feasibility of the proposed scheme. Compared to the conventional OFDM PON, our proposal can save 17.1% and 26.7% energy consumption of ONUs by halving and quartering the sampling rate and the FFT size of ONUs with the use of the TI-OFDM technology.

Traffic Grooming for IP-Over-WDM Networks: Energy and Delay Perspectives

As energy consumption has become a major concern of networks, traffic grooming studies on Internet protocol over wavelength division multiplexing (IP-over-WDM) networks have been revisited for energy-efficient optical network applications. Traffic grooming techniques can save on the number of installed lightpaths and corresponding IP router line cards at the cost of traffic processing overhead. Energy awareness in networking device development has initiated improvement of the energy-traffic proportionality of networking devices. Accordingly, networks will consist of networking devices with a wide range of energy-traffic proportionalities. Therefore, previously known traffic grooming techniques may not achieve energy-efficient networking in high energy-traffic proportional networks. Moreover, the traffic grooming technique tends to prefer longer paths, which are responsible for longer transmission delays. These two concerns trigger investigation of new aspects of heuristic traffic grooming algorithms for green and low delay optical networks consisting of network devices with diverse energy-traffic proportionalities. This paper demonstrates that a heuristic traffic grooming algorithm enhanced by comparison with direct bypass routing improves both energy and delay performances in a high energy-traffic proportionality regime. A hottest-first sorting policy in flow provisioning can further improve delay performance even in a low energy-traffic proportionality regime.

Guest Editorial Energy-Efficiency in Optical Networks

The articles in this special issue focus on energy efficiency techniques deployed in optical fiber networking.

Call for Papers - IEEE Journal on Selected Areas in Communications: Energy-Efficiency in Optical Networks

Call for Papers - IEEE Journal on Selected Areas in Communications: Energy-Efficiency in Optical Networks

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 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 multicasting in TDMA PONs

Multicast transmission is utilized in Time Division Multiple Access TDMA Passive Optical Networks PONs to efficiently and selectively send downstream data to subsets of users. For example, multicast can be exploited in open access PONs to offer various services provided by different providers to the end-users. In this scenario, the minimization of the energy consumption, which is one of the greatest contributors to PON CAPEX, would benefit not only service providers but also end-users.This paper proposes an energy efficient multicasting solution based on energy efficient optical network units ONUs. Energy savings are achieved by setting to sleep mode the ONUs that need not receive downstream data, i.e. are not subscribed to a multicast group. Sleep mode is combined with an optimal multicast group scheduling to minimize the transitions from sleep to active mode, which consume power for achieving synchronization.Results show that energy efficient multicast transmission reduces the energy consumption with respect to the current broadcast-based transmission. The improvement is more significant when only one user is connected to an ONU i.e., FTTH than when several users are connected to the same ONU i.e., FTTB. This is due to the fact that the higher is the number of subscribers connected to an ONU the higher is the likelihood that an ONU must be active most of the time.

Sleeping Link Selection for Energy-Efficient GMPLS Networks

To improve the energy efficiency of optical networks, strategies and technologies should aim at ensuring a (low) power consumption proportional to the network utilization. To achieve such aim, this paper proposes the support of sleep mode in the links of a wavelength-switched optical network with generalized multiprotocol label switching control plane. A centralized strategy (to be performed at the Path Computation Element-PCE) and a distributed strategy are proposed to dynamically select the link to be set to sleep. Performance of the proposed strategies is evaluated for different parameter settings. Results show a significant reduction of the overall power drained by the optical devices with both strategies and a contained impact on lightpath blocking probability. The tradeoff between blocking and energy saving of the two strategies is discussed to derive the most energy-efficient and energy-proportional strategy, with negligible impact on the quality of service.