Energy Consumption and Environmental Implications of Wired Access Networks

Wired broadband access can be realized using various technologies, configurations and protocols. It is widely deployed and able to provide both high data rates and high reliability. These features are of strong importance for many advanced applications. Since the number of broadband subscribers worldwide grows exponentially, the power efficiency of access networks becomes an important issue. The main goal of this paper is to study the power consumption of different wired broadband access technologies including both those already widely used and those which are state-of-the art, but not yet widely deployed. Thus, results on power efficiency of different access networks such as hybrid fiber coax (HFC), digital subscriber line (DSL), 1 Gbit/s and 10 Gbit/s point-to-point Ethernet and passive optical networks (1G-PON and 10G-PON) are shown.

Network infrastructure plays a key role in the success of added services and in user satisfaction. It is widely accepted that Passive Optical Networks (PON) are the most promising, cost-effective, and high-performance access network solutions. Access networks are also commonly referred to as either ‘the last mile’ by the operators, or ‘the first mile of the network’ in IEEE terminology. The term ’mile’ is often related to the path portion that is used to reach the user from a network node, however access networks go as far as 20 km depending on the technology used. An access network comprises connections between different subscribers and a Central Office (CO), which is attached to the metro or core network. The wired technology deployed varies significantly from one country to another, i.e. Digital Subscriber line (xDSL), based on copper wires; Hybrid Fiber-coax (HFC), and optical fiber. The trends for Next Generation Access Networks (NGA) based on PON are: Wavelength Division Multiplexing (WDM), 10 Gb/s or more, and longer reach/higher splits. NGA must be able to cope with challenges, such as delivering diverse broadband services and facilitating the integration of different technologies. Moreover, NGA should provide higher bandwidths or further reduce the cost of existing delivering services, and serve as backhaul of wireless access networks (WiFi, WiMAX). The last one constitutes a relevant issue for the convergence between wireless and wired technologies.

_ Maritime transport accounts for around 3% of global anthropogenic greenhouse gas (GHG) emissions (Well-to-Wake). These GHG emissions must be reduced by at least 50% in absolute values by 2050 to contribute to the ambitions of the Paris Agreement signed in 2015. Switching to zero-carbon fuels made from renewable sources (hydro, wind, or solar) is seen by many as the most promising option to deliver the desired GHG reductions. However, renewable energy is a scarce resource that gives a much larger GHG reduction spent within other sectors. This study explores how to reach the IMO 2050 GHG targets exclusively through energy efficiency measures. The results indicate that by combining wind-assisted ship propulsion (WASP) with a slender hull form, fuel consumption and GHG emissions can be reduced by 30–35%, at a negative abatement cost for speeds exceeding 8 knots. Where the cost saving increases with the speed because at higher speeds, the fuel accounts for a higher share of the total cost, which implies that the cost saving goes from zero at 8 knots, to 5% reduction at 11 knots average speed to 14% reduction of total cost with 15 knots average speed. In comparison, GHG reductions through zero-carbon fuels will increase transport costs by 50–200%. Introduction From the first days of our civilization, sea transport has enabled regional and global trades. Today, sea transport accounts for 80% of the global trade measured in ton-miles (UNCTAD 2021) and 3% of greenhouse gas (GHG) emissions measured Well-to-Wake (Lindstad et al. 2021). More than 40% of this sea trade is performed by dry bulkers, making them the real workhorses of the sea. Even though sea transport is energy efficient compared to other transport modes, all sectors need to reduce their GHG emissions by at least 50% in absolute values by 2050 to contribute to the Paris Agreement (UNFCCC 2015). According to Bouman et al. (2017), the desired energy and GHG reductions can be achieved through: Design and other technical improvements of ships; Operational improvements; Fuels with zero or low GHG footprints; or a combination of these.

Over the past few years, telecommunication networks have experienced a dramatic shift from traditional voice-dominated traffic to data-oriented, application-based traffic. The access network or the last-mile connecting households or businesses to the internet backbone, have been recognized as a major bottleneck in todays network hierarchy. The ongoing demand for new access networks that support high-speed (greater than 100 Mb/s), symmetric, and guaranteed bandwidths for future video services has been accelerated and the search for a cost-effective optical access solution has yielded a number of possible solutions. To satisfy the required bandwidth over a 20-km transmission distance, single-mode optical fiber is a natural choice. Passive Optical Networks (PONs) are promising access solutions that will open the last-mile bottleneck bringing data rates of 100 Mb/s to 1 Gb/s to the end-users. The goal of this work is to provide a cohesive overview of research done in the area of Fiber In The Loop (FITL) optical access technology. Specifically, it explores the area of Passive Optical Network (PON) : its history, variants, architecture, and standards. Various passive optical components which make a passive optical network work, are also discussed. Some laboratory emulations on RF over PON showing noise, distortion, and fading in the channels are then carried on using the Vector Signal Generator SMIQ03B (Rhode & Schwarz), and the Wireless Communication Analyzer WCA380 (SONY Tektronix).

Dominant broadband access technologies today are Digital Subscriber Line (DSL) and hybrid fiber coaxial (HFC) networks. DSL leads, with global subscribers exceeding 100 million, while cable-modem subscribers worldwide total 55 million in 2005 [1]. Recently, fiber-to-the-home (FTTH) and fiber-to-the-curb (FTTC) scenarios are also on the rise. In all these access networks, optical fiber plays an imperative role. Fiber carries multimedia signals such as video, audio and Internet data with a combination of subcarrier multiplexed radio over fiber (SCM-ROF) and digital baseband formats. Despite the IPTV hype, the most bandwidth hungry video (especially HDTV) is predominantly transmitted in SCM-ROF format. In addition, wireless broadband multimedia access using the ROF technique is also on the rise. Newly released 71-76 GHz, 81-86 GHz, and 92-95 GHz bands for wireless multimedia delivery will trigger wide deployment of ROF technology. Therefore, ROF plays key role in both wired and wireless broadband multimedia access networks [2]. However, there are number of issues in the design and deployment of ROF links for multimedia access. Nonlinearity of the optical modulator (either direct or external); loss due to electrical-optical-electrical conversion and increasing intensity noise are key concerns. Some of our recent work involves with adaptive digital nonlinearity and noise cancelation [3], optical domain reduction in unmodulated carrier [4] and all optical de-multiplexing of closely spaced RF signals by Bragg grating filters [5] and multi system signals over fiber [6].

The improvement in energy efficiency (EE) and increasing consumption of renewable energy sources (RES) in manufacturing play an important role in pursuing sustainable development in the Baltic States and contribute to the transition to a low-carbon economy. This paper presents the results of a detailed analysis of the channel through which EE, along with structural activity changes, passes energy intensity and total energy savings and in combination with other key drivers results in reductions in greenhouse gas (GHG) emissions in manufacturing in Estonia, Latvia, and Lithuania during the period 2010–2020, taking into account the role of transformations in the energy and climate framework of the European Union (EU). The Fisher Ideal Index, the Kaya identity, the Logarithmic Mean Divisia Index (LMDI), and comparative analysis methods are used. The results of the impact analysis of key drivers on energy intensity showed different contributions towards improvements in EE and structural activity changes to changes in energy intensity in manufacturing, which decreased by 53.1% in Estonia, by 30.5% in Lithuania, and by 16.5% in Latvia. The dominant role of EE improvements on total energy savings is identified. The results of the GHG decomposition analysis showed that because of improvements in energy intensity, reductions in the share of fossil fuels, and increases in labour productivity, number of employees, and emissions intensity, the GHG emissions decreased by 35.5% in Estonia, 40.4% in Latvia, and 8.1% in Lithuania. The results confirm the need for new policies and the implementation of relevant commitments to save energy and increase the contribution of RES in all three countries.

Summary Corn‐ethanol production is expanding rapidly with the adoption of improved technologies to increase energy efficiency and profitability in crop production, ethanol conversion, and coproduct use. Life cycle assessment can evaluate the impact of these changes on environmental performance metrics. To this end, we analyzed the life cycles of corn‐ethanol systems accounting for the majority of U.S. capacity to estimate greenhouse gas (GHG) emissions and energy efficiencies on the basis of updated values for crop management and yields, biorefinery operation, and coproduct utilization. Direct‐effect GHG emissions were estimated to be equivalent to a 48% to 59% reduction compared to gasoline, a twofold to threefold greater reduction than reported in previous studies. Ethanol‐to‐petroleum output/input ratios ranged from 10:1 to 13:1 but could be increased to 19:1 if farmers adopted high‐yield progressive crop and soil management practices. An advanced closed‐loop biorefinery with anaerobic digestion reduced GHG emissions by 67% and increased the net energy ratio to 2.2, from 1.5 to 1.8 for the most common systems. Such improved technologies have the potential to move corn‐ethanol closer to the hypothetical performance of cellulosic biofuels. Likewise, the larger GHG reductions estimated in this study allow a greater buffer for inclusion of indirect‐effect land‐use change emissions while still meeting regulatory GHG reduction targets. These results suggest that corn‐ethanol systems have substantially greater potential to mitigate GHG emissions and reduce dependence on imported petroleum for transportation fuels than reported previously.

The panorama of the “Last mile” is rapidly evolving (or has recently evolved) in many countries under the pressure of demand for broadband Internet and new services requested both by the residential and the business subscribers. In the convergence towards ubiquitous IP and Ethernet in access and metro networks, legacy fixed-infrastructure access-network technology is transforming from xDSL to fibered access (in particular, passive optical networks), also thanks to new low-impact deployment techniques. On the other hand, alternative technological solutions, competing with fibre, offer less bandwidth but in change require lower investments (e.g. HFC, PLC) and/or ensure user mobility (e.g. WiMax, LTE, LEO/MEO satellites). This short tutorial paper provides a quick bird-eye overview of the evolution of the access network, from present to future technical solutions and technologies for implementing the “Last mile”. A comprehensive picture looking at the entire panorama of broadband access, and not just at a single technology or only at the latest findings, is of key importance, in our view, for understanding the changes and for adapting to the field reality when providing broadband to private users.

Energy Efficient Scheduling on Hybrid Multiple Access at Backend of FiWi

Urban water cycle systems(UWCS), including water treatment facilities, distribution facilities, sewers, and wastewater treatment facilities, are energy intensive and significant source of greenhouse gas (GHG) emissions, making the reduction of GHG emissions and the transition to eco-friendly energy essential. This study identifies specific GHG emission sources at each stage of the UWCS and proposes detailed methods to achieve a 40% reduction in GHG emissions, implement RE100, and attain Net Zero by employing insets and offsets. This study develops scenarios for insets and offsets based on the baseline process of the UWCS, and investigates potential pathways to reduce GHG emissions by quantifying emissions from each process. Internal insets, which are self-implemented and technical measures, are prioritized, while external offsets are applied to compensate for the remaining emissions. Internal insets include the application of anaerobic digesters and combined heat and power(CHP), improvements in energy efficiency of equipment, reduction in water pipe leakage, implementation of water footprint labeling, and installation of on-site photovoltaic system. External offsets comprise renewable energy certificates(REC), power purchase agreements(PPA), green hydrogen fuel for vehicles, natural sequestration improvement, and emission trading system. GHG emissions at each stage within the UWCS are quantified using modeling software. Based on these results, the effectiveness of insets and offsets in achieving a 40% GHG emissions reduction, Net Zero, and RE100 goal is analyzed. The baseline total GHG emissions for the UWCS are estimated at 4,732.8 tCO2eq/yr, of which 56.8% is identified as targets for internal insets, and the remaining 43.2% is reduced through external offsets. A 40% GHG reduction can be achieved through internal insets, and Net Zero can be attained by incorporating additionally applying external offsets. The total power demand of UWCS facilities and equipment is calculated as 572.8 kW. Renewable energy is generated through anaerobic digesters and CHP(116.1kW) as well as on-site PV(395.0 kW), while RE100 compliance is achieved by securing an aditional 61.7 kW through REC/PPA. Achieving Net Zero and RE100 requires prioritizing strategies for insets, offsets and efficient resource allocation. For this, the technical feasibility and self-implementation potential of reduction efforts and the external conditions for offsets, should be carefully reviewed to optimize implementation strategies. GHG reduction and renewable energy utilization in the UWCS are key priorities for addressing the climate crisis and achieving sustainable water resource management, requiring technological innovation and institutional support. The comprehensive and systematic application of GHG insets and offsets is the optimal approach to achieving these goals. Furthermore, modeling software serves as a key tool for quantifying GHG emissions and formulating concrete, viable GHG reduction strategies. In addition to the technical and institutional approaches proposed in this study, achieving Net Zero and implementing RE100 requires the integrated consideration of economic factors in the future.

Ethernet passive optical networks (EPONs) have emerged as the one of the most promising candidates for next-generation access networks. These new architectures couple low-cost optics with advanced edge electronics to offer vastly improved scalability over competing digital subscriber line and cable modem offerings. This paper proposes several novel architectural enhancements for EPON, which will help increase the viability of optical access over a broader range of subscriber access scenarios. Specifically, this paper proposes a two-stage EPON architecture that allows more end-users to share an optical line terminal link, and enables longer access reach/distances (beyond the usual 25 km distance). In addition, a new dynamic bandwidth allocation (DBA) algorithm is proposed to effectively allocate bandwidths between end users. This DBA algorithm can support differentiated services in a network with heterogeneous traffic. We conduct detailed simulation experiments to study the performance and validate the effectiveness of the proposed architecture and algorithms.

As concerns about energy consumption grow, the power consumption of the EPON becomes a matter of increasing importance.In respect of energy efficiency, the current standard has no management protocols aiming to reduce power consumption in EPONs.In this paper, we propose an Energy Management Mechanism (EMM) for downlink EPON systems.The proposed mechanism is designed to enhance the standardized control scheme in EPON with the objective to increase energy efficiency while satisfying diverse QoS requirements.The main idea is to put an Optical Network Unit (ONU) into the sleep mode and determine a suitable wakeup time scheduler at the Optical Line Terminal (OLT).A generic EPON system is considered, which is composed of an OLT and several ONUs that are EMM enabled.An energy consumption optimization problem aimed at saving energy is proposed and two heuristic sleep mode scheduling policies are addressed to solve it.The scheduling algorithms are tightly coupled with the upstream bandwidth allocation and downstream transmission scheduling together through an integrated approach in which awake time in ONUs is minimized.There is a trade-off decision between maximizing the power saving and guaranteeing the network performance at the same time.Simulation results show that an EMM-based EPON with well designed scheduling disciplines is essential to achieving significant energy saving while meeting the delay constraint.

The Empirical Case Against Asymmetric Regulation of Broadband Internet Access

We investigate the challenges in designing the network architecture for running EPON (Ethernet Passive Optical Network) Protocol over Coax, or EPoC in short. EPoC is the transparent extension of EPON over a cable operator's Hybrid Fiber-Coax (HFC) network, and uses a hybrid of optical and coaxial technologies to carry traffic to and from end-users and the Internet backbone. For managing and controlling such a hybrid network, a network operator will prefer to have a unified scheduling, management, and quality-of-service (QoS) environment that includes both the optical and coax portions of the network. This can be achieved by extending the EPON Medium Access Control (MAC) to run over the coax physical layer, to have a centralized end-to-end network control from the cable head-end to the end-users' premises. The use of the coax portion of the network is transparent to EPON protocol operation in the headend, as the same MAC runs over the entire network. In this article, we describe the architecture of EPoC, and outline how the EPON MAC Control, i.e., the EPON Multi-Point Control Protocol (MPCP) can be extended for designing an end-to-end Multi-Point MAC Control for EPoC. We explain the design of several MAC functions and their operation, including framing for coax, Ethernet frame fragmentation, generation of upstream and downstream Media Allocation Plans, and automatic discovery and registration of user equipment. With strong backing from both service operators and equipment vendors, EPoC is set to become a rapidly-evolving standard within the next few years, and the creation of the IEEE 802.3bn Task Force for EPoC is a major step in that direction.

With the growing interest on wireline network architectures for residential triple-play and business Ethernet services there is a renewed demand for efficient and reliable packet-based transport capabilities between the content providers and the end users. Voice and data traffic carried over a variety of access technologies is collected via technology-specific access networks (e.g., digital subscriber line [xDSL], passive optical network [xPON], and wireless fidelity [WiFi]). Metro and core networks need to aggregate the various user flows from different access network nodes and provide scalable and cost-effective distribution of various flow types (e.g., Internet access, voice, video on demand, and broadcast TV services) to the relevant service access points. Varying quality of service and resiliency requirements for these services are being reflected in a new breed of converged Ethernet and optical network elements with capabilities to interwork the bearer-planes of these two networking technologies seamlessly. Network elements based on Ethernet/Optical converged technology are able to select the most fitting mechanisms from each networking technology to meet the transport requirements for each individual service demand better while providing significantly enhanced implementation and operational efficiencies. This paper discusses network architecture models and network elements addressing these goals. © 2007 Alcatel-Lucent.