Presentación realizada en el PhD Seminar del ITS 2011 en Budapest. ICTs (Information and Communication Technologies) currently account for 2% of total carbon emissions. However, although modern standards require strict measures to reduce energy consumption across all industrial and services sectors, the ICT sector also faces an increase in services and bandwidth demand. The deployment of Next Generation Networks (NGN) will be the answer to this new demand; more specifically, Next Generation Access Networks (NGANs) will provide higher bandwidth access to users. Several policy and cost analyses are being carried out to understand the risks and opportunities of new deployments, but the question of what role energy consumption plays in NGANs seems off the table. Thus, this paper proposes a model to analyse the energy consumption of the main fibre-based NGAN architectures: Fibre To The House (FTTH), in both Passive Optical Network (PON) and Point-to-Point (PtP) variations, and FTTx/VDSL. The aim of this analysis is to provide deeper insight on the impact of new deployments on the energy consumption of the ICT sector and the effects of energy consumption on the life-cycle cost of NGANs. The paper also presents an energy consumption comparison of the presented architectures, particularised to the specific geographic and demographic distribution of users of Spain but easily extendable to other countries

Coomonte Belmonte, Rafael

Servicio de Coordinación de Bibliotecas de la Universidad Politécnica de Madrid

A SIMPLIFIED ENERGY CONSUMPTION MODEL  
FOR FIBRE-BASED  
NEXT GENERATION ACCESS NETWORKS 
 
2nd PhD Seminar of International Telecommunications Society 
21-22 September 2011, Budapest (Hungary) 
Project financed by the European Investment Bank (EIB) 
Disclaimer: This document was prepared by independent experts under EIB´s  supervision with the aim of 
proposing a model for energy consumption in Next Generation Networks, and does not in any way represent 
EIB’s official position in regard to these matters. 
Rafael Coomonte Belmonte 
CeDInt Technical University of Madrid 
Index 
2 
1.   Background analysis 
2. Foundations of the model 
3. Model description 
4. Results discussion 
5. Conclusions 
3 
1. Background analysis 
 
• Reducing energy consumption is one of the main goals of Europe. 
• ICT-based opportunities (smart buildings, smart grids and smart 
transportation systems among others) can lead to emission reductions 5 
times the size of the sector’s own footprint. 
• Next Generation Networks (NGN) are considered as the most relevant 
upcoming ICT developments. 
• Major blocks of energy consumption in ICTs: telecommunications 
networks, data centres and consumer equipment. 
• A significant degree of innovation is still required. 
Introduction 
4 
1. Background analysis 
 
• Deriving a simplified model for energy consumption of diverse types of 
fiber-based NGANs. 
• Enable comparisons across technologies. 
• Estimate the impact of the energy consumption in the life-cycle cost of 
NGNs and the implications of new NGAN deployments on the ICT carbon 
footprint.  
• Contribute to a constructive and open discussion on the benefits of 
deploying NGAN from an energy efficiency point of view.  
Objectives 
5 
2. Foundations of the model 
 
• The model for energy consumption in NGANs departs from a review of 
all of the technologies suited for NGANs in the short and middle term 
• Broadband access technologies can be classified by the physical 
medium into two major groups: wired (or fixed line) technologies and 
wireless technologies.  
 
 
 
 
• In the following discussion, only fixed fibre-based NGANs (PON and PtP 
variations of FTTH and FTTx/VDSL) and their energy requirements are 
taken into account. 
Access Technologies 
Access Technologies 
Fixed line 
 
• Fibre 
• Coaxial 
• Copper wire 
• PLC 
Wireless 
• Terrestrial 
 
• Satellite 
6 
2. Foundations of the model 
 
• Different phases of  
energy consumption  
in the life cycle of a NGAN. 
• Wide variety of devices  
that take part in the energy  
consumption of a NGAN.  
Focus on the main active components of the network and the end-
user facilities (CPEs and ONTs). 
• Energy consumption of the customers’ own house equipment is 
defrayed excluded from the economic balance presented below.  
• Calculations using the maximum power allowances stated for each 
technology provided by the standards listed in the regulatory initiatives 
section.  
• The reference price/KWh set for the cost calculations is 0.14 €/KWh. 
Energy assumptions 
7 
2. Foundations of the model 
 
 
• Classification in 10 geographical zones with population density as the 
basic parameter. 
• The nation of Spain  is used as a case study.  
The model described in the paper would  
be applicable without major modifications  
to most European countries. 
Demographic data 
Number of municipalities 8.112
Total population 46.745.807
Population per municipality 5.763
Total surface (km2) 504.677,19
Surface per municipality 62,21
Number of households and businesses 17.950.398
SPAIN
8 
2. Foundations of the model 
 
• Energy consumption highly dependent on the traffic patterns of the 
users.  
• The interfaces 100% duty cycle constantly (24 hours per day). Total 
energy consumed in one year= [power consumption of each device per 
hour] x [power factor of 8760 (24 hours times 365 days a year)]. 
• Demand is also an important factor for a general view of the complete 
Spanish scenario. 
• The study on the energy consumption during the network usage 
presented in this paper defines the behaviour of the network once 
deployed.  
• Take-up ratio of 80%  
• Churn ratio 20% 
•  It would be interesting to study the implications of energy in cost 
balancing during the network deployment phase. 
Traffic and Demand assumptions 
9 
2. Foundations of the model 
 
Network sizing assumptions 
• Energy consumption model would be incomplete if only isolated access 
networks are analysed.  
• As not every municipality make a 100% efficient use of the access area 
even fully deployed, a extrapolation for the complete density zone is 
done in order to take into account these not used parts of the access 
areas that also consume energy. (Not linear deployment) 
• The correction factor is used with the intention of alleviating this effect. 
Affects the energy required by cabinets and OLTs that are not fully 
used. Do not affect customer premises equipment. 
 
In the zones where this number is lower than 1 no correction is needed  
as the full network is exploited, so in those cases the factor used is 1 . 
10 
2. Foundations of the model 
 
• Large repercussions on the costs of network operation. Can represent a 
strong barrier towards the economic viability of NGAN deployments. 
• Energy consumption could become an important criterion taken into 
account in the design process of active devices. 
Economic repercussions 
• European Commission: Code of Conduct on Energy Consumption of 
Broadband Equipment (EC 2008). 
• ETSI: TS 102 533: EE - Energy consumption in BB Telecom Network 
Equipment. 
• Verizon NEBS Compliance: Energy Efficiency Requirements for 
Telecommunications Equipment (Verizon 2009). 
Regulatory initiatives 
11 
3. Model description 
 
 
Different FTTH network architectures, single fibre is used for a subscriber 
in a point-to-point configuration (PtP) or some portion of the fibre is 
shared among customers (point-to-multipoint); here presented as a 
Passive Optical Network (PON).  
Fiber-to-the-home (FTTH) 
Point-to-point network architecture Passive Optical Network architecture 
 
• No passive elements placed in between Local  Exchange and Customer 
Premises. 
• Customers without service do not need to be connected. 
• Total local exchange offices depend on connected users, the network 
penetration and the percentage of subscribed users.  
• The cost per user is constant and the energy consumption is directly related to 
the number of users. 
• Extra factor because of the cooling requirements (αcooling=60% ).  ONT cooling 
factor approaches zero (passive way). 
 
 
• Equations for the energy balance of an access area: 
 
 
12 
3. Model description 
 
Fiber-to-the-home (FTTH) 
PtP architecture  
13 
3. Model description 
 
• After the local exchange, one level of passive optical splitters is used to 
distribute the signal before it reaches the optical network terminal (ONT) placed 
in the customer premises.  
• Splitting process increases the power required for signal transmission. The 
insertion loss depends on the splitting factor n  (17 dB for a 32-fold splitter ). 
• Focus placed in the OLT and ONT stages.  
• The key difference with PtP model is that the homes passed are now considered 
to be subscribed. (resource allocation) 
• The calculations can be made using the next equation: 
Fiber-to-the-home (FTTH) 
PON architecture  
14 
3. Model description 
 
 
• FTTx bring fibre from the CO closer to the subscriber and the final distribution is 
made via an alternative means. FTTB (Fibre To The Building/Basement), FTTC 
(Fibre To The Curb/Cabinet) and FTTN (Fibre To The Node).  
• VDSL/xDSL can be considered equivalent from a network architecture 
perspective. 
• Active devices: OLT and CPE (calculated similarly to the FTTH-PON), VDSL/ONU 
and the DSLAM (Cabinet). 
• Power consumption  
per cabinet is set at 1334 W. 
• Total power demand  
FTTx/VDSL 
FTTx/VDSL access area architecture 
15 
4. Results discussion 
 
• Two main results: to determine which deployments will result into more energy 
efficient solutions and to obtain estimations of the economic costs due to the 
power consumption. 
• Next topics are discussed: the analysis of the relative importance of each energy 
consumer element in the access network, the average premise cost for access 
areas according to the specific network sizing used, the study of the factors 
affecting the total energy and cost calculations for the complete demographic 
framework and the study of the power consumption in the different density 
zones for FTTx/VDSL . 
 
Results introduction 
16 
4. Results discussion 
• FTTH-PtP networks, the share of the 
active element power consumption 
is constant throughout the ten 
zones. 
• FTTH-PON and FTTx/VDSL networks, 
the non-direct relation of the 
energy on the number of users 
connected to the local exchange 
translates into a variation of the 
power share of the active elements. 
• The higher output required by the 
laser diodes in FTTH-PON and 
FTTx/VDSL is a critical fact. Weaken 
the advantage of PON over PtP 
networks, but on the whole power 
consumed EPtP>EPON&FTTx. 
Analysis of the relative importance of each energy consumer element  
Percentage of power consumption for each active element of 
the fibre-based networks vs. the total power consumption in 
the access area (according to the sizing for density zone VI). 
17 
4. Results discussion 
Average premise cost (€) in each access network. 
• PtP networks constant and 
independent of the area, because each 
resource is allocated to the customer 
only when the premise is connected to 
the network. 
• In low density areas the importance of 
OLT and cabinets power consumption 
increases. 
• Importance of the sizing of the 
network. 
Average premise energy cost for each access area  
18 
4. Results discussion 
• Factors affecting cost 
calculations: 
1. Access area average energy 
cost per premise 
2. Sizing of the network 
3. Premises involved in each 
density zone 
4. Number of areas required 
to cover each density zone  
5. Network correction factor  
• For the access areas only the 
two first factors affected the 
power and cost calculations. For 
the density zones the three 
other factors are used and as 
the access area data is used as 
reference for the calculations 
the first two factors affect 
indirectly as well. 
Factors affecting the total energy consumption  
Access area cost per year (€) 
Total cost of each density zone per year (M€) 
 • Power consumption: correction factor applied (both OLT and cabinets) 
• In density zone VII reaches a peak. 
Factors affecting the total energy consumption  
19 
Total power consumption per density zone (MWh) of the FTTx/VDSL architecture  
and participation of each network active element. 
4. Results discussion 
 • To conclude this section, the following table summarizes the results obtained for 
the whole territory of Spain, given all the data and assumptions explained in the 
previous sections. 
Results summary 
20 
Technology FTTH-PtP FTTH-PON FTTx/VDSL 
Total energy consumption for the Spanish territory 
(GWh) 
755 1.352 2.503 
Total cost per year for the entire Spanish territory 
(M€) 
106 189 350 
4. Results discussion 
21 
5. Conclusions and Next Steps 
 
• Importance of the Access layer in the power consumption analysis of NGNs 
Conclusions (I) 
22 
5. Conclusions and Next Steps 
 
 
• Distribution of energy consumption among the active elements of the access 
network is rather dependant on the technology. 
• Energy consumption mainly depends on the architecture and on the sizing of 
the access coverage area, but is also affected by other particularities.  
• Importance of framing the study in a specific scenario.  
• Analysis of the single access area cannot be extrapolated to the general 
deployment of each access networks along the demographic framework 
because it  entails some implications. 
• Energy consumption and deployment investment costs behaves the same way 
when the areas are aggregated. 
• PtP access networks are more expensive to deploy but implies lower overall 
energy consumption than that of PON 
• In low density areas, while VDSL networks have an advantage in economic 
terms (reuse of existing network), consume more energy due to the required 
equipment.  
Conclusions (II) 
23 
5. Conclusions and Next Steps 
 
• DOCSIS and Mobile NGANs energy consumption models development for 
technology comparison in order to obtain further conclusions on the suitability 
of one or other technology for each population scenario. This would add one 
more variable in the comparison among different technologies  for an optimal 
roll-out aside for the simple economic one. 
• Detailed demand assumptions over time to  determine the rolling-out period 
energy consumption and the afterwards usage energy level. 
• Exhaustive traffic assumptions  for energy consumption frame in the different 
equipment and scenarios. 
• Implication of the energy consumption on the OPEX of the NGANs for an 
economic comparison on the level of expense this factor implies. 
Next steps 
24 
Questions and Ideas 
A SIMPLIFIED ENERGY CONSUMPTION MODEL  
FOR FIBRE-BASED  
NEXT GENERATION ACCESS NETWORKS 
 
2nd PhD Seminar of International Telecommunications Society 
21-22 September 2011, Budapest (Hungary) 
Project financed by the European Investment Bank (EIB) 
Disclaimer: This document was prepared by independent experts under EIB´s  supervision with the aim of 
proposing a model for energy consumption in Next Generation Networks, and does not in any way represent 
EIB’s official position in regard to these matters. 
26 
2. Foundations of the model 
 
Network sizing assumptions 
Municipality A 
Part used  Part not used  
Optimal Scenario 
Capacity of the access area: n users 
Municipality 
A 
Municipality 
B 
Due to the distant locations of the different municipalities of the same density zone the 
optimal scenario is not real and therefore an access network has to be deployed alone for a 
single municipality (in many of the cases ), even if the population of the municipality (or the 
remain population not covered by other access network) is lower than the total capacity of 
the access area 
Real scenario 
Municipality 
A 
Municipality 
B 
Municipality 
B 
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