IMT Lucca, 25/11/2009 MAM Energy Efficient Wireless Internet Access Marco Ajmone Marsan, Michela Meo Politecnico di Torino
Jun 19, 2015
IMT Lucca, 25/11/2009 MAM
Energy Efficient Wireless Internet Access
Marco Ajmone Marsan, Michela Meo
Politecnico di Torino
IMT Lucca, 25/11/2009 MAM
WIA & MtCO2e
Marco Ajmone Marsan, Michela Meo
Politecnico di Torino
IMT Lucca, 25/11/2009 MAM
What’s all this “green networking” about?
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• Energy is becoming the issue of our futureWe depend on energy which is becoming scarce
Energy consumption is causing dramatic climate changes
• We must cope with this and reduce energy consumption in all sectors,
ICT and networking included
The problem
IMT Lucca, 25/11/2009 MAM
Climate change
Source: Hansen, J., et al. (2006) "Global temperature change". Proc. Natl. Acad. Sci. 103: 14288-14293.
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2003 Model2009 Model
Climate change
Source: A.P. Sokolov et al, “Probabilistic Forecast for 21st Century Climate Based on Uncertainties in Emissions (without Policy) and Climate Parameters”, Report 169, Jan 2009
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• The main global warming culprit is carbon dioxide, CO2
• Gases that react to form smog
• Fine particles such as black carbon
• 80% of the increase of CO2 in the air in the last century is due to fossil fuel burning (20% deforestation)
Who is the culprit?
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Source: Energy Information Administration (EIA), International Energy – Annual Energy Outlook 2009
TW
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• Electricity = 30% of energy
• 1 W of electrical energy ≈ 2.1 W of primary energy
Source: Energy Information Administration (EIA), International Energy – Annual Energy Outlook 2009
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• Information and Communication Technologies play a positive role for energy saving:– moving bits instead of atoms
• teleworking and telecommuting• e-commerce• intelligent transport systems• electronic billing
– sensors to monitor and manage environment
What about ICT?
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The ICT sector is a heavy consumer!
… but
“ICT alone is responsible of a percentage which vary from 2% to 10% of the world power consumption.”
“Electricity demand of ICT is almost 11% of the overall final electricity consumption in Germany.”
“The ICT sector produces some 2 to 3% of total emissions of greenhouse gases.”
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Source: M. Pickavet et al, “Worldwide Energy Needs for ICT: the Rise of Power-Aware Networking,” in IEEE ANTS Conference, Bombay, India, Dec. 2008.
Which ICT?
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Consumption might double in the next decade
Source: M. Pickavet et al, “Worldwide Energy Needs for ICT: the Rise of Power-Aware Networking,” in IEEE ANTS Conference, Bombay, India, Dec. 2008.
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• Life Cycle Assessment (LCA) refers to the quantitative characterization of the environmental impacts of products and services and includes– Manufacture– Operation – Disposal
• A life cycle perspective can lead to a better understanding of environmental management
This is particularly true for IT products
Life cycle matters
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• Example: 2-gram memory chip requires – at least 1,200 grams of fossil fuels – 72 grams of chemicals
• Fossil fuels for production are some 600 times the weight of the chip (the total fossil fuel to produce a car is 1-2 times its weight)
• Purification to semiconductor grade materials is energy intensive
• Due to its extremely low-entropy, organized structure, the materials intensity of a microchip is orders of magnitude higher than that of “traditional” goods.
Electronics
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-2000
0
2000
4000
6000
8000
10000
12000
14000
16000
Desktop Laptop CRT LCD
To
tal
En
erg
y (M
J)
Production
Distribution
Use
End of life
Source: Peter James and Lisa Hopkinson, “Energy and Environmental Impacts of Personal Computing -- A Best Practice Review prepared for the Joint Information Services Committee (JISC)”, May 2009.
PCs
Williams, E., 2004. Energy Intensity of Computer Manufacturing: Hybrid Assessment Combining Process and Economic Input-Output Methods. Environ. Sci. Technol., 2004, 38, 6166-6174.
Lawrence Berkeley National Laboratory, 2005. Optimization of Product Life Cycles to reduce Greenhouse Gases in California. Report for California Energy Commission. CEC-500-2005-110-F.
IVF Industrial Research and Development Corporation, 2007. Lot 3: Personal Computers (desktops and laptops) and Computer Monitors. Final Report for the European Commission, August 2007.
IMT Lucca, 25/11/2009 MAM
Equipment Consumption
Desktop PC 100-150W
Laptop PC 20W
Server 700 W – 10KW
Router 5-10 W per Gbps
GSM BS 700W
UMTS BS 800W
WIMAX BS 400W
Operation
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Data centers
Source: “Report to Congress on Server and Data Center Energy Efficiency” Public Law 109-431. U.S. Environmental Protection Agency ENERGY STAR Program , August 2007
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• In 2006, U.S. data centers used 61 TWh of electricity, corresponding to 1.5% of national consumption
• Double the amount consumed in 2000
• Based on current trends, energy consumption will continue to grow 12% per year, due to increasing demand for the services they provide
Data centers
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• Algorithms to free up servers and put them into sleep mode or to manage load on the servers in a more energy-efficient way
• Sensors identify which servers would be best to shut down, based on environmental conditions
• Use more efficient components• Reduce cooling needs (cooling consumes as
much as 40% of the operating costs) through specific physical layouts
Current solutions
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Data centers
Source: “Fact Sheet on National Data Center Energy Efficiency Information Program“, U.S. Department of Energy (DOE) and U.S. Environmental Protection Agency (EPA), March 19, 2008
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Internet
Core
Backbone
Metro
FeederNetworks
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Typical network
Source: J. Baliga, K. Hinton and R. Tucker, “Energy consumption of the Internet”, in COIN - ACOFT 2007, June 2007, Melbourme, Australia
factor 4factor 4
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Source: R. Tucker et al., “Energy consumption in IP networks”, in European Conference on Optical Communication ECOC’2008, Brussels, Sept. 2008.
Routers
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Fixed operators
70% of power consumption70% of power consumption
30% of power consumption30% of power consumption
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Mobile operators
10% of power consumption10% of power consumption
90% of power consumption90% of power consumption
Order of the OPEX!
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Which business model?
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Fast Slow
Intermediate
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Cellular networks• Base stations are responsible for about 80% of
energy consumed by a cellular network• A typical BS consumes from 500W to 3KW, with an
average consumption per year of 35 MWh (as much as 10 families)
• In Italy 60,000 BSs, leading to 2.1 TWh/year, about 0.7 % of total Italian consumption of electricity
• 300 M€ electricity bill for the operators
• About 1,2 Mton of emitted CO2 equivalent per year
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Base station consumption
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An immediate solution for mobile operators
Start by reducing consumption at the
access network with current technologies
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Dynamic network planning
• Networks are planned based on the peak hour traffic
• Due to natural traffic variability (i.e., typical day/night traffic profile) the network results over-dimensioned during long periods of time
Switch off portions of the network
when traffic is low
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Traffic profiles
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• Assume that a fraction x of the base stations (cells) are switched off
• The BSs that remain on are in charge of ― the traffic of the cells that are off (the
desired QoS must still be guaranteed)― the radio coverage (transmission power
might be increased to guarantee coverage)
Switch-off scheme
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A NodeB controls 2 microcells
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Switch off Switch off halfhalf of the NodeB, x=1/2 of the NodeB, x=1/2
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Switch off Switch off halfhalf of the NodeB, x=1/2 of the NodeB, x=1/2
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8:00 16:00 24:00 8:00 16:00 24:00 8:000
0.01
0.02
0.03
0.04
0.05
0.06
0.07
time
lam
bda
day/night traffic patternfor one cell
Low traffic threshold: QoS is guaranteed
Total traffic in x+1 cells
night zone
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8:00 16:00 24:00 8:00 16:00 24:00 8:000
0.01
0.02
0.03
0.04
0.05
0.06
0.07
time
lam
bda
night zone
traffic pattern for cells
remaining on
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3.Check the maximum cell radius, RMAX
If R’< RMAX DONE
else • increase transmission power during night
zone OR• reduce the night zone
Looking for a switch-off scheme
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8:00 16:00 24:00 8:00 16:00 24:00 8:000
0.01
0.02
0.03
0.04
0.05
0.06
0.07
Time
lam
bda
VOICEVIDEOCALLDATA
Switch off 1 Node-B for about 9 hours
Energy saving= 37.5%
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7 μCells with:R_μcells=100mPTX_μcells=2 W
Umbrella (Macro) Cell:R_Mcell≈265mPTX_Mcell=3.4 W
Hierarchical scenario
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8:00 16:00 24:00 8:00 16:00 24:00 8:000
0.01
0.02
0.03
0.04
0.05
0.06
Time
lam
bd
a
VOICE
VIDEOCALL
DATA
λnight→0: Good for
office scenario
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8:00 16:00 24:00 8:00 16:00 24:00 8:0010
-20
10-15
10-10
10-5
100
Time
Blo
ckin
g P
rob
abi
lity
VOICE
VIDEOCALL
DATA
8:00 16:00 24:00 8:00 16:00 24:00 8:0010
-4
10-3
10-2
10-1
Time
La
mb
da
µ M Mµ µ
-The Umbrella cell is always ON (day+night)- Switch off 2 Node-B (7µcells) for about 4 hours
Energy saving= 17%
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Possible configurations
Manhattan configurations (linear)
(1,2)
(2,3)
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Possible configurations
Hexagonal configurations (squared)
(3,4)
(8,9)
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Switch off schemegeometry
(1,2)linear
(2,3) linear
(3,4) squared
(8,9) squared
Load ratio 2 3 4 9
Cell radius 2x 3x 2x 3x
PB[W] 5 18 5 18
Night zone 16h30m 14h40m 12h20m 7h
NodeB saving [%] 68.7 61.1 50.4 29.1
Network saving 34.3 40.7 37.8 25.9
Switching off more does not always mean saving more!
IMT Lucca, 25/11/2009 MAM
But, we have multiple operators
• Several competing mobile operators cover the same area with their equipment
• Networks are dimensioned over the peak hour traffic
• During low traffic periods the resources of one operator are sufficient to carry all the traffic
Make operators cooperate to reduce energy consumption
IMT Lucca, 25/11/2009 MAM
• In turn,– Switch off the network of one operator, when
traffic is low and the active operators can carry all the traffic
– Let users roam to other operators– Balance costs
Cooperation
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• Two operators: A and B– No. of users NA and NB, with NB = NA and <1– Daily traffic profile fA (t) and fB (t), fB(t)= fA(t)
Example: 2 operators
fM
T/2 T=24h t
fA(t)
fB(t) fM
IMT Lucca, 25/11/2009 MAM
fM
T/2 T=24h t
fM/(1+)
fM/(1+)
Switch off time for B
Switch off A
MMBA f)f()f( f)(f)(f BBBB
MMBA f)f()f( f)(f)(f AAAA
B A
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• Let pA and pB be the frequency with which A and B switch off
• Different strategies can be adopted for choosing the switching frequency
Switch-off policies
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• Switch off the networks every other day, alternatively,
pA = pB
Balanced switch-off frequency
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• Make the two networks carry the same roaming traffic (on average)
Balanced roaming cost
B
B
A
A
T
BB
T
AA dttfpdttfp
2/2/
)()(
traffic carried by B when A is off
traffic carried by A when B is off
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• Make the two networks achieve the same energy saving
Balanced energy saving
)2()2( BBBAAA TCpTCp
switch off time for A
energy costfor A
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• Two cost models– Constant: the fixed costs dominate, the
networks have the same energy cost regardless the number of subscribers
CB=CA
– Variable: the network energy cost is proportional to the number of subscribers
CB = CA
Balanced energy saving
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Real traffic pattern
0
0.2
0.4
0.6
0.8
1
1.2
9:00 12:00 15:00 18:00 21:00 0:00 3:00 6:00 9:00
Tra
ffic
, f_
A(t
)
Time, t [h]
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Constant cost model:Total saving
0
5
10
15
20
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10
10
20
30
40
En
erg
y sa
vin
g [
cost
/day
]
En
erg
y sa
vin
g [
%]
Traffic ratio,
RoamingSaving
SwitchingMax
Saving can be huge!
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Constant cost model:Roaming balance
0
5
10
15
20
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10
10
20
30
40
En
erg
y sa
vin
g [
cost
/day
]
En
erg
y sa
vin
g [
%]
Traffic ratio,
TotalAB
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Constant cost model:Switching balance
0
5
10
15
20
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10
10
20
30
40
En
erg
y sa
vin
g [
cost
/day
]
En
erg
y sa
vin
g [
%]
Traffic ratio,
TotalAB
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Variable cost model:Total saving
0
5
10
15
20
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
En
erg
y sa
vin
g [
cost
/day
]
Traffic ratio,
RoamingSaving
SwitchingMax
Different cost models lead to different
policies
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Variable cost model:Total saving
5
10
15
20
25
30
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
En
erg
y sa
vin
g [
%]
Traffic ratio,
RoamingSaving
SwitchingMax
Different cost models lead to different
policies
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Different QoS
• When operators guarantee different QoS levels, the network with the best QoS switches off only when the other operator can guarantee similar QoS
• This translates into a traffic reduction factor
MM f)f()(1 f)f()(1 AA
Same QoS Different QoS: QoS of A is tighter
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2 Operators: Different QoS
0.4 0.5 0.6 0.7 0.8 0.9 1 0
5
10
15
20
25
0.1 0.2 0.3
Sav
ing
[%
]
QoS traffic reduction factor,
=0.25=0.50=0.75=1.00
IMT Lucca, 25/11/2009 MAM
2 Operators: Different QoS
20
21
22
23
24
0.2 0.4 0.6 0.8 1
Sw
itch
ing
tim
e
QoS traffic reduction factor,
On-Off
=0.25=0.50=0.75=1.00
6
7
8
0.2 0.4 0.6 0.8QoS traffic reduction factor,
Off-On
=0.25=0.50=0.75=1.00
1
IMT Lucca, 25/11/2009 MAM
Multiple Operators
• With more than 2 operators, the space of possible switch-off patterns explodes
• Different roaming schemes are possible, during the switch-off phase:– Roaming-to-One: Roaming traffic goes to the
operator which remains on all the time– Roaming-to-All: Roaming traffic is distributed to
active operators
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Example: 4 Operators
• Let the number of users for operator i be proportional to i, with
a is the network unbalance– a=0: the networks carry the same traffic– a=1: network 1 has ¼ of the traffic of network 4
4
iaa)(1i
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4 Operators: Increasing Pattern
20
25
30
35
40
0 0.2 0.4 0.6 0.8 1
Sav
ing
[%
]
Network unbalance, a
same cost - Allvar cost - All
same cost - Onevar cost - One
Under same cost, increasing pattern
is optimal
Roaming to all is more effective
IMT Lucca, 25/11/2009 MAM
4 Operators: Decreasing Pattern
20
25
30
35
40
0 0.2 0.4 0.6 0.8 1
Sav
ing
[%
]
Network unbalance, a
same cost - Allvar cost - All
same cost - Onevar cost - One
IMT Lucca, 25/11/2009 MAM
4 Operators: Increasing Pattern
7
8
9
10
11
12
13
14
15
0 0.2 0.4 0.6 0.8 1
Off
tim
e
Network unbalance, a
oper. 1 - Alloper. 2 - Alloper. 3 - All
oper. 1 - Oneoper. 2 - Oneoper. 3 - One
IMT Lucca, 25/11/2009 MAM
• Energy issues are crucial, even for networking– Design criteria must be changed – Energy consumption/wastage is a variable to
be taken into account in design and performance evaluation
– Future Internet design will have to cope with it– Virtual operators appear to be an interesting
option
Lessons
IMT Lucca, 25/11/2009 MAM
• A new attitude is needed– Consumers: awareness of the cost of
• Turn over of devices • Uncontrolled use of energy
– Manifacturers• Life cycle assessment
– Operators• Careful management of resources • Architectures
Lessons
IMT Lucca, 25/11/2009 MAM
• Governments and institutions will have to play a role in – Inducing new attitudes (e.g., education to an
aware use of resources)– Forcing new production models based on
products life cycle (e.g., responsibility for disposal, incentives to long lasting devices)
– Providing incentives for cooperation
Lessons
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• M.Ajmone Marsan, L.Chiaraviglio, D.Ciullo, M.Meo, “Energy-Aware UMTS Access Networks”, W-GREEN 2008 - First International Workshop on Green Wireless, Lapland, Finland, September 2008
• M.Ajmone Marsan, L.Chiaraviglio. D. Ciullo, M.Meo, “Optimal Energy Savings in Cellular Access Networks”, GreenComm'09 - First International Workshop on Green Communications, Dresden, Germany, June 2009
• M.Ajmone Marsan, L.Chiaraviglio, D.Ciullo, M.Meo, “Energy-Efficient Management of UMTS Access Networks”, 21st International Teletraffic Congress (ITC 21), Paris, France, September 2009
• M. Ajmone Marsan, M. Meo, ”Energy Efficient Management of two Cellular Access Networks”, GreenMetrics 2009 Workshop, Seattle, WA, USA, June 2009
References
IMT Lucca, 25/11/2009 MAM
Thank you!
IMT Lucca, 25/11/2009 MAM
Questions?