Green Wireless Communication - IEEEewh.ieee.org/r10/calcutta/comsoc/lecture_ETCOMS13.pdf · A....

02 February, 2013Jadavpur, Kolkata

Aniruddha Chandra

Electronics & Communication Engineering Department, National Institute of Technology, Durgapur.

[email protected]

Green Wireless Communication Green Wireless Communication

2/26A. Chandra - Green wireless communication

ETCOMS 2013

Green Communication =

Energy Efficient Communication

A new timely idea


ETCOMS 2013OutlineOutline

Energy Efficiency – Why?

Energy Efficiency – How?

Case Study





Case Study


ETCOMS 2013Energy EfficiencyEnergy Efficiency

Why?

Traditional perspective:

- Reduced Tx power → reduced reliability.

- To maintain QoS, Tx rate should be reduced.

Ecological perspective:

- Reduce greenhouse gas emission.

Economical perspective:

- Reduce OPEX cost.



Traditional Perspective

Value BW most:

- Ever increasing subscriber base.

- Strict spectrum regulations.

- R&D focus on BW efficient radio access techniques.

- These complex techniques demand more processing power.

A typical MIMO-OFDM Tx Rx ckt



Traditional Perspective

What about energy?

- Battery powered mobile terminals → limited energy.

- Limited energy → limited reliable data rate.

BER vs. SNR curves (M = 16) BW efficiency vs. power efficiency



Ecological Perspective

2007 statistics on environmental impact:

- A cellular network ~ Energy for 1,70,000 homes.

- 3% of the energy consumption.

- 2% of CO2 emission.

- The figures are going to triple by 2020.

Objects in Mirror are Close than

they Appear



Sources of Greenhouse Gas Emission

Operation of radio access network:

- RF transmission.

- Fossil fuel powered BS.

- Charging of devices.

Device/ equipment production.

Backbone network operation.

A. Fehske et al. “The global footprint of mobile communications: the ecological and economic perspective,” IEEE Commun. Magz., 49 (8), 55-62, 2011.



Economical Perspective

Decreasing revenue:

- Vodafone annual ARPU decreased from € 30 (2000) to € 16 (2009).

Increasing fuel cost:

- Diesel cost has doubled since 2008.


ETCOMS 2013

Energy Consumption

Cost components:

Energy components:

- Feeder network.

- RF conversion.

- Climate control (e.g., air conditioning).

Energy EfficiencyEnergy Efficiency

Energy components for BS



Energy Cost Calculation

Revenue generated:

- No. of subscribers per cell site ~ 800.

- ARPU ~ 3$ / month.

- Monthly revenue ~ 800 x 3$ = 2400 $.

Cost for energy:

- Energy cost ~ 0.20 $/ kWh.

- Power requirement per BS ~ 1.7 kW.

- Cost per month ~ 30 (days) x 24 (hours) x 1.7 x 0.20 $ = 244 $.

10% of total revenue (even before tax, interest, depreciation)!

BSSubscriber

Subscriber

Cell site

Power plant





Case Study


ETCOMS 2013

Energy Savings in Base Stations

Improvements in PA:

- Linear PAs → 90% wastage.

- DPD, Doherty, GaN based PA.

Power saving mode:

- Sleep mode, discontinuous Tx/ Rx.

Optimization:

- BS placement, cell size.

Energy Efficient MethodsEnergy Efficient Methods

V. Mancuso et al. “Reducing costs and pollution in cellular networks,” IEEE Commun. Magz., 49 (8), 55-62, 2011.

Z. Hasan et al. “Green cellular networks: a survey, some research issues and challenges,”IEEE Commun. Surveys Tuts., 13 (4), 524-40, 2011.


ETCOMS 2013

Energy Savings in Base Stations

Renewable energy:

- Sustainable bio-fuel.

- Solar energy.

- Wind energy.

New BS architecture:

- Short, low power RF cable between Amp. & Ant.

- Feeder less site.

Reduce no. of BS?C. Lubritto et al. “Energy and environmental aspects of mobile communication systems,”Energy, 36 (2), 1109-14, 2011.

Solar powered BS (Italy)



ETCOMS 2013

New Communication Strategies

MIMO / beamforming:

- Diversity.

- More sectors per cell site.

Cognitive radio:

- Find unused spectrum, BW traded off for power.

Use a third node:

- Reduce effective transmission distance.






Case Study


ETCOMS 2013

Save Energy by Introducing Relays

Basic idea:

- Transmit power,

- Realized over two hops,

Consider circuit energy:

- Energy consumed by Tx and Rx circuit at source, destination, and relay.

Overall energy saving:

- Depends on relay placement.

Case StudyCase Study

nT

nT CdPdP =⇒∝

212211 ;, dddCdPCdP nT

nT +===

( ) TTTnnn PPPdddd ≤+⇒+≤+ 212121


ETCOMS 2013Relay PlacementRelay Placement

Collinear Model

Relay DestinationSource

Direct Path(Reference level)

Relayed Path

42.2 m (Optimum location)



Non-linear Model



Non-linear Model

Floor plan of 1st floor of ECE department, National Institute of Technology

My Cabin!



Non-linear Model

Energy saving contours superimposed on Floor plan

B. Ghosh et al. “Placing the ‘third’ node: An energy efficiency perspective,” Proc. IEEE CODEC, Kolkata, Dec. 2012.


ETCOMS 2013

Open Problems

Relay - To use or not to use:

- Always cooperate, or use relay only when the direct link fails?

Relay selection:

- If there are many relay nodes, how many and which ones to select?

Other issues:

- Multiple antennas at relay, distributed STC etc.

Relay PlacementRelay Placement


ETCOMS 2013SummarySummary

Value energy.

Various means to reduce energy consumption.

Use of wireless relays is one of them.

A single collinear relay may save upto 40% energy.

For non-linear setup, an energy efficient region may be found to place the relay.

Many open problems, we need you!


ETCOMS 2013Read More About ItRead More About It

Green Communication1. G. Y. Li et al., “Energy efficient wireless communications: Tutorial, survey,

and open issues,” IEEE Wireless Commun. Magz., 18 (6), 28-35, 2011.

Modelling Energy Consumption

1. S. Cui et al., “Energy-efficiency of MIMO and cooperative MIMO techniques in sensor networks,” IEEE JSAC, 22 (6), 1089-98, 2004.

2. G. G. de Oliveira Brante et al., “Energy efficiency analysis of some cooperative and non-cooperative transmission schemes in wireless sensor networks,” IEEE TCOM, 59 (10), 2671-77, 2011.


ETCOMS 2013

Thank You!

[email protected]

Green Wireless Communication - IEEEewh.ieee.org/r10/calcutta/comsoc/lecture_ETCOMS13.pdf · A....

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