Effects of joint macrocell and residential picocell deployment on the network energy efficiency

Holger Claussen Bell Laboratories, UK

Problem Overview

 Increasing costs of energy on climate change issues and international focus have resulted in high interest in improving the efficiency telecommunications industry   Telecommunications is a large consumer of energy (e.g. Telecom Italia uses 1% of Italy’s total energy consumption) This results in significant CO2 emissions which  contributes to climate change, and  will result in increased costs due to carbon taxation.

Question: How can we contribute to reducing the energy consumption?

(a) Directly by improving the efficiency networks of cellular (b) Indirectly by reducing the need for travel • Example: rising oil prices in recent years • source: http://seekingalpha.com/article/78326-oil-price-chart-since-1990 All Rights Reserved © Alcatel-Lucent 2008 2 | June 2008

Agenda 1. Direct effects of improving efficiency of cellular networks

 Mixed macro-pico cell topology  Network power consumption with today’s technology  Potential Macrocell improvements  Potential Picocell improvements  Future network power consumption

2. Indirect effects of improving networks

 Teleworking  Teleconferencing to reduce travel

3. Comparison of direct and indirect effects & conclusions

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1

Direct effects of improving efficiency of cellular networks

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Reduce the power required to operate our networks: Mixed macro-pico cell topology

The concept

  Use home-BS deployed by the user to supplement macro-cell coverage Use the users internet connection as backhaul  Allow public access for home-BS  This results in no costs for the cell deployment, the site, electricity, and backhaul for the operator

Objective of this investigation

 Analyse the impact of such a mixed deployment on the total energy consumption and CO 2 emissions of the network All Rights Reserved © Alcatel-Lucent 2008 5 | June 2008

Scenario assumptions

Assumptions for user demand and distribution

     Wellington, NZ + Suburbs (10x10km) Population: 200000 (Wellington 160k, region 420k) Mobile users: 190000 (95% of population) Population NZ = 3.7M, Vodafone: 1.9M, Telecom NZ: 1.6M

Usage: 740 min/user/month = 24 min/user/day = 8 calls/day (3 min) Homes: 65000 assuming 3 persons per home  Demand is based on real measurements , extrapolated to the considered operator market shares of 10%, 20%, 30% and 40%  

Assumptions on emission and energy costs:

 Electricity Emission factor = 0.50063 kg CO 2 Electricity price = 86.3 Euro / MWh / kWh Carbon emission trading value = 21 Euros/tonne CO 2 All Rights Reserved © Alcatel-Lucent 2008 6 | June 2008

Joint macro- and picocell deployment

Home-cell deployment:

   random in homes that have the distribution of the evening traffic cell coverage area: 100x100m up to 8 active users  Power consumption: 15W

Macro-cell deployment:

      Macrocells take care of the remaining users Shared bandwidth: Supported active users per macro cell depends on their requested data rate.

Different numbers of supported active users are considered: 30 (high speed data) to 240 users (voice) per macro-cell This results in a VERY ROUGH approximation of the required number of macro-BS User-distribution: max(dist_business, dist_evening)  users_covered_by_HBS Power consumption: 2500 W for a 3 sector, 1 carrier base station (480 W power amplifier, 2020W base & control).

By deploying picocells, the required number of macrocells is reduced to achieve the same capacity

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100% market share 40% market share 30% market share 20% market share 10% market share 0 0 0.2

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fraction of customers with picocells 0.8

1 A small fraction of randomly deployed home base stations can achieve a significant user coverage!

70 60 40% market share 30% market share 20% market share 10% market share 50 40 30 20 10 0 0 0.2

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1 fraction of customers with HBS With increasing home base station coverage, fewer macrocells are required to provide full user coverage All Rights Reserved © Alcatel-Lucent 2008 7 | June 2008

Energy consumption and CO

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deployment scenarios – Today emission of different

Challenge:

 Macrocell coverage becomes less energy efficient compared to picocell coverage with increasing demand for high data rate services 3500 3000 Network energy consumption for operator with 40% market share (Today)

Approach:

 A mixed deployment of macrocells for area coverage and picocells for the main demand reduces the total network energy consumption and CO 2 emission significantly.

2500 2000 1500 Picocell contribution increases linearly

Model Results – Wellington NZ:

   Maximum expected CO effects (assuming 30 users/macrocell) would be up to approximately 2 reduction from direct 2250 tons CO 2 /year for covering the full population in Wellington Total carbon reduction value: 47250 Euros/year (for full population coverage) The total saved energy costs: (for full population coverage) 377000 Euros/year 1000 500 30 users/macrocell 60 users/macrocell 120 users/macrocell 240 users/macrocell picocell contribution 0 0 0.2

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fraction of customers with picocells 100% of energy costs paid by operator 0.8

1 97% of energy costs paid by end user

The highest energy savings can be achieved when a small fraction of the customers have picocells deployed

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Macrocell improvements: Power Amplifier Efficiency improvements over time and their drivers

Source: Georg Fischer, Bell Labs Nuernberg 9 | June 2008 All Rights Reserved © Alcatel-Lucent 2008

Macrocell Improvements: Efficiency improvements by change in architecture

Current architecture: PA, ~60% of Power lost in Heat Connector Cable, 0.5dB Loss (10%!) Ground - Tower Cable.

Up to 2.5dB losses (40% of the power!) 8-Element Antenna 1dB Loss in divider network (20% loss) Digital RF-Signal Gen (Radio) PA Diplexer Tower-Top-architectures: PA, (MUCH smaller) Antenna (single Element) Digital Ground - Tower RF-Signal Gen (Radio) RF-Signal Gen (Radio) Diplexer Diplexer NO Cable Losses!

RF-Signal Gen (Radio) Diplexer

By Changing the architecture, min. 50% of the required RF-Power can be saved!

But: more power in parallel radios etc. required…

Source: Florian Pivit, Bell Labs Ireland 10 | June 2008 All Rights Reserved © Alcatel-Lucent 2008

Picocell improvements

Introduction of idle mode procedures

 In urban areas public picocell deployments can quickly result in high over provisioning of capacity (20% of customers with picocells can serve up to 80% of the total demand) Switch off picocells temporarily already provided in areas by other picovells where sufficient capacity is

Other possible areas for improvements

 more efficient processing  Power saving states when only partially loaded • not considered here 11 | June 2008 All Rights Reserved © Alcatel-Lucent 2008

Energy consumption and CO

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emission of different deployment scenarios – Future improved Technology

Assumptions:

 Macrocell efficiency is improved by 33% improved PAs and architectural improvements.

 by Picocells dynamically switch off when the area in which they are deployed already provides sufficient coverage and capacity.

Results:

 The improved efficiency results in a significant further reduction of the total energy consumption , energy costs , and CO 2 emissions .

  Reductions of up to 70% compared to a macrocell network with today’s technology are feasible, for high data rate demand in urban areas (30 user/macrocell). The benefits of a mixed macro- and picocell topology will increase further as both technologies mature.

2500 Network energy consumption for operator with 40% market share (Future improved Technologies) 2000 Higher macrocell efficiency 30 users/macrocell 60 users/macrocell 120 users/macrocell 240 users/macrocell picocell contribution 1500 1000 Higher picocell efficiency 500 Picocell contribution does not increase linearly anymore 0 0 0.2

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fraction of customers with picocells 100% of energy costs paid by operator 0.8

1 85% of energy costs paid by end user

When picocells dynamically switch off based on demand, more than the optimum number of picocells can be deployed without significantly increasing the energy consumption

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2

Indirect effects of improving communication systems:

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Teleworking



Teleconferencing to reduce travel

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Effects of teleworking

based on study by BT Laboratories

      A reduction of approximately 6MWh in Energy usage can be achieved by telework per person compared to full time office work The main savings result from reduced travel. The energy for heat and light is similar in all cases The reduction results in a value of 33.6 Euros under the carbon emission trading scheme per year The average travel cost reduction per year is far greater at 698£ = 938 Euros (assuming car travel with 7.1 l/100km and 0.169 kg CO 2 /km, and price of unleaded petrol 103.9 pence per litre) At a national level , the effect of of CO 2 , 1.4% of UK total CO 2 5 million people emissions . working at home would save about 8 million tonnes 14 | June 2008 All Rights Reserved © Alcatel-Lucent 2008

Teleworking

Example: Wellington + Suburbs      Approximately 65% (130000) of the population are working. Assumption: New communication technologies would enable an increase of 10% (13000) of the working population to work from home. For Wellington this would result in a CO 2 reduction of up to 20800 tons of CO 2 This would correspond to a carbon reduction value of 43680 Euros per year.

per year . The total travel cost reduction would be 12.2 x 10 6 Euros per year 15 | June 2008 All Rights Reserved © Alcatel-Lucent 2008

Reduced travel due to Teleconferencing

Example: Wellington International Airport         Wellington Airport (http://www.wellington airport.co.nz/html/business/statistics.php) 110000 flights per year, approximately 95% are domestic, and 5% international 55% of flights (60500) are business related Assumption: A typical domestic flight distance is 800km and emits 11.61 kg CO 2 /km resulting in a total of 9.288 tons CO 2 emission. Total emission of 57475 flights = 533828 tons CO 2 Assumption: A typical international flight distance is 8000km and emits 23.39 kg CO 2 /km resulting in 187 tons. Total emission of 3025 flights = 565675 tons CO 2 Per 1% reduction of business flights in Wellington would result in a reduction of 10950 tons of CO 2 per year.

This would correspond to a carbon reduction value of 231000 Euros per year.

In addition the corresponding reduction in travel costs would be roughly 87 x 10 6 Euros (assuming: domestic flight = 150 Euros, International flight = 700 Euros) All Rights Reserved © Alcatel-Lucent 2008 16 | June 2008

3

Comparison of Direct and Indirect effects & Conclusions

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Comparison of direct and indirect effects of improved networks

Results:

Potential CO2 reduction for Wellington per year  Improving the efficiency can directly reduce emissions both of network equipment OPEX and CO 2  Indirect CO 2 and cost reduction as a result of improved networks can be far greater that the direct effects .

 Examples of indirect effects resulting from improved networks are:   increase in teleworking replacement of business trips by teleconferencing 25000 20000 15000 10000 5000

Opportunity:

 Teleworking CO 2 and emissions teleconferencing enormous potential to reduce both costs and if the user experience is improved. Possible solutions are: have an  improve technology to provide the required higher data rates to homes and offices  reduce the data rates required for high quality video conferencing (e.g. by improving compression).

70000000 60000000 50000000 40000000 30000000 20000000 10000000 0 0 Efficient hardware & Network architecture Efficient hardware & Network architecture

Direct effects

10% of population Teleworking 10% of population Teleworking 1% business flight reduction through teleconferencing 100000000 Potential cost reduction and carbon value for Wellington per year 90000000 80000000 1% business flight reduction through teleconferencing

Indirect effects

tonnes CO2 cost reduction carbon value All Rights Reserved © Alcatel-Lucent 2008 18 | June 2008

Conclusions

Direct effects: Architecture improvements

 A mixed macro- and picocell architecture can significantly reduce the energy consumption of cellular networks in urban areas where macrocells are capacity limited  Effect expected to increase in the future when both technologies mature  Attractive for operators since energy for picocells is paid for by the user

Indirect effects: Teleworking and reducing travel

 Improving telecommunication systems can reduce energy consumption indirectly improving teleworking and video conferencing by  Reducing travel has a very high impact on the energy consumption and emissions  Indirect effects have a much higher impact as direct effects.

Reducing the environmental impact can be achieved best by a combination of (a) Improving the efficiency of eetworks (b) Improving communication systems to promote teleworking and reduce travel

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