Green Telecom & IT Workshop by IISc and Bell Labs: Green telecom by Rouzbeh

Rouzbeh Razavi

Small Cell Deployments: Impacts on the Energy Efficiency

Traffic growth for communication networks

10-1

100

101

102

103

Tra

ffic

(Tb/

s)

Wireless Voice

P2P

Wireless data

grows fastest

COPYRIGHT © 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.

2010 2015 202010-2

10

YearData from: RHK, McKinsey-JPMorgan, AT&T, MINTS, Arbor, ALU, and Bell Labs Analysis: Linear regression on log(traffic growth rate) versus log(time) with Bayesian learning to compute uncertainity.

Transition to LTE will increase capacity trough more spectrum, better scheduling, and MIMO, but these gains are not sufficient.

Energy consumption of networks will become an increasing problem. “More of the same” will not be good enough.

How can we address these


address these problems?

Historic Capacity Gains in Wireless Networks

Wireless Network Capacity Gains 1950-200015x by using more spectrum (3 GHz vs 150 Mhz)

5x from better voice coding


5x from better voice coding

5x from better MAC and modulation methods

2700x from smaller cells

Total gain 1 million fold

Source: William Webb, Ofcom.

Small Cells - A Necessary Topology Evolution for Future Data Growth


Moving to hierarchical cell structures with small cells can:

• Significantly increase the capacity in the same bandwidth

• Significantly reduce the energy consumption of networks

How can Small Cells improve


improve Energy Efficiency?

Impact of femtocells on the network energy consumption• Telecommunications is a large consumer of energy (e.g. Telecom Italia uses 1% of Italy’s total energy consumption, NTT uses 0.7% of Japan’s total energy consumption)

Opportunity:

Small cells have the potential to reduce the transmit power required for serving a user by a factor in the order of 103 compared to macrocells.


Small cells can provide significant capacity improvement in hotzone areas where traffic demand is high and hence can replace traditional cumbersome macrocells

Due to their reduced coverage, small cells normally serves fewer users and hence enable significant reduction of power consumption if efficient idle modeprocedures are enabled

Source: BBC News - How the world is changing

Methodology & Model

Given the traffic demand map for an area, find out the optimal network topology in terms of the number and the transmit power of macrocell and small cell required

Consider variations of hourly traffic demand to enable investigation of idle mode procedures

System Model:


PNo_Load PTotal

Total

NoLoad

PP

=γSmallcellTotal

MacrocellTotal

P

P=α

60.0,55.0

][7.14

][1350

:

==

=

=

MacroMacro

SmallcellTotal

MacroTotal

WP

WP

ValuesTypical

γγ

Energy Consumption Improvements

5

6

7

8

9

10x 10

4

Tota

l Pow

er [W

]

Macrocells OnlyPIF Macrocells=15%, PIF Smallcells=15%, γm=0.4, γs=0.4

PIF Macrocells=30%, PIF Smallcells=30%, γm=0.2, γs=0.3

PIF Macrocells=50%, PIF Smallcells=50%, γm=0.2, γs=0.05

Observations

Significant power reduction gains as the traffic demand increases (Small Cells can replace macrocells)

Improving the idle mode energy efficiency of small cells (γs) is significantly rewarding

Factor of 45.7 Energy Reduction


2010 2011 2012 2013 2014 2015 20160

1

2

3

4

Year

Tota

l Pow

er [W

]

γs)

Challenge

Maintaining high Quality of Service (QoS) while enabling efficient idle mode procedures for small cells

References: [1] R. Razavi and H. Claussen, “Urban Small Cell Deployments: Impact on the Network Energy Consumption" in Proc. IEEE Wireless Communications and

Networking Conference (WCNC),Paris, France, Apr. 2012.

Reducing energy consumptionIdle mode procedures for Small CellsWhen femtocells become more widely deployed, their energy consumption becomes a concern.

Idle mode procedures can:• Significantly reduce energy consumption

• Reduce power density in the home

• Reduce mobility procedures and associated


• Reduce mobility procedures and associated signalling

• Reduce interference caused by pilot transmissions

References: [1] I. Ashraf, L. T. W. Ho, and H. Claussen, “Improving energy efficiency of femtocell base stations via user activity detection," in Proc. IEEE Wireless Communications

and Networking Conference (WCNC), Sydney, Australia, Apr. 2010.

[2] H. Claussen, I. Ashraf, and L. T. W. Ho, “Dynamic idle mode procedures for femtocells," Bell Labs Technical Journal, to be published in 2010.

Femtocell activation based on noise rise from active UE allows to activate the femto only for serving a call

Challenges and Ongoing Research

Enabling idle mode for small cells requires

- Efficient algorithms to enable sleeping/ awaking

- Modular hardware design that allow independent operation of components

- Hardware design that fulfil the time to reconfigure requirements after awaking

- Self-configuration/Optimisation algorithms that


- Self-configuration/Optimisation algorithms that can swiftly adapt to the environment changes after awaking

Femtocell energy consumption - Today Femtocell energy consumption – Optimized design

What is the future for


future forMacrocells?

lightRadio Cube and Active Antenna Array

lightRadio


lightRadiocube

Active Antenna Array

Digital link

What Do We Mean By lightRadio AAA? Part I: “Invisible infrastructure” co-locating the

RF with the antenna

XXXXXXX

Remote Radio

Conventional Node B site

RF

XXXXXXX

Distributed Node B site

⌧⌧⌧⌧⌧⌧⌧⌧⌧⌧⌧⌧⌧⌧⌧⌧⌧⌧⌧⌧⌧⌧⌧⌧⌧⌧⌧⌧

AAA Node B site

Active Antenna


Radio Head

CPRICPRI

Move RF toantenna

OR Cloud

Integration

Reduces Energy consumption by ~50%

What Do We Mean By lightRadio AAA? Part II: Places a “lightRadio cube” transceiver behind

each antenna element

•Pico Cell

•Macrocell

•Micro Cell (SNAP)RF


•Macrocell upgrade

Innovative Designscan result significant additional reductions of energy consumption

for macrocells

Ethernet or CPRI

Remarks & Conclusions• Wireless data traffic is increasing significantly in the future.

– Energy consumption of networks becomes a major problem.

• Small cells are a necessary topology evolution for future data growth and for reducing energy consumption.

– Compared to an architecture consisting of only macrocells a hybrid deployment results in significant energy reduction gains

– Idle mode procedures in combination with a modular hardware design are essential.


essential.

– Future research focuses on modular hardware and software design of small cells that that can enable efficient idle mode procedures

• Light Radio can improve energy efficiency of base-stations.

– Removing cable losses by integrating RF part and antenna into the “lightRadio Cube” reduces energy consumption by ~50%.

– Individual control of antenna elements enables large scale antenna systems which can significantly reduce the energy consumption for macrocells.


Technology

Green Telecom & IT Workshop by IISc and Bell Labs: Green telecom by Rouzbeh