Wireless and energy efficient buildings · Frequency selective surface A Reconfigurable approach...

The University of Sheffield

Communications Research Group

Wireless and energy efficient

buildings

Richard Langley

University of Sheffield, UK



WiFEEB Project 286333

Funded by EU FP7 £2M

http://eeepro.shef.ac.uk/wifeeb/

Wireless Friendly Energy

Efficient Buildings

2



WIRELESS SYSTEMS

• e-Health

• Smart Meters

• Mobile telephone

• WiFi

• TV distribution



Contents

• Propagation issues

• Modelling – iBuildnet, CST, FEKO

• Energy performance - insulation

• Smart walls for coverage reconfiguration

• Security – Mobile phones in prisons

• Conclusion

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Energy performance

Insulation

– foil backed foam (Kingspan) – reflecting signals

– green walls – absorbing signals

Energy calculations and optimisation carried out using Energyplus

software - Standard for Civil Engineering Industry.

Conflicts with wireless propagation optimisation?

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Integration of EnergyPlus for the design of energy

efficient buildings

• EnergyPlus is a whole building energy simulation program that engineers,

architects, and researchers use to model energy and water use in buildings.

Modelling the performance of a building with EnergyPlus enables building

professionals to optimize the building design to use less energy and water.



Architecture have introduced Green Wall Systems (GWS) in the project.

GWS are vertical vegetation with integrated modular units and are

commonly used in the building industry on building facades as well as other

building indoor spaces.

• Measurements of grass and ivy green wall samples were carried out

• Samples were initially saturated with water and gradually allowed to dry

Selected Green Wall System



Green wall -Ivy

-60

-50

-40

-30

-20

-10

0

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

Tra

nsm

issi

on

(d

B)

Frequency (GHz)

Day 0

Day 1

Day 8



Wireless Signal issues

• Frequency – 169, 433, 700 - 2500, 5200 MHz?

• Building materials and construction

• Propagation – frequency/building construction - how

far will signal propagate?

• Interference – co-channel/adjacent channel - choice

of modulation/protocol/technology

• Data rates – network, capacity

• Robustness – congestion and interference

• Reliability

• Human occupants?

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SIGNAL PROPAGATION

Dependent on frequency, materials,

construction, occupants, etc.

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Signal Propagation

• Stud walls – good signal transmission

• Brick walls/ concrete – poor transmission,

high loss

• Glass – dependent on type and coatings

• Metal clad insulation?

• Human occupants absorb signals

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Building 3

Test site 3 – Late-Victorian terraced

house (built approx. 1890).

Brick construction with brick and

lathe/plaster internal walls). S

Slate roof.

PVC double glazing.

Two inhabited floors plus stone-

walled, uninhabited basement

Fully furnished

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Building 3 Trial 1

• Trial 1 ‘Receiver in the Kitchen’, located on

Ground Floor (typical location)

• Meter location?

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Building 3 Trial 1

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Received Power Topology (Measured)

• This figure illustrates the results of trial in

various locations in the front room.

• The two regions shown in black correspond

to areas where data could not be taken.

• The highest RSSI values can be seen in an

area closest to the kitchen and near to the

door adjoining the two rooms.



Choice of frequency

(m)

(m)

-4 -3.5 -3 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5-3.6

-3.1

-2.6

-2.1

-1.6

-1.1

-0.6

-0.1

0.4

0.9

1.4

1.9

2.4

2.9

3.4

-36

-33

-30

-27

-24

-21

-18

-15

-12

-9

-6

-3

0

3

6

(m)

(m)

-4 -3.5 -3 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5-3.6

-3.1

-2.6

-2.1

-1.6

-1.1

-0.6

-0.1

0.4

0.9

1.4

1.9

2.4

2.9

3.4

-36

-33

-30

-27

-24

-21

-18

-15

-12

-9

-6

-3

0

3

6

(m)

(m)

-4 -3.5 -3 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5-3.6

-3.1

-2.6

-2.1

-1.6

-1.1

-0.6

-0.1

0.4

0.9

1.4

1.9

2.4

2.9

3.4

-36

-33

-30

-27

-24

-21

-18

-15

-12

-9

-6

-3

0

3

6

(m)

(m)

-4 -3.5 -3 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5-3.6

-3.1

-2.6

-2.1

-1.6

-1.1

-0.6

-0.1

0.4

0.9

1.4

1.9

2.4

2.9

3.4

-36

-33

-30

-27

-24

-21

-18

-15

-12

-9

-6

-3

0

3

6

(a) (b)

(c) (d)

5.8GHz 2.4GHz

433MHz866MHz



Add External Wall Insulation 2.45GHz

No insulation

Insulation

External walls only

Ground floor First floor



Effect of floor insulation 2.45 GHz (measured)

0 1 2 3 4 5m

0 1 2 3 4 5m

NO INSULATION INSULATION



PROPAGATION ENHANCEMENT

STRATEGIES

Metal Shielding

Frequency Selective Surfaces (FSS)

Smart walls

MIMO



Smart Environments

Moving users

Control propagation

Reduce interference

Shape cells

Isolate rooms/buildings

Intelligent Walls

Active Frequency Selective Walls

Antenna Unit Walls



Reconfiguring Conference Centre



Controlling coverage (a) 16 intelligent walls either isolate or provide connection between rooms

(b - d ) show different settings of intelligent walls and therefore different

cell shapes.

Red walls are in an isolation state, green ones provide connection.

The colours of covered areas correspond to the colours of the Access Points.



Active multiband – Option FSS wall

Intelligent Walls with Active FSS

Potential problems with• Design

• Installation

• Multiband

• Price

• Attenuation only 20 dB at best



Active frequency selective surfaces

© The University of Sheffield

– Double layer switchable AFSSs with interwoven spiral unit cells

• Separate switching layer

– Singly polarised AFSS – Isotropic/dual polarised AFSS

• For dual pol

arised operat

ion additiona

l switches or

layer



Solution Using Intelligent Wall Unit (IWU)

Intelligent Walls with IWU• Metalized insulation foam

• Simple IWU

Advantages• Quite easy to design

• Much cheaper than FSS

• Can do multiband easily



IWU can consist of• Receiving antenna

• Filter ( => band)

• Amplifier

• Transmitting antenna



Secure Electromagnetic Buildings



Motivation

• Not all environments (buildings etc) wish to have communication signals enter

or leave the building (E.g. prisons, hospitals, military buildings etc)

• Some signals would be wanted at all times (E.g. emergency services)

• How do we stop some communications signals but allow others through?

• FARADAY CAGE IS VERY DIFFICULT

• Many researchers have investigated the use of FSS for this application as they

act as a large area filter

• Problem: In order to stop a signal the FSS may have to attenuate >60dB. This

is impractical. Mobile phones operate down to -120dBm.

• We have investigated how we might STOP a GSM mobile phone signal using a

time varying FSS approach



Frequency selective surfaces

Frequency selective surfaceA Reconfigurable approach

The FSS above has varactor diodes to change the amplitude and phase response of the Transmission coefficient

A GSM signal is based on a GMSK modulation scheme, hence, the information is transmitted using phase information at a bit rate of 277bits/s

Question : Can we change the FSS response, rapidly, between one or more phase states to impair the GSM signal?



Measured Performance

The results show similar trends to the simulations with a maximum BER of 35%.

The range of switching frequencies which will offer significant BER (>15%) is

approximately between 1kHz and 600kHz.

The large variation is switching frequency and transmission phase demonstrates that the

concept is very robust for secure applications.

BER %Switching

Frequency

kHz

Phase



INTERFERENCE



Smart Meter Scenario

A UK residential area combined with Detached, Semi-Detached and Terraced

houses.

Each house installed one Zigbee Coordinator @2.4GHz in the meter box.

Some WiFi APs randomly located in different houses, and work at 2.4 GHz.

Interference may be introduced due to frequency collision.

Semi-Detached Houses

Terraced Houses

Detached HousesWiFi AP

ZC



-40dBm

-110dBm


The EIRP of ZCs is 18 dBm.

The whole residential area is covered with good

signal strength.




Interference will be a concern if the channels are not well planned.

WiFi APs can introduce additional interference to the Zigbeenetworks which operate at 2.4 GHz

All ZCs are operating on the same channel

50dB

6dB

The channels of ZCs are well optimised.Interference introduced by WiFi APs.

Signal/interference

level



Conclusion

Frequency needs careful consideration

Access points and Meter placement problem

Each dwelling/office will have different

propagation conditions

Intelligent reconfiguration possible

Securing a building is very difficult

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Wireless and energy efficient buildings · Frequency selective surface A Reconfigurable approach...

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