Smart meters with TV gray spaces connectivity: A feasibility study for two reference network topologies

Luca Bedogni*, Andreas Achtzehn^, Marina Petrova^, Petri Mähönen^ * Department of Computer Science and Engineering, University of Bologna, Italy

^ iNETS, RWTH Aachen University, Germany

SECON 2014, 03.07.2014, Singapore

Overview

Introduction

Scenario

Indoor-to-Indoor communication

Indoor-to-Outdoor communication

Conclusion

1. Introduction

Introduction

•  Network services constantly increase

–  The smart grid paradigm needs reliable connections –  Not heavy data rates –  Wired or Wireless –  Wireless in existing bands?

•  Cognitive Wireless Networks

–  Gray Spaces communication

Source: Fadlullah et al., Toward intelligent machine-to-machine communications in smart grid, IEEE Communications Magazine

Gray Spaces Communication

•  TV bands now considered for opportunistic communication –  Commonly referred to as TV White Spaces

•  Gray spaces are occupied channels at the rooftop, possibly free indoors –  Due to shadowing effects

Why Gray Spaces?

•  TVWS hard to find in highly populated areas

Contributions

•  Highlight on two network topologies

•  DTV Spectrum measurements

•  Experimental setup –  Indoor-to-indoor communication on TV bands –  Indoor-to-outdoor communication on TV bands

2. Scenario

Scenario

•  Two network architectures studied

SM1

SM5 SM6 SM7 SM8 SM9

SM2 SM3 SM4

SMCC

SMi

SMk

SMn

SMj

SMh

Indoor-to-Indoor, mesh like

Indoor-to-Outdoor, centralized

Wireless transmissions

PU DTV Signal for PU DTV Receivers

PU DTV Noise for indoor devices

SU Signal is Noise for PU DTV Receivers

Coverage reduction

•  Can Gray spaces negatively impact the primary network?

0

0.2

0.4

0.6

0.8

1

-120 -115 -110 -105 -100 -95 -90 -85 -80

Reduction (m2)/(Maximum Possible coverage (m2))

Prx,sm

Ptx = 80 dBmPtx = 70 dBmPtx = 60 dBm

0

5

10

15

20

25

30

10 20 30 40 50 60 70 80 90 100

SNR

Distance from the transmitter (km)

No interference-100 dBm of interference-90 dBm of interference-80 dBm of interference

SNR threshold for DTV receiver

Nearly 30 km of coverage loss

3. Indoor-to-Indoor

Experimental setup

Parameter Value Tx Power 32 dBm

Central Frequency 472 MHz

Cable Losses 0.5 dB

Tx Antenna Gain 2.5 dBi

Rx Antenna Gain 2.5 dBi

5 10 15 20 25 30 35 40 4560

70

80

90

100

110

120

130

140

150

Distance (m)

Path

loss

Ground Floor (_ = 6.874, ` = 21.15)First Floor (_ = 5.237, ` = 55.32)Second Floor (_ = 3.961, ` = 79.71)

Indoor communication

•  Experimental setup

•  High shadowing, high pathloss •  Floors have a major impact

Reduction due to floors

1 2 3 4 50

5

10

15

20

25

30

35

40

Point number

Diff

eren

ce in

pat

hlos

s [d

B]

Without ordering − same wing

Ground and 1st floorGround and 2nd floor

Indoor communication

•  Experimental setup

•  High shadowing, high pathloss •  Floors have a

major impact

PU protection

•  PU protection is a major key aspect •  A general rule of thumb is hard to be found

–  materials, environments,

•  Adjust SU power not to interfere with PUs

•  On our side: – Directionality of antenna gain of DTV plays

an important role – Shielding can greatly reduce the signal

PU Interference to SU

•  PU signal is treated as noise by SU •  Higher noise means lower SNR •  Measurements in Aachen, Germany

Block Building Height Near buildings clutter height

Türme

WEH 50 meters 0 meters TVK 50 meters 0 meters

Uniklinik Kullen 25 meters 20 meters Kawo2 22 meters 15 meters

Aachen downtown Super C 20 meters 15 meters Economics 15 meters 10 meters

Measurements

WEH TVK

Türme

Power peaks at a low floor

Block Building Height Near buildings clutter height

Türme

WEH 50 meters 0 meters

TVK 50 meters 0 meters

Uniklinik

Measurements

More or less same power at all floors Power increase with the floor height

Kullen Kawo2

Block Building Height Near buildings clutter height

Uniklinik Kullen 25 meters 20 meters

Kawo2 22 meters 15 meters

Measurements Downtown

Power increase with the floor height

Economics Super C

Block Building Height Near buildings clutter height

Aachen downtown Super C 20 meters 15 meters

Economics 15 meters 10 meters

Measurements

•  No general rule of thumb exists – Sometime the peak is at the higher floor – Sometime it is at a lower floor

•  What can we do? –  In-site measurements, costly – Reliable 3d models, may be inaccurate – Cooperative sensing

4. Indoor-to-Outdoor

85

90

95

100

105

110

115120

100

40

Y [m

]

0

20

60

80

0 20 40 60 80 100X [m]

Indoor-Outdoor communication

•  Experimental setup

•  Wall shadowing, high pathloss •  Walls have a major impact

Signal is constrained by buildings

0 20 40 60 80 100100

105

110

115

120

125

130

135

140

145

Distance (m)

Path

loss

Outdoor measurementsPathloss (_ = 1.723, ` = 100.98)

Indoor-Outdoor communication

•  Experimental setup

•  Wall shadowing, high pathloss •  Walls have a major impact

Conclusion

•  Indoor-to-Indoor communication on TV Gray Spaces technically feasible

•  We are skeptical about Indoor-to-Outdoor communication – The PU signal can be higher outdoor – Call for on-site measurements

Future Work

•  Comparison with different technologies – 802.15.4, 802.15.4m

•  More in-depth evaluation of differences in building materials

•  Real testbed to assess the performance

Thank you

Questions?

Smart meters with TV gray spaces connectivity:

A feasibility study for two reference network topologies

Luca Bedogni*, Andreas Achtzehn^, Marina Petrova^, Petri Mähönen^ * Department of Computer Science and Engineering, University of Bologna, Italy – ^ iNETS, RWTH Aachen University, Germany

BACKUP SLIDES

Indoor: 433 and 868 MHz

2 4 6 8 10 12 14 16 18 200

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Distance SMi A SMj

Achi

evab

le th

roug

hput

(Mbp

s)

BPSK on Gray Spaces4−PSK on Gray Spaces8−PSK on Gray Spaces16−PSK on Gray SpacesBPSK on White Spaces4−PSK on White Spaces8−PSK on White Spaces16−PSK on White Spaces

5 10 15 20 250

1

2

3

4

5

6

7

8

Distance SMi A SMj

Achi

evab

le th

roug

hput

(Mbp

s)

BPSK on Gray Spaces4−PSK on Gray Spaces8−PSK on Gray Spaces16−PSK on Gray SpacesBPSK on White Spaces4−PSK on White Spaces8−PSK on White Spaces16−PSK on White Spaces

25 kHz BW 300 kHz BW

BER = 10-6

Indoor: TV bands

5 10 15 20 25 30 35 400

20

40

60

80

100

120

140

160

180

200

220

Distance SMi A SMj

Achi

evab

le th

roug

hput

(Mbp

s)

BPSK on Gray Spaces4−PSK on Gray Spaces8−PSK on Gray Spaces16−PSK on Gray SpacesBPSK on White Spaces4−PSK on White Spaces8−PSK on White Spaces16−PSK on White Spaces

8 MHz BW

BER = 10-6

Outdoor: 433 and 868 MHz

25 kHz BW 300 kHz BW

10 20 30 40 50 60 70 80 90 1000

0.1

0.2

0.3

0.4

0.5

0.6

Distance SMi A SMcc

Achi

evab

le th

roug

hput

(Mbp

s)

BPSK on Gray Spaces4−PSK on Gray Spaces8−PSK on Gray Spaces16−PSK on Gray SpacesBPSK on White Spaces4−PSK on White Spaces8−PSK on White Spaces16−PSK on White Spaces

10 20 30 40 50 60 70 80 90 1000

1

2

3

4

5

6

Distance SMi A SMcc

Achi

evab

le th

roug

hput

(Mbp

s)

BPSK on Gray Spaces4−PSK on Gray Spaces8−PSK on Gray Spaces16−PSK on Gray SpacesBPSK on White Spaces4−PSK on White Spaces8−PSK on White Spaces16−PSK on White Spaces

BER = 10-6

Outdoor: TV bands

8 MHz BW

10 20 30 40 50 60 70 80 90 1000

20

40

60

80

100

120

140

160

180

Distance SMi A SMcc

Achi

evab

le th

roug

hput

(Mbp

s)

BPSK on Gray Spaces4−PSK on Gray Spaces8−PSK on Gray Spaces16−PSK on Gray SpacesBPSK on White Spaces4−PSK on White Spaces8−PSK on White Spaces16−PSK on White Spaces

BER = 10-6