This presentation is based on the the article: "A Comprehensive Survey on Networking over TV White Spaces"

1. TV White Space Networking: Characteristics,
Challenges, and Opportunities
Mahbubur Rahman
Department of Computer Science
Wayne State University, Detroit, MI

2. TV White Spaces
• Refer to allocated but locally unused TV channels
• Between 54 MHz and 698 MHz in the US
• TV channel index: 2 - 51
• VHF (54-216 MHz) and lower UHF (470-698 MHz)
• Federal Communication Commission (FCC) in the US
• Allowed unlicensed use in 2008
• But not to interfere primary users
• In other countries
• UK by Office of Communication (Ofcom)
• Canada by Industry Canada Consultation
• South Africa by Communication Authority
• Singapore, Kenya, Namibia, Argentina, etc.
2
Occupied
White spaces
Frequency (MHz)
Signal Strength (dBm)

3. TV White Space: FCC Regulations
• Operational Regulations
• Licensed Operation
• Unlicensed Operation
• Hybrid Operation
• FCC allows unlicensed operations
• Unlicensed device category
• Fixed
• Personal/portable
3

4. TV White Space: FCC Regulations
• Fixed Device
• Generally placed in outdoor fixed locations
• Can use higher transmission power
• Sends automatic periodic messages
• Personal/portable Device
• Can be mobile and change locations
• Usually uses lower transmission power
• Two operational modes
• Mode I (dependent) and Mode II (independent)
4
Fixed device
Personal/portable device

5. TV White Space: FCC Regulations
• Access Regulations
• Tells how to determine unoccupied and occupied TV channels
• 3 Methods
• Geo-location Database Approach
• Control Signal Approach
• Spectrum Sensing/listening Approach
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Internet
Location
Available channels
White Space Database

6. TV White Space: FCC Regulations
Attributes Fixed Device
Personal/portable Device
Mode I (Client Mode) Mode II (Independent)
Database Access ✓ X ✓
Spectrum Sensing X X X
Sensing Threshold -84 dBm -114 dBm -114 dBm
Tx Power 1 Watt (30 dBm) 100 mWatt (20 dBm) 100 mWatt (20 dBm)
Antenna Height <30 Meters N/A N/A
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7. TV White Space: Opportunities
• TV white space can enable several applications
• Low cost and complexity
• Sensing & Monitoring Applications
• Urban sensing, Environmental/habitat monitoring, Oil filed monitoring , etc.
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A Sensing & Monitoring network (source: Green Orb)

8. TV White Space: Opportunities
• Agricultural IoT Applications
• Needs data-driven decisions
• Temperature, humidity, water level, etc.
• Microsoft, Climate Corp., AT&T, Monsanto are taking initiatives
8
Smart Agriculture (Source: AgfunderNews)

9. TV White Space: Opportunities
• Smart and Connected Community Applications
• Promise to address the needs of the past, present, and future
• Wireless broadband access, public safety, etc.
• Microsoft, Google are already adopting white spaces.
9Wireless Broadband Access (Source: ArsTechnica)

10. TV White Space: Opportunities
• Real-time Applications
• TV white space has potential to support large-
scale real-time CPS (Cyber-physical systems)
applications
• Industrial process control
• Data center power management
• Civil infrastructure control, etc.
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Industrial process control (oil tank monitoring)
Controller
Valve

11. TV White Space: Opportunities
• Smart Utility Network (SUN) Applications
• Promises efficient management of electricity, natural gas, water, and sewage.
• Advanced Metering Infrastructure (AMI)
11
Smart Water Management (source: Alliance of Water Utility)

12. TV White Space: Characteristics
• Traditional Wireless Network Technologies
• IEEE 802.15.4, Wi-Fi, Bluetooth
• Traditional Networks: short range à multi-hop topology
• Complex protocols, energy and latency overhead
12
IEEE 802.15.4 based mesh network topology

13. TV White Space: Characteristics
• TV white spaces have longer communication range
• 𝒅𝒊𝒔𝒕𝒂𝒏𝒄𝒆 ∝ 𝟏
𝒇𝒓𝒆𝒒𝒖𝒆𝒏𝒄𝒚1 [from Friss’ Equation]
13Single hop network architecture
Received power
Transmit power
Transmitter gain
Receiver gain Speed of light
distance
frequency

14. TV White Space: Characteristics
• TV white spaces can penetrate obstacles
• Lower frequency à longer wavelength
• TV frequency: wavelength between 43-59 cm
• Can easily penetrate building walls and trees
14Single hop network architecture

15. TV White Space: Characteristics
• Spectrum Availability
• Large in number compared to 2.4 GHz and 5 GHz bands
• 2.4 – 2.5 GHz (2.4 GHz band) , 5.725-5.875 GHz (5 GHz band)
• 47 TV channels (54-698 MHz)
15
White space availability at different
number of counties (in US) based
on data from Spectrum Bridge
database

16. TV White Space: Characteristics
• Higher bitrate
• A single TV channel can provide up to 21 Mbps [Bahl et al., SIGCOMM ‘09]
• Operating on N channels can boost the bitrate N-times
• IEEE 802.15.4 maximum allowable bitrate is 250 kbps
• Some applications demand higher bitrate
• E.g., Volcano Monitoring require high bitrate
• Sampling period: 100 kHz
• Each sample: 24 bits resolution
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17. TV White Space: Standardization Efforts
17
Work Group Focus Agenda
IEEE 802.22 Wireless Regional Network (WRAN)
Cognitive Medium Access Control (MAC) layer and
Physical layer (PHY)
IEEE 802.11af Wireless Local Area Network (WLAN) MAC layer and PHY layer
IEEE 802.15.4m
Low-Rate Wireless Personal Area
Network (LR-PAN)
MAC layer and PHY layer
IEEE 802.19.1 Wireless Coexistence Group Coexistence methods in white space
IEEE 1900.4a,
1900.4.1
Heterogeneous Mobile Wireless
Networks
Enable distributed heterogeneous wireless mobile
services
IEEE 1900.7
Radio Interface for Dynamic TVWS
Access
Develop radio interface with MAC and PHY layer

18. TV White Space: Protocols
• Industries are already adopting TV white spaces
• Wireless Broadband Access (both Microsoft and Google in Africa)
• Agricultural IoT (Microsoft FarmBeats project)
• Research community is also developing protocols
• Protocols for white space network
• TV white space detection protocols
• Networking protocols
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19. TV White Space: Detection Protocols
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Protocols
TVWS
Access
Location Mobility Security Applications
KNOWS
[Yuan et al., DySPAN ‘07]
Sensing +
Database
Indoor/
Outdoor
✓ X
Indoor/outdoor TVWS
detection
SenseLess
[Murty et al., TMC ’12]
Database Outdoor ✓ X Outdoor TVWS detection
WISER
[Ying et al., MobiCom
‘13]
Sensing +
Database
Indoor ✓ X Indoor TVWS detection
WINET
[Zhang et al., INFOCOM
’15]
Sensing +
Database
Indoor ✓ X Indoor TVWS detection

20. TV White Space: Networking Protocols
20
Protocols
TVWS
Access
Location Mobility Security Applications
CR-S
[Ahuja et al., DySPAN
‘08]
Sensing +
Database
Indoor/
Outdoor
✓ ✓ Sensing & Monitoring, IoT
WhiteFI
[Bhal et al., SIGCOMM
‘09]
Sensing +
Database
Indoor/
Outdoor
✓ X Wireless broadband access
WhiteNet
[Feng et al., DySPAN ‘11]
Sensing +
Database
Indoor/
Outdoor
✓ X Wireless broadband access
SNOW
[Rahman et al., SenSys
’16,17]
Database
Indoor/
Outdoor
X X Sensing & Monitoring, IoT

21. TV White Space: Challenges & Directions
• New challenges for wireless sensor networks (WSNs)
• WSNs are mainly for data collection (many-to-one communication)
• White spaces: multi-hop à single hop à more conflict at BS (base station)
• Long range à more hidden terminals à more collisions at BS
• WSNs need scalability and energy efficiency
21
A
B
C
D
E
F
• While A transmits, B, C, and D cannot
transmit and have to back-off.
• E, F can be hidden terminals and thus
will collide if transmit at the same time
• Need efficient medium access layer
(MAC) and physical layer (PHY)
solutions
Conflict and collision in single hop WSN

22. TV White Space: Challenges & Directions
• What we have done for wireless sensor networks (WSNs)
• SNOW [Rahman et al., SenSys ‘16,17]
• D-OFDM (Distributed Orthogonal Frequency Division Multiplexing) based
physical layer that enables parallel Tx/Rx
• Hidden terminal aware CSMA/CA (Carrier Sense Multiple Access/Collision
Avoidance) medium access control layer
• Scalable and energy efficient
Internet
Location
Available channels
f1 f2 f3 fnf4 …
…
White Space
Database
Nodes
BS
22
SNOW architecture

23. TV White Space: Challenges & Directions
• New challenges for wireless sensor networks (WSNs)
• Coexistence of homogeneous WSNs
• Spectrum sharing between WSNs
• Handling interference between WSNs
23
Possible coexistence scenario in
homogeneous (SNOW) networks

24. TV White Space: Challenges & Directions
• What we have done for coexistence isssue
• SOP [Rahman et al., IoTDI ‘18]
• Trade-off between scalability and interference
• Enables concurrent inter-SNOW and intra-SNOW communications
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Possible coexistence scenario in
homogeneous (SNOW) networks

25. TV White Space: Open Challenges & Directions
• Many other challenges that need to addressed in general
• Interference between primary and secondary users
• Longer communication range à more interference to primary users
(Specially, if operating near a restricted area)
• Reduce Transmission (Tx) power à Reduce communication range à reduced
throughput
• Trade-off between Tx power and Quality of service (QoS)
25

26. TV White Space: Open Challenges & Directions
• Fragmentation of TV white spaces
• Presents discontinuity in spectrum
• Existing networking protocols may not be able to use fragmented spectrum
• Need to be very careful about incumbents in between
• Need new physical layer and medium access layer solutions (like SNOW?)
26
Data on fragmented spectrum (source: WhiteFi [Bhal et al., SIGCOMM ’09])

27. TV White Space: Open Challenges & Directions
• Temporal and Spatial variations
• Need to operate on different TV white spaces at different times and places
• Will hurt seamless operation
• Critical to real-time applications
• Need cognitive radio solutions
27
Temporal and spatial variations of TV white spaces (source: WISER [Ying et al., MobiCom ‘13]

28. TV White Space: Open Challenges & Directions
• Scarcity and future adaptation
• White space availability differs in urban, suburban, and rural areas.
• Who knows about FCC’s plan?
• Make the protocols compatible for other frequency bands
• Antenna design
• Lower frequency à larger antenna
• Antenna size à at least one-tenth of wavelength for efficient reception
• Better Quality of service (QoS)à Multiple antennas
• Antennas need to be apart by half of wavelength
• Reduce antenna form factor
28

29. TV White Space: Open Challenges & Directions
• Variable Bandwidth
• How to enable many-to-one communication with variable bandwidth support?
• No protocols exist.
• Mobility
• FCC rules: need to check white spaces every 100m move
• Vehicle-to-vehicle communication
• How to look for TV white spaces?
• How to address Doppler effect?
• Security
• Longer range à higher security vulnerability
• Sniffing, spoofing, man-in-the-middle attacks may not be viable for short range protocols
• Possible isolation of nodes in long communication range
• Do the existing security protocols suffice?
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30. Conclusion
• We’ve looked into TV white spaces
• Device types
• Regulations
• Opportunities of TV white spaces
• Can enable various low-power wide-area networking applications
• Have benefiting characteristics (long range, availability, high bitrate)
• TV white space protocols
• Standardization efforts
• Detection and networking protocols
• Challenges and directions
• Scalability
• Coexistence and interference
• Fragmentation, temporal variation, and spatial variation
• Variable bandwidth
• Mobility
• Security.
30

31. 31
References
• Saifullah, A., Rahman, M., Ismail, D., Lu, C., Chandra, R. and Liu, J., 2016, November. SNOW:
Sensor network over white spaces. In Proceedings of the 14th ACM Conference on Embedded
Network Sensor Systems CD-ROM (pp. 272-285). ACM.
• Saifullah, A., Rahman, M., Ismail, D., Lu, C., Liu, J. and Chandra, R., 2017, November. Enabling
reliable, asynchronous, and bidirectional communication in sensor networks over white spaces. In
Proceedings of the 15th ACM Conference on Embedded Network Sensor Systems. ACM.
• Rahman, M. and Saifullah, A., 2018, April. Integrating Low-Power Wide-Area Networks in White
Spaces. In Internet-of-Things Design and Implementation (IoTDI), 2018 IEEE/ACM Third
International Conference on (pp. 255-260). IEEE.
• Saifullah, A., Rahman, M., Ismail, D., Lu, C., Liu, J. and Chandra, R., 2018. Low-Power Wide-Area
Network Over White Spaces. IEEE/ACM Transactions on Networking, 26(4), pp.1893-1906.
• Rahman, M. and Saifullah, A., 2018. A Comprehensive Survey on Networking over TV White
Spaces. arXiv preprint arXiv:1810.07120.