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WINLAB Backhauling in TV White Space Narayan B. Mandayam ( joint work with Cyrus Gerami, Larry Greenstein, Ivan Seskar ) WINLAB, Rutgers University IEEE.

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Presentation on theme: "WINLAB Backhauling in TV White Space Narayan B. Mandayam ( joint work with Cyrus Gerami, Larry Greenstein, Ivan Seskar ) WINLAB, Rutgers University IEEE."— Presentation transcript:

1 WINLAB Backhauling in TV White Space Narayan B. Mandayam ( joint work with Cyrus Gerami, Larry Greenstein, Ivan Seskar ) WINLAB, Rutgers University IEEE Distinguished Lecture 1

2 WINLAB What is White Space? TV Band Devices: Fixed or Portable Max. Fixed antenna height = 30m, Portable < 3m Permissible channels (6MHz each) Transmit Restrictions Protected region around primary TV transmitters Sense and avoid protected devices TX power: Fixed:30 dBm (6dBi antenna gain) = 4W EIRP, Co- and Adjacent-channel not allowed Portable: 20 dBm (no antenna gain) = 100mW, Co-channel not allowed, Adjacent = 16 dBm 2 X Additional Ruling on Sep

3 WINLAB What is Really White Space? Economist Markets, Property Regulator/Politician Social Good Engineer New Technology, Cognitive Radios Folks who are out there Free speech, Bill of Rights Communication/Information Theorist W 3 ¢ $ $, votes priceless

4 WINLAB How much TV White Space is there in NJ? TV Towers around NY City and Philadelphia Lots of white space spectrum available in NJ! 4 # of channels (fixed) vs. # of 5 X 5 sq. mi. grids 7 – 31 channels available per cell (42 – 186 MHz)

5 WINLAB Radio Coverage 5 Prime spectrum with a wide range of applications ~ MHz available depending on TV transmitter density Power constraints result in achievable bit-rate profile for fixed- fixed, fixed-mobile, and mobile-mobile ~5 2Km range for LOS fixed-mobile ~3-5x WiFi range for non-LOS services, e.g. ~50 250m

6 WINLAB White Space Networks 6 Range of possible usage scenarios, with sweet spot in outdoor networks with medium range and speed Bit-Rate 100 m

7 WINLAB Sample Applications: Cellular Data Boost 7 Cellular data boost network can be used to offload fast-growing cellular traffic using dual-mode radio Mesh network of outdoor white space hot spots; backhaul data to existing BTS Intended for transport of non-real time data such as mail, content, facebook … Potential for ~2-5x capacity boost depending on % coverage & service mix

8 WINLAB Sample Applications: Distribution/Backhaul 8 D ISTRIBUTION AND B ACKHAUL USING W HITE S PACE

9 WINLAB Sample Applications: Long range V2V/Emergency Network 9 Long-range V2V useful for traffic control/warnings, geographic apps, p2p content, etc. Supplements short-range p/DSRC V2V links (from mandated car radios?) can be used to form a high capacity emergency backup network using ad hoc mesh between cars and fixed APs Application requirements well matched with WS range/bit-rate properties

10 WINLAB 10 GENIE NODE Central spectrum manager Service Provision Device Provides end-user service Relay and Wireless Access Devices Provides relay/connectivity support Sample Applications: Cognitive Digital Home

11 WINLAB Design Implications for White Space Networks 11 White space radio systems require the following building blocks: Flexible BW PHY, preferably operating in non-contiguous spectrum Spectrum sensing for TV primary and other incumbents, coordination with data base Opportunistic link layer access with distributed congestion control procedures for fair sharing among secondary users Discovery and bootstrap protocols for ad hoc network formation Common coordination channels and/or spectrum servers for improved coordination among multiple types of secondary users, e.g. Databases … and of course, cognitive SDR platforms (wideband, flexible, low-cost)

12 WINLAB WS Building Blocks: NC OFDMA PHY NC OFDMA approach used to opportunistically fill spectrum Allows for flexible spectrum sharing for secondary coexistence Center freq White Space Primary freq Min. tones needed for freq. synchronization

13 Case for Noncontiguous OFDMA - I A B C X Three available channels Node A transmits to node C via node B. Node B relays node As data and transmits its own data to node C. Node X, an external and uncontrollable interferer, transmits in channel 2. 2 If we use max-min rate objective and allocate channels, node B requires two channels; node A requires one channel Scheduling options for Node A and Node B?

14 Case for Noncontiguous OFDMA - II 14 2 A C 3 B Transmission in link BC suffers interference in channel #1: Contiguous OFDM X 2 A C B Spectrum fragmentation limited by number of radio front ends #2: Multiple RF front ends X 14 2 A C B #3: Non-Contiguous OFDM (NC-OFDMA) Nulled Subcarrier X NC-OFDM accesses multiple fragmented spectrum chunks with single radio front end

15 15 2 A AP B Non-Contiguous OFDM Nulled Subcarrier Serial to Parallel IFFT Parallel to Serial D/A X X[1] X[3] X[1] X[3] 0 x[1] x[2] x[3] X[2] = NC-OFDM accesses multiple fragmented spectrum chunks with single radio front end Node B places zero in channel 2 and avoids interference Node A, far from the interferer node X, uses channel 2. Both nodes use better channels. Node B spans three channels, instead of two. Sampling rate increases. Modulation NC-OFDM Operation

16 Resource Allocation in NC-OFDMA Benefits: Avoids interference, incumbent users Uses better channels Each front end can use multiple fragmented spectrum chunks 16 Challenges: Increases sampling rate Increases ADC & DAC power Increases amplifier power Increases peak-to-average-power-ratio (PAPR) Develop centralized, distributed and hybrid algorithms for carrier and forwarder selection, power control

17 WINLAB WS Building Blocks: NC OFDMA MAC NC OFDMA offers the possibility of a simple FDMA MAC instead of CSMA or TDMA (..CSMA may still be used for end- user access) Simplifies ad hoc network operation and avoid classical mesh self interference and exposed node problems Requires a cooperative access policy (i.e. not greedy, and with some form of congestion backpressure) LINK 1 freq LINK 2 LINK 3 rate r1 rate r2 rate r3 Rates r1, r2, r3 periodically adjusted via cooperative procedures f1 f2 f3

18 WINLAB Architectures for Secondary Coexistence WS Mobile Access Protocol WS AP w/ backhaul Secondary System A Secondary System B freq Secondary A Spectrum Secondary B Spectrum Secondary co-existence an important requirement for WS Various schemes possible depending on system model Completely autonomous, using performance feedback only Common coordination channel Common Internet based spectrum server Common Coordination Channel (optional) Internet Spectrum Server (optional) Control information


20 O UTLINE The Proposed System First order Methodology Achievable Capacity Traffic Demand How many cells would need fiber? Aggregating Flows Conclusion and Future Directions White Space: Where are we? Where do we go? WINLAB 20

21 H OW WILL IT LOOK ? WINLAB NJ as case study Proximity to NY & Philly Highest population density WINLAB in NJ! Cells of 5 mi X 5 mi total 307 Antenna (base-station) in each FCCs max allowed height=30 m FCCs max TX power=4 W Based on fixed devices rules of FCC 21

22 WINLAB W HAT WILL IT DO ? Internet user Wifi Fiber 4 sector antennas Antenna coverage Wireless Distribution and Backhaul Use of Sector antennas for more concentrated transmission

23 WINLAB C AN W HITE S PACES BE USED ? A CHIEVABLE C APACITY D EMAND ( PER CELL ) ( PER CELL )>< Use Radio Use Fiber Resources used: FIRST ORDER CRITERION FCC rules Propagation models NJ pop statistics Census 2000 Internet usage statistics Internet traffic survey 23

24 A VAILABLE B ANDWIDTH WINLAB NJ TOWERS AT A GLANCE Towers in NJ, NY, DE & PA Coverage can be 100km (r) 24


26 C HANNEL AVAILABILITY INCLUDING ADJACENT CHANNEL EFFECT 26 WINLAB A VAILABLE SPACE PER CHANNEL A VAILABLE B ANDWIDTH TV tower coverage Additional separation ring Available for possible use Available as White Spaces 25

27 A VAILABLE B ANDWIDTH 27 WINLAB 25 B ANDWIDTH D ATABASE X Repeat this for each cell and you get bandwidth database Each channel is 6 MHz 7 – 31 channels available per cell (42 – 186 MHz) No islands Similar channels available in neighboring cells INTERFERENCE!

28 WINLAB F REQUENCY REUSE PLANNING SNR at cell-2 = 19 dB SNR at cell-4 = 5 dB – Interference 14 dB isolation for r=2 Median path loss: ITU terrain model for LOS Obstruction height:15m for sparse population and 30m for dense population 1% outage with 8 dB shadowing variance A VAILABLE B ANDWIDTH 28 reuse factor (r) of 2 :


30 WINLAB L ET S CONSIDER ONE CELL 54 MHz (9 channels) available 27 MHz usable (reuse) Spectral Efficiency: 6.23 bps/Hz (path loss and population and building heights) Max Achievable Capacity: ~ 168 Mbps ~ 75.7 GB/hour 30

31 WINLAB A CHIEVABLE C APACITY D EMAND>< U SAGE PER H OUSEHOLD S IMULTANEOUS A CTIVE U SERS (α) α = 10% α = 30% α = 50% Pop/sq mi pop/cell 3 people per household 74.2% have internet internet clients/cell 18MB/hr (Cisco Survey) 90 MB/hr (5 times more) 126 MB/hr (7 times more) 180 MB/hr (10 times more) 31 US Census 2000 Our Approximation

32 WINLAB L ET S CONSIDER ONE CELL Cell pop: 8750 Cell households: 2917 Cell internet connections: 2164 Cell traffic using α = 30% : 18 MB/hr/link: 11.7 GB/hr 90 MB/hr/link: 58.4 GB/hr 126 MB/hr/link: 81.8 GB/hr 180 MB/hr/link: GB/hr 32

33 WINLAB L ET S CONSIDER ONE CELL A CHIEVABLE C APACITY D EMAND>< α = 30% & 18 MB/hr/link : 75.7 > 11.7 α = 30% & 90 MB/hr/link : 75.7 > 58.4 α = 30% & 126 MB/hr/link : 75.7 < 81.8 α = 30% & 180 MB/hr/link : 75.7 <

34 WINLAB H OW MANY CELLS NEED FIBER ? ( OUT OF 307) 18 MB/hr90MB/hr126 MB/hr 180 MB/hr Cells requiring fiber connection 34

35 WINLAB A GGREGATING M ULTIPLE F LOWS 35 FIBER Proposed Solution: Use Excess Capacity for aggregation Excess Capacity = Achievable Capacity - Demand Clustering Plant more fiber at cluster heads Plant cluster heads in high capacity cells to route traffic through Detailed routing study CLUSTER CLUSTER HEAD

36 WINLAB E XAMPLE OF AGGREGATION Group cells into clusters (illustrated in figure) Have 1 fiber connected cell in each cluster If in each cluster: Excess Capacity > Total Demand X (2 or 3) Then: 1 fiber per cluster is sufficient! Else: Add 1 fiber to cluster After calculations for α = 30% & 126 MB/h: W ORST CASE REQUIRES 10 MORE FIBER CELLS 36

37 WINLAB C ONCLUSIONS AND FUTURE WORK Feasibility study of a distribution plan in NJ – First order study promising in spite of conservative assumptions on traffic and propagation – system more cost effective than a fiber layout – Most effective in rural areas (where its needed) No prior high speed internet connectivity No fiber infrastructure More bandwidth available and better propagation Same methodology for other states/regions Further issues that need to be studied: Detailed routing strategies Cost/benefit analysis 37

38 WINLAB W HITE S PACE : W HERE ARE WE TODAY ? Database Testing and Trials – Google, Microsoft, Spectrum Bridge, Telcordia, etc. – No TVBDs and services rolled out yet! Wireless Service Providers and TV Broadcasters still continue to resist Service providers want more licensed spectrum Broadcasters worry about interference FCC working on next round of spectrum auctions Reverse Auctions, Repackaging and Incentive Auctions 38

39 WINLAB W HITE S PACE : W HERE WILL WE GO ? Green trumps White? 39


41 WINLAB PILOT PROJECT: BROADBAND TO BIVALVE Set up WiFi Hotspots in Bivalve, NJ Backhaul to Bridgeton, NJ where Internet (T1) connectivity exists Use Fixed Towers and available TV White Space to provide backhaul as shown in exemplary figure – Could reuse water towers or weather towers as feasible for installing radios – Towers requires power supply The set-up will also serve as a research testbed for protocol and application development to benefit rural areas If an ISP partner is available, mobile hotspot service could be provided along the way to farms, etc. 41

42 WINLAB PILOT PROJECT: BROADBAND TO BIVALVE Hardware: Radio Router Node based on currently available second generation ORBIT platform – Multiple radio interfaces: (wifi), (wimax), LTE, ZigBee, Bluetooth, CRKit (whitespace capable) Software: Whitespace Routing Protocol optimized for throughput – Local (hotspot) support – Caching capabilities 42

43 References C. Gerami, N. B. Mandayam, and L. J. Greenstein, Backhauling in TV white spaces, Proceedings of IEEE GLOBECOM 2010, December 2010 O. Ileri and N. B. Mandayam. Dynamic spectrum access models: Toward an engineering perspective in the spectrum debate. IEEE Communications Magazine, 46(1): , January D. Zhang, R. Shinkuma, N. B. Mandayam, Bandwidth Exchange: An Energy Conserving Incentive Mechanism for Cooperation in IEEE Transactions on Wireless Communications, vol. 9, No. 6, pp , June 2010 D. Zhang and N. B. Mandayam, Bandwidth Exchange for Fair Secondary Coexistence in TV White Space, in Proceedings of International ICST Conference on Game Theory for Networks (GameNets), Shanghai, April 2011 M. N. Islam, N. B. Mandayam, and S. Kompella. Optimal resource allocation in a bandwidth exchange enabled relay network. In Proc. IEEE MILCOM2011, pages 242–247, November 2011 C. Raman, R. Yates, N. B. Mandayam, Scheduling Variable Rate Links via a Spectrum Server in Proceedings of IEEE DySpan 2005, November 2005, Baltimore, MD D. Raychaudhuri, N. B. Mandayam, J. B. Evans, B. J. Ewy, S. Seshan, and P. Steenkiste. Cognet: an architectural foundation for experimental cognitive radio networks within the future internet. In Proc. ACM MobiArch 2006 N. Krishnan, R. D. Yates, N. B. Mandayam, J. S. Panchal, Bandwidth Sharing for Relaying in Cellular Systems in IEEE Transactions on Wireless Communications, vol. 11, No. 1, pp , January

44 Acknowledgments 44 U.S. National Science Foundation Office of Naval Research IEEE COMSOC Debi Siering WINLAB Collaborators: Cyrus Gerami, Larry Greenstein, Nazmul Islam, Ivan Seskar, Dipankar Raychaudhuri

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