1 / 44

Backhauling in TV White Space

Backhauling in TV White Space. Narayan B. Mandayam ( joint work with Cyrus Gerami, Larry Greenstein, Ivan Seskar ) WINLAB, Rutgers University IEEE Distinguished Lecture. What is White Space?. TV Band Devices: Fixed or Portable Max. Fixed antenna height = 30m, Portable < 3m

kin
Download Presentation

Backhauling in TV White Space

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

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

  2. 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 Additional Ruling on Sep 23 2010 X

  3. 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 ≈ $ ≈ $, votes ≈ ¢ priceless

  4. How much TV White Space is there in NJ? • TV Towers around NY City and Philadelphia • Lots of white space spectrum available in NJ! # of channels (fixed) vs. # of 5X5 sq. mi. grids • 7 – 31 channels available per cell (42 – 186 MHz)

  5. Radio Coverage • Prime spectrum with a wide range of applications • ~50-200 MHz available depending on TV transmitter density • Power constraints result in achievable bit-rate profile for fixed-fixed, fixed-mobile, and mobile-mobile • ~5 Mbps @ 2Km range for LOS fixed-mobile • ~3-5x WiFi range for non-LOS services, e.g. ~50 Mbps @ 250m

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

  7. Sample Applications: Cellular Data Boost • “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. Sample Applications: Distribution/Backhaul Distribution and Backhaulusing White Space

  9. Sample Applications: Long range V2V/Emergency Network • Long-range V2V useful for traffic control/warnings, geographic apps, p2p content, etc. Supplements short-range 802.11p/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 AP’s • Application requirements well matched with WS range/bit-rate properties

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

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

  13. Case for Noncontiguous OFDMA - I C • Three available channels • Node A transmits to node C via node B. • Node B relays node A’s data and transmits its • own data to node C. • Node X, an external and uncontrollable • interferer, transmits in channel 2. 3 1 2 2 B X A • 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 #3: Non-Contiguous OFDM (NC-OFDMA) #1: Contiguous OFDM #2: Multiple RF front ends Nulled Subcarrier C C C 3 1 3 1 1 2 B B B 2 2 2 X X 2 X 3 2 A A A NC-OFDM accesses multiple fragmented spectrum chunks with single radio front end • Spectrum fragmentation limited by number of radio front ends • Transmission in link BC suffers interference in channel 2 14

  15. NC-OFDM Operation Non-Contiguous OFDM Nulled Subcarrier 0 X[2] = AP 3 1 X[1] x[1] X[1]X[3] Parallel to Serial Modulation Serial to Parallel IFFT D/A x[2] x[3] B 2 X[3] X 2 • 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. A NC-OFDM accesses multiple fragmented spectrum chunks with single radio front end

  16. Resource Allocation in NC-OFDMA • 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 Benefits: • Avoids interference, incumbent users • Uses better channels • Each front end can use multiple fragmented spectrum chunks

  17. 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) f2 f3 f1 rate r2 rate r1 rate r3 freq LINK 3 LINK 1 LINK 2 Rates r1, r2, r3 periodically adjusted via cooperative procedures

  18. Architectures for Secondary Coexistence • 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 Spectrum Server (optional) freq Secondary B Spectrum Secondary A Spectrum Internet WS AP w/ backhaul Control information WS Mobile Access Protocol Common Coordination Channel (optional) Secondary System A Secondary System B

  19. Distribution and Backhaulusing White Space 3G WHITESPACES WIFI FIBER BACKHAUL NETWORK WINLAB

  20. Outline WINLAB 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?

  21. How will it look? • 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 • FCC’s max allowed height=30 m • FCC’s max TX power=4 W • Based on fixed devices rules of FCC WINLAB

  22. What will it do? Use of Sector antennas for more concentrated transmission Antenna coverage Fiber Internet user Wifi Wireless Distribution and Backhaul 4 sector antennas WINLAB

  23. Can White Spaces be used? FIRST ORDER CRITERION Use Radio > Achievable Capacity Demand (per cell) (per cell) Use Fiber < Resources used: FCC rules Internet traffic survey Propagation models Internet usage statistics NJ pop statistics Census 2000 WINLAB

  24. NJ towers at a glance • Towers in NJ, NY, DE & PA • Coverage can be 100km (r) WINLAB

  25. FCC’s Protection rule Available Bandwidth Secondary White Space radio WINLAB

  26. Available space per channel Channel availability including adjacent channel effect 25 TV tower coverage Additional separation ring Available for possible use Available as White Spaces 24 25 26 Available Bandwidth WINLAB

  27. Bandwidth Database 25 Available Bandwidth X WINLAB • 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. Frequency reuse planning reuse factor (r) of 2 : Available Bandwidth WINLAB • SNR at cell-2 = 19 dB • SNR at cell-4 = 5 dB • Interference • 14dB 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

  29. > Achievable Capacity Demand < WINLAB

  30. Let’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 WINLAB

  31. US Census 2000 Our Approximation > Achievable Capacity Demand < • 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) WINLAB

  32. Let’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: 116.9 GB/hr WINLAB

  33. Let’s consider one cell > α = 30% & 18 MB/hr/link : 75.7 > 11.7 Achievable Capacity Demand < α = 30% & 90 MB/hr/link : 75.7 > 58.4 α = 30% & 126 MB/hr/link : 75.7 < 81.8 FIBER α = 30% & 180 MB/hr/link : 75.7 < 116.9 FIBER WINLAB

  34. How many cells need fiber?(out of 307) 18 MB/hr 90MB/hr 126 MB/hr 180 MB/hr Cells requiring fiber connection WINLAB

  35. Aggregating Multiple Flows CLUSTER CLUSTER HEAD FIBER WINLAB 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

  36. Example 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: • Worst case requires 10 more fiber cells WINLAB

  37. Conclusions and future work WINLAB • 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 it’s 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

  38. White Space: Where are we today? WINLAB • 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

  39. White Space: Where will we go? WINLAB “Green” trumps “White”?

  40. PILOT PROJECT: “Broadband to Bivalve” WINLAB

  41. PILOT PROJECT: “broadband to bivalve” WINLAB • 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.

  42. PILOT PROJECT: “broadband to bivalve” WINLAB • Hardware: Radio Router Node based on currently available second generation ORBIT platform • Multiple radio interfaces: 802.11 (wifi), 802.16 (wimax), LTE, ZigBee, Bluetooth, CRKit (whitespace capable) • Software: Whitespace Routing Protocol optimized for throughput • Local (hotspot) support • Caching capabilities

  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):153-160, January 2008. • 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. 2055-2065, 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 MILCOM’2011, 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. 117-129, January 2012

  44. Acknowledgments • 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

More Related