Extreme Bandwidth Wireless Area Networks Utilizing Terahertz Frequencies
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The document discusses the potential for using terahertz frequencies, which exist in the largely unregulated spectrum between 100 GHz and 10 THz, to enable wireless networks with bandwidth well beyond existing technologies. Key advantages include the vast amount of unused spectrum available and the possibility to provide gigabit wireless networks without straining regulated radio frequencies. Challenges include inherent atmospheric attenuation at terahertz frequencies and developing low-cost transmission and modulation methods to facilitate widespread adoption and drive efficient usage over time.
Extreme Bandwidth Wireless Area Networks Utilizing Terahertz Frequencies
- 1. Extreme Bandwidth- Wireless Area Networks Utilizing Terahertz Frequencies Date: 2007-07-06 July 2007 David Britz AT&T Labs Slide Authors:
- 2. Abstract True gigabit wireless networks will likely strain available FCC defined spectrum. Devices and networks operating in that shared spectrum space will necessarily be expensive to deploy and operate. The author examines the possibility of utilizing spectrum beyond 100Ghz and well into the unregulated spectrum of Terahertz frequencies, to exploit the vast essentially unused spectrum with low cost technology (inefficient) transceiver and modulation methods that allow many people to get in on the new opportunity – creating a large market that then heads toward more efficient usage methods over time. July 2007 David Britz AT&T Labs Slide
- 3. July 2007 David Britz AT&T Labs Slide To deliver greater bandwidth, every new 802.11 standard has historically demanded new spectrum allocation! As an example 802.11n, to deliver 100Mbs requires spectrum at 40 MHz channels. So what spectrum will be needed for Gigabit WLAN’s? How many bits per Hz? (cheap or expensive systems) Does the FCC even have the available spectrum needed to support Gigabit WLAN’s? To follow Moore's Law in bandwidth scaling, perhaps it’s time to consider going above the FCC’s spectrum purview!
- 4. July 2007 David Britz AT&T Labs Slide How many 1 gigabit channels are available (assuming 2.5 Gigahertz channel spacing)? 2 (channels) 3 (channels) 1 (channel) 6 (channels) 8 (channels) 10 (channels) 5 (channels) 4 (channels) 2 (channels) 6 (channels) 10 (channels) 10 (channels) 4 (channels) 5 (channels)
- 5. July 2007 David Britz AT&T Labs Slide Terahertz Frequencies ter·a·hertz (tĕr ' ə-hûrts') n. ( Abbr. THz) One trillion (10 ) hertz. So what’s it good for? Truly enormous bandwidth per channel (10-100+ Gbps)! But nature gives you nothing for free Think short distances 10 -100 meters 12
- 6. July 2007 David Britz AT&T Labs Slide X Ray Energies Radio Energies Ultra Violet Energies Far Infra Red Energies 0.001 µm 0.4 µm 0.75 µm 3.0 µm 30.0 µm 1.0 mm Radio Spectrum Spectra of Optical, Terahertz and Radio Frequencies Visible Light Current Commercial Radio Spectrum “ Optical” Spectrum Mid Infra Red Energies Near Infra Red Energies 0.91 µ 1.5-1.6 µ ITU 1.3 µ 10 µ 0.85 µ 1.0 µm 1000.0 µ 1.0 µm= 1 Millionth of a Meter 25.4 µ = 1/1000 of an inch 75 µ (3/1000”) thickness of human hair Scale: “ Terahertz” Spectrum 1nm channel @1550nm = 124.8 GHz 1.0 nm = 1 Billionth of a Meter Wavelength 300.0 µm 1THz 1.0 THz = 1000 GHz (300 µm) Thickness of 4 human hairs 0.4 -0.75 µm= Visible light 10 THz 300 GHz FCC Cutoff 100 THz 100 GHz spacing Current Commercial Optical Fiber & FSO Spectrum There is plenty of unused spectrum out there We Just haven't figured out how to use it 100 GHz Advanced Laser designs provide optical channels at Visible Light Energies
- 7. July 2007 David Britz AT&T Labs Slide Optical Photon Emission Tightly bound electrons can only move when provided discreet (quantized ) excitation energy matching a particular shell radius. Electrons closer to the binding nucleous require more excitation energy. The higher the energy the shorter the wavelength (higher frequency) photon released. - Conservation of Energy Excitation energy gained by an accelerated electron (momentum) is released by the electron as an electromagnetic disturbance called a photon λ Terahertz Photon Emission Unbound electrons oscillating within a magnetic field (Free Electron Laser) Intermediate excitation levels, intermediate wavelengths released λ - e‾ + Radio Photon Emission Loosely bound electrons jumping between the outer electron shells of conductor atoms. Lower energy excitation needed, lower energy (longer wavelength) Released. - + - - λ e‾ + +
- 8. July 2007 David Britz AT&T Labs Slide The Absorption Chasm Between The Optical And Radio Electromagnetic Spectrum Terahertz
- 9. July 2007 David Britz AT&T Labs Slide 100 THz 3 µm 10 THz 30 µm 1 THz 0.30 mm 100 GHz 3 mm 10 GHz 30 mm 0.1 100.0 1000 1.0 10.0 ATTENUATION dB/Km DRIZZL 0.25mm/Hr Heavy Rain 25mm/Hr Deluge 150mm/Hr FOG (0.1gm 3 Visibility 50m 20” 1Atm H 2 O H 2 O H 2 O H 2 O CO 2 CO 2 CO 2 O 2 O 2 H 2 O 1000 THz 0.3 µm Visible Millimeter Sub-Millimeter Infrared 0.01 O 3 Avoiding Deep Molecular Absorption Bands Broadening IR spectrum into longer wave Broadening Radio spectrum into Sub Millimeter wave 1000 dB/Km wall FCC 300GHz Radio Boundary Existing Optical Fiber & FSOC Commercial RF Spectrum
- 10. July 2007 David Britz AT&T Labs Slide Astronomy Orbital and ground based study of cold interstellar molecular clouds of singly ionized nitrogen and carbon monoxide -contributing to early galactic formation Remote Sensing Atmospheric sensing of pollutants and composition Medical Imaging Penetrates non polar materials, skin and soft tissue may be a safe X-Ray replacement Materials Analysis THz frequencies interact aggressively with polar molecules (water), most molecules have vibration and rotational emission and absorption spectral Security Terahertz detectors can now detect passive emissions from human bodies and objects hidden within clothing Terahertz scanners can penetrate sealed packages Return spectra can identify material composition (spectral fingerprint) Indoor and Outdoor Wireless LANs (10-100+ Gbps) Radio tags Intelligent home device interface Personal Space Broadband Networks Terahertz & Extreme Gigahertz frequencies can propagate like radio, but be brought to a focus like light. Terahertz Imaging 100 Gigahertz ESA -Herschel Spacecraft
- 11. July 2007 David Britz AT&T Labs Slide FSOC P to P & Mesh P to MP 10 feet 100 feet 1 mile 10 miles 1 Peak Data Rate Range Wider Area, More Mobility 10 100 4G Wireless NAN 2.4 & 5 GHz 4G H/S Wireless LAN 2.4 & 5 GHz Unlicensed 3G/802.16 Wireless Various Bands 3G/MAN Fixed or Pedestrian Higher Rate, Less Mobility Megabits per Second/User 2.5G Mobile/Pedestrian 3G/MAN Mobile .1 Bluetooth PANs 2.4GHz and UWB ZigBee (Europe) 2/2,5G Wireless 800 MHz, 2 GHz ZigBee ZigBee (US) UWB Slide provided by Robert R. Miller, Director AT&T Labs Research THz Shrinking Radio Cell Size
- 12. July 2007 David Britz AT&T Labs Slide Electronic Entertainment, Gaming, Shopping, Smart Home And Medical Monitoring PAN’s Education, Business Information And Telepresence Services In Home Terahertz Network Entertainment Productivity 2005+ Vision GATEWAY Utility IP Home QoS Networks Metallic Narrowband Optical Fiber Legacy Eqpt. Wireless 4G Radio FSOC Audio Video Telematics Vehicle Monitoring Etc… Wireless Terahertz TV VCR Audio System Remote Control Camcorder... PC Printer Scanner... Phone Fax Environmental Security Medical & PAN’s Domestic apps… Wireless Terahertz Electronic Entertainment, Gaming, Shopping, Smart Home And Medical Monitoring PAN’s Education, Business Information And Telepresence Services In Home Terahertz Network Entertainment Productivity 2005+ Vision GATEWAY Utility IP Home QoS Networks Metallic Narrowband Optical Fiber Legacy Eqpt. Wireless 4G Radio FSOC Audio Video Telematics Vehicle Monitoring Etc… Wireless Terahertz TV VCR Audio System Remote Control Camcorder... PC Printer Scanner... Phone Fax Environmental Security Medical & PAN’s Domestic apps… Wireless Terahertz FoodMart FoodMart
- 13. July 2007 David Britz AT&T Labs Slide Terahertz (GigE) up/down link From terminal to airplane Terminal Link (fiber back to building ) Airplane Link Short distance Terahertz links use low power safe wavelengths and are capable of transmitting GigE capacity Autonomous reading (imaging scanning) of freight destination tags In-Plane broadband connectivity
- 14. July 2007 David Britz AT&T Labs Slide 3 Tiered Overlay / Underlay Optical Fiber, FSOC, Terahertz Access Network Layers are transparent and non-interfering with each other
- 15. July 2007 David Britz AT&T Labs Slide Nano Wire Terahertz detector chip level device University at Buffalo; Andrea Markelz and Jonathan Bird MIIM Terahertz detector announced May 16 th 2006 EE Times 2 µm SiO2 encapsulated Nb microbolometer Array Free electron laser producing terahertz radiation from localized surface charges moving across a grating Vermont Photonics An electromagnetic wave is produced by this broadband short-pulse terahertz source when a dc bias is placed across the antenna and an ultra short pump-laser pulse is focused in the gap. Terahertz wireless links will connect the customer or device to the surrounding network or to other devices via short distance , intelligent, cooperative and widely distributed In-building and terrestrial wireless access points. (Micro - Municipality model) Examples Of Terahertz Sources and Receivers
- 16. July 2007 David Britz AT&T Labs Slide Creating Imaging systems at Terahertz frequencies is conceptually and practically easy. Building a robust communications infrastructure is not! P-to-P P-to-MP Free Space Terahertz Transmission LOS O to T Optical Signal Electromagnetically Driven Modulators 10¹ ² Hertz Optical Signal Source T to E Tx Module Rx Module Optical Modulation RF Signal Processing AD AD Demodulator Decoder Data Baseband Q I Direct Optical Signal Processing T-to-O? Phase Based on maturing transceiver devices, Bandwidth beyond 100+Gbps are possible
- 17. July 2007 David Britz AT&T Labs Slide Groups and Standards Activities http://www.thznetwork.org/wordpress The Terahertz Technology Forum of Japan Terahertz Science and Technology Network, USA The Virtual Journal of Terahertz Science and Technology GODOT, a European consortium of THz groups IEEE 802.15, TG 3c WPAN, IEEE P802.15 SCwng Conferences ITW - International Terahertz Workshop (Sandbjerg, Denmark, September 17-19, 2000) The 2004 DOE-NSF-NIH Report on Opportunities in THz Science OSA Topical Meeting on Optical Terahertz Science and Technology (Orlando FL, March 14-16, 2005) IRMMW - THz 2006 (Shanghai, Sept. 18-22, 2006) SPIE East THz Physics, Devices and Systems (Boston Oct 1-4 2006) The THz center at RPI CUOS, University of Michigan University of California, Berkeley Columbia University Case Western Univ. of Alberta, Edmonton Center for Terahertz Science and Tech, UCSB Oklahoma State University NJIT Purdue University University of Chicago Oregon State University Georgia Tech Syracuse University Colgate University Univ. of Maryland Picometrix, Inc. (home of the T-Ray 2000TM) Physical Sciences, Inc. Los Alamos National Laboratory Yale University SUNY Buffalo Microwave Laboratory, Ohio State University Jefferson Lab University of Toronto UMBC Johns Hopkins University Research & Development
- 18. July 2007 David Britz AT&T Labs Slide Use of the radio spectrum has seen the upper frequency for communications increase about a decade every 20 years. At this rate, by 2020 0.5 to 1THz will be used for wireless communications T.S. Bird 2004 (CSIRO ICT Centre) Indoor and Terrestrial Wireless Personal Space Networks Key challenges will be; Inherent atmospheric attenuation conditions Inter-room isolation (doesn't go through walls---good or bad?) Network planning for multi-layered small-cell dynamic cluster configurability Minimize network backhaul, intelligent edge and localized cluster routing (rapid cell transit and handoffs) Physical layer and device interoperability standards (IEEE 802.11/15. 3c, ZigBee IEEE 802.15.4 Intelligent home/commercial sensors, device interoperability, common air interface). Localized intelligent cluster element coordination and management, (high density reuse of channel frequencies and inter-device cooperation). Device power (input and transmit) Suitable transceivers System and device cost Mass distribution and deployment (smart dust model).
- 19. July 2007 David Britz AT&T Labs Slide Indoor and Terrestrial Wireless Personal Space Networks Take Away Key Advantages; Bandwidth well beyond any existing wireless technology No FCC licensing or spectrum allocation, Terahertz is unlicensed spectrum Terahertz starts at 300GHz – not so far from existing 90-100GHz technology and development experience Like any new frontier, Terahertz users can afford to be initially greedy and wasteful of their spectrum resource since there is so much of it to exploit. This exploitation and growing market in turn encourages the creation of low cost (inefficient) transceiver and modulation methods that allow many people to get in on the new opportunity – creating a large market that then heads toward more efficient usage methods over time. Conversely increasingly expensive but efficient signal and channel processing methods are critical for today's radio spectrum management as the availability of radio spectrum is being increasingly challenged by competitive demands for that limited spectrum
- 20. July 2007 David Britz AT&T Labs Slide Thank You David Britz AT&T Shannon Labs dbritz@research.att.com
- 21. July 2007 David Britz AT&T Labs Slide Empirical relationship based on measured liquid water content and using analytic expression based on Mie scattering calculations. Ground effect microclimate Ground Effect On Fog Courtesy of Christos Kontogeorgakis Virginia Polytechnic Institute and State University
- 22. July 2007 David Britz AT&T Labs Slide At Low temperatures the peak of the blackbody power curve lies in the THz range. The dashed line is the wave number at 1THz, wave numbers from 3.3 to 333.3cm¹ corresponds to 0.1 to 10THz.
Editor's Notes
- #2: doc.: IEEE 802.11-yy/xxxxr0 Month Year John Doe, Some Company Page