Wireless Communications with sub-mm Waves - Specialties of THz Indoor Radio Channels

Transcription

1 Platzhalter für Bild, Bild auf Titelfolie hinter das Logo einsetzen Wireless Communications with sub-mm Waves - Specialties of THz Indoor Radio Channels Sebastian Priebe, Thomas Kürner,

2 Wireless Communications with sub-mm Waves - Specialties of THz Indoor Radio Channels 1. Introduction Why THz Frequencies for Communications? Feasibility Study Towards a Standard for THz Communications 2. The THz Indoor Radio Channel 3. Channel Measurements/Modeling 4. Summary Sebastian Priebe Wireless Communications with sub-mm Waves 2/22

3 Why THz Frequencies for Indoor Communications? (1) Common ground with nanonetworks: Terahertz frequencies, i.e. 300 GHz 3 THz, for data communications What are the drivers? Nanonetworks: Natural radiation of THz frequencies with graphene antennas Wireless indoor communications: Up to 100 Gbit/s required within a few years from now Sebastian Priebe Wireless Communications with sub-mm Waves 3/22

4 Why THz Frequencies for Indoor Communications? (2) Problem: Hardly any unregulated spectrum available below 300 GHz 3 khz 300 khz 300 khz 3 MHz 3 MHz 30 MHz 30 MHz 300 MHz 300 MHz 3 GHz 3 GHz 30 GHz 30 GHz 300 GHz à Shift to carrier frequencies in the THz range from 300 GHz onwards Sebastian Priebe Wireless Communications with sub-mm Waves 4/22

5 Why THz Frequencies for Indoor Communications? (3) Aim: Ultra high data rates of 100 Gbit/s and beyond over rather short distances Potential scenarios: Gbit/s Gbit/s (1) WPAN (2) Kiosk downloads Gbit/s Gbit/s à But: Is THz communication feasible? (3) WLAN (4) Video streaming Sebastian Priebe Wireless Communications with sub-mm Waves 5/22

6 Feasibility Study Transmission of a DVB-T test signal at 300 GHz: à Data rate: 36 Mbit/s with 64 QAM modulation à Achieved distance: 52 m à THz data transmission is technically feasible à Strong, increasing interest in sub mm-wave communications Sebastian Priebe Wireless Communications with sub-mm Waves 6/22

7 Towards a Standard for THz Communications On the way to 100 Gbit/s THz WPANs/WLANs: An international system standard will be required Feasibility studies Initiation of the IEEE THz Interest Group Propagation investigations Channel measurements Propagation modeling System simulations System design guidelines IEEE standard IEEE standard for for THz WPANs/ WLANs WLANs THz WPANs/ Accurate propagation modeling is necessary as input for system simulations à How does the THz indoor radio channel behave? à What are arising challenges? Sebastian Priebe Wireless Communications with sub-mm Waves 7/22

8 Wireless Communications with sub-mm Waves - Specialties of THz Indoor Radio Channels 1. Introduction 2. The THz Indoor Radio Channel Conventional vs. THz Radio Channels Propagation Mechanisms 3. Channel Measurements/Modeling 4. Summary Sebastian Priebe Wireless Communications with sub-mm Waves 8/22

9 Conventional vs. THz Radio Channels Comparison of conventional and THz communication channels: 2.4 GHz, 5 GHz 60 GHz 300 GHz Data rates 600 Mbit/s 4 Gbit/s Up to 100 Gbit/s Bandwidths 40 MHz 2 GHz GHz Output powers Limited by regulations 22 dbm Limited by technology and regulations; typically 10 dbm Currently limited by technology only << 10 dbm Path loss at 10 m 60 db 88 db 101 db Antenna gains Low ( 3 dbi) Medium ( dbi) High ( dbi) à Huge bandwidths à Very high path losses low output powers à Specific propagation mechanisms? Sebastian Priebe Wireless Communications with sub-mm Waves 9/22

10 Propagation Mechanisms (1) Propagation attenuation: Total attenuation = free space loss + atmospheric attenuation db FSL [db] db db 900 MHz (GSM) GHz (WLAN) 60 GHz (WPAN) 300 GHz d [m] à Challenge: Very high (atmospheric) attenuation à Solution (1): Line-of-sight connection à Solution (2): Highly directive antennas à Solution (3): Transmission in atmospheric windows, e.g GHz, GHz Sebastian Priebe Wireless Communications with sub-mm Waves 10/22

11 Propagation Mechanisms (2) Huge occupied bandwidths >> 10 GHz Channel frequency dependency: Demonstration: Ray tracing in an empty room at GHz 96 4 m RX Path P CIR Gain [db] [db] Total Power LOS only Reflections only TX 6 m f [GHz] à Challenge: Significant frequency dispersion è pulse form distortion à Solution: Equalization or pulse pre-distortion Sebastian Priebe Wireless Communications with sub-mm Waves 11/22

12 Propagation Mechanisms (3) Typical building materials must be considered as rough at THz frequencies Wallpaper Plaster Diffuse rough surface scattering occurs à Challenge: Multipath propagation and high reflection losses à Solution: Directive antennas for spatial multipath suppression Sebastian Priebe Wireless Communications with sub-mm Waves 12/22

13 Propagation Mechanisms (4) Dynamic ray shadowing by person movement: à Challenge: Blockage of line-of-sight path with high additional attenuation à Solution: - Dynamic antenna redirection to a different indirect transmission path - Electrically steerable antennas Sebastian Priebe Wireless Communications with sub-mm Waves 13/22

14 Propagation Mechanisms (5) Ray shadowing by objects: Office room in top view Direction of antenna beam TX RX RX Non-line-of-sight area Screen causing shadowing à Challenge: No line-of-sight available, very high transmission attenuation à Solution: Use of directed non-line-of-sight path with steerable antennas Sebastian Priebe Wireless Communications with sub-mm Waves 14/22

15 Wireless Communications with sub-mm Waves - Specialties of THz Indoor Radio Channels 1. Introduction 2. The THz Indoor Radio Channel 3. Channel Measurements/Modeling 4. Summary Sebastian Priebe Wireless Communications with sub-mm Waves 15/22

16 Channel Measurements/Modeling (1) Measurement campaign: Channel transfer functions in typical indoor scenarios Channel sounding in frequency domain with vector network analyzer Ultra broadband at GHz Spatially resolved MIMO antenna configurations Vector Network Analyzer Frequency sweep: GHz Indoor Channel Aims: 1. Experimental investigation and understanding of THz radio channels 2. Validation of ray tracing propagation modeling 3. Calibration of the ray tracing tool 4. Development of a THz channel model Test Head Lens Automatic Rotation Unit VNA Sebastian Priebe Wireless Communications with sub-mm Waves 16/22

17 Channel Measurements/Modeling (2) Methodology: 1.) Measurements in an actual office scenario 2.) Digital 3D model of the scenario 3.) Ray tracing simulations 4.) Comparison of measurements and simulations à Validation of ray tracing modeling 3.59 m Windows Test Head Lens TX 2 Tables Ray 4 Ray 3 TX 1 LOS Ray Automatic Rotation Unit 4.52 m RX MIMO Shift Ray 2 Ray 1 VNA Wardrobes TX 3 z y x Door Sebastian Priebe Wireless Communications with sub-mm Waves 17/22

18 Channel Measurements/Modeling (3) Considered scenarios: Different offices Hallway Exemplary evaluations: Angular power spectrum Angular power delay profile 4.52 m TX 2 RX Tables Ray 4 MIMO Shift Ray m Ray 2 Ray 3 Windows TX 1 LOS Ray AoD [ ] Path Loss [db] Ray Ray LOS Ray 2 2 Ray Reflection at Lens Mount AoA [ ] Ray Relative Received Power [db] > Wardrobes 85 à Comparison with ray tracing propagation simulations y z x Door TX AoA [ ] τ [ns] Sebastian Priebe Wireless Communications with sub-mm Waves 18/22

19 Channel Measurements/Modeling (4) In-house development of a ray tracing tool Verification of ray tracing simulations with channel measurements at 300 GHz: Small office scenario TX Relative received power [db] Power delay profile c Simulations, x = 40 l r corr Measurements RX t [ns] à Very good agreement between simulations and measurements is achieved à Ray tracing proves well-suited to model THz propagation channels Sebastian Priebe Wireless Communications with sub-mm Waves 19/22

20 Channel Measurements/Modeling (5) Current status: Accurate propagation model available Feasibility studies Initiation of the IEEE THz Interest Group Propagation investigations Channel measurements Propagation modeling System simulations System design guidelines IEEE standard IEEE standard for for THz WPANs/ WLANs WLANs THz WPANs/ Future steps: à System simulations based on the propagation model à Development of an appropriate system design Sebastian Priebe Wireless Communications with sub-mm Waves 20/22

21 Wireless Communications with sub-mm Waves - Specialties of THz Indoor Radio Channels 1. Introduction 2. The THz Indoor Radio Channel 3. Channel Measurements/Modeling 4. Summary Sebastian Priebe Wireless Communications with sub-mm Waves 21/22

22 Summary THz communications......opens up huge unregulated bandwidths > 100 GHz...allows for wireless data rates of 100 Gbit/s and more...has plenty potential applications THz radio channels impose the challenges of......very high free space losses...additional atmospheric attenuation...significant frequency dispersion...rough surface scattering...ray shadowing by objects or persons Solutions are......high antenna gains...transmission in atmospheric windows...pulse form equalization...beam switching/beam steering Can be modeled with ray tracing FSL [db] db 28 db db 900 MHz (GSM) GHz (WLAN) 60 GHz (WPAN) 300 GHz d [m] Sebastian Priebe Wireless Communications with sub-mm Waves 22/22

23 Thank you for paying attention. Dipl.-Ing. Sebastian Priebe Sebastian Priebe Wireless Communications with sub-mm Waves 23/22