Millimeter Wave MIMO Communication

Transcription

1 Millimeter Wave MIMO Communication Professor Robert W. Heath Jr., PhD, PE Wireless Networking and Communications Group Department of Electrical and Computer Engineering The University of Texas at Austin

2 Robert W. Heath Jr. (2015) Heath Group in the UT Austin 12 PhD students mmwave communication and radar for car-to-car! mmwave precoding! mmwave wearables! mmwave for tactical ad! hoc networks! mmwave for infrastructure-to-car! next generation! mmwave LAN! mmwave licensed shared access for 5G! mmwave 5G performance! 2

3 Motivation 3

4 Robert W. Heath Jr. (2015) Why millimeter wave for consumer wireless? cellular 300 MHz 30 GHz u u u UHF (ultra high frequency) spectrum! note: log scale so even smaller over here WiFi 3 GHz 300 GHz Huge amount of spectrum possibly available in mmwave bands Technology advances make mmwave possible for cheap consumer devices mmwave research is as old as wireless, e.g. Bose 1895 and Lebedew 1895 large bandwidth communication channels 4

5 Millimeter wave for the consumer 5

6 Naked body scanner Ok this is mmwave system that uses the consumer Image from 6

7 Robert W. Heath Jr. (2015) mmwave in consumer applications MercedesBenz Distronic (ACC Radar) 79 PreCrash System : 2004 Lexus VOLVO Collision Warning with Auto Brake (CWAB) 3rd Generation Long Range Radar-Bosch Short range radar SiGe electronics Frequency (in GHz) 77 Honda Inspire Collision Mitigation Brake System 60 MB Sclass : one LRR and six 24 GHz UWB WirelessHD SRR Cadillac Virtual bumpers IEEE adWilocity Chipset Silicon Image WiGig Ultra 4K HD LAN PAN 35 5G Cellular Wireless LAN Wireless HD products shipping products shipping Automotive Radar built by AEG-Telefuken 1974 Medium range radarbosch Year Source: Holger H Meinel and Juergen Dickmann. Automotive radar: From its origins to future directions. Microwave Journal, 56(9),2013.

8 Automotive radar 77 GHz LRR! ACC! 79 GHz! MRR! Stop&Go! Cross Traffic Alert! (CTA)! 79 GHz! SRR! Precrash! Precrash! Blind Spot! Detection! (BSD)! Lane Change Assistance! (LCA)! u Long range radar (LRR) is used for automatic cruise control (ACC) Robert W. Heath Jr. (2015) Type LRR MRR SRR Frequency band (GHz) Bandwidth (GHz) Range (m) Distance accuracy u Medium range radar (MRR) supports CTA, LCA, stop&go and BSD u Short range radar (SRR) is used for parking aid and precrash applications *J. Hasch, E. Topak, R. Schnabel, T. Zwick, R. Weigel, and C. Waldschmidt, Millimeter-wave technology for automotive radar sensors in the 77 GHz frequency band, IEEE Transactions on Microwave Theory and Techniques, vol. 60, no. 3, pp , **R. Mende and H. Rohling, New automotive applications for smart radar systems, in Proc. German Radar Symp., Bonn, Germany, Sep. 3 5, 2002, pp ***R. Lachner, Development Status of Next generation Automotive Radar in EU, ITS Forum 2009, Tokyo, 2009, [Online]. Available. J3Schedule/ P22/ lachner pdf 8

9 WLAN and WPAN Standard Bandwidth Rates Approval Date WirelessHD 2.16 GHz Gbps Jan IEEE ad 2.16 GHz 6.76 Gbps Dec Dell Laptop** u Standards unlicensed 60 GHz band ª WirelessHD: Targeting HD video streaming ª IEEE ad: Targeting Gbps WLAN u Compliant products already available ª Dell Alienware laptops, Epson projectors, etc. ª 11ad Chipset available from Wilocity, Tensorcom, Nitero u Only single stream MIMO beamforming ª Next generation will likely support multiplexing (>20 Gbps)* Epson projector** Wilocity s chipset*** Tensorcom s chipset*** * ** *** 9

10 5G cellular mmwave BS Conventional BS Wireless backhaul Control signals Indoor user Buildings Femtocell LOS links Data center Multiple-BS access for fewer handovers and high rate mmwave D2D Non-line-of-sight (NLOS) link u Repurpose existing mmwave spectrum for mobile cellular applications ª MmWave used to provide high throughput in small geographic areas u Many different applications of MIMO communication ª Single user, multiple user, multi-cell, relay ª Interference and mobility become more of a challenge *T. S. Rappaport, R.W. Heath, Jr., J. N. Murdock, R. C. Daniels, Millimeter Wave Wireless Communications, Pearson, 2014 **T. Bai, A. Alkhateeb, and R. W. Heath Jr, Coverage and Capacity of Millimeter-Wave Cellular Networks, IEEE Coomm. Mag, vol.52, no.9, Sept ***T. Bai and R.W. Heath Jr, Coverage and Rate Analysis for Millimeter-Wave Cellular Networks, IEEE Trans. Wireless Comm., vol.14, no.2, Feb

11 Connected car Vehicle driving cloud u Attractive for vehicle-to-vehicle and vehicle-to-infrastructure u Enhanced local sensing capability in connected cars ª Share high rate sensor data: radar, LIDAR, video, IR video, other sensors ª Data fusion from other cars can enlarge the sensing range u Enable the transition from driver assisted to autonomous vehicles ª Develop a better understanding of the local environment ª Seamlessly scales with more vehicles * NHTSA, Vehicle safety communications applications (VSC-A) final report, Sep

12 Wearables Device to track dog s activity Connected pet Augmented reality glasses Fitness trackers Connected person Wireless headset Smart watch Smart phone u Multiple communicating devices in and around the body ª 5 or more devices per person based on market trends trend u MmWave solves two critical problems ª Provides high data rates for high-end devices ª Provides reasonable isolation for low-end devices 12

13 MIMO at mmwave 13

14 Why MIMO at mmwave? millimeter wave band, possible locations of 5G cellular deployment 1.3 GHz 2.1 GHz 7 GHz (unlic) 10 GHz several GHz of spectrum is promising but found in many separate bands 28 GHz 37 / 42 GHz spatial multiplexing & beamforming isotropic radiator mmwave aperture 60GHz E-Band just beamforming to 300 GHz multiple data streams TX RX sub-6ghz aperture Beamforming for antenna gain Spatial multiplexing for spectral efficiency Shu Sun, T. Rappapport, R. W. Heath, Jr., A. Nix, and S. Rangan, `` MIMO for Millimeter Wave Wireless Communications: Beamforming, Spatial Multiplexing, or Both?,'' IEEE Communications Magazine, December

15 Some key differences Sub 6GHz MmWave bandwidth 1-160MHz 100MHz-2GHz role of antennas multiplexing & diversity array gain & multiplexing exploiting channel limited feedback directional beamforming BS 1 to 8 32 to 256 UE 1 or 2 1 to 32 scattering rich sparse urban coverage via diffraction via reflection penetration loss low high large-scale fading distant dependent + shadowing distant dependent + blockage 15

16 Significance of blockage X line-of-sight non-line-of-sight blockage due to buildings blockage due to people User Base station Handset X Blocked by users body hand blocking self-body blocking many forms of blockage have yet to be modeled and analyzed 16

17 MIMO mmwave Architectures 17

18 MIMO receiver at < 6 GHz frequencies 2 to 8 antennas Chain ADC Bandwidths of MHz Chain ADC MIMO Combining Baseband and Precoding Equalization All interesting MIMO processing performed in digital Chain ADC # antennas = # = # pairs ADCs Conventional MIMO heavily leverages digital signal processing 18

19 Hardware constraints at mmwave Chain ADC 20mW 40mW Chain mw ADC Baseband processing Baseband Precoding For a receiver with 16 antennas, the power consumed by this front end would be 7.36 W!!! u Large antenna systems are employed at mmwave u Cost and power consumption of mmwave components are high Impossible to dedicate a separate chain and ADC for each antenna 19

20 MIMO receiver at mmwave frequencies 1 to 256 antennas Bandwidths of GHz Analog processing Analog processing Analog processing Chain Chain Chain Joint processing ADC ADC ADC Bas eban Baseband Processing d Prec odin Some MIMO processing may be performed in analog # antennas >= # >= # pairs ADCs Power and complexity force different implementation tradeoffs at mmwave 20

21 MIMO architectures at mmwave: analog beamforming beamformer combiner Baseband ain DAC Chain H Chain ain ADC Baseband Phase shifters u Use a network of phase shifters ª Constant gain and quantized angles ª Power consumption in the phase shifter depends on the angle resolution u Joint search for optimal beamforming and combining vectors w/ codebook The defacto approach for IEEE ad and WirelessHD 21

22 MIMO architectures at mmwave: hybrid precoding Robert W. Heath Jr. (2015) chain chain Baseband Baseband Precoding Precoding 2-4 chains Precoding H Combining 2-4 chains Baseband Combining Digital can correct for analog limitations chain chain Combined analog and digital beamforming u Makes compromise on power consumption and hardware complexity u Enables spatial multiplexing and multi-user MIMO u Digital can correct for analog limitations Current topic of interest for NG60 and cellular 22

23 Robert W. Heath Jr. (2015) Hybrid precoding with phase shifters, switches or lenses. + Precoding Lenses N r. + M r Phase shifters. + Switches M r. + mmwave Beam Selector N r dim. Lens N r M r. + M r. + 23

24 MIMO architectures at mmwave: combining with 1-bit Chain 1-bit ADC 1-bit ADC Different transmit architectures possible Transmit Processing H Baseband Processing Baseband Precoding Chain 1-bit ADC 1-bit ADC 10mW 1 bit, 240 GHz u Use1-bit ADCs (pair) for each chain, ultra low power solution u Can approach the capacity of the unquantized solutions Of significant academic interest, industry is non-committal

25 MIMO architectures at mmwave: line-of-sight MIMO Transmitter D 1 2 n R θ T Receiver 1 2 n Angular separation of the Tx elements θ D T R Angular resolution of the Rx array θ res λ n D θ θ T res R λ D = n u Multiple parallel mmwave LOS MIMO links can be established ª Antenna element spacing from diffraction-limited optics ª Links are robust to deviations in alignment and array positioning u Applications ª Data centers ª Chip-to-chip Some academic interest Picture from C. Sheldon, E. Torkildson, M. Seo, C. P. Yue, M. Rodwell, and U. Madhow, Spatial multiplexing over a line-of-sight millimeter-wave MIMO link: A two-channel hardware demonstration at 1.2Gbps over 41m range, in 38th European Microwave Conference, October

26 Multi-user mmwave channel estimation 6 s 1 s N Chain Beamformers N F Chain Base station N BS N MS combiner w u uth mobile station u Compressed sensing based channel estimation* ª Exploits the sparse nature of the channel ª All users channels are trained at the same time ª Trade-off between training overhead & estimation quality Chain Effective Achievable Rate (bps/ Hz) L C = 600 symbols L C = 400 symbols L C = 200 symbols Number of Measurements (M BS x M MS ) BS s has 64-ant. ULA 4 MS s with 32-ant. ULA each Training that maximizes the achievable rate *A. Alkhateeb, G. Leus, and R. W. Heath Jr, Compressed-Sensing Based Multi-User Millimeter Wave Systems: How Many Measurements Are Needed? in Proc. of the international conference on Acoustics, Speech, and Signal Processing (ICASSP), Brisbane, Australia, April

27 Research directions signal processing compressive channel estimation blockage models channel measurements propagation channel models information theory hybrid precoding for single and multiple users beam training and feedback cellular systems stochastic geometric analysis of mmwave cellular systems performance in broadband channels capacity with low resolution ADCs non-coherent or wideband capacity going beyond 120 GHz other communication theory device architectures protocols 27

28 Application specific challenges 5G cellular Energy efficient architectures Precoding and combining Channel estimation and feedback Synchronization Modulation Wideband channel models Network densification Backhaul WLAN/WPAN Spatial multiplexing Link robustness Coverage Wearables Low power operation Support for omni ant. MACs for interference management Robert W. Heath Jr. (2015) V2X and radar Joint waveform design V2X channel models Radar-comm. tradeoffs Cloud processing Full duplex of sensor data Data fusion Antenna placement Beam alignment 28

29 Conclusions 29

30 Millimeter wave is coming to a wireless system near you 30

31 Heath group mmwave references u u u u u u Overviews ª T. Rappapport, R. W. Heath, Jr., R. Daniels, J. N. Murdock, Millimeter Wave Wireless Communications, Pearson Education, Inc ª Shu Sun, T. Rappapport, R. W. Heath, Jr., A. Nix, and S. Rangan, MIMO for Mil- limeter Wave Wireless Communications: Beamforming, Spatial Multiplexing, or Both?, IEEE Communications Magazine, vol. 52, no. 12, pp , Dec ª Ahmed Alkhateeb, Jianhua Mo, N. Gonzalez Prelcic and R. W. Heath, Jr., MIMO Precoding and Combining Solutions for Millimeter Wave Systems, IEEE Communications Magazine, vol. 52, no. 12, pp , Dec ª Tianyang Bai, Ahmed Alkhateeb, and R. W. Heath, Jr., Coverage and Capacity of Millimeter Wave Cellular Networks, IEEE Communications Magazine, vol. 52, no. 9, pp , Hybrid precoding ª Ahmed Alkhateeb, G. Leus and R. W. Heath, Jr., Limited Feedback Hybrid Precoding for Multi-User Millimeter Wave Systems, submitted to IEEE Trans. on Wireless, September Available at ArXiv. ª Ahmed Alkhateeb, O. El Ayach, G. Leus and R. W. Heath, Jr., Channel Estimation and Hybrid Precoding for Millimeter Wave Cellular Systems, IEEE Journal on Sel. Topics in Sig. Proc., special issue on Massive MIMO Communication, vol. 8, no. 5, pp , October ª O. El Ayach, S. Abu-Surra, S. Rajagopal, Z. Pi, and R. W. Heath, Jr., Spatially Sparse Precoding in Millimeter Wave MIMO Systems, IEEE Trans. on Wireless, vol. 13, no. 3, pp , March Coverage and capacity in cellular systems ª Tianyang Bai and R. W. Heath, Jr., Coverage and Rate Analysis for Millimeter Wave Cellular Networks, IEEE Trans. on Wireless, vol. 14, no. 2, pp , Feb Previous version available at ArXiv. Wearable networks ª K. Venugopal, M. Valenti, and R. W. Heath, Jr., Interference in finite-sized highly dense millimeter wave networks, (invited) Proc. of the Information Theory and Applications, San Diego, California, February 1-6, One-bit ADCs ª Jianhua Mo, P. Schniter, N. Gonzalez Prelcic and R. W. Heath, Jr., Channel Estimation in Millimeter Wave MIMO Systems with One-Bit Quantization, to appear in the Proc. of the Asilomar Conf. on Signals, Systems, and Computers, November 2-5, ª Jianhua Mo and R. W. Heath, Jr., Capacity Analysis of MIMO Systems with One- Bit Quantization, submitted to IEEE Trans. on Signal Processing, September Available at ArXiv. Security ª N. Valliappan, A. Lozano, and R. W. Heath, Jr. Antenna Subset Modulation for Secure Millimeter-Wave Wireless Communication, IEEE Trans. on Communications, vol. 61, no. 8, pp , Aug