January doc.: thz_THz_Wireless_Communications_Challenges_and_Opportunities

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1 January 2017 doc.: thz_THz_Wireless_Communications_Challenges_and_Opportunities Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs) Submission Title: THz Wireless Communications: New Opportunities and Challenges Date Submitted: 5 January 2017 Source: Alenka Zajić Address 85 5 th Street NW, Atlanta GA Voice: , FAX: N/A, alenka.zajic@ece.gatech.edu Re: n/a Abstract: This talk focuses on chip-to-chip interconnects where wire-based interconnects are becoming a bottleneck for performance and scalability. Among wire-replacement candidates, wireless interconnect is especially promising because wireless links between chips would circumvent the pincount problem. Currently investigated mm-wave wireless interconnects face two problems: not enough bandwidth and antennas that are too big for successful integration. Both problems call for terahertz (THz)-range communications. We will talk about THz propagation and channel modeling in chip-tochip environments. Purpose: Information of IEEE IG THz Notice: This document has been prepared to assist the IEEE P It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P Submission Slide 1 Alenka Zajić (Georgia Tech)

2 THz Wireless Communications: New Opportunities and Challenges Prof. Alenka Zajić January 2017

3 Internet of Everything 3

4 Challenges for IoT and Wearable Devices Sensing a complex environment -Innovative ways to sense and deliver information from the physical world to the cloud Connectivity- Variety of wireless networks needed Cloud is important - IoT will require significant increase in data storage needs better rack-to-rack, device-to-device, and chipto-chip communication Security is vital - Detecting and blocking malicious activity IoT is complex IoT application development needs to be easy for all developers, not just to experts Power is critical 4

5 Applications That Need THz Communication Interconnects in Data Centers Wearable Devices Chip-to-Chip On Motherboard 5

6 Current Wireless Interconnects + antenna size/integration with chips +adding bandwidth without adding pins or fiber connectors to the chip package. - limited bandwidth For example, a computer in a typical high performance cluster gets 56 Gbits/s Wireless communication at mm- Wave frequencies: WiGig uses 60 GHz frequency range to provide up to 7 Gbits/s using OFDM, 64- QAM, and sophisticated coding. Power hungry systems 6

7 THz Transmitter and Receiver GHz Measurement System GHz Measurement System 7

8 Path Loss Measurement LoS NLoS Varying diffraction loss with different materials (FR4, metal, plastic) [1] S. Kim and A. Zajić, Statistical characterization of 300-GHz propagation on a desktop, IEEE Transactions on Vehicular Technology, vol. 64, no. 8, pp , Aug

9 Path Loss vs. Distance Freq. bands [GHz] Log-normality of path loss variation introduced by misalignment: PL 0 = db 9

10 Normalized PDP [db] Normalized PDP [db] Multipath Characterization (LoS) cm without ABS cm without ABS cm without ABS cm with ABS cm with ABS cm with ABS Excess Delay [ns] Excess Delay [ns] [2] S. Kim, W. T. Khan, A. Zajić, and J. Papapolymerou, D-band channel measurements and characterization for indoor applications, IEEE Transactions on Antennas and Propagation, vol. 63, no. 7, pp , July

11 Path Loss [db] Path Loss [db] Path Loss [db] Path Loss with Cylindrical Obstructions 35.56cm NLOS glass THEO 45.72cm NLOS glass THEO 76.20cm NLOS glass THEO 35.56cm NLOS glass MEAS 45.72cm NLOS glass MEAS 76.20cm NLOS glass MEAS 35.56cm NLOS plastic THEO 45.72cm NLOS plastic THEO 76.20cm NLOS plastic THEO 35.56cm NLOS plastic MEAS 45.72cm NLOS plastic MEAS 76.20cm NLOS plastic MEAS 85 (Glass) Frequency [GHz] cm NLOS Ceramic THEO 35.56cm NLOS Ceramic MEAS 45.72cm NLOS Ceramic THEO 45.72cm NLOS Ceramic MEAS 76.20cm NLOS Ceramic THEO 76.20cm NLOS Ceramic MEAS Frequency [GHz] (Plastic) Frequency [GHz] (Ceramic) 11

12 Diffraction [3] S. Kim and A. Zajić, UTD-Based Modeling of Diffraction Loss by Dielectric Circular Cylinders at D-band, Proceedings of IEEE International Symposium on Antennas and Propagation, pp. 1-2, June 26-July 1, 2016, Fajardo, Puerto Rico. 12

13 Diffraction 33 GHz 140 GHz 307 GHz 13

14 Chip-to-Chip Measurement Scenarios C D DIMM E Link A-B: CPU-AGP (Accelerated Graphics Port) - LoS with T-R height difference A B Link C-D: Directed NLoS with DIMM as reflecting surface Link E-F: OLoS through parallelplate structure (i.e., DIMM s, cards) F Corridor 14

15 Measurement Scenarios 1) LoS propagation between the Tx and Rx over the large ground plane 2) Processor-Memory Link (A-B Channel) 3) OLoS Link through Guided Metal Parallel-plate Structures (C-D Channel) 4) Heatsink Channel [4] S. Kim and A. Zajić, "Characterization of 300-GHz Wireless Channel on a Computer Motherboard," in IEEE Transactions on Antennas and Propagation, vol. 64, no. 12, pp , Dec

16 LoS over large ground plane Path Loss Received power dependent on antenna height and the location of ground-reflection Oscillation due to reflection from Tx hardware PDP Reflection from Tx 16

17 LoS with T-R height difference AGP CPU 4.3 cm Height difference in the order of few centimeters (> 10λ) will suffer from significant loss 17

18 Directed NLoS Front and Back surfaces of a DIMM (Dual Inline Memory Module) Front and Back surfaces of a graphic card 18

19 Path Loss (Directed NLoS) Front surface of DIMM Back surface of DIMM 19

20 Reflection Coefficient (Directed NLoS) Measured PL 20

21 OLoS Link through Parallel-Plate Structure 2.3 cm < w < 5.2 cm 21

22 NLOS- Through Heatsink 22

23 NLOS- Through Rotating Fan 23

24 Path Loss [db] Impact of Human Hand on THz Propagation Ground reflection (FR4) Ground reflection (Copper sheet) LoS FR4 Copper sheet Human hand Cardboard FSPL (d=55 cm) Ground reflection (Human hand) Frequency [GHz] 24

25 Path Loss [db] Impact of Human Hand on THz Propagation Hand angle LoS Perturbation by hand LoS Hand at 30 o angle Hand at 45 o angle FSPL (d=55 cm) Frequency [GHz] 25

26 2-D Geometrical Propagation Model [5] S. Kim and A. Zajić, Statistical modeling and simulation of short-range device-to-device communication channels at sub-thz frequencies, IEEE Transactions on Wireless Communications, vol. 15, no. 9, pp , Sept

27 LoS Ray ( p, q) S ( l, m) S AT T D θr AR 27

28 Single-Reflected Ray ( p, q) S ( l, m) S AT T ( l, m) T θr AR ( l, m) R 28

29 Double-Reflected Ray ( p, q) S ( l, m) S AT ( l, m) T D R ( p, q) AR 29

30 Distribution of Scatterers The joint PDF: 30

31 Correlation Function Transfer function is the FFT pair of the delay-spread function 31

32 Reference Model Validation LoS desktop scenario (300~320 GHz) : D = 30cm D = 40cm 32

33 Reference Model Validation Realistic desktop scenario with clutters (300~320 GHz) : D = 55cm 33

34 Reference Model Validation NLoS desktop scenario with cylindrical obstruction (110~170 GHz) : D = cm 34

35 Research Challenges Cost and energy efficient transceivers Antenna design for efficient communication over small distances Channel modeling at THz frequencies Low-complexity modulation and coding schemes Channel equalization over wide frequency bandwidth Medium access protocols suitable for ultra-dense networks 35

36 THANK YOU Questions? 36