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Match 2015 doc.: 15-15-0207-00-003d Stochastic Channel Model for Wireless Data Center
Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)
Submission Title:
The THz Channel Model in Wireless Data Center
Date Submitted:
10 Match 2015
Source:
Bile Peng Company TU Braunschweig Address Schleinitzstr. 22, D-38102 Braunschweig, Germany Voice:+495313912405, FAX: +495313915192, E-Mail: [email protected]
Re:
n/a
Abstract:
This contribution presents some preliminary THz channel modeling results in the future wireless data center scenario. A series of ray tracing simulations are conducted for different channel types. The RMS delay spread and the RMS angular spread are employed as the metric of the multipath richness. A stochastic channel model is developed based on the simulation results and is validated by the ray tracing simulation results.
Purpose:
Contribution towards developing a wireless data center channel model for use in TG 3d
Notice:
This document has been prepared to assist the IEEE P802.15. 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 P802.15.
Submission Slide 1 Bile Peng (TU Braunschweig).
Match 2015 doc.: 15-15-0207-00-003d Stochastic Channel Model for Wireless Data Center
Submission
A Stochastic THz Channel Model in Wireless Data Centers Bile Peng , Thomas Kürner TU Braunschweig
Slide 2 Bile Peng (TU Braunschweig)
Match 2015 doc.: 15-15-0207-00-003d Stochastic Channel Model for Wireless Data Center
Contents
• • • •
Motivation
Ray Tracing Simulation Results Stochastic Channel Model Conclusion Submission Slide 3 Bile Peng (TU Braunschweig)
Match 2015 doc.: 15-15-0207-00-003d Stochastic Channel Model for Wireless Data Center
Motivation
The data center link is responsible for the cooperation between computers and must achieve very high data rates.
The data center link is prevailingly wired. However, the wireless link has some significant advantages [1]: More flexibility Less maintenance cost More space for cooling The high data rates of Terahertz (THz) communications makes it a competitive candidate.
This report is a preliminary PHY layer feasibility study of the application of the THz communication in the data center wireless backhaul.
Submission Slide 4 Bile Peng (TU Braunschweig)
Match 2015 doc.: 15-15-0207-00-003d Stochastic Channel Model for Wireless Data Center
Radio Wave Propagation Paths [2,3]
Ceiling Type 1: LoS Type 2: NLoS Type 3: Adjacent casings Submission Slide 5 Bile Peng (TU Braunschweig)
Match 2015 doc.: 15-15-0207-00-003d Stochastic Channel Model for Wireless Data Center
Selection of Propagation Path Type (1/2)
If transmitter and receiver are on the same or adjacent casings, they can be positioned lower than the casing roof to reduce the interference.
Submission Slide 6 Bile Peng (TU Braunschweig)
Match 2015 doc.: 15-15-0207-00-003d Stochastic Channel Model for Wireless Data Center
Selection of Propagation Path Type (2/2)
If transmitter and receiver are close enough, we use the NLoS path with reflection on the ceiling.
The short distance compensates for the reflection loss.
The AoD/AoA elevations are far from the horizonal direction, which reduces the interference on the LoS paths.
Criterion: the elevation ( θ) is at least 2 times Half-Power-Beamwith away from the horizontal direction. Otherwise we select the LoS path.
θ 1 θ 2 Ceiling Submission Slide 7 Bile Peng (TU Braunschweig)
Match 2015 doc.: 15-15-0207-00-003d Stochastic Channel Model for Wireless Data Center
Simulation Environment
Transmitter Receiver Casing Typical data center (source: http://www.enterprisetech.com/wp content/uploads/2014/11/SIO_DataCenter_Rows1.jpg) Wall Ray tracing simulation Submission Slide 8 Propagation path Bile Peng (TU Braunschweig)
Match 2015 doc.: 15-15-0207-00-003d Stochastic Channel Model for Wireless Data Center
Contents
• • • • Motivation
Ray Tracing Simulation Results
Stochastic Channel Model Conclusion Submission Slide 9 Bile Peng (TU Braunschweig)
Match 2015 doc.: 15-15-0207-00-003d Stochastic Channel Model for Wireless Data Center
Statistical Characteristics With Type 1/2
• • • Type1/2: LoS/nLoS channels between 2 nonadjacent casings Multipath richness metric: RMS delay spread with omniantenna Parity pattern due to reflections on the casing roof RMS delay spread RMS delay spread 10 2 Tx 2 8 4 4 6 Tx 6 6 4 8 8 2 10 5 10 server in x 15 ns 0 10 5 10 server in x 15 10 8 2 ns 0 6 4 Submission Slide 10 Bile Peng (TU Braunschweig)
Match 2015 doc.: 15-15-0207-00-003d Stochastic Channel Model for Wireless Data Center
Impact of Directive Antenna
RMS delay spread RMS delay spread 10 2 8 2 4 6 4 6 4 6 8 2 8 10 5 10 server in x 15 ns 0 10 5 10 server in x 15 • • Omniantenna Directive phased array Antenna: 4x4 phased array The directive antenna reduces the RMS delay spread significantly.
10 8 6 4 2 ns 0 Submission Slide 11 Bile Peng (TU Braunschweig)
Match 2015 doc.: 15-15-0207-00-003d Stochastic Channel Model for Wireless Data Center
Statistical Characteristics With Type 1/2
• • • Type1/2: LoS/nLoS channels between 2 nonadjacent casings Multipath richness metric: RMS angular spread with omniantenna Parity pattern due to reflections on the casing roof RMS angular spread RMS angular spread 60 Tx 2 50 2 40 4 4 Tx 30 6 6 20 8 8 10 10 0 10 5 10 server in x 15 5 10 server in x 15 60 50 40 30 20 10 0 Submission Slide 12 Bile Peng (TU Braunschweig)
Match 2015 doc.: 15-15-0207-00-003d Stochastic Channel Model for Wireless Data Center
8 10 2 4 6
Impact of Directive Antenna
RMS angular spread RMS AoD elevation spread 60 50 40 30 20 10 0 5 10 server in x 15 8 10 2 4 6 5 10 server in x 15 60 50 40 30 20 10 0 • • Omniantenna Directive phased array Antenna: 4x4 phased array The directive antenna reduces the RMS angular spread significantly as well.
Submission Slide 13 Bile Peng (TU Braunschweig)
Match 2015 doc.: 15-15-0207-00-003d Stochastic Channel Model for Wireless Data Center
Statistical Characteristics With Type 3
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0 0 • • • Type 3: channels between 2 adjacent casings Randomly generated adjacent Tx and Rx The RMS delay spread is lower than the in type 1/2 because of the limited propagation space.
1 Submission 1 2 3 4 RMS delay spread (ns) Omniantenna 5 6 Slide 14 0.8
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Bile Peng (TU Braunschweig)
Match 2015 doc.: 15-15-0207-00-003d Stochastic Channel Model for Wireless Data Center
Statistical Characteristics With Type 3
• • • Type 3: channels between 2 adjacent casings Randomly generated adjacent Tx and Rx The RMS angular spread is lower than the in type 1/2 because of the limited propagation space.
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0 0 10 20 30 RMS angle spread 40 Slide 15 50 Bile Peng (TU Braunschweig)
Match 2015 doc.: 15-15-0207-00-003d Stochastic Channel Model for Wireless Data Center
Contents
• • • • Motivation Ray Tracing Simulation Results
Stochastic Channel Model
Conclusion Submission Slide 16 Bile Peng (TU Braunschweig)
Match 2015 doc.: 15-15-0207-00-003d Stochastic Channel Model for Wireless Data Center
Stochastic Channel Model
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Determine number of paths.
Determine delay for each path.
Determine pathloss according to delay.
Determine angles.
Generate uniformly distributed phases.
Generate frequency dispersions (Friis law).
Generate polarisations.
Submission Slide 17 Bile Peng (TU Braunschweig)
Match 2015 doc.: 15-15-0207-00-003d Stochastic Channel Model for Wireless Data Center
Numbers of Paths
Type 1/2, Tx 1 (in corner) Number of paths Probability Number of paths Probability (%) LoS 1 100% 17 27 Reflections 18 35 19 22 20 15 21 1 Submission Slide 18 Bile Peng (TU Braunschweig)
Match 2015 doc.: 15-15-0207-00-003d Stochastic Channel Model for Wireless Data Center
Numbers of Paths
Type 1/2, Tx 2 (in center) Number of paths Probability Number of paths Probability (%) LoS 1 100% 16 32 17 29 Reflections 18 12 19 16 20 8 21 3 Submission Slide 19 Bile Peng (TU Braunschweig)
Match 2015 doc.: 15-15-0207-00-003d Stochastic Channel Model for Wireless Data Center
Numbers of Paths
Type 3 (Adjacent casings) Number of paths Probability Number of paths Probability (%) LoS 1 100% 3 22 4 13 Reflections 5 6 8 15 7 8 8 17 9 8 10 6 11 3 Submission Slide 20 Bile Peng (TU Braunschweig)
Match 2015 doc.: 15-15-0207-00-003d Stochastic Channel Model for Wireless Data Center
Delay Distribution: type 1/2, Tx 1
Path
LOS NLOS Submission 0.2
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0 0 LOS 20 40 Delay (ns) Reflection 0.4
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0 0 50 Relative delay (ns) 100
Distribution
Normal distribution Negative EXP Slide 21
Parameters
µ=2.26e-8, σ=8.76e-9 λ=4.26e7
Bile Peng (TU Braunschweig)
Match 2015 doc.: 15-15-0207-00-003d Stochastic Channel Model for Wireless Data Center
Delay Distribution: type 1/2, Tx 2
Path
LOS NLOS Submission LOS Reflection 0.2
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0 0 10 20 Delay (ns) 30 0 0 50 Relative delay (ns) 100
Distribution
Normal distribution Normal distribution Slide 22
Parameters
µ=1.20e-8, σ=4.56e-9 µ=2.98e-8, σ=1.79e-8 Bile Peng (TU Braunschweig)
Match 2015 Path
LOS NLOS Submission
doc.: 15-15-0207-00-003d Stochastic Channel Model for Wireless Data Center
Delay Distribution: type 3
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0 0 2 4 Delay (ns) Reflection 0.35
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0 0 50 Relative delay (ns) 100
Distribution
Normal distribution Negative EXP Slide 23
Parameters
µ=1.80e-8, σ=8.60e-9 λ=4.92e7
Bile Peng (TU Braunschweig)
Match 2015 doc.: 15-15-0207-00-003d Stochastic Channel Model for Wireless Data Center
Delay-Pathloss Correlation: type 1/2, Tx 1
Path
LOS NLOS Submission
Deterministic part
p=-20log 10 (d)-71.52
p r =-0.294d
r -17.44
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Random part (Norm.)
σ=0 σ=4 Bile Peng (TU Braunschweig)
Match 2015 doc.: 15-15-0207-00-003d Stochastic Channel Model for Wireless Data Center
Delay-Pathloss Correlation: type 1/2, Tx 2
Path
LOS NLOS Submission
Deterministic part
p=-20log 10 (d)-71.52
p r =-0.385d
r -17.95
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Random part (Norm.)
σ=0 σ=4 Bile Peng (TU Braunschweig)
Match 2015 doc.: 15-15-0207-00-003d Stochastic Channel Model for Wireless Data Center
Delay-Pathloss Correlation: type 3
Path
LOS NLOS Submission
Deterministic part
p=-20log 10 (d)-71.52
p r =-0.429d
r -30.3
Slide 26
Random part (Norm.)
σ=0 σ=6 Bile Peng (TU Braunschweig)
Match 2015 doc.: 15-15-0207-00-003d Stochastic Channel Model for Wireless Data Center
Pathloss-Angle Correlation
• • Since we want to reduce the multipath effect by highly directive antenna, the propagation paths with low pathloss and similar Angle of Arroval (AoA) to LOS path has a negative impact on the system design.
There is no appropriate distribution to describe the relation, therefore we use the correlation matrix.
180 160 140 120 100 80 60 40 20 0 -70 -60 -50 -40 -30 -20 Relative Pathloss (dB) -10 0 0.45
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Submission Slide 27 Bile Peng (TU Braunschweig)
Match 2015 doc.: 15-15-0207-00-003d Stochastic Channel Model for Wireless Data Center
Stochastic Channel Example
-90 -100 LoS path -110 -120 -130 -140 -150 -160 -170 -180 0 0.5
1 Time (s) 1.5
x 10 -8 2 Channel impulse response Submission Slide 28 180 160 140 120 100 80 60 40 20 0 -160 -150 -140 -130 Pathloss (dB) -120 LoS path -110 -100 Pathloss-angle distribution Bile Peng (TU Braunschweig)
Match 2015 doc.: 15-15-0207-00-003d Stochastic Channel Model for Wireless Data Center
Validation via RMS Delay Spread
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0 0 2 4 6 8 RMS delay spread (ns) 10 12 0.5
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0 0 2 4 6 8 RMS delay spread (ns) 10 12 Ray Tracing simulation Submission Slide 29 Stochastic channel model Bile Peng (TU Braunschweig)
Match 2015 doc.: 15-15-0207-00-003d Stochastic Channel Model for Wireless Data Center
Validation via RMS Angular Spread
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0 0 10 20 30 40 50 RMS angle spread (ns) 60 Ray Tracing simulation 70 80 0.4
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0 0 10 20 30 40 50 RMS angle spread (ns) 60 70 80 Stochastic channel model • The similar distribution of RMS delay/angle spreads validate the stochastical model.
Submission Slide 30 Bile Peng (TU Braunschweig)
Match 2015 doc.: 15-15-0207-00-003d Stochastic Channel Model for Wireless Data Center
Contents
• • • • Motivation Ray Tracing Simulation Results Stochastic Channel Model
Conclusion
Submission Slide 31 Bile Peng (TU Braunschweig)
Match 2015 doc.: 15-15-0207-00-003d Stochastic Channel Model for Wireless Data Center
Conclusion
• The THz communication is a competitive solution for the next generation wireless data center.
• A ray tracing simulation environment is set up to investigate the channel characteristics.
• The multipath propagation is a major hurdle of the high speed error free data transmission and the RMS delay/angular spread is used as metric of the multipath richness.
• A stochastic channel model is developed according to the ray tracing simulation results.
Submission Slide 32 Bile Peng (TU Braunschweig)
Match 2015 doc.: 15-15-0207-00-003d Stochastic Channel Model for Wireless Data Center
List of References
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T. Kürner, “Literature review on requirements for wireless data centers” doc.: IEEE 802.15-13-0411-00-0thz_Literature Review Zhang W et. al, „3D beamforming for wireless data centers”, in Proceedings of the 10th ACM Workshop on Hot Topics in Networks. 2011 K. Ramchadran„60 GHz Data-Center Networking: Wireless Worry less?“, 2008 Submission Slide 33 Bile Peng (TU Braunschweig)