Presentation given by PhD student Paul Harris from the Communication Systems & Networks Research Group at the University of Bristol at IEEE Globecom in Washington D.C., USA on 5th December 2016.

1. IEEE Globecom, WCS.10: Channel Measurements and Modeling
5th December 2016, Washington D.C.
LOS Throughput Measurements in Real-Time
with a 128-Antenna Massive MIMO Testbed
Paul Harris
Siming Zhang, Mark Beach, Evangelos Mellios, Andrew Nix, Simon Armour, Angela Doufexi, Karl Nieman, Nikhil Kundargi
Communication Systems and Networks Group
University of Bristol, Bristol, UK
http://www.bristol.ac.uk/engineering/research/csn/

2. IEEE Globecom, WCS.10: Channel Measurements and Modeling
5th December 2016, Washington D.C.
Summary
• System Overview
• Measurement Setup
• Experimental Results
• Conclusions
• Ongoing Work
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3. IEEE Globecom, WCS.10: Channel Measurements and Modeling
5th December 2016, Washington D.C.
The Massive MIMO Concept
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Ultimate Spatial
Resolution
• Increased spectral efficiency and network capacity
• Accurate spatial multiplexing
Time
Space
Uplink Downlink
Uplink
Uplink
Uplink
Downlink
Downlink
Downlink
Cellular View

4. IEEE Globecom, WCS.10: Channel Measurements and Modeling
5th December 2016, Washington D.C.
NI Based ‘BIO’ Massive MIMO test-bed
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• 128 Programmable Radio Heads (4
racks of 32 radios)
• ‘TD-LTE’ like PHY (20 MHz BW)
• 1.2 – 6.0GHz Carrier (3.51GHz used)
• Centralised MMSE, ZF and MRC/MRT
MIMO Processing
• Supports up to 12 User Clients (Full
FPGA Processing)
• 24 user clients (decimated processing)

5. IEEE Globecom, WCS.10: Channel Measurements and Modeling
5th December 2016, Washington D.C.
Functional Overview
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Distributed FPGA Processing with PCIe links Compact Computer

6. IEEE Globecom, WCS.10: Channel Measurements and Modeling
5th December 2016, Washington D.C.
Linear Decoding/Precoding
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• MGS Full QR
Decomposition
• Partial parallel systolic
array
• One detection matrix
per 12 subcarrier
resource block

7. IEEE Globecom, WCS.10: Channel Measurements and Modeling
5th December 2016, Washington D.C.
MIMO Processor
• Wide Data Path 128 x 12 Linear Detector
• Computes 128 x 12 by 128 x 1 matrix vector
multiply in 160 ns
• 24 Million times per second
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𝒚𝑾 𝑴𝑴𝑺𝑬
12 x 128
128 x 1
× = = 𝒖
12 x 1
32 x 1 (4)12 x 32 (4)
𝑾 𝑴𝑴𝑺𝑬 𝟎
𝑾 𝑴𝑴𝑺𝑬 𝟏
𝑾 𝑴𝑴𝑺𝑬 𝟐
𝑾 𝑴𝑴𝑺𝑬 𝟑
𝒚 𝟎
𝒚 𝟏
𝒚 𝟐
𝒚 𝟑

8. IEEE Globecom, WCS.10: Channel Measurements and Modeling
5th December 2016, Washington D.C.
Frame Schedule
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9. IEEE Globecom, WCS.10: Channel Measurements and Modeling
5th December 2016, Washington D.C.
Initial Indoor Deployment
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• 5.4m Linear Array with half-
wavelength spacing
• Client Separation 2.5 – 6 λ
• Equal and fixed UE Tx Gains
• “LOS” Conditions

10. IEEE Globecom, WCS.10: Channel Measurements and Modeling
5th December 2016, Washington D.C.
Initial Indoor Deployment
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11. IEEE Globecom, WCS.10: Channel Measurements and Modeling
5th December 2016, Washington D.C.
CDF Plots of SVS
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Scenario 1-3 in ascending order of LOS distance. 200ms capture interval for 3 minutes. Averaged across frequency.
Exploitation
of azimuth
spread Closest
scenario is
the worst for
32 elements

12. IEEE Globecom, WCS.10: Channel Measurements and Modeling
5th December 2016, Washington D.C.
𝑯𝑯 𝑯
for 12 users with scaled N
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Scenario 2 (12.5m Straight Line). 200ms capture interval for 3 minutes. Averaged across frequency and time.

13. IEEE Globecom, WCS.10: Channel Measurements and Modeling
5th December 2016, Washington D.C.
Real-Time Channel Information
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Eigen
Structure
Individual Spatial Stream Rx Magnitude
Power Delay profiles
Frequency Domain profiles
Fading over the
array caused by
stairwell

14. IEEE Globecom, WCS.10: Channel Measurements and Modeling
5th December 2016, Washington D.C.
12 Streams of 256-QAM
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15. IEEE Globecom, WCS.10: Channel Measurements and Modeling
5th December 2016, Washington D.C.
2nd Phase Deployment (11th May 2016)
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24.8m
3.51 GHz Patch Array
24 UEs
2.5λ spacing
Presented at SiPS 2016, Dallas.

16. IEEE Globecom, WCS.10: Channel Measurements and Modeling
5th December 2016, Washington D.C.
22 User Gram Matrix
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17. IEEE Globecom, WCS.10: Channel Measurements and Modeling
5th December 2016, Washington D.C.
22 Streams of 256-QAM
• With the same frame structure as before this equates
to 145.6 bits/s/Hz (uncoded sum rate of 2.915 Gbps)
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User
Inactive
User
Inactive
131 bits/s/Hz
144 bits/s/Hz
145.7 bits/s/Hz

18. IEEE Globecom, WCS.10: Channel Measurements and Modeling
5th December 2016, Washington D.C.
Conclusions
• Average ratio of composite channel gain to inter-user
correlation observed to be 10 dB or more for a ratio of up
to 6:1 basestation antennas to users
• Azimuth dominated array configurations could improve
close range LOS performance
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19. IEEE Globecom, WCS.10: Channel Measurements and Modeling
5th December 2016, Washington D.C.
Ongoing Work
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20. IEEE Globecom, WCS.10: Channel Measurements and Modeling
5th December 2016, Washington D.C.
Acknowledgements and Thanks to…
• Post Graduate Students: Wael Boukley Hasan, Siming Zhang, Henry
Brice & Benny Chitambira
• Academic Colleagues & post graduates at Lund University: Steffen
Malkowsky, Joao Vieira, Liang Liu, Ove Edfurs & Fredrik Tufvesson
• Academic Colleagues at Bristol: Mark Beach, Andrew Nix, Evangelos
Mellios, Angela Doufexi and Simon Armour
• NI Staff: Karl Nieman, Nikhil Kundargi, Ian Wong, Leif Johansson &
James Kimery
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21. IEEE Globecom, WCS.10: Channel Measurements and Modeling
5th December 2016, Washington D.C.
Thank You
Any questions?
Communication Systems and Networks Group
University of Bristol, Bristol, UK
http://www.bristol.ac.uk/engineering/research/csn/