EURECOM – CAMPUS SOPHIATECH
450 route des Chappes F-06410 BIOT Sophia Antipolis www.eurecom.fr
• Measurement on ExpressMIMO2
2x1 and 4x1 MISO case using 2 ExpressMIMO2 cards synchronized by cables;
Measured results:
• Beamforming Gain
• Future work
Scale up the experiment to Massive MIMO case.
• OpenAirInterface (OAI)
Open-source hardware/software development platform and open-forum for innovation in the area of digital radio communications created by EURECOM [2].
• ExpressMIMO2
• Massive MIMO prototype
64 Antenna array supported by 16 ExpressMIMO2 cards
Centralized high end computing engine
• Massive MIMO key challenges
Acquisition of channel information at transmitter (CSIT);
Pilot contamination;
Fast and distributed coherent signal processing;
Hardware impairment, etc.
• Time Division Duplexing (TDD)
Use TDD channel reciprocity for massive MIMO to ease the acquisition of CSIT : no feedback needed;
However, hardware non-symmetry destroys the TDD reciprocity.
• Relative Calibration
Compensate the impairment by a multiplicative matrix;
Cost efficient: no additional hardware needed.
Exploiting Channel Reciprocity in Massive MIMO
Xiwen JIANG, Florian Kaltenberger, Raymond Knopp, Luc Deneire * Email: [email protected]
5G Wireless Networks
Massive MIMO Prototyping
Channel Reciprocity Exploitation
Figure 5: calibration matrix in 4x1 MISO
Figure 6: Beamforming performance based on different CSIT acquisition methods (4x1 MISO) Figure1: Key challenges for future radio access [1]
Figure 3: Massive MIMO prototype on OAI
• Key challenges for future radio access
Massive growth in traffic volume;
Massive growth in connected devices;
Wide range of requirements and characteristics for different services.
• Emerging technologies for 5G
MASSIVE MIMO: the focus of our work;
Heterogeneous network (HetNet);
Machine to Machine Communications (M2M);
Software Defined Network (SDN), etc.
Figure 2: ExpressMIMO2 card
Experimental Results
-2 -1.5 -1 -0.5 0 0.5 1 1.5 2
-2 -1.5 -1 -0.5 0 0.5 1 1.5 2
F0
-1.5 -1 -0.5 0 0.5 1 1.5
-1.5 -1 -0.5 0 0.5 1 1.5
Real
Imaginary
f33
f22
f44
f11
fij(i j)
Figure 4: calibration matrix in 2x1 MISO
Different CSIT acquisition methods: feedback mode, calibration matrix full
estimation, diagonal estimation (assume the off-diagonal
elements to be zero) and no calibration used.
Relative calibration fully achieves the channel
reciprocity.
References
[1] Ericsson, “5G radio access”, white paper.
[2] http://www.openairinterface.org/
Note *
Luc Deneire is a professor in Université de Nice Sophia Antipolis, Laboratoire I3S
OAI’s hardware platform interfacing with the
OpenAir4G modem
1.91 1.911 1.912 1.913 1.914 1.915
32 33 34 35 36 37 38 39 40
Frequency (GHZ)
Beamforming SNR (dB)
Feedback Identity Diagonal Full
