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The role antennas play in a MIMO link

Dr Andre FourieCEO, Poynting Antennas

Overview

Where is MIMO used: Wi-Fi, WIMAX, LTE

SDMA – spacial division multiplexing (multiple access?)

Antennas – radiation pattern, polarisation

Channels – indoor vs outdoor

Radiation patterns

• Transmission interpretation

• Reception interpretation

Polarisation

• Defined in terms of electric field

• Often referenced to the earth

• Linear

• Circular

• Elliptical

• Cross pol gain

Channels

• Channel includes: Transmit antenna – path – receive antenna

• Free space example

Channel – single reflection

Channel – multiple reflections

Channel - Indoor vs outdoor

Channel – indoor vs outdoor

• Assume BER of 1E-4

• Then– Outdoor SNR = 8dB– Indoor SNR = 34 dB

• Thus indoor signal must be 400 times stronger (26 dB) for similar performance

MIMO

• Multiple input multiple output

• SDMA is a technique which attempts to send multiple streams of data over a link using the same frequency resource

• SDMA is more multiplexing than multiple access

MIMO – a contrived example

MIMO – using cross-pol antennas

MIMO – how it works

MIMO – how it works

MIMO – how it works

MIMO – estimating the channel

MIMO – estimating the channel

MIMO – estimating the channel

MIMO – estimating the channel

Poor signal de-correlation

Poor signal de-correlation

Testing MIMO

Testing MIMO

Testing MIMO

Assessing antenna quality

• Good de-correlation required? Let’s test…

Assessing antenna quality

• Download speedup vs de-correlation

Conclusion

• External antenna make a big difference even for non-MIMO technologies

• Well de-correlated external antennas are important for good MIMO performance