**Authors:** Per-Simon Kildal

**Source:** FERMAT, Volume 14, Communications 7, Mar Apr., 2016

**Abstract:**• In this invited presentation I describe how we prepare for 5G in my research division. The
background is that we have contributed to 3G and 4G developments with two commercial successes:
the hat-fed reflector antenna for backhaul radio links, and Bluetest reverberation chambers for OTA
(Oer-The-Air) characterization of devices with MIMO and OFDM.
• 5G means Gbit/s data rates, for which higher frequencies are needed towards the user terminal, may
be up to 30 or 60 GHz. This means that the multipath will be weaker as it gradually diminishes when
frequency increases. Therefore, we prepare by introducing a Random-LOS (RLOS) complement to
the OTA testing in Rich Isotropic Multipath (RIMP) being provided by Bluetest’s reverberation
chambers.
• Further, high gain steerable beams will be needed, requiring new planar packaging solutions for
closer integration of antennas and RF chipsets. Therefore, we prepare by research on gap
waveguides. Massive MIMO have many technological uncertainties, so others also consider oldfashioned phased arrays, but they will not work in RIMP.
• The best hardware can only be chosen if we know how to characterize the system performance. The
radiation pattern and realized gain cannot be used directly for this purpose due to all the statistical
variations caused by the arbitrariness of the user. Therefore, we introduce instead the Probability of
Detection (PoD) as a quality metric. This will be different for each desired number of bitstreams.
Further, we quantify the difference between different PoD curves in dBiid in RIMP, i.e. in dB
relative to the i.i.d. (independent identically distributed) case, and in dBt in RLOS, i.e. in dB relative
to an ideal polarization- and coverage-matched threshold receiver.
• The presentation will give an overview of this research.

**Keywords:** 5G, Massive MIMO, Antenna design, gap waveguides, RIMP, Random-LOS

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