Uppsala universitet

Predictor Antennas in Action

Joachim Björsell , Uppsala University,
Mikael Sternad , Uppsala University, and
Michael Grieger , AIRRAYS - Wireless Solutions, Dresden, Germany

2017 IEEE 28th Annual International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC) , Montreal, October 2017.

Paper In Pdf

Presentation slides

Connected vehicles in large numbers will be expensive in terms of power and bandwidth unless advanced transmit schemes are employed. These would rely on channel state information at transmitter (CSIT), which rapidly becomes outdated for fading vehicular channels.

We here evaluate the predictor antenna concept, that solves this problem by using antennas on the outside of vehicles, with one extra antenna in front of the others. Its estimated channel is a scaled prediction for the channels encountered by rearward antennas when they reach that position.

We evaluate this concept on a large set of channel sounding measurements from an urban environment. Recent investigations of the correlations of these measurements indicate that the average normalized mean squared errors (NMSEs) of the complex valued channel predictions should be around -10 dB for prediction horizons in space of up to 3 wavelengths.

This represents an extension of the attainable prediction horizon by an order of magnitude, as compared to Kalman or Wiener extrapolation of past channel measurements. It represents an accuracy that would enable e.g. accurate massive multiple input multiple output (MIMO) downlink beamforming to vehicles.

We here perform predictions on a subset of the measurements with good channel-to-estimation error power ratio (SNR). The approximate true channels are here available and we evaluate the performance on a validation data set. The results confirm that the distribution of the NMSE, over all investigated propagation environments, is close to that obtained by correlation-based models and outperforms the use of outdated channel measurements.

Related publications:

Companion paper at IEEE ICC 2017 that provides the statistical estimate of the prediction accuracy.

Paper at IEEE WCNC 2012, Original proposal for using "Predictor antennas" for long-range prediction of fast fading for moving relays.

WSA 2018 paper verifying with measurements that predictor antennas enable precise precoding for massive MIMO antennas in non-line-of sigth.

Conference paper at EUCAP 2014 presenting compensation of antenna coupling.

IEEE Intelligent Transportation Systems Magazine 2015: Making 5G adaptive antennas work for very fast moving vehicles.

Paper at Globecom 2016 5G Workshop on the gain by predictor antennas in terms of spectral efficiency and power efficiency when serving connected vehicles by 5G Massive MIMO antennas.

Channel estimation and prediction for 5G applications.
PhD Thesis by Rikke Apelfröjd, Uppsala University 2018

Channel Estimation and Prediction for MIMO OFDM Systems.
PhD Thesis by Danel Aronsson, Uppsala University 2011.

Prediction of Mobile Radio Channels.
PhD Thesis by Torbjörn Ekman, Uppsala University 2002.

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