Uppsala universitet

Measurement-Based Evaluation of Robust Linear Precoding for Downlink CoMP.

Rikke Apelfröjd , Mikael Sternad and Daniel Aronsson , Uppsala University.

IEEE Conference on Communications(ICC), Ottawa, Canada June 2012, pp 5749-5755.

We study the design and evaluation of joint processing coordinated multipoint (CoMP) downlink transmission. Precoders will then be designed based on outdated channel state information (CSI), so interference cannot be eliminated completely as by an ideal zero-forcing (ZF) solution.

We here strive to design and evaluate realistic linear transmit schemes. Kalman predictors are used for orthogonal frequency-division multiplexing (OFDM) channels. They provide optimal linear predictions and also estimates of their uncertainty. Robust linear precoders are designed based on these uncertainty estimates. We introduce and use robust linear quadratic optimal feedforward control, with the criterion averaged (marginalized) over the CSI uncertainty. This flexible solution performs minimum mean square error (MSE) minimization. It can also iteratively optimize other criteria, such as sum-rate.

The prediction- and transmission performance is evaluated using measured data on 20 MHz OFDM downlinks from three base stations, for users at fast pedestrian velocities. Downlink CoMP is here also compared to cellular transmission, that uses orthogonal resources within cells but allows uncontrolled interference between cells.

Related publications:
Licentiate thesis by Rikke Apelfröjd, May 2014
(of which this is the first contribution paper).

PhD Thesis by Rikke Apelfröjd, April 2018.

EURASIP JWCN paper 2014 that significantly improves on these results by combining them with a simple and appropriate user grouping strategy.

Performance Evaluation of Coordinated Multi-Point Transmission Schemes with Predicted CSI (IEEE PIMRC 2012).

Report by Rikke Apelfröjd on Kalman prediction for multipoint OFDM downlink channels, May 2014, revised March 2018.

Channel Estimation and Prediction for MIMO OFDM Systems: Key design and performance aspects of Kalman-based algorithms.
PhD Thesis by Daniel Aronsson, 2012.

Eusipco 2007, focusing on comparing the use of overlapping versus dedicated uplink pilots.

IEEE VTC-2003-Fall: Channel estimation and prediction for adaptive OFDM downlinks.

Prediction of mobile radio channels, Ph.D. Thesis by Torbjörn Ekman 2002.

Proceedings of the IEEE paper (2007) giving overview of adaptive transmission in OFDMA systems.

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