Spatial separation of closely-spaced users in measured massive multi-user MIMO channels

Fully-synchronous measurements of a massive multi-user multiple-input multiple-output (MU-MIMO) radio propagation channel are presented. We evaluate the ability of a massive MIMO system to spatially separate users located close to each other in line-of-sight (LOS) propagation conditions. The system consists of a base-station (BS) antenna array equipped with 64 dual-polarized antenna elements (128 ports) arranged in a cylindrical configuration, and eight single-antenna users. The users are confined to a five-meter diameter circle and move randomly at pedestrian speeds. The BS antenna array is located on top of a 20 m tall building and has LOS to the users. We examine user separability by studying singular value spread of the MU-MIMO channel matrix for several subsets of BS antenna array ports, along with sum-rate capacity and achievable sum-rates with both zero-forcing and matched-filtering linear precoders. We also analyze the performance of the user with the lowest rate. Finally, a comparison between the performance offered by the massive MIMO system and that of a conventional MU-MIMO system is provided. To the best of our knowledge, this is the first report of fully-synchronous dynamic measurements of a massive MIMO system. Our investigation shows that even users located close to each other in LOS propagation conditions can be spatially separated in a massive MIMO system.

[1]  Andrea J. Goldsmith,et al.  Duality, achievable rates, and sum-rate capacity of Gaussian MIMO broadcast channels , 2003, IEEE Trans. Inf. Theory.

[2]  Fredrik Tufvesson,et al.  Measured propagation characteristics for very-large MIMO at 2.6 GHz , 2012, 2012 Conference Record of the Forty Sixth Asilomar Conference on Signals, Systems and Computers (ASILOMAR).

[3]  Max H. M. Costa,et al.  Writing on dirty paper , 1983, IEEE Trans. Inf. Theory.

[4]  A. Goldsmith,et al.  Sum power iterative water-filling for multi-antenna Gaussian broadcast channels , 2002, Conference Record of the Thirty-Sixth Asilomar Conference on Signals, Systems and Computers, 2002..

[5]  Jeffrey G. Andrews,et al.  What Will 5G Be? , 2014, IEEE Journal on Selected Areas in Communications.

[6]  F. Tufvesson,et al.  Channel measurements and analysis for very large array systems at 2.6 GHz , 2012, 2012 6th European Conference on Antennas and Propagation (EUCAP).

[7]  Robert W. Heath,et al.  Five disruptive technology directions for 5G , 2013, IEEE Communications Magazine.

[8]  Thomas L. Marzetta,et al.  Noncooperative Cellular Wireless with Unlimited Numbers of Base Station Antennas , 2010, IEEE Transactions on Wireless Communications.

[9]  Taoka Hidekazu,et al.  Scenarios for 5G mobile and wireless communications: the vision of the METIS project , 2014, IEEE Communications Magazine.

[10]  Emre Telatar,et al.  Capacity of Multi-antenna Gaussian Channels , 1999, Eur. Trans. Telecommun..

[11]  Stephan ten Brink,et al.  Channel measurements for large antenna arrays , 2012, 2012 International Symposium on Wireless Communication Systems (ISWCS).

[12]  Erik G. Larsson,et al.  Scaling Up MIMO: Opportunities and Challenges with Very Large Arrays , 2012, IEEE Signal Process. Mag..

[13]  Fredrik Tufvesson,et al.  Linear Pre-Coding Performance in Measured Very-Large MIMO Channels , 2011, 2011 IEEE Vehicular Technology Conference (VTC Fall).

[14]  Erik G. Larsson,et al.  Massive MIMO for next generation wireless systems , 2013, IEEE Communications Magazine.

[15]  Gerd Sommerkorn,et al.  Identification of time-variant directional mobile radio channels , 2000, IEEE Trans. Instrum. Meas..

[16]  Rohit U. Nabar,et al.  Introduction to Space-Time Wireless Communications , 2003 .

[17]  Fredrik Tufvesson,et al.  Massive MIMO in real propagation environments , 2014, ArXiv.

[18]  Erik G. Larsson,et al.  Energy and Spectral Efficiency of Very Large Multiuser MIMO Systems , 2011, IEEE Transactions on Communications.