Co-located and distributed antenna systems: deployment options for massive multiple-input–multiple-output

To evaluate the benefits of distributed arrays in massive multiple-input-multiple-output systems, the authors investigate the interaction between linear receivers (maximum ratio combining and zero forcing) and three deployments scenarios: (i) a massive co-located array at the cell centre; (ii) a massive array clustered at B discrete locations; and (iii) a massive distributed array with a uniform distribution of individual antennas. The authors also study the effect of propagation parameters, system size, correlation and channel estimation error. The authors demonstrate by analysis and simulation that in the absence of any system imperfections, a massive distributed array is preferable. An intermediate deployment such as a massive array clustered at a few discrete locations, can be more practical to implement and more robust to imperfect channel state information. The authors show an example with a 128 antenna deployment where four locations achieves one third of the gains due to a fully distributed array.