At the beginning of the projet
The MHESTIA project started a few years after the M-MIMO paradigm emerged . From 2010 to 2015, a huge amount of studies regarding M-MIMO have been led by the scientific community , advocating for M-MIMO as a promising solution for future cellular networks. Most of these works were however based on theoretical system and channel models. In the meantime, the exploitation of frequency bands above 6 GHz for communication, and especially around 60 GHz, was seriously envisaged, the numerous drawbacks according to the ability to harness such mmWaves becoming less dominant than the urgent need for large bandwidth as promised at such frequencies . On this basis, many of the industrial visions exposed between 2010 and 2015 were integrating mmWaves and M-MIMO as a win–win combination to consider among other key enablers for 5G.
 T. L. Marzetta, “Noncooperative Cellular Wireless with Unlimited Numbers of Base Station Antennas,” in IEEE Transactions on Wireless Communications, vol. 9, no. 11, pp. 3590-3600, November 2010.
 F. Rusek et al., “Scaling Up MIMO: Opportunities and Challenges with Very Large Arrays,” in IEEE Signal Processing Magazine, vol. 30, no. 1, pp. 40-60, Jan. 2013.
 T. S. Rappaport et al., “Millimeter Wave Mobile Communications for 5G Cellular: It Will Work!,” in IEEE Access, vol. 1, pp. 335-349, 2013.
One first clear fact is that the sparsity of the propagation channels in mmWaves has been widely confirmed from 2015, according to the numerous litterature works and the ones led within WP3.
During the last years also, hybrid beamforming concepts has also progressively become a credible solution to accommodate with the complexity of multiuser beamforming in mmWaves . As a major example towards such system design, the last releases of the 3GPP LTE have introduced the concept of virtual MIMO structures grouping multiple radiating elements to form one single digital spatial port.
On one other hand, spatial modulations have also been recently considered as an efficient option to deal with the complexity issues related to the use of multiple RF chains at mmWave frequencies .
In the MHESTIA project, we have provided theoretical analyses and new algorithms taking into account the last pieces of knowledge in terms of channel models at mmWaves, hybrid beamforming strategies and spatial modulation, in the perspective of practical implementation designs.
 A. F. Molisch et al., “Hybrid Beamforming for Massive MIMO: A Survey,” in IEEE Communications Magazine, vol. 55, no. 9, pp. 134-141, Sept. 2017.
 T. Lakshmi Narasimhan, P. Raviteja and A. Chockalingam, “Generalized Spatial Modulation in Large-Scale Multiuser MIMO Systems,” in IEEE Transactions on Wireless Communications, vol. 14, no. 7, pp. 3764-3779, July 2015.