Large-Scale Antenna Systems (LSAS), widely known as massive MIMO, have recently emerged as a potential disruptive technology for fifth-generation (5G) wireless communications. On one hand, sub-6 GHz LSAS have taken the expected role of providing an umbrella of high-capacity and ubiquitous coverage. Indeed, massive MIMO systems enjoy many more spatial degrees of freedom (d.o.f.) than the number of user terminals to be served, hence making them resilient to the effects of uncorrelated noise and small-scale fading. This effectively enables them to provide large spectral-efficiency gains in fast-changing propagation environments. On the other hand, millimeter-wave (mmWave) LSAS will be deployed in conjunction with sub-6 GHz LSAS to augment the network capacity for short-range and low-mobility scenarios. This may prove extremely helpful in densely crowded environments such as shopping malls, airports, etc.
Due to the scarcity of available licensed spectrum, future LSAS are also envisioned to make extensive use of unlicensed frequency bands, now embraced as valuable assets for traffic offloading and/or throughput boost via aggregation. A tight integration of licensed and unlicensed spectrum however poses various challenges, and a fair coexistence between the new technologies and the ones already operating in the unlicensed band, e.g., IEEE 802.11x (WiFi), is still a concern. In this context, LSAS and their abundant spatial d.o.f. are foreseen to become a game changer.
Though some initial steps toward the implementation of LSAS have already been taken, there are still several key challenges that need to be tackled, before the benefits in terms of increased spectral efficiency, coexistence, and spatial reuse can be fulfilled. This new workshop will bring together academic and industrial experts to identify and discuss technical challenges and recent results related to the role of LSAS in improving spectral efficiency in both licensed and unlicensed bands.