Project ARIES
Our other focus is on a transmission technology that is a) spectrally efficient (total number of bits transmitted per unit of radio spectrum bps/Hz), allowing for higher throughput in even the smallest bandwidths, and b) energy efficient (total number of bits transmitted per unit Joule energy spent b/J), allowing for extended coverage range. Project ARIES are our proof-of-concept effort to build a test platform for incredibly efficient usage of spectrum and energy: A base station with 96 antennas, it can support 24 streams simultaneously over the same radio spectrum. We currently are able to demonstrate 71 bps/Hz of spectral efficiency, and when complete ARIES will demonstrate an unprecedented 100+ bps/Hz of spectral efficiency.
Today, 4G cellular and WLAN systems use a technology called MIMO — multiple inputs, multiple outputs. The progression toward 5G comes with Massive MIMO, an advanced wireless technology that uses a large number of antennas. ARIES is an embodiment of such a technology — by using the notion of “spatial multiplexing,” the antenna array at the base station can serve a multiplicity of autonomous user terminals on the same time-frequency resource. This spatial resource sharing policy serves as an alternative not only to the need for spectrum licensing but also the procurement of additional base stations in conventional cell-shrinking strategies. Massive MIMO systems with an excessively large number of antennas have recently gained attention, thanks to asymptotic results on random matrix theory that illustrate how the effects of uncorrelated noise and small-scale fading are virtually eliminated as the number of antennas in a MIMO cell grows large.
Massive MIMO systems are also versatile over a wide range of system parameters. For instance, the beamforming gain afforded by using a large number of transmit antennas may be used to overcome the large path loss associated with millimeter-wave links in urban areas. Alternatively, the beamforming gain may be harnessed at lower frequencies to provide wide-coverage connectivity to rural areas, and this is our focus. Given such promises, the practical and theoretical aspects of massive MIMO systems are being examined for potential beyond-4G wireless communications deployments by standardization entities such as the third generation partnership project (3GPP), and by many industrial base-station and device manufacturers worldwide.
