RINGS: Massive Extended-Array Transceivers for Robust Scaling of All-Digital mmWave MIMO

University Of California-Santa Barbara, Santa Barbara CA

Investigators

Abstract

As the demand for high-speed wireless data keeps growing, it is essential to access the vast amounts of spectrum available in “millimeter wave (mmWave)” frequency bands, which are orders of magnitude higher than the frequency bands used in WiFi and cellular systems today. There has been substantial recent progress demonstrating feasibility of radio frequency integrated circuits (RFICs) built with low-cost silicon semiconductor processes, for lower mmWave frequency bands such as 28 GHz licensed spectrum (for 5G cellular), and 60 GHz unlicensed spectrum (for next-generation WiFi). This project aims to provide a quantum leap beyond these efforts, developing strategically important and commercially viable technologies for opening up upper mmWave bands beyond 100 GHz. A specific goal is to develop antenna arrays with thousands of elements, capable of forming agile pencil beams tracking mobile devices, which can be miniaturized into compact form factors because of the tiny wavelengths at 100+ GHz. The project investigates novel approaches for co-design of hardware and algorithms for scaling array sizes, targeting significant jumps in attainable link distances and data rates (10 Gbps per mobile user in an urban cell, and 100 Gbps for a fixed wireless alternative to fiber). Millimeter wave (mmWave) communication will play a crucial role in next-generation communication infrastructures. A fundamental bottleneck in mmWave hardware development is packaging: “fitting” the RFIC electronics becomes difficult at small carrier wavelengths due to the standard constraint of half-wavelength spacing between antennas. This project investigates novel hardware architectures that sidestep such packaging bottlenecks to realize massive extended arrays, along with closely coupled innovations in all-digital hierarchical signal processing architectures, targeting quantum leaps in capacity and resilience. Hardware research includes development of extremely low-cost 140GHz transceiver modular array tile technologies that readily scale to arrays having vast numbers of elements. Signal processing and systems research develops all-digital hierarchical signal processing architectures matched to the tiled hardware architecture, illustrating the system-level impact of the robustness and additional spatial degrees of freedom provided by extended arrays in canonical multiuser (MU) MIMO and Line of Sight (LoS) MIMO settings aimed at flexible, cost-effective deployment of access and backhaul nodes. A key design concept is spatial redundancy: by choosing hardware and system parameters such that the number of array RF channels greatly exceeds the number of MIMO signals involved, it becomes possible to simplify power consumption and die area by sacrificing dynamic range. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.