Emerging Hardware Enablers for More Efficient Use of the Spectrum

Tunable and reconfigurable radio frequency (RF) technologies have the potential to aid a more efficient use of spectrum through increased bandwidth efficiency, increased flexibility in operating frequencies, more efficient spectrum authorization models, and more efficient spectrum sharing mechanisms. Spectrum sharing mechanisms are already deployed in some countries (e.g. television white-space), however a lack of low-cost tunable RF technologies for user equipment applications has contributed to slow adoption of the technology. To exploit the benefits of spectrum sharing, frequency agile transceivers are required in the low and mid frequency ranges (e.g. 600 MHz to 6 GHz), making tunable and reconfigurable RF technologies a key enabler for spectrum sharing in 5G. This paper reviews recent advances in tunable RF technologies in the context of spectrum use. This work covers power amplifiers, acoustic filters/duplexers, self-interference canceling duplexers, and receivers, discussing the subsystem performance requirements and potential benefits. Various technology challenges are identified at device, subsystem, and transceiver system level, and current research directions and progress are reviewed. Substantial progress is forthcoming in this field. The uptake of spectrum sharing technology is likely to accelerate, with the the development and deployment of 5G and IoT devices, however further work is required to address performance enhancements in RF front-ends through sub-system co-design in the next generation of devices.