3GPP Spectrum Access Evolution Towards 5G

The ever-increasing needs for more spectrum resources, and the emerging new Radio Access Technologies under the 5G umbrella add to the complexity of the Spectrum Toolbox in mobile networks landscape. This article covers 3GPP LTE evolution from Release 8 up to the Release 14, which deals with the LTE-Advanced Pro enhancements. A collection of available frequency bands, spectrum aggregation mechanisms, licensing and duplexing schemes, as well as spectrum sharing and refarming techniques is described. With such a classification, Spectrum Toolbox is defined and its evolution directions are discussed, with the opportunities and challenges of the individual features summarized. Studies on the new non-backwards compatible Radio Access Technology, as well as the new channel models for higher frequency bands are also covered. The presented Spectrum Toolbox is considered as a baseline for the introduction of the new air interface framework towards 5G ecosystem in the context of future mobile networks enhancements.