Spectrum scarcity has driven enhancements of Long-Term Evolution (LTE) in utilizing unlicensed bands in conjunction with licensed bands for delivering mobile data, resulting in the introduction of LTE unlicensed technologies such as Rel-13 LTE–Licensed-Assisted Access (LAA), Rel-14 LTE–Enhanced Licensed-Assisted Access (eLAA), and LTE-Unlicensed (LTE-U). The next-generation radio access technology, 5G New Radio(NR), faces greater technical challenge due to the need to support frequency bands covering various spectrum licensing regimes and a wide range of frequencies (up to 100 GHz) with very different signal propagation characteristics. This paper presents an overview of LAA and eLAA technical features and 5G NR design considerations to achieve a unified access in licensed and unlicensed bands.
