As major industry players race to be the first ones to debut pre-standard versions of 5G, the current emphasis is on the millimeter-wave spectrum. The idea is to have 5G NR (typically millimeter wave) infrastructure provide additional capacity in hot spots or hot zones within LTE networks, seamlessly supplementing the LTE coverage.
In the 3GPP, the stakeholders are working on defining the 5G radio access technology, which is called simply the New Radio (NR).
Structurally, it builds on the groundwork laid by LTE. The radio is based on OFDM technology just like LTE. The fundamental numerology is still based on LTE’s 15 kHz subcarrier spacing and the same basic time unit of 32 53/96 nanoseconds derived from it: additional options (30 kHz and 60 kHz to begin with, with other figures up to 480 kHz for future consideration) are available for subcarrier spacing, and they are all 2X times 15 kHz. The frame and sub-frame durations are still 10 ms and 1 ms respectively.
In fact, it may not be wrong to say that for someone trying to understand the radio technology, 5G will be closer to 4G than 4G was to 3G, 3G was to 2G, and 2G was to 1G: the main difference will be in the scale. In 5G NR, several concepts that were developed in and for 4G LTE will be taken forward.