Meet Low Frequency / High Frequency Demand 5g Nr Subcarrier Spacing With Adjustment Elasticity.

3GPP announced the new 5G Independent Radio (NR) standard in June 2018, which lays the foundation for a new 5G end-to-end network architecture and establishes the complete specification of 5G R15. However, compared with LTE, 5G NR spectrum covers a wide range of frequencies, including 6 GHz below and 30-300 GHz millimeter wave (mm wave) frequency bands. To enable 5G NR to operate in different frequency bands, 3GPP also adjusts the 5G subcarrier spacing and leakage power requirements.

According to the current national spectrum planning and development, 5G Enhanced Operational Broadband (eMBB) mainly uses bands below 6GHz and 24.5-29.5GHz, 37-43.5GHz. Su Yucheng, Marketing Engineer of national instrument market, pointed out that the spectrum distribution below 6GHz is very different from that of millimeter wave. The spectrum below 6GHz is crowded and fragmented, while the spectrum distribution of millimeter wave is relatively wide. Therefore, both of them should be considered from standard setting, technical development to component design. There are different points.

In order to meet the different bandwidth requirements, the 5G subcarrier spacing is adjusted elastically. In the past, 4G LTE subcarrier spacing was fixed at 15 kHz, but 5G spectrum coverage was quite large, so 3GPP developed a set of elastic parameters (Numerology) to expand the subcarrier spacing. Su Yucheng further shows that the denser the subcarriers, the higher the spectral efficiency, but the smaller the subcarrier spacing is more vulnerable to interference and difficult to resist attenuation, so it is necessary to consider the characteristics of different frequency bands to adjust the subcarrier spacing. For frequency bands below 6 GHz, narrow subcarrier spacing of 15 kHz, 30 kHz and 60 kHz will be used; for millimeter-wave bands, wider subcarrier spacing of 60 kHz and 120 kHz will be used to reduce interference caused by phase noise.

In addition, the bands used in wireless networks, mobile networks and AM / FM broadcasting applications are concentrated below 6GHz, which also causes the problem of congestion and fragmentation of available spectrum. Therefore, in addition to re-dividing the spectrum, how to improve the spectral efficiency is also the future development focus of the band below 6GHz. Su Yucheng pointed out that in the past, in order to avoid interference between adjacent spectra in the 4G LTE spectrum planning, 10% guard band will be reserved for use. In order to solve the problem of spectrum congestion below 5G 6GHz, 3GPP will also increase the requirement of leakage power, only 2% of the protection band will be reserved to reduce the spectrum waste. At the same time, the protection band will be divided into narrow-band technology such as NB-IoT to improve the overall spectrum efficiency.