erent: there are no CRSs at all. 5G has user-specific reference signals instead, where the reference signals are trans- mitted together with data. If no user data transmission occurs, there is no reference signal transmission either. There are a number of benefits in flexible reference signal transmission: Lower base station power consumption. The 5G base station can utilize power sav- ing mode during low load cases because there is no need to keep up with frequent reference signal transmission. The ultimate target is "zero users-zero power con- sumption." Less interference from reference signals, which minimizes inter-cell interference and improves network capacity. LTE cell reference signals make 10% of the total base sta- tion power during maximum loading, but the share of reference signals is substantially higher - even 50% of the interference - during the low load. More efficient beamforming. CRSs are useless for user-specific beamforming, which requires user-specific reference signals. Since beamforming is an essential part of 5G systems, the reference signal structure needs to be designed accordingly. Figure 3.13 illustrates the transmission of LTE reference signals: 20 times in a 5 ms period, that is, four times every millisecond. 5G does not have any CRS. Only synchro- nization and broadcast channels are transmitted with a typical frequency of every 20 ms. The relative share of 5G common channels becomes even lower when the subcarrier Synchronization Cell-specific and broadcast reference signals Synchronization 15 kHz subcarrier spacing and broadcast Synchronization 30 kHz subcarrier spacing and broadcast Figure 3.13 Lean carrier in 5G. 3 Technology Components spacing increases. Both 15 and 30 kHz cases are shown. Synchronization and broadcast channels use four symbols, i.e. 1.4% of all symbols in 20 ms with 15 kHz and 0.7% of all symbols with 30 kHz. 3.4.6 Adaptive Reference Signals Reference signals are required for the channel estimation and demodulation of user data. The reference signal transmission