fix sets the maximum subcarrier spacing. Slot duration affects latency based on subcarrier spacing. cell size large medium latency decreases small frequency medium Figure 4.16 - Numerology and latency The use of large subcarrier spacing in small cells is capable of providing very low delays. It is necessary to use an extended cyclic prefix in large cells. Waveform, numerology, and frame structure Mixed numerology NR supports multiplexing or the mixing of different numerologies, such as TDM and/or FDM in the downlink and uplink, both in time and frequency. From a device's perspective, FDM mixed numerology is limited to data and SSB. NR does not mandate a device to transmit and receive with more than one numerology at the same time. There are two use cases for multiplexing numerologies in FDM. The first one is multiplexing data channels with data channels using different numerologies. This case is not supported in Release 15, but it will be supported to transmit and receive from a device using two different numerologies in later releases. However, having the downlink in one numerology and the uplink in another one is supported in Release 15. The second use case is the multiplexing of the SS block and the data channels using different numerologies. This case is optional from a device point of view, as mentioned before. It is important to note that a device does not have to read both signals at once. AAAAAAAAAAAAAAAA AAAAAAAA .................. Subcarriers Figure 4.17 - Multiplexing SS block and data channels Special care must be taken when transmitting and receiving simultaneously using different subcarrier spacing. The OFDM waveforms for different subcarrier spacings are not always orthogonal with each other, which means, for instance, a 30 kHz transmission can interfere with a 15 kHz transmission on the adjacent frequency resources. To mitigate the interference, you can either include relevance between different numerologies or filter the transmission of the different subcarrier spacings to reduce the interference