tted with either 15 kHz or 30 kHz subcarrier spacing. For both cases, there are two SS block positions in each slot, as shown in the following figure: 15 kHz 0.5 ms 30 kHz 0.5 ms 30 kHz Figure 5.7 SS block mapping locations - below 6 GHz (FR1) In the 15 kHz case, the slot duration is 1 millisecond, and two possible SS block positions can be seen in the figure. In the 30 kHz case, the slot duration is 500 microseconds. So, two SS block locations are possible in this period. As you can see in the preceding figure, there are two different mappings for 30 kHz. The second one is intended for low-latency use cases. It has an empty pair of OFDM symbols within SS blocks, which allows downlink and uplink transmissions for low-latency scenarios. SS block locations show an alteration for frequencies above 6 GHz. The following figure presents the SS block locations in a slot for the 120 kHz and 240 kHz subcarrier spacings: Physical channels and signals for the initial access procedure -SSB mapping locations > 6GHz 0.125 ms 2 SS block locations in each slot 0.125 ms 4 SS block locations in each two slot Figure 5.8 - SS block mapping locations - - above 6 GHz (FR2) In 120 kHz, we have two SS block locations in a 125 microseconds slot, whereas we can see 4 SS block locations in the case of 240 kHz. SS blocks for LTE-NR coexistence What we mean by LTE and NR coexistence is providing LTE and NR networks at the same RF frequency and that share the same bandwidth. This coexistence requires that NR SS blocks shall not collide with LTE cell reference signals; otherwise, this would create interference. This is crucial for the sake of LTE network performance. The 30 kHz subcarrier spacing case is the only one that can guarantee that no interference occurs between NR SS blocks and LTE cell reference signals. 0.5 ms 30 kHz Figure 5.9 - The SS block for LTE-NR coexistence The preceding figure shows the 30 kHz mapping during 1 millisecond of the LTE subframe, and in red, you can see the locations of the LTE cell reference signals. Recall f