ese assumptions lead to latency of 5.0, 2.8, 1.9, and 1.2 ms for subcarrier spacings of 15-120 kHz. Latency can be improved with mini-slot transmission by using only part of the TTI. Mini-slot improves latency especially for low band FDD deployments using 15 kHz sub- carrier spacing. Table 10.9 and Figure 10.11 show the latency with 15 kHz mini-slot 10.4 Latency Table 10.9 Two-way latency with mini-slot transmission with 15 kHz with UE capability 2. Delay component 14-symbol 7-symbol 4-symbol 2-symbol Downlink transmission (ms) Uplink transmission (ms) Downlink frame alignment (ms) Uplink frame alignment (ms) UE processing - reception (ms) UE processing - transmission (ms) BTS processing - reception (ms) BTS processing - transmission (ms) Transport and core (ms) Total (ms) Round trip time 14-symbol 7-symbol 4-symbol 2-symbol Downlink transmission Uplink transmission Frame alignment Scheduling UE processing - RX UE processing - TX BTS processing - RX BTS processing - TX Transport and core Figure 10.11 Two-way latency with mini-slot transmission with 15 kHz with UE capability 2. assuming UE processing capability 2. The latency estimate shows that it is possible to achieve below 2 ms two-way latency with 15 kHz FDD and with mini-slot. FDD has an inherent benefit in terms of latency because uplink and downlink trans- missions can run simultaneously. The TDD frame will add some latency because uplink transmission is not available during the downlink, and vice versa. When the packet 10 5G Performance Sub-6 GHz with 30 kHz subcarrier spacing Figure 10.12 TDD frame adds latency 2.5 ms compared to FDD. Downlink Downlink Downlink Switching Uplink mmW with 120 kHz subcarrier spacing 0.625 ms D = downlink D D S U S = switching U = uplink arrives in the uplink transmission buffer, it has to wait until the uplink transmission part of the TDD frame. The packet in the downlink may also need to wait until the downlink transmission part starts, but the downlink frame alignment time is typically short because the TDD frame is confi