Everyone says 5G will improve latency, but 4G and 5G are both electromagnetic spectrums that travel at the speed of light. So where is the latency improvement coming from. Nokia has a paper on low latency that goes into lots of details.
Below is a table and graphic that shows you were the times are in a latency calculation.
When you look at transmission and frame alignment you get about 3ms of time savings. Looking at UE and BTS which are user equipment and base station times you get 5 ms of time savings.
So there is actually more time saved in latency in the backend equipment than in transmission.
Ok since I brought up the transmission latency I might as well keep going. If you want to look at where the latency savings in transmission the current standards require a connection to be established to send data, switching between idle and connected modes. In 5G a connection is established and you can suspend and resume which is much quicker.
This applies to the same spectrum with only changing 4G and 5G infrastructure. So the new spectrum is not an issue. It is the transmission, connections, and backend that improve the speeds.