Dynamic Spectrum Sharing (DSS) is the technology that allows the mobile operators to use the same frequencies to deliver both 4G and 5G. So that both 4G and 5G wireless signals are broadcast over the same frequencies. The main advantage is that the allocation of the frequency to the 4G or 5G network can be based on demand. This is obviously an advantage to the operators in these times when they have 2 different networks to manage.

For example, if an operator has 20GMHz of frequency at the 3.5GHz frequency range and wanted to split this (regulator permitted) between 4GLTE and 5GSA. Then they could allocate half to each of these networks, but with DSS the spliut would be dynamic that is dependent on the demand.

There are obvious advantages for using DSS. Most importantly perhaps is that the new network (5G) can be integrated into the network, and later the 4G can be moved 'out' dependent on demand and at all time utilising optimally the available frequency. Suitable frequency for mobile communications is much in demand but low on supply with no possibility to increase the supply. If the newer 5G network can use the existing 4G network then immediately 5G has a much larger network.

DSS is usde by all 4 mobile operators in the UK to share the mid band spectrum betwenn 5G and 4G-LTE. This is possible due to the support from OfCom.