-DC (New Radio Dual Connectivity) radio interfaces. Figure 5.1 shows the deployment of a 5G radio node in the FR1 (Frequency Range 1) band at the frequency of 3.5 GHz on a 4G site that operates LTE in a 700 MHz band. Operations on the different frequency bands improve coverage and throughput: - spectrum sharing and the SUL technique allow the deployment of 5G on the FDD band at 700 MHz. The coverage is important but has weak capacity (e.g. the band is limited to 10 MHz); - with dual connectivity, UE are controlled in the 4G band and the data rate is increased thanks to the 5G interface. With 4G connectivity at 700 MHz, the coverage is important and 5G connectivity at 3.5 GHz allows higher data rates; - carrier aggregation increases the data rate thanks to it having more bandwidth to allocate. Band 3.5 GHz UL/DL 5G Co-existence band: 700 MHz (4G/5G FDD) 5G band 2: 3.5 GHz (5G TDD) Figure 5.1. 5G coverage with DC, CA and SUL (Ericsson). For a color version of this figure, see www.iste.co.uk/launay/5g.zip Among all the users under 4G coverage in the cell: - 45% of users only access 5G in the 3.5 GHz band (5G-SA). SUL mode allows mobiles to transmit on the uplink in the 700 MHz band. - 67% of users have access to the 5G-NSA network: the control plan is carried out by the eNB base station on the LTE interface and the dual connectivity allows for increased speed via 5G-NR radio access. 5G-NR Radio Interface - Operations on the Frequency Bands - 84% of cell users have access to 5G services thanks to the carrier aggregation technique. The control plane is carried out in the 700 MHz band. 5.2. Carrier aggregation Carrier aggregation increases the bandwidth by combining several carriers. Each aggregated carrier is referred to as a component carrier (CC). 5G-NR CA supports up to 16 contiguous and non-contiguous CCs with different numerologies in the FR1 (Frequency Range 1) band and in the FR2 band. The number of DC radio channels aggregated on the DL is greater than or equal to the number of DC radio channels aggregated on 