Now that more than 50 service providers on every continent have rolled out 5G, where are we with 5G? and where we are going? are timely questions. When will we get to 5G Standalone (5G SA)?
To date, all 5G networks have been launched with dual connectivity (DC) architecture. DC means that the User Equipment (UE) is connected to two base stations at the same time. In the 3GPP standards, four DC configurations are defined. (See Figure 1 for all 5G configurations)
The DC configuration chosen for the launch of today’s 5G networks is commonly known as Option 3x. Formally, it is known as E-UTRA-NR Dual Connectivity (EN-DC). The EN-DC configuration is defined as a 5G Non-standalone (5G NSA) architecture. An EN-DC configuration relies on the 4G Evolved Packet Core (EPC) and an anchor 4G eNB base station that acts as the master node. In addition, the 5G NR gNB base station is tethered to the 4G eNB and acts as the secondary node. The DC configuration is actually quite clever, combining the capacity of both base stations. By leveraging the existing EPC, it allowed service providers to get to market faster, launching in 2019 rather than in 2020. This is where we are today.