What is eNodeB?
E-UTRAN Node B, also known as Evolved Node B (abbreviated as eNodeB or eNB), is the element in E-UTRA of LTE that is the evolution of the element Node B in UTRA of UMTS. It is the hardware that is connected to the mobile phone network that communicates directly wirelessly with mobile handsets (UEs), as a base transceiver station (BTS) in GSM networks.
What is gNodeB?
gNodeB is a 3GPP-compliant implementation of the 5G-NR base station. It consists of independent Network Functions, which implement 3GPP-compliant NR RAN protocols namely: PHY, MAC, RLC, PDCP, SDAP, RRC, NRAP see Figure below. They can run together or independently and can be deployed on either physical (e.g. a small cell chipset) or virtual resources (e.g. dedicated COTS server or shared cloud resources).
gNodeB 3GPP protocol stack for Control Plane
Difference between eNodeB and gNodeB
eNodeB
The base stations in 4G LTE networks are called evolved Node B or eNodeB. In network architecture diagrams, eNodeB is often also abbreviated as eNB. eNodeB is an essential part of the 4G LTE radio network and is capable of performing network control functions in addition to creating mobile network coverage. If you look at the network diagram above, you may notice that the 4G radio network does not have a separate network controller entity. This is different from GSM and UMTS networks that have BSC and RNC respectively for network control tasks. It means that for LTE, eNodeB is able to perform the radio access functions that are equivalent to what Node B and RNC do together in 3G UMTS. In line with the LTE standard, eNodeB employs separate radio access technologies for the uplink and the downlink. The communication between eNodeB and the cell phone uses Orthogonal Frequency Division Multiple Access (OFDMA) for the downlink and Single Carrier Frequency Division Multiple Access (SC-FDMA) for the uplink. eNodeB also has the intelligence and ability to perform radio network control functions. As part of that, it represents the 4G LTE radio access network E-UTRAN (Evolved UMTS Terrestrial Radio Access Network). It then connects to the 4G LTE core network, the Evolved Packet Core (EPC).
gNodeB:
5G networks use a technology called New Radio or NR for the air interface. There are two ways in which 5G networks can be deployed; standalone mode and non-standalone mode.
Standalone mode (SA) is where 5G networks operate completely on their own without any legacy network i.e. no 4G LTE network dependency.
Non-standalone mode (NSA) is the more common one especially for early adoption of 5G where mobile operators add 5G NR to their existing 4G LTE infrastructure. You may read more about SA and NSA in this post, but the point relevant here is that NSA makes use of the LTE core network EPC (with some enhancements) whereas SA uses a new 5G core network called 5G Core or 5GC.
In both cases, 5G uses a dedicated radio network for the air interface.
The radio network for 5G NR is called Next-Generation Radio Access Network or NG-RAN. Since NSA deployment takes advantage of the existing EPC for core network functions, it requires both LTE and NR radio networks to connect to the same EPC. 4G LTE networks can operate the same way they do today by allowing eNB to communicate with EPC for control plane as well as user plane. In other words, all the radio network functions, as well as user functions (e.g. mobile data, QoS, etc.), take place through eNB.
The 5G radio network node gNB operates slightly differently and is only used for user-level functions. The control plane for 5G is still managed by eNB as part of a concept called dual connectivity. When the 5G Core network is used instead of EPC, the connectivity for any 5G devices uses the gNB node for both user and control planes. Any 4G LTE devices, on the other hand, use ‘next-generation eNodeB instead of the regular eNodeB to be able to communicate with the 5G Core network. The next-generation eNodeB is abbreviated as ng-eNB.
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