What is the difference between Node B, eNodeB, and gNB?

If you are familiar with the base stations within the 3G, 4G and 5G mobile networks, then you may have come across the terms Node B, eNodeB and gNodeB before. Base stations are part of a mobile radio network that represents the largest part of the overall mobile network.

Node B is the radio base station in 3G UMTS networks; eNodeB is the radio base station in 4G LTE networks; gNodeB (gNB) is the radio base station in 5G NR networks. These radio base stations (nodes) are the cell towers mobile operators use to connect our mobile phones to 3G, 4G and 5G networks.

Node B vs eNodeB vs gNodeB

Node B, Evolved Node B (eNodeB) and Next Generation Node B (gNodeB) are radio base stations that allow mobile phones to connect to 3G, 4G and 5G mobile networks. Node B belongs to the 3G UMTS (Universal Mobile Telecommunication System) network, eNodeB belongs to the 4G LTE (Long Term Evolution) network, and gNodeB belongs to the 5G NR (New Radio) network. There are two types of radio base station nodes in 5G networks: gNodeB and ng-eNB. Both of these nodes allow the mobile phone to connect to the 5G core network (5GCN). gNB allows 5G phones (devices) to connect to the 5G core network using the 5G radio interface, whereas ng-eNB allows 4G LTE devices to connect to 5G core network using 4G radio interface.

Node B, eNodeB, and gNodeB are part of the radio network

A mobile network is a massive investment for a mobile operator as it consists of many network components that work together to enable cellular services for customers. At a high level, a mobile network consists of a radio network and a core network. The radio network is the largest part of the overall mobile network and comprises cellular towers (radio base stations) that every mobile phone must be able to connect to in order to be in service. As a result, the radio base stations or radio nodes are deployed throughout towns and cities to provide full network coverage. If a mobile operator does not invest properly in the radio network, that can result in coverage holes. The radio network connects to the mobile core network, which is like a telephone exchange or central office. The core network connects the mobile users to external networks to make calls or to access the internet. Node B in 3G, eNodeB in 4G and gNodeB in 5G are part of the mobile radio network. The diagram below provides a visual representation of this concept and also lists the nodes included in 2G, 3G, 4G and 5G radio and core networks. This is not a full list but enough to provide a good overview of the key network nodes.

What is Node B?

Node B, sometimes also written as NodeB, uses WCDMA – Wideband Code Division Multiple Access for the air interface to connect mobile phones to the network. In the overall UMTS network architecture, Node B is part of the UMTS Radio Access Network or UTRAN (UMTS Terrestrial Radio Access Network).

When 2G GSM networks (Global System for Mobile Communications) started in the early 1990s, wireless connectivity was enabled by the radio base stations, also known as Base Transceiver Stations or BTS. The word ‘transceiver’ suggests that the base station is capable of transmitting as well as receiving. When 3G UMTS networks came, the 3G base stations were assigned a new terminology, ‘Node B’. If a mobile operator wants to provide nationwide 3G network coverage, it needs to deploy a large number of Node Bs throughout the country.

In 3G UMTS networks, Node Bs are controlled by another radio network entity called the Radio Network Controller- RNC. The 2G equivalent of RNC in the GSM network is the Base Station Controller or BSC. When your cell phone screen shows 3G or H or H+ symbol next to the signal bar, you are being served by a Node B. As shown in the network diagram above, Node B and RNC collectively represent the 3G UMTS radio access network. The RNC then connects to the SGSN (Serving GPRS Support Node) through the transport network to establish a connection between the 3G radio access network and the 3G mobile core. I have written a dedicated post on UMTS networks where you can find information about how UMTS works and which frequencies are used by Node B in different geographical regions.

What is eNodeB?

eNodeB, often abbreviated as eNB, stands for Evolved Node B, and it is the radio base station in 4G LTE networks. eNodeB is an essential part of the 4G LTE radio network (E-UTRAN) 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 the combined work that Node B and RNC do in 3G UMTS networks. eNodeB represents the 4G LTE radio access network E-UTRAN – Evolved UMTS Terrestrial Radio Access Network. It connects to the 4G LTE core network, the EPC – Evolved Packet Core.

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 employs Orthogonal Frequency Division Multiple Access (OFDMA) for the downlink and Single Carrier Frequency Division Multiple Access (SC-FDMA) for the uplink. Have a look at our Mobile Networks Made Easy if you want to build an overall understanding of how the different network entities, including, eNodeB, operate within a mobile network.

What radio network nodes are used in 5G?

gNodeB (gNB) is the 5G radio base station that connects 5G New Radio (NR) devices (e.g. 5G phones) to the 5G core network using the NR radio interface; ng-eNB is an upgraded version of 4G LTE radio base station that connects 4G LTE devices to the 5G core network using the LTE radio interface.

5G networks use a new technology called New Radio (NR), which requires new radio base stations. In the context of 5G networks, two types of radio base station nodes are talked about: gNodeB (gNB) and next-generation Evolved Node B (ng-eNB). 5G NR and 4G LTE networks will co-exist for a long time to cater to a wide range of customer use cases. It means that 5G will not replace all 4G networks; but instead, a combination of 4G LTE and 5G NR networks will work together. Achieving that would require both 4G and 5G to be well-integrated to address deployment scenarios where both gNodeB and ng-eNB can be used. The radio network interface in 5G is called Next Generation Radio Access Network or NG-RAN.

5G radio network nodes vs 5G deployment types

5G network deployment can take place in two ways: standalone (SA) and non-standalone (NSA). The difference between the two deployments is the type of core network used. A non-standalone 5G deployment makes use of the 4G core network, whereas a standalone deployment uses a dedicated 5G core network. I have written a dedicated post on the difference between standalone and non-standalone 5G deployments, but let’s have a look at these deployments in the context of radio network nodes. The non-standalone mode (NSA) is the more common deployment option, especially for the early adoption of 5G, where mobile operators add 5G NR to their existing 4G LTE infrastructure. NSA makes use of the LTE core network EPC (with some enhancements), whereas SA uses a new 5G core network called 5G Core Network or 5GCN.

4G and 5G networks are expected to co-exist for a very long time, which means that irrespective of the deployment model used (NSA or SA), we expect to see both LTE and NR devices for a very long time. If a mobile operator chooses to use a 5G core network (5GCN), the LTE and NR networks are designed in such a way that both 5G and 4G phones (and other devices) can connect to the 5G core network. When a 5G phone is connected to the network in the NSA mode, the user-level functions (e.g. mobile data bandwidth, service quality etc.) take place on the 5G radio network, whereas the control-level functions (e.g. signalling) take place on the 4G LTE network. The device, essentially, is connected to both 4G and 5G networks at the same time through a concept called Dual Connectivity.

User and control planes for eNB, gNB and ng-eNB

With a 5G core network, gNB is responsible for both user and control planes for 5G NR devices, and ng-eNB is responsible for user and control planes for 4G LTE devices. With a 4G core network in non-standalone 5G, gNB is responsible for the user plane, and eNB is responsible for the control plane.

The dual connectivity concept is a significant one for the co-existence of LTE and 5G. In dual-connectivity, a mobile phone is connected to both 4G and 5G networks simultaneously; however, the type of connectivity is different. In a non-standalone deployment (NSA), the size of the data connection, quality of service (QoS) and other user-level functions for a 5G NR device (e.g. a 5G phone) are handled by the 5G NR radio network (gNodeB). This user-level connection is called the user plane. However, the control-level functions for the 5G device are part of the control plane and are handled by the 4G LTE radio network (eNodeB).

When a 5G core network is used, the connectivity is different. When a 5G device needs to connect to the network, the gNodeB (gNB) can provide both control and user planes using the NR radio interface. On the other hand, when a 4G device needs to connect to the network, ng-eNodeB (ng-eNB) can provide both control and user planes using the LTE radio interface.

Conclusion

Node B, eNodeB (eNB), gNodeB (gNB) and ng-eNodeB (ng-eNB) are essential radio network components that allow 3G, 4G and 5G mobile phones to connect to the mobile network. Node B is the radio base station for UMTS networks (Universal Mobile Telecommunication System), eNodeB or eNB is the radio network node for LTE networks (Long Term Evolution), and gNB is the radio network node for 5G NR networks. ng-eNodeB is an upgraded radio base station for 4G LTE that connects to a 5G core network. These nodes are installed at the cell sites of mobile operators and are generally known as cell towers.