NB-IoT Architecture | LTE-NB IoT Architecture
This page covers NB-IoT Architecture as per 3GPP LTE-NB Specifications.It describes various elements used in the LTE NB-IoT architecture.
3GPP has released specifications for narrowband cellular IoT solution known as LTE-NB or NB-IoT utilizing 200 KHz bandwidth. It has been released in Rel.13, Rel.14 and Rel.15. NB-IOT is known as LPWAN (Low Power Wide Area Network) technology. The technology mainly focuses on improving indoor coverage, low cost, long battery life and larger number of connected devices. Let us understand overall network architecture as shown in figure-1.
As shown, there are two main parts in the NB-IoT architecture access network and core network. UEs are connected to eNBs (i.e. base stations) using Uu interface. The eNBs are connected together via X2 interface. The eNBs are connected to Core network side using S1 interface. This S1 interface carry either NB-IoT control packets or data packets. Though NB-IoT does not support handover, X2-interface is used to enable fast resume from IDLE state of UE. One can refer RRC Connection Establishment Produre to know more about different states of UE. Overall, access network part is similar to LTE.
LTE NB-IoT Architecture | Core Network Side
There are two optimizations used in CIoT (Cellular IoT) based architecture such as NB-IoT. Control plane is marked in red and user plane is marked in blue. In NB-IoT new node called SCEF is designed to handle machine type data. It is used for delivery of non-IP data over control plane. It also provides abstract interface for the network services such as authentication, authorization, discovery and access nework capabilities.
The figure-2 depicts data transmission and reception.
• UL data are transmitted from eNB to MME. From there it may either follow SGW to PGW path or to SCEF path. From this node, they are forwarded to application server for CIoT services.
• DL data is transmitted over same paths but in reverse direction.
• This LTE NB-IoT architecture does not require data radio bearer setup. Data packets are sent on signaling radio bearer instead. Hence this architecture based solution is most ideal for transmission of infrequent and small data packets.
Reference: 3GPP 36 series Rel.13, 14, 15
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