An overall introduction to the 5G protocol, worth collecting!

The technical specifications related to 5G NR are naturally defined by 3GPP. This system design covers all aspects from mobile phones to base stations, and the content is huge and complex.

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Therefore, I started with the 5G network architecture, sorted out the theme of the protocol and presented it in Chinese. What is the 5G network architecture and the definition of each interface? As shown in the figure below.

Generally speaking, the 5G network architecture is divided into the following three parts: 5G terminal (called UE in the protocol, the most common one is the 5G mobile phone we use); 5G base station (called NG-RAN in the protocol, including the narrow 5G base station gNB, and the upgraded 4G base station connected to the 5G core network, which is the ng-eNB in ​​the above figure); 5G core network (5GC in the above figure, where AMF is called access and mobility management function, which is the core control plane network element; UPF is called user plane function, as the name suggests, it is the user plane network element of the core network).

The design of the wireless technical specifications is mainly centered around 5G terminals and 5G base stations. In addition to the specifications for terminals and base stations, there are also specifications for the air interface between 5G terminals and 5G base stations: NR, and various interfaces between base stations and within base stations (between CU and DU): NG-RAN-related specifications. The above four types of specifications are shown on the left side of the figure above.

The figure above describes the 5G base station protocol stack, as well as the interfaces within and between base stations. The protocol stack supported by 5G base stations is very similar to that of 4G, including PHY, MAC, RLC, PDCP and other layers. The control plane also has an RRC layer, and the user plane adds an SDCP layer for processing QoS-related.

The interface between 5G base stations is the interface Xn between gNB and gNB; the interface within the base station includes the interface E1 between CU and CU, and the interface F1 between CU and DU. These interfaces are defined in the 5G NG-RAN related specifications.

In addition, there is another part in 3GPP, called TR (Technical Report), which is the research report on the technology by each member. The accepted parts will be standardized in subsequent work.

The 5G-related TRs are shown in the following table. The table header is the same as the table above: the first column is the label, the second column is the English subject of the TR, and the last column is the Chinese subject.

The above 3GPP 5G protocol introduction can be viewed at the following address:

https://www.3gpp.org/DynaReport/38-series.htm?device=desktop

The specific 5G NR 38 series protocols can be downloaded from the following address:

https://www.3gpp.org/ftp/Specs/archive/38_series/