5G Standards and Protocol Reference

1- Purpose

This article answers the following questions:

• What are the main 5G standards organizations?
• What is the vision for 5G?
• What is the progress of 5G standards formulation?

2- Overview

5G has become one of the most widely discussed topics across both media coverage and everyday conversation. To build a clear and grounded understanding of this transformative technology, this document begins at the foundation — the standards organizations that define what 5G actually is and how it works.

3- Standards Organizations

5G: The foundation of next-generation connectivity

5G — short for 5th Generation Mobile Network — is more formally known as New Radio (NR), and carries the official ITU designation IMT-2020. That name signals both scope and timing: International Mobile Telecommunications, built for 2020 and the decades that follow.

Two organizations govern how 5G becomes reality.

The International Telecommunication Union (ITU) establishes the vision and defining performance targets, spectrum requirements, and use-case mandates that 5G must satisfy. Think of the ITU as setting the bar. Once standards are submitted, it performs the final evaluation to confirm compliance.

The 3rd Generation Partnership Project (3GPP) does the heavy engineering. Every protocol, radio interface, and network architecture specification that makes 5G work in the real world originates from 3GPP. Where the ITU defines what 5G must achieve, 3GPP defines how.

Together, these two bodies underpin the entire wireless ecosystem, from the chipsets powering mobile devices to the infrastructure connecting billions of users worldwide.

3.1 ITU

Founded in 1865 and headquartered in Geneva, Switzerland, the ITU is first one of the 15 United Nations specialized agencies and is mainly responsible for information and communication technology (ICT). We benefit from the work of the ITU in our daily life, such as making phone calls, surfing the Internet, or sending e-mails.

Figure 3-1 ITU

The ITU consists of three Sectors: ITU Radiocommunication Sector (ITU-R), ITU Telecommunication Standardization Sector (ITU-T), and ITU Telecommunication Development Sector (ITU-D), with multiple research work groups (WGs) in each Sector. 5G standardization is mainly carried out by the Working Party 5D (WP 5D) of ITU-R.

During the formulation of 5G standards, the ITU is mainly responsible for research in the early stage of standardization and continuously promotes the consensus of global 5G standards. In September 2015, the ITU officially named 5G "IMT-2020", which is consistent with the official names of 3G (IMT-2000) and 4G (IMT-Advanced). The ITU also finalized the official logo of 5G.

Figure 3-2 5G official logo

3.2 3GPP

The 3GPP established in December 1998 was initially aimed to formulate and implement global 3G mobile communications system specifications within the scope of the ITU's IMT-2000, hence the name 3rd Generation Partnership Project.

Figure 3-3 3GPP

Currently, the seven 3GPP organizational partners are from China, Europe, the US, Japan, South Korea, and India, including:

• China Communications Standards Association (CCSA)
• European Telecommunications Standards Institute (ETSI)
• North America's Alliance for Telecommunications Industry Solutions (ATIS)
• Japan's Association of Radio Industries and Businesses (ARIB)
• Japan's Telecommunication Technology Committee (TTC)
• South Korea's Telecommunications Technology Association (TTA)
• Telecommunications Standards Development Society, India (TSDSI)

Figure 3-4 3GPP organizational partners

3GPP is essentially a global alliance of the wireless communications industry. It aims to formulate more detailed technical specifications and standards based on the requirements proposed by ITU to unify the specifications of the wireless communications industry.

In the 3GPP organizational structure, the Project Coordination Group (PCG) is responsible for overall coordination, such as overseeing the time frame and work assignment of 3GPP organizations, while the Technical Specification Groups (TSGs) dominate technical work.

3GPP consists of three TSGs:

• TSG radio access network (TSG-RAN): is responsible for the functions, requirements, and interfaces associated with the radio access network.
• TSG Service and System Aspects (TSG SA): undertakes system and service work.
• TSG Core and Terminals (TSG CT): encompasses work for core networks and terminals.

Each TSG is further divided into multiple WGs, each WG handling specific tasks.

Table 3-1 lists the latest organizational structure of 3GPP. There are 15 WGs for specific standard formulation and one ITU-specific WG — RAN AH1 — for information transmission and sharing between the 3GPP and ITU.

Table 3-1 3GPP organizational structure

The 3GPP organizational structure does not always remain unchanged, but will be adjusted with the development of technologies. The most recent adjustment was in July 2020. At the RAN#88e plenary meeting, 3GPP announced the closure of WG6 under TSG RAN, which was responsible for GERAN and UTRAN radio and protocol work, that is, 2G and 3G protocol specifications.

3GPP specifications are managed based on releases, such as R15 and R16. It takes about 15 to 21 months to formulate and release (or freeze) a version. The first version released by 3GPP is R1999, which is the first 3G standard. 1999 refers to the year 1999, and later versions are no longer named by year. In 2008, 3GPP released the first LTE standard — R8. The first 5G standard, R15, was released in 2017.

Figure 3-5 3GPP release history

4- 5G Vision

The development of mobile Internet in 4G has profoundly changed people's lives, but people's pursuit of higher-performance mobile communications has never stopped. 5G will penetrate into various fields of the society in the future and build a user-centric comprehensive information ecosystem.

Since 2012, the ITU has organized the global industry to start research on 5G standardization in the early stage. In September 2015, the ITU defined the vision and application scenarios of 5G and proposed its key capability indicators.

According to ITU-proposed vision white paper, 5G has three typical application scenarios: enhanced Mobile Broadband (eMBB), ultra-reliable low-latency communication (URLLC), and Massive Machine-Type Communications (mMTC), as shown in Figure 4-1.

• eMBB is a further evolution of current mobile broadband services and mainly serves the consumer Internet. It supports higher network bandwidth and rate, and further larger data traffic and enhanced user experience.
• URLLC is a communication with an ultra-low latency and ultra-high reliability. It has extremely strict requirements on performance such as throughput, latency, and reliability. It can be applied in fields such as wireless control of industrial manufacturing or production processes, remote surgery, power distribution automation of smart grids, and transportation security.
• mMTC refers to a service that supports a large quantity of terminals. This scenario is most characterized by a large quantity of connected devices that usually transmit a relatively small amount of delay-insensitive data. The device cost needs to be reduced, and the battery endurance needs to be significantly prolonged.

Figure 4-1 Three 5G application scenarios

The ITU also defines 5G key capability indicators from eight aspects, as listed in Table 4-1. Figure 4-2 shows the comparison of these key indicators between 5G and 4G. This is the cobweb model that is familiar to the industry.

Table 4-1 5G key capability indicators

Figure 4-2 Comparison of key indicators between 5G and 4G

In addition to the preceding eight key indicators, the ITU proposes the following five performance indicators to ensure the flexibility, reliability, and security of 5G in different application scenarios:

• Spectrum and bandwidth flexibility: the flexibility of a system design in different application scenarios, especially the capability to operate in different frequency ranges, including a higher frequency and a wider channel bandwidth.
• Reliability: the ability to provide specific services with high availability.
• Recovery capability: the ability of a network to continue to operate properly when or after natural or man-made interference (such as a power failure of the main power supply) occurs.
• Security and privacy: Multiple fields are involved, for example, encryption and integrity protection of user data and signaling, protection of end users' privacy against unauthorized user tracing, and protection of networks against hacker attacks, fraud, DoS, and man-in-the-middle attacks.
• Operational life: operating time after each energy storage. This is especially important for machine-type devices that require extremely long battery life (for example, more than 10 years). Due to physical and economic factors, routine maintenance of such devices is a demanding task.

5-5G Standards Formulation Progress

The ITU defines the vision and requirements of 5G, but the specific standards research and formulation are implemented by the 3GPP.

At the RAN workshop on 5G held in Phoenix, USA, in September 2015, 3GPP proposed the standards research timeline for 5G, aiming to submit 5G technical standards within the time schedule planned by the ITU.

3GPP Release 15:

5G's first chapter began with 3GPP Release 15 (R15) — the foundational standard that defined the technical specifications for enhanced Mobile Broadband (eMBB). Rather than rolling out as a single monolithic spec, R15 was deliberately structured in two phases to give operators flexibility and speed their path to market.

The first phase addressed Non-Standalone (NSA) architecture, with its protocol standards frozen in December 2017. NSA was designed to be practical: it leverages 5G New Radio's superior transmission capabilities to boost the speed and capacity of existing 4G infrastructure, without replacing it. The tradeoff is intentional — NSA relies on the 4G core network, which means it can't fully unlock the new services that 5G is ultimately built to deliver.

The second phase brought Standalone (SA) architecture, finalized in June 2018. This is where 5G stands on its own as a complete, independent network with a native 5G core. SA marks the moment the 5G standard was officially complete and truly capable of supporting the full spectrum of next-generation services.

Together, these two phases gave the industry a pragmatic on-ramp: operators could deploy NSA quickly to deliver immediate performance gains, while building toward the full SA architecture that makes 5G's long-term promise real.

3GPP Release 16:

Release 15 was where it began. As the first standardized version of 5G, R15 laid the foundation by addressing enhanced Mobile Broadband (eMBB), delivering the raw speed and capacity that made 5G headlines. But R15 was a starting point, not a finish line. It established that 5G could work. What came next determined whether it would work for the world.

That's where Release 16 changed everything.

Building on R15's groundwork, R16 didn't just refine eMBB — it expanded 5G's ambitions entirely. It brought serious attention to the two application scenarios that R15 left incomplete: Ultra-Reliable Low-Latency Communications (URLLC), critical for industrial automation and mission-critical connectivity, and massive Machine-Type Communications (mMTC), the backbone of large-scale IoT deployments. Frozen in July 2020, R16 marked 5G's transformation from a consumer technology into a platform for entire industries.

R16 is, by every meaningful measure, the first complete version of 5G.

It's also practical in ways that matter. R16 addressed the real-world concerns of network operators and enterprises alike — optimizing for cost efficiency and energy consumption, not just peak performance. The result is a 5G ecosystem that's not only more capable, but more deployable, more sustainable, and more ready for the demands of vertical industries from manufacturing to healthcare to transportation.

R15 opened the door. R16 built what's behind it.

3GPP Release 17:

3GPP Release 17 & 18: Advancing Connectivity for the Intelligent Era

With Releases 15 and 16 frozen and commercially deployed, 3GPP wasted no time kicking off research for Release 17 (R17) in June 2019.

R17 marks a decisive step deeper into vertical industry transformation. Building on the foundation R16 established, it advances critical capabilities across massive MIMO and multi-antenna technologies, ultra-reliable low-latency communications (URLLC), Industrial IoT, device power efficiency, high-precision positioning, and Vehicle-to-Everything (V2X). But R17 doesn't stop at refinement it introduces a new layer of capability purpose-built for emerging real-world demands: enhanced coverage reach, native multicast and broadcast support, sidelink communication for mission-critical and commercial device-to-device use cases, and intelligent multi-SIM device optimization.

R17 was officially frozen in June 2022, laying a robust and future-ready platform for the innovations R18 continues to build upon.

3GPP Release 18:

R18 is a further evolution of 5G, that is, 5G-Advanced, also known as 5.5G. It will further improve and enrich 5G application scenarios and gradually expand to cross-industry fields. Typical application scenarios will be expanded from the original triangle to the hexagon, with three new scenarios added: Uplink Centric Broadband Communication (UCBC), Real-Time Broadband Communication (RTBC), and Harmonized Communication and Sensing (HCS), revealing the sprout of 5.5G/6G development. R18 will significantly improve eMBB performance, popularize new immersive services such as XR, meet the requirements of large-scale digitalization in the industry, achieve intelligent connection of everything, and enable 5G to generate greater social and economic values. R18 has been frozen in June 2024.

Table 5-1 Main content and freezing time of 5G protocols

6 Overview of 5G Protocols

Introduction to 3GPP Specifications

The 3GPP specifications formulation process can be divided into two phases: Study Item (SI) and Work Item (WI). The former completes the feasibility study of the project, with the output being Technical Report (TR), while the latter completes the writing of technical specifications, with the output being Technical Specification (TS). The TR provides the background and significance of standards formulation, and the TS provides detailed technical specifications.

3GPP specifications are numbered in the following format:

• 3GPP TR aa.bbb (technical report)
• 3GPP TS aa.bbb (technical specifications)

aa is the serial number, and bbb is the tail number in the series. For example, 5G protocol 38.211 indicates the 211 protocol in the 38 series.

In addition to the serial number and tail number, a complete technical specification name must contain the version number, that is, x.y.z, where:

• x is the major field, which corresponds to the release version.
• y is the technical field. The value of this field is incremented when a technical change is made to a specification.
• z is the editorial field. The value of this field is incremented each time a non-technical change (such as editorial change) is made to a specification.

Their relationships are as follows: y is reset to zero every time x is incremented, and z is reset to zero every time y is incremented.

The following figure shows an example of a specification. It is the 201 protocol in the 38 series. The specific version number is V16.0.0, corresponding to R16 and indicating that no technical or non-technical changes have been made to this document in R16.

Main 5G Protocols

The 5G system mainly consists of the 5G access network (NG-RAN) and 5G core network (5GC). The protocols related to the NG-RAN are mainly in the 38 series, and those related to the 5GC are distributed in different series based on functions and services, for example, the 29 series for Service Based Architecture (SBA), 28 series for network slice management, 26 series for such applications as V2X/VR/AR/network automation, and 32 series for 5G charging.

This document describes the protocols related to the NG-RAN, that is, the 38 series. The 38.1xx series are RF specifications, 38.2xx series are air-interface physical-layer specifications, 38.3xx series are air-interface higher-layer specifications, 38.4xx series are NE interface specifications, and 38.5xx series are terminal conformance specifications. These specifications are in the charge of different WGs under the TSG RAN, as listed in Table 6-1.

Table 6-1 Main contents of 38 series protocols and corresponding WGs under the TSG RAN

Table 6-2 to Table 6-6 list the numbers and main contents of related protocols.

Table 6-2 38.1xx series: RF specifications

Table 6-3 38.2xx series: air-interface physical-layer specifications

Table 6-4 38.3xx series: air-interface higher-layer specifications

Table 6-5 38.4xx series: NE interface specifications

Table 6-6 38.5xx series: terminal conformance specifications

In addition, technical reports on some important topics will be provided in the project research phase during standards formulation. Table 6-7  lists 5G-related technical reports.

Table 6-7 5G technical reports