# 3GPP Release

## Summary


3GPP regularly publishes Technical Specifications (TSs) and Technical Reports (TRs) pertaining to mobile cellular systems (2G/3G/4G/5G). These documents go by the generic term **specifications**. New specifications are created and existing specifications are updated as the technologies evolve. Specifications are grouped into what are called **Releases**. Given a particular release, a mobile system can be constructed. By adding new functionality to a release, 3GPP partners and members construct a new release. 

Coming up with a new release normally takes about 2.5 years. This excludes the time to conceptualize and finalize what should go into the release.  

Companies develop products conforming to a specific release. Release is therefore an important concept for feature support and interoperability. Moreover, each release is designed with backward and forward compatibility in mind.

## Discussion

### How are specifications organized and versioned?

Specifications are organized into **series**, versioned and change-tracked. Documents within a series are closely related technically. For example, 38-series covers 5G, 36-series covers 4G and 25-series covers 3G. Within the 38-series, 38.1xx covers UE and base station requirements, 38.2xx covers PHY, 38.3xx covers radio protocols, etc. 

Every specification is versioned with a version number of the form `x.y.z`. Field `x` refers to the release. Field `y` increments every time technical changes are introduced and approved by the TSG. Field `z` increments every time editorial changes are made. Fields `y` and `z` reset to zero if the preceding fields increment. 

For example, *TS 38.101-4 V17.6.0* is a TS belonging to 38-series and of Release 17. The document is in its sixth technical version with no editorial changes to that version. The suffix "-4" indicates part 4 (parts and subparts are used only for long specifications published as multiple documents). 

Field `x` has a few special values: 0 (draft), 1 (presented to TSG for information), and 2 (presented to TSG for approval). Once approved, `x` takes the value of the release number. 


### What's the typical 3GPP release process?

Every release starts with a vision or concept of what is desired from the release. Proposals are made to add new features or services. Work formally begins when some of these proposals are accepted. Features are typically broken down into smaller elements. 

Each 3GPP TSG meets quarterly to approve Work Items. Work Items with sufficient complexity may be preceded by Study Items. Study Items result in Technical Reports (TRs) that in turn becomes inputs to writing the Technical Specifications (TSs). Either new TR/TS documents are created or existing ones are updated via Change Requests (CRs). Essentially, specifications are change controlled and can be updated only via CRs. 

A new release of a specification is either via CRs, via a request to the TSG, or automatic. If a specification is not updated during a release, it's automatically upgraded from the previous release without any changes. 

The decision-making process is non-linear, iterative and via consensus. There's no voting process at meetings. Delegates discuss and negotiate. In most cases, original proposals are refined before accepted. 


### What's meant by stage 1, 2 and 3 of a 3GPP release?

A release is developed via a three-stage methodology that comes from ITU‑T Recommendation I.130: 

    + **Stage 1**: Overall service description from a user's perspective.
    + **Stage 2**: Overall description of network functions. These map service requirements into network capabilities.
    + **Stage 3**: Definition of switching and signalling capabilities to support services defined in stage 1.A feasibility study is often conducted before defining the specifications. This may be termed *Stage 0*. Likewise, stage 3 may be followed with test specifications. This may be termed *Stage 4*. 

The figure shows Release 18 as an example. From package approval (December 2021) to protocol coding freeze (March 2024), the duration is 2 years and 3 months. Conceptualizing new features or enhancements for the release may begin as early as 12 months before the package approval. We also note that Release 18 overlaps with adjacent releases. This overlap enables continuous progress. 

Stage 3 freeze is usually 1-2 TSG meetings before protocol freeze (release end date). End date is indicative since release may be refined/corrected later. 


### Could you share more details on Change Requests?

CRs add new features, clarify/correct/enhance features of an ongoing release, or correct error in functionally frozen specifications. A CR is on a TR or TS and relates to a Work Item. It should highlight sections of the specification changed and include the changes. 

CRs can undergo multiple revisions. Multiple CRs could be merged. CRs are agreed first within WGs before sent to TSG for approval. CRs can be rejected, withdrawn or postponed either at WG or TSG level. The figure shows an example of three CRs on 23.456 (fictional) specification. CRs are numbered 4, 5 and 6. Apart from CR 6, the other two have undergone revisions. When presented to the TSG plenary, all CRs of a given specification are combined into a single document along with a cover sheet. 

CRs fall into a few categories: A (change to an earlier release), B (add/delete feature), C (functional change), D (editorial change, no impact on implementation), E (not used), and F (correction). When a release is frozen, category F is permitted but other categories are generally not permitted. 


### What online resources are available to 3GPP release contributors?

Every release has a full release description document named *TR 21.9xx*. For example, the document for Release 17 is *TR 21.917*. It can be downloaded from the 21-series page.

The following resources are helpful: 

    + 3GPP portal for members
    + 3GPP FAQ page
    + List of all series
    + Current status of specifications by release
    + Current Work Plan listing applicable Work Items
    + Guidelines for writing Work Items
    + Work Items download
    + Instructions to write a CR
    + CR search service by Netovate or on 3GPP portal
    + Database of all CRs submitted to TSG plenary

### Which are the main 3G releases?

The first 3G release was called **Release 99**. It supported both circuit-switched and packet-switched bearers. It met IMT-2000 requirements set by ITU. Subsequent 3G releases were Rel-4 through Rel-7. Rel-8 was the start of 4G/LTE but 3G continued to evolve in this and later releases. 

Rel-5 introduced High Speed Downlink Packet Access (HSDPA) that supported shared channel transmission, HARQ and higher-order modulations. HSDPA brought lower latency, higher data rate and higher capacity. Rel-6 introduced Enhanced Uplink, aka High Speed Uplink Packet Access (HSUPA), with benefits and techniques somewhat similar to HSDPA. HSDPA and HSUPA are often together called **HSPA**. 

HSPA evolved to Rel-7 with MIMO and higher-older modulations. This was called **HSPA+**. From Rel-8, HSPA+ started supporting Carrier Aggregation (CA). Rel-11 marked the start of **HSPA+ Advanced** with the Multiflow feature. Rel-12 introduced HetNets and Wi-Fi interworking. 

The names 3.5G (HSPA), 3.75G (HSPA+) and 3.9G (LTE) are sometimes used, although this usage is not consistent across the industry. 


### Which are the main 4G releases?

The first 4G/LTE release was Rel-8. It's main features were OFDMA waveform, FDD/TDD operation and an all-IP core network. Rel-9 added femtocells in the form of Home eNodeB (HeNB), Location Services (LCS), Evolved Multimedia Broadcast/Multicast Service (eMBMS), VoLTE and Circuit Switched FallBack (CSFB).  

Rel-10 introduced CA, HetNets and advanced MIMO. It marked the start of **LTE Advanced**. These features were further enhanced in Rel-11 and Rel-12.  

Rel-13 marked the start of **LTE Advanced Pro** with enhancements to CA and MIMO. The standard could achieve 1 Gbps in the downlink, giving rise to the term *Gigabit LTE*. It also introduced unlicensed access (LAA) and IoT (eMTC and NB-IoT). Enhancements to the specifications continued in Rel-14 and beyond.  


### Which are the main 5G releases?

The first 5G release was Rel-15, launched in three phases: early drop with support for Non-Standalone (NSA) operation, main drop with support for Standalone (SA) operation, and late drop. Among its main features were mmWave band support, scalable OFDMA, Dual Connectivity (DC) with LTE, FDD/TDD support, short TTI, mini-slots, massive MIMO, beamforming, and more. The 5G Core (5GC) adopted a Service-Based Architecture (SBA) with network functions, microservices and APIs. 

Rel-16 enhanced MIMO, beamforming, DC/CA, UE power saving, positioning and Dynamic Spectrum Sharing (DSS). It also added new features: Integrated Access and Backhaul (IAB), operation in unlicensed spectrum, time-sensitive networking for industrial IoT, NR sidelink for Vehicle-to-Everything (V2X) communications, and more. Apart from many enhancements, Rel-17 added 60 GHz unlicensed band support, satellite communications and sidelink relaying. 

Rel-18 marks the start of **5G Advanced** meant to enhance MIMO, mobility, AI-based decisions, sidelink, positioning, satellite communications, multicast, DSS, multi-SIM, and more. 

## Milestones

Dec  
1998

The 3GPP Partnership Project Agreement is signed by **five Organizational Partners**: ARIB (Japan), ETSI (Europe), ATIS Committee T1 (USA), TTA (South Korea) and TTC (Japan). Their goal is to produce the 3G specifications. Subsequently, they expand their scope of work to include GSM/GPRS/EDGE specifications (since 2000) and evolution of 3G (since 2007). 

2000

Release 99 for **UMTS/3G** is launched. It evolves to Rel-4 (2001). 

2002

Rel-5 comes out. It's the first release of **High Speed Packet Access (HSPA)**. Also part of HSPA is Rel-6 (2004). This further evolves to **HSPA+** in Rel-7 (2007), Rel-8 (2008), Rel-9 (2009), and Rel-10 (2011). The next evolution is **HSPA+ Advanced** in Rel-12 (2015) and Rel-13 (2016).  The slightly different dates in the figure reflect dates of commercial deployment. 

2008

With Rel-8, the first release of **4G/LTE** is launched. The LTE project work was started in December 2004. Originally named Evolved Universal Terrestrial Radio Access (E-UTRA) for the radio access part, it becomes significantly different from the UMTS system. LTE evolves to **LTE Advanced** in Rel-10 (2011), Rel-11 (2012) and Rel-12 (2015). This evolves to **LTE Advanced Pro** in Rel-13 (2016) and Rel-14 (2017). The slightly different dates in the figure reflect dates of commercial deployment. 

2018

Rel-15, the first release of **5G**, comes out in 2018, although an "early drop" occurred in December 2017. This is followed by Rel-16 (2020) and Rel-17 (2022). This evolves to **5G Advanced** in Rel-18, which is expected in 2023. 

2027

The first release of **6G**, in Rel-21, is expected in 2027.