Rich Communication Services

Rich Communication Services (RCS) is a communication protocol standard between mobile telephone carriers for the purpose of instant messaging, developed and defined by the GSM Association (GSMA). It aims to be a replacement of SMS and MMS, with a text-message system that is richer. RCS is also marketed as Advanced Messaging, and was previously marketed as chat features, joyn, SMSoIP, Message+, and SMS+.

RCS has been designed as an industry standard to provide improved text messaging capabilities, and also to regain the influence of mobile network operators against individual OTT (over-the-top) services that have become prominent. Features of RCS include high-resolution photo and video sharing, file sharing, typing indicators, read receipts, operation over mobile data or Wi-Fi, improved group chat functionality, and providing phonebook polling for service discovery. End-to-end encryption is not a feature of RCS specified by GSMA, instead deferring to the individual messaging clients to establish encryption; Google has added support for this feature using RCS in their own text messaging app, Google Messages. RCS services are based on IP Multimedia Subsystem (IMS).

As of 2020, RCS has rolled out across 90 cell operators in 60 countries globally. In addition, RCS can be used anywhere with Google Messages on Android, where it is provided directly by Google via their own Jibe platform backend in place of a mobile operator's. By 2023, there were 800 million active RCS users on Google's platform and 1.2 billion handsets worldwide supporting RCS. Apple plans to support RCS in Messages with iOS 18 in the fall of 2024; RCS is also accessible through desktops via the web client of Google Messages or via Microsoft Phone Link.

Software adoptions

Samsung was one of the first major device original equipment manufacturers (OEMs) to support RCS. Samsung RCS capable devices have been commercially launched in Europe since 2012 and in the United States since 2015. In December 2020, Samsung updated its One UI Messages app to also allow users to opt into RCS.

Google supports RCS on Android devices with its Android SMS app Google Messages, beginning with Lollipop across Android devices. In April 2018, it was reported that Google would be transferring the team that was working on its Google Allo messaging service to work on a wider RCS implementation. In June 2019, Google announced that it would begin to deploy RCS on an opt-in basis via the Messages app, with service compliant with the Universal Profile and hosted by Google rather than the user's carrier, if the carrier does not provide RCS. The rollout of this functionality began in France and the United Kingdom.

In September 2022, Apple CEO Tim Cook said the company had no plans to support RCS on its devices or any interoperability with iMessage. However, in November 2023, an Apple spokesperson stated that the company planned to introduce RCS support in 2024. The decision came after China’s Ministry of Industry and Information Technology proposed new regulation which could have required Apple to support RCS. In June 2024, Apple announced that RCS support would be introduced on iOS 18 in the Messages app; as with SMS, RCS will be displayed with green message bubbles and buttons, although an RCS indicator will display in the text box.

Encryption support

In response to concerns over the lack of end-to-end encryption in RCS, Google stated that it would only retain message data in transit until it is delivered to the recipient. In November 2020, Google later announced that it would begin to roll out end-to-end encryption for one-on-one conversations between Messages users, using RCS but not part of the GSMA's RCS specifications, beginning with the beta version of the app. Google added end-to-end encryption to their Messages app using the Signal Protocol as the default option for one-on-one RCS conversations starting in June 2021. Google stated it would like to collaborate with other companies to make end to end encryption over RCS compatible with other apps. In December 2022, end-to-end encryption was added to group chats in the Google Messages app for beta users and was made available to all users in August 2023. Additionally, Google enabled RCS in Messages by default to encourage end-to-end encryption adoption. In July 2023, Google announced it was developing support for the Messaging Layer Security (MLS) end-to-end encryption standard in Google Messages to encourage interoperability of messaging platforms. Apple stated it will not support Google's end-to-end encryption extension over RCS, but would work with GSMA to create an RCS encryption standard.

Development and history

Launch and "joyn"

The Rich Communication Suite industry initiative was formed by a group of industry promoters in 2007. In February 2008 the GSM Association (GSMA) officially became the project home of RCS and an RCS steering committee was established by the organization, officially announced as Rich Communications Suite on September 15, 2008, later known as Rich Communication Services. The companies involved in launching it were: operators Orange, Telecom Italia, Telefonica and TeleSonera, network vendors Ericsson and Nokia Siemens Networks, and device vendors Nokia, Sony Ericsson and Samsung. The steering committee specified the definition, testing, and integration of the services in the application suite.

By 2010, RCS had released Version 4 of its specification, however progress was slow and it had yet to be deployed on commercial subscriber services. During this time, closed internet-based instant messaging services (known in the industry as "OTT" (over-the-top) providers) were rising in popularity. To accelerate development, the RCS project released a new specification – RCS-e (e = "enhanced"), which included various iterations of the original RCS specifications. At Mobile World Congress 2012, RCS-e was launched under the consumer brand name "joyn" (a brand that has since been abandoned). The full list of carriers that agreed to support RCS-e at the time were AT&T, Bell Mobility, Bharti Airtel, Deutsche Telekom, Jio, KPN, KT Corporation, LG U+, Orange, Orascom Telecom, Rogers Communications, SFR, SK Telecom, Telecom Italia, Telefónica, Telia Company, Telus, Verizon and Vodafone. That year, the first RCS-e/Joyn services were rolled out by networks in Spain, Germany and the US.

Universal Profile

The GSMA published the Universal Profile in November 2016. The Universal Profile is a single GSMA specification, and carriers that deploy the Universal Profile guarantee interconnection with other carriers. As of early 2017, there were 47 mobile network operators, 11 manufacturers, and 2 OS providers (Google and Microsoft) that had announced their support of the Universal Profile. Adoption of RCS increased following Google's purchase of Jibe Mobile, which uses an implementation of the RCS Universal Profile, designed to help carriers launch RCS quickly and scale easily.

In October 2019, the four major U.S. carriers announced an agreement to form the Cross-Carrier Messaging Initiative (CCMI) to jointly implement RCS using a newly developed app. This service was to be compatible with the Universal Profile. However, this carrier-made app never came to fruition. By 2021, both T-Mobile and AT&T signed deals with Google to adopt Google's Messages app. In 2023, T-Mobile and AT&T agreed to use Google Jibe to implement RCS services, and in 2024 Verizon agreed to use Google Jibe.

Comparison with SMS

SMS (Short Messaging Service) was deployed by cellular networks in the 1990s alongside the earliest 2G digital GSM networks. It uses traditional circuit switching technology, as opposed to the data-based packet oriented standards that were introduced with newer technologies like GPRS and which are now standard. SMS has numerous limitations compared to more modern messaging standards (as in instant messenger clients), such as a 160 character limit, lack of read receipts, and media sharing (images may be shared but these would be sent as an MMS, with an increased charge). RCS aims to be a modern successor with newer features while still remaining an open standard for cell networks like SMS and hence would also not be a closed "walled garden" like commercial messaging networks (also known as OTT (over-the-top) services) such as Messenger and WhatsApp.

RCS Business Messaging

RCS Business Messaging (RBM) is the B2C (A2P in telecoms terminology) version of RCS. This is supposed to be an answer to third-party messaging apps (or OTTs) absorbing mobile operators' messaging traffic and associated revenues. While RCS is designed to win back Person-to-Person (P2P) traffic, RBM is intended to retain and grow this A2P traffic. RCS offers "rich" features similar to those of messaging apps, but delivered (in theory) via the preloaded SMS messaging app - for example Google Messages or Samsung Messages. By making these features available in a B2C setting, RBM is expected to attract marketing and customer service spend from enterprises, thanks to improved customer engagement and interactive features that facilitate new use cases. This was the primary reason for the development of RCS by the GSMA.

RBM includes features not available to ordinary users, including predefined quick-reply suggestions, rich cards, carousels, and branding. This last feature is intended to increase consumer confidence and reduce fraud through the implementation of a verified sender system. These additional features are only available with the use of a messaging-as-a-platform (MaaP) server integrated with the operator's network. The MaaP controls the verified sender details, unlocking RBM features, while also segregating P2P and A2P RCS messages, aiding monetisation of the latter (SMS currently suffers from grey routes, where A2P messages are sent over P2P connections, which are cheaper or often free).

Reception

In 2018, Amnesty International researcher Joe Westby criticized RCS for not allowing end-to-end encryption, because it is treated as a service of carriers and thus subject to lawful interception.

The Verge in 2019 criticized the inconsistent support of RCS in the United States, with carriers not supporting RCS in all markets, not certifying service on all phones, or not yet supporting the Universal Profile. Concerns were shown over Google's decision to run its own RCS service due to the possibility of antitrust scrutiny, but it was acknowledged that Google had to do so in order to bypass the carriers' inconsistent support of RCS, as it wanted to have a service more comparable to Apple's iMessage service available on Android.

Ars Technica in 2019 criticized Google's move to launch a direct-to-consumer RCS service, considering it a contradiction of RCS being native to the carrier to provide features reminiscent of messaging apps, counting it as being among various past and unsuccessful attempts by Google to develop an in-house messaging service (including Google Talk, Google+ Messenger, Hangouts, and Allo), and noting limitations: such as its dependencies on phone numbers as the identity (whereas email-based accounts are telco-agnostic), not being capable of being readily synchronized between multiple devices, and the aforementioned lack of end-to-end encryption.

Specifications

RCS Universal Profile

The GSMA's Universal Profile is a globally agreed-upon standard for implementing RCS. The profile allows subscribers of different carriers and nations to communicate with each other. Universal Profile became the dominant RCS specification since its introduction.

Version 1.0 (November 2016)

References RCS Advanced Communications Services and Client Specification (RACSCS) Release 6.0 Version 7.0. Includes capability discovery which is interoperable between regions, chat, group chat, file transfer, audio messaging, video share, multi-device, enriched calling, location share and live sketching.

Version 2.0 (July 2017)

RACSCS Release 7.0 Version 8.0. Includes Messaging as a Platform (MaaP) with chatbots, also known as RCS Business Messages, APIs, plug-in integration and improved authentication and app security. Adds group chat icons, group chat change of subject, and file transfer enhancements. Support for passing group chat administrator to another participant, and allowing various features to fall back to SMS.

Version 2.1 (December 2017)

References the same RACSCS Release 7.0 Version 8.0 as Universal Profile Version 2.0.

Version 2.2 (May 2018)

RACSCS Release 8.0 Version 9.0. Added additional chatbot features and vCard 4.0 format support.

Version 2.3 (December 2018)

RACSCS Release 9.0 Version 10.0. Support for large pager standalone messages.

Version 2.4 (October 2019)

RACSCS Version 11.0. Removes plug-in integration and includes integrated seamless web-view. Added additional chatbot features. This version is planned for the first iOS 18 support of RCS.

Version 2.5 (October 2020)

RACSCS Version 12.0. Additional messaging verification and chatbot features.

Version 2.6 (December 2022)

RACSCS Version 13.0. Optional procedures for file transfer authentication and additional chatbot verification.

Version 2.7 (June 2024)

RACSCS Version 14.0. Adds support for sending message replies, custom emoji reactions, editing and deleting messages. Improves spam handling and adds chatbot features.

Historical specifications

Before Universal Profile RCS became the dominant RCS specification, there was a variety of proprietary RCS specifications that did not allow RCS messaging between carriers. RCS combined different services defined by 3GPP and Open Mobile Alliance (OMA) with an enhanced phonebook. Another phone's capabilities and presence information could be discovered and displayed by a mobile phone. RCS reuses 3GPP specified IMS core system as the underlying service platform to take care of issues such as authentication, authorization, registration, charging and routing.

Release 1 Version 1.0 (December 15, 2008)

Offered the first definitions for the enrichment of voice and chat with content sharing, driven from an RCS enhanced address book (EAB).

Release 2 Version 1.0 (August 31, 2009)

Added broadband access to RCS features: enhancing the messaging and enabling sharing of files.

Release 3 Version 1.0 (February 25, 2010)

Focused on the broadband device as a primary device.

Release 4 Version 1.0 (February 14, 2011)

Included support for LTE.

Release 5 Version 1.0 (April 19, 2012)

RCS 5.0 was completely backwards-compatible with RCS-e V1.2 specifications and also includes features from RCS 4 and new features such as IP video call, IP voice call and Geo-location exchange. RCS5.0 supported both OMA CPM and OMA SIMPLE IM. RCS 5.0 included the following features.

• Standalone Messaging
• 1-2-1 Chat
• Group Chat
• File Transfer
• Content Sharing
• Social Presence Information
• IP Voice call (IR.92 and IR.58)
• IP Video call (IR.94)
• Geolocation Exchange
• Capability Exchange based on Presence or SIP OPTIONS

Release 5.1

5.1 was completely backwards compatible with the RCS-e V1.2 and RCS 5.0 specifications. It introduced additional new features such as Group Chat Store & Forward, File Transfer in Group Chat, File Transfer Store & Forward, and Best Effort Voice Call, as well as lessons-learnt and bug fixes from the V1.2 interoperability testing efforts. RCS 5.1 supported both OMA CPM and OMA SIMPLE IM.

• Version 1.0 (August 13, 2012)
• Version 2.0 (May 3, 2013)
• Version 3.0 (September 09, 2013)
• Version 4.0 (November 28, 2013)

Release 5.2 Version 5.0 (May 7, 2014)

Improved central message store and introduced service extension tags into the specification. It also introduced a number of incremental improvements and bug fixes to RCS 5.1 V4.0 that improved the user experience and resolve issues that were noticed in deployed RCS networks.

Release 5.3 Version 6.0 (February 28, 2015)

Release 6.0 Version 7.0 (March 21, 2016)

First version to be incorporated into Universal Profile, as were the subsequent versions.

RCS-e (enhanced)

An attempt by Europe's five biggest mobile operators to galvanize RCS with a simplified version of RCS.

• Initial Version (May 2011)
• Version 1.2 (November 28, 2011)
• Version 1.2.2 (July 4, 2012)

Joyn

Joyn was a service brand of RCS-e. The GSMA defined a series of specific implementations of the RCS specifications. The RCS specifications often defined a number of options for implementing individual communications features, resulting in challenges in delivering interoperable services between carriers. The RCS specifications aimed to define a more specific implementation that promotes standardization and simplify interconnection between carriers.

• Joyn Hot Fixes (July 15, 2013) - based upon the RCS 1.2.2 specification (previously known as RCS-e), this includes 1:1 chat, group chat, MSRP file sharing and video sharing (during a circuit-switched call). Services based upon this specification were live in Spain, France and Germany.
• Joyn Blackbird Drop 1 (June 19, 2013) - based upon the RCS 5.1 specification, this extends the Joyn Hot Fixes service to include HTTP file sharing, location sharing, group file sharing, and other capabilities such as group chat store and forward. Joyn Blackbird Drop 1 was backwards compatible with Joyn Hot Fixes. Vodafone Spain's network is accredited for Joyn Blackbird Drop 1, and Telefónica and Orange Spain have also been involved in interoperability testing with vendors of Joyn Blackbird Drop 1 clients. A number of client vendors were accredited to Joyn Blackbird Drop 1.
• Joyn Blackbird Drop 2 (September 26, 2013) - also based upon the RCS 5.1 specification, this primarily added IP voice and video calling.
• Joyn Crane (August 18, 2015)

Commercial deployment

Universal Profile is currently backed by "a large and growing ecosystem" (68 supporters in 2019). Universal Profile support is optional in 4G, but mandatory in 5G networks and devices.

• 55 operators: Advanced Info Service, América Móvil, AT&T Mobility, Axiata, Beeline, Base, Bell Mobility, Bharti Airtel, China Telecom, China Unicom, Claro Americas, Deutsche Telekom, Etisalat, Globe Telecom, Ice, Indosat Ooredoo, Jio, KDDI, KPN, M1 Limited, MegaFon, Millicom, MTN Group, MTS (network provider), NTT Docomo, Optus, Orange S.A., Personal, Proximus, Rogers Communications, Singtel, Smart Communications, SLTMobitel, Sprint Corporation, T-Mobile US, Telcel, Tele2, Telefónica, Telenor, Telia Company, Telkomsel, Telstra, Telus, TIM, Turkcell, Verizon Communications, VEON, and Vodafone.
• 12 OEMs: TCL (Alcatel Mobile), Asus, General Mobile, HTC, Huawei, Intex Technologies, Lava International, LG Electronics, Lenovo (Motorola), Samsung Electronics, Sony and ZTE.
• 2 mobile OS providers: Google and Apple in 2024.

Interconnect and hubs

Like SMS, RCS requires national and international interconnects to enable roaming. As with SMS, this will be accomplished with hubbing - where third-party providers complete agreements with individual operators to interwork their systems. Each subsequent operator that connects to a hub is therefore connected automatically to all other connected operators. This eliminates the need to each operator to connect to all the others to which they may need to send messages. RCS hubs are provided by stakeholders with a vested interest in increasing RCS use. These include traditional SMS hub providers (e.g. Global Message Services and Sinch), software and hardware vendors (e.g. Interop Technologies, Mavenir, and ZTE), and also Google via its Jibe Cloud platform.

See also

• Matrix communication protocol
• XMPP, Extensible Messaging and Presence Protocol
• Multimedia Messaging Service (MMS)
• Instant messaging

References

External links

• Official website
• Specifications

1. IOS 18
2. Mavenir Systems
3. Text messaging
4. Multimedia Messaging Service
5. RCS
6. Joyn
7. Google Messages
8. GSMA
9. SMS
10. IMessage
11. Open Mobile Alliance
12. Matrix (protocol)
13. OpenMarket
14. Symphony Communication
15. IP Multimedia Subsystem
16. Media richness theory
17. Honestly, Nevermind
18. Short Message Peer-to-Peer
19. Element (software)
20. Google Allo