• Source: Rich Communication Services

Rich Communication Services (RCS) is a communication protocol standard for instant messaging, primarily for mobile phones, developed and defined by the GSM Association (GSMA). It aims to be a replacement of SMS and MMS on cellular networks with more modern features including high resolution image and video support, typing indicators, file sharing, and improved group chat functionality. As for MMS, mobile service must be activated. Development of RCS began in 2007 but early versions lacked features and interoperability; a new specification named Universal Profile was developed and has been continually rolled out since 2017.
RCS has been designed as an industry open standard to provide improved capabilities over basic text messaging, based on the Internet Protocol (IP). Its development has also been supported by mobile network operators to regain their influence against individual OTT (over-the-top) chat apps and services. Additional features of RCS include presence information, location and multimedia sharing, video calling, and operation over mobile data or Wi-Fi, natively integrated in mobile phones without requiring the download of third-party apps.
As of 2020, RCS has rolled out across 90 cell operators in 60 countries globally, and has over 1 billion monthly active users as of 2023. RCS can also be used anywhere without carrier support using Google Messages on Android, where it is provided via their own Jibe backend in place of a carrier's while still connected to the global RCS network, and additionally offer end-to-end encryption. Apple added support for RCS in Messages with iOS 18 in September 2024; RCS is also accessible through desktops via the web client of Google Messages or via Microsoft Phone Link.




Branding


RCS is also marketed as Advanced Messaging and 5G Messaging (in China), and was previously variously marketed as chat features, enhanced chat, joyn, SMSoIP, and SMS+.




Software support



Samsung Electronics was one of the first major device original equipment manufacturers (OEMs) to support the RCS initiative and it commercially launched RCS capable devices in Europe in 2012 and in the United States in 2015. Following the launch of the new RCS Universal Profile specification, Samsung supported it on new devices since 2017 in its stock Messages app. In December 2020, Samsung updated its One UI Messages app to also allow users to opt into RCS using Google's Jibe backend instead of carriers in certain regions. The Samsung Messages client brands the RCS capability as chat features, and displays Enter chat message in the message box. Starting in 2024, Samsung Messages is no longer coming preloaded on Galaxy phones sold in the United States market in favor of Google Messages.
Mobile phones running Android with Google Play Services support RCS with its native messaging app, Google Messages, beginning with Android Lollipop. 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 (i.e. Jibe) rather than the user's carrier, if the carrier does not provide RCS. Before 2023 the Google Messages app branded RCS communication as Chat, before it was renamed to RCS to be clearer. In March 2024, it was reported that Google was "silently" blocking RCS on rooted Androids.
Other flavors of Android such as Huawei's HarmonyOS in China also support RCS through native messaging clients (EMUI version 8.1+).
In June 2024, Apple announced that support for RCS would be added to the Messages app in iOS 18; as with SMS, RCS is displayed with green message bubbles and buttons, although an RCS indicator is displayed in the message composer text field. iOS 18 launched with support for RCS in September 2024.




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 15 September 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.
However, the RCS standard struggled with fragmentation and incompatibility, with one industry analyst stating in 2015 that the project was a "zombie [..] infected with bureaucracy, complexity, and irrelevance". A Mountain View-based startup called Jibe Mobile, headed and cofounded by Iranian-American engineer Amir Sarhangi, attempted to solve the situation having built an in-house cloud platform claimed to be fully RCS interoperable between carriers, and offering a fast deployment of the service to the carriers. Some operators like Orange and Deutsche Telekom had previously signed up to the Jibe cloud platform.




= Universal profile

=
Google purchased Jibe Mobile in September 2015, and Amir Sarhangi led the RCS project at Google. Subsequently they worked together with the GSMA which led to the creation of the Universal Profile standard. 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, while designed to help carriers launch RCS quickly and scale easily.
The new standard, helped by promotion from Google, finally led to RCS taking off: in 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. To accelerate adoption, Google transferred the team that was working on Google Allo to work on a wider RCS implementation, then in 2019 it launched the Guest programme to provide an OTT (over-the-top) RCS solution using Jibe to all Google Android users, without requiring carrier support; it rolled out globally by 2020.



Adoption

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.
The three Chinese carriers together announced in April 2020 that they will roll out RCS, branded as 5G Messaging. Both China Telecom and China Unicom had rolled out the services within two years time. However, China Mobile, the country's and also world's largest mobile carrier, delayed the roll-out until it began in December 2023. In 2020, Germany's three carriers had all rolled out RCS services, interconnected and provided by Mavenir; Mavenir's RCS network also started powering carrier Rakuten Mobile in Japan, however this network is not linked to the RCS network used by Japan's three largest carriers, who use their own network named +Message that is currently not based on the Universal Profile specifications and not connected to the global RCS network.
In 2023, the Chinese state ruled that all new 5G handsets sold in China from 2024 must support RCS. Media reports stated that this decision led to Apple to announce RCS support on its iPhone, despite Apple CEO Tim Cook having earlier stated that the company had no plans to support RCS on its devices or any interoperability with iMessage.




Comparison with SMS


SMS (Short Messaging Service) was deployed on 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.
Additionally, RCS is IP-based, instead of the Signalling System No. 7 (SS7) standard that SMS uses. Unlike SMS, RCS may require an Internet connection depending on the RCS servers. (further explained in the Technical details section below)




RCS Business Messaging



RCS Business Messaging (RBM) is the business-to-consumer (B2C) (A2P in telecoms terminology) version of RCS. RBM includes unique features, including predefined quick-reply suggestions, rich cards, carousels, and branding, designed to improve customer engagement and interactive features that facilitate new use cases. These are available as standard on preloaded RCS-enabled text messaging apps.
This is supposed to be an answer to third-party messengers (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. These additional features are only available with the use of a messaging-as-a-platform (MaaP) server integrated with the operator's network. SMS currently suffers from grey routes, where A2P messages are sent over P2P connections, which are cheaper or often free.




Technical details



RCS Universal Profile is based on 3GPP's IP Multimedia Subsystem (IMS) architectural framework and uses Session Initiation Protocol (SIP) to establish sessions and exchange messages and other content.
RCS may require an Internet connection depending on the RCS servers: in an IMS 'single registration' setup, the SIP messaging traffic can be forwarded to be sent directly to the carrier's network, instead of going over the top across the Internet in a 'dual registration' scenario. In cases where RCS is able to operate over cellular networks without data, it supports messaging as well as file transfer, enriched calling, and more.




= Features

=

RCS Universal Profile aims to build on SMS with additional interactive features that have become increasingly relevant in world of instant messaging. This includes typing indicators, read receipts, file sharing, high-resolution photo and video sharing, improved group chat functionality, audio messaging, and providing phonebook polling for service discovery. The service directly links to the user's phone number and does not require any account registrations, nor does it require downloading and setting up of third-party chat apps from an app store.




= Encryption support

=
End-to-end (E2E) encryption is not currently a feature of RCS specified by GSMA, instead deferring to the individual clients to establish E2E encryption. However in September 2024, the GSMA announced it was working on bringing interoperable E2E encryption to the Universal Profile RCS standard. RCS uses Transport Layer Security encryption when E2E encryption is not available. Google claims it will only retain message data in transit until it is delivered to the recipient over Google infrastructure. Google Jibe provides RCS infrastructure for various global carriers, as well as Google Messages directly if the carrier does not offer RCS.
In November 2020, Google announced that it would begin to roll out E2E encryption for one-on-one conversations on their Google Messages messaging client - using RCS but not part of the GSMA's RCS specifications - beginning with the beta version of the app. Google added E2E encryption to their Messages app using the Signal Protocol as the default option for one-on-one RCS conversations starting in June 2021. In December 2022, E2E 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 E2E encryption adoption.
In July 2023, Google announced it was developing support for the Messaging Layer Security (MLS) E2E encryption standard in Google Messages to encourage interoperability of messaging platforms. Apple stated it will not support Google's E2E encryption extension over RCS, but would work with GSMA to create an RCS E2E encryption standard.




= Interconnection and hubs

=
Mobile network carriers/operators typically have two ways to deploy RCS services: either basing it on their own IMS infrastructure, or use a third-party hosted service. 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. Sinch), and software and hardware vendors (e.g. Mavenir, ZTE, and most notably Google's Jibe Cloud platform).




Reception



In 2018, Amnesty International researcher Joe Westby criticized RCS for not allowing E2E 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 E2E 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 used in Messages (Apple) with iOS 18.
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. Google Messages had implemented some of the features in this version.




= 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 (15 December 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 (31 August 2009)

Added broadband access to RCS features: enhancing the messaging and enabling sharing of files.
Release 3 Version 1.0 (25 February 2010)

Focused on the broadband device as a primary device.
Release 4 Version 1.0 (14 February 2011)

Included support for LTE.
Release 5 Version 1.0 (19 April 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 (13 August 2012)
Version 2.0 (3 May 2013)
Version 3.0 (9 September 2013)
Version 4.0 (28 November 2013)
Release 5.2 Version 5.0 (7 May 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 (28 February 2015)
Release 6.0 Version 7.0 (21 March 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 (28 November 2011)
Version 1.2.2 (4 July 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 (15 July 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 (19 June 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 (26 September 2013) - also based upon the RCS 5.1 specification, this primarily added IP voice and video calling.
Joyn Crane (18 August 2015)




Commercial deployments


Apple maintains a global list of carriers that support Universal Profile RCS messaging in Messages (Apple). Google Messages supports RCS with these carriers, and additionally supports RCS for all users globally, provided directly by Google Jibe if the carrier does not offer RCS. The GSMA states that Universal Profile support is optional in 4G, but mandatory in 5G networks and devices. In Japan, since 2018, the +Message carrier app uses the Universal Profile RCS protocol and has millions of Android and iPhone users, but it does not currently connect to the global Universal Profile network.




See also


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




References






External links


Official website
Specifications

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