Rich Communication Services
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.
[1] RCS has been designed as an industry open standard[2][3] 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.
Following the launch of the new RCS Universal Profile specification, Samsung supported it on new devices since 2017 in its stock Messages app.
[19] 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.
[29] Other flavors of Android such as Huawei's HarmonyOS in China also support RCS through native messaging clients (EMUI version 8.1+).
[38][39][40] 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.
[37] During this time, closed internet-based instant messaging services (known in the industry as "OTT" (over-the-top) providers) were rising in popularity.
[37][42] However, the RCS standard struggled with fragmentation and incompatibility,[43][44] with one industry analyst stating in 2015 that the project was a "zombie [..] infected with bureaucracy, complexity, and irrelevance".
[45] 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.
[56] 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 is supposed to be an answer to third-party messengers (or OTTs) absorbing mobile operators' messaging traffic and associated revenues.
[74] 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.
[82] RCS Universal Profile aims to build on SMS with additional interactive features that have become increasingly relevant in world of instant messaging.
[84][85][86][87] However in September 2024, the GSMA announced it was working on bringing interoperable E2E encryption to the Universal Profile RCS standard.
[91] 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.
As with SMS, this will be accomplished with hubbing - where third-party providers complete agreements with individual operators to interwork their systems.
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).
[100] 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.
[90][103] 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.
[119] RCS combined different services defined by 3GPP and Open Mobile Alliance (OMA) with an enhanced phonebook.
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.
The RCS specifications often defined a number of options for implementing individual communications features, resulting in challenges in delivering interoperable services between carriers.
