SMS is the most basic of mobile messaging systems. There have been enhancements to allow long messages (over 160 characters), MMS (to allow images etc) and there are delivery receipts, but it is still seen as an old technology; useful for basic simple text but not as good as the commercial messaging systems,iMessage, Facebook Messenger and WhatsApp.

RCS protocol was proposed in 2007 but only since 2018 have things got going mainly due to the enthusiasm of Google. RCS has been built into Google (now Android) Messages and more recently into Samsung Messages. Thus it is available on more modern Android phones. Additionally to use RCS the carrier needs to support RCS. In the UK Vodafone and THREE support RCS. There are no signs, nor any likelihood, that Apple are about to implement RCS, they have iMessages!!

RCS has been recently labelled Chat. The protocol allows text messages to be sent 1 to 1 or indeed to groups of people. Additionally picture messages, videos and many more files are supported. Live chat with typing indication is available, ass are audio and video calls. Indeed all the features built into WatsApp or iMessage. Whereas with Whatsapp, both parties need the same app, iMessage needs Apple hardware, RCS works between different RCS apps over a carrier that supports RCS. For Vodafone users RCS has been available between customers with Google Messages installed. RCS is backwards compatible and if any part of the communication does not support RCS, it will then rollback to MMS or SMS.

A second important part of RCS is Business RCS where businesses can interact with customers, so called B2C communication. This can be used by businesses to deliver electronic artefacts, sending tickets, item delivery notifications, or indeed any other electronic notification.

RCS has been slow to grow but with the backing of Google and (some) carriers in the UK it is set to take off. But is it secure. Well it does NOT support end to end encryption but does retain the same legal intercept standards as does SMS currently. Even with RCS, simple SMS messages still have a place. SMS do not need 4G or WiFi but only a weak 2G signal to work.