What is this fuss about RCS ? For the past few weeks I’ve been trying to find the answer to this one. After much information gathering I understood that majority of communicatio platform provider’s mostly OTT such as imessage from apple , RBM already support this features. And it is partially a term coined by Google to bring smart communication festures in Android and other smart phones. In essence RCSe is a part of broader IMS archietcture pulished by GSMA

Update : after 2019 plenty of carriers also already provide RCSe as a replacement of SMS . OEM providers like Samsung also have RCS feature inbuild in phones.

The Rich Communication Services programme is a global initiative to deploy inter-operator services within an industry ecosystem.

Marketed by the GSMA under the brand name joyn,  RCS is an upgrade that marks the transition of messaging and voice capabilities from Circuit Switched technology to an all-IP world.

Wider and large scale IMS deployment, interoperability between different terminal vendor RCS clients and RCS service interworking between operators are the key aims of the RCS Initiative.

Whats special about RCS ?

• Enhanced Phonebook: service capabilities and enhanced contacts information such as presence and service discovery.
• Enhanced Messaging: enables a large variety of messaging options including chat, emoticons, location share and file sharing.
• Enriched Calls: enables multimedia content sharing during a voice call, video call and video sharing (see what I see).

RCS releases

Five releases of the RCS specifications have been made to date. Each release expanded the scope of its predecessor.

Release 1 : Offered the first definitions for the enrichment of voice and chat with content sharing, driven from an RCS enhanced address book.

Release 2 : Added broadband access to RCS features: enhancing the messaging and enabling sharing of files.

Release 3: Focused on the broadband device as a primary device.

Release 4: Included support for LTE.

Release 5: The most recent release, global interoperability is a key aspect of these specifications.

As the team developed a web client for making and receiving SIP calls over websockets through a proxy SIP server , I felt its an  achievement big enough. To integrate it with RCS ( Rich Communication Suite ) stack appeared as a very complicated job .

I began by adding RCS specific standards modules one by one instead of importing the whole stack / library all together.

So the modules for XCAP for buddylist , MSRP for file transfer , geolocation  mapping , cloud sync of phonebook and message book have begun taking shape . In essence following features set are expected out of a RCS enabled Client  ( short outline ) Provisioning

OAUTH integration with operator customer portal

RCS HTTP Auto-Configuration

Manual IMS credentials, typically reserved for testing / troubleshooting

RCS services:

• Service Discovery
  o OPTIONS and Presence supported
  o Address book polling

• Delivery & display notifications o Message composing indication

• 1-1 Chat
  o IMDN
  o Is-Composing
  o Store & forward / deferred message and notification delivery
  o Hotfixes compliant

• Group Chat
  • Hotfixes compliant
  • Is-Composing
  • IMDN
  • Geo-location Push
  • Start and end a group chat session
  • Add or remove participants
  • Broadcast / Send messages to all participants

• File Transfer
  • Send file via URL or as MIME attachment o Accept or Reject file transfer
  • MSRP based
  • HTTP based
  • Store & forward
  • Geo-location push via FT
  • vCard sharing
  • Thumbnail support

• Voice & video
  o Best effort voice
  o Transcode

• Network Address Book Support
  o Synchronization to SyncML based network address book
  o Contact import from Google, Facebook etc.

RCS APIs

( published under Joyn in GSMS RDC Devloepr documents in http://rcs.oneapi-gw.gsma.com)

There are many individual RCS APIs available. Brief details are as follows.

1. Log user in and out of the RCS server Allows address book contacts to receive periodic updates of user availability for chat, file transfer and other services. This is essential for use of the RCS services.

2. Subscribe application to server-originated notifications This is one of the most important aspects of RCS as events are asynchronous; the notifications channel is used by your application to know how an API call is proceeding and to receive updates from other users such as messages, files and status updates. You can subscribe to certain types of notifications if your application is focused on particular RCS services.

3. Network address book access and management RCS provides each registered user with a server managed address book. Though the other APIs are not restricted to contacts in the network address book this makes it much more convenient to connect with other users. The network address book can have contacts added, removed, attributes changed, and is available to any application the user signs in to.

4. Individual chat services Unlike SMS, which is broadly a ‘fire and forget’ service, the RCS chat services allow much more sophisticated messaging services to be built. Depending on user configuration you can check out whether the user has received the message, and displayed it. RCS chat also allows feedback to other parties when a user is composing a message. There are also group chat services allowing multiple parties to collaboratively message. RCS provides API features for setting up a group chat session, adding or removing chat participants.

5. File Transfer These APIs allow applications to send content between users – whether this is a picture or a document, and whether it is stored originally on the user’s device or elsewhere located on the Internet. They allow the recipient to receive information about the file separately from the file itself so the recipient can choose whether or not to accept the file.

6. User capabilities API Enables the application to retrieve and amend system managed common capabilities of the user.

At this stage I will also put in a bit more about RCS e

RCS e ( enhanced )

What is the difference between RCS-e and RCS?

RCS-enhanced (RCS-e) is the currently available version of RCS, developed to speed time to market. It offers enhanced features such as instant messaging, live video sharing, and file transfer across any device on any network operator

RCS e Benefits :

• Focus on advanced communication
  chat , file transfer , video sharing
• Easy to Use
  zero touch from end user perspective
  minimal setup for subscribers
  Interoperability across devices , infrastructure components and service providers
• Low barrier to entry / simplify networks
  Capability discovery using SIP OPTIONS
  Less impact on network elements and handset battery
  Lack of presence server reduces cost and time to market
• Universal
  Allows implementation in lower range devices
  One common device specification

RCS-e Customer Value Proposition

New IP Communication Services , Profile Sharing , Native Device Integration

RCS e Characteristics

Realted Terms

MSRP

File Transfer using   MSRP (or Message Session Relay Protocol) is an instant messaging or chat protocol, defined by the IETF in RFC4975. MSRP is a text-based, connection-oriented protocol for exchanging  arbitrary (binary) MIME content, especially instant messages.

References

Wikipedia – https://en.wikipedia.org/wiki/Rich_Communication_Services

GSMA Rich Communication Services APIs Developer Guide vs1.2