Text Conversation

Description

Text Conversation is a service concept defined in 3GPP specifications that describes a real-time exchange of text between users, where each character is transmitted immediately upon entry. This differs from store-and-forward messaging like SMS, where the entire message is composed and then sent. Text Conversation enables a more interactive, conversational experience, similar to a live chat. It is specified in 3GPP TS 22.226 and TS 23.226, which outline the service requirements and technical realization for text conversation and text telephony.

The service operates over a circuit-switched or packet-switched bearer, depending on the network generation. In its simplest form, it uses a low-rate data channel to carry text characters as they are typed. The receiving terminal displays the characters in real time, allowing both parties to engage in a fluid dialogue. This is particularly useful for users who are deaf, hard of hearing, or have speech impairments, as it provides an alternative to voice conversation. It also supports multi-party conversations and can be combined with other media.

Architecturally, Text Conversation can be implemented using the ITU-T T.140 protocol for real-time text, which defines how text is transported over IP networks. In 3GPP, the service may be realized over IMS (IP Multimedia Subsystem) using the RTP payload for text, or over circuit-switched networks using the GSM text telephony features. The key requirement is low latency and character-by-character transmission, which ensures that the conversation feels natural and immediate.

The service includes mechanisms for text formatting, such as bold or italics, and may support features like text conferencing and interworking with other text services. It also defines procedures for session setup, modification, and teardown. Because it is real-time, it requires a continuous connection and appropriate QoS to avoid delays or loss of characters. The 3GPP specifications ensure interoperability between different terminals and networks.

Text Conversation has evolved with the advent of smartphones and over-the-top messaging apps, but the 3GPP standard provides a standardized, operator-controlled alternative that can be integrated with emergency services and accessibility features. It is a key enabler for total conversation, which combines voice, video, and text in a single session. The service continues to be relevant in the context of 5G and beyond, where real-time text can be part of immersive communication services.

Purpose & Motivation

Text Conversation was created to address the need for real-time text communication that is more interactive than SMS. Traditional text messaging is store-and-forward, meaning there is a delay between sending and receiving, which is not suitable for conversational use. For users who rely on text for communication, such as the deaf and hard of hearing, this delay can be a significant barrier. Text Conversation provides a real-time, character-by-character transmission that mimics the immediacy of voice conversation.

The service also solves the problem of interoperability between different text-based communication methods. By standardizing the requirements and technical realization in 3GPP, it ensures that users can engage in text conversations across different networks and devices. This is particularly important for emergency services, where real-time text can be used to communicate with emergency responders.

Historically, text telephony existed in various proprietary forms, but 3GPP's standardization in Release 2 and subsequent releases brought a unified approach. The introduction of IMS and IP-based text (using T.140) further enhanced the service, allowing it to be integrated with other multimedia services. Text Conversation remains a vital accessibility feature and a foundation for modern real-time text applications.