LTE for Public Safety

5Group Communication Over LTE

5.1 Introduction to Group Communication Services

In general, a Group Communication Service provides a fast and efficient mechanism to distribute the same content to multiple users in a controlled manner. As an example, the concept of group communication is used extensively in the operation of classical Land Mobile Radio (LMR) systems such as P.25 in the United States or TETRA in Europe and is used for, but not limited to, public safety (PS) organizations (also commercial realizations exist). At the moment, the primary use of a Group Communication Service in LMR is to enable a “Push to Talk” (PTT) function. PTT is a feature where one person can talk at a certain time (has the “floor” to talk) while all other group members can only listen. Thus, a Group Communication Service based on the 3GPP architecture, using Long-Term Evolution (LTE) radio technology, needs to enable PTT voice communication and meet expected performance requirements, for example, end-to-end latency should be less than 150 ms (source: 3GPP TS 22.468[1]).

The service should allow different media types to be used as communication media to fulfill requirements from different users and environments they are operating in. For example, the capabilities of LTE allow for broadband communication, so an LTE-based Group Communication Service is expected to support voice, video, and in general any kind of data communication. Also, LTE allows a user to communicate with several groups in parallel, ...