  Long Term Evolution (LTE), which has its root on commercial mobile
communications, recently becomes an influential solution to future public
safety communications. To verify the feasibility of LTE for public safety, it
is essential to investigate whether an LTE system optimized for one-to-one
communications is capable of providing group communication, which is one of the
most important service concepts in public safety. In general, a number of first
responders for public safety need to form a group for communicating with each
other or sharing the common data for collaboration on their mission. In this
article, we analyze how the current LTE system can support group communication
in a radio access aspect. Based on the requirements for group communication, we
validate whether each LTE-enabled radio access method can efficiently support
group communication. In addition, we propose a new multicast transmission
scheme, termed index-coded Hybrid Automatic Retransmission reQuest (HARQ). By
applying the index coding concept to HARQ operations, we show that the LTE
system can provide group communication more sophisticatedly in terms of radio
resource efficiency and scalability. We finally evaluate the performance of
LTE-enabled group communication using several radio access methods and show how
the proposed transmission scheme brings the performance enhancement via system
level simulations.
