A review of public safety communications, from LMR to voice over LTE (VoLT E)

Public safety communications users in the United States are living in times of unprecedented change. From the challenges associated with the FCC's recent LMR narrowbanding mandate, which limited mobile radio channel bandwidths to 12.5 kHz, to the creation of FirstNet, the world's first, all-LTE public safety broadband network, public safety practitioners are changing the way they react and communicate during times of need. Though the network architecture for FirstNet has yet to be defined, an IMS-based VoLTE solution is the likely voice application successor to LMR push-to-talk and group calling. However, it remains to be seen whether or not VoLTE can provide the features and quality of service that public safety professionals have come to expect and rely on. And the problem is not confined to emergency responders in the United States - the worldwide community of P25 and TETRA users are evaluating the value of migrating to an LTE-based emergency communications network as well. This paper offers a high level discussion on the history of LMR, the basics of LTE and VoLTE, and implementation and testing recommendations based on possible FirstNet architectures.