In recent years, the public safety community has been aligning behind LTE (Long Term Evolution) technology as the basis for next generation public safety networks. Correspondingly, the 3GPP (3rd Generation Partnership Project) standards body has started multiple technical work initiatives on LTEenhancements to better support public safety use cases and requirements. Of particular importance to the public safety community is the addition of direct device-to-device (D2D) broadcast capability that can enable off-network, push-to-talk (PTT) group communications in a manner equivalent to existing public safety communication systems.
In this paper, we briefly explore the design objectives for, and challenges associated with, providing a D2D broadcast service. We then present and analyze a new distributed, media access control (MAC) scheme for interference-aware coordination of both unicast and broadcast transmission. System-level simulation results are provided to validate the performance and the effectiveness of our approach, using a CSMA-based approach as a basis for comparison.