Device-to-device (D2D) communications is the integral part of public safety (PS) communications. However, the most important requirement is the users’ rapid discovery to timely communicate the emergency information. The existing half-duplex (HD) results in large time delays because it cannot transceive during same time slot. In-band full duplex (IB-FD) communications is an enabler to quickly discover the user because of simultaneous transmission and reception during same time-frequency block. In this paper, we proposed the frame structure for IB-FD system with prioritized PS users in resource allocation. Moreover, to improve spectral efficiency, time-efficient device discovery resource allocation (TE-DDRA) scheme has been proposed as well, where a user can switch the transmission mode from HD to IB-FD when the demand exceeds the available resources in HD mode. The proposal is validated by system-level simulations in terms of discovery time with conventional random access mode. The simulation results shows that with PS priority mode around 37 % discovery time as compared with random access mode.