Transmission Reduction Scheme in an Emergency Warning System with LTE D2D

In Japan, an Earthquake and Tsunami Warning System (ETWS) in LTE is being adopted to provide emergency warning for quick evacuation. This paper proposes to enhance the ETWS by leveraging the device to device (D2D) communications in LTE. In particular, we propose to extend the coverage of e node B (eNB)s through relaying among User Equipment (UE)s with Proximity Service (ProSe) device to device (D2D) capability, such that the important ETWS messages may reach people even out of the coverage area of eNBs. By exploiting the distribution information of UEs around the eNB, we also develop a new relaying scheme to reduce the number of transmissions in the relaying process, such that an efficient dissemination of ETWS messages can be achieved. The experiment results based on a network scenario with UE density of 24 UEsjkm2 or more indicate that by applying the proposed relaying scheme, the total number of transmissions can be reduced as high as 27% on average.