Relay UE Selection Scheme in an Emergency Warning System Integrating Proximity Services

In Japan, early warnings such as the earthquake early warning and the tsunami warning are broadcast to cellular phones by using the Earthquake and Tsunami Warning System (ETWS) [1]. The connectivity of a LTE device (UE: user equipment) depends on the LTE base station (evolved Node B: eNB) which acts as a relay with the Internet. Therefore it is difficult to broadcast early warnings during large-scale disasters.