Relay location considering in-band emission for OFDMA-based D2D overlay systems

In device-to-device (D2D) communication systems, orthogonal frequency division multiple access (OFDMA) is widely used to secure the communication coverage and maintain the similarity with cellular systems. In order to avoid severe interference between cellular and D2D systems, one can use overlay schemes, where D2D devices use dedicated sub-channels of uplink OFDMA resources. However, sub-channels in OFDMA systems are not completely orthogonal and there is still some interference between sub-channels due to in-band emission. There are many advantages of D2D communications and the advantages can be enjoyed even for not-very-close devices by using D2D relays. In this paper, we discuss the optimal relay location taking care of in-band emission for OFDMA-based D2D overlay systems.