Carrier Sensing for OFDMA-Based D2D Group-Casting Systems

Abstract

Device-to-device (D2D) communications refer to direct communications between two or more devices without transferring data through the base station or other infrastructure. For synchronous D2D communication systems in most recent researches and development, orthogonal frequency-division multiple access (OFDMA) or single-carrier frequency-division multiple access (SC-FDMA) is considered to increase the communication coverage and to maintain the similarity with the cellular communication systems. One important design consideration for OFDMA-based (or SC-FDMA-based) D2D communication systems, particularly in an ad-hoc network mode, is the in-band emission effect, which corresponds to the mutual interference between different signals over other subchannels in the same time slot. To avoid interference from other transmitters or to other receivers, a transmitter may perform carrier sensing, which allows for transmission only when the measured interference is below the given threshold. Since the characteristics of the performance degradation due to other-channel interference (OCI) can be quite different from those by cochannel interference (CCI), the interference measurement must be carefully considered for carrier sensing in OFDMA-based D2D communication systems. This paper discusses physical carrier sensing for interference management in D2D group-casting or broadcasting systems and proposes a mechanism that efficiently avoids the interference from other subchannels. More specifically, outage probability is derived by taking both OCI and CCI into account and is then employed as a reference for the carrier sensing level in the course of selecting the resource blocks (RBs) for D2D communication. We demonstrate that our proposed carrier sensing scheme can significantly increase the areal capacity subject to the given target outage performance.