Performance analysis of sidelink data communications in autonomous mode

Third Generation Partnership Project (3GPP) has defined a solution for direct-mode communications by introducing SideLink (SL) channels in LTE-Advanced Pro. First, we point out that in case of autonomous SL operation, half-duplexing constraints combined with the current SL Hybrid Automatic Repeat Query (HARQ) protocol can heavily affect the decoding performance. These degradations are taken into account for the derivation of an analytical model of the SL data channel successful MAC access probability. This model, which has been validated by simulation, is of particular interest for Public Safety (PS) applications and it avoids overestimation of the SL throughput at high spectral efficiencies. Finally, by using the proposed model, it is shown that if a minimum requirement on successful access probability is imposed e.g. by PS applications, then SL communications as defined in LTE-Advanced Pro can support only a small number of concurring transmitters. For instance, for a minimum successful access probability of the SL data channel equal to 90%, only up to 8 transmitters can be supported by the SL data channel using a typical SL configuration.