Performance Analysis of Device-to-Device Communications in Cellular Networks Under Varying Load Conditions

Device-to-device (D2D) communications is identified as potential technology for future cellular networks. It is a promising concept to provide the high data rate requirements for bandwidth hungry applications like social networking, multimedia services etc. It facilitates better utilization of radio resources and shorter transmitter receiver delays and therefore better user performance. In this paper framework for studying performance of D2D communications in orthogonal frequency division multiple access based multicellular scenario is developed using downlink cellular resources. The load condition of D2D mode in addition to that of cellular mode plays an important role. The performance of both modes for their respective load conditions have been analyzed. The key parameters analysed are ratio of signal power to noise plus interference power (SINR), outage probabilty, effect of variation in D2D transmitter power, capacity, mode selection and D2D mode switching distance. The goal of the paper is to find the optimum distance for switching to D2D mode from cellular mode for loads with different power ratios. The results shows that D2D communications is beneficial for cellular edge UEs and improves their capacity. It is seen that with increase in load in both the cellular and D2D modes the corresponding link capacity falls. It is also seen that as the cellular load increases, the switching distance moves away from BS while it moves towards the BS when the D2D load increases.