Modeling DRX for D2D Communication

Discontinuous reception (DRX) has been included in 4G-LTE as the main power saving mechanism for user equipment (UE). However, the existing 3-state DRX model is not sufficient for new use cases introduced by 4G and 5G. For example, the device discovery process in device to device (D2D) communication has a significant impact on delay and power consumption, but the existing conventional 3-state DRX model is unable to capture this impact. In this article, we propose a novel 5-state DRX model for D2D communications using a semi-Markov process, with separate arrival processes for data and discovery messages. The proposed model includes separate states for the discovery process, and is general and easy to extend for possible future changes. Our model allows us to investigate the behavior of the system under various DRX and discovery parameters. Numerical results show significant influence of the discovery phase on the performance of the DRX mechanism and provide new insights into how it affects power saving and delay.