Modeling of MTC Energy Consumption for D2D Communications with Chase Combining HARQ Scheme

Device-to-Device (D2D) communication for Massive Machine-Type Communication (mMTC) applications is a promising approach to reduce the energy consumption of the battery-limited Machine-Type Devices (MTDs) located in poor coverage areas. In this paper, we analyze the energy consumption of the MTDs when Automatic Repeat reQuest (ARQ) and Hybrid ARQ with Chase Combining (CC-HARQ) mechanisms are used to improve the reliability of D2D communications. By using the tools of stochastic geometry, we derive analytical expressions for the global success probability, the average number of transmissions, and the average MTD energy consumption. Numerical results show that CC-HARQ outperforms ARQ in terms of energy consumption, especially for low relay density when the distance between an MTD and its relay increases or when the density of MTDs sharing the same sub-channel increases.