Energy-Efficient Hybrid Precoding For Millimeter Wave MIMO-OFDM Communication Systems

Achieving higher wireless transmission rate and network capacity are the objectives for the cellular networks.The millimeter wave communications,massive multiple-input multiple-output(MIMO)technology and ultra-dense network are the key technologies in the fifth generation(5G)cellular networks.Meanwhile,the hardware cost and energy consumption of the 5G cellular network increased dramatically when combining the millimeter wave communications,massive MIMO technology and ultra-dens network.The hybrid precoding consisting of a digital baseband precoding and a radio frequency(RF)chain precoding is considered as an energy-efficient technology to reduce the hardware complexity and energy consumption of 5G cellular network.Moreover,the hybrid precoding is also a key technology to improve the energy efficiency of MIMO orthogonal frequency-division multiplexing(MIMO-OFDM)communication systems.Most of the existed studies focused on optimizing the spectral and energy efficiency of MIMO-OFDM communication systems by designing the hybrid precoding in narrow-band millimeter-wave scenarios.In this paper,single-user and multi-user scenarios are considered in the MIMOOFDM communication systems.The energy efficiency of MIMO-OFDM communication systems is optimized by designing the hybrid precoding.Moreover,the energy consumption structure of base stations and the further optimization for the energy efficiency of the MIMO-OFDM communication systems are shown.Firstly,system models of millimeter wave MIMO-OFDM communication systems in single-user and multi-user scenarios are modeled.The system models of millimeter wave MIMO-OFDM communication systems consists of the downlink transmission model and power consumption model.Multi-subcarrier and multi-user have been considered in the downlink transmission model.The power consumption model contains the communication power,subdivided computational power and fixed power.Moreover,the computational power caused by the complexity of the hybrid precoding algorithm is analyzed particularly in the subdivision of the computational power.Secondly,the energy efficiency of MIMO-OFDM communication systems in the single-user scenario is optimized by designing the hybrid precoding.In this paper,we jointly design the hybrid precoding in broadband millimeter wave systems by designing the hybrid precoding of each subcarrier.The analytical solution of the power allocated to each subcarrier is derived.Moreover,two algorithms,i.e.,the power allocation algorithm and the hybrid precoding algorithm for the single-user scenario,are proposed.Simulations results indicate that the proposed single-user hybrid precoding algorithm achieves 40.72% improvement in energy efficiency at the expense of 4.92% decrease in rate performance of MIMO-OFDM communication systems,compared with the full-digital zero forcing precoding.Finally,the energy efficiency of MIMO-OFDM communication systems in multiuser scenario is optimized by designing the hybrid precoding.The digital precoding is designed for each subcarrier corresponding to every user.Afterwards,the analytical solution of the power allocated to each subcarrier corresponding to every user is derived.A hybrid precoding algorithm is developed to optimize the energy efficiency of MIMO-OFDM communication systems in multi-user scenarios.Simulation results indicate that the energy efficiency achieved by proposed multi-user hybrid precoding algorithm is fully superior of the energy efficiency achieved by the fully-digital zero forcing precoding algorithm.