Energy Efficiency in LTE-U Based Small Cell Systems

In this paper, we study how to improve the energy efficiency (EE) of the LTE unlicensed small cell systems. Since the small base station (SBS) can use both licensed and unlicensed bands, the EE on licensed and unlicensed spectrum need to be considered jointly to improve the EE of the whole system. First, the trade-off between the EE on licensed and unlicensed bands is analyzed when the SBS reuses the licensed bands with a macro base station (MBS) and shares unlicensed bands with multiple Wi-Fi access points (AP)s. Furthermore, the weighted Tchebycheff method is applied to demonstrate the Pareto optimal EE tradeoff on licensed and unlicensed bands numerically. Based on the analysis, how the EE on the licensed bands interacts with the EE on the unlicensed bands is revealed. Accordingly, ajoint power, licensed and unlicensed spectrum allocation scheme is proposed to improve the system EE. Numerical results are presented to validate the analysis and verify the effectiveness of the proposed schemes.