# Energy and Spectral Efficiency Balancing Algorithm for Energy Saving in LTE Downlinks
###### Abstract  
In wireless network communication environments, Spectral Efficiency (SE) and Energy Efficiency (EE) are among the major indicators used for evaluating network performance. However, given the high demand for data rate services and the exponential growth of energy consumption, SE and EE continue to elicit increasing attention in academia and industries. Consequently, a study of the trade-off between these metrics is imperative. In contrast with existing works, this study proposes an efficient SE and EE trade-off algorithm for saving energy in downlink Long Term Evolution (LTE) networks to concurrently optimize SE and EE while considering battery life at the Base Station (BS). The scheme is formulated as a Multi-objective Optimization Problem (MOP) and its Pareto optimal solution is examined. In contrast with other algorithms that prolong battery life by considering the idle state of a BS, thereby increasing average delay and energy consumption, the proposed algorithm prolongs battery life by adjusting the initial and final states of a BS to minimize the average delay and the energy consumption. Similarly, the use of an omni-directional antenna to spread radio signals to the user equipment in all directions causes high interference and low spatial reuse. We propose using a directional antenna instead of an omni-directional antenna by transmitting signals in one direction which results in no or low interference and high spatial reuse. The proposed scheme has been extensively evaluated through simulation, where simulation results prove that the proposed scheme is efficiently able to decrease the average response delay, improve SE, and minimize energy consumption. b 2021 13 211  
where frequent transitions may lead to high energy consumption. Moreover, dynamically adjusting the idle threshold is difficult because of time-varying traffic. Therefore, an efficient SE and EE Trade-off (SET) algorithm is proposed in this study; this algorithm mitigates the ineffectiveness of the DRX algorithm. The major difference between the proposed SET algorithm and the DRX algorithm is the manner in which the sleep-mode is adjusted: initial and final state. The packet arrival interval and transmission time of the DRX algorithm are adjusted using exponential and general distribution methods, respectively, whereas that of the proposed SET algorithm are adjusted in accordance with the packet arrival pattern. In this study, an enhancement to the DRX power-saving algorithm, namely SET, is proposed for saving energy in downlink LTE networks. The Radio Resource Control (RRC) idle state in the DRX algorithm is analytically enhanced. In contrast with the DRX algorithm, the proposed SET algorithm dynamically adjusts the RRC at initial and final states on the basis of downlink stochastic arrival pattern. In addition, an improved sleep-mode scheme is proposed to minimize numerous transitions to listening mode, which consequently reduces the high energy consumption when the traffic arrival is less. The simulation results show that the SET algorithm considerably outperforms the DRX algorithm in terms of SE, SET, average response delay, and energy consumption. The major contributions of this study are fourfold. Firstly, SE and EE are concurrently optimized as a Multi-objective Optimization Problem (MOP). Secondly, the MOP is transformed to a Single-objective Optimization Problem (SOP) by using a weighted sum technique, thereby proving that the scheme is quasi-concave while its Pareto optimal solution is also examined. Thirdly, an efficient algorithm namely SET is proposed to prolong the battery life, which reduces energy consumption at a BS. Lastly, the performance of the proposed SET algorithm is evaluated via simulation, where the results clearly demonstrate the considerable gain of the SET algorithm compared to other methods.