Energy Efficiency-Spectral Efficiency Trade-Off of Transmit Antenna Selection

Abstract

Abstract-We evaluate the Energy Efficiency-Spectral Efficiency (EE-SE) trade-off of Multiple-Input Multiple-Output (MIMO) and Transmit Antenna Selection/Maximum Ratio Combining (TAS/MRC) schemes. A realistic power consumption model (PCM) is considered, and it is shown that using TAS/MRC can provide significant energy savings when compared to MIMO in the low to medium spectral efficiency region, regardless the number of antenna elements. If the number of receive antennas is fixed, the energy efficiency gain of using TAS/MRC becomes even greater with the increasing number of transmit antennas. The optimal value of spectral efficiency that minimizes the energy consumption is obtained in closed-form, and confirmed by numerical results. Moreover, it is also shown that considering a non-realistic PCM can lead to mistakes when analyzing the gain obtained by using TAS/MRC instead of MIMO.

On the Area Energy Efficiency of Multiple Transmit Antenna Small Base Stations

“…To compute the network total power consumption, P net , we employ a PCM combining [3] and [13], which also takes into account the number of active antennas at the BS. Thus,…”

“…An important task in network planning is finding the optimal number of BSs that achieves a desired quality of service while maximizing the energy efficiency. Moreover, it is well known that choosing a proper antenna technique can lead to either meeting the increased traffic demand, or reducing the power consumption [3]. Looking forward to improve spectral efficiency, the long term evolution (LTE) cellular network 4G standard [4] employs multiple antenna (MIMO) technologies in order to mitigate the effects of fading, providing diversity gains, or to increase the network capacity, providing multiplexing gains through spatial multiplexing (SM) techniques.…”

“…It is worth noting that LTE already employs TAS, but at the user equipment (UE) only [7], while at the BS side it could lead to greater area energy efficiency (AEE), with the same diversity order as in MIMO [8]. Moreover, according to [3], when analyzed through a realistic power consumption (PCM) model, TAS is more energy efficient when compared to SM in the low to medium spectral efficiency region.…”

“…The use of a realistic PCM is important to evaluate the energy efficiency, as shown, e.g., in [3], [9]- [11], which take into account several components that consume power in a BS, such as the AC-DC main power unit, cooling and DC-DC power supplies, as well as the RF power amplifier chain for communications. Additionally, the works in [12], [13] have shown that the power consumed by the backhaul -i.e., the power consumed by the aggregation switches, which is a function of the network traffic -should not be neglected into a complete network energy efficiency evaluation, since it may be the bottleneck in terms of energy consumption.…”

“…We also assume that interference may not be fully canceled due to, e.g., the interference mitigation technique or imperfect CSI estimation, so that we consider a fraction of residual interference denoted by κ. Moreover, we employ a realistic PCM that combines [3] and [13], i.e., it scales with the number of active antennas at the BS for the different MIMO techniques [3], at the same time that it includes the backhaul power consumption [13]. Differently from [9]- [11], by considering TAS we observe different trade-offs in terms of AEE between the MIMO techniques.…”