ABSTRACT
In the context of energy saving and operational cost reduction, energy efficiency (EE) has emerged as an important performance metric in cellular networks. According to the famous Shannon capacity theorem, maximizing the EE and maximizing the spectral efficiency (SE) are conflicting objectives; hence, both metrics can be jointly studied via the EE-SE trade-off. In this context, the aim of this chapter is to investigate the fundamental trade-off between EE and SE in the futuristic fifth-generation (5G) cellular networks in which a distributed multipleinput multiple-output (D-MIMO) scheme is used for meeting their high data rate requirement. More specifically, it presents a framework for comprehensively analyzing the D-MIMO system from both an EE and an SE perspective by means of an accurate closed-form approximation (CFA) of its EE-SE trade-off. The chapter first introduces the EE-SE trade-off concept in a generic fashion. Next, it provides the relevant background information regarding D-MIMO’s system model, capacity expression, realistic power consumption model (PCM), and EE-SE trade-off formulation. Subsequently, the generic CFA of the D-MIMO EE-SE trade-off is presented and then analyzed for specific scenarios with one or a larger number of active radio access units (RAUs), respectively, and with practical antenna settings. Next, the D-MIMO EE-SE trade-off CFA is compared with the nearly exact approach (based on Monte Carlo simulation and a linear search algorithm), and the great accuracy of the former is established over a wide range of SE values for both the uplink and downlink channels as well as for both idealistic and realistic PCMs.
