Abstract
Addressing high capacity at low power as a key design goal envisages achieving high spectral efficiency (SE) and energy efficiency (EE) for the next-generation mobile networks. Because most data are generated in indoor environments, an ultra-dense deployment of small cells (SCs), particularly within multistory buildings in urban areas, is revealed as an effective technique to improve SE and EE by numerous studies. In this paper, we present a framework exploiting the four most interconnected-domain, including, power, time, frequency, and space, in the perspectives of SE and EE. Unlike existing literature, the framework takes advantage of higher degrees of freedom to maximize SE and EE using in-building SCs for 5G and beyond mobile networks. We derive average capacity, SE, and EE metrics, along with defining the condition for optimality of SE and EE and developing an algorithm for the framework. An extensive system-level evaluation is performed to show the impact of each domain on SE and EE. It is shown that employing multiband enabled SC base stations (SBSs) to increase operating spectrum in frequency-domain, reusing spectrum to SBSs more than once per building in spatial-domain, switching on and off each in-building SBS based on traffic availability to reduce SBS power consumption in power-domain, and using eICIC to avoid co-channel interference due to sharing spectrum with SBSs in time-domain can achieve massive SE and EE. Finally, we show that the proposed framework can satisfy SE, EE, as well as user experience data rate requirements for 5G and beyond mobile networks.
Highlights
We assume that whenever a macrocell user equipments (UEs) of mobile network operator (MNO) 1 is within the coverage of an SC base stations (SBSs) in a building, it is offloaded to the corresponding SBS such that in place of the macrocell, the macrocell UE is served by the in-building SBS of MNO 1 to avoid co-channel interference (CCI) with UEs of the SBS served by its transceiver 1
Recall that if an outdoor macrocell UE is present within the coverage of an in-building SBS of MNO 1, the macrocell UE is served by the corresponding SBS causing no CCI with UEs of the SBS served by its transceiver 1
An indoor macrocell UE is assumed to be offloaded to an SBS whenever it is found within a building such that no co-channel interference can occur among macrocell UEs and small cell UEs even though transceiver 1 of each SBS operates at the same macrocell spectrum
Summary
According to [1], most data is generated in indoor environments, within buildings in urban areas. Due to increasing the use of rich multimedia services on mobile phones over time, the high data rate demand of users increases Serving this large amount of data at a high rate with an outdoor macrocell base station (MBS) is difficult due to the presence of high external wall penetration loss of a building [2], the scarcity of available system bandwidth below 3-GHz [3], and a limit to the maximum transmission power to avoid excessive interference. Due to the existence of a high external wall penetration loss of a building, the same outdoor spectrum can be reused to indoor SBSs within a building by enforcing a proper interference management technique to SBSs such as time-domain almost blank subframe based (ABS) based enhanced inter-cell interference coordination (eICIC) technique [6]. Based on the above discussion, it can be concluded that the capacity, and the spectral efficiency (SE), as well as the energy efficiency (EE) of a cellular mobile system, can be maximized by exploiting four most interconnected-domain, namely power, time, frequency, and space
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