# An Energy-Efficient Coverage Algorithm for Macrocell--Small Cell Network Systems
## 2 Related Work  
A substantial amount of the previous research regarding the design of cellular network resource allocation has been largely devoted to the involvement of the MBSs in those systems only, with numerous studies (such as [5; 6; 7; 8; 9; 10; 11]) having addressed, in a comprehensive manner, the individual contributions of a variety of approaches, in terms of improved system performance. For example, studies by [PERSON] et al. investigated the proper allocation of resources in single-cell environments [5] and in multi-cell environments [6] when seeking to ensure energy-efficient transmission by the traditional MBS of single component carriers (CCs). The same authors later investigated the utilization of another type of MBS, namely, an MBS that itself utilized the harvesting of hybrid energy, for data transmissions [7]. More recently still, a study by [PERSON] sought to provide a means of minimizing the energy used by the transceivers of an MBS utilizing two CCs, while simultaneously ensuring the necessary quality of service and fairness for users through its proposal of a rate-and-power control transmission scheme [8]. Subsequently, another paper by [PERSON] considered the same system in its construction of a framework aimed at thoroughly examining how to ensure transmission efficiency via both the maximization of system capacity and the minimization of the total energy consumed [9]. This was followed by still another paper from the same author, in which a more flexible scheme for the efficient minimization of total power consumed by the transceivers of an MBS utilizing two or more CCs (while simultaneously ensuring the necessary quality of service and fairness for users)was proposed [10]. That study was followed, in turn, by one in which the author proposed an efficient packet scheduling algorithm aimed at increased transmission efficiency in the context of the simultaneous transmission of both real-time traffic and non-real-time traffic [11]. While those studies largely focused, again, on the involvement of MBSs in systems only, other recent studies have reported the expectation that SBSs will be among the mainstream technologies utilized in the next-generation networks designed to provide energy savings [2; 3]. In order to furnish network service to users, both SBSs and MBSs are reliant on the wireless spectrum. At the same time, the presence and simultaneous use of multiple SBSs and MBSs in a network necessarily creates a number of complicated resource allocation-related issues, and a variety of further studies (such as [12; 13; 14; 15; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25]) have devoted their attention to these issues. For example, discussions have been conducted by the aforementioned 3 GPP organization regarding various possible approaches to conserving power in evolved universal terrestrial radio access networks [12]. Relatedly, [PERSON] et al. proposed a scheme in which user-activity detection would be used to enhance energy efficiency [13], while a study by [PERSON] and [PERSON] [14] explored the cell's energy efficiency (measured in bits per joule) and area energy efficiency (measured in energy efficiency per unit area). In 2011, [PERSON] et al. [15] conducted a study in which they quantified the differing levels of power consumed by different types of BSs, while a 2013 study by [PERSON] et al. [16] suggested a hybrid model for the assessment of converged wireless/optical access network energy efficiency. Two years later, both distributed and centralized optimization methods for addressing small cell cluster coverage optimization problems were proposed by [PERSON] et al. [17], while in 2016, [PERSON] et al. investigated the potential imposition of quality-of-service requirements and interference mitigation as a means of improving transmission efficiency [18].