# Efficient Power Control Framework for Small-Cell Heterogeneous Networks
### Related Work  
Recently, there has been an upsurge in the interest in heterogeneous networks [7]. In this regard, the main techniques for exploiting heterogeneous networks have been deterministic or stochastic approaches [8]. Deterministic coverage allows us to calculate the necessary distance between co-channel cells and avoid interference [9]. Despite this approach's effectiveness, this method sometimes becomes ineffective for highly dense urban scenarios where there are obstacles like building high traffic because of a huge number of users [10; 11]. The deterministic method decreases rapidly due to such high fluctuations of cell load and the presence of skyscrapers that affects the network geometry negatively [12]. Therefore, stochastic geometry was introduced to predict the probabilistic parameters of randomly designed HetNet and the stochastic approach is showing better solutions [13].  
In [14], the authors combined the software-defined networking approach with the small-cell deployments. They provided the concept of multiple TCP connections to ensure link reliability between the vehicles and small-cells. The authors of [15] provided a novel spatial phase coding technique for orthogonal frequency division multiplex (OFDM) systems. Their main object was to minimize inter-cell interference to enhance the reliability of mobile terminals. The results demonstrate that their proposed method reduces the bit-error-rate when compared to conventional techniques. Besides this, the incorporation of multi-antenna massive multiple-input-multiple-output (MIMO) networks is another important area of research for heterogeneous networks [16; 17]. For instance, the authors of [18] consider full-duplex massive MIMO communication in heterogeneous networks and applied self-backhauling technique for small-cell networks.  
Another work [19] consider a 3D MIMO heterogeneous network and perform the trial results. Their measurement shows the promising features of the heterogeneous network when combined with 3D MIMO. From the perspective of performance evaluation, the authors of [20] investigated the outage performance of heterogeneous networks. [PERSON] et al. in [21] aims to improve the performance of wireless backhaul links in massive MIMO heterogeneous networks. They also study the spectral efficiency of the system and identify the different requirements and connectivity issues of backhaul links. A novel interference alignment technique was proposed by the authors of [22]. They investigate small-cell based heterogeneous networks and identified the problem of inter-cell interference. Their proposed interference alignment technique improves upon the existing baseline approaches. A two-stage device-to-device (D2D) communication technique was proposed by the authors of [23]. They highlighted that the problem of computation resource management could become critical for large-scale heterogeneous networks. Thus, they provided D2D-assisted approach to balance the computation resource in the small-cells which significantly improves the performance of the network. They used a hybrid coordinated beamforming technique for signal transmission. They identified the key outage constraints on the performance of such networks. An energy-efficient and spectral efficient tradeoff for the small-cell backhaul networks was provided by the authors of [24; 25]. The authors claimed that there is a need to find the optimal balancing point between the tradeoff of spectral and energy efficiency. Energy-efficient scheduling techniques were proposedby the authors of [26; 27] for conventional small-cell cellular networks and unmanned aerial vehicle (UAV) assisted small-cell communications [28]. In a similar manner, the user association problem was investigated by the authors of [29]. It was shown that significant performance gains could be obtained by jointly optimizing the resources and associating the users.