## 1 Introduction
In device-assisted-networking for cellular greening (DANCE) scheme, a macro cell BS manages the control signal of UEs and a small cell controller activates or deactivates the small cell BSs when the traffic load varies to optimize the number of activated/deactivated small cell BSs [17]. In [18], the authors propose a joint BS on/off switching and user association algorithm in order to maximize the energy efficiency, based on the time- and space-dependent traffic load in massive MIMO heterogeneous networks. In [19], the authors change the on/off states of small cell BSs dynamically based on UE distribution. In uniform UE distribution, small cell BSs are turned off with the ascending order of the distance with the macro cell BS. In non-uniform UE distribution, a joint location and user density based scheme is proposed and near-optimum solution is obtained. In [20], the authors discuss the technical challenges of BS on/off switching in 5G systems, summarize the state of the art on BS on/off switching, and present challenges and open problems. In [21], the authors introduce four different sleep modes to small cell BSs depending on the consumed energy levels. Then, they formulate an optimization problem for energy efficiency maximization based on either a random sleeping or a strategic sleeping policy for small cell BSs. In [22], the authors analyze the impact of the sleeping of BSs on energy efficiency and user-perceived delay based on three wake-up schemes such as single sleep, multiple sleep, and N-limited schemes. Then, they formulate an optimization problem for delay-constrained energy-optimal BS sleeping policies and analyze the tradeoff between energy saving and mean delay. In [23], the authors analyze the tradeoff between energy consumption and grade of service degradation when the different sleeping patterns of BSs are considered. In [24; 25; 26; 27; 28], energy efficiency of BSs shared by multiple operators is analyzed. In [24], in order to reduce the energy consumption and operational cost in cellular networks, network sharing is considered, in addition to the switching off of BSs. The authors introduce the concept of intra-cell roaming, where UEs of a specific mobile network operator are roamed to another BSs operated by other mobile network operators, and the operator turns off its BSs. Then, they propose a distributed game theoretic BS switching off scheme and analyze the energy saving and cost saving. In [25], the authors propose a cooperative BS switching off scheme, where macro cell BSs and small cell BSs are turned off when the traffic load is low and UEs are served by BSs operated by other mobile network operators in order to guarantee the quality of service. In [26], the authors propose game-theoretic approaches, i.e., pricing decision game and user association game, based on the relationship between roaming price and user association in multi-mobile network operator environment. Then, they reveal that significant energy saving is achieved in the proposed approaches. In [27], the authors propose an auction-based switching-off scheme, by using the fact that network is underutilized if traffic load is low and thus third party small cells can be used to offload its traffic and BSs can be turned off to save power. The proposed scheme consists of a bidding strategy and an auction scheme which maximize the profit and minimizes energy consumption. In [28], the authors propose a game-theoretic infrastructure sharing scheme, where mobile network operators estimate the switching-off probabilities that can reduce their cost and finally equilibrium state is achieved that minimizes the cost of each operator. In [28], an analytical model is developed using voice and data traffic model. Regarding the works on network architecture for a green network, third generation partnership project (3 GPP) proposed the concept of separation of data plane and control plane for 5G networks [29].