É NERGIE ET RADIOSCIENCES Inter - cell Interference Coordination for Backhaul - aware Small Cell DTX

Introduction Europe targets to develop low-carbon and energy efficient technologies through the 2020 roadmap. On the other hand, forecast on ICT industry states an exponential increase in data traffic going through wireless cellular networks. A dense deployment of small cells (SCs) is necessary to satisfy the future traffic requirements, which results in a fast increase of energy consumption with more challenging operational costs for the mobile industry. Hence, the wireless community has a tremendous interest for improving the energy efficiency (EE) at system level and there is a large effort for finding innovative solutions in order to improve the network sustainability. Current activities in the domain of the green wireless networks are mainly focusing on four research axes [1]: the definition of models and tools to evaluate the EE of current Radio Access Network (RAN) and backhaul (BH), the investigation of new adaptive hardware solutions, the design of innovative multi-layer architectures based on dense SCs deployment, and the proposal of flexible management schemes that adapt the network parameters with respect to service load variations. Discontinuous transmission (cell DTX) is a well-known solution to improve the network EE by dynamically deactivating most of the eNB hardware components when data is absent in a given transmission time interval [2]. Cell DTX jointly combined with buffering and cooperative transmissions can achieve additional gains by exploiting spatial diversity and the energy-delay trade-off [3]. More recently, we have shown that by deploying a SDN-like controller, it is possible to orchestrate both the SCs and the corresponding BH facilities, which have a large impact on the overall network energy consumption [4]. However, in this context, spikes of interference have been observed when two neighboring SCs are activated simultaneously, and large packet error rate losses can be perceived in scenarios characterized by high data rate requirements. Therefore, in this study, we present an architecture for an Inter-cell Interference Coordination (ICIC) controller to manage backhaul-aware SC DTX in dense heterogeneous wireless networks. This paper is organized as follows: in the first section the need for joint RAN and backhaul optimization mechanisms is discussed. Afterwards, the proposed ICIC framework for Backhaul-aware cell DTX is presented in Section 2. In Section 3 we introduce the used reinforcement learning mechanisms. In Section 4, we provide more detail on the architecture of the proposed scheme. Finally, in Section 5, we show preliminary results that confirm the advantages of our solution.