LTE femtocell network categorized as one of small cell technologies will play an important role in future 5G networks due to the fact that it not only can expand the coverage of wireless communication systems but also can increase frequency reuse. With the growth of “Internet of Thing” (IoT), the data volume will increase explosively in the future. Hence the need to deploy femtocell is stringent. However, the growing deployments of femtocell base stations (FBSs) have brought a serious issue of inter-FBS interference (also referred to as co-tier interference) due to their easy and convenient installations. In this article, we propose a systematic approach to reduce FBS co-tier downlink interference under the scenario that FBSs are densely deployed in an environment. Power control for an FBS is performed when the number of warning messages issued from other femtocell User Equipment (FUE) is greater than a threshold for a typical distributed power control scheme. However, it will also reduce the Signal to Interference and Noise Ratio (SINR) of the FUEs connected to the FBS as well. Therefore, it will reduce the total capacity. In our proposed Loading Aware Green Power Control (LAGPC) scheme, an FBS performs power control only when the number of FUEs connected to other FBSs interfered by the FBS is greater than the number of FUEs served by this FBS. In order to solve the cell edge or cell border effect, a directional antenna assisted is proposed. Our proposed scheme has been validated through simulations that it could effectively reduce co-tier downlink interference in shared-spectrum femtocell environments, thereby boosting system performance by 32.4 and 45.9% under the scenarios with 300 FUEs and 400 FUEs to be served respectively on average. In order to solve the border effect, i.e. the FUE resides on the border of two FBSs, beamforming (BF) and Near-Far effect are proposed. Our rough studies show that BF can boost the performance of any proposed scheme by 120% at least at cost of higher device cost as well as lager header overheads in PHY layer.
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