With huge number of smart gadgets and wireless devices being interconnected to each other, the demand for very high data bandwidth is becoming critically challenging. With such density of nodes inside wireless networks, providing high-quality service as well as wide coverage in indoor environment is a real challenge, which is due to the limited radio frequency and intense interference between nodes. As a one way to solve such problem and improve indoor service quality, femtocells have been introduced as an extension to the existing macrocell stations. Although femtocell is a promising technology, the pervasive deployment of huge number of femtocells without very tight network planning as well as coverage strategy may worsen the problem and degrade the service quality. One important problem that needs to be addressed when deploying femtocell technology in heterogenous networks (HetNets) is mitigating the various types of cross-tier and cotier interferences in between wireless cells. This study investigates the effect of unplanned ultradensity femtocell deployment in the downlink performance of two-tier heterogeneous networks in urban area based on LTE system. Instead of deploying femtocells one by one, grids of size either () or () of neighboring femtocell will be deployed inside each macrocell sector area. The simulation results show that femtocell deployment improves overall average user throughput in case of low and medium density scenarios. However, for ultradensity scenario, there is no enhancement in terms of fairness and throughput. The results confirm that this leads to high degradation for macrocell and femtocell user performance due to the severe interference between macrocells and femtocells, as well as among neighboring femtocells in each grid.

中文翻译：

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Femtocell Ultradense 部署对 LTE 异构网络下行链路性能的影响

随着大量智能设备和无线设备相互连接，对极高数据带宽的需求正变得极具挑战性。由于无线网络内部节点的密度如此之高，在室内环境中提供高质量的服务和广泛的覆盖是一个真正的挑战，这是由于有限的无线电频率和节点之间的强烈干扰。作为解决此类问题和提高室内服务质量的一种方式，已引入毫微微蜂窝作为对现有宏蜂窝站的扩展。尽管 femtocell 是一项很有前途的技术，但在没有非常严格的网络规划和覆盖策略的情况下大量部署 femtocell 可能会使问题恶化并降低服务质量。在异构网络 (HetNets) 中部署毫微微蜂窝技术时需要解决的一个重要问题是减轻无线蜂窝之间的各种类型的跨层和同层干扰。本研究调查了未规划的超密度 femtocell 部署对基于 LTE 系统的市区两层异构网络下行链路性能的影响。不是一个一个地部署毫微微蜂窝，而是大小的网格（)或 ()的相邻毫微微蜂窝将部署在每个宏蜂窝扇区区域内。仿真结果表明，在中低密度场景下，毫微微蜂窝部署提高了整体平均用户吞吐量。但是，对于超密度场景，在公平性和吞吐量方面没有任何增强。结果证实，由于宏蜂窝和毫微微蜂窝之间以及每个网格中相邻毫微微蜂窝之间的严重干扰，这导致宏蜂窝和毫微微蜂窝用户性能的严重下降。