The user-centric cooperative transmission provides a compelling way to alleviate frequent handovers caused by an ever-increasing number of randomly deployed base stations (BSs) in ultra-dense networks (UDNs). This paper proposes a new user-centric cooperative transmissions-based handover scheme, i.e., the group-cell handover (GCHO) scheme, with the aim of reducing the handover rate in UDNs. In the proposed scheme, the boundary of the cooperating cluster depends on the distance among the user equipment (UE) and cooperating BSs. The new scheme captures the dynamicity and irregularity of the cooperating cluster topology resulting from randomly distributed BSs. Based on stochastic-geometry tools where BSs locations are modeled as the Poison point process (PPP), we derive an analytical expression of the handover rate for the UE with an arbitrary movement trajectory. Furthermore, a GCHO skipping (GCHO-S) scheme is proposed to minimize the handover cost, i.e., the percentage of time wasted in handover signaling in user-centric cooperative transmissions scenarios. The numerical results show that the GCHO scheme decreases the handover rate by 42.3% and 72.7% compared with the traditional single BS association and fixed-region cooperative network topology handover approaches, respectively. Moreover, under the same group-cell size and constant velocity, the GCHO-S scheme diminishes the handover cost by 50% against the GCHO scheme.
翻译:以用户为中心的合作传输为减轻超高级网络中随机部署基站数量不断增加造成的频繁交接提供了令人信服的办法。本文件提出了一个新的以用户为中心的基于合作传输的交接办法,即群体-细胞交接办法,目的是降低UDN的交接率。在拟议办法中,合作集群的边界取决于用户设备(UE)和合作型BS之间的距离。新办法反映了随机分布的BS产生的合作集群表层结构变化和不规则性。基于以BS为制模范的Stochatical-地质测量工具,即以毒点进程(PPPPP)为模型,我们对UE的交接率进行了分析性表示。此外,还提议了GCHO(GCHO-S)跳过计划,以尽量减少移交费用,即以用户为中心的合作传输方式交接信号时浪费的时间比例。 数字结果显示,与GCHO-HO-S的交接办法相比,与GCHO-72号区域平流率比,与GCHO-CHO-C-C-72号速度模式的交接合率分别减少了与GCHO-72的固定比率。