In this paper, the impact of varying path loss exponent (PLE) on user association probability, decoupled uplink coverage probability as well as decoupled uplink average spectral efficiency in downlink uplink decoupled (DUDe) multi-tier heterogeneous networks, is investigated. We investigate the effect of the difference in path loss exponents in both macro and small cell environments over uplink network performance. It is assumed that the mobile user connected to the macro base station experience different path loss exponent as compared to when connected to small base station. It is observed that the difference of path loss exponents in both cases has significant effect on the user association probability, decoupled uplink coverage probability as well as decoupled uplink average spectral efficiency. Moreover, in order to further support key findings and make sound comparison between coupled and DUDe performance in varying PLE environment, generalized analytical expressions for coupled association probabilities, along with coupled uplink coverage probability and coupled uplink average spectral efficiency have been derived. The analytical results evaluated in this paper are compared with the computer simulation and found in good agreement. Our analysis shows that decoupling technique performs suboptimal for cases where the environments around macro and small base stations are different with respect to each other. The work explained in this paper highlights the limitation of applying DUDe technique in realistic conditions where the PLEs of cellular tiers are not exactly equal to one another.

本文研究了下行链路去耦（DUDe）多层异构网络中变化的路径损耗指数（PLE）对用户关联概率，解耦的上行链路覆盖概率以及解耦的上行平均频谱效率的影响。我们研究了在宏小区和小型小区环境中，路径损耗指数差异对上行链路网络性能的影响。假设连接到宏基站的移动用户与连接到小型基站的移动用户相比经历不同的路径损耗指数。可以看出，两种情况下路径损耗指数的差异对用户关联概率，解耦的上行链路覆盖概率以及解耦的上行链路平均频谱效率均具有显着影响。此外，为了进一步支持关键发现并在变化的PLE环境中进行耦合和DUDe性能之间的合理比较，已经导出了耦合关联概率，耦合上行链路覆盖概率和耦合上行平均频谱效率的广义分析表达式。将本文评估的分析结果与计算机仿真进行比较，发现吻合良好。我们的分析表明，在宏基站和小型基站周围的环境彼此不同的情况下，去耦技术的效果不佳。本文解释的工作突显了在实际条件下应用DUDe技术的局限性，在这种情况下，蜂窝层的PLE之间并不完全相等。