Capable of significantly reducing cell size and enhancing spatial reuse,network densification is shown to be one of the most dominant approaches toexpand network capacity. Due to the scarcity of available spectrum resources,nevertheless, the over-deployment of network infrastructures, e.g., cellularbase stations (BSs), would strengthen the inter-cell interference as well, thusin turn deteriorating the system performance. On this account, we investigatethe performance of downlink cellular networks in terms of user coverageprobability (CP) and network spatial throughput (ST), aiming to shed light onthe limitation of network densification. Notably, it is shown that both CP andST would be degraded and even diminish to be zero when BS density issufficiently large, provided that practical antenna height difference (AHD)between BSs and users is involved to characterize pathloss. Moreover, theresults also reveal that the increase of network ST is at the expense of thedegradation of CP. Therefore, to balance the tradeoff between user and networkperformance, we further study the critical density, under which ST could bemaximized under the CP constraint. Through a special case study, it followsthat the critical density is inversely proportional to the square of AHD. Theresults in this work could provide helpful guideline towards the application ofnetwork densification in the next-generation wireless networks.
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