Cell splitting is an effective way of implementing network densification in order to boost the capacity of a mobile system. Traditionally, the cell splitting procedure has been carried out in the azimuth dimension. However, another approach known as vertical sectorization has been gaining momentum recently, where the sectors of a conventional cellular system are split vertically instead, creating inner and outer cells by using AAS technology. Then vertical sectorization can use the same communication resources in both inner and outer parts of the cells. Performance of vertical sectorization has been extensively studied in the literature using advanced system simulations. However, field measurements to characterize the actual performance of vertical sectorization with AAS have been scarce so far. In this article, we first identify key issues that may hinder the smooth implementation of commercial cellular systems using vertical sectorization. Then we present the results of a measurement campaign that was carried out to study these limitations and to identify the actual vertical radiation patterns when AAS technology is used. Finally, we reflect on some problems that remain open to make future cellular systems using vertical sectorization with AAS commercially viable.
['Weiliang Xie', 'Qimei Cui', 'Fengyi Yang', 'Qi Bi', 'Yifei Yuan']
Experimental investigation on a vertical sectorization system with active antenna