Tradeoffs of Small Cell Coverage Autoconfiguration in Co-Channel WCDMA Cellular Networks
22 February 2012
In this study, we examine the tradeoffs related to the problem of coverage auto-configuration of small cells that are deployed in a traffic hotspot of a WCDMA network. We assume open access small cells that operate in the same frequency channel as the hosting/neighboring macro cells. We show that the downlink and uplink characteristics of the hotspot users respond antagonistically to the variations of the small cell coverage - the offloading of the macro-cell users by the small cell improves the overall downlink transmission quality, but reduces the achievable uplink capacity of the small cell. It is also shown that the uplink power control stability may require the small cell to maintain the coverage within traffic-dependent minimum/maximum limits which complicates any autonomous search for optimum partitioning of the small cell power budget. As a conclusion, we discuss equilibrium states of the identified tradeoffs whose achievement can represent an optimality criterion for automatic coverage configuration of small cells. Owing to a fundamental theoretical impossibility to represent variables related to the uplink stability by using closed-form expressions, our analysis numerically evaluates a 3GPP-compliant system model.
