Open, Closed, and Shared Access Femtocells in the Downlink
A fundamental choice in femtocell deployments is the set of users which are allowed to access each femtocell. Closed access restricts the set to specifically registered users, while open access allows any mobile subscriber to use any femtocell. Which one is preferable, depends strongly on the distance between the Macrocell Base Station (MBS) and femtocell. The main results of this paper are lemmas which provide expressions for the Signal-to-Interference-plus-to-Noise Ratio (SINR) distribution for various zones within a cell as a function of this MBS-femto distance. The average sum throughput (or any other SINR-based metric) of home users and cellular users under open and closed access can readily be determined from these expressions.