Uplink Timing Misalignment in Open and Closed Access OFDMA Femtocell Networks

We focus on an uplink network composing of femtocell access points (FAPs), macrocell users (MUs) and a macrocell base station (MBS) employing orthogonal frequency division multiple access (OFDMA) signaling. Synchronization of MUs at the MBS results in asynchronous signal arrivals at the FAPs which may induce intercarrier interference (ICI). Given a fixed distance between an FAP and the MBS, we derive a closed-form expression for the probability of an MU causing ICI to the FAP. Then, we extend this to obtain the probability of an open and closed access FAP experiencing ICI in the presence of a fixed number of MUs, and the average number of open and closed access FAPs experiencing ICI.