Separating mixed signals includes receiving the mixed signals from signal sources transmitting from a number of cells. A signal source is operable to transmit a source signal, and a mixed signal comprises at least a subset of the source signals. A complex mixing matrix is established from the mixed signals. The complex mixing matrix describes mixing the source signals to yield the mixed signals. The number of cells is estimated from the mixed signals. The mixed signals are separated using the complex mixing matrix and the estimated number of cells.