Performance of orthogonal and co-channel resource assignments for femto-cells in long term evolution systems

The femto-cell base station (BS) is presented as a promising consumer electronic device to provide the wireless multi-medium services in the family or office environments. Radio resources allocated to femto-cell and macro-cell users should be made orthogonal to reduce interferences. The radio resources for the femto-cell and macro-cell users can also be reused to improve spectrum efficiency at the expense of increasing the cross-layer interference. This study investigates the uplink interference and derives the exact cumulate distribution function (CDF) expressions for the signal-to-interference ratio distributions in these two radio resource scenarios. Their throughputs are expressed according to the derived CDF expressions. It is shown that the simulation results match to the theoretical analysis very well, illustrating that the radio resource allocation in these two scenarios is related strictly to the path loss exponent and the number of femto-cells in a macro-cell. Furthermore, the average distance between the macro-cell and the femto-cell BSs has significant impact on the user performance of femto-cells.