Throughput and fairness of femtocell users in OFDM macrocell-femtocell networks

While femtocell network enhances throughput and coverage, it also introduces cross-tier interference. In the uplink, to protect existing macrocell users (MUs), the interference accumulated at the macrocell base station (MBS) by femtocell users (FUs) should be limited. Due to variable distances between a femtocell base station (FBS) and the MBS, FU associated with the FBS closer to the MBS will impose more interference to the MBS due to smaller path loss. To meet the interference constraint at the MBS, the FU closer to the MBS has a stricter transmission power limit than the FU further away from the MBS. In this situation, fairness issue arises among the FUs. In this paper, we consider an uplink power allocation problem for orthogonal frequency division multiplexing (OFDM) transmissions under the rise-over-thermal constraint at the MBS and evaluate throughput and fairness of the FUs. Our simulation results indicate that the instantaneous channel knowledge between the FUs and the MBS increases throughput and fairness of the FUs compared to the average channel knowledge. In addition, wall loss is beneficial in improving the throughput and fairness as it suppresses interference from FUs to the MBS.