Mitigating Uplink interference in femtocell networks with Physical Layer Network coding

The challenge of mitigating the Uplink (UL) interference in a two-tier heterogeneous network could be significantly improved by employing Physical-Layer Network coding (PNC) at a Home NodeB (HNB). This paper makes a case for a macrocell femtocell overlay network that utilizes PNC to mitigate the UL interference at the HNB. In closed subscriber group (CSG) UL information exchange, a Macrocell User Equipment (MUE), especially situated at coverage area´s edge of a macrocell nodeB (MNB), creates interference that could make the received signal-to-interference-plus-noise-ratios (SINR) of the neighboring HNB to fall below the acceptable threshold. In a bid to ensure that the Service Quality (QoS) of femtocell and macrocell users are guaranteed, we propose to use PNC at the HNB by taking advantage of both the signals from the MUE and the Home User Equipment (HUE), rather than considering the signal from the MUE as interference. The paper develops the analytical expression of outage probability in closed-form, or equivalently the cummulative distribution function (CDF) for the received SINR of the proposed system is provided. Our results show that PNC is suitable for interference mitigation in femtocell network and it provides significant gain over the traditional scheme.