Femto-to-Macro Control Channel Interference Mitigation via Cell ID Manipulation in LTE

With considerable interest being garnered in recent years, femto-cells are seen as a major contender to significantly increase capacity and fill coverage holes in 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) cellular networks. User- deployed femto-cells, each exclusively serving a set of registered users and sharing the same frequency spectrum as the overlay macro-cells are already defined in 3GPP specifications. Such a co- channel and random deployment of femto-cells can cause heavy downlink (DL) interference to a user equipment (UE) in the vicinity of one or more femto-cells and not belonging to their closed subscriber groups (CSGs). In this paperwe focus on protection of the most important LTE DL control channel, known as the physical control format indicator channel (PCFICH). Failure to decode this channel correctly results in the loss of the subsequent subframe. A technique which mitigates femto-to-macro PCFICH interference by carefully manipulating the physical cell identity (PCI) of the aggressor femto-cell is presented. It is shown that employing this technique results in a significant improvement of PCFICH effective signal- to- interference-plus-noise ratio (SINR) without the need for any additional network signaling.