Bias-based self-organized cell selections for outdoor open-access picocell networks

Cellular structures are to be enhanced by heterogeneous deployments. One type of such deployments is to add outdoor pico evolved NodeBs (PeNBs), formulating a hierarchical cell structure with macro eNBs (MeNBs). The cell selection in such system is facing challenges, including problems of coverage and cross interference. One method is called cell range expansion (RE), typically in which a common fixed bias value is added to the users´ receiving signal power from PeNBs to adjust their coverage. However, it might not be appropriate to use the same bias for all the PeNBs. This paper focus on the specific bias design. By defining the interfered region, it proposes a mechanism to obtain the average interference suffered by each PeNB. The interference is from MeNBs with sector antennas and other randomly located PeNBs. In the discussion, it is further pointed out that its implementation follows a self-organized manner, with sustainable signalling overhead. Simulation results show that the proposed method achieves much better cell edge performances than those with fixed bias values.