A simple network-listening based synchronization for small cells in LTE-Advanced

The layered cell structure, in which a large number of small cells overlay each macro cell to increase network capacity is attracting much attention. In the layered cell structure, eICIC is essential to avoid the interference between the macro cells and the small cells when co-channel deployment is used. Because eICIC conducts interference coordination in the time domain, accurate timing synchronization is required between the macro cells and the small cells. Although GNSS-based or packet-based timing synchronization is effective in many cases, GNSS-based synchronization cannot be used indoors and the packet-based approach may not work depending on the backhaul network configuration. Network-listening based synchronization is attracting much attention recently as an alternative to the above methods. It uses just the macro-cell signal to realize accurate synchronization. However, the loop-back signal from the small-cell eNB itself interferes the reception of the macro-cell signal. In this paper, we propose a simple synchronization method that eliminates loop-back interference, and clarify that it achieves accurate synchronization by computer simulations.