A Cell Identification Performance Improvement in Co-Channel Heterogeneous Cellular Networks with Cell Range Expansion

Recently, data traffic has been explosively increasing in cellular mobile communication systems due to the prevalence of smart phones. A co-channel heterogeneous cellular network overlaid with pico-cells (HetNet), in which pico-cell base stations (BSs) with low transmission power are placed at the hot spot area of a macro-cell base station with a high transmission power, has been receiving attention in order to deal with the increasing traffic. In general cellular mobile communication systems, synchronization signal (SS) symbols for the initial serving-cell identification and for the neighboring-cell identification at user equipments (UEs) are periodically transmitted from base stations (BSs). For HetNet, Cell Range Expansion (CRE), in which a bias value is used for the reference signal received power from pico-cell BSs, has been investigated as a promising approach to offload the traffic into the pico-cell from the macro- cell. Unfortunately, there is an issue that the cell identification delay at pico-cell area increases with the CRE bias value, since larger CRE bias value suffers from larger interference from macro-cell base stations (Macro-BSs) at the received SS symbols transmitted from pico-cell base stations (Pico-BSs) in the pico-cell area expanded by CRE. This paper investigates the cell- identification performance improvement possible with transmission power coordination of the SS symbols for HetNet with CRE. Then, it evaluates the cell-identification characteristics of a cell search operation based on the hierarchical SS structure of 3GPP LTE/LTE-Advanced, and also clarifies the effectiveness of the transmission power coordination of the SS symbols in terms of the pico-cell identification for HetNet with CRE.