A Tutorial on 3GPP Initial Cell Search: Exploring a Potential for Intelligence Based Cell Search

This tutorial guides the reader through the open literature on the aspect of Initial Cell Search (ICS) in both Code Division Multiple Access (CDMA) and Orthogonal Frequency Division Multiple Access (OFDMA) systems perspectives with a special focus on the DownLink (DL), where the ICS represents the very first operational stage of commercial mobile station modem's always-on mobility. There is no comprehensive up-to-date tutorial of the ICSs encompassing 3G, 4G, and 5G systems. Hence, we review the ICS-related operations which have been proposed for Wideband CDMA (W-CDMA), Time Division-Synchronous CDMA (TD-SCDMA), Long Term Evolution Frequency Division Duplex (LTE-FDD), and Time Division LTE (TD-LTE) from the point of view of 3rd Generation Partnership Project (3GPP) standard and implementation. In the case of TD-SCDMA, there is no in-depth literature illustrating the details of ICS. Therefore, this tutorial aims to fill the related gap in the literature. As an evolution from the operational systems, we also shed light on the ICS being employed in New Radio (NR) system operating at sub-6 GHz and provide insight into interesting and challenging technical issues in millimeter-Wave spectrum bands, which is an ultimate foundation to be deployed in the full-scale NR system. Furthermore, we exemplify entire cell search operations over diverse spectrum bands and elucidate intelligent ways of designing multi-mode mobile station modem in a systematic manner. A taxonomy diagram also classifies three main targets constituting ICS procedures in 3G, 4G, and 5G systems. It is expected that this tutorial is beneficial not only for academic researchers but also for practical modem development engineers.