When the user equipment (UE) is turned on, it first needs to perform an initial cell search procedure before it can communicate with the base station (BS). However, this procedure must deal with the initial time and frequency synchronization and search for the appropriate home BS for services. In conventional cell search methods, the entire cell search process is carried out on the UE, where the computational requirement can lead to additional overhead and power consumption of the UE. Therefore, aiming to help UEs offloading their overhead to BSs, we in this paper propose a novel cell search method, called Network Resolved and Mobile Assisted Cell Search, which can achieve our goal by letting the BSs be the main performers for deciding the appropriate BSs for connection and letting UEs only be the assistants of the cell search process. The implementation details and analysis of the proposed cell search approach are provided along with the numerical simulations. Results show that our proposed cell search not only can offload the computational overhead, but it also outperforms the conventional code-based cell search approach in terms of the cell search error probability with similar overall network energy consumption.INDEX TERMS initial cell search, cellular systems, multipath division multiple access (MDMA), universal pilot, base station.

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Cell search procedure is an essential and critical process in an early stage when the user equipment (UE) is powered on. It mainly comprises symbol and frame timing synchronization, frequency offset compensation, and base station (BS) identification. Among the current exiting 3G, 4G and 5G mobile networks, the UE completes the initial cell search based on different code sequences. In this paper, we investigate and compare two kinds of cell search methodology. Tone-based and code-based methods are explored for massive antenna systems. The detailed description and analysis are offered for two approaches. Simulation results indicate that the tone-based cell search not only possesses stable performance with respect to path numbers but also outperforms the code-based one in general channel realizations in terms of cell search error probability. The results suggest that the tone-based cell search could be used for 5G communication systems.INDEX TERMS initial cell search, tone-based cell search, 5G, cellular systems, massive antennas