Abstract
The initial process of identifying any available base station (BS) by a user equipment (UE) that wants to communicate is termed as cell search. To ensure a reliable communication, any UE has to be synchronized with the BS both in time and frequency domains. Cell search process is said to be complete once cell ID associated with long-term evolution (LTE) BS is decoded successfully. This paper presents a series of cell search and synchronization algorithms, which efficiently estimated time and frequency offsets as well as cell ID. The synchronization signals present in LTE, namely, primary synchronization signal (PSS) and secondary synchronization signal, that carry cell ID are critically exploited in the algorithms. The aforementioned algorithms are classified into two modules, namely, module I and module II, based on their computation complexity.In module I, a cyclic prefix (CP)-based maximum likelihood (ML) estimator is employed to obtain a coarse estimate of time and fractional frequency offset; however, the estimates are refined using synchronization signals. A joint estimation of timing, integer frequency offset (IFO), and PSS ID (sector ID) is carried out in module II. Both the modules operate on the cross-correlation approach of PSS with the received signal for obtaining timing and sector ID. IFO as a part of module II is detected from a finite hypotheses set using synchronization signals. Extensive simulations are carried out on a time-varying frequency-selective channel to analyze the performance of the algorithms.
Highlights
Third generation partnership project (3GPP) has developed long-term evolution (LTE) technology to achieve high data throughput and better spectrum utilization
user equipment (UE) starts the cell search process without any prior information related to LTE base station (BS)
International telecommunication union (ITU) has developed few channel models depending on the carrier frequency [14]. 3GPP further extended the ITU channel models to reflect the LTE channel characteristics at around 2.5 GHz carrier frequency and 20 MHz bandwidth
Summary
Third generation partnership project (3GPP) has developed long-term evolution (LTE) technology to achieve high data throughput and better spectrum utilization. Supporting varied range of bandwidths from 1.4 to 20 MHz makes this technology more flexible. LTE aims at data rates up to 100 Mbps in down-link (DL) and 50 Mbps in up-link (UL) with a bandwidth (BW) of 20 MHz excluding carrier aggregation and spatial multiplexing [1]. Orthogonal frequency division multiplexing (OFDM) makes a perfect choice in the DL because of its competence in dealing channel frequency selectivity and its flexibility to handle different channel BWs. Single-carrier frequency division multiplexing (SC-FDM) is adopted in UL to reduce the peak to average power ratio (PAPR). A cyclic prefix (CP) is inserted in every OFDM and SC-FDM symbol. LTE base station (BS) supports normal and extended CP to combat delay spreads
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