Design and Implementation of Initial Cell Search in 5G NR Systems

The initial cell search plays an important role during the process of downlink synchronization establishment between the User Equipment(UE) and the base station. In particular, the uncertainty of the synchronization signals on the frequency domain and the flexibility of frame structure configuration have brought great challenges to the initial cell search for the fifth-generation(5G) new radio(NR). To solve this problem, firstly, we analyze the physical layer frame structure of 5G NR systems. Then, by focusing on the knowledge of synchronization signals, the 5G NR cell search process is designed, and the primary synchronization signal(PSS) timing synchronization algorithm is proposed, including a 5G-based coarse synchronization algorithm and conjugate symmetry-based fine synchronization algorithm. Finally, the performance of the proposed cell search algorithm in 5G NR systems is verified through the combination of Digital Signal Processing(DSP) and personal computer(PC). And the MATLAB simulation proves that the proposed algorithm has better performance than the conventional cross-correlation algorithm when a certain frequency offset exists.

A novel cell search scheme for OFDM cellular systems

A novel cell search scheme for OFDM cellular systems is proposed. It is based on one OFDM symbol with several identical slots as preamble, the time domain repetition structure of which can be utilized to accomplish OFDM timing/frequency synchronization. The cell ID is comprised of two parts: a sub-carrier mask index g and a sequence index x. Each sub-carrier mask activates or deactivates some of the sub-carriers, after which a differentially coded sequence is loaded on pairs of the adjacent active sub-carriers. The user equipment (UE) recognizes the mask with index g via power detection of the received frequency domain signal. Then it estimates the index x from differential demodulation followed by detection of the frequency domain se-quence. In order to improve the performance, a method of jointly estimating g and x is devised. Simulation results showed that the proposed scheme is able to support a very large number of cell IDs while maintaining a good performance even in bad multi-cell environment.

A robust symbol timing strategy for cellular systems

In cellular systems,establishing the initial symbol timing of potential preambles is the first step of a cell search.The envelope fluctuation of the downlink signal hinders the successful timing of conventional symbol timing methods.To solve this problem,a hybrid timing strategy is proposed with two novel detectors,namely the normalized replica-based detector and normalized differential detector.The strategy first detects all potential preambles via the normalized replica-based detector and then employs the normalized differential detector to verify the target preamble,which comes from the target cell and has the highest power.The strategy is unaffected by envelope fluctuation and has computational complexity comparable to that of conventional methods.Simu-lations and real-data tests show that the hybrid timing strategy is robust and practical for initial symbol timing.

Cell Search Algorithm in Beyond 3G Systems

The downlink frame structure for beyond 3G mobile communication systems is presented. Beyond 3G systems utilize the OFDM technique. However, a problem encountered in OFDM is that channel dispersion destroys orthogonality between carriers, caushag inter-symbol interference. It is also sensitive to high peak to mean power ratio （PAPR）. Therefore it spends much time on obtaining frequency, time, and frame synchronization. This paper proposes to add a frame synchronization channel in the time domain to overcome the shortcoming of OFDM. As transmitter diversity improves the system performance, beyond 3G systems employ space-time block coded （STBC）. Fast cell search algorithm including slot synchronization, frame synchronization and cell ID identification is then discussed, which is based on the frame synchronization channel in transmitter diversity systems. Detection and false alarm probabilities in AWGN and Rayleigh channels are analyzed, and the mean acquisition time is obtained. Computer simulations are conducted to evaluate the performance of the cell search algorithm under different channel conditions.

Robust frame synchronization method for FDD-LTE systems

The primary synchronization signal and the secondary synchronization signal are respectively used to fulfill the subframe and frame synchronization in the long term evolution （LTE） systems. Based on the assumption that the channel frequency response of the primary synchronization signal symbol is nearly the same as that of the secondary synchronization symbol in frequency division duplex-LTE （FDD-LTE）, a new synchronization method is proposed. The frame synchronization success probability is simulated in different wireless channel models and the Mento-Carlo method is used in the simulation. Simulation results show that if the LMMSE channel estimation is adopted, the proposed method is robust at a low signal noise ratio （SNR） scenario and works well when cartier frequency offset and fast Fourier transform （FFT） window timing offset are considered in practical applications. The frame synchronization success probability can still exceed 99% with an SNR of 0 dB when the maximum Doppler shift is very large, which means that this robust frame synchronization method can be applicable in most mobile situations. Simulation results also show that the success probability of the proposed frame synchronization method is higher than that of the method which fulfills the frame synchronization through correlating the received secondary synchronization symbol with local sequences in practical applications.

Research and simulation on synchronization algorithm of PSS in a 5G system based on block cross-correlation

In response to the downlink synchronization requirements of the user equipment(UE)or third-party radio equipment in fifth-generation(5G)mobile communication systems,a synchronization algorithm of primary synchroni-zation signal(PSS)was designed and developed in the 5G system based on block cross-correlation.According to the new characteristics of the 5G synchronization channel and broadcast channel,starting from the traditional downlink synchronization algorithm of long-term evolution(LTE),the detection performance of the algorithm under a low signal-to-noise ratio(SNR)is improved by introducing an incoherent accumulation,and the new scheme of joint coarse frequency offset estimation is used to improve the frequency offset estimation performance.Finally,the performance of the proposed synchronization algorithm is verified by conducting a simulation on a 5G downlink simulation platform based on MATLAB software.Simulation results show that the improved downlink synchronization algorithm has stable performance in the tapped delay line-C(TDL-C)and additive white Gaussian noise(AWGN)channels with large frequency deviation and low SNR.

Effect of Chitin Treatment on Softening of Actinidia arguta

[Objectives] This study was conducted to discuss the effect of chitin treatment on softening of Actinidia arguta Huanyou No. 1 as the test material.[Methods]Huanyou No. 1 was sprayed with chitin,and the changes of some physiological and biochemical indexes in fruit softening were investigated. [Results]Chitin treatment significantly improved single fruit weight,increased soluble solid content,but decreased titratable acid content and significantly reduced the content of cellulose and hemicellulose; and the chitin treatment significantly inhibited the breakdown of pectin,cellulose and hemicellulose,and inhibited the activities of PG enzyme and β-Gal enzyme. [Conclusions] Chitin spray treatment could increase the yield of A. arguta,and improve its quality and storage property.

Cell search scheme for long-term evolution of TD-SCDMA system

Cell search is an important aspect for 3G long-term evolution （LTE）. This article deals with cell search in the time-division-synchronou code-division multiple access （TD-SCDMA） LTE system. On the basis of the synchronization channel （SCH） and cell specific reference symbols （CSRSs）, the proposed cell search procedure includes five stages： frame detection and coarse timing, coarse carrier frequency offset （CFO） estimation, fine timing, fine CFO estimation, and cell identification. The key features of the proposed method are as follows： first, the neighboring three cells＇ CSRSs are frequency division multiplexed （FD） to mitigate inter-cell interference. Second, the frequency domain differential cross-correlation, computed from CSRSs are maximally ratio combined for cell identification. Finally, the large set Kasami sequences are quadrature phase shift key （QPSK） modulated to be cell specific sequences （CSSs）, to support a large number of target cells. Simulations show that the FD method is better than the code division multiplexed （CD） method.

Cell search algorithms for the 3G long-term evolution

This article presents downlink initial synchronization and cell identification algorithms for long term evolution （LTE） of third-generation （3G） mobile communication systems, which are based on synchronization channel （SCH） and cell specific pilot symbols, respectively. The key features of the proposed scheme are： it can improve performance of the frequency synchronization through oversampling of the SCH, it can support a large number of target cells by modulating a cell-specific pilot sequence over two symbols within a subframe, and it can guarantee cell identification performance by maximally ratio combining the frequency domain differential cross-correlation. Simulations show that the proposed scheme has a potential use in 3G LTE.

Dual-CRC polar codes and dual-SCFlip decoding algorithm for cell search in 5G system

Polar codes become the coding scheme for control channels of enhanced mobile broadband(eMBB)scenarios in the fifth generation(5 G)communication system due to their excellent decoding performance.For the cell search procedure in 5 G system,some common information bits(CIBs)are transmitted in consecutive synchronization signal blocks(SSBs).In this paper,a dual-cyclic redundancy check(dual-CRC)aided encoding scheme is proposed,and the corresponding dual-successive cancellation flip(dual-SCFlip)algorithm is given to further improve the performance of polar codes in the low signal-to-noise ratio(SNR)environment.In dual-CRC aided encoding structure,the information bits of polar codes in different transmission blocks add cyclic redundancy check(CRC)sequences respectively according to CIBs and different information bits(DIBs).The structure enlarges the size of CIBs to improve the block error ratio(BLER)performance of the system.The dual-SCFlip decoder can perform bit flip immediately once CIBs is decoded completely,and then decode DIBs or terminate decoding in advance according to the CRC result,which reduces the delay of decoding and mitigates the error propagation effect.Simulation results show that the dual-CRC aided encoding scheme and dual-SCFlip decoder have significant performance improvement compared to other existing schemes with low SNR.