Cell Search Algorithm Research Articles

Cross-link interference in the 5G cell search procedure: Observation and field experiments for mitigation

This paper presents field experiment results that illustrate the impact of cross-link interference on the cell search procedure in a 5G time division duplex system. We initially show how cross-link interference affects to the cell search procedure from an analytic aspect. An example of an experimental result provided in this paper shows how the user equipment wrongly estimates the symbol timing offset due to cross-link interference. Furthermore, we propose a modified cell search algorithm which is robust against the strong influence of cross-link interference. The proposed modification efficiently suppresses the effects of cross-link interference by applying selective energy normalization to the correlation process. The experimental results show that the modified algorithm can accurately estimate the symbol timing offset with a negligible increment in computation time.

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 complete cell search and synchronization in LTE

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.

Joint Block Sparse Signal Recovery Problem and Applications in LTE Cell Search

We consider the problem of jointly recovering block sparse signals that share the same support set, using multiple measurement vectors (MMVs). We consider the generalized MMV (GMMV) model wherein the different measurement vectors could have been obtained by using different sensing matrices. We study greedy- and convex-programming-based recovery algorithms and theoretically establish their support recovery guarantees. Our results present insights into how the correlation among block sparse signals plays a role in the recovery performance. Next, we consider the problem of cell search in heterogeneous cellular networks (HetNets). With the cell search process, the mobile terminal (MT) acquires synchronization parameters, such as frame timing, residual frequency offset, and the physical-layer identity of a base station (BS), suitable for its connection. In HetNets, due to the increased density of the BS, the MT may receive strong interference from several BSs in its neighborhood. We establish that the problem of cell search in HetNets can be solved by using the GMMV joint block sparse signal recovery framework. We numerically study the performance of the cell search algorithms proposed by using our framework and show that they perform significantly better than the successive interference cancelation algorithm that exists in the literature.

AeroMACS 시스템을 위한 동기화기 설계

In this paper, the performance analysis results of time/frequency synchronization and cell search algorithm are presented for aeronautical mobile airport communication systems (AeroMACS). AeroMACS is based on IEEE 802.16e mobile WiMAX standard and uses the aeronautical frequency band of 5GHz with the bandwidth of 5MHz. The simulation model of AeroMACS is designed and the performance evaluation is conducted with the various airport channel models such as apron (APR), runway (RWY), taxiway (TWY), and park (PRK). The proposed synchronization unit was designed in hardware description language (HDL) and implemented on FPGA. Also, the real-time operation was verified and evaluated using FPGA test system.

Low-Complexity Cell Search Algorithm for Interleaved Concatenation ML-Sequences in 3GPP-LTE Systems

In this paper, we present a low-complexity cell-search algorithm and architecture for secondary synchronization signal in 3GPP-LTE downlink systems. Differential correlations are computed to remove common channel effects so that two sets of synchronization signals can be combined to obtain enhanced detection quality. To achieve low complexity, we further adopt one-bit quantization and exploit the properties of limited offset in the indices of the two maximal-length sequences. The arithmetic complexity of the proposed algorithm is significantly reduced while attaining similar detection performance comparable to the conventional schemes. Finally, hardware architecture of the proposed algorithm is presented to demonstrate feasibility and efficiency in the implementation.

Preamble and Pilot Design with Computationally Efficient Synchronization and Cell Search Algorithms in Cellular OFDM Systems

A computationally efficient initial synchronization technique is introduced in cellular orthogonal frequency division multiplexing downlink systems, which includes symbol timing estimation, frequency offset estimation, frame synchronization, and cell search. Novel preamble and pilot structures are proposed and a simple three-step synchronization scheme is developed based on a variety of practical conditions such as low computational complexity, time-varying frequency selective fading, limited preamble length, low peak-to-average-power ratio, and noncoherent synchronization with no channel estimation. The proposed three-step synchronization is sequentially described as (1) joint timing and frequency synchronization, (2) frame synchronization and preamble pattern identification (ID), and (3) pilot group ID. Simulation results show that the proposed technique nicely works even at low signal-to-interference-and-noise ratio regions.

Implementation of W-CDMA Cell Search on a Highly Parallel and Scalable MPSoC

The performance of the W-CDMA cell search algorithm can be significantly improved using homogeneous general purpose Multi-Processor System-on-Chip (MPSoC) architectures. The application also scales well, as the number of processing nodes increases, allowing practical accelerations to become close to the theoretical maximum. In this work we describe a template MPSoC architecture based on multiprocessor computational clusters, called Ninesilica. Each Ninesilica consist of nine processing nodes based on COFFEE RISC architecture. MPSoC inter- and intra-cluster communication are enabled using hierarchical Network-on-Chip with dedicated point to point and broadcast communication services for better performance. Proposed template has been used to instantiate complete systems with one and four Ninesilica clusters, resulting in MPSoCs with respectively 9 and 36 computational nodes. The MPSoCs have been physically prototyped on a FPGA device, and the W-CDMA cell search algorithm has been mapped on both MPSoC platforms. The four Ninesilica MPSoC can execute W-CDMA in 20.5 ms (at 115 MHz, slow mode implementation) with the total speed-up of 24.3X and 3.3X when compared to a single processing core system and to a single Ninesilica cluster, respectively.

An efficient synchronization signal structure for OFDM-based cellular systems

OFDM has been a widely accepted technology in high rate and multimedia data service systems such as long term evolution (LTE) in the 3rd generation partnership project (3GPP). In this paper, we investigate a synchronization signal structure and corresponding cell search algorithm in the LTE system where two, primary and secondary synchronization signals are employed. We focus on the secondary synchronization signal which possesses two layered scrambling sequences in addition to basic sequences. These scrambling sequences minimize performance degradation in cell search, but incur a high complexity to a mobile station receiver. In this paper, we propose a new secondary synchronization signal structure which does not require additional scrambling sequences while maintaining almost the same performance as the current LTE scheme. We evaluate the performance of the proposed scheme under various channel environments by examining the impacts of multipath fading, frequency offset, and vehicular speed. We also compare the complexity of the proposed scheme with the LTE scheme.

A new preamble-based cell search algorithm for asynchronous MC-CDMA systems

In this paper, we propose a new cell search scheme for asynchronous multi-carrier (MC) CDMA systems. For initial cell search, the proposed scheme contains detection processes for symbol timing, fractional frequency offset, frame timing, cell-specific code group, integer frequency offset, and cell-specific code. In order to accomplish faster cell search by diminishing the effects of noise and interference, a new preamble structure with power-concentrated repeated symbols is proposed and efficient detection algorithms for the above parameters are also proposed. Then, the performances of the proposed cell search algorithms are evaluated in a multi-cell environment with 19-hexagonal cell layout. The proposed method can search the desired cell site nearly twice as fast as the conventional method when the cumulative cell detection probability is 0.95.

Phase rotation-based synchronisation channel structure for synchronous OFDM cellular system

For simple and robust cell search in a synchronous OFDM cellular system, considered is the coherent cell search algorithm where a cell-specific secondary synchronisation channel is coherently detected by using the channel response estimated from the primary synchronisation channel (P-SCH). Owing the limited number of P-SCH sequences, the channel response estimated from P-SCH does not match the channel response of the target cell, which will degrade the coherent cell search performance. To solve such a problem, proposed is a new phase rotation based synchronisation channel structure. It is shown by neighbour cell search simulations that the proposed technique significantly improves the coherent cell search performance.

Synchronization and Cell-Search Technique Using Preamble for OFDM Cellular Systems

In this paper, a novel preamble structure, including a synchronization field (S-field) and a cell-search field (C-field), is proposed for orthogonal-frequency-division-multiplexing-based cellular systems. An efficient algorithm for downlink synchronization and cell search using the preamble is also proposed. The synchronization and cell-search process includes the initial symbol-timing estimation using continuously or, at least, periodically transmitted downlink signal, the frame detection, the fine symbol-timing estimation, the frequency-offset estimation using the preamble S-field, and the cell identification using the preamble C-field. Performance of each synchronization and cell-search step is analyzed and verified by computer simulation. The overall performance of the synchronization and cell search is then analyzed in terms of the mean acquisition time. It is shown that the proposed preamble with the corresponding synchronization and cell-search algorithm can provide a very robust synchronization and cell-search capability, even in bad cellular environments.

Performance Analysis of 3-Stage Cell Search Process in a WCDMA System

In this article, we study the performance benefits of the cell search algorithm. The purpose of the cell search algorithm in Universal Mobile Telecommunication Systems (UMTS) is to estimate the spreading code of the serving base-station and its corresponding timing offset. We study the performance benefits of estimating multiple “code-time” hypotheses in each stage of the cell search process. In addition, we also study the effect of oversampling and nonideal sampling. The improved cell search design (CSD) proposed in this article aims to achieve faster synchronization between the mobile station (MS) and the base station (BS) and thus improves system performance, also has lower hardware utilization when compared with the third generation partnership project (3GPP)-comma free cell search design scheme under the same design constraints.

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, causing 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.

Fast Cell Search Algorithm for Overlay System with Cellular and Isolated Cells in Forward Link for OFCDM Broadband Wireless Access

This paper proposes a new cell-specific scrambling code (CSSC) assignment method and a fast cell search algorithm in the forward link for Orthogonal Frequency and Code Division Multiplexing (OFCDM) wireless access that are suitable for a system incorporating coexisting isolated and cellular cells. In the proposed method, one or some CSSC groups and thereby the CSSCs belonging to the CSSC groups are exclusively assigned to isolated cells. By detecting the best CSSC assigned to an isolated cell with higher priority than the cellular cells, the best cell including the isolated cell obtaining the minimum path loss can be detected far faster than by using the conventional cell search method, which employs uniform CSSC assignment. Computer simulation results show that by using the proposed cell search method together with the exclusive CSSC assignment to the isolated cells, the isolated-cell detection probability of approximately 90% is achieved at the cell boundary after the cell search time of 10msec, while corresponding detection probability using conventional CSSC assignment is approximately 80% without notifying the user equipment of the cell type and its CSSC information of the surrounding cells via the broadcast channel, at the average received signal energy per bit-to-noise power spectrum density ratio (E b /N 0 ) of 10dB for the common pilot channel (CPICH) in the cellular cells, when the transmission power ratio of the CPICH to the packet data channel (PDCH) for a one-code channel is R CPICH = 9dB in a 20-cell layout model.

Chimera Donor Cell Search Algorithm Suitable for Solving the Full Potential Equation

An approximate iterative search algorithm for finding donor cells associated with the chimera zonal grid approach is presented. This new algorithm is both fast and simple. It is used in conjunction with a chimera-based full potential solver for computing transonic flow solutions about wing and wing/fuselage configurations. Within each grid zone a fully implicit approximate factorization scheme is used to advance the solution one iteration. This is followed by the explicit advance of all common intergrid boundaries using a trilinear interpolation of the velocity potential. The presentation is highlighted with numerical result comparisons, a grid refinement study, and parametric variation of pertinent algorithm parameters. The new search algorithm produces donor cells for the two-zone wing problem at a rate in excess of 60,000 cells/s (single processor Cray C90). The approximate nature of the search algorithm, which causes some of the donor cells to be approximated by nearest neighbor cells, does not cause any impact on solution accuracy. Overall the results indicate that the present chimera zonal grid approach is a viable technique for solving the full potential equation for aerodynamic applications

Experiments on fast cell search algorithm for intercellasynchronous W-CDMA mobile radio

Laboratory and field experiment results for a two-step cell search algorithm using scramble code masking for intercell asynchronous W-CDMA mobile radio are presented. The scramble code is masked at different time positions during each scramble period in the forward link common control channel (CCH) for scramble code timing detection at the mobile receiver. 16 scramble codes are used. The cell search time achievable with the authors' recently proposed three-step cell search algorithm is estimated from the experimental results; cell search can be accomplished within /spl sim/960 ms at a probability of 93% in the case of 512 scramble codes and 16 scramble code groups.

Comparison of the UKMO and GFDL GCM climate projections in NPP simulations for southern loblolly pine stands

CR Climate Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials CR 07:55-69 (1996) - DOI: https://doi.org/10.3354/cr007055 Comparison of the UKMO and GFDL GCM climate projections in NPP simulations for southern loblolly pine stands Sampson DA, Cooter EJ, Dougherty PM, Allen HL We used the process model BIOMASS version 13.0 to simulate contemporary net primary production (NPP) and NPP response to climate projections for a doubling of atmospheric CO2 concentration from 2 general circulation models (GCMs) that vary in their CO2 sensitivity: the less sensitive GFDL and the more sensitive UKMO. Increased GCM sensitivity to CO2 is reflected in increased predictions in the magnitude, variation, and range of the climate variables. Simulations used a 40 yr historical climate record, and 2 stand and site conditions to standardize the total NPP response estimates for eighteen 1×1° grid cells across the southern United States. Contemporary NPP and NPP response estimates from the 18 cells were smoothed using a cell search algorithm to obtain an NPP response index matrix for the entire loblolly pine (Pinus taeda) forest-type. We conducted a sensitivity analysis of the environmental variables projected to change in a 2×CO2 environment to help interpret simulation output. Contemporary NPP varied from 2.5 to 8.5 Mg C ha-1 yr-1 over the range of loblolly pine. High leaf area index (LAI) simulations had 1.5 to 2 times the productivity of low LAI simulations, but the regional patterns were similar; NPP was correlated with regional differences in precipitation and temperature. The NPP response to future climate and atmospheric changes depended on the GCM used, and on the stand and site condition assumed. Inter-annual estimates for the 18 cell simulations resulted in a +22 to +84% NPP response for the GFDL climate projections and a -30 to +94% NPP response for the UKMO climate projections. The 40-year average NPP response for the smoothed data ranged from +43 to +65% and -1 to +94% for the GFDL and the UKMO climate projections, respectively. Consequently, the magnitude and range of the 40-year average NPP response to the climate projections was directly correlated with the GCM CO2 sensitivity. Although increased CO2 sensitivity resulted in broader extremes in the predicted temperature response, precipitation response for the 2 models was similar. The NPP response was also correlated with the patterns in predicted climate change, with regional differences coupled to local climatic conditions. Climate projections from both models produced similar NPP responses when predicted temperatures and precipitation regimes were similar. Elevated ambient CO2 had a greater effect on NPP response than temperature or precipitation in the sensitivity comparisons. Simulations indicate that a CO2 fertilizer effect, assuming no CO2 acclimation, more than compensates for declines in productivity over most of the loblolly pine forest-type associated with projected decreased precipitation and/or projected low to moderate increases in temperature and, therefore, increased maintenance respiration costs. Loblolly pine · GCM · UKMO · GFDL · Climate change Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in CR Vol. 07, No. 1. Publication date: August 22, 1996 Print ISSN: 0936-577X; Online ISSN: 1616-1572 Copyright © 1996 Inter-Research.

The automated analytical electrophoresis microscope

The components of an automated computer-controlled analytical electrophoresis microscope (AEMS) are described. Computer tracking of migrating cells projected under phase contrast onto a vidicon permits the rapid taking of multiple velocity measurements per cell so that reliable determinations of electrophoretic mobilities thereby result. The computer-controlled cell search and tracking algorithms allow high speed operation so that statistically valid profiles and data bases can be collected rapidly. Initial electrophoretic mobility evaluations have been carried out on populations of lymphocytes, erythrocytes, and platelets.