Preamble Sequence Research Articles

Research on the DFT of ZC Sequence in TD-LTE System

In the LTE system, Zadoff---Chu (ZC) sequence is used for the generation and detection of physical random access channel (PRACH) preamble sequence. The key step of PRACH baseband signal generation ...

Wireless Synchronization Preamble Detection Scheme Using Bispectra-Based Statistics in the Presence of Stationary Noise

Higher-order statistical analysis has been applied in many areas of communication systems, such as blind equalization, pattern recognition and channel estimation; among others. In this paper, wireless preamble sequences in additive noise are processed to reduce the signal to noise ratio of synchronization signals thereby improving interconnectivity. For such end, detection structures using matched filtering in the form of passive implementation along with cumulant-based processing are proposed. A framework based on bispectra is used to obtain the probability of detection confirming successful synchronization in the presence of Gaussian and non-Gaussian noise. Signal bispectra and power of the tests are estimated over a number of samples within the length of standard wireless preamble signals.

Design of Wireless Automatic Synchronization for the Low-Frequency Coded Ground Penetrating Radar

Low-frequency coded ground penetrating radar (GPR) with a pair of wire dipole antennas has some advantages for deep detection. Due to the large distance between the two antennas, the synchronization design is a major challenge of implementing the GPR system. This paper proposes a simple and stable wireless automatic synchronization method based on our developed GPR system, which does not need any synchronization chips or modules and reduces the cost of the hardware system. The transmitter omits the synchronization preamble and pseudorandom binary sequence (PRBS) at an appropriate time interval, while receiver automatically estimates the synchronization time and receives the returned signal from the underground targets. All the processes are performed in a single FPGA. The performance of the proposed synchronization method is validated with experiment.

Study of High-Accurate Frequency Estimation in 60GHz Wireless Communication System

A high-accurate frequency estimation algorithm is proposed in the 60GHz OFDM wireless communication system. The phase offset is caused by the carrier frequency offset, and its accumulation has a linear relationship in the time. So the preamble sequence phase can be obtained by the algorithm in this paper, and then the carrier frequency offset value is calculated by the linear regression theory. The 60GHz wireless communication system simulation platform is established. In the platform, the algorithm is simulated with different carrier frequency offset, and the algorithm estimation performance is contrasted with the traditional algorithm. The results show that accuracy of the algorithm has 30dB higher than the auto- correlation algorithm, and that the BER performance of the algorithm is the same as witch in the case of no frequency offset. So the high-accuracy of frequency offset estimation is proposed by the algorithm in the 60GHz wireless communication.

밀리미터 웨이브 링크를 갖는 셀룰러 통신 시스템을 위한 송·수신 빔 추적 기법

In cellular communication systems employing millimeter wave (mmWave) bands for a link, a large amount of training time and network resources will be required to find a serving BS with the best transmit and receive (Tx-Rx) beam pair if downlink control signals are used. In this paper, a tracking technique for OFDM-based cellular communication systems with a mmWave link, where an analog beamforer is used at the mobile station (MS) and a digital beamformer is used at the BS, is proposed using an uplink signal. A technique to select a serving BS with the best beam pair is described using the uplink preamble sequence based on Zadoff-Chu sequence and a metrics which can be used to identify parameters such as beam ID (BID), MS ID (MID), and direction-of-arrival (DoA). The effectiveness of the proposed technique is verified via simulation with the spatial channel model (SCM) for a moving MS in mmWave cellular systems. ※ 본 연구는 지식경제부 및 정보통신산업진흥원의 대학 IT연구센터 지원사업 (NIPA-2014-H0301-14-1015) 과 2012년도 정부(교육과 학기술부)의 재원으로 한국연구재단의 기초연구사업 지원을 받아 수행된 것임(2012005603) First Author : School of Electric & Electronic Engineering, Chung-Ang University, KOREA, 학생회원 ° Corresponding Author : School of Electric & Electronic Engineering, Chung-Ang University, KOREA, 종신회원 * School of Electric & Electronic Engineering, Chung-Ang University, KOREA, 학생회원 논문번호:KICS2014-08-292, Received August 5, 2014; Revised October 31, 2014; Accepted October 31, 2014 The Journal of Korean Institute of Communications and Information Sciences '14-12 Vol.39C No.12

On design of physical random access channel in high-speed railway LTE systems

For the uplink in the long-term evolution (LTE) systems, the physical random access channel (PRACH) adopts Zadoff–Chu (ZC) sequences as preamble sequences, and each user can choose a unique cyclic shift for user identification. In high-mobility scenario, the Doppler frequency shift raises up the false alarm probability by inducing the correlation peak offsetting at the receiver side. Traditional detection method utilizes multiple search windows for searching the potential uplink users. When the Doppler frequency shift is larger than the subcarrier spacing, the energy of correlation peak leaks outside the search window and increases the false alarm probability. In this paper, we present a novel design for PRACH preamble sequence for high-speed railway scenario. Through numerical observation, we find out that the offset of the correlation peaks only depends on the initial root sequence number and the length of ZC sequences. Therefore, the root number of ZC sequences should be carefully designed to generate a preamble sequence to fight against the Doppler frequency shift. Consequently, those offsets of the correlation peaks are concentrated within a single search window, resulting in lower complexity of detection and lower probability of false alarm for random access in LTE uplink.

Design and Realization of a Full Digitalization GMSK Modem on FPGA

To implement GMSK modem with the characteristics of good spectrum, low complexity and fast acquisition, a full digitizationGMSKmodem scheme was proposed. Based on LUT method, the generation of GMSK signals has better spectrum characteristicand easy to realize. In receive terminal, a non-coherent digitized GMSKreceiver with fast signal detection and symbol timing acquisitionalgorithm was presented. Double sliding windows was used to conquer the influence of communication channel gain on the detection algorithm and realized within 6 symbols with accuracy. Additionally, in order to reduce the complexity of the receiver, the received signals are demodulated sample by sample in advance and then decided with the estimated symbol timing. The symbol timing acquisition algorithm proposed is realized based on a preamble sequence rapidly within only 8 symbols. Simulation results and integrated FPGA realizationprove its feasibility and superiority.

Timing Synchronization Performance of Short Preamble Sequence with Orthogonal Frequency Multiplexed Data Symbols

Timing Synchronization Performance of Short Preamble Sequence with Orthogonal Frequency Multiplexed Data Symbols

Fast Antijamming Timing Acquisition Using Multilayer Synchronization Sequence

Pseudonoise (PN) sequences are widely used as preamble sequences to establish timing synchronization in military wireless communication systems. At the receiver, searching and detection techniques, such as the full parallel search (FPS) and the serial search (SS), are usually adopted to acquire correct timing position. However, the synchronization sequence has to be very long to combat jamming that reduces the signal-to-noise ratio (SNR) to an extremely low level. In this adverse scenario, the FPS scheme becomes too complex to implement, whereas the SS method suffers from the drawback of long mean acquisition time (MAT). In this paper, a fast timing acquisition method is proposed, using the multilayer synchronization sequence based on cyclical codes. Specifically, the transmitted preamble is the Kronecker product of Bose-Chaudhuri-Hocquenghem (BCH) codewords and PN sequences. At the receiver, the cyclical nature of BCH codes is exploited to test only a part of the entire sequence, resulting in shorter acquisition time. The algorithm is evaluated using the metrics of MAT and detection probability (DP). Theoretical expressions of MAT and DP are derived from the constant false-alarm rate (CFAR) criterion. Theoretical analysis and simulation results show that our proposed scheme dramatically reduces the acquisition time while achieving similar DP performance and maintaining a reasonably low real-time hardware implementation complexity, in comparison with the SS scheme.

Doubly spread preamble sequence for timing acquisition in ultra‐wideband communications

SUMMARYWe propose a new preamble that can reduce the performance degradation because of the diminishing of operational complexity in coarse timing acquisition. The reduced‐complexity acquisition algorithm uses a received preamble that has been shortened by summing its elements group‐by‐group. Therefore, the performance deteriorates because it loses the impulsive autocorrelation property of the preamble after summation and correlation. In this paper, we design a preamble sequence with a sliding correlator output function that shows a distinct peak at zero delay and symmetry even after summation based on a flipping and doubly spreading concept. By comparing with other preamble sequences, we prove that the proposed preamble shows better timing acquisition performance in ultra‐wideband channel environment.Copyright © 2013 John Wiley & Sons, Ltd.

The Research on the FDD-LTE System and its Key Technologies

The paper elaborates OFDM technology and its advantages and disadvantages, analyzes the basic principles on random access preamble sequence design ,and defines and analyzes Zadoff sequences and its excellent characteristics . After that, the paper analyzes the frequency offset exists and ZC sequence cyclic shift for the reasons for the decline of the autocorrelation peak of Zero, as a relative frequency offset .Finally,the paper proposes and emphasizes on the design of random access preamble sequence.

An Economical, ISI-Immune Frequency Offset Estimator for DOCSIS Upstream Channels

This paper discusses the design and implementation of frequency offset estimation algorithms for DOCSIS upstream channels. A cost-effective estimator which approaches the Cramer-Rao bound for high SNRs is derived. The effect of ISI generated by upstream micro-reflections in typical cable networks is considered, and a condition upon the transmitted preamble sequence which guarantees unbiased estimation is presented. It is shown that the proposed estimator is unbiased for a wide range of preamble sequences, which is generally not the case for burst frequency estimators. This flexibility may be utilized by selecting a broadband preamble which is suitable for performing channel estimation and frequency offset estimation simultaneously, thereby increasing the efficiency of the upstream channels.

A polarity comparison timing synchronization estimation for MB-OFDM-based UWB systems

Abstract We propose a new approach for timing synchronization estimation with polarity comparison for multi-band orthogonal frequency division multiplexing (MB-OFDM)-based UWB systems. We attempt to locate the start sample of frame sequences by calculating difference of the two cross-correlation functions, between received symbols, the successive received symbols, and predefined preamble sequence. It makes sense to propose polarity comparison and identification ideas to the scenario, the cross-correlation difference exceeding predefined threshold is not unique. If polarities of selected symbols are not all the same, the estimator is put forward to find out a peak of correlation summation to figure out the unique timing point and promote synchronization accuracy. Uniqueness and accuracy of timing synchronization, therefore, could be guaranteed. The performance of the proposed estimator is evaluated by mean square error (MSE) and synchronization probability. The proposed estimator could carry out timing synchronization for MB-OFDM-based UWB systems and make the uniqueness of timing index for sure. The MSEs of the proposed estimator are evidently lower than the reference method for a great deal. Total and exact synchronization probability could get as much as 100 and 96%.

Self‐optimization of random access channel in 3rd Generation Partnership Project Long Term Evolution

ABSTRACTThe long term evolution (LTE) is being designed to enhance third generation radio access technologies, and it represents a major step towards high‐performance mobile data networks that are fully optimized for packet‐switched connections. In an initial access, the LTE user equipment executes the random access (RA) procedure while searching for serving base station and initiating services. For a good cell coverage to be obtained, feasible uplink data rate and low delays in, for example, call setup, the optimal random access channel (RACH) performance is essential. Although manual tuning of procedures can be very costly, it is important to design self‐organizing network (SON) algorithms that optimize procedures such as RA. In this paper, a mathematical framework for the RACH modeling in LTE technology is presented on the basis of probability theory and statistics. A self‐optimization algorithm for RACH preamble sequence allocation and preamble split is then examined using the deduced mathematical framework and system‐level simulations. Performance analysis is semi‐analytical: First, RACH performance results are produced using analytical model, and second, outputs are fed into a dynamic LTE network simulator. Results show that the proposed optimization approach clearly improves uplink performance and ensures a certain success rate at the first RA attempt so that shorter handover durations and call setup delays can be achieved. Copyright © 2011 John Wiley & Sons, Ltd.

A frequency domain coherent detection scheme to realize DAA technique for WiMedia UWB systems

In this paper, a low complexity detection scheme is proposed to detect so-called victim systems in the WiMedia UWB environment. According to regulation of DAA in world-wide radio frequency, many detection schemes have been studied and time-domain coherent detection (TDCD) scheme is known as the best approach with respect to the detection performance. However, this scheme requires the additional filter and down-sampler to reconstruct victim signal from the received signal and these requirements lead to increase of hardware complexity. The proposed frequency-domain coherent detection (FDCD) scheme is based on the cross-correlation with frequency-domain reference sequences (FDRS), which are derived from the preamble sequence of the victim system. The detection performance is almost the same as that of the TDCD scheme and the computational complexity is about half.

Subcarrier allocation for improvement of preamble sequence detection

A subcarrier allocation method is proposed for the improvement of the preamble sequence detection. Precise detection of the preamble sequence is crucial for identifying the base station. It is shown that the proposed method can substantially enhance the performance of the preamble sequence detection. Finally, the condition under which the proposed method can maintain the performance of the channel quality indicator measurement is investigated.

Low-Complexity Mean-Delay Estimation for OFDM Systems

In this paper, we propose two simple orthogonal frequency-division multiplexing (OFDM) mean-delay estimation schemes, i.e., a channel impulse response (CIR)-based scheme and a differential scheme, which are applicable for adaptive algorithms including improved channel estimation and fast handover. Instead of time-domain processing which requires additional inverse fast Fourier transform (IFFT), the mean delay can be obtained in the proposed CIR-based scheme using the estimated frequency-domain CIR. When cell-specific preamble sequences are employed, the mean delay can also be estimated without CIR estimation in the proposed differential scheme using cross correlation of differentially correlated received signals, enabling further complexity reduction and performance improvement when the CIR estimation is not sufficiently accurate. The performance of the proposed schemes is verified by computer simulation.

Error vector magnitude to SNR conversion for nondata-aided receivers

Error vector magnitude (EVM) is one of the widely accepted figure of merits used to evaluate the quality of communication systems. In the literature, EVM has been related to signal-to-noise ratio (SNR) for data-aided receivers, where preamble sequences or pilots are used to measure the EVM, or under the assumption of high SNR values. In this paper, this relation is examined for nondata-aided receivers and is shown to perform poorly, especially for low SNR values or high modulation orders. The EVM for nondata-aided receivers is then evaluated and its value is related to the SNR for quadrature amplitude modulation (QAM) and pulse amplitude modulation (PAM) signals over additive white Gaussian noise (AWGN) channels and Rayleigh fading channels, and for systems with IQ imbalances. The results show that derived equations can be used to reliably estimate SNR values using EVM measurements that are made based on detected data symbols. Thus, presented work can be quite useful for measurement devices such as vector signal analyzers (VSA), where EVM measurements are readily available.

Differential preamble detection in packet-based wireless networks

A novel hypothesis-based preamble detection method for uncoordinated, high-density packet-based communication over an additive white Gaussian noise channel is proposed and analyzed. Received samples are observed over a window of length equal to that of the preamble and a metric is computed for each sample shift of the window. A metric exceeding a noise dependent pre-computed threshold flags the presence of a preamble. The preamble sequence consists of concatenated sections of spreading sequences whose length is at most the coherence time of the channel. These sections are then differentially combined. A differential correlation-based detection is employed to locate the boundaries of the preamble. A theoretical framework is developed to provide exact analytical solutions for missing and falsely detecting a preamble using matrix analysis of quadratic Gaussian statistics. Furthermore, the robustness of the proposed methodology in a two path channel is studied. The effects of frequency and timing offsets on the system performance is evaluated. Simulation results are presented to validate the analytical expressions. Additionally, a performance comparison of the proposed differential detection scheme with that of a noncoherent square-law detector is presented.

Investigations on Physical Random Access Channel Structure in Evolved UTRA Uplink

This paper presents the optimum physical random access channel (PRACH) structure in terms of the number of control signaling bits accommodated and the transmission bandwidth based on the link budget in order to satisfy the coverage requirement for the single-carrier (SC)-FDMA based E-UTRA uplink. First, we present the design concept of the PRACH structure considering the purposes of the random access procedure in the E-UTRA. Simulation evaluations including a system-level simulation show that a PRACH comprising a 0.5-msec preamble sequence can convey a 6-bit control signal at the cell edge when the inter-site distance (ISD) is 500m under full channel load conditions with one-cell frequency reuse. It is also shown, however, that a PRACH longer than one-sub-frame, e.g., 1.0msec, is necessary to support the ISD of 1732m assuming the same conditions. We also show that the best transmission bandwidth for the PRACH is approximately 1.08-4.5MHz from the viewpoint of the misdetection probability, and a 1.08-MHz transmission bandwidth is suitable considering other aspects such as flexible resource assignment in the time domain and a small number of options in the transmission bandwidth.