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The integration of radar interference is an effective technical path to optimize radio frequency resources and realize directional interference. Radar interference integrated waveform design is a hot spot in radar interference integrated research. This paper presents an radar interference integrated waveform based on Zadoff-Chu sequence and orthogonal frequency division multiplexing (OFDM) architecture, and studies the waveform design and processing methods. The waveform uses OFDM as the modulation mode and time- frequency division multiplexing as the basic architecture. The frequency domain subcarriers are reasonably allocated and modulated through Zadoff-Chu and Mersenne-Twister sequences to achieve the integration of detection and interference functions. In signal processing, the first step in to separate the time and frequency of interference detection, and the second step in to conduct pulse compression and coherent processing, so as to achieve ranging and velocity measurement. Theoretical analysis and simulation test show that the proposed waveform has the advantages of high ratio of main lobe to side lobe of pulse compression, strong Doppler tolerance, flexible frequency alignment and strong interference randomness. [ABSTRACT FROM AUTHOR]

In this paper, we propose a novel technique for the inspection of high-density polyethylene (HDPE) pipes using ultrasonic sensors, signal processing, and deep neural networks (DNNs). Specifically, we propose a technique that detects whether there is a diversion on a pipe or not. The proposed model transmits ultrasound signals through a pipe using a custom-designed array of piezoelectric transmitters and receivers. We propose to use the Zadoff–Chu sequence to modulate the input signals, then utilize its correlation properties to estimate the pipe channel response. The processed signal is then fed to a DNN that extracts the features and decides whether there is a diversion or not. The proposed technique demonstrates an average classification accuracy of 90.3 % (when one sensor is used) and 99.6 % (when two sensors are used) on 3 4 inch pipes. The technique can be readily generalized for pipes of different diameters and materials. [ABSTRACT FROM AUTHOR]

In this paper, we propose a novel technique for the inspection of high-density polyethylene (HDPE) pipes using ultrasonic sensors, signal processing, and deep neural networks (DNNs). Specifically, we propose a technique that detects whether there is a diversion on a pipe or not. The proposed model transmits ultrasound signals through a pipe using a custom-designed array of piezoelectric transmitters and receivers. We propose to use the Zadoff–Chu sequence to modulate the input signals, then utilize its correlation properties to estimate the pipe channel response. The processed signal is then fed to a DNN that extracts the features and decides whether there is a diversion or not. The proposed technique demonstrates an average classification accuracy of 90.3% (when one sensor is used) and 99.6% (when two sensors are used) on 34 inch pipes. The technique can be readily generalized for pipes of different diameters and materials.

The integration of satellite and the terrestrial cellular network is a promising technology to provide global ubiquitous communication. As orthogonal frequency-division multiplexing (OFDM) has been adopted in the 3GPP standards, such as 4G LTE and the ongoing 5G new radio (NR), it will become an important feature of the satellite to achieve a high degree of commonality with the terrestrial cellular networks, i.e. LTE or 5G. For OFDM systems, synchronization is crucial for the initial attach processing. Unlike the traditional OFDM-based terrestrial cellular systems, synchronization in OFDM-based satellite is facing new challenges, due to the higher Doppler shift in the satellite system. In this paper, we analyze the impact of large doppler on the synchronization of the OFDM-based satellite system and then propose new methods to estimate the carrier frequency offset for the OFDM-based satellite. The advantages of the proposed methods are as follows: first, the proposed methods are compatible with the procedures of the LTE and NR; second, our methods are designed based on the features of the satellite channel, it is suitable for the OFDM-based satellite system; third, the complexity of our methods, whose primary computational efforts are relatively cheap matrix-vector multiplications, is lower than the previous methods. [ABSTRACT FROM AUTHOR]

In this paper, we consider the implementation of different Zadoff-Chu sequences to different modulation levels in communication systems with multiple modulation levels. The base station of the system can dynamically estimate the number of users in each modulation level by detecting the Zadoff-Chu sequences it receives. The base station then calculates the throughput of each modulation level and determines if any modulation level is saturated. If a modulation level is saturated, then the base station implements an additional mechanism on the users in the modulation level with the largest throughput. This mechanism makes users enter a waiting period before allowing further data transmissions so as to mitigate or reduce the base station load to accomplish the tasks and functions of the self-organizing network. [ABSTRACT FROM AUTHOR]

An improved timing and frequency synchronization algorithm based on Zadoff-Chu(ZC) sequence for OFDM system is proposed. The algorithm constructs a training sequence with conjugate repetition relationship. Firstly, the timing synchronization is completed by utilizing the conjugate characteristics of the training sequence in time domain, and the integer frequency offset(IFO) estimation is obtained directly, not affected by the frequency synchronization performance. Then the fractional frequency offset(FFO) estimation is done using the repeatability of the training sequence after timing synchronization. Theoretical analysis and simulation results show that the improved algorithm′s timing and frequency offset estimation mean square error is lower, the integer and fractional frequency offset estimation range is expanded, and computational complexity is reduced.

Simultaneous acquisition of channel state information (CSI) of many devices with high accuracy is crucial to provide the Internet-of-Things (IoT) connectivity in cellular networks. A traditional channel estimator in cellular networks adopts the orthogonal pilot structure, which cannot provide high scalability for many IoT devices without a significant increase of pilot overhead. To overcome such a limitation, we propose a novel channel estimator based on non-orthogonal pilot signals for frequency-division duplex (FDD) based uplink cellular IoT networks. The proposed scheme provides an interference-canceled environment during the channel estimation procedure by reconstructing the non-orthogonal pilot signals and removing their effects. Consequently, the proposed scheme can increase the number of available pilot signals without any increase of pilot overhead, which makes the BS spectral-efficiently accommodate more IoT devices with full exploitation of antenna technique. The numerical results verify the effectiveness of the proposed scheme on supporting more IoT devices at the expense of a slight loss of the channel estimation accuracy, compared to the conventional discrete Fourier transform (DFT)-based channel estimator, from the viewpoint of a mean squared error, a bit error rate and a network throughput.

The physical random access channel (PRACH) in the uplink of cellular systems is used for the initial access requests from users. In fifth generation (5G) systems three different types of services are available, which are massive machine-type communication, enhanced mobile broadband communication, and ultra-reliable low-latency communication. Considering the tight requirements in terms of latency, a robust design of PRACH receiver is one of the priorities. In this paper we first explore the simple extension of a technique proposed for fourth generation (4G) systems to 5G. Then we propose the application of machine learning techniques to make the PRACH receiver more robust to false peaks, which are responsible of performance degradation in the extension of the 4G technique to 5G. Monte Carlo simulations are used to evaluate and compare the performance of the proposed algorithms. [ABSTRACT FROM AUTHOR]

Inter-cell interference is a major issue for next-generation wireless cellular networks, due to the increased user mobility, high user density, and backhaul bandwidth constraint. In this work, a unified approach is proposed to address these challenges. The proposal firstly performs a per-cell signal spreading by Zadoff-Chu (ZC) sequence, then the spread signal is precoded by a modified coordinated beamforming scheme. The proposal is robust to Doppler caused by user mobility, supports a high co-channel user capacity for ultra-dense networks, and requires only limited backhaul signaling exchange between basestations thus being suitable for massive MIMO deployment. The advantages of the proposal are firstly analyzed in theory, then evaluation results are presented to validate the proposal for MIMO and massive MIMO setups. It is found that the proposed scheme consistently outperforms the traditional scheme under various scenarios. The practical issues related to synchronization in coordinated beamforming are discussed. [ABSTRACT FROM AUTHOR]

In this paper, we analyze the acquisition and tracking performance of signal using a tiered differential polyphase code as the secondary code. The Zadoff-Chu sequence is known to have a CAZAC (Constant Amplitude Zero Auto-Correlation) characteristics. The secondary code generated by differential encoding of the Zadoff-Chu sequence also has the same characteristics as the Zadoff-Chu sequence. Therefore, long integration will give better correlation results. We compare signal acquisition and tracking performance when using the NH sequence and Zadoff-Chu sequence as the secondary code. Monte-carlo simulation is performed using MATLAB. We use the probability of detection and the mean acquisition time for signal acquisition performance and tracking jitter for signal tracking performance. [ABSTRACT FROM AUTHOR]

The physical random access channel (PRACH) in the uplink of cellular systems is used for the initial access requests from users. In fifth generation (5G) systems three different types of services are available, which are massive machine-type communication, enhanced mobile broadband communication, and ultra-reliable low-latency communication. Considering the tight requirements in terms of latency, a robust design of PRACH receiver is one of the priorities. In this paper we first explore the simple extension of a technique proposed for fourth generation (4G) systems to 5G. Then we propose the application of machine learning techniques to make the PRACH receiver more robust to false peaks, which are responsible of performance degradation in the extension of the 4G technique to 5G. Monte Carlo simulations are used to evaluate and compare the performance of the proposed algorithms. [ABSTRACT FROM AUTHOR]

Cellular networks will play an important role in realizing the newly emerging Internet-of-Everything (IoE). One of the challenging issues is to support the quality of service (QoS) during the access phase, while accommodating a massive number of machine nodes. In this paper, we show a new paradigm of multiple access priorities in random access (RA) procedure and propose a novel root-index based prioritized random access (RIPRA) scheme that implicitly embeds the access priority in the root index of the RA preambles. The performance evaluation shows that the proposed RIPRA scheme can successfully support differentiated performance for different access priority levels, even though there exist a massive number of machine nodes.

In this article, timing synchronization in OFDM is attained with the help of Zadoff-Chu sequence as a training symbol. An algorithm based on the cross-correlation property of fractional Fourier transform (FRFT) is proposed to generate a new timing metric. In this algorithm, cross correlation of received signal and Z-Chu sequence is taken at the receiver side in FRFT domain. The mathematical analysis of proposed estimator has been done and the variance of timing metric is obtained under the effect of AWGN channel. The simulation result shows that the variance of timing metric decreases as signal to noise ratio increases. The mean and MSE of the timing offset is simulated under HYPERLAN indoor channel (type-A). The proposed estimation method has been compared with existing methods and established as a better method to combat timing offset. [ABSTRACT FROM AUTHOR]

We propose an enhanced physical random access channel (PRACH) preamble detector, which efficiently identifies non-orthogonal preambles while suppressing the noise rise. The proposed PRACH preamble detector reconstructs preambles from the received signal and efficiently utilizes them to improve the detection performance. Through simulations, we verify that the proposed detector successfully detects the desired preambles while suppressing the undesired noise rise, and, thus, it can detect ten non-orthogonal preambles simultaneously with an extremely low mis-detection probability lower than 10^-5 , while achieving a false alarm probability of approximately 10^-3 . [ABSTRACT FROM PUBLISHER]

A Zadoff–Chu (ZC) sequence is uncorrelated with a non-zero cyclically shifted version of itself. However, this alone is insufficient to mitigate inter-code interference in LTE initial uplink synchronization. The performance of the state-of-the-art algorithms vary widely depending on the specific ZC sequences employed. We develop a systematic procedure to choose the ZC sequences that yield the optimum performance. It turns out that the procedure for ZC code selection in LTE standard is suboptimal when the carrier frequency offset is not small. [ABSTRACT FROM PUBLISHER]

To overcome the preamble collision in multi-RRU combined with same cell and other co-channel network scenario of rail transport, from the key role of random access, we redistribute and design preamble based on the Zadoff-Chu sequence structure. The aim is to promote reuse degree and complete tool development. The design method is related to the actual operation speed and the business needs in railway. Scene division depends on the performance of different frequency bands. In the low speed / high speed scene we determine the root sequence by rational cyclic shift to adapt different cell radius and different running speed. In the super high speed scene we use an adaptive interpolation method to design long sequence. Operational results show that the study can achieve sequence distribution in main interference area of the low speed / high speed scene, the sequence has good self-correlation ami cross correlation of the super high speed scene. So the preamble is fully isolated , and the uncertain factors in random access are effectively controlled. [ABSTRACT FROM AUTHOR]

In view of the distinctive characteristics of satellite communication, the physical random access signals used in the terrestrial mobile communication system have to be modified or redesigned for the satellite communication system. In this paper, we boost the random access signal energy by repeating the short Zadoff–Chu (ZC) sequence based preamble signal used in the terrestrial system. Different long ZC sequences are used to scramble this cascaded sequence to distinguish different random access signals for multiple random access user equipments. For correlation performance optimization, properties of the roots for both the short and long ZC sequences are mathematically analyzed and derived. Finally, we illustrate how to construct a root set for these different long ZC sequences based on the obtained propositions in a practical way. This analytical framework provides a useful insight into ZC sequence-based random access signal design and performance analysis in mobile satellite communication systems. [ABSTRACT FROM AUTHOR]

The processing time for beam training in millimeter-wave (mmWave) cellular systems can be significantly reduced by a code division multiplexing (CDM)-based technique, where multiple beams are transmitted simultaneously with their corresponding Tx beam IDs (BIDs) in the preamble. However, mmWave cellular systems with CDM-based preambles require a large number of cell IDs (CIDs) and BIDs, and a high computational complexity for CID and BID (CBID) searches. In this paper, a new preamble design technique that can increase the number of CBIDs significantly is proposed, using a preamble sequence constructed by a combination of two Zadoff-Chu (ZC) sequences. An efficient technique for the CBID detection is also described for the proposed preamble. It is shown by simulations using a simple model of an mmWave cellular system that the proposed technique can obtain a significant reduction in the complexity of the CBID detection without a noticeable performance degradation, compared to the previous technique. [ABSTRACT FROM AUTHOR]

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 is to perform a discrete Fourier transform (DFT) of ZC sequence, which is characterized by the root index u and a rotation factor p. On-line computation according to the DFT formula is adopted in traditional algorithm, which has high computational complexity and is hard to meet the real-time requirement of LTE system. In this paper, it is mainly to improve the calculation of rotation factor p in DFT formula. Based on theoretical analysis of the ZC sequence DFT property, the symmetry property and recurrence relations of its rotation factor p are derived. Hence, a small amount of the rotation factors p in a ZC sequence can be calculated off-line and stored in memory firstly. And then all the other rotation factors can be obtained by looking up the table and some simple computations. As a result, the improved ZC sequence DFT can be achieved with less computational effort at a little expense of memory space. [ABSTRACT FROM AUTHOR]

In this paper, a beam ID preamble (BIDP) technique, where a beam ID is transmitted in the physical layer, is proposed for efficient beam training in millimeter-wave cellular communication systems. To facilitate beam ID detection in a multicell environment with multiple beams, a BIDP is designed such that a beam ID is mapped onto a Zadoff-Chu sequence in association with its cell ID. By analyzing the correlation property of the BIDP, it is shown that multiple beams can be transmitted simultaneously with the proposed technique with minimal interbeam interference in a multicell environment, where beams have different time delays due to propagation delay or multipath channel delay. Through simulation with a spatial channel model, it is shown that the best beam pairs can be found with a significantly reduced processing time of beam training in the proposed technique. [ABSTRACT FROM AUTHOR]

Common signals in public channels of cellular systems should be transmitted omnidirectionally from the base station (BS) to ensure cell-wide coverage. In this paper, we propose an omnidirectional precoding (OP) based transmission for public channels in massive MIMO systems, which leads to a significant reduction in the downlink pilot overhead while providing omnidirectional signaling. For this OP based transmission, we present three necessary conditions that the OP matrix should satisfy, to meet the requirements for omnidirectional transmission for reliable cell-wide coverage, equal average power on each antenna to sufficiently utilize all the available power amplifier capacities of BS antennas, and achievable ergodic rate maximization for the i.i.d. channel, respectively. Then, several examples of the OP matrix satisfying the three necessary conditions simultaneously are designed by utilizing the Zadoff-Chu sequence and its properties. We also analyze the system performance in terms of achievable ergodic rate, outage probability, and peak-to-average power ratio (PAPR) for these designs. It is shown that a dedicated design of the OP matrix has the following advantages: 1) it asymptotically maximizes the achievable ergodic rate, maximizes the achievable diversity order, and minimizes the outage probability in the large-scale array regime, not only for the i.i.d. channel, but also for spatially correlated channels; 2) it preserves the PAPR of the transmitted signal after precoding. [ABSTRACT FROM AUTHOR]

Time-reversed orthogonal frequency division multiplexing (TR-OFDM) has recently received attention as a promising spectral efficient scheme for single-input multiple-output communications over time-dispersive fading channels. For TR-OFDM, passive time reversal processing is used as a simple means for channel time dispersion reduction. In particular, pseudorandom noise (PN)-sequence padding time-domain synchronisation OFDM (TDS-OFDM) transmission scheme has been reported as an appealing alternative to the traditional cyclic prefix (CP) OFDM technology as it can provide significant improvement in the spectrum efficiency. In this study, a new correlation based coder for inter-block and inter-symbol interference removing in time-reversed TDS-OFDM, which is denoted TR-TDS-OFDM briefly is proposed. Such a coder is, then, tested for multipath channels with significant tap delays. A Zadoff–Chu sequence with perfect autocorrelation property is adopted as a training sequence (TS) for a TDS-OFDM system. Simulation results show that, by using TR-TDS-OFDM with correlation-based coder, a TS with length shorter than channel order can be used without introducing notable inter-block interference. The other merits of the proposed design are also supported by both theoretical analysis and numerical simulations.

Orthogonal frequency division multiplexing (OFDM) technique has been widely adopted in wireless systems, but it is known for being sensitive to synchronization errors. In this paper, we present timing and frequency synchronization algorithms for OFDM downlink transmissions using Zadoff-Chu sequences. We show that the current timing synchronization method employing Zadoff-Chu sequences is sensitive to carrier frequency offsets. To reduce this sensitivity, we develop conditions for the selection of appropriate Zadoff-Chu sequences. We then design a training sequence and propose joint signal detection, timing, and carrier frequency offset estimation algorithms for OFDM downlink transmissions. We show that the proposed schemes simplify the overall synchronization architecture and improve the performance compared to the existing schemes in the literature. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM AUTHOR]

Zadoff-Chu (ZC) sequences have been used as random access sequences in modern wireless communication systems, replacing the conventional pseudo-random-noise (PN) sequences due to their superior autocorrelation properties. An analytical framework quantifying the ZC sequence's performance and its fundamental limitation as a random access sequencein the presence of frequency offset}between the transmitter and the receiver is introduced. We show that a ZC sequence's perfect autocorrelation properties can be severely impaired by the frequency offset thereby limiting the overall performance of the random access signals formed from these sequences. First, we derive the autocorrelation function of these random access sequences as a function of the frequency offset. Next, we introduce the concept of critical frequency offsets and the spectrum associated with a ZC sequence set to characterize the frequency offset properties of the random access signals. Finally, we demonstrate that the frequency offset immunity of a ZC sequence set can be controlled by shaping the spectrum of the ZC sequence set. [ABSTRACT FROM AUTHOR]

Abstract: A novel data-aided error vector magnitude (EVM) estimator for signal-to-noise ratio (SNR) is derived. Previous SNR estimators are mainly based on the data symbols or the preamble symbols. However, most existing EVM estimators need the factually received symbols modulated and even coded again to recover the symbols in the receiver. To improve it, a good new estimator that utilizes Zadoff-Chu sequence as the preamble is recommended andadopted in this paper. Its performance is examined and compared with Maximum-Likelihood (ML) estimator by the measures of the normalized bias and the normalized mean square error. Numerical results are presented to show the visible advantages obtained by using this estimator. [Copyright &y& Elsevier]

In this paper, a complex matrix C consisting of a set of perfect sequences is studied. The matrix C is constructed by taking the inverse discrete Fourier transform (IDFT) of a diagonal matrix, in which the diagonal elements comprise an arbitrary periodically perfect sequence γ. Properties of the matrix C are presented. In addition, the Fourier dual E of the matrix C is investigated. When y is a Zadoff-Chu sequence for the case of N even, M = 1, and ɡ = 0, an explicit representation for the matrix E is derived. [ABSTRACT FROM AUTHOR]