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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]

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]

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]

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]

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]

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]

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]

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]