Pseudo-noise Research Articles

A Novel Satellite PRN Code Assignment Method Based on Improved RLF Algorithm.

Low Earth Orbit (LEO) satellites have stronger received signals and more rapid geometry changes than Global Navigation Satellite System (GNSS) satellites, making them attractive for positioning, navigation, and timing (PNT) applications. Due to the low altitude, the LEO constellation requires more satellites to cover the entire globe and more Pseudo Random Noise (PRN) codes to realize Code Division Multiple Access (CDMA), which means greater receiver storage resources and receiver acquisition time. In this paper, different from the traditional methods that assign a unique PRN code to each satellite, we propose a novel method in which several satellites share the same PRN code, and simply demonstrate the feasibility and benefits of this method. To determine the minimum number of PRN codes needed for a constellation, we build a mathematical model. After the algorithm comparison, we improve the recursive largest first (RLF) algorithm so that it has a higher running speed and a smaller approximate optimal solution within a certain time period. By studying polar-orbiting and walker constellations, we find that if other satellite parameters remain the same, the higher the orbital altitude is, the more PRN codes are needed, and no matter what the orbital inclination is, the minimum number of PRN codes remains the same. Overall, it is feasible and meaningful for several satellites sharing the same PRN code to save storage resources and reduce the satellite acquisition time of the receiver. If this new technology is applied, the storage resources and the average satellite acquisition time of the receiver will be, at most, one-third of previous ones.

Waveform Reconstruction of DSSS Signal Based on VAE-GAN

The complex electromagnetic environment will limit the efficacy of communication equipment. It is critical to construct a complex electromagnetic environment to test communication equipment in order to maximize its capability. One of the most important methods for constructing a complex electromagnetic environment is signal reconstruction. This paper proposes a VAE-GAN-based method for reconstructing direct sequence spread spectrum (DSSS) signals. In this method, the deep residual shrinkage network (DRSN) and self-attention mechanism are added to the encoder and discriminator of VAE-GAN. In feature learning, the DRSNs can reduce the redundant information caused by noise in the collected signal. The self-attention mechanism can establish the long-distance dependence between the input sequences, making it easier for the network to learn the samples’ pseudonoise (PN) sequence features. In addition, feature loss is applied to the encoder and generator to improve network stability during training. The results of the experiments indicate that this method can reconstruct DSSS signals with the characteristics of the target signal.

TWO LEVEL IMAGE CRYPTOSYSTEM USING HYBRID-CHAOTIC KEY AND PRNG KEY FOR MULTI-MODALITY DIGITAL IMAGES WITH DISCRETE WAVELET TRANSFORM

In this information age, the need of secure picture transmission is critical. Medical data is hacked in the form of photographs, which costs more in terms of insurance claims. It is vital to safeguard photographs so that unauthorised individuals cannot view them. Chaos-based picture crypto systems are the most well-known of the several types of image crypto systems because their keys are invulnerable to assault or hacking. The chaotic features play a significant role in the development of keys for secure transmission and reception. The discrete wavelet transform (DWT) is a more basic transform that compresses the input image by combining approximation and detailed coefficients. The incorporation of the key in the approximate coefficients of the input image provides an efficient encryption when compared to other image crypto schemes. A two level image encryption is adopted in this work, where one level is achieved using the hybrid-chaotic sequences and the next level is utilizing the pseudo random noise sequence (PRNG) as the keys. A smaller value of variance value is achieved which shows the higher uniformity of pixel values in encrypted images of our proposed two level image cryptography. Also the better performance metrics in terms of entropy, NPCR, and UACI are achieved compared to a single level image encryption. The developed image crypto system is designed and simulated using MATLAB software package. KEYWORDS: two level chaos image cryptosystems, DWT, encryption, hybrid-chaotic maps, and PRNG key generation.

Randomized Spectral Separation Coefficient for Short Code Acquisition Performance Evaluation

Reliable signal acquisition with low computational complexity is an important design objective for the evolution of global navigation satellite systems (GNSS). Most GNSS signals consist of long pseudorandom noise (PRN) codes whose acquisition is expensive in terms of memory, computation time, and energy. As these resources are particularly scarce in the emerging mass-market user segment, cyclostationary pilot signals with short PRN codes are an attractive option to keep the number of acquisition search bins low. However, reducing the code length degrades the acquisition performance, as multiple access interference (MAI) becomes more pronounced and can lead to an increased false alarm rate. We demonstrate that, quite different from stationary MAI, cyclostationary MAI does not affect each bin of the search space uniformly, and is therefore not easily modeled with the well-known spectral separation coefficient (SSC). We propose a new randomized SSC (SSC-R) based on code/Doppler interference functions, which can be used for simple and accurate acquisition performance evaluation. As an application example, we demonstrate how the SSC-R can be utilized in signal design to minimize the PRN code length under an acquisition performance constraint. We conclude that feasible PRN code lengths for GNSS can be on the order of 300-700.

Sea Experimental for Compressive Sensing-Based Sparse Channel Estimation of Underwater Acoustic TDS-OFDM System

Due to the high spectral efficiency (SE) and fast synchronization, the time-domain synchronization orthogonal frequency division multiplexing (TDS-OFDM) system has gotten much more attraction of researchers as compared to cyclic-prefix (CP) and zero padding (ZP) OFDM in terrestrial as well as underwater acoustic communication. Inter-block interference (IBI) degrades the TDS-OFDM performance due to its long-delay multiple channels. In TDS-OFDM, dual pseudo-random noise (DPN) sequences utilize two PN sequences as a guard interval (GI) after every data block to cope with interference from the OFDM data block to the next PN sequence resulting in compromising the energy efficiency (EE) and spectral efficiency. We have proposed compressed sensing-based technique compressive sensing matching pursuit (CoSaMP), orthogonal matching pursuit (OMP), and look-ahead and backtracking OMP (LABOMP) for TDS-OFDM over the real-time underwater channel in this paper. Moreover, prior to estimating the channel, the received PN sequence is considered in the time domain to compensate for the Doppler shift of the UWA channel. The real-time data experiment has been initially conducted for testing in a water tank in our laboratory. Furthermore, it has been tested on the sea for long communications under the water at the Wuyuan sea area in Xiamen, China. Simulations and experimental results evident that the compressed sensing techniques have better performance over the conventional TDS-OFDM and DPN-TDS-OFDM, even LABOMP outperform OMP and CoSaMP in terms of bit-error-rate (BER), SE, and EE.

Optical CDMA MAC Evaluation in Vehicle-to-Vehicle Visible Light Communications

One of the most critical challenges in vehicle-to-vehicle (V2V) visible light communications (VLCs) is the access capability of multi-users over the same channel. VLC links are known to be line of sight (LOS) and highly directional compared to the commonly used radio-frequency (RF) technologies, but multi-user interference can still be problematic. Consequently, it is necessary to develop a medium access control (MAC) protocol for VLC. In the present work, we propose a novel optical code division multiple access (OCDMA) protocol. The fundamentals of the VLC channel are presented, and the interference problem is discussed in more detail. We also explain the CDMA MAC protocol and its adaptation from optical fiber communications. The simulations with our OCDMA protocol based on pseudo-noise (PN) sequence codes are presented, and the results are compared with those obtained using a solution based on VLC and optical orthogonal codes (OOCs) from the OCDMA gold standard. Finally, the results show that PN sequence OCDMA can provide sufficiently high performance and is particularly attractive because there are no synchronization requirements between nodes in real V2V scenarios.

Pulse Broadening Effects on Ranging Performance of a Laser Altimeter with Return-to-Zero Pseudorandom Noise Code Modulation.

A laser altimeter using code modulation techniques receives a backscattered pulse wider than the transmitted rectangular pulse when scanning a rough or sloped target surface. This leads to degrading the ranging performance in terms of signal-to-noise ratio (SNR) and detection probability. Unlike the pulsed techniques, little work has focused on the pulse broadening effect of the code modulation techniques. In this study, mathematical models were derived to investigate the pulse broadening effect on the ranging performance of a return-to-zero pseudorandom noise (RZPN) laser altimeter. Considering that the impulse response can be approximated by a Gaussian function, the analytical waveform was derived using a new flat-topped multi-Gaussian beam (FMGB) model. The closed-form expressions were also analytically derived for a peak cross-correlation, SNR, and detection probability in terms of the pulse broadening effect. With the use of a three-dimensional model of asteroid Itokawa for practical surface profiles, the analytical expressions were validated by comparing to the results obtained from numerical simulations. It was also demonstrated that the pulse broadening effect dropped down the peak cross-correlation and then deteriorated the ranging performance. These analytical expressions will play an important role in not only designing a laser altimeter using the RZPN code modulation technique but also analyzing its ranging performance.

Low Power Linear Feedback Shift Register Using DY-CML

A Linear Feedback Shift Register (LFSR) is a sequential shift register that cycles through a succession of binary values in a pseudo-random way using combinational logic. Pseudo-noise sequences, whitening sequences, and fast digital counters are some of the applications of LFSR. The design of a 4-bit LFSR employing CMOS, MOS Current-Mode Logic (MCML), and Dynamic Current-Mode Logic (DY-CML) approaches are shown in this paper. MCML has low power consumption and better performance. The disadvantage of MCML approach is that it has more static power dissipation due to the constant current source. In order to solve the issues of MCML approach, the DY-CML with a dynamic current source is used to design the LFSR. All designs are simulated using the Mentor graphics tool, which uses 90nm technology. This paper also includes a comparison of LFSR’s in terms of power, delay, and transistor count.

Gaussian Distributed Noise Generator Design Using MCU-STM32

The random noise signal is widely used as a test signal to identify a physical or biological system. In particular, the Gaussian distributed white noise signal (Gaussian White Noise) is popularly used to simulate environmental noise in telecommunications system testing, input noise in testing ADC (Analog to Digital Converter) devices as well as testing other digital systems. Random noise signal generation can be done using resistors or diodes. The weakness of the noise generator system using physical components is the statistical distribution. An alternative solution is to use a Pseudo-Random System that can be adjusted for distribution and other statistical parameters. In this study, the implementation of the Gaussian distributed pseudo noise generation algorithm based on the Enhanced Box-Muller method is described. Prototype of noise generation system using a minimum system board based on Cortex Microcontroller or MCU-STM32F4. From the test results, it was found that the Enhanced Box-Muller (E Box-Muller) method can be applied to the MCU-STM32F4 efficiently, producing signal noise with Gaussian distribution. The resulting noise signal has an amplitude of ±1Volt, is Gaussian distributed and has a relatively wide frequency spectrum. The noise signal can be used as a jamming device in a certain frequency band using an Analog modulator.

Underwater acoustic communication based on chirp spread spectrum with cyclic shifted PN sequences

In this presentation, we propose a new underwater acoustic communication technique that combines a binary PN (Pseudo Noise) sequence to which cyclic shift is applied and a CSS (Chirp Spread Spectrum) method that is robust against low Doppler shift. PN sequences are known to have sharp autocorrelation function and cyclic properties. In the case of the previous CSS method, 1-bit per symbol was mapped according to the sign of the slope in the time-frequency domain of the chirp signal, but the proposed method maps 2-bit per symbol according to the cyclic shift direction of PN sequence and the slope of the chirp. As a result, the transmission data rate is doubled. For example, “00” symbol is expressed as an up-chirp and right cyclic shifted PN sequence, and “11” symbol can be expressed as a down-chirp and left cyclic shifted PN sequence. This combination can have excellent autocorrelation properties and Doppler shift immunity. The performance of the proposed method will be compared with that of the previous method by presenting the results of the sea trial. [Work supported by the Agency for Defense Development, South Korea, Grant No. UD200002DD.]

Long-range underwater acoustic communication of M-eyry spread spectrum with cyclic prefix

The Spread Spectrum is an effective transmission method for complex channels in underwater acoustic (UWA) communication because of the high correlation of pseudo-random noise (PN) sequence. In particular, the spread spectrum method is effective in an environment with a low signal-to-noise ratio. The bandwidth of UWA communication channel is limited due to the fact that sound wave attenuation in water is positively associated with frequency. The limited bandwidth directly leads to the low data rate of conventional direct-sequence spread spectrum UWA communication. M-ary spread spectrum (MSS) schemes using multiple orthogonal PN sequences were proposed as a solution to this problem. However, even in the MSS method, the performance may be limited by the delay spread characteristics in the multipath propagation channels. We propose a more robust communication method in the UWA channel by including Cyclic Prefix (CP) to achieve a more robust performance in the multipath channel. In the proposed method, a CP is inserted for every symbol. In the 160 km long-range UWA communication experiment conducted in the East Sea, the proposed method showed more reliable results than the conventional MSS method. [Work supported by the Agency for Defense Development, South Korea, Grant No. UD200010DD.]

The frame synchronization robust to low signal power in underwater acoustic communications

In underwater acoustic communications, it is difficult to find the starting time of received signals because of noise, multipath, transmission time delay, and Doppler frequency. In this paper, we solve the problem by using 2-STEP frame synchronization in the receiver. The transmitted signal is modulated by using burst PSK. The frame is composed of preamble of PN code and random data. The 2-STEP frame synchronization consist of non-coherent correlation, sliding FFT, and coherent correlation. First, in the STEP 1, the non-coherent correlation and sliding FFT are simultaneously performed to obtain an approximate start time of a frame in time domain and a Doppler frequency in frequency domain. However, through the results of the marine experiments, we can see that it is difficult to guarantee the starting time point in STEP 1 when the received signal power is weak and there is high Doppler frequency. Therefore, in the STEP 2, we use the coherent correlation to get more accurate start time stably after compensating the Doppler frequency of FFT in STEP 1. Finally, we can assure that the performance of the proposed 2-STEP frame synchronization is robust to low power of received signal and high Doppler frequency through marine experiments.

Joint equalizer and phase-locked loop for time variability in underwater acoustic communications

In this paper, we verify the performance of the equalizer and phase-locked loop (PLL) operating jointly for channel time variability in underwater acoustic communications. We apply the decision feedback equalizer in order to eliminate channel multipath and PLL to phase rotation due to Doppler effects. In the PLL, a decision-directed tan−1 type phase detector is adopted. As shown in previous papers, it is difficult to make PLL to be steady state because of time-varying ISI occurred by multipath. Also, the phase rotation incurs the equalizer tap rotation. Therefore, we can see that the two subsystems of equalizer and PLL complement each other perfectly. Another issue is the convergence speed; how quickly we can make the joint equalizer and PLL to be stable state within the preamble period (known data). In order to verify the performance, the sea experiments were conducted in the condition of moving transmitter. The transmitted signal is modulated by using PSK and consists of five burst frames that are composed of preamble of PN code and random data. As a result, if we use the initial multipath value and Doppler frequency offset, we can make the joint equalizer and PLL to be the steady state more quickly.

Specification of downlink-fixed reference channel DL-FRC for 5G new radio technology

<p>The next generation for mobile communication is new radio (NR) that supporting air interface which referred to the fifth generation or 5G. Long term evolution (LTE), universal mobile telecommunications system (UMTS), and global system for mobile communication (GSM) are 5G NR predecessors, also referred to as fourth generation (4G), third generation (3G) and second generation (2G) technologies. Pseudo-noise (PN) code length and modulation technique used in the 5G technology affect the output spectrum and the payload of DL-FRC specification, in this paper quadrature phase shift keying (QPSK), 16 QAM modulation approaches tested under additive white Gaussian noise (AWGN) in term of bit error rate (BER) which used with 5G technology system implemented with MATLAB-Simulink and programing and, resulting of 1672, 12296 bit/slot payload at frequency range FR1 from 450 MHz-6 GHz and 4424, 20496 bit/slot payload at frequency range FR2 from 24.25 GHz-52.6 GHz, also determining subcarrier spacing, allocated source block, duplex mode, payload bit/slot, RBW (KHz), sampling rate (MHz), the gain and the bandwidth of main, side loop where illustrated.</p>

Pseudo-random noise generator based on FPGA

This paper proposes a novel pseudo-random noise generator based on FPGA. The system architecture is written by Verilog, and each sub-module is designed in Vivado software. Modelsim is employed to co-simulate the sub-modules and the saved data is imported to Matlab for spectrum analysis. Consequently, the proposed design can be applied to practical noise generating with great scalability and flexibility.

Four-Channel Interference of Dual-Antenna GNSS Reflectometry and Water Level Observation

The signals at higher elevation angles could be received by a left-handed circularly polarized (LHCP) antenna because LHCP components dominate the reflected signals at higher elevation angles. This letter explores a four-channel interference method of dual-antenna global navigation satellite system (GNSS) reflectometry capable and its application in retrieving the water level. Compared to single-antenna observation using a oscillating signal-to-noise ratio (SNR), due to the capability of receiving the reflected signals at high elevation angles, the proposed method has higher temporal resolution. The criterion based on the effective value of the time series is proposed to evaluate the quality of oscillating carrier phase difference. The Lomb–Scargle method and cosine fitting are used to estimate the oscillated frequency of carrier phase difference. Through normalizing cosine oscillation and time scale by the GNSS signal amplitude and wavelength, the time-series from multisatellites could be combined to retrieve the height. At last, the experiment is conducted to demonstrate the proposed method, and the results show that when the criterion threshold is under 0.2, the centimeter-level precision of the retrieved height could be achieved. Two-satellite observation combining satellite pseudorandom noise (PRN) 15 and 24 could decrease the time span of the observation to 320 s from 480 s for only using single satellite, and the root mean square error (RMSE) reduces to 6.2 cm from 9.5 and 18.9 cm of the satellite PRN 15 and 24.

A Modified PRBS: Vertical Stacked LFSR Primitive Polynomial for Secure Data Communication

Linear Feedback Shift Register (LFSR) generates the fault coverage test patterns to compute the target fault of data compression methods. Future Generation wireless communication covers irrespective of complex situation and dense environments marginable throughput to everyone. LFSR widely applied to generate Pseudo Random Noise Sequence, Digital Random Number Generator commonly employed in Cryptography, encoding techniques, Built in Self-Test (BIST) etc. Sequence generated by the LFSR are easily predictable as periodic nature of the sequence. A Modified Pseudo Random Sequence Generator (PRBS) with vertical stacked LFSR (VS-LFSR) is proposed to improve security against predictability nature of PRBS. The primitive polynomial of the nbit LFSR is vertically stacked with top most polynomial and ends with the least polynomial with this flexible of the primitive polynomial are processed and Random sequences are generated. The proposed method generates the random numbers of flexible ranges by appropriately selecting necessity primitive polynomial code in the vertical stack. Compare to conventional LFSR, all zero (0) states also generated in the VS-LFSR, enables the test pattern to have all 2npossible states of n-bit LFSR. With little hardware complexity, periodic pattern of LFSR is further improved with the maximum number of states and result attained maximum number of random outputs as Πn-202n-m - 1.

Prenos u proširenom spektru - frekvencijsko skakanje - istorija, principi i primena

Introduction/purpose: The frequency hopping spread spectrum (FH-SS) technique assumes the carrier generated by the syntesizer to hop from frequency to frequency over a wide bandwidth, according to a pseudonoise code sequence defined by the code sequence generator. The article presents the history, principles and applications of the FH-SS technique. Both military and commercial applications are discussed. Methods: This article presents an overview of data from the technical literature, with appropriate comments. Results: After presenting the history and principles of the FH-SS technique, the article summarizes its use with examples of military and commercial applications. The importance of using FH-SS in the described applications is highlighted. Conclusion: The FH-SS technique has been successfully implemented in many military and commercial technologies due to its high protection against interference, making communication difficult for reconnaissance and eavesdropping, and its ability to provide code division multiple access.

ADAPTIVE TECHNIQUE TO PHASE ESTIMATION IN PSEUDO-NOISE INFORMATIVE SIGNAL OF DOPPLER RADAR FOR RESCUERS

ADAPTIVE TECHNIQUE TO PHASE ESTIMATION IN PSEUDO-NOISE INFORMATIVE SIGNAL OF DOPPLER RADAR FOR RESCUERS

Design a system for an approved video copyright over cloud based on biometric iris and random walk generator using watermark technique

Copyright is a tool for preventing anyone forged to copy an electronic work from another person and claim that electronic work is referred to him. Since the identity of the person is always determined by his name and biometrics, there is a concern to handle this information, to preserve the copyright. In this paper, a new idea for copyright technology is used to prove video copyright, by using blind watermarking technique, the ownership information is hidden inside video frames using linear congruential generator (LCG) for adapted the locations of vector features extracted from the name and biometric image of the owner instead of hidden the watermark in the Pseudo Noise sequences or any other feature extraction technique. When providing the watermarked vector, a statistical operation is used to increase randomization state for the amplifier factors of LCG function. LCG provides random positions where the owner's information is stored inside the video. The proposed method is not difficult to execute and can present an adaptable imperceptibility and robustness performance. The output results show the robustness of this approach based on the average PSNR of frames for the embedded in 50 frames is around 47.5 dB while the watermark remains undetectable. MSSIM values with range (0.83 to 0.99).