Spread Spectrum Technology Research Articles

Design and Implementation of a Long Range Wireless Data Acquisition System for Photovoltaic Installation based on LoRa Technology

In this paper, a low power consumption long range wireless data acquisition system for PV installations, consisting of a set of sensors connected wirelessly with one or several monitoring/control systems was designed and implemented. The wireless communication between devices is based on LoRa technology. LoRa is a spread spectrum modulation technique derived from Chirp Spread Spectrum (CSS) technology. It offers a long-range low power wireless platform, suitable for professional wireless sensor network applications. The integration of this technology in PV installations provides an extensive, low cost, power-efficient, and easy to maintain, system. Design, high-layer communication protocol, and hardware implementation of sensors are discussed. The sensor set consists of a voltage/current sensor, a sun irradiance sensor, a panel position sensor based on an accelerometer/magnetometer for sun tracking installations, a temperature and humidity sensor, and a mobile monitoring system.

Review Paper on LoRa based technologies for Vehicular and Tracking applications

Abstract: LoRa stands For Long Range. It is a low powered wide area network derived from chirp spread spectrum technology and encodes information through chirp pulses on to the radio waves. The range of LoRa greatly varies from few meters to approximately 100 Kilometers depending on the mode of operation. The main advantage of LoRa against Bluetooth, WiFi and ZigBee is its long range and it is well suited for transmission of small chunks of data with low bit rates. LoRa is generally operated at 915MHz, 868MHz and 433MHz which are Sub-Giga Heartz bands. These are a part of the ISM bands which are reserved for Industrial and Medical Purposes Internationally which are free of cost and do not require any kind of licensing. Vehicular communication is a form of exchanging messages between various vehicular and roadside units regarding their location, speed and much more. The LoRa technology when integrated with Vehicular Communication establishment of green corridors for Emergency vehicles by clearing the traffic and help in reaching the destination with minimal time delay. Keywords: LoRa, ISM Bands, Vehicular Communication

Toward Physical Layer Security and Efficiency for SAGIN: A WFRFT-Based Parallel Complex-Valued Spectrum Spreading Approach

Space-air-ground integrated network (SAGIN), as an integration of interconnected space, air, and ground network segments, is expected to see prevalent usage as part of intelligent transportation systems (ITS), providing an enhanced service provision in terms of coverage, flexibility and reliability. However, restricted by the limited and unbalanced network resources, the efficiency and security of the underlying connectivities of SAGIN are of utmost concern for ITS applications. In this paper, a weighted fractional Fourier transform (WFRFT) based parallel complex spreading (PCS) approach is proposed to improve the communication efficiency and security of SAGIN at the physical (PHY-) layer. The concept of WFRFT along with the direct sequence spread spectrum technology establish the security kernel of the proposed scheme. The practicability of the complex-valued WFRFT-spreading architecture is verified by studying the correlation properties of the WFRFT-spreading signals. Taking advantages of the signal uniqueness of WFRFT, the proposed scheme is capable of providing more flexibility in signal characteristic control. Moreover, the complex-valued WFRFT-spreading processing makes the proposed scheme inherently robust against the large Doppler shift distortions in SAGIN. Simulation results demonstrate the superiority of the proposed WFRFT-PCS scheme in terms of communication efficiency and PHY-layer security. Finally, as a proof of concept, an all-digital FPGA prototype system is designed to show the practicability and the performance enhancement of the proposed scheme.

Communication and ranging composite system based on parallel combinatory spread spectrum technology

Communication and ranging composite system based on parallel combinatory spread spectrum technology

Communication and ranging composite system based on parallel combinatory spread spectrum technology

Communication and ranging composite system based on parallel combinatory spread spectrum technology

Uplink grant‐free pattern division multiple access transmission scheme by exploiting poly complementary sequence

AbstractNon‐orthogonal multiple access (NOMA) technology is a key technology of the future cellular mobile communication system. It provides services for users under different channel conditions through signal superposition transmission and spectrum multiplexing. Pattern division multiple access (PDMA) is a new NOMA technology based on the overall optimization of multi‐user communication system. Since the performance of PDMA mainly depends on the gain of the pattern matrix, we propose a design scheme of uplink PDMA pattern matrix for ultra‐reliable low latency communication (uRLLC). For the interference between users is a common problem in NOMA system, first, we use poly complementary sequence (PCS) as the spread codebook to spread the PDMA transmission signal and reduce interference. Meanwhile, an uplink power control scheme is proposed. It allocates wireless resources reasonably by jointly considering the interference between users and resource blocks within users (JUR), the corresponding outage probability formula is also derived. Simulation results show that compared with the previous researches, the pattern matrix design scheme and JUR power control scheme proposed in this article have greatly improved the transmission performance. The addition of PCS spread spectrum technology can significantly reduce the block error rate and outage probability.

Generalized Complementary Coded Scrambling Multiple Access for MIMO Communications

Spectrum efficiency is a critical performance metric in wireless communications due to an increasing demand for radio spectrum to support high data rate applications. Direct sequence spread spectrum technology enables a code division multiple access (CDMA) system a strong anti-interference capability but with a relatively low spectrum efficiency. To address this issue, complementary coded scrambling multiple access (CCSMA) (X. Liu <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">et al</i> ., in 2018) was proposed to use three-dimensional (space-time-frequency) resources for performance enhancement. However, in a CCSMA system, if the number of multipath returns is larger than the number of transmit (Tx) antennas, a code reuse problem occurs to degrade bit error rate performance significantly. This work designs a new scrambling code, namely generalized complementary coded scrambling multiple access (GCCSMA) codes, to overcome the code reuse problem in CCSMA. GCCSMA uses complementary codes, scrambling modulation, and multiple-input-multiple-output (MIMO) techniques jointly, which works well even in multipath channels with more paths than the number of Tx antennas. The analysis and simulations are conducted to validate the effectiveness of the proposed GCCSMA system.

User Capacity Analysis of Space-Based Internet of Things with Multibeam Techniques

Space-based Internet of Things (S-IoT) utilizes the characteristics of satellite network coverage, strong antidestructiveness, and full-time work to realize large-scale sensing and interconnection of everything in the sky, land, sea, and air. The user capacity of S-IoT satellites is mainly determined by beam design, communication schemes, satellite-to-earth links, and communication protocols, which directly affect the system capacity and operational capabilities of S-IoT. This paper proposes an S-IoT satellite user capacity analysis model with multibeam and spread spectrum technology. Taking into account the randomness of user distribution, the difference in transmit power, and different spreading sequences, the user capacity of S-IoT satellites was simulated and compared in different scenarios. Based on these results, this article analyzes the key factors affecting user capacity, which will provide a valuable reference for S-IoT design, link optimization, and power selection.

Interference Mitigation in Wireless Communication – A Tutorial on Spread Spectrum Technology

Interference Mitigation in Wireless Communication – A Tutorial on Spread Spectrum Technology

DESAIN SIMULASI UNJUK KERJA KODE SMALL KASAMI PADA KANAL MULTIPATH FADING

Telecommunication capable of handling interference, fading and no less importantissues regarding the confidentiality of user information is very much needed in the currenttechnological era, to overcome this spread spectrum technology is quite developed in theadvancement of telecommunication technology. In this study, the small kasami code was usedas the spreading code. The purpose of this study is to determine the performance of the smallkasami code with changes in the number of multipath components using multipath fadingchannels. The modulation technique uses digital modulation, namely binary phase shift keying(BPSK) with a small kasami code with a code length of 15 in the spreading and spreadingprocess. Analyzed based on BER (Bit Error Rate) versus EB/No (Energy Bit per Noise). In thesimulation of flat fading performance using 1 multipath component, flat fading serves as an idealreference where the simulation BER should resemble the theoretical BER as simulationvalidation so that it can be used on selective fading channels. Variation of multipathcomponents in frequency selective fading channel produces different BER because there isinterference of multipath signal to the desired signal. The number of multipath components asmany as 11 have the most interference signals resulting in the worst performance. The value ofcross correlation between users has poor performance, where the correlation value of user 1with 2, 3, and 4 is more than 0, this value shows that many signal levels experience interferencebetween users.

Optical domain despreading method of optical time-domain reflectometer using spread spectrum technology

The advantages of optical time-domain reflectometer (OTDR) using spread spectrum technology are analyzed briefly. For the shortcomings of spread spectrum OTDR in traditional despreading method, the concept of optical domain multiplier is first proposed, i.e., the most important multiplication operation in despreading is realized by modulating the phase of Mach–Zehnder modulator before photoelectric conversion. The proposed two methods of despreading in optical domain overcome the electronic bottleneck of correlative despreading in electrical domain, and solve the various restrictions on the application of high-speed spreading code in OTDR. Simulations verify the correctness and feasibility of the two methods.

REAL TIME SEARCH OF AGRICULTURAL MACHINERY BASED ON MATRIX SEQUENCE SENSOR

Omni-directional vision sensor can provide information within the sensor range, and the directional angle of an object can be accurately obtained through omni-directional images. Based on this characteristic, an automatic navigation and positioning system for agricultural machinery is developed, and a three-dimensional positioning algorithm for agricultural wireless sensor networks based on cross particle swarm optimization is proposed. The method mainly includes three stages: convergence node selection, measurement distance correction and node location. Using the idea of crossover operation of genetic algorithm for reference, the diversity of particles is increased, and the influence of ranging error and the number of anchor nodes on positioning results is effectively improved. The location algorithm has the ability of global search. On the positioning node, the symmetric bidirectional ranging algorithm based on LFM (Linear frequency modulation) spread spectrum technology is used to calculate the distance between the positioning node and each beacon node, and the trilateral centroid positioning algorithm is used to calculate the coordinate position information of unknown nodes. Finally, the Kalman filter algorithm is used to superimpose the observed values of the target state to solve the influence of measurement noise on the positioning accuracy.

Performance Simulation of Underwater Acoustic Spread Spectrum Communication Based on LDPC Code

As we all know, the underwater acoustic channel is a time-varying, space-changing, and frequency-varying fading channel with limited bandwidth and severe noise interference. This paper studies and analyzes the main factors restricting the transmission of underwater acoustic channels, and establishes an underwater acoustic multipath time-varying fading channel. The channel coding adopts Quasi-Cyslic Low-Density Parity-Check Codes (QC-LDPC), combined with spread spectrum technology and high-order modulation technology, and utilizes Log-likelihood Ratios Belief Propagation (LLR-BP) is decoded, the simulation results show that LDPC codes have stronger error correction capabilities in underwater acoustic spread spectrum communication systems, ensuring that the system can operate reliably under low SNR conditions.

Mapping Algorithm of Multi - code combination spread spectrum technology for Short Packet Transmission

Multi-code combined spread spectrum (MCSS) is based on M-ary spread spectrum to improve information payload by combining multiple spread spectrum sequences, which solved the contradictions between spread spectrum gain and transmission efficiency under limited channel bandwidth conditions. This paper focuses on two mapping algorithms of multi-code combination spread spectrum and their decoding algorithms for MCSS, which transmits the information by combining multiple spreading sequences. The R-combined mapping algorithm is provided to keep the sequence orthogonal and the design complexity increases with the increase of the number of correlators at the receiver while the SVC algorithm is adopted and MMP algorithm is used to realize multi-code combination spread spectrum with increasing sequences. The BER performance of the two algorithms is compared through simulation analysis

The Simulation Study of Multi-User Spread-Spectrum Wireless Communication System

Spread-spectrum technology is a promising and effective is an effective technique using for multiple accessing, combating multi-user interference and rejecting unwanted radio jamming. In this paper, we explore the effect of Direct Sequence spread-spectrum (DSSS) which base on π/4-DPSK modulation and demodulation technique, we provide a multi-user spread-spectrum wireless communication system and the system performance was studied from simulation and comparison. Four users information are transmitting over Rayleigh fading channel to model the 5G communication environments. The performances of the system are expressed through comparisons of the bit-error rate (BER) and signal to noise ratio (SNR) for both original signals at transmitter and recovered signals at receiver. From the contrast results, the anti-multi-user interference ability of the system is provided.

A New Protection Scheme for Biometric Templates based on Random Projection and CDMA Principle

Although biometric technologies have revolution-ized the world of communication and dematerialized exchanges, authentication by biometrics still has many limitations, particu-larly in terms of privacy concerns, due to the various potential threats to which biometric templates are subject. The existence of these vulnerabilities has created an enormous need for biometric data protection. Indeed, several protection schemes have been proposed, which are normally supposed to offer certain guaran-tees, including the confidentiality of the collected personal data and the reliability of the recognition system. The challenge for all these techniques is to achieve a trade-off between performance ac-curacy and robustness against vulnerabilities, which is not always obvious. In this paper, we propose a theoretical protection model dedicated to biometric authentication systems. The objective is to ensure a high level of security for the stored reference data in such a way that it complies with the non-invertibility and revocability properties. The main idea is to incorporate a discretization tool, namely the spread spectrum technology and in particular the Code Division Multiple Access (CDMA), into a biometric system based on Random Projection. We introduce and demonstrate the proposed scheme as a non-invertible transform, while proving its effectiveness and ability to meet the requirements of revocability and unlinkability.

PERFORMANCE ANALYSIS OF DS-CDMA SYSTEM FOR UNDERWATER ACOUSTIC COMMUNICATIONS

We choose direct sequence spread spectrum (DSSS)technologies combined with Rake receiver under the modulation of BPSK to establish the communication modem. The performance of the modem is extensively investigated by MATLAB based simulation. We analysis the bit error rates (BER) against signal to noise ratio (SNR) corresponding to different parameter settings, for instance, under different Pseudo noise (PN)codes, the long of PN code period, the modulation schemes. Regarding to the Rake receiver, we also compare the scatter plots to deduce whether rake has better performance than without rake, furthermore we change the taps of the rake and diversity combining schemes to continue comparing the BER performance. The modem is implemented in a linear time invariant (LTI)channel model.

Research on Clock Circuit Electromagnetic Emission Test and Suppression

Clock circuit is an important part of PCB, which is usually composed of crystal oscillator, crystal oscillator control chip and capacitor. Electromagnetic emission generated by clock circuit is one of the main interference sources of electronic equipment. According to the different transmission paths, electromagnetic interference caused by clock circuit usually includes conduction interference and radiation interference. When the electromagnetic emission generated by the clock circuit reaches a certain degree, it may affect the electromagnetic compatibility of electronic equipment. In this paper, by analyzing the frequency spectrum characteristics of the clock signal, the difference of the frequency spectrum of the clock signal under different parameters is compared, and the electromagnetic emission test method is given. On this basis, when the EMI suppression method of clock circuit is studied, a series of EMC design methods of clock circuit are summarized, and the application of spread spectrum technology in clock circuit is proposed.

Energy Enhancement Techniques for Structure-Free Wireless Sensor Network with Encrypted Data

Background: Nowadays, in military and border surveillance application, the WSNs become an effective part of the command and control system. This requires an efficient type of cryptography. Due to small size requirement, elliptic curve becomes the most suitable for such purpose. Objective: The encryption operation, in turn, increases the power required to transmit data through the network. The aim of this work is to reduce such power. Methods: This work suggests three methods to reduce the needed power. The first method is based on spread spectrum technology, which reduces the total number of levels in the network. The second method deals with algorithm used to choose the sensing node, while the third method suggests a cost function related directly to the available energy. Results: Computer simulation tests show a reduction in the required energy by 40% when we apply the first method, while the second and third methods together reduce the energy by 12% of the total value of the whole network. Conclusion: The energy required to transmit encrypted data can be reduced with the aid of routing algorithms. These algorithm increase the coverage radius of the node transmission.

Research on modulation recognition of Communication Radar Based on spread spectrum technology

Aiming at the problem that the traditional radar signal recognition method needs to be completed under the noiseless condition, which leads to the low recognition accuracy of low SNR signal, the modulation recognition method of communication radar signal based on spread spectrum technology is studied. The phase difference and instantaneous frequency characteristics of communication radar signal are extracted after the spread spectrum processing of communication radar signal with direct sequence spread spectrum. The training sample is used to train PNN neural network, and the modulation recognition of communication radar signal is completed. Simulation experiments under different parameters show that the recognition method based on spread spectrum technology has an effective recognition rate higher than 90% for low SNR signal, which is superior to the traditional method and can be applied in practice.