Direct Sequence Spread Spectrum Cdma

This paper presents the architecture as well as the circuit implementation of a ZigBee transceiver using 2.45 GHz band, which is compliant with the physical layer of IEEE 802.15.4 standard. A prototypical system and chip has been designed using 0.18-μm CMOS process with core area of 0.16 mm 2 . The simulation results shows the packet error rate is less than 1% given E b /N 0 = 9 dB. The total power consumption is merely 271 μW at a 8.0 MHz system clock.

In this paper, a new technique to monitor and control bidirectional DC-DC converter was designed and implemented precisely. A prototype of a complete system is verified with efficient communication capabilities. This system is realized by integrating the internet of things (IoT) operating system and the bidirectional DC-DC converter. The IoT communication facilities further develop and extend the platform for this system. The DC-DC converter with the soft switching technique will then convert the battery voltage to a high voltage of 380V inverter bus in emergencies via boost converter mode. High-frequency toroidal transformer has been used for power level shifting and isolation between the primary and secondary sides of the transformer. The closed-loop control scheme is implemented in software by using a high-performance 32-bit STM32 microcontroller. IoT technique is used to find current, voltage and perform the communication smoothly through Wi-Fi sensors to complete the design of the system. The results of the proposed system prove the effectiveness of the proposed system with high-performance specifications.

The present explosion in digital communications and multi-user wireless cellular networks has urged a demand for more effective modulation methods, utilizing the available frequency spectrum more efficiently. To accommodate a large number of users sharing the same available frequency band, one requirement is the availability of large families of spreading sequences with excellent AC and CC properties. Another requirement is the availability of sets of orthogonal basis functions to extend capacity by exploiting all available degrees of freedom (e.g., temporal, frequency and spatial dimesions), or by employing orthogonal multi-code operation in parallel, such as used in the latest 3GPP and 3GPP2 Wide-band Code Division Multiple Access (WCDMA) modulation standards by employing sets of orthogonal Walsh codes to improve the overall data throughput capacity. The generic Direct Sequence Spread Spectrum (DSSS) transmitter developed in this dissertation has originally been designed and implemented to investigate the practicality and usefulness of complex spreading sequences, and secondly, to verify the concept of non-linearly interpolated root-of-unity (NLI-RU) filtering. It was found that both concepts have a large potential for application in point-to-point, and particularly micro-cellular Wireless Local Area Networks (WLANs) and Wireless-Local-Loop (WLL) environments. Since then, several novel concepts and subsystems have been added to the original system, some of which have been patented both locally and abroad, and are outlined below. Consequently, the ultimate goal of this research project was to apply the principles of the generic DSSS transmitter and receiver developed in this study in the implementation of a WLL radio-frequency (RF)-link, and particularly towards the establishment of affordable wireless multimedia services in rural areas. The extended coverage at exceptionally low power emission levels offered by the new design will be particularly useful in rural applications. The proposed WLL concept can for example also be utilized to add a unique mobility feature to for example existing Private Automatic Branch Exchanges (PABXs). The proposed system will in addition U Un ni iv ve er rs si it ty y o of f P Pr re et to or ri ia a e et td d --M Ma ar rx x, , F F E E ( (2 20 00 05 5) ) offer superior teletraffic capacity compared to existing micro-cellular technologies, e.g., the Digital European Cordless Telephony (DECT) system, which has been consider by Telkom for employment in rural areas. The latter is a rather outdated interim standard offering much lower spectral efficiency and capacity than competitive CDMA-solutions, such as the concept analyzed in this dissertation, which is based on the use of unique large families of spectrally well confined (i.e., band-limited) constant envelope (CE) complex spreading sequences (CSS) with superior correlation properties. The CE characteristic of the new spreading sequences furthermore facilitates the design of systems with superior power efficiency and exceptionally robust performance characteristics (much less spectral re-growth) compared to existing 2G and 3G modulation standards, in the presence of non-linear power amplification. This feature allows for a system with larger coverage for a given performance level and limited peak power, or alternatively, longer battery life for a given maximum communication distance and performance level, within a specified fixed spreading bandwidth. In addition, the possibility to extend the concept to orthogonal multi-code operation provides for comparable capacity to present 3G modulation standards, while still preserving superior power efficiency characteristics in non-linear power amplification. Conventional spread spectrum communication systems employ binary spreading sequences, such as Gold or Kasami sequences. The practical implementation of such a system is relatively simple. The design and implementation of a spread-spectrum communication system employing complex spreading sequences is however considerable more complex and has not been previously presented, nor been implemented in hardware. The design of appropriate code lock loops for CSS has led to a unique design with 3dB performance advantage compared to similar loops designed for binary spreading sequences. The theoretical analysis and simulation of such a system will be presented, with the primary focus on an efficient hardware implementation of all new concepts proposed, in the form of a WLL RF-link demonstrator.

A novel servomotor design that is powered and controlled through only one wire is presented in this paper. A traditional servonzotor needs both a power cable and a control cable connecting the motor to a control amplifier. Cables are bulky, heavy, and expensive and, more iniportuntly, dijjcult to install and maintain in many applications. Particularly for multi-axis applications, like robots and machine tools, cable harnesses become thick and long, and are dijjcult to run through a stack of many axes, being a major burden and bottleneck in electromechanical drives. The objective of this research is to eliminate such bulky cables by integrating and consolidating power cables and signal cables into a single wire, and transmitting control signals through the signal wire. Signals are coded by using a CDMA protocol and are superimposed on the single wire that supplies a DC voltage to each motor. In this paperJirst the principle of reduced-cable smart motors is described, followed by the architecture of signal transmission system using direct sequence spread spectrum. A prototype system is designed, and the signal transmission line is simulated to verifi the principle.

A signal transmitted in an Underwater Acoustic Communication (UAC) system operating in a shallow-water channel suffers from strong time dispersion due to multipath propagation. This causes the Inter-Symbol Interference (ISI) observed in the received signal, which significantly limits the communication system’s reliability and transmission rate. In such propagation conditions, the Direct-Sequence Spread Spectrum (DSSS) method is one of the solutions that make reliable data transmission possible. In systems with one-to-one communication, it ensures communication with a satisfactory Bit Error Rate (BER). Additionally, it makes it possible to implement the Code-Division Multiple Access (CDMA) protocol in underwater acoustic networks. This paper presents the results of simulation and experimental communication tests on a DSSS-based UAC system using three types of spreading sequence, namely m-sequences, Kasami codes and Gold codes, and occupying different bandwidths from 1 kHz to 8 kHz ar...

Low energy adaptive clustering hierarchy (LEACH) guided a considerable portion of the research, and is used as benchmark, in energy efficient data gathering schemes in wireless sensor networks. In it, the probabilistic and randomized selection strategy of clusterhead selection results in their variable number, during different rounds of data gathering. To avoid communication interference in different clusters it uses Direct Sequence Spread Spectrum (DS-SS) technique, which spreads the signal by multiplying it with a spreading signal, and thus results in increased data size. The variable number of clusterheads requires the spreading factor to be set corresponding to the probable maximum number of clusterheads, to avoid collisions. This increases the data size and correspondingly the amount of energy required to transmit it to the base station. This letter presents the effect of spreading factor on the data gathering performance of LEACH scheme with its simulation in NS-2. The obtaine...

The aim of the present paper is to increase the reliability of a Kalman filter-based DS-SS receiver by considering in the state space models the multipath coefficients and associated delays. The objective being to operate at very low SNRs in shallow water (to achieve furtive transmissions) and with the need of a limited computational cost, the implementation relies on the Unscented Kalman Filter, which is known to be more robust than the popular Extended Kalman Filter. The proposed receiver schemes are discussed and compared using experimental data.

Data-driven decision making is the key to providing effective and efficient wildfire protection and sustainable use of natural resources. Due to the complexity of natural systems, management decision(s) require clear justification based on substantial amounts of information that are both accurate and precise at various spatial scales. To build information and incorporate it into decision making, new analytical frameworks are required that incorporate innovative computational, spatial, statistical, and machine-learning concepts with field data and expert knowledge in a manner that is easily digestible by natural resource managers and practitioners. We prototyped such an approach using function modeling and batch processing to describe wildfire risk and the condition and costs associated with implementing multiple prescriptions for risk mitigation in the Blue Mountains of Oregon, USA. Three key aspects of our approach included: (1) spatially quantifying existing fuel conditions using ...

This paper concentrates on building a multi-antenna FPGA based Channel Sounder with single transmitter and multiple receivers to realize wireless propagation characteristics of an indoor environment. A DSSS signal (spread with a real maximum length PN sequence) is transmitted, which is correlated with the same PN sequence at each receiver to obtain the power delay profile . Multiple power delay profiles are averaged and the result is then sent to host. To utilize high bandwidth, the computationally expensive tasks related to generation and parallel correlation of PN sequences are moved to the FPGA present in each USRP (Universal Software Radio Peripheral). Channel sounder blocks were built using Vivado HLS and integrated with RFNoC (RF Network on Chip) framework, which were then used on USRP X310 devices.

It is very difficult to design an underwater communication system because of multipath, Doppler effects, noise, and attenuation. These factors lead to errors in the communication performance and maximum propagation distance. In this study, we calculate the distance that can be realized using the direct-sequence code division multiple access (DS-CDMA) technique with direct-sequence spread spectrum (DSSS) in an underwater communication system considering only the attenuation and noise. We also compare the estimated and calculated propagation distances obtained for several different scenarios.

This paper proposes a novel method for acoustically and wirelessly transmitting data underwater with a high transmission rate. The method uses the most promising physical layer and multiple access technique (i.e., the code division multiple channel access technique) to divide the channel into subchannels. Data is transmitted through these subchannels. The codes are pseudo-random noise (PN) sequences. In the spread-spectrum technique, a signal such as electrical, electromagnetic, acoustic signal generated in a particular bandwidth is deliberately spread in the frequency domain, which results in a signal with a wider bandwidth. This paper reviews the possibility of application of the direct-sequence code division multiple access (DS-CDMA) technique in an underwater system using MATLAB. As the result of our review, we recognize that the DS-CDMA technique can be applied to underwater environments.

The FHSS and DSSS technologies are described as well as different types of spread coding. DSSS systems can provide higher access data rates (up to 11Mbit/s) than FHSS systems (up to 3Mbit/s). More FHSS systems can operate simultaneously in the same area than DSSS systems. DSSS systems have higher interference susceptibility tolerance levels. However, if there is a strong broadband interferer in the operational spectrum, FHSS systems will suffer less due to frequency hopping. Assuming equal transmit powers, DSSS systems have lower power spectral density due to wider operating spectrum. Monte Carlo analysis results show that DSSS systems are more likely to cause interference than FHSS systems. The worst case interference levels are higher when the interferer is FHSS system. It was shown that this case has a very low probability of occurring.

Building on the theoretical foundations established in FIRECAST I, this paper presents comprehensive operational validation, benchmark comparisons with existing systems, and scalability analysis for real-world deployment of AI-optimized aerial firefighting dispatch. We validate FIRECAST through highfidelity discrete-event simulation of the August 2020 California lightning siege-the largest mass-ignition event in modern history-using 42,807 NASA FIRMS satellite fire detections. Benchmark comparisons against CAL FIRE's current dispatch procedures, commercial wildfire management systems (Technosylva FSIM, Esri ArcGIS Wildfire), and academic baselines demonstrate 38.7% reduction in weighted response time and 23.4 percentage point improvement in initial attack success rate. We present detailed cost-benefit analysis showing ROI ranging from 71:1 to 264:1 depending on fire season severity, with breakeven achieved within 2 weeks of deployment. Scalability analysis extends FIRECAST from California (163,696 mi²) to continental United States (3.8M mi²), Australia (2.97M mi²), and Mediterranean Europe (890K mi²), with region-specific adaptation costs estimated at $2.1-8.2M per deployment. We address key operational challenges including human-AI teaming, regulatory compliance, liability frameworks, and integration with existing Computer-Aided Dispatch (CAD) systems. This paper provides the technical and economic foundation for deploying AIoptimized dispatch at scale, with implications for fire agencies, insurers, and emergency management organizations worldwide.

Wireless networks have biggest constraint of limited bandwidth in comparison to wired networks but in spite of this constraint wireless networks are becoming popular day by day on account of their flexibility, mobility as well as inexpensive physical medium (air). This paper aims to simulate wireless local area network. The performance of the network is evaluated using optimized network engineering tool, OPNET 14.5 modeler,over four major physical layer technologies Infra-Red , Direct Sequence Spread Spectrum DSSS, Frequency Hopping Spread Spectrum FHSS and Orthogonal Frequency Division Multiplexing OFDM at multiple transmissionrates,1Mbps,2Mbps,5.5Mbps,6Mbps, 9Mbps,11Mbps, 36Mbps,48Mbps, 54Mbps. DSSS can use 1,2,5.5,11 Mbps rates. FHSS and IR are able to operate at 1or 2 Mbps rates, while OFDM is capable to operate at 6, 9,11,36,48 or 54 Mbps rate.A trade-off exists between the selected data rate and the physical technology. It is founded that at some transmission rate, the OFDM technology delay is better than in DSSS. FHSS delay is less than DSSS delay. IR delay is better than FHSS and DSSS delay. In addition, for one physical layer technology the delay can be reduced by increasing the transmission rate of the channel.

In mobile multiple-access communications, not only the location of active users, but also their number varies wi th time. In typical analyses, multiuser detection theory is de veloped under the assumption that the number of active users is const ant and known at the receiver, and coincides with the maximum number of users entitled to access the system. This assumpti on is often overly pessimistic, since many users might be inact ive at any given time, and detection under the assumption of a numbe r of users larger than the real one may impair performance. This paper undertakes a different, more general approach to the problem of identifying active users and estimating their parameters and data in a dynamic environment where users are continuously entering and leaving the system. Using a mathematical tool known as Random Set Theory, we derive Bayesian-filter equations which describe the evolution wit h time of the a posteriori probability density of the unknown user parameters, and u...

A linear receiver for direct-sequence spreadspectrum multiple-access communication systems under the aperiodic random sequence model is considered. The receiver consists of the conventional matched filter followed by a tapped delay line with the provision of incorporating the use of antenna arrays. It has the ability of suppressing multipleaccess interference (MAI) and narrowband interference in some weighted proportions, as well as combining multipath components without explicit estimation of any channel conditions. Under some specific simplified channel models, the receiver reduces to the minimum variance distortionless response beamformer, the RAKE receiver, a notch filter, or an MAI suppressor. The interference rejection capability is made possible through a suitable choice of weights in the tapped delay line. The optimal weights can be obtained by straightforward but computationally complex eigenanalysis. In order to reduce the computational complexity, a simple blind adaptive algorithm is also developed.

The problem of non-stationary interference suppression in direct sequence spread-spectrum (DS-SS) systems is considered. The phase of interference is approximated by a polynomial within the considered interval. According to the local polynomial Fourier transform (LPFT) principle, the received signal is dechirped by using the obtained phase approximation and the interference is, in turn, suppressed by excising the corrupted low-pass frequency band. For the estimation of polynomial coefficients, we use the product high-order ambiguity function (PHAF), known for its capability to successfully resolve components of a multicomponent polynomial-phase signal (PPS). The proposed method can suppress interferences with both polynomial and non-polynomial phase. In addition, it can suppress both monocomponent and multicomponent interferences. The simulations show that the proposed method outperforms timefrequency (TF) methods, that successfully deal with multicomponent interferences, in terms of the error probability and computational complexity.

This paper presents the novel concept of employing the noise insensitive spread-spectrum technique in well logging. The proposed design of a spread-spectrum device improves the performance of well logging tools, particularly within highly noisy environments. The heart of the device is a shift register which generates a pseudorandom binary code sequence. A coder is connected to the transmitter and codes the probing signal by utilizing the pseudorandom sequence. A decoder is connected to the receiver and correlates the return signal to the same sequence, which is used as a sliding reference. Shifts as small as a fraction of a bit are unambiguously resolvable, and distance resolution of the order of micrometers is achievable. Spread-spectrum well logging tools can operate even with coded signal-to-noise ratio below zero-dB. The spreadspectrum device can be interfaced with any available wave transmitting logging tool. However, tools employing acoustic waves are favorable because the acoustic wave propagation velocity is low and allows the use of inexpensive electronics. The problems associated with high temperatures which are commonly encountered in geothermal reservoirs are bypassed, since the spreadspectrum device can be located either inside the well logging tool or together with the supporting electronics on the surface.

In this paper, an all-digital differentially encoded quaternary phase shift keying (DEQPSK) direct sequence spreadspectrum (DSSS) transceiver is proposed. It consists of &yo parts: a baseband/IF spread-spectrum transmitter and a coherent intermediate frequency (IF) receiver. The center frequency of this IF receiver is llMHz and the sampling rate is 44 Msampleslsecond. Modulatioddemodulation, carrier recovery, PN code acquisition, and differential coding are all provided within a single chip. Functional optimization and architecture design have been done before layout implementation. Furthermore, we added testing circuits in this chip and thus each fimctional block is easily tested. The chip was fabricated through TSMC 0 . 8 ~ n-well CMOS SPDM technology. The maximum operational clock rate is measured at over 90MHz (5V, over 4Mbps), and the minimum supply voltage for 2Mbps (44MHz) rated speed is 2.6V.

In this paper, we consider an adaptive single dwell serial search system of pseudo-noise (PN) sequence s for direct sequences spread-spectrum (DS-SS) systems in no fading additive white Gaussian noise channels. Since the received signal levels in mobile communications are unknown and location varying, the acquisition schemes for pseudo-n oise (PN) sequences with fixed thresholds may cause too many false alarms. Therefore, adaptively varying thresh old schemes are proposed through the use of a constant false alarm rate (CFAR) algorithm. From the simulation results, w e observe that the DS/CDMA systems with CFAR processor outperforms the conventional scheme with fixed threshold.

This paper presents a case study describing the impact of charging process of plug in hybrid vehicles (PHEV) and all electrical vehicles (EV) on the supply grid. The paper shows the distortion produced in the grid by the simultaneous charge of a large fleet of vehicles and the corrective actions taken to guarantee the Electromagnetic Compatibility with other loads in the same grid. The goal of the investigation was to establish a design guide for parking facilities

In this paper, we experimentally evaluate and compare the robustness against interference of the OQPSK-DSSS (Offset Quadrature Phase Shift Keying-Direct Sequence Spread Spectrum) and the SUN-OFDM (Smart Utility Network-Orthogonal Frequency Division Multiplexing) physical layers, as defined in the IEEE 802.15.4-2015 standard. The objective of this study is to provide a comprehensive analysis of the impact that different levels of interference produce on these modulations, in terms of the resulting PDR (Packet Delivery Ratio) and depending on the length of the packet being transmitted. The results show that the SUN-OFDM physical layer provides significant benefits compared to the ubiquitous OQPSK-DSSS in terms of interference robustness, regardless of the interference type and the packet length. Overall, this demonstrates the suitability of choosing the SUN-OFDM physical layer when deploying low-power wireless networks in industrial scenarios, especially taking into consideration the ...

This paper addresses the security of the radio link in body area sensor networks (BASNs). Given that the well being of a person or its privacy can be compromised, security in a BASN is of utmost importance. In this work, we take a joint encryption/multiple access approach. We use a direct-sequence spread spectrum (DSSS) multiple access technique to share a radio channel between multiple sensor nodes. Unlike standard DSSS techniques, in this work, the pseudo-noise (PN) code employed to spread the transmitted signal is changed on a bit-by-bit basis. This new PN code is generated by a non-linear feedback register. The register is initialized with a secret key. Not two radio links may use the same key at any given moment. The nodes begin communication with each other by employing a publicly known PN code assignment. They exchange keys using the public PN codes and then switch into the non-linear, non-repeating PN code generation. The proposed method has the advantage of simultaneously securing the radio link and providing a means for different sensors to share the same radio channel. This joint approach results in circuit complexity and power savings.

A short overview is given on wireless high speed data links for local-area-ad-hoc-networks in mobile applications and a multifunctional CDMA-Direct-Sequence Spread-Spectrum communicating platform is investigated which may be used for inter vehicle communication as well as for object detection and ranging in the environment of cars.

In our study of this system directly spread spectrum systems, this system uses many code to spread data bits of communication.There are different types of code sequences available with good correlation properties,And they often use Pesudo sequence to spread as it is less efficient in protecting information from the breaches that attack the communications systems from penetration. But we will use Gold sequence it as it is better and more complex than the rest of the code sequence ( Pn Sequence , Barker Code, Hadamard Code , And others) in terms of the security aspect of the information, as well as it is difficult to detect the information sent in addition to that it is used in Code-division multiple access (CDMA). In our articles we design and implement difficult code in the protection of information in the communication system. Where we implemented this system using MATLAB to send as well as to send a binary data and  color photo (RGB).To make sure our system is working properly and...

Adaptive methods for performing multi-user demodulation in a Direct-Sequence Spread-Spectrum Multiple-Access (DS/SSMA) communication environment are investigated. In this scenario, the noise is characterized as being the sum of the interfering users' signals and additive Gaussian noise. The optimal receiver for DS/SSMA systems has a complexity that is exponential in the number of users. This prohibitive complexity has spawned the area of research on sub-optimal receivers with moderate complexity. Adaptive algorithms for detection allow for reception when the communication environment is either unknown or changing. Motivated by previous work with Radial Basis Functions (RBF's) for performing equalization, RBF networks that operate with knowledge of only a subset of the system parameters are studied. Although this form of detection has been previously studied (Group Detection) when the system parameters are known, in this work, neural network techniques are employed to adaptively determine unknown system parameters. This approach is further bolstered by the fact that the optimal detector in the synchronous case can be implemented by a RBF network when all of the system parameters are known. The RBF network's performance (with estimated parameters) is compared with the optimal synchronous detector, the decorrelating detector and the single layer perceptron detector. Clustering techniques and adaptive Least Mean Squares methods are investigated to determine the unknown system parameters. This work shows that the adaptive Radial Basis Function network attains near optimal performance and is robust in realistic communication environments.

Perkembangan teknologi informasi yang pesat menuntut sistem komunikasi nirkabel yang andal, efisien, dan tahan terhadap gangguan. Salah satu pendekatan yang banyak digunakan untuk menjawab tantangan ini adalah Direct Sequence Spread Spectrum (DSSS) yang dikombinasikan dengan modulasi Binary Phase Shift Keying (BPSK) koheren. Penelitian ini bertujuan untuk merancang dan menganalisis performa sistem komunikasi digital berbasis DSSS-BPSK pada kanal Additive White Gaussian Noise (AWGN). Analisis dilakukan melalui simulasi yang mengevaluasi hubungan antara nilai Signal-to-Noise Ratio (SNR) dan Bit Error Rate (BER), serta mengamati pengaruh panjang kode pseudo-random terhadap ketahanan sistem. Hasil simulasi menunjukkan bahwa sistem DSSS-BPSK menunjukkan ketahanan yang baik terhadap derau, dengan nilai BER yang menurun signifikan seiring meningkatnya SNR. Selain itu, semakin panjang kode pseudo-random yang digunakan, semakin baik performa sistem dalam mengatasi gangguan kanal. Penelitian ini mendemonstrasikan efektivitas teknik penyebaran spektrum dalam meningkatkan reliabilitas komunikasi digital, khususnya pada lingkungan dengan kondisi kanal yang tidak ideal.

This paper concentrates on building a multiantenna FPGA based Channel Sounder with single transmitter and multiple receivers to realize wireless propagation characteristics of an indoor environment. A DSSS signal (spread with a real maximum length PN sequence) is transmitted, which is correlated with the same PN sequence at each receiver to obtain the power delay profile . Multiple power delay profiles are averaged and the result is then sent to host. To utilize high bandwidth, the computationally expensive tasks related to generation and parallel correlation of PN sequences are moved to the FPGA present in each USRP (Universal Software Radio Peripheral). Channel sounder blocks were built using Vivado HLS and integrated with RFNoC (RF Network on Chip) framework, which were then used on USRP X310 devices.