Performance analysis of instantaneous frequency-based interference excision techniques in spread spectrum communications

The direct sequence (DS) spread spectrum communication technique is widely regarded as one of the most effective methods of mitigating the effects of a repeating jammer in military communications systems. The proposed system coupled DS with multiple frequency shift keying (DS/MFSK). It is comprised of a transmitter and a receiver. Non-coherent demodulation is examined, as are the spreading sequences in question. The effect of AWGN and Rayleigh fading channels on the proposed approach's bit error rate (BER) is examined. The investigation demonstrates that even with an 8 dB signal-to-noise ratio, superior outcomes can be achieved; this study's suggested endeavor is to create a novel transceiver system built on the DS/MFSK modular architecture. MFSK modulation prevents multiple-access interference, while DS is typically employed to boost system efficiency across erratic fading. Test results show that reliability on the AWGN channel decreases a little while reliability is greatly enhanced by Rayleigh fading. Moreover, notable improvements in bandwidth efficiency are achieved.

Clock and carrier recovery are very critical in high speed digital wireless communication for achieving high data rate with low packet error rate. In this paper, we propose a linear estimator for both clock and carrier recovery in a direct sequence spread spectrum (DSSS) communication system and show that this is also the maximum likelihood (ML) estimator. We present simulation results to illustrate the convergence of the estimator under different multipath channel conditions.

A novel method of multipath diversity signal combination is proposed for mobile direct sequence spread spectrum (DS-SS) communications. Multiple transmissions are made for each spread signal. Each transmission is independently delayed and amplified in the complex domain according to the delay profile and the estimated path strength of the channel. This is done to facilitate reception of a signal at the mobile unit which is already a RAKE combination of the multipath signals. This method is called a pre-RAKE combination system because the RAKE combination function is performed pre-transmission. Using this method the size and complexity of the mobile unit can be kept to a minimum. The pre-RAKE method retains the advantages of diversity reception in a multi-path fading environment. An examination of the SNR for the traditional RAKE and the pre-RAKE systems and computer simulations show that the performance of the pre-RAKE system is equivalent to that of the RAKE system. >

In this letter, the weighted fractional Fourier transform (WFRFT) is performed on the chaotic sequence to enhance the security of the chaotic direct sequence spread spectrum (CD3S) communication, and a WFRFT-CD3S system that spreads the information bits through the WFRFT-chaotic sequence is proposed. In the proposed system, the transmitter scrambles the phase space trajectory of the chaotic sequence through WFRFT and make the distribution of the transmitted signal be Gaussian-like. The receiver synchronizes the WFRFT-chaotic sequence through bidirectional correlation search and demodulates the information through the synchronized local WFRFT-chaotic sequence. Simulations are implemented to evaluate the security performance, synchronization performance, and demodulation performance of the proposed system.

The time-frequency (TF) filter design of non-stationary signals especially chirp signals are studied in the fractional domain. The design of TF/ linear time variant (LTV) filter is implemented as a non-overlapping short time fractional Fourier transform (STFRFT). The first step of our method involves detecting the presence of a multi component linear FM interference and correctly estimating its orientation in the time-frequency plane using cross spectral estimation of signal parameter via rotational invariant technique. This paper introduces a novel algorithm to excise single and multicomponent chirp-like interferences in direct sequence spread spectrum (DSSS) communication. The proposed method excises the interference with high interference power condition, and technique could be easily extended to any kind of chirp interference with little modification

Remote labs have become popular learning aids due to their versatility and considerable ease of utilisation as compared to their physical counterparts. At Makerere University, the remote labs are based on the standard Massachusetts Institute of Technology (MIT) iLabs Shared Architecture (ISA) - a scalable and generic platform. Presented in this paper is such a lab, addressing the key practical aspects of Direct Sequence Spread Spectrum (DSSS) communication. The lab is built on the National Instruments Educational Laboratory Virtual Instrumentation Suite (NI ELVIS) with the Emona Digital and Analog Telecommunications Experimenter (DATEx) add-on board. It also incorporates switching hardware. The lab facilitates real-time control of the equipment, with users able to set, manipulate and observe signal parameters in both the frequency and the time domains. Simulation and data Acquisition modes of the experiment are supported to provide a richer learning experience.

Traditional time/frequency domain filter-based methods would fail due to the serious overlapping of the communication signal and jamming in time/frequency domain. In order to solve this problem, an anti-jamming algorithm based on single channel source separation by exploiting cyclostationary difference is proposed for direct sequence spread spectrum (DSSS) communication. Firstly, the cyclostationary difference among source signals is used to establish the single channel source separation model based on partial priori information of the DSSS signal. Secondly, cost function of the algorithm is constructed by the training sequences and the minimum mean square error criterion; after that, the optimal separation matrix of the pilot mixed signal can be calculated based on this cost function. Thirdly, the purpose of anti-jamming for DSSS communication can be achieved by separating the communication signal from the service mixed signal based on the optimal separation matrix calculated before. Simulation results show that, compared with the unseparated signal of high bit error rate (BER) close to 0.5, the proposed antijamming algorithm is more effective in anti-jamming with the BER as low as 10–3, which is not only applicable to narrowband jamming such as the single-tone/multi-tone jamming, but also applicable to broadband jamming such as the sweep-spot jamming.

Under the software environment of MATLAB/Simulink, the communication system of direct sequence spread spectrum (DSSS) is dynamically modeled and simulated over a new practical Rayleigh channel, and the relationship curves of the bit error rate (BER) with the signal-to-noise ratio (SNR) of DSSS communication systems are presented. It is analyzed that DSSS system can effectively overcome multipath fading in multipath Rayleigh Fading Channel (RFC). In addition, the anti-multipath fading performance improved by the way of increasing pseudo noise (PN) code length is better than that by the way of increasing the spread spectrum gain in the condition of strong multipath fading.

To address the inability to quantitatively analyze the performance of the direct sequence spread spectrum (DSSS) communication system in the presence of short-period pseudo-noise (PN) sequences, this study derives the interference components resulting from correlation processing of single-frequency interference. Given the short period of the spread spectrum sequence used in underwater acoustic systems, a theoretical expression is proposed for analyzing the anti-single-frequency interference performance of DSSS communication systems in underwater acoustics. This expression combines the interference power output by the system to enable quantitative analysis. Simulations are conducted to validate the accuracy of the theoretical expression. The results reveal that the interference sequence generated by correlation processing assumes either a direct current (DC) or sinusoidal distribution. The bit error rate (BER) of the system is influenced by signal-to-interference ratio (SIR), interference frequency offset, phase deviation, and the structure of the spreading code itself. The BER exhibits regular variation with changes in the interference phase. In all working conditions where the interference frequency offset is an integer multiple of the bit bandwidth, single-frequency interference with a frequency offset equivalent to the bit bandwidth has the greatest impact on the system. The concise theoretical expression presented in this study has significant practical value as it allows for quick prediction of variation in the anti-single-frequency interference performance of underwater acoustic DSSS communication systems using short-period PN sequences.

The suppression of narrow-band interference has long been a concern in Direct-Sequence Spread Spectrum (DS-SS) Communication Systems. Recently, transform domain processing (TDP) approaches have been used to suppress intentional interference. This paper extends previous work done in the area of TDP utilizing non-linear rank order filters, namely conditional median filters (CMFs). The paper confronts problems incurred in Rayleigh distributed fading channels. A solution is suggested by introducing a normalized adaptive median filter. This adaptive approach considers each received bit independently and uses a normalization metric to compensate for fading. The paper also presents bit error rates (BER) for a DS-SS receiver employing the proposed approach. Using Monte-Carlo simulations the BER of the fading channel was determined for various jammer and fading scenarios, and results are presented.

A generalized approach for interference suppression in PN spread spectrum communications using open-loop adaptive excision filtering is introduced. The excision filter coefficients under this technique depend on the jammer power and its instantaneous frequency (IF) information, and both values can be gained in the time-frequency domain. The dependency of the excision filter characteristics on the interference power, which was absent in past contributions in this area, is of significant importance as it allows optimum tradeoff between interference removal and the amount of self-noise generated from the induced correlation across the PN chip sequence, due to filtering. This tradeoff is bounded by the two extreme cases of no self-noise, which implies preprocessing disabled, and full interference excision, which the case previously considered. In this paper, we derive the FIR excision filters that maximize the receiver signal-to-noise ratio for narrowband interference and discuss the generalization to nonstationary jamming environment.

This study introduces the group delay and its characteristics in satellite channel, meanwhile, the model of the impact of group delay ripple on performance of direct sequence spread spectrum communication system is established and simulated for analysis. The simulation results indicate the specific impact of group delay ripple on system, as well as the impact of group delay ripple on the transmission and reception signals in the spread spectrum communication system. For transmission signals in the spread spectrum system, the group delay ripple can worsen the EVM and Eye-diagram of spread spectrum signal, cause signal distortion and the deterioration of noise tolerance. For the reception performance of the spread spectrum system, the group delay ripple has little effect on the spread spectrum acquisition using incoherent accumulation and energy judgment, but it can cause a deterioration in the error performance of the reception signal. For example, when relative group delay increases from 0.011 to 0.9, the error performance decreases by about 2 dB. When designing satellite spread spectrum communication systems, power resources are extremely precious, it is necessary to consider the impact of group delay on the communication system, and take certain measures to reduce the impact of group delay ripple to the system.

Modulation techniques in 5G wireless communication systems play a crucial role in meeting demands for higher data rates, lower latency, and improved connectivity. This involves optimizing power spectral density (PSD), enhancing data transmission reliability, and reducing bit error rates (BER) and interference. The objective of this paper is to evaluate primary modulation schemes used in 5G—Orthogonal Frequency Division Multiplexing (OFDM), Filter-Orthogonal Frequency Division Multiplexing (F-OFDM), Filter Bank Multi-Carrier (FBMC), and Universal Filtered Multi-Carrier (UFMC)—based on performance metrics such as PSD, BER, and signal-to-noise ratio (SNR) using MATLAB. OFDM demonstrates low BER at high SNR but faces degradation at lower SNRs, necessitating a higher SNR for maintaining low BER. F-OFDM improves BER in noisy environments through reduced out-of-band emissions and improved spectral efficiency. FBMC shows lower BER than OFDM, especially in multipath fading scenarios, despite its higher complexity. UFMC provides balanced performance with moderate BER across varying SNRs, offering a trade-off between simplicity and efficiency, with stable BER and enhanced spectral efficiency, and reduced latency compared to OFDM. Each modulation scheme in 5G presents specific strengths and weaknesses. OFDM is robust and widely used, while F-OFDM, FBMC, and UFMC enhance spectral efficiency, BER, and SNR management. Selecting the appropriate technique depends on network requirements, with MATLAB simulations playing a crucial role in optimizing 5G network performance.

Deployment of wireless sensor networks (WSNs) with a large number of nodes have reinstated interest in spread spectrum (SS) technologies as they allow to establish multiple access for nodes with simple hardware and limited power budget. Chaotic spreading is one of the still insufficiently explored areas which can lead to higher security and lower multiple access interference (MAI). This research is intended to bring new information about the performance of binary direct sequence spread spectrum (DSSS) and frequency hopping spread spectrum (FHSS) communication systems which employ chaos-based spreading codes and compare them against classical systems employing m-sequences. Unlike existing research, this investigation is based on the simulation of passband communication systems with up/down-conversion and respective filtering. Performance comparison in terms of bit error ratio (BER) versus signal-to-noise ratio (SNR) at the different number of users and MAI dependence on carrier frequency offset among users in case of additive white Gaussian noise (AWGN) channel are presented. Obtained results highlight several scenarios where chaotic-sequences-based binary DSSS and FHSS systems have advantages over classical solutions.

Jammer suppression in spread spectrum communication using novel independent component analysis approach