scholarly journals PERFORMANCE ANALYSIS OF DS-CDMA SYSTEM FOR UNDERWATER ACOUSTIC COMMUNICATIONS

2021 ◽  
Vol 5 (9) ◽  
Author(s):  
Haoxin Kang
Keyword(s):  
Spread Spectrum ◽  
Channel Model ◽  
Linear Time ◽  
Signal To Noise Ratio ◽  
Rake Receiver ◽  
Direct Sequence Spread Spectrum ◽  
Error Rates ◽  
Underwater Acoustic Communications ◽  
Linear Time Invariant ◽  
Scatter Plots

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.

Adaptive Interference Suppression Based on Lv Distribution for DSSS Communications

2014 ◽  
Vol 24 (01) ◽  
pp. 1550012 ◽  
Author(s):  
Shan Luo ◽  
Xiumei Li ◽  
Shenghong Li ◽  
Guoan Bi
Keyword(s):  
Spread Spectrum ◽  
Interference Cancellation ◽  
Communication Systems ◽  
Signal To Noise Ratio ◽  
Interference Suppression ◽  
Direct Sequence Spread Spectrum ◽  
Error Rates ◽  
Phase Cancellation ◽  
Adaptive Interference Suppression ◽  
High Order Statistics

It is generally difficult to effectively eliminate intentional multiple component interference in any communication systems mainly because of the difficulties in accurately estimating the parameters of interference particularly in low signal-to-noise ratio (SNR) environments. This paper proposes effective methods of adaptive interference suppression based on Lv distribution (AISL) for direct sequence spread spectrum (DSSS) communications. Since the recently reported Lv distribution (LVD) provides better concentration of signal energy in the domain of frequency-chirp rate than other reported methods, it achieves performance improvement on estimating the parameters containing multiple linear frequency modulated (LFM) signals. With the desirable properties of the LVD, the proposed interference suppression methods are able to excise interference of multiple components. The proposed methods firstly examine if the received signal is interfered by using a high-order statistics, known as skewness, to measure the distribution concentration of the received signal in the LVD domain. Then the interference excision process is employed only when the interference is present. Two methods, i.e., AISL-I based on the concept of interference cancellation and AISL-II based on phase cancellation and filtering, are investigated. The merits of these methods are analyzed and compared in terms of bit error rates (BERs). Results of Monte Carlo experiments are also presented to show the effectiveness of suppressing interference by the proposed methods.

scholarly journals SHAPING OPERATOR TECHNIQUE FOR MODELLING CYCLOSTATIONARY RANDOM PROCESSES

T-Comm ◽  
2021 ◽  
Vol 15 (8) ◽  
pp. 4-12
Author(s):  
Timofey Ya. Shevgunov ◽  
Keyword(s):  
Spread Spectrum ◽  
Linear Time ◽  
Pulse Amplitude ◽  
Delta Function ◽  
Direct Sequence Spread Spectrum ◽  
Analytical Relation ◽  
Operator Technique ◽  
Spectral Correlation ◽  
Dirac Delta ◽  
Linear Time Invariant

The paper proposes the shaping operator technique for modelling cyclostationary random process (CSRP) which belong to the class of second-order processes being described by the parametric pulse train model. Generating CSRP is expressed as the propagation result of the specially chosen elementary CSRP through the linear time-invariant system with a known impulse response. The paper describes the approach to forming the elementary CSRP based on the train made of Dirac delta-function uniformly following in time domain with constant step and defining the desired structural periodicity of the process being modelled. The analytical expressions for the main characteristics used for describing cyclostationary properties of the elementary process, including two-dimensional, cyclic and spectral correlation functions, were obtained. In addition to the case of the elementary CSRP with correlated weighting coefficients of delta-functions, the case of statistically independent coefficients was considered. It was shown that utilization of the spectral correlation function (SCF) for describing the cyclic property reveals the explicit analytical relation between characteristics of the elementary and modelled CSRPs provided the filter frequency response is known. The paper presents the comparative example which describes the modelling of two CSRPs: one of them was chosen as the train of rectangle pulses which is pulse amplitude modulated by stationary random time series, while the other is considered as a signal formed by the method of direct sequence spread spectrum. The chosen short-length Barker sequence as the code allowed performing visual comparison between absolute value of SCF components taken at the cyclic frequencies multiple of the chip frequency and cyclic frequencies multiple of the symbol frequency. The future development of the methods proposed in the paper opens the road to improving the performance of modern radar and telecommunication systems by means of utilizing cyclic frequencies which are non-random parameters describing the structural properties of signals under processing.

Microcellular direct-sequence spread-spectrum radio system using N-path RAKE receiver

1990 ◽  
Vol 8 (5) ◽  
pp. 772-780 ◽  
Author(s):  
U. Grob ◽  
A.L. Welti ◽  
E. Zollinger ◽  
R. Kung ◽  
H. Kaufmann
Keyword(s):  
Spread Spectrum ◽  
Rake Receiver ◽  
Direct Sequence Spread Spectrum ◽  
Direct Sequence ◽  
Radio System ◽  
Spectrum Radio

scholarly journals A RAKE RECEIVER DESIGN FOR ULTRA WIDE BAND APPLICATION

2014 ◽  
pp. 257-262
Author(s):  
SURAJIT DEKA ◽  
MANASH PRATIM SARMA ◽  
Kandarpa Kumar Sarma
Keyword(s):  
Spread Spectrum ◽  
Interference Mitigation ◽  
Signal To Noise Ratio ◽  
Rake Receiver ◽  
Wide Band ◽  
Multipath Fading ◽  
Ultra Wide Band ◽  
Receiver Design ◽  
Sequence Generator ◽  
Spread Spectrum Modulation

In this paper, we describe the design and implementation of a rake receiver for use with ultra wide band (UWB) systems. The rake receiver uses spread spectrum modulation (SSM) aided by kasami sequence generator. The combination is found to be effective in dealing with multipath fading and signal to noise ratio. The design is initially simulated using MATLAB 7.10 and is implemented using a HDL coder. The design is also implemented in a FPGA kit and is found to be effective in interference mitigation as part of a CDMA framework.

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