Abstract
The exponential chip weighting waveforms have been designed with the purpose of multiple access interferences (MAI) rejection based on the concept that the optimum despreading sequence in reference emphasizes the transitions in the received spreading signal of interest. The despreading sequence weighted by exponential chip waveforms was determined by only one parameter. The objective of this study, was to introduce neural networks (NN) to facilitate the computing of the bit error rate (BER) performance of a direct sequence code division multiple access (DS/CDMA) system over a Rayleigh multipath fading with power control error, for both coherent and noncoherent receivers, by producing the despreading sequences weighted (WDS) by exponential chip weighting waveforms. Numerical results show that the parameter values of the exponential chip weighting waveforms produced by the proposed network are nearly optimal and satisfactory in viewpoint of the achieved bit error rate (BER) performance.
Highlights
The major limitation in the bit error rate (BER) and system performance and capacity, is due to multipath fading, (MAI) and imperfect power control
In a previous work[4], the BER performance of a direct sequence code division multiple access (DS/CDMA) system was analyzed with power control error over a multipath Rayleigh fading channel using both coherent and noncoherent receptions, the receivers under consideration employ the despreading sequences weighted (WDS) by adjustable exponential chip waveforms optimized for MAI rejection
A new approach based on neural networks (NN) has been successfully presented in this study to help the determination process of the exponentially weighted despreading sequences for a DS/CDMA system
Summary
The major limitation in the bit error rate (BER) and system performance and capacity, is due to multipath fading, (MAI) and imperfect power control. With the objective of MAI rejection, most of works had been made on CDMA performance in presence of multipath fading and are based on the fact that power control is perfect[1,2,3], which is not really possible in practice. In a previous work[4], the BER performance of a DS/CDMA system was analyzed with power control error over a multipath Rayleigh fading channel using both coherent and noncoherent receptions, the receivers under consideration employ the despreading sequences weighted (WDS) by adjustable exponential chip waveforms optimized for MAI rejection. The chip weighting waveforms employed are determined by only one parameter that leads to easy tuning of the waveforms in practice to achieve the best performance. A number of computational efforts are needed to define the parameters of each spreading sequence
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