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This paper proposes a feed-forward neural network predictor to adaptively estimate and suppress the narrowband interference (NBI) in the Direct Sequence-Code Division Multiple Access (DS-CDMA) signal. The iterative code-aided estimation is used to further improve the system performance. Simulation results reveal that the proposed algorithm outperforms conventional linear prediction filtering and recurrent...
Direct sequence spread spectrum (DSSS) signals are now widely used for communications, as well as for multiple access. DSSS transmitters use a spreading sequence to modulate the baseband signal before transmission. A receiver which does not know the spreading sequence cannot demodulate the signal. In the paper, we propose a method which can estimate the spreading sequence in a non-cooperative context...
To aim at the problem of blind estimation of low-SNR DS/SS signals spreading sequence, an approach is proposed to estimate the spreading sequence from DS/SS signals in this paper. The method is based on neural network by a novel information criterion. The theoretic analysis and computer simulation results show that this algorithm has much less computation and storage than EVD, and its performance...
Knowledge of the direction of arrival (DOA) of a signal is useful both in civil applications such as mobile communications and also in military related applications as well. Even though asynchronous wise both applications are same, they are not when the number of sources are considered. This paper considers the problem of estimating the DOA of users in an asynchronous DS-CDMA system where the technique...
A combination method is presented to estimate the unknown pseudo-noise (PN) spreading sequence for direct sequence spreading spectrum (DS-SS) signals in frequency selective fading channel. Performance of traditional blind estimator based on eigenanalysis techniques shows significant performance degradation when directly employed in multipath fading environment. Borrowing blind channel estimation and...
Aiming at the problems of the detection of long pseudo-random code DSSS (direct sequence spread spectral) Signals and the estimation of the pseudo-random code period and the chip width, the paper proposes a method based on the processing of delay-multiply with the signals. The method does processing of delay-multiply on the received signals at first, then calculates the autocorrelation and gets correlation...
A new algorithm based on pilots for the joint carrier frequency offset (CFO) and channel estimation of the uplink of MC-DS-CDMA systems is presented. As with the specially designed pilots, the inter-user interference (IUI) among user specific sub-matrix of received signal matrix in time domain does not exist any more, CFO and channel estimations are easily obtained for all users with single user CFO...
One of the most important problems to be solved in direct sequence spread spectrum systems is to achieve a robust acquisition of the pseudo noise sequence. In multiuser time-varying environments this fact becomes even more important because acquisition and tracking performance can heavily degrade communication reliability. In this paper a new neural network estimator is presented, and it is compared...
In this paper, we propose a new algorithm for the carrier frequency offset (CFO) estimation of the uplink of multicarrier DS-CDMA (MC-DS-CDMA) systems. Firstly, our method exploits a new pilot scheme to obtain the approximation of the interested userpsilas signal from the composite signals on the user specific subcarrier in the receiver. Then the fast Fourier transform (FFT) operation is applied to...
A method for estimating the hop period of frequency hopping (FH) signals based on Hilbert-Huang transform (HHT) is proposed. This method iteratively decomposes the FH signal into intrinsic mode functions (IMFs) and applies Hilbert transform to each IMF to yield Hilbert spectrum, whose maxima for each time instant are extracted to form a sequence. A simple Fourier transform based analysis of the obtained...
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