摘要 :
This paper proposes a narrowband interference (NBI) suppression algorithm for Direct Sequence-Code Division Multiple Access systems. The NBI is considered from heterogeneous networks, and predicted based on its cyclostationary cha...
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This paper proposes a narrowband interference (NBI) suppression algorithm for Direct Sequence-Code Division Multiple Access systems. The NBI is considered from heterogeneous networks, and predicted based on its cyclostationary characteristic using a nonlinear feed-forward neural network predictor which eliminates the nonlinearity of the spread spectrum (SS) signal in the NBI prediction. To further improve the suppression performance, this paper exploits the structure of the spreading code, and proposes an iterative code-aided algorithm to jointly estimate the NBI and the SS signal. Simulation results reveal that the proposed algorithm largely outperforms the conventional linear prediction filtering and linear-conjugate linear polyperiodically time-varying filtering methods in both the signal to interference plus noise ratio improvement and the bit error rates, when it operates in NBI-contaminated environments.
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摘要 :
In order to improve spectral efficiency, CDMA overlay, which means co-existence of wideband and narrowband signals in the same frequency band, has been considered. However, signals from existing narrowband systems are not necessar...
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In order to improve spectral efficiency, CDMA overlay, which means co-existence of wideband and narrowband signals in the same frequency band, has been considered. However, signals from existing narrowband systems are not necessarily transmitted with low power level enough not to give damage to DS-CDMA signals. Therefore, an efficient rejection technique for narrowband interferers is required for successful CDMA overlay. Furthermore, it is necessary to cope with sudden changes of interference power levels associated with their appearance/disappearance. In this paper, we propose a chancellor to reject such high power narrowband interference for the DS-CDMA system and show the rejection performance obtained from the computer simulation.
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摘要 :
In order to improve spectral efficiency, CDMA overlay, which means co-existence of wideband and narrowband signals in the same frequency band, has been considered. However, signals from existing narrowband systems are not necessar...
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In order to improve spectral efficiency, CDMA overlay, which means co-existence of wideband and narrowband signals in the same frequency band, has been considered. However, signals from existing narrowband systems are not necessarily transmitted with low power level enough not to give damage to DS-CDMA signals. Therefore, an efficient rejection technique for narrowband interferers is required for successful CDMA overlay. Furthermore, it is necessary to cope with sudden changes of interference power levels associated with their appearance/disappearance. In this paper, we propose a chancellor to reject such high power narrowband interference for the DS-CDMA system and show the rejection performance obtained from the computer simulation.
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摘要 :
Due to congestion in wireless frequency use, it is difficult to assign an independent frequency bandwidth to broadband wireless communication systems based on the DS-CDMA (Direct Sequence Code Division Multiple Access) system. The...
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Due to congestion in wireless frequency use, it is difficult to assign an independent frequency bandwidth to broadband wireless communication systems based on the DS-CDMA (Direct Sequence Code Division Multiple Access) system. Therefore, operation of the DS-CDMA system on the existing narrowband wireless system is contemplated. However, the interference of the transmitted power of the existing narrowband wireless system on the DS-CDMA system has not been studied. There is a possibility that significant narrowband interference on the DS-CDMA system may occur. In this paper, a narrowband interference rejection system in DS-CDMA is proposed. By making use of prior information on the carrier frequency of the narrowband interference, a narrowband interference rejection process with little computational overhead is realized.
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We often encounter a situation where several half-duplex based narrow-band interferes give much damage to DS-CDMA signal with sudden changes in the power level. In this paper, we discuss a method to reject such narrow-band interfe...
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We often encounter a situation where several half-duplex based narrow-band interferes give much damage to DS-CDMA signal with sudden changes in the power level. In this paper, we discuss a method to reject such narrow-band interference in DS-CDMA system. We propose an adaptive digital filter-based narrow-band interference canceler with an interference detection method. We show the rejection and detection performance obtained from computer simulation.
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摘要 :
We often encounter a situation where several half-duplex based narrow-band interferes give much damage to DS-CDMA signal with sudden changes in the power level. In this paper, we discuss a method to reject such narrow-band interfe...
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We often encounter a situation where several half-duplex based narrow-band interferes give much damage to DS-CDMA signal with sudden changes in the power level. In this paper, we discuss a method to reject such narrow-band interference in DS-CDMA system. We propose an adaptive digital filter-based narrow-band interference canceler with an interference detection method. We show the rejection and detection performance obtained from computer simulation.
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摘要 :
The multiple access causes an interference prob- lem in the direct-sequence code-division multiple access systems. An efficient adaptive algorithm should be used to suppress this interference for the improvement of system performa...
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The multiple access causes an interference prob- lem in the direct-sequence code-division multiple access systems. An efficient adaptive algorithm should be used to suppress this interference for the improvement of system performance. In this paper, the new blind adaptive method is suggested using the constant modulus algorithm for the purpose of interference sup- pression.
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This paper deals with narrowband interference (NBI) and multiple access interference (MAI) suppression based on subspace-based approaches for direct-sequence code-division multiple-access (DS-CDMA) systems. First, the signal subsp...
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This paper deals with narrowband interference (NBI) and multiple access interference (MAI) suppression based on subspace-based approaches for direct-sequence code-division multiple-access (DS-CDMA) systems. First, the signal subspace-based and the interference subspace-based techniques are developed to estimate the noisy DS-CDMA signal and the interference signal, respectively. In conjunction with a modified multiple constrained minimum variance multiuser detector, we develop two efficient schemes to deal with the NBI and MAI that do not need any prior knowledge about the characteristics of the interference and specific training sequence. Next, an adaptive implementation based on a signal subspace tracking algorithm and a recursive least mean square algorithm is also developed. Several computer simulation examples in terms of bit error rate are provided for illustrating the effectiveness of the proposed schemes.
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A convolutionally coded M-ary orthogonal direct sequence code division multiple access (DS-CDMA) system in time-varying frequency-selective Rayleigh fading channels is considered in this work. We propose several novel soft demodul...
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A convolutionally coded M-ary orthogonal direct sequence code division multiple access (DS-CDMA) system in time-varying frequency-selective Rayleigh fading channels is considered in this work. We propose several novel soft demodulation algorithms based on interference cancellation and suppression techniques that can be coupled with soft decoding to improve the system performance in an iterative manner. The performance of the proposed demodulation algorithms is evaluated numerically and proved to achieve substantial bit error rate (BER) performance gain compared with the conventional detection schemes.
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摘要 :
The performance of a multitone Code Division Multiple Access (CDMA) system is investigated in this paper by considering the effect of multipath fading, diversity and narrowband interference. The performance is evaluated in terms o...
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The performance of a multitone Code Division Multiple Access (CDMA) system is investigated in this paper by considering the effect of multipath fading, diversity and narrowband interference. The performance is evaluated in terms of the average bit error rate when both multiple access and partial band interference are present. Results are obtained by deriving the statistics of the receiver output parameters and then tested by numerical evaluation. The bit error rate performance is analyzed as a function of bit rate, bandwidth, delay range and different diversity techniques, while considering issues relevant to system implementation. Comparisons were made between conventional single-tone CDMA systems and multitone CDMA systems. The effectiveness of multitone CDMA in suppressing interference compared to conventional CDMA system is analyzed. Results reveal considerable performance improvement of multitone CDMA system over conventional CDMA system.
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