共查询到20条相似文献,搜索用时 31 毫秒
1.
Since the received signal levels in mobile communications are unknown and the location is varying, acquisition schemes for pseudonoise (PN) sequences with fixed thresholds cannot provide satisfactory performance. This fixed-threshold scheme may cause too many false alarms or result in a low detection probability for a selected threshold value. We present an adaptive acquisition scheme for PN sequences which estimate the background power level, multiply it with a threshold coefficient to keep the false alarms constant, and use it as a threshold 相似文献
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为有效解决强干扰环境下长PN 码的同步捕获问题,研究了基于自适应滤波器的PN 码同步捕获方法,给出了基于自适应滤波器权矢量范数的同步捕获判决准则,与传统的基于均方误差的判决相比,这种方法可以大幅提高判决的正确概率。在此基础上,研究了智能天线权值与PN 码同步联合捕获算法,并对其性能进行了计算机仿真验证,结果表明这种空时联合的捕获算法可以有效实现低SINR 环境下的长PN 码捕获。 相似文献
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For pt. I see IEEE Trans. Veh. Technol. A smart antenna, i.e., a blind adaptive antenna array, has attracted much attention to improve the capacity of a future code-division multiple-access wireless communications system. It has been demonstrated that there is significant improvement in data demodulation through lab simulations and field experiments by employing a smart antenna of multiple elements. However, only one element is used for the pseudonoise (PN) code acquisition process, which is a coarse PN code synchronization prior to data demodulation. This paper proposes a simple and practical PN code acquisition scheme, which employs all elements in the smart antenna. Also, this paper uses an adaptive threshold for the PN code acquisition. Simulation results demonstrate that the proposed scheme can significantly improve the PN code acquisition performance, e.g., the PN code acquisition time will be half as long by employing five elements rather than the single element at a given bit-energy-to-interference power spectral density ratio. 相似文献
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Adaptive PN code acquisition using instantaneous power-scaled detection threshold under Rayleigh fading and pulsed Gaussian noise jamming 总被引:1,自引:0,他引:1
Kwonhue Choi Kyungwhoon Cheun Taejin Jung 《Communications, IEEE Transactions on》2002,50(8):1232-1235
An adaptive serial search pseudonoise (PN) code acquisition scheme is proposed, in which the detection threshold is scaled by the instantaneous received power measured prior to PN code correlation. We observe that the proposed scheme achieves significantly improved mean acquisition times compared to the conventional nonadaptive schemes under Rayleigh fading and pulsed Gaussian noise jamming. Furthermore, the proposed scheme is shown to be optimum under pulsed Gaussian noise jamming in the sense that it forces the worst case jamming fraction to unity. 相似文献
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Jung Hoon Lee Iickho Song So Ryoung Park Jumi Lee 《Vehicular Technology, IEEE Transactions on》2004,53(1):49-60
In this paper, a fast acquisition scheme of pseudonoise (PN) sequences for direct-sequence spread-spectrum systems is proposed. The scheme exploits a new decision logic not only to estimate chip values, but also to check the reliability of the chip estimates. As a result, the internal state of a PN sequence generator is estimated more accurately. We derive the probability of finding a correct state estimate and show that the proposed scheme can reduce the average number of chips for acquisition when compared with the conventional scheme. It is also shown that the performance improvement is more noticeable in the moderate signal-to-noise-ratio range. 相似文献
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An acquisition method of long pseudo-noise (PN) sequences in direct-sequence spread spectrum (DS/SS) systems is presented. The concurrent cross correlation of locally generated auxiliary signals with the incoming PN sequence produces binary search estimates leading to an initial approximation of the input signal's PN offset. The PN receiver then uses a closed-loop subsystem to determine the true offset of the incoming PN signal. New phase estimates are generated from successive corrections of likely errors in the binary search. The acquisition scheme's average acquisition time and its variance are analytically determined. Simulation results show that the proposed acquisition scheme is faster than the conventional serial receiver. A hybrid serial/parallel PN acquisition receiver is used for comparing the acquisition performance given similar hardware complexity. The hybrid receiver used the same number of parallel correlators as used in the proposed receiver's input phase estimator. Simulation results show that the proposed system provides an improved performance under normal operating conditions. 相似文献
7.
PN code acquisition using smart antenna for spread-spectrum wireless communications. I 总被引:1,自引:0,他引:1
The smart antenna (a blind adaptive antenna array) has brought much attention to its ability to improve the future code-division multiple-access (CDMA) wireless communications systems. However, Adachi et al. (1998), employed only one out of M elements that are in a smart antenna array during the pseudonoise (PN) code acquisition process due to the difficulty in obtaining the weight coefficients of the smart antenna and PN code acquisition jointly and adaptively. Yet, as the PN code is acquired, all M elements are used by Adachi et al. to improve the signal-to-noise ratio (SNR) at a reverse link. We propose an efficient PN code acquisition scheme where all elements are employed during PN code acquisition. Also, we show that by using all elements, the PN code acquisition time can be shortened by at least 40% for a given signal-to-noise ratio and M=5, compared to the single element case. Furthermore, the power of a random access user signal in the reverse link can be lowered at least 3 dB. The additional computational load and complexity to use the proposed PN code acquisition are insignificant. 相似文献
8.
Noncoherent SPRT-based acquisition scheme for DSSS 总被引:1,自引:0,他引:1
Jia-Chin Lin 《Electronics letters》1998,34(13):1290-1291
A noncoherent sequential PN code acquisition scheme is proposed. The out-of-phase and on-phase sequences are properly modelled to avoid significantly high error probabilities occurring with the conventional SPRT-based acquisition. In addition, data modulation and frequency offset can be effectively overcome using this technique 相似文献
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Suwon Kang Yong-Hwan Lee 《Selected Areas in Communications, IEEE Journal on》2001,19(6):1128-1137
We propose a new scheme for rapid acquisition of PN signals in direct-sequence spread spectrum (DS/SS) systems by estimating the phase of the received PN signal with the use of an auxiliary signal. The auxiliary signal can be generated by a sum of the phase shifted PN signals. The phase of the incoming PN signal is estimated using the properties of cross correlation between the PN signal and the auxiliary signal. True phase alignment is detected using a conventional serial search scheme, where the initial phase of the local PN generators is set to a value obtained by the phase estimator. The performance of the proposed acquisition scheme is analytically evaluated in terms of the mean acquisition time. Numerical results show that the proposed scheme can achieve acquisition at least two times faster than the conventional scheme in the nominal operating condition 相似文献
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Byoung-Hoon Kim Byeong Gi Lee 《Communications, IEEE Transactions on》1999,47(5):754-765
We propose a new acquisition scheme called distributed sample acquisition (DSA) which is applicable to the direct-sequence code-division multiple-access (DS/CDMA) system with a long-period pseudonoise (PN) sequence. The proposed scheme lays its foundations on an auxiliary PN sequence called the igniter sequence, which has relatively short period, and the distributed sample scrambling (DSS) technique previously developed for the asynchronous transfer mode cell transmission. In the DSA scheme, acquisition is done in three steps. First, the igniter sequence is synchronized, which normally takes a very short time due to its short period. Second, the state samples of the long-period PN sequence generator in the transmitter, which are conveyed to the receiver over the igniter sequence stream, are determined out of the synchronized igniter sequence. Third, the long-period PN sequence is synchronized by applying the state samples to the DSS receiver. Since the operation of each step takes a very short time, the overall acquisition is done very quickly. We analyze the acquisition time performance of the proposed scheme by taking the transform domain approach, confirming that the resulting mean acquisition time is dramatically reduced. If compared with the existing serial-search scheme, the DSA scheme can perform acquisition about 100 times faster when the period of the PN sequence is 215-1. None the less, the additional circuit complexity for its implementation is very small 相似文献
15.
We introduce a correlation-aided distributed sample acquisition (CDSA)-based intercell synchronous direct-sequence code-division multiple-access (DS/CDMA) system for enhancing the robustness of the previously proposed distributed sample acquisition (DSA)-based system. The CDSA system incorporates the state symbol correlation process in the existing DSA process to maintain the fast acquisition performance even under very poor channel environment. For its realization, each CDSA-based mobile station stores in its memory a period of the possible state symbol sequences, which are determined by the long-period scrambling PN sequences used in the system and the sampling time parameters for the state samples. In the first stage of the synchronization procedure, the mobile station (MS) attempts to acquire the psuedo noise (PN) sequence by taking the comparison-correction based synchronization approach of the original DSA scheme. However, if it cannot acquire the synchronization until it collects a predetermined number of state symbols (e.g., a period of the state symbol sequence), then the MS determines the PN sequence timing by correlating the received symbol sequence with each shift of the prestored state symbol sequences. Performance analysis and simulation results reveal strong robustness of the CDSA-based system in low-signal-to-noise ratio, fading, and large frequency-offset channels. 相似文献
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对PN序列的捕获问题,介绍了串行捕获和并行捕获两种方案,在此基础上介绍了一种改进的门限自适应的快速同步技术,适用于短波高速数据传输。 相似文献
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Sequential acquisition of PN sequences for DS/SS communications:design and performance 总被引:3,自引:0,他引:3
The performance of sequential acquisition of m sequences, based on the sequential probability ratio test (SPRT), is studied. The authors consider a sliding correlator-type structure for the acquisition scheme, which the mean acquisition time is proportional to the average number of samples used for a synchronization test. Sequential acquisition requires the knowledge of the partial correlation of the pseudonoise (PN) sequence, however, as the partial correlation of an m sequence is difficult to model the authors propose an approximate upper bound. This is then piecewise linearized and used for designing the SPRT which is then compared to the fixed-dwell time technique, a scheme using the fixed sample size test. Numerical results show that the saving of acquisition time by the SPRT increases as the desired probabilities of errors and/or the input SNR decrease. Analytic results are verified by computer simulation 相似文献
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设计一种针对基于FFT的PN码捕获自适应限技术,对高斯环境下信号统计特性进行了推导,得出了适用于恒需警概率自适应门限算法的统计量,并用最大似然准则对统计量进行参数估计.最后仿真验证表明,该方法适合在低信噪比环境下完成PN码捕获. 相似文献
20.
This paper proposes a novel carrier Phase noise (PN) pre-correction scheme with an adaptive PN prediction algorithm for Single-carrier Frequency-division multiple-access (SC-FDMA) systems to alleviate degrada-tion due to the PN. Our proposed PN prediction algorithm is a modified polynomial fitting algorithm which is based on receding horizon principle. The parameters of the pre-diction model are optimized by using the algorithm on PN samples of the local oscillator signal in a training window. By using the optimized prediction model parameters and the latest PN samples, we can predict future PN samples. Then these predicted PN samples are put into our pro-posed PN pre-correction scheme and the SC-FDMA sym-bols at the transmitter are pre-compensated. Due to the absence of the radio frequency delay device, the proposed scheme has a low hardware complexity. Simulation results show that our proposed scheme can greatly reduce the ef-fect of the PN on the transmitted SC-FDMA signal. 相似文献