检索结果-内蒙古大学图书馆

International Conference on Ubiquitous and Future Networks

作者： Lin, Wei-Lun Feng Chia Univ Dept Commun Engn Taichung Taiwan

ISBN: (纸本)9781479989935

The error performance of minimum-bandwidth direct-sequence code division multiple access (MB-DS-CDMA) is studied for synchronous and asynchronous scenarios in Nakagami multipath fading channels. Comparing to the bandlimited raised cosine pulsed DS-CDMA systems, MB-DS-CDMA in both synchronous and asynchronous scenarios realizes Nyquist rate transmission with zero excess bandwidth, but only synchronous MB-DS-CDMA gives equivalent error performance, whereas asynchronous MB-DS-CDMA suffers degradation in error performance, which can be deemed as a trade-off by providing the ultimate Nyquist transmission rate. This work was supported by Ministry of Science and Technology, Taiwan, under contract NSC 102-2221-E-035-005.

关键词： error performance direct-sequence code-division multiple access code division multiple access Multipath fading Performance Evaluation code division Asynchronous

来源：评论

学校读者我要写书评

暂无评论

Performance comparison of chaotic spreading sequences generated by two different classes of chaotic systems in a chaos-based direct sequence-code division multiple access system

引用

IET COMMUNICATIONS 2013年第10期7卷 1024-1031页

作者： Rahnama, Nazila Talebi, Siamak Shahid Bahonar Univ Kerman Dept Elect Engn Kerman Iran

In the world of wireless communications, achieving a highly secure transmission at the lowest possible performance degradation has presented a major challenge and a number of conventional direct-sequence-code division multiple access (DS-CDMA)-based solutions have been put forward that deals with the issue. This study aims to overcome the challenge by introducing a new approach that employs a chaotic sequence in DS-CDMA system over fading channels. The proposed algorithm, which assumes a perfect sync between the transmitter and the receiver, generates a binary code by using a three-dimensional (3D) chaotic system. Simulations based on a flat-fading channel with additive white Gaussian noise and interuser interference reveal that the new approach outperforms codes generated by other classes of chaotic systems, that is, the 1D chaotic system. The results also proved the proposition's performance is comparable to conventional pseudo-noise spreading codes, the Gold code, in several key aspects including security of transmission, bit-error rate, code generation speed and the number of possible code sequences.

关键词： code division Chaotic systems direct-sequence code-division multiple access AWGN degradation of performance CDMA mobile communications flat fading channel spreading sequence transmitter receivers CARRIER SYSTEM binary code

来源：评论

学校读者我要写书评

暂无评论

Estimation of spreading sequences in LC-DS-CDMA signals based on sparse auto-encoder

引用

EVOLUTIONARY INTELLIGENCE 2020年第2期13卷 235-246页

作者： Qiang, Fangfang Zhao, Zhijin Shang, Junna Shen, Lei Hangzhou Dianzi Univ Sch Elect & Informat Hangzhou 310018 Peoples R China Hangzhou Dianzi Univ Sch Commun Engn Hangzhou 310018 Peoples R China Zhejiang Prov Key Lab Informat Proc Commun & Netw Hangzhou 310027 Peoples R China

A method based on a sparse auto-encoder (SAE) network for the estimation of spreading sequences in long-code direct-sequence code-division multiple access (LC-DS-CDMA) signals is proposed. First, a network classification model based on SAE and softmax classifier is established. Next, the effectiveness of the proposed method is verified by estimating Walsh sequences and m sequences. To estimate the spreading sequences, the LC-DS-CDMA signal is divided into fragments. Then, each user's spreading sequence is separated by the fast independent component analysis (Fast-ICA) algorithm, and the amplitude fuzziness is eliminated by the delay-and-multiply method. Finally, the spreading sequences are estimated by the SAE model. Experimental results showed that the proposed algorithm could effectively estimate the spreading sequences of LC-DS-CDMA signals. Compared to the existing matching algorithm and Fast-ICA algorithm, the estimation time required by the proposed algorithm was shorter, and its estimation performance at low signal-to-noise ratios was superior.

关键词： direct-sequence code-division multiple access Deep learning Sparse auto-encoder Blind source separation Signal analysis

来源：评论

学校读者我要写书评

暂无评论

Navigation With Cellular CDMA Signals-Part I: Signal Modeling and Software-Defined Receiver Design

引用

IEEE TRANSACTIONS ON SIGNAL PROCESSING 2018年第8期66卷 2191-2203页

作者： Khalife, Joe Shamaei, Kimia Kassas, Zaher M. Univ Calif Riverside Dept Elect & Comp Engn Riverside CA 92521 USA

A software-defined receiver (SDR) for navigation using cellular code-division multiple access (CDMA) signals is presented. The cellular forward link signal structure is described, and models for the transmitted and received signals are developed. Particular attention is paid to relevant information that could be extracted and subsequently exploited for positioning and timing purposes. The pseudorange from the proposed receiver is modeled and the pseudorange error is studied in an additive white Gaussian channel. Experimental results with aerial and ground vehicles utilizing the proposed SDR are presented demonstrating a close match between the variation in pseudoranges and the variation in true ranges between the receiver and two cellular CDMA base transceiver stations (BTSs). Moreover, the dynamics of the discrepancy between the observed clock biases of different sectors of the same BTS cell is modeled and validated experimentally. The consistency of the obtained model is analyzed through experimental tests in different locations, at different times, and for different cellular providers.

关键词： Radionavigation signals of opportunity opportunistic navigation direct-sequence code-division multiple access software radio system identification

来源：评论

学校读者我要写书评

暂无评论

Asynchronous Detection and Identification of multiple Users by Multi-Carrier Modulated Complementary Set of sequences

引用

IEEE access 2018年 6卷 22054-22069页

作者： Aparicio, Jaoquin Shimura, Takuya Japan Agcy Marine Earth Sci & Technol Dept Engn Geomarine Sci Yokosuka Kanagawa 2370061 Japan

The correct detection of arrivals is a crucial step in any communication system, in order to achieve frame synchronization. This step is even more relevant in underwater acoustic communications, as the medium is characterized by hazardous phenomena such as long multipath delays and non-uniform Doppler shifts, which hinder the detection process. All these phenomena make the detection of arrivals and identification of multiple users in underwater communication systems a challenging task. In this paper, a multi-user detector is presented. The detection is based on the direct-sequence code-division multiple access technique, by using a combination of two sequences as a preamble: a Zadoff-Chu sequence that provides candidate peaks and frame synchronization, and a complementary set of sequences (CSS) that validates the true Zadoff-Chu arrival while at the same time identifies the user. Both sequences are modulated using multi-carrier techniques, and the users can transmit asynchronously to the channel. In the case of CSS, multi-carrier modulation techniques allow performing channel equalization and demodulation at the receiver in a simple manner, enabling the correlation of the CSS at bit level, thus keeping its ideal correlation properties. Sea trials were conducted in February 2017 at Suruga Bay, Japan, in which the reception of two different users was analyzed under different noise and multipath conditions, as well as uniform and non-uniform Doppler shifts. The results show that, even under strong multipath and non-uniform Doppler shifts caused by roll and pitch motions, the receiver is able to detect and identify the user in 98% of the transmitted packets.

关键词： direct-sequence code-division multiple access frame synchronization multiaccess communication OFDM SC-FDMA underwater communication

来源：评论

学校读者我要写书评

暂无评论

Navigation With Cellular CDMA Signals-Part II: Performance Analysis and Experimental Results

引用

IEEE TRANSACTIONS ON SIGNAL PROCESSING 2018年第8期66卷 2204-2218页

作者： Khalife, Joe Kassas, Zaher M. Univ Calif Riverside Dept Elect & Comp Engn Riverside CA 92521 USA

A framework for navigation using cellular code division multiple access (CDMA) signals is studied in this paper. Theoretical lower bounds on the navigation performance using pseudorange measurements drawn from the cellular CDMA base transceiver stations (BTSs) are derived. Moreover, the navigation performance for a mapper/navigator framework is studied in the presence of timing discrepancies between the mapper and navigator. In this framework, a mapping receiver (mapper) estimates the stochastic dynamic clock biases of the BTSs and shares these estimates with a navigating receiver (navigator). The optimal navigation performance of the mapper/navigator framework in the presence of timing discrepancies is analyzed, and a practical upper bound on the resulting position error is derived. Experimental results for a ground vehicle and unmanned aerial vehicles (UAVs) are presented. The ground vehicle results show a mean distance difference of 5.51 m between the cellular CDMA-only navigation solution and a GPS navigation solution in the absence of clock bias discrepancies. The UAV results show an improvement of 10.57 m in the root-mean-square error of the cellular CDMA navigation solution, when the sector clock bias discrepancies are accounted for utilizing the statistical model relating observed clock biases from different sectors of the same BTS cell.

关键词： Radionavigation signals of opportunity opportunistic navigation direct-sequence code-division multiple access wireless sensor networks

来源：评论

学校读者我要写书评

暂无评论

Simultaneous Transmission of Biomedical Signals Using DS-CDMA

Simultaneous Transmission of Biomedical Signals Using DS-CDM...

引用

International Conference on Innovation in Engineering and Technology (ICIET)

作者： Hasan-Uz-Zaman Ashik A. B. M. Aowlad Hossain Dept. of Electronics and Communication Engineering Khulna University of Engineering & Technology Khulna Bangladesh

ISBN: (纸本)9781538652305;9781538652299

Telemedicine system requires high speed and secured data transmission. Recent studies in transmission of biomedical signals are mostly based on Bluetooth devices that use Frequency-hopping spread spectrum (FHSS) where the transmission range (10-100 m) and speed (1-3 Mbps) are limited. However, IEEE 802.11 Wireless LAN or wireless fidelity (Wi-Fi) uses direct sequence spread spectrum (DSSS) in physical layer that offers high speed simultaneous transmission of several leads of biomedical signals. In this paper, we have simulated DS-CDMA for transmission of several biosignals in Additive white Gaussian noise (AWGN) environment. As all the signals are spread over the entire bandwidth in DS-CDMA, it facilitates security of information to the end user. Furthermore, Walsh code which is a linear and mutually orthogonal code, is assigned to several leads of biosignals that minimizes the signal interference. To estimate the performance of the system, error calculating parameters like RMSE, STD and PRD are measured. For 12 lead ECG data average PRD is obtained 0.6% when SNR is 8 dB (out of scale 10). Likewise, for EEG and stress data the errors are also very low. The simulated results depict better performance of the system even in presence of dominant noise.

关键词： AWGN Bluetooth code division multiple access electrocardiography electroencephalography frequency hop communication interference (signal) linear codes medical signal processing orthogonal codes spread spectrum communication telecommunication security tele AWGN orthogonal codes Frozen soils frequency hop communication code division multiple access telecommunication security interfering signal direct-sequence code-division multiple access Bluetooth medical signal processing Spread spectrum communication simultaneous transmission linear codes Electroencephalography Electrocardiography

来源：评论

学校读者我要写书评

暂无评论

Multiuser detectors for band-limited direct-sequence code-division multiple-access systems with multitone jamming and generalised-K fading

引用

IET COMMUNICATIONS 2010年第17期4卷 2021-2031页

作者： Mehdi, H. Teh, K. C. Li, K. H. Nanyang Technol Univ Sch EEE Singapore 639798 Singapore

In this study, the authors analyse the bit-error rate (BER) performance of band-limited direct-sequence code-division multiple-access (DS-CDMA) systems employing two types of multiuser detectors, namely, linear decorrelator with whitening (LDW) and linear minimum mean-squared error (MMSE) detector over frequency-selective multipath channels with multitone jamming (MTJ). The authors consider the generalised-K distribution in order to include both shadowing and small-scale fading effects. Generalised-K distribution is generic and versatile as it can incorporate various composite fading and shadowing effects observed in wireless communication channels with mathematical tractability. The authors derive analytical BER expressions that are functions of band-limited pulse shapes, MTJ parameters and shadowing and fading parameters of the wireless channel. The system incorporates either a Nyquist pulse or a cosine band-limited pulse shape. Numerical results show that the systems with cosine pulse demonstrate better BER performance than the ones with Nyquist pulse in the presence of MTJ. Furthermore, in the presence of MTJ, MMSE-based systems demonstrate improved BER performance as compared to LDW-based systems. The authors also observe that the systems employing two-dimensional scheme, that is, the combination of space and multipath diversity, outperform the ones with multipath diversity scheme.

关键词： fading color sequence coding bit error rate performance Multi-Tone Jamming direct-sequence code-division multiple access SHADOW EFFECT Multipath channels K-distribution Pulse shape Shadowing (Histology)

来源：评论

学校读者我要写书评

暂无评论

Error probability analysis of multicarrier direct sequence code division multiple access system under imperfect channel estimation and jamming in a Rayleigh fading channel

引用

IET SIGNAL PROCESSING 2010年第1期4卷 89-101页

作者： El-Mahdy, A. E. German Univ Fac Informat Engn & Technol Cairo Egypt

The performance of a multicarrier direct sequence code division multiple access (MC-DS-CDMA) system in fading environment has been extensively analysed in the literatures. The analysis that is available in the literatures did not take into account the impact of jamming and channel estimation errors on the performance of the system. In this study, closed-form expressions of the average bit error probability (BEP) of the MC-DS-CDMA system with channel estimation errors in the presence of partial band, broadband and multitone jamming are derived in a Rayleigh fading channel. The analysis shows that the magnitude of the normalised correlation between the actual and the estimated complex fading channel gain, A, greatly affects the performance of the MC-DS-CDMA system. For large signal-to-noise ratio, the average BEP with A 1 and without multiple access interference (MAI) tends to zero. When A not equal 1, the BEP of the system exhibits an error floor even without MAI. This error floor increases as the number of users increases. It is also shown that increasing the number of the system subcarriers enhances the system performance against jamming.

关键词： Raleigh fading channels System performance direct-sequence code-division multiple access error floor Multi-Tone Jamming ABER channel estimation jamming MC-DS-CDMA code division CDMA mobile communications

来源：评论

学校读者我要写书评

暂无评论

Joint transmit/receive one-tap minimum mean square error frequency-domain equalisation for broadband multicode direct-sequence code division multiple access

引用

IET COMMUNICATIONS 2010年第14期4卷 1752-1764页

作者： Takeda, K. Adachi, F. Tohoku Univ Grad Sch Engn Dept Elect & Commun Engn Aoba Ku Sendai Miyagi 9808579 Japan

Multicode direct-sequence code division multiple access (DS-CDMA) can flexibly support multimedia services with various data rates simply by changing the code multiplexing order. The use of simple one-tap frequency-domain equalisation (FDE) at a receiver is known to improve the bit error rate (BER) performance of multicode DS-CDMA in a severe frequency-selective fading environment. However, the BER performance improvement is limited due to the presence of the residual inter-chip interference (ICI). The authors propose a joint transmit/receive minimum mean square error (MMSE) FDE, which carries out one-tap transmit FDE and one-tap receive FDE jointly based on the MMSE criterion. The authors theoretically derive a suboptimal set of transmit and receive FDE weights and investigate the BER performance improvement by computer simulation in a freqeuncy-selective Rayleigh fading channel. The proposed scheme improves the received signal-to-interference plus noise ratio after despreading, and consequently, the BER performance can be significantly improved compared to the conventioal receive MMSE-FDE by (a) making the variations in the equivalent channel gain shallower to reduce the residual ICI for large code multiplexing order U and (b) allocating the transmit power to the frequencies having good condition to improve the received signal-to-noise ratio for a small U. This is conformed by the computer simualtion.

关键词： TRANSMITTING Data transfer rates ICI direct-sequence code-division multiple access bit error rate performance performance boost Mini Mental State Examination Multimedia services Transmitter power Mean square error multipleXOR

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：