检索结果-内蒙古大学图书馆

Single-user performance of direct-sequence code-division multiple-access using relay diversity and power allocation

IET COMMUNICATIONS 2008年第3期2卷 462-472页

作者： Fang, W. Yang, L. -L. Hanzo, L. Univ Southampton Sch Elect & Comp Sci Southampton SO17 1BJ Hants England

In this contribution, the authors investigate the single- user- bound performance of a direct- sequence code- division multiple- access ( DS- CDMA) system, where one source mobile terminal ( MT) communicates with its base- station ( BS) with the assistance of multiple relays. The authors assume that the communications channels experience both propagation pathloss and fast fading, and that the channels from the source MT to the BS and relays as well as that from the relays to the BS may experience different fast fading modelled correspondingly by Nakagami- m distributions. In the study, they assume both the single- user combining using maximal ratio combining and the multiuser combining, which are derived based on the maximum signal- to-interference-plus- noise ratio criterion. The bit- error- rate ( BER) performance of the DS- CDMA is investigated associated with considering the locations of the relays as well as the power- allocation among the source MT and relays. From the study and simulation results, it can be shown that the achievable BER performance of the DS- CDMA depends on the locations of the relays and also on the power- allocation among the source MT and relays. When the relays of a source MT are chosen from a different area, the power- allocation should also be adjusted correspondingly in order to achieve the minimum BER. Furthermore, when optimum power-allocation is assumed, the BER performance of the DS- CDMA can be significantly improved, when increasing the number of relays assisting the source MT.

关键词： diversity reception single-user combining channel allocation multiuser combining Nakagami channels code division multiple access fading channel maximal ratio combining direct-sequence code-division multiple-access relay diversity error statistics bit-error-rate maximum signal-to-interference-plus-noise ratio criterion power allocation Nakagami-m distribution spread spectrum communication

来源：评论

学校读者我要写书评

暂无评论

Robust chip-matched myriad filter-based multiuser receiver for impulsive channels

引用

SIGNAL PROCESSING 2008年第5期88卷 1216-1232页

作者： Lim, Heng-Siong Chuah, Teong-Chee Chuah, Hean-Telk Multimedia Univ Fac Engn & Technol Melaka 75450 Malaysia Multimedia Univ Fac Engn Jalan Multimedia Cyberjaya 63100 Selangor Malaysia

The problem of impulsive noise suppression for direct-sequence code-division multiple-access (DS-CDMA) systems employing multiuser detection in impulsive channels is treated. Prior to the detector, linear chip-matched filter is commonly used for continuous-to-discrete-time conversion. The effects of the non-Gaussian impulsive channel in an asynchronous system are studied by modeling the samples of noise before front-end filtering as a symmetric alpha-stable process. The error probability performance of the linear correlation receiver under these conditions is compared to that for additive white Gaussian noise (AWGN) channels. It is found that the approach performs poorly in the presence of impulsive noise. To overcome this problem, an impulse mitigation strategy derived from the myriad filtering framework is employed to produce reliable soft channel outputs over a wide range of noise characteristics. The asymptotic error probability performance of the chip-matched myriad filter (CMMyF)-based receivers is then computed and compared to the computer simulated expression. The results show that, in contrast to the linear filter, the CMMyF is effective in removing the impulsive noise and leads to a reliable recovery of the desired chips with low estimation error. The proposed method proves to be fruitful in that the subsequent k-opt multiuser detector is safe to process the chip samples obtained hereafter, thereby retaining all its optimality and advantages. (C) 2007 Elsevier B.V. All rights reserved.

关键词： symmetric alpha-stable distributions impulsive noise matched myriad filter direct-sequence code-division multiple-access multiuser receivers

来源：评论

学校读者我要写书评

暂无评论

Serial acquisition performance of single-carrier and multicarrier DS-CDMA over Nakagami-m fading channels

引用

IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2002年第4期1卷 692-702页

作者： Yang, LL Hanzo, L Univ Southampton Dept Elect & Comp Sci Southampton SO17 1BJ Hants England

In this paper, we investigate the issue of pseudo noise (PN) code acquisition in single-carrier and multicarrier (MC) direct-sequence code-division multiple-access (DS-CDMA) systems, when the channel is modeled by frequency-selective Nakagami-m fading. The PN code acquisition performance of single-carrier and MC DS-CDMA systems is analyzed and compared when communicating over Nakagami-m fading channels under the hypothesis of multiple synchronous states (H-1 cells) in the. uncertainty region of the PN code. In the, context of MC DS-CDMA, the code acquisition performance is evaluated, when the correlator outputs of the subcarriers associated with the same phase of the local PN code replica are noncoherently combined by using equal gain combining (EGC) or selection combining (SC) schemes. The performance comparison of the above mentioned schemes shows that the code acquisition performance of the MC DS-CDMA scheme, especially when using the EGC scheme, is more robust, than that of single-carrier DS-CDMA schemes communicating over the multipath Nakagami-m- fading channels encountered. However, our code acquisition performance comparison also shows that if the detection threshold was set inappropriately, the performance might be degraded, even if the channel fading becomes less severe.

关键词： code acquisition direct-sequence code-division multiple-access equal gain combining multicarrier transmission Nakagami fading channel selection combining

来源：评论

学校读者我要写书评

暂无评论

Performance analysis of a linear MMSE receiver for bandlimited random-CDMA using quadriphase spreading over multipath channels

引用

IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2004年第4期3卷 1053-1066页

作者： Mirbagheri, A Yoon, YC Univ Waterloo Ctr Wireless Commun Dept Elect & Comp Engn Waterloo ON N2L 3G1 Canada

This paper analyzes the bit-error-rate (P-e) performance of a linear minimum mean-square error (LMMSE) receiver for bandlimited direct-sequence code-division multiple-access systems which use quadriphase spreading with aperiodic pseudonoise (PN) sequences. The analysis is based on the improved Gaussian approximation (IGA) with focus on chip pulse shaping. It shows that the IGA reduces to the standard Gaussian approximation (SGA) if 1) random quadriphase spreading is employed, 2) the spreading factor takes moderate to large values, and 3) the chip pulse excess bandwidth (BW) is zero. Hence, the SGA, known for its inaccuracy in low regions of P-e, remains an accurate approximation even when the number of active users in the system is small as long as the aforementioned conditions are met. The analysis holds for either matched or different transmit and receive filters. Consequently, closed form conditional P-e expressions are derived for the coherent selective Rake and the LMMSE receivers and verified with Monte Carlo simulations. Numerical results are presented to illustrate the performance improvement achieved by the LMMSE receiver which, in contrast to the coherent selective Rake receiver, not only suppresses interference when the excess BW of chip pulse is nonzero, but also harnesses the energy of all paths of the desired user. Under the examined scenarios tailored toward current narrowband system settings, the LMMSE receiver achieves 60% gain in capacity over the selective Rake receiver. A third of the gain is due to interference suppression capability of the receiver while the rest is credited to its ability to collect the energy of the desired user diversified to many paths. Future wideband systems will yield an ever larger gain.

关键词： bit-error rate direct-sequence code-division multiple-access (DS-CDMA) Gaussian approximation long spreading sequences minimum mean-square error (MMSE) pulse shaping Rake receiver

来源：评论

学校读者我要写书评

暂无评论

Orthogonalizing matched filtering (OMF) detector for DS-CDMA mobile communication systems

引用

IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 1999年第1期48卷 188-197页

作者： Fukawa, K Suzuki, H NTT Mobile Commun Network Inc Kanagawa 2398536 Japan Tokyo Inst Technol INCOCSAT TIT Tokyo 152 Japan

This paper proposes a new blind interference suppression scheme for direct-sequence code-division multiple-access (DS-CDMA) mobile communication systems. The proposed detector, the orthogonalizing matched filtering (OMF) detector, consists of a bank of despreading filters and a signal combiner. The received composite signal is first despread by the filters in the bank. The despreading filter outputs are then weighted and combined. The weight vector is adaptively determined and updated so that the average combined signal power is minimized while keeping the combiner's response to the desired signal constant. The proposed algorithm for OMF weight updating requires neither knowledge about other users' spreading sequences nor desired user's signal reference. The similarity between the proposed OMF detector and Applebaum's sidelobe canceller adaptive array is discussed in detail. Results of computer simulations are shown to demonstrate the OMF performance in various mobile communications environments.

关键词： Applebaum's sidelobe canceller blind operation direct-sequence code-division multiple-access interference suppression mobile communication

来源：评论

学校读者我要写书评

暂无评论

Nonparametric PN code acquisition using the signed-rank statistic for DS/CDMA systems in frequency-selective Rician fading channels

引用

IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2002年第5期51卷 1138-1144页

作者： Kim, HG Song, I Yoon, S Park, SR Samsung Elect Co Core Technol Res Team Suwon 442742 Gyeonggi Do South Korea Korea Adv Inst Sci & Technol Dept Elect Engn & Comp Sci Taejon 305701 South Korea Harvard Univ Div Engn & Appl Sci Cambridge MA 02138 USA

In this paper, signed-rank based nonparametric detectors are used for pseudonoise (PN) code acquisition in frequency-selective Rician fading channels. We first derive the locally optimum rank detector and then propose the locally suboptimum rank (LSR) and kth order modified signed-rank (MSRk) detectors using approximate score functions. We compare the hybrid parallel double-dwell scheme using the LSR and MSRk detectors with that using the conventional squared-sum (SS) and modified sign (MS) detectors. From the simulation results, it is shown that the LSR and MSRk detectors perform better than the SS detector using the cell averaging constant false-alarm rate processor and the MS detector by about 2-3 dB.

关键词： direct-sequence code-division multiple-access systems (DS/CDMA) nonparametric detection pseudonoise (PN) code acquisition signed-rank statistic

来源：评论

学校读者我要写书评

暂无评论

Dynamic code reservation multiple access for supporting various-bit-rate integrated traffics in slotted DS-CDMA systems

引用

COMPUTER COMMUNICATIONS 2000年第9期23卷 793-801页

作者： Jeong, EH Khil, AR Kim, MK Maeng, SR Korea Adv Inst Sci & Technol Dept Comp Sci Yusung Gu Taejon 305701 South Korea Soongsil Univ Dept Comp Sci Dongjak Gu Seoul 156743 South Korea Univ Ulsan Sch Comp Engn & Informat Technol Nam Gu Ulsan 680749 South Korea

Recently, several works have been proposed for media access control protocols which are based on slotted direct-sequence code-division multiple-access and support integrated traffics. In this paper, we propose dynamic code reservation multiple access (DCRMA) which can enhance the previous works. DCRMA extends a minislot technique to the integrated traffic environment and supports connection-oriented and connectionless traffic with various bit rates. Additionally, DCRMA develops a simultaneous transmission scheme to reduce average message transmission delay for connectionless traffic. Packet dropping probability is analyzed for connection-oriented traffic with various bit rates using an embedded Markov chain model. Simulations are also performed to further investigate the integration of connection-oriented and connectionless traffics. (C) 2000 Elsevier Science B.V. All rights reserved.

关键词： media access control direct-sequence code-division multiple-access integrated traffic service

来源：评论

学校读者我要写书评

暂无评论

Partial zero-forcing adaptive MMSE receiver for DS-CDMA uplink in multicell environments

引用

IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2002年第5期51卷 1066-1071页

作者： Lee, JH Kim, HM Samsung Elect Co Telecommun R&D Ctr Global Stand & Strategy Team Suwon 442742 Gyeonggi Do South Korea Korea Adv Inst Sci & Technol Dept Elect Engn & Comp Sci Div Elect Engn CSPLAB Taejon 305701 South Korea

Recently, adaptive multi-user detection techniques for interference suppression in direct-sequence code-division multiple-access (DS-CDMA) systems have gained much attention since they do not require any information on interfering users. In the uplink of DS-CDMA systems, however, the base station receiver typically knows the spreading waveforms of the users within its cell but does not know those of the users in other cells. In this paper, we propose a partial zero-forcing adaptive minimum mean squared error (MMSE) receiver for the DS-CDMA uplink utilizing the spreading waveforms known at the base station as well as training data. The proposed receiver first removes the intracell interference using a linear filter based on the knowledge of the spreading waveforms of the interfering users within the cell. Then the intercell interference remaining in the output of the linear filter is mitigated by adaptive MMSE detection. To speed up the convergence of the adaptive filter weights without loss of the steady-state performance, we develop a modified least mean square (LMS) algorithm based on the canonical representation of the filter weights. It is shown through analysis and simulation results that the proposed receiver improves the convergence speed and the steady-state performance.

关键词： adaptive minimum mean squared error (MMSE) detection direct-sequence code-division multiple-access (DS-CDMA) uplink intercell interference multicell

来源：评论

学校读者我要写书评

暂无评论

Performance. analysis O³BPSK LDD for asynchronous CDMA systems in the presence of synchronization errors

引用

IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2003年第4期52卷 958-969页

作者： Wen, JF Wen, CK Wu, HT Natl Tsing Hua Univ Inst Commun Engn Hsinchu 300 Taiwan

A convenient signaling scheme, termed orthogonal on-off binary phase-shift keying ((OBPSK)-B-3), along with a simple one-shot linear decorrelating detector (LDD), was proposed by Zheng and Barton as a technique,for near-far resistant detection in the asynchronous direct-sequence code-division multiple-access (DS/CDMA) systems. The temporally adjacent bits from different users in the received signals are decoupled by using the on-off signaling, and the data rate is maintained with no increase in the transmission rate by adopting an orthogonal structure. This paper examines the effects of three classes of synchronization errors, including time-delay errors, carrier phase errors, and carrier frequency errors, on the performance of the (OBPSK)-B-3 LDD in an asynchronous CDMA near-far environment. It is shown that the performance of the (OBPSK)-B-3 LDD has an advantage over that of the isolation bit insertion detector in the presence of synchronization errors. In addition, numerical results show that the, (OBOSK)-B-3 LDD still offers,a good near-far resistant property as long as synchronization errors do not exceed some practical limit.

关键词： direct-sequence code-division multiple-access (DS/CDMA) linear decorrelating detector on-off binary phase-shift keying (BPSK) one shot synchronization errors

来源：评论

学校读者我要写书评

暂无评论

Noncoherent MLSE in DS-CDMA wireless systems with antenna arrays

引用

IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2003年第6期52卷 1435-1446页

作者： Abrardo, A Univ Siena Dept Informat Engn I-53100 Siena Italy

This paper addresses the noncoherent detection problem for direct-sequence code-division multiple-access (DS-CDMA) signals in the presence of antenna arrays at the base station. An ideal open-loop power control, which compensates for the long-term variations due to path loss and shadowing experienced by the mobile users, is assumed. Then, the noncoherent maximum-likelihood sequence-estimation problem is analyzed under the assumption of spatially white interference. The contribution of this paper is to extend previous results obtained by the author in [17] for the case of multiantenna receivers, including the derivation and analysis of two suboptimal detectors based on an approximate maximization of the transmitted symbols likelihood. The first detector works as a traditional squared envelope combiner, which fully exploits the K diversity degrees provided by the multiple antenna system. In the second case, the receiver assumes a perfect knowledge of antenna response vector, so that spatial filtering of the received signal is made possible. Simulation and theoretical results are provided for a widely used circular ring of scatterers spatial channel model, which allows analysis in a wide range of different environmental conditions.

关键词： direct-sequence code-division multiple-access (DS-CDMA) systems multiple differential phase-shift keying (M-DPSK) modulations maximum-likelihood sequence estimator (MLSE) noncoherent detection multiple antenna

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：