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1.
Zero correlation window (ZCW) or zero correlation zone (ZCZ) sequence can be used in quasi-synchronous code division multiple access (QS-CDMA) system to eliminate multiple access and multipath interferences. However, as the length of ZCW or ZCZ increases, fewer sequences are available. Recently, a new concept, sequence set with group-wise zero correlation window is introduced, which can increase the number of available sequences for a QS-CDMA system. In this article, a new method for generating sequence set with group-wise zero correlation window is presented. This method is based on a Hadamard matrix of size N×N and a pair of Hadamard matrices of size M×M. Compared with previous methods, the proposed sequence set has a group-wise zero correlation window for both periodic and aperiodic cross-correlation functions. 相似文献
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高斯整数零相关区(ZCZ)序列集作为准同步码分多址(QS-CDMA)系统的地址序列不仅能抑制系统的多径干扰(MAI)和多址干扰(MPI),而且为系统提供高传输码率和高的频谱利用率,但目前这种地址序列的构造结果还较少,针对此问题本文提出了一种利用过滤操作构造高斯整数ZCZ序列集和完美高斯整数序列的方法.基于完美序列和周期ZCZ序列集本文获得了最佳或几乎最佳的高斯整数ZCZ序列集,同时基于完美序列构造了周期为奇数和偶数的完美高斯整数序列.本文的构造结果为高速QS-CDMA系统提供了更多的地址选择空间. 相似文献
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This paper presents a multi-rate quasi-synchronous CDMA (QS-CDMA) system with QPSK modulation based on the new signature waveforms,
namely GPZ-chip waveforms which are constructed by the generalized pairwise Z-complementary (GPZ) codes and optimal chip waveforms.
According to the properties of GPZ-chip waveforms, the multiple access interference of different users can be reduced or eliminated.
The interferences among different streams of the same user are handled by an optimal (or suboptimal) multi-stream detector(s).
The performance of the proposed system is simulated and analyzed in a cellular communication environment consisting of multipath
fading. The result shows that the proposed system has similar performance as compared to the single-rate QS-CDMA system employing
GPZ codes with one chip waveform due to the properties of multi-stream detection. Also, the proposed system can achieve a
significant interference reduction as compared to the multi-rate system employing concatenated WH/m sequence sets with one
chip waveform due to the zero correlation zone properties of the GPZ-chip waveforms, thus resulting better BER performance. 相似文献
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In this paper, a class of generalized orthogonal sequences (GOS) is presented with the the following characteristics, (1) the cross-correlations in the vicinity of zero shift (zero shift is excluded) between two arbitrary sequences from different GOS sets are zeros; (2) the cross-correlations in the vicinity of zero shift between two arbitrary sequences from different subsets of the same GOS set are zeros; and (3) two arbitrary different sequences from the same subset of the same GOS set are orthogonal. By applying the GOS sets to multi-rate multi-cell quasi-synchronous CDMA (QS-CDMA) system, the system interference is analyzed and compared with that of well-known concatenated orthogonal/PN sequence sets. It is shown that due to the zero correlation properties in the vicinity of zero shift, the interference of system employing GOS sets can achieve a bigger reduction than concatenated orthogonal/PN sequence sets, thus resulting better BER performance than that of latter under the same conditions. 相似文献
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交织法构造最佳或几乎最佳低零相关区序列集 总被引:1,自引:1,他引:0
该文提出一种新的移位序列的构造方法,通过给移位序列赋予不同的值,得到一类新的移位序列。基于这种移位序列,利用交织法得到了一类具有灵活相关区长度并且参数接近甚至达到理论界限的低零相关区序列集,扩大了交织法的应用范围,得到了更多的适用于准同步CDMA系统的扩频序列集。 相似文献
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The construction of zero correlation zone (ZCZ) Gaussian integer sequence set was researched.Based on binary orthogonal matrices,ZCZ ternary sequence sets were constructed by adding zeros at first.Then the ternary ZCZ squences were transformed into Gaussian integer sequences by using a perfect Gaussian integer sequence without changing the ideal autocorrelation functions and crosscorrelation functions in the zero correlation zone.The proposed ZCZ Gaussian integer sequence sets are optimal or almost optimal with respect to the Tang-Fan-Matsufuji bound. 相似文献
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Seong Ill Park So Ryoung Park Iickho Song Suehiro N. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2000,46(4):1448-1458
In this paper, a new class of polyphase sequences for CDMA systems and its generation method are suggested, and the correlation properties of the sequence are investigated. The performance of the sequence in quasi-synchronous CDMA (QS-CDMA) systems is investigated under a frequency-selective, time-nonselective, slow Nakagami fading channel with additive white Gaussian noise (AWGN). It is shown that the performance of the QS-CDMA systems using the suggested sequence is independent of the number of users and is much better than that using the PN sequence 相似文献
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在准同步CDMA系统中,使用零相关区(ZCZ)序列能够避免共信道冲突和多址干扰。通过应用序列偶理论,基于交织技术和一类最优ZCZ序列集中的移位序列,成功构造出了具有良好自相关和互相关性能的ZCZ序列偶集,不但可以生成不同的零相关区,而且使得序列偶集中的所有序列都循环移位不等价。仿真结果表明,它的性能优良,适于作准同步CDMA系统的扩频序列。 相似文献
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Quasisynchronous (QS) Code Division Multiple Access (CDMA) is currently being considered for a variety of wireless applications
and services because QS-CDMA enables information transmission with a good quality of service. In this paper, for M-ary signaling,
the Symbol Error Rate (SER) performance of QS-CDMA communication system with a maximal ratio combiner (MRC) over frequency-selective,
time-nonselective multipath Generalized Gamma (GG3) fading channels is derived not only for any deterministic spreading sequences
but also for any chip-limited chip waveforms, and it is investigated for Rectangular, Half-Sine, and Raised-Cosine chip waveforms
by means of numerical and simulation results. Numerical and simulation results show that the performance of QS-CDMA is as
good as or slightly better than synchronous CDMA (S-CDMA) when the maximum quasisynchronous delays do not need to be less
than some specific values depending on the path power scattering. With this flexibility of quasisynchronous delays, both the
transmitter and receiver complexities are reduced as quasisynchronous communication is a challenging task for researchers.
Additionally, since not only the spreading sequences but also the partial autocorrelation functions of the chip waveform are
influential on the performance of multipath QS-CDMA, a measure, Partial Power Ratio (PPR) is defined based on these partial
autocorrelation functions in order to select or design a chip waveform for quasisynchronous communication. Furthermore, results
show that QS-CDMA using the chip waveform whose PPR is greater has better performance.
相似文献
Oğuz Kucur (Corresponding author)Email: |
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Biqi Long Ping Zhang Jiandong Hu 《Vehicular Technology, IEEE Transactions on》1998,47(4):1268-1275
A generalized quasi-synchronous code-division multiple-access (QS-CDMA) system for digital mobile radio communications is proposed. In a QS-CDMA system, the relative time delay between the signals of different users is random and restricted in a certain time range, that is, the signals are quasi-synchronous. The analysis shows that the multiple-access interference (MAI) of the QS-CDMA system is determined by the cross-correlation between spreading codes around the origin. To minimize the MAI of the QS-CDMA system, we design a new set of spreading codes. The performance is evaluated according to the criteria of the bit error rate (BER). Analytic results of the BER are obtained by using two methods: Gaussian approximation and characteristic function approaches, which are checked by modified Monte Carlo computer simulations known as “importance sampling.” The results indicate that the performance of the QS-CDMA system using the spreading codes we construct is much improved 相似文献
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该文基于任意两个NN Hadamard矩阵,构造出一类三元非周期零相关区序列集。与Donelan和OFarrell的构造方法相比,该文构造出的序列具有较高的能量效率。又进一步构造出两个相互正交的具有非周期零相关区的三元序列集,这样就可以提供更多的能够在准同步CDMA系统中使用的序列。 相似文献
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在CDMA系统中,采用正交序列可以有效地减小多址干扰的影响。然后,当由于多径衰落的影响使码片间的相对移位增加时,系统中用户扩频序列间的相互正交性减弱,导致性能大大恶化。本文基于新近提出的广义正交序列,分析了采用该序列的多载波直接序列码多分址系统在瑞利衰落信道中的误比特性能。数值结果表明,当扩频序列间相互移位在零相关区之内时,扩频序列仍可保持正交,因而大大提高了系统误比特性能。 相似文献
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本文给出两种新的移位序列集的构造方法,同时计算出不等价移位序列集数量的上界.提出移位序列起始点和初始距离的概念,CBIID方法通过设计合适的初始距离构造多个不等价移位序列集,可以利用交织技术获得多个不等价低零相关区序列集,该方法灵活选择起始点,是对现有不等价移位序列构造方法的扩展.CBVID方法以此为基础,并在一个移位序列集合中基于不同的初始距离构造移位序列,增加了移位不等价低零相关区序列集合的数量,与现有方法相比,可以构造更多的适合多小区准同步码分多址通信系统的扩频序列集,不同小区分配的低零相关区序列集移位不等价,降低不同小区间用户的干扰. 相似文献
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点对多点无线局域网中直扩序列选取 总被引:1,自引:0,他引:1
扩频序列的选择和构造是扩频通信系统设计的关键技术之一,系统的抗干扰、抗多径衰落、抗截获、保密、同步实现等均与所采用的扩频序列密切相关,扩频序列良好的相关特性和随机性对系统的性能具有决定性的作用。在点对多点通信系统中采用直接序列扩频方式,结合实际需求,通过对m序列、M序列、gold序列和kasami序列进行充分分析和仿真,得到了5种长度相关性能最优的直扩序列。 相似文献
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Xu Duan Lin Kyung Hi Chang 《Communications, IEEE Transactions on》1997,45(2):221-226
Direct sequence (DS) code-division multiple-access (CDMA) is a modulation and multiple access technique currently being implemented in digital cellular mobile radio communication systems. The conventional quasisynchronous (QS) DS-CDMA communication system is generalized, and the problem of optimal spreading pseudonoise (PN) sequence design for new QS DS-CDMA communication systems is formulated. The classes of optimal PN sequences which have good pseudo-randomness and very small cross-correlation values for some range of offsets are designed by using a matrix-based approach. In contrast to the case of the other sequences, the optimal PN sequences produce small multiple-access interference (MAI) which is not affected by the number of users if there are sufficiently large number of users in the link. The new results are compared with the commonly used PN sequences to prove the superiority of our designed sequences, and the system performance of the QS-CDMA systems using different PN sequences are also evaluated 相似文献