共查询到17条相似文献,搜索用时 46 毫秒
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瑞利衰落信道中MC-CDMA系统的载波频率偏移性能 总被引:1,自引:0,他引:1
多载波CDMA(MC-CDMA)技术结合了OFDM和CDMA技术的优点,在无线衰落信道中传输高速数据时具有突出的性能。但由于MC-CDMA采用了多载波技术,载波频率偏移对系统性能的影响非常大。本文对瑞利衰落信道下存在载波频率偏移的MC-CDMA系统性能进行了理论分析并对误码率进行了详细讨论。 相似文献
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提出一种通用的多载波频率分集CDMA系统基带发射、瑞利信道以及相关接收的矩阵信号分析模型。通过分析可以看出,多载波频率分集CDMA系统是一种高效的并行调制技术,它使信道和信号之间的卷积关系变成了线性加权关系,有效地抑制了符号间干扰和码间干扰,同时还具有频率分集的优点。对多载波频率分集CDMA系统在BPSK调制下的理论误码性能进行了深入探讨,给出了一种新颖的单用户系统和多用户系统的误码率分析方法。通过高斯近似法和Monte-Carlo模拟方法得到的数值仿真结果表明:瑞利衰落信道下,多载波频率分集CDMA具有良好的抗多径效果:随着用户数的增加,系统性能下降;在无线宽带数据业务传输中的性能大大优于CDMA,应用前景广阔。 相似文献
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差分跳频中,用户数据对频率选择的约束性比较弱。对此本文提出多序列跳频(MSFH)系统,其发送频率不仅是用户数据的函数,也受同步跳频序列严格约束,因此可以采用窄带接收更好地抑制带外干扰。具体地,数据分组从一簇相互正交的跳频序列中选出一个序列,该序列的当前频率由射频端直接发送,而无需对发送信号进行调制。得到了瑞利衰落信道中,未编码和采用卷积编码-硬/软判决Viterbi译码时MSFH符号误码率性能。计算和仿真表明,在相同编码增益下,MSFH误码率低于常规跳频系统;与差分跳频译码复杂度相当时,MSFH性能亦具有一定优势。 相似文献
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SONGLi-xin HUANGTian-shu DINGYao-ming 《半导体光子学与技术》2005,11(2):129-134
Based on the theory of multicarrier (MC) technique and the Rake receiver, a multicarrier DS-CDMA Rake system is proposed, where a data sequence multiplied by a spreading sequence modulates multiple carriers. The receiver provides a Rake for each subcarrier, and the outputs of the Rakes are combined by a maximal-ratio combiner. The average probability of error of the system is derived from an uncorrelated subcarrier and frequency-selective fading channel model. The system performances are evaluated over Rayleigh fading channel with an exponential multipath intensity profile(MIP) and with a rectangular MIP, respectively, when multipath interference is present. It is found that this kind of model has larger superiority in an exponential MIP than in a rectangular MIP. 相似文献
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We present an new method for the analytical calculation of the error probability in a Rayleigh fading channel with correlated fading amplitudes. Even though the method can be applied for more general problems, we restrict ourselves on the investigation of a multicarrier CDMA transmission. The frequency correlation between the fading amplitudes of the carriers is given by the delay power spectrum of the channel. We generalize the well-known analytical expressions for the pairwise error probability of the uncorrelated Rayleigh channel to this case of correlated fading. This probability can be expressed in a closed form by an integral over a finite interval which can be easily evaluated numerically. We present some examples to show how much of the diversity of a code remains useful if the transmission channel does not provide an arbitrary degree of diversity. 相似文献
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Cognitive Radio with Single Carrier TDCS and Multicarrier OFDM Approach with V-BLAST Receiver in Rayleigh Fading Channel 总被引:1,自引:0,他引:1
This article presents the performance comparison of TDCS and OFDM based cognitive radio for MIMO system using VBLAST receiver
architecture to reconstruct the transmitted data. The interference avoidance performance in terms of BER and bitrate are improved
by adding multiple antennas to the system and the use of V-BLAST technique at the receiver. The results show the most promising
interference avoidance technique combined with MIMO V-BLAST architecture to be applied in the CR system.
相似文献
L. P. LigthartEmail: |
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This paper examines the performance of a multicarrier CDMA system in a Rayleigh fading channel without a RAKE receiver. Since the multicarrier technique is a diversity reception technique used in the frequency domain, the signal is transmitted at different frequency bands and undergoes different fading. The superimposed signal of the multipath components after going through the mobile channel will be processed by an Fourier Transform to enter the frequency domain, where the time delays in various paths are converted to the phase shifts in the compound signal. In this paper, we use sounding bits to extract the characteristics of the mobile channel and to partly remove the multipath effect. From the simulation, it is found that the multicarrier technique is simpler than the technique used in the single carrier system with a RAKE receiver while producing a better performance than that of the RAKE receiver. 相似文献
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In this paper, an antenna array based base station receiver structure for multicarrier direct sequence code-division-multiple-access
(Multicarrier DS-CDMA) system with binary phase shift keying (BPSK) modulation is proposed. One of the main advantages of
the receiver structure is that the spatial diversity is obtained by combining signals at different array elements. Based on
the detailed analysis of multiple access interference (MAI) and additive white Gaussian noise (AWGN) characteristics, the
uplink bit error rate (BER) performance of the proposed antenna array Multicarrier DS-CDMA is provided. With regard to spatial
domain combining, the optimum spatial combining (OSC) and suboptimum spatial combination (SOSC) weights is derived while the
suboptimum set of weights is simplified in the sense that only the knowledge of array vector of desired user alone is sufficient
for the combining. Simulation results verify the analysis, and it is shown that MAI is mitigated and subsequently the system
performance is improved significantly by incorporating antenna array at the base station. 相似文献
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Qinghua Zhao Pamela Cosman Laurence B. Milstein 《The Journal of VLSI Signal Processing》2002,30(1-3):7-20
This paper investigates the tradeoffs of source coding, channel coding and spreading in CDMA systems. We consider a system consisting of an image source coder, a convolutional channel coder, an interleaver, and a direct sequence spreading module. With different allocations of bandwidth to source coding, channel coding and spreading, the system is analyzed over a frequency selective Rayleigh fading channel. The performance of the system is evaluated using the cumulative distribution function of peak signal-to-noise ratio. Tradeoffs of different components of the system are determined through simulations. We show that, for a given bandwidth, an optimal allocation of that bandwidth can be found. Tradeoffs among the parameters allow us to tune the system performance to specific requirements. 相似文献