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基于光纤光栅编解码和修正素数跳频码的一种光码分多址系统方案研究 总被引:4,自引:3,他引:4
在素数跳频码(PHCs)的基础上,研究了修正素数跳频码(MPHCs)的构造方法和性能,提出了基于光纤布拉格光栅(FBG)编解码实现修正素数跳频码这种二维地址码的光码分多址(OCDMA)系统方案。并通过对素数跳频码和修正素数跳频码这两种码字误码性能的分析,得到以下结论:对于相同的素数P,当系统误码率(BER)B≤10^-9,P≥37时,修正素数跳频码所容纳的最大用户数大于素数跳频码;在光纤布拉格光栅阵列上修正素数跳频码所需要的编码光栅数相对素数跳频码减少(P一1)/2个,从而降低了光纤布拉格光栅阵列的制作难度。 相似文献
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以OCFHC(一次重合跳频码)作为时间扩频序列,OCS(单重合序列)作为波长跳频序列,构造了一种新的二维光正交码OCFHC/OCS。分析OCFHC/OCS的码字性能,得到了码字的互相关均值表达式,并对该码字的误码率进行了仿真比较。仿真结果表明,当码重和任意两个相邻"切普"波长的最小间隔一定时,增加OCFHC/OCS码的跳波长数,不仅可以降低MWOCDMA(多波长光码分多址)系统的误码率,还可以增加码字容量;与OOC(光正交码)/OCS码相比,OCFHC/OCS码的码字性能更优。 相似文献
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本文提出了一种新的频域跳频、时间扩频混合光CDMA编码方案,并提出了其编、解码器结构.这种新的编码方案利用(L,ω,1)-光正交码(OOC)为频域跳频模式,以素数码(Prime Code)为时间扩频模式,我们称之为Prime/OOC 码.该码具有良好的自相关、互相关性能和大的容量,更为重要的是,该混合码的编、解码器可以通过多布喇格光纤光栅来实现.相对于时间扩频码分多址系统的编、解码器,这种编、解码器更简单,容易变址和集成. 相似文献
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本文提出了一种新的频域跳频、时间扩频混合光CDMA编码方案,并提出了其编、解码器结构。这种新的编码方案利用(L,w,1)-光正交码(OOC)为频域跳频模式,以素数码(Prime Code)为时间扩频模式,我们称之为Prine/OOC码。该码具有良好的自相关、互相关性能和大的容量,更为重要的是,该混合码的编、解码器可以通过多布喇格光纤光栅来实现。相对于时间扩频码分多址系统的编、解码器、这种编、解码器更简单,容易变址和集成。 相似文献
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基于二次全等跳频码的跳频光码分多址系统 总被引:2,自引:0,他引:2
从跳频光码分多址(FH-OCDMA)系统的扩频特征出发,推导出具有良好相关性能的扩频码所能达到的最大码容量,再利用二次全等理论为跳频光码分多址系统构造出一种具有最大码容量的扩频码——二次全等跳频码(QCHC),并给出了构造实例。在此基础上,运用光纤布拉格光栅序列作为编解码器设计了一种跳频光码分多址系统的实现方案,并对该系统的性能进行了详细的分析。结果表明,采用二次全等跳频码的跳频光码分多址系统具有设计简单、用户容量大和误码率低等方面的优点。 相似文献
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一种新的二维光正交码及其性能分析 总被引:3,自引:0,他引:3
以光正交码(OOC)作为时间扩频序列,以单重合序列(OCS)作为波长跳频序列,构造了一种新的二维光正交码,即光正交码/单重合序列。与其他二维光正交码相比,光正交码/单重合序列的波长数并不局限于素数或素数幂,可以是任意整数,不仅构造灵活,而且可充分利用多波长光码分多址(MW OCDMA)系统的有效波长数。分析了光正交码/单重合序列码字的自相关和互相关性能,并得到了其互相关均值的具体表达式。最后,针对多波长光码分多址不同的系统参数,对不同参数的光正交码/单重合序列码字性能进行了分析和讨论:1)给定单重合序列参数和光正交码的码重,增加码长将降低光码分多址系统误码率;2)给定光正交码的参数和单重合序列的码长,增加波长数将降低光码分多址系统误码率。 相似文献
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从跳频素数码的构造方法出发,为同步混合直扩/跳频光码分多址(DS/FH-OCDMA)系统构造了一种新的扩频码一同步跳频素数码,并给出了构造方法和构造实例.在此基础上,运用阵列波导光栅作为编解码器设计了一种同步DS/FH-OCDMA系统的实现方案,并对该系统进行了详细的性能分析.结果表明,基于同步跳频素数码的同步Ds/FH-OCDMA系统具有用户容量大和误码率低等方面的优点. 相似文献
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一种新的光CDMA编码方案 总被引:5,自引:0,他引:5
本文以光正交码(OOC)为基础,提出了一种新的光CDMA编码方案。这种新的方案充分利用了已有的成熟的OOC编码技术,可以灵活方便地构造出光正交跳频以及光正交时间/频率组合码。这种新的地址码具有良好的自相关、互相关性能、较大的容量和良好的系统性能,还可以灵活地和现有的光天源器件相匹配。 相似文献
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Hamarsheh M.M.N. Shalaby H.M.H. Abdullah M.K. 《Lightwave Technology, Journal of》2005,23(12):3959-3965
A dynamic optical code division multiple access (DOCDMA) communication system is proposed for high-bandwidth communication systems. An implementation of the system is proposed based on a fast tunable optical filter (TOF) in each encoder and decoder. This technique actively modulates the central wavelength of a TOF according to a functional code at the transmitter during the bit period before the transmission of the data. The system is modeled and analyzed taking into account multiple access interference (MAI), thermal noise, and phase-induced intensity noise (PIIN). The performance of this system is compared to that of a spectral amplitude coding system that uses either a Hadamard code or a modified quadratic congruence (MQC) code. The results show that the proposed DOCDMA system reduces the PIIN effect on the performance of the system and improves the bit error rate (BER) performance at a large number of users. Furthermore, it is found that when the effective power is large enough, the MAI becomes the main factor that limits system performance, whereas when the effective power is relatively low, both thermal noise and PIIN become the main limiting factors with thermal noise having the main influence. 相似文献
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《Optical Fiber Technology》2007,13(2):180-190
The purpose of this study is to investigate the multirate transmission in fiber-optic code-division multiple-access (CDMA) networks. In this article, we propose a variable-length code construction for any existing optical orthogonal code to implement a multirate optical CDMA system (called as the multirate code system). For comparison, a multirate system where the lower-rate user sends each symbol twice is implemented and is called as the repeat code system. The repetition as an error-detection code in an ARQ scheme in the repeat code system is also investigated. Moreover, a parallel approach for the optical CDMA systems, which is proposed by Marić et al., is also compared with other systems proposed in this study. Theoretical analysis shows that the bit error probability of the proposed multirate code system is smaller than other systems, especially when the number of lower-rate users is large. Moreover, if there is at least one lower-rate user in the system, the multirate code system accommodates more users than other systems when the error probability of system is set below 10−9. 相似文献
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This letter presents an efficient method for optical code division multiple access (OCDMA) code acquisition based on unipolar optical orthogonal codes. We propose a two-dwell acquisition procedure and provide closed form expressions to analyze the system?s error probabilities. Our results match the Multiple Shift (MS) algorithm, recently introduced in the literature, and show that our procedure can achieve the same system performance with a lower computational complexity. 相似文献
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Chun-Ping Hsieh Cheng-Yuan Chang Guu-Chang Yang Kwong W.C. 《Communications, IEEE Transactions on》2006,54(7):1190-1194
We propose a modified bipolar-bipolar code for wavelength-time optical code-division multiple access. The new code uses Gold sequences for time spreading, in place of Barker sequences in our previously proposed bipolar-bipolar code. The new code has a cardinality of N+1 times greater than the original code, because there exist N+2 Gold sequences, but only one Barker sequence, for a given code length N. Since the new code is modified from the original code, there is no increase in hardware complexity. The average performance of the new code is analyzed and found very close to that of the original code. In other words, the new code can support greater cardinality without worsening average performance or increasing hardware complexity. 相似文献
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In this paper, a new mechanism of faster routing known as message priority and fast routing (MPFR) mechanism in optical code division multiple access (OCDMA) is proposed for optimization of routing performance and to provide effective data transfer. In this proposed work, we have reduced the size of the header bits which are used in MPFR mechanism. In proposed algorithm, with accordance to packet header, the message size is being increased and priority bit is being added which leads to faster data transfer rate and effective data transfer in OCDMA. The transmitter sent the 2D codes to the MPFR which is then added priority bit. If the cover bit in any codes is enabling then the code is considered to be a priority packet and its superior bit then the code is considered to be routing. A modern novel approach which reduces the overhead for fast data transfer is proposed on name of MPFR. Thus the routing can be faster and the codes to be sent are being priorities and send. Thus the OCDMA can now become much faster to be used in critical areas. MPFR protocol, which prioritizes the code with high priority and also it reduces the header processing time of the codes with increase in message size. The prioritization of the code helped to process the particular code first and then rest of the codes and with increase in message size, help to reduce the transmission and processing time of the packet header. 相似文献
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Detection using a code orthogonalising filter in the reverse link of a multi-carrier code division multiple access (MC-CDMA) system is discussed. In addition, a scheme which can reduce hardware complexity is proposed. Simulation results show that the proposed MC-CDMA system has superiority in performance over an MC-CDMA system under a multi-user environment 相似文献
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In this paper, we introduce a new and advanced algorithm, namely, multiple-shift algorithm for code acquisition in optical code-division multiple access (CDMA) systems using unipolar optical orthogonal codes (OOCs) as signature sequences. We analyze the performance of the newly proposed algorithm and obtain a bound on its performance and show its advantage in reducing the mean time of synchronization when compared with other synchronization methods. The algorithm can be used with many different receiver structures, like active or passive correlator with or without hardlimiter(s). However, in this paper, we only consider the simple active correlator structure for further discussions and analysis. 相似文献
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OCDMA系统二维QPC地址码的设计和性能研究 总被引:3,自引:1,他引:2
通过对光纤信道波长片和时间片的重新组合,提出了一种新的适用于二维OCDMA系统的素数码(2D-QPC)的结构方案;给出了具体的码字设计步骤和过程;运用有限域理论,分析了码字的相关特性.在此基础上,根据"撞击法'研究2D-QPC应用于同步OCDMA系统时的用户容量和误码性能.结果表明:较之一维QPC,2D-QPC的相关特性有了很大的改进,最大自相关旁瓣由1降为0,最大互相关由2降为1;2D-QPC在系统容量上也有很大提高,在相同带宽,传输速率相同的情况下,比一维QPC的系统容量增加p 1倍. 相似文献
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An optical dynamic frequency hopping code division multiple access communication system is proposed. In this system, an electrically controlled tunable optical filter (TOF) is used to encode the modulated broadband light source. The code depends on the function set to the controller. Two-dimensional code, named functional code, is also proposed based of shifted sine function. The function defines the dynamic coding pattern of the central wavelength of the transmitted narrowband optical signal. Thus, the system will allow for an easy reconfiguration of the transmitter without the need for sophisticated encoder. At the receiver, a synchronized TOF with the same function is used as a decoder. The system is modeled and analyzed taking into account the multiple access interference, phase induced intensity noise, and thermal noise. The performance of this system is shown to be better compared with a fast frequency hopping system and a spectral amplitude coding system that uses either a Hadamard code, a modified quadratic congruence code (MQC), or a modified frequency hopping code (MFH). 相似文献