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101.
基于三种调制模式下的turbo码光无线通信系统分析 总被引:1,自引:0,他引:1
从分析大气对光无线通信系统的影响出发,研究了大气信道特性,建立了大气信道信噪比和能见度的关系.为降低系统误码率,提出了基于OOK、BPSK、BPPM三种调制模式的turbo码的编码方案,推导出三种不同方案对应的turbo码迭代MAP算法.应用建立的信噪比关系,分析和计算了基于三种不同方案的系统的误码率.结果表明,基于BPSK的turbo码系统比OOK和BPPM系统的信噪比降低约3dB,且在高的信噪比情况下,BPSK系统能显著降低系统的误码率.因此,基于BPSK的turbo码方案较适合光无线通信系统. 相似文献
102.
In this paper we have proposed a novel prime spreading sequence family hereby referred to as “new-Modified Prime Code (n-MPC)”
for direct-detection synchronous optical code-division multiple-access (OCDMA) networks. The new code has been applied to
Overlapping Pulse-Position Modulation (OPPM) CDMA system and the performance of system is evaluated. In addition, we have
analyzed the system throughput and also introduced a new interference cancellation technique which significantly improves
the bit error probability (BEP) of OPPM-OCDMA systems. 相似文献
103.
A novel super-FEC code based on concatenated code for high-speed long-haul optical communication systems 总被引:3,自引:0,他引:3
The structures of the novel super forward error correction (Super-FEC) code type based on the concatenated code for high-speed long-haul optical communication systems are studied in this paper. The Reed-Solomon (RS) (255, 239) + Bose-Chaudhuri-Hocguenghem (BCH) (1023, 963) concatenated code is presented after the characteristics of the concatenated code and the two Super-FEC code type presented in ITU-T G.975.1 have theoretically been analyzed, the simulation result shows that this novel code type, compared with the RS (255, 239) + convolutional-self-orthogonal-code (CSOC) (k0/n0 = 6/7, J = 8) code in ITU-T G.975.1, has a lower redundancy and better error-correction capabilities, and its net coding gain (NCG) at the third iteration is 0.57 dB more than that of RS (255, 239) + CSOC (k0/n0 = 6/7, J = 8) code in ITU-T G.975.1 at the third iteration for the bit error rate (BER) of 10−12. Therefore, the novel code type can better be used in long-haul, larger capacity and higher bit-rate optical communication systems. Furthermore, the design and implementation of the novel concatenated code type are also discussed. 相似文献
104.
Tuvi Etzion 《组合设计杂志》2008,16(2):137-151
A doubly constant weight code is a binary code of length n1 + n2, with constant weight w1 + w2, such that the weight of a codeword in the first n1 coordinates is w1. Such codes have applications in obtaining bounds on the sizes of constant weight codes with given minimum distance. Lower and upper bounds on the sizes of such codes are derived. In particular, we show tight connections between optimal codes and some known designs such as Howell designs, Kirkman squares, orthogonal arrays, Steiner systems, and large sets of Steiner systems. These optimal codes are natural generalization of Steiner systems and they are also called doubly Steiner systems. © 2007 Wiley Periodicals, Inc. J Combin Designs 16: 137–151, 2008 相似文献
105.
106.
在多聚磷酸三甲基硅酯(PPSE)的存在下,2,6-二异丙基苯胺和丁二酸缩合可以高产率地得到N,N',N'-三(2,6-二异丙基苯胺基)-2,5-二亚胺吡咯(1).化合物1经过了元素分析、红外光谱、氢谱、高分辨质谱和单晶结构衍射的表征. 相似文献
107.
108.
Abstract. The trace representation of the dual of quaternary Goethals code δ(m) is given . It isproved that the shortened code of δ(m) is cyclic and its generators are shown. 相似文献
109.
Kuang Tsan Lin 《Optics Communications》2008,281(13):3447-3453
This paper proposes a new type of encoding methods to encrypt hidden (covert) information in host images. The encrypted information can be plot, fax, word, or network data, and it must be encoded with binary codes. All the pixels in an encoded (overt) image modulated from a host image are classified into three groups. The first group of pixels is called identification codes, used to judge whether the overt image is encoded by a method proposed in this paper or not. The second group of pixels is called type codes, used to judge the encoding type. The third group of pixels is called information codes, used to decode the encoded information. Applying the proposed encoding methods is quite convenient, and host images are not needed for decoding. Decoding covert information from overt images is rather difficult for un-authorized persons, whereas it is very easy for designers or authorized persons. Therefore, the proposed methods are very useful. 相似文献
110.
In this paper, we shall prove that there is no [3q4-q3-q2-3q-1,5,3q4-4q3-2q+1]q code over the finite field for q11. Thus, we conclude the nonexistence of a [gq(5,d),5,d]q code for 3q4-4q3-2q+1d3q4-4q3-q. 相似文献