共查询到19条相似文献,搜索用时 93 毫秒
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正交频分复用(OFDM)技术存在着高峰值平均功率比(PAPR)的缺点,在光OFDM系统中,由于其调制器、D/A转换器件、功率放大器及光纤本身的非线性,较大PAPR的信号将会产生严重的畸变,从而大大降低系统的有效性.为抑制光OFDM系统中的PAPR,提出了一种基于线性变换和预留子载波技术的光OFDM系统PAPR降低算法.仿真结果表明,该方案不仅有效地降低了峰均功率比,而且对系统误码率的影响较小,能够获得可靠的系统误码率性能. 相似文献
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研究了利用虚拟子载波抑制OFDM系统PAPR及其算法简化的问题.通过对虚拟子载波技术迭代过程进行简化,得到了运算量只是系统子载波数量级的低复杂度迭代算法,减小了算法实现的复杂度.计算机仿真表明,通过增大虚拟子载波数量或迭代次数,可使系统PAPR性能在一定范围内得到明显改善.由于不用传输边带信息,系统具有较强的可靠性和抗干扰能力. 相似文献
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在相干光正交频分复用(CO-OFDM)系统中,较高的峰均功率比会使信号产生严重的畸变,导致系统误码率性能的严重下降,为了抑制CO-OFDM系统的PAPR提出了一种PTS-TR方法。仿真结果表明,该方法与传统TR方法和PTS方法相比,具有很高的稳定性和更小的运算复杂度,对PAPR的抑制性能较好,更适用于CO-OFDM系统。 相似文献
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针对现有预留子载波TR技术对无线OFDM信号峰均比(PAPR)抑制性能效率低,且难以同时兼顾峰均比抑制、误码率(BER)性能损失及带外频谱分量扩展的问题,提出一种联合智能梯度映射主动星座扩展ACE的预留子载波峰均比抑制ACE-TR算法,能以较低的复杂度同时对信号峰均比和接收端误码率性能进行联合优化,并在迭代过程中消除因限幅处理所导致的信号带外频谱分量再生;特别是,由于在优化迭代过程中可以对迭代参数进行自适应调整,能够有效提高算法的适用灵活性。对算法进行了全面深入的理论分析,推导了其可获得的PAPR抑制增益理论界和接收信号误码率性能理论值。理论分析与仿真表明,ACE-TR算法能以更快的收敛速度产生所需的削峰信号,并同时获得优异的峰均比抑制、误码率及带外功率谱性能。 相似文献
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峰均功率比(PAPR)问题是OFDM系统的主要缺陷之一,在光OFDM系统中,由于调制器、D/A转换器、功率放大器和光纤的非线性,高峰均功率比的信号将会产生严重畸变,对系统的性能造成较大的影响。介绍了降低OFDM系统PAPR的主要方法,包括信号预畸变技术、编码技术和概率类技术,并对星座图扩展(ACE)方法和脉冲成形(PS)方法进行了仿真分析,讨论了各自的优缺点及改进的空间。 相似文献
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HD Radio标准中使用的“带内同频( IBOC)”技术在现有FM模拟广播的同频带内实现数字广播,无需打破现有的频率规划,是调频模拟广播数字化的最佳选择。然而模拟信号和数字信号同时通过混合天线发射时产生的耦合损耗非常大,降低数字信号的峰均比是减小损耗的有力措施。在降低峰均比的所有方案中,预留子载波法由于不引起信号的失真而受到广泛的关注,而预留子载波法的核心即是预留子载波位置的选取。基于HD Radio系统提出一种基于度量的预留子载波位置的选取方法,该方法通过一个度量值来衡量每个子载波对时域大幅度采样值的贡献,并选取具有最大的正度量值的子载波作为预留子载波。仿真结果表明,当使用30个预留子载波时,在概率为10-3时,提出的方案至少能带来0.79 dB的PAPR增益。 相似文献
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为降低过采样后峰均比回升对预留载波法峰均比抑制效果的影响,提出了一种改进方法。该方法利用改进的互熵法计算预留载波的位置,获得一个过采样条件下旁瓣值最低的时域核。用时域核对过采样后的正交频分复用(OFDM)符号进行迭代削峰处理。每次迭代中,OFDM符号的幅度峰值被加权且循环移位后的时域核削减到一个预先设定的阈值。仿真结果表明,该方法可有效降低峰均比回升的影响,在总载波数1 024,预留载波数10的条件下,峰均比抑制效果改善了2.1 dB。 相似文献
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正交频分复用(OFDM)具有较高的频谱利用率、良好的抗多径干扰能力,长期以来一直受到广泛的关注。目前,OFDM已经被公认为是下一代移动通信系统的核心技术之一,但其较高的峰值平均功率比(PAPR)却一直是制约OFDM技术发展的问题之一。如何降低OFDM系统的PAPR是目前通信领域的研究热点之一,本文对目前常用的降低PAPR方法进行了综合分析和比较,并讨论了各方法的优缺点。 相似文献
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The high peak-to-average power ration (PAPR) values of optical orthogond frequency division multiplexing (OFDM) signal limit the system nonlinear tolerance (NLT). In this paper, a novel method based on Hadamard precoding is proposed to reduce the peak-to-average power ratio in optical direct detection OFDM system. The proposed scheme is successfully applied to an experimental system of optical direct-detection OFDM signal transmission through fiber. In this experiment, the 2.5 Gbit/s binary phase shift keying (BPSK) optical OFDM signals with Hadamard precoding are generated and transmitted though a single mode fiber. The experimental results show that the proposed scheme can reduce PAPR by almost 1.5 dB. Meantime the received sensitivity is improved by 2 dB with 100 km fiber transmission compared with that of an ordinary optical direct detection OFDM system. 相似文献
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Abbas Ali Sharifi 《光电子快报》2019,15(4):302-305
The high peak-to-average power ratio (PAPR) is one of the main drawbacks in orthogonal frequency division multiplexing (OFDM) communication systems, which also exists in the optical OFDM (O-OFDM) systems. In this letter, a new approach based on the discrete Hartley transform (DHT) post-coding technique is proposed to reduce PAPR of an O-OFDM signal in visible light communication systems. The proposed method is compared with Walsh-Hadamard transform (WHT) and discrete cosine transform (DCT) techniques in terms of PAPR reduction and bit error rate (BER) performance. Experimental results indicate that the proposed DHT post-coding method remarkably reduces the PAPR of an OFDM signal for optical intensity modulated direct detection systems without any corruption in the BER performance. 相似文献
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A new grouped precoding technique based on discrete cosine transform (DCT) is presented for peak to average power ratio (PAPR) reduction of optical intensity modulated/direct detection (IM/DD) orthogonal frequency division multiplexing (OFDM) system. The computational complexity of the scheme is reduced by at least about 15% compared with that of the ordinary DCT precoding scheme when the number of groups is 2. The PAPR with this method can be reduced by about 0.8 dB. Meantime, compared with original OFDM, the bit error rate (BER) performance of system is improved. So the proposed scheme for reducing PAPR is very effective in optical IM/DD OFDM systems. 相似文献
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针对光OFDM系统存在高峰均功率比(PAPR),提出了一种基于离散哈特利变换(DHT)的选择映射抑制算法。采用快速哈特利逆变换(IFHT)代替传统的快速傅立叶逆变换(IFFT)和Hermi t i an对称算法,并结合非对称限幅法产生满足光OFDM系统要求的正、实值信号送入光纤信道。 相似文献
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针对光正交频分复用(O-OFDM)系统中峰值平均功 率比(PAPR)较高的缺点,对PAPR抑制技术的选择性 映射法(SLM) 进行了深入研究。基于低复杂度SLM方案的深入研究,提出了一种改进的次PAP R选择的思 想与低复杂度SLM相结合的PAPR抑制方案。改 进的SLM方案能够成倍降低传统SLM方案的计算复杂 度。仿真分析表明,改进的SLM方案在载波数为256的O-OFDM系统中,计算复杂度能降低50%以上,并 且随着子载波数的增加,其复杂度降低程度更为高效;同时,该改进的SLM方案又能使其PAPR抑制性能优于传统的SLM方案,从而进一步提升了低复杂度SLM 方案的实用价值。 相似文献
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Block coding scheme for reducing PAPR in OFDM systems with large number of subcarriers 总被引:1,自引:0,他引:1
JiangTao ZhuGuangxi ZhengJianbin 《电子科学学刊(英文版)》2004,21(6):482-489
The major drawback in Orthogonal Frequency Division Multiplexing (OFDM) system is due to the high Peak-to-Average Power Ratio (PAPR), so the performance of the system is significantly degraded by the nonlinearity of a High Power Amplifier (HPA) in the transmitter. In order to mitigate distortion, a block coding scheme for reducing PAPR in OFDM systems with large number of subcarriers based on complementary sequences and predistortion is proposed, which is capable of both error correction and PAPR reduction. Computer simulation results show that the proposed scheme significantly improves Bit Error Rate(BER) performance as compared to an uncoded system when an HPA is employed or a coded system without predistortion. 相似文献
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在光正交频分复用系统中,由于光功率放大器、调制器和光纤本身的非线性,高峰均功率比会大大降低系统的性能.为抑制光OFDM系统的PAPR,提出一种新的基于线性变换和自适应压扩技术的方案.仿真结果表明,与传统压扩方法相比,该方法既能更加有效地抑制光OFDM的PAPR,又能够使系统得到更好的误码率性能. 相似文献
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Tao Jiang Yang Yang Yong-Hua Song 《Broadcasting, IEEE Transactions on》2005,51(2):244-248
In this paper, a new nonlinear companding technique, called "exponential companding", is proposed to reduce the high Peak-to-Average Power Ratio (PAPR) of Orthogonal Frequency Division Multiplexing (OFDM) signals. Unlike the /spl mu/-law companding scheme, which enlarges only small signals so that increases the average power, the schemes based on exponential companding technique adjust both large and small signals and can keep the average power at the same level. By transforming the original OFDM signals into uniformly distributed signals (with a specific degree), the exponential companding schemes can effectively reduce PAPR for different modulation formats and sub-carrier sizes. Moreover, many PAPR reduction schemes, such as /spl mu/-law companding scheme, cause spectrum side-lobes generation, but the exponential companding schemes cause less spectrum side-lobes. Computer simulations, which consider a baseband OFDM system with Additive White Gaussian Noise (AWGN) channels and a Solid State Power Amplifier (SSPA), show that the proposed exponential companding schemes can offer better PAPR reduction, Bit Error Rate (BER), and phase error performance than the /spl mu/-law companding scheme. 相似文献