排序方式: 共有65条查询结果,搜索用时 15 毫秒
41.
Turbo码由于其接近香农限的特性而倍受关注,但标准的Turbo码是低码率码,其频带效率低,为了利用Turbo码低误码率的特点,同时又能提高其频带利用率,一个简单的方法是让其与高效率的高阶调制方案M-QAM相结合,本在高斯信道和瑞利平坦衰落信道条件下对数域最大后验概率(log-MAP)解码算法进行了研究和修改,使之适合这2种信道和高阶调制方案,通过采用一种实用方法,使得编、解码系统具有通用性,同时推导出精确计算高斯信道下调制码元对数似然值(LLR)的计算公式,并与近似算法进行了比较,仿真结果表明,在2种信道中,该方案具有很高的编码增益,同时频带效率也得到了提高。 相似文献
42.
为了进一步提高数据的传输速率,采用16进制的正交振幅调制(16QAM)方式,设计实现了一种新颖的基于基片集成波导互连的高速数据传输系统.基片集成波导经设计加工和测试,其带宽为14~28GHz,通带内插损约为0.5dB;16QAM互连系统经先进系统设计(ADS)软件仿真验证,得到了清晰的眼图及星座图,最大传输速率可达到20Gb/s,是传统基片集成波导(SIW)互连系统的数据传输速率的4倍.因此,采用16QAM的SIW高速互连系统与传统的采用载波调制方式的SIW互连系统相比,可显著增加SIW的频带利用率,进而提高系统的数据传输速率. 相似文献
43.
阐述了适用于数字微波系统的全数字正交幅度调制方式与一种全数字频率合成DDS技术,把DDS技术应用于64QAM调制器数控振荡器设计中,并利用FPGA实现了64QAM调制器的各个模块单元,最后在Altera公司的QuartusⅡ5.0软件平台上进行了仿真。 相似文献
44.
提出了基于幅度相位联合校正算法的8阶正交幅度调制(8-QAM)自由空间相干光通信方案。与传统的自由空间光通信方案相比,本文提出的方案不仅无需信道状态信息(CSI)就可以实现对原信号的高精度还原,同时还具有较高的光谱效率。仿真实验表明,当接收端与发射端的频偏f0=20 MHz、激光器联合线宽Δf=10 kHz、信噪比为20 dB时,该方案在归一化大气闪烁标准差σ=0.25、归一化相位噪声方差σ■=0.07的对数正态湍流信道条件下,其误码率(BER)与未采用联合校正算法的8-QAM系统相比低4个量级。 相似文献
45.
In this paper, we analyze the most preferred modulation techniques for CATV transmission system. PSK direct, PSK back to back, QPSK, 16QAM modulation techniques are compared so as to get result for CATV transmission system with most suitable modulation technique in term of jitter, Q-factor, eye diagram. 相似文献
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Le Nguyen Binh 《Optical and Quantum Electronics》2008,40(10):707-732
This paper presents the transmission performances, by simulation, of optical communication systems over 10 spans of dispersion
compensated and optically amplified fiber distance with a bit rate of 100 Gb/s, by employing modulation formats of two amplitude
levels and 8 phase states per amplitude level, the 2R-16-Star QAM constellation under direct and coherent detection with and
without phase estimation. Different ring ratios of the amplitude levels are examined and associate transmission performances
are reported. Optical signal to noise ratio is achieved with 18 dB and 23 dB for back to back and long haul transmission cases
with a dispersion tolerance of ±67 ps/nm at 2 dB power penalty of the eye opening at 100 Gb/s. Monte–Carlo simulation is
also performed and a receiver sensitivity of − 15 dBm is achieved for a BER of 10−5under direct detection after 1100 km of dispersion-compensated and optically amplified transmission. Transmission performances,
bit error rate versus receiver sensitivity, are also confirmed with the use of the eye diagram and associate multiple-peaks
statistical spectral density distribution. For 100 Gb/s 2R-16-Star QAM coherent transmission, an improvement of the receiver
sensitivity of 2.5 dB and 3.5 dB is obtained for coherent detection without phase estimation and respectively. Under coherent
detection with phase estimation, the chromatic dispersion tolerance reaches ±100 ps/nm for a 2 dB eye opening penalty at
100 Gb/s bit rate. Comparative studies of the transmission performances of the Star and Square QAM modulation formats are
also conducted under the fiber linear and nonlinear effects and detection with and without phase estimation. 相似文献
49.
在数字电视前端采用的数字调制方式需要具有良好的带宽效率和功率效率,为了找到具备以上特性的调制方式,对正交振幅调制(QAM)作了理论分析和计算机仿真,并将其与移相键控调制(PSK)作了对比分析,结果表明,住相同的条件下,正交振幅调制的性能优于移相键控调制方式,从而表明正交振幅调制比较适合作为数字电视的调制方式。 相似文献
50.
分析了模拟/数字混合式HFC系统中箝位噪声和高斯噪声的一些特点,以及在此噪声环境下传送接收M-QAM信号的误码性能.提出了计算误码率的公式,给出了仿真结果,证实了误码率对有效光调制指数的限制情况. 相似文献