无线光通信副载波系统基于Gamma-Gamma信道的性能研究

首次基于G amm a-G amm a光强闪烁分布大气湍流信道,对采用数字副载波PSK强度调制技术的大气激光通信系统的差错性能进行研究与分析,在不同闪烁强度和接收系统噪声下,对系统的信噪比和比特差错率进行仿真.仿真结果表明,副载波PSK强度调制系统具有较优越的性能,具有实现可靠大气激光通信的潜力.     

副载波多路复用模拟光传输系统中激光器非线性畸变的分析

本文主要分析副载波多路复用模拟光传输系统中激光器的非线性畸变，提出一个激光器非线性失真分析的完整的数学模型，特别考虑了多路副载波情况下激光器的削波影响。认真分析了ＱｕｎＳｈｉ等人的论文，对他们提出的传输系统中ＣＳＯ和ＣＴＢ的计算公式进行了改进，考虑了高阶失真项的影响。理论推导已为实验所得多路光纤ＣＡＴＶ链路中的ＣＳＯ和ＣＴＢ结果所证实。     

微波副载波光纤通信系统特性的PSPICE分析

本文介绍在通用电路分析软件PSPICE中建立激光器件和光电器件的电路模型,模型参数的确定完全依赖于器件的外特性。并利用已建立的器件模型,以微波副载波光纤通信系统为例,对系统的性能特性进行了全面的分析,其分析结果与实验值相吻合。     

毫米波副载波在光无线通信系统中的传输性能

分析了毫米波副载波信号在ROF系统中传输时光纤色散引起的两种效应一幅度衰落和边带脉冲走离,同时模拟了这两种效应对信号性能的影响.理论分析和仿真实验表明边带脉冲的走离限制了信号传输的最大距离,幅度衰落造成了衰落节点信号幅度的减小.理论模型和仿真结果为光载毫米波信号的产生和调制提供了定性和定量分析的基础.     

Optical Single-Sideband Modulators and Their Applications

We review our recent work in the implementation of optical single-sideband (OSSB) modulation and in the application of this modulation format to microwave photonics and optical testing systems. We have developed an enhanced OSSB modulator for wide-band operation, the so-called bidirectional OSSB modulator, and a simplification of this scheme for narrow-band applications. These OSSB modulators are based on the use of a standard single-electrode Mach-Zehnder electro-optic modulator (MZ-EOM) and passive fiber-optic components. In both designs, the OSSB operation is shown to be independent of the MZ-EOM bias. Therefore, the optical modulation depth at the output of the device can be enhanced using minimum transmission biasing to provide suppression of the optical carrier. Finally, we demonstrate the application of OSSB modulators to the improvement of microwave/millimeter-wave subcarrier multiplexing fiber-optic links and to narrow-band fiber radio systems. In addition, we analyzed the feasibility and the limitations of an optical vector network analysis technique based on OSSB modulation that can provide sub-picometer wavelength resolution.     

CO-OFDM系统中一种改进的同步算法方案

对相干光正交频分复用(CO-OFDM)系统时序和频率 同步算法进行了改进,消除了Park的方法中由于时间标尺旁瓣引起 的定时模糊性,利用单个训练符号实现了和Schmidl方法一样宽的频偏估计范围,且保持 同等的估计精 度。在20Gb/s的CO-OFDM系统上对改进算法进行仿真测试的结果表 明,通过色散补偿的辅助,改进的同步 算法方案实现了精确的定时估计,和节省训练符号且宽范围的频差估计。此外,色散补偿的 辅助提升了子载波恢复的性能,使得误比特率(BER)为10－3时系统的光信噪比(OSNR)要求降低了3dB。     

Asymptotically maximum likelihood detection for subcarrier mapping‐induced cyclostationary signatures in cognitive radio networks

In cognitive radio networks based on orthogonal frequency division multiplexing, the subcarrier mapping‐induced cyclostationary signatures are utilized for robust network coordination. However, the effect of network coordination depends on the reliable detection of such cyclostationary signatures. Moreover, doubly selective fading increases the difficulty of reliable detection. In this paper, we first derive an exact covariance matrix to characterize the statistics of the cyclostationary signatures induced by subcarrier mapping. Using the exact covariance matrix rather than its estimation adopted in conventional algorithms, we propose an asymptotically maximum likelihood detection algorithm. The detection performance of the proposed asymptotically maximum likelihood detection algorithm is analyzed and evaluated both in flat fading and doubly selective fading channels. Simulation results show that the proposed algorithm outperforms the conventional low‐complexity single‐cycle signature detection algorithm in terms of less observation period or smaller mapping set size. Copyright © 2011 John Wiley & Sons, Ltd.     

Resource allocation based on genetic algorithm for multi-hop OFDM system with non-regenerative relaying

This article investigates resource allocation in multi-hop orthogonal frequency division multiplexing (OFDM) system with amplifying-and-forwarding relaying to maximize the end-to-end capacity. Most existing methods for multi-hop system focus on power allocation or subcarrier selection separately, but joint resource allocation is rarely considered due to the absence of effective interaction schemes. In this work, a novel joint resource allocation methodology is proposed based on Partheno genetic algorithm (PGA), which produces excellent subcarrier allocation set (referred to as individual in PGA) with higher capacity by evolution operator generation by generation. In addition, an adaptive power allocation is also designed to evaluate the fitness of PGA and further enhance the system capacity. Both theoretical analysis and simulated results show the effectiveness of the proposed joint strategy. It outperforms the traditional method by as much as 40% capacity improvement for 3-hop relaying system when system power is high, and obtains much more capacity enhancement percent under conditions of low system power.     

预留载波法在同轴电缆调制解调系统中的实现

阐述了一种改进的预留载波方法,结合一个基于OFDM技术的同轴电缆调制解调系统给出了其实现结构,并在FPGA上实现了这种方法。     

一种自适应的OFDMA系统下行分组调度算法

提出了一种适合于OFDMA（正交频分多址接入）系统的资源分配与调度算法,该算法利用物理层的信道信息和MAC层的队列状态信息,并综合考虑了数据分组传输的时延要求和业务的优先级,采取资源块与子载波分配相结合的资源分配方式。仿真结果表明,该算法在吞吐量和公平性方面都得到了较好的改善。