Location-adaptive transmission for indoor visible light communication

A location-adaptive transmission scheme for indoor visible light communication (VLC) system is proposed in this paper. In this scheme, the symbol error rate (SER) of less than 10^-3 should be guaranteed. And the scheme is realized by the variable multilevel pulse-position modulation (MPPM), where the transmitters adaptively adjust the number of time slots n in the MPPM symbol according to the position of the receiver. The purpose of our scheme is to achieve the best data rate in the indoor different locations. The results show that the location-adaptive transmission scheme based on the variable MPPM is superior in the indoor VLC system.     

显微物镜光学传递函数测定

本文介绍了显微物镜光学传递函数测定仪的研制工作,包括仪器的基本工作原理,仪器电路设计、计算机接口设计、软件系统设计。并介绍了仪器的技术性能测试结果,仪器的使用效果。     

基于神经网络的VBR视频流量建模及预测

为解决视频流量预测问题,结合神经网络和小波技术建模IP（Internet Protoc01）网络视频流,提出了利用神经网络预测尺度因子的预测算法。对可变比特率的压缩视频流完成小波分解,得出尺度因子。通过对尺度因子的预测和小波重建,完成视频流量预测。尺度因子的归-化特性简化丁神经网络处理过程。对真实VBR（Variable BitRate）视频流的流量预测实验表明,模型对IP网络普遍应用的高压缩比视频流具有良好的预测能力。     

基于互谱自回归模型的Levinson算法的变换域通信系统抗干扰性能

对互功率谱估计理论及方法进行了深入研究,提出了基于互谱自回归(AR)模型参数估计的Levinson算法,构建数字仿真模型验证互谱Levinson算法的谱估计性能,结果表明:该方法具有良好的谱估计性能。搭建了测量噪声背景下的仿真平台,对基于互谱AR模型参数估计的Levinson算法的变换域通信系统(TDCS)的抗干扰性能进行了研究,仿真结果表明:该方法下TDCS能够保持较强的抗干扰能力,提高了通信质量和频谱资源的利用率。     

第一讲 智能网概述

本文介绍了智能网的概念、基本结构、由来及业务特点     

M2M小数据业务的IEEE 802.11WLAN分析模型

机器对机器(M2M,machine to machine)通信有着巨大的市场潜力,无线局域网(WLAN)作为3G网络的主要补充必将承载大量M2M业务。针对具有时延容忍、耐性重试等特点的典型的M2M小数据业务,提出了一种大时间尺度退避的IEEE 802.11 DCF网络分析模型,推导了MAC层服务时间的概率分布;建立IPP/G/1/K离散时间排队系统模型,研究了非饱和负载下M2M业务在WLAN非理想信道中传输的QoS性能。算法仿真结果表明,大时间尺度退避机制有效提高了系统的吞吐量,降低了系统阻塞率。     

串联排队RED、ERED网络分析模型

基于串联排队网络理论,建立了包括多个网络节点的串联排队RED和ERED分析模型。推导了具有指数分布分组丢失函数的RED算法(ERED)。在概率生成函数域,推导了节点的离去过程,并将其拟合为后续节点的到达过程,从而,刻画了多节点级联拥塞控制的通信场景。通过求解串联排队系统,得出串联排队RED、ERED以及DT 3种AQM机制的网络性能指标,分析了AQM参数设置对其性能的影响。针对不同突发度的业务源,给出每个节点和系统端到端性能指标。     

欠采样噪声分析与光电一体化设计

欠采样噪声产生分布于整个画面的附加像,给目标识别等应用带来困难。基于信息理论,建立了欠采样噪声的应用分析模型,提出了采样成像系统光电一体化设计方法。通过仿真试验,得出欠采样噪声与光学成像系统参数的关系。理论分析和仿真证明,根据系统互信息量选择光、电系统参数,可以减小欠采样噪声,提高图像质量。     

Investigation on random access in a VLC system with multipacket reception in the presence of hidden devices and obstructions

Due to the directionality of light, the hidden device problem and the obstruction cannot be ignored for carrier sense multiple access with collision avoidance (CSMA/CA)-based uplink visible light communication (VLC). In this paper, we introduce multipacket reception (MPR) to handle the hidden device problem in VLC system. We model the traffic of the device with on/off Markov source. With the unsaturated traffic, we formulate a two dimensional (2D) Markov chain to model the CSMA/CA-based slotted random access procedure to evaluate the effects of hidden devices and obstructions on the performance of MPR-aided VLC system, which are mapped into the transition probabilities of the Markov chain. Then, we analyze the throughput and the reception power efficiency (RE) of MPR-aided VLC system with the obstructed optical channel. Numerical results show that the effect is negative when hidden devices or obstructions appear solely. But when they appear simultaneously, they will interact with each other to mitigate the negative effects.