汽车电子控制装置的复用通信技术

随着电动机、传感器以及各种电子控制系统在汽车上的应用，汽车线束的总长度也在不断延伸。1960年轿车线束的长度仅为200m，而现在它们的长度几乎翻了一番，总质量也达到了50kg。

基于OFDM载波通信技术的变压器油色谱数据传输方法

由于常规的变压器油色谱数据传输方法未进行编码处理导致传输效果不佳,文章设计一种基于正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)载波通信技术的变压器油色谱数据传输方法。利用色谱分析仪获取数据,进行归一化处理和特征提取,以获取数据的关键信息,并对其进行编码。计算数据的覆盖范围,并根据覆盖情况制定合适的传输协议。在OFDM支持下评估信道质量,根据信道状况分配子载波,动态调整分配结果,计算传输频率,实现高效的数据传输。实验结果表明,该方法误码率低,传输效果较好。

Efficient Timing and Frequency Offset Estimation Scheme for OFDM Systems

A new training symbol weighted by pseudo-noise(PN) sequence is designed and an efficient timing and fre-quency offset estimation scheme for orthogonal frequency division multiplexing(OFDM) systems is proposed. The timing synchronization is accomplished by using the piecewise symmetric conjugate of the primitive training symbol and the good autocorrelation of PN weighted factor. The frequency synchronization is finished by utilizing the training symbol whose PN weighted factor is removed after the timing synchronization. Compared with conventional schemes, the pro-posed scheme can achieve a smaller mean square error and provide a wider frequency acquisition range.

New Passenger Services in Railway Stations Based on Mode Group Diversity Multiplexing Optical Fiber Communications

Nowadays, because of its wide bandwidth and high communication capability, the optical fiber is more and more used for high data rate transmission of information in railway environments. Conventionally, only one service is sent over the fiber at a time. However, many different services can be simultaneously conveyed in railway stations such as passenger information service, cellular phone, Wi-Fi... The objective of the work proposed in this paper is to demonstrate the potential benefits of transmitting radio signals over fiber in a railway environment. The main idea is to exploit the full capacity of the fiber by transmitting multiple services using the same fiber. Since, different services are operating in different frequency bands; we propose a new multiplexing technique called Mode Group Diversity Multiplexing （MGDM） to ensure the transmission of multiple services using the same fiber, without additional infrastructure. There are numerous advantages of the proposed technique, e.g., faster and reliable data exchange, high resolution video surveillance capability, high data rate information exchange in railway stations. We present, in this paper, the physical characteristics of optical fibers, performance of MGDM multiplexing technique, and the influence of the laser excitation conditions at the entrance of the fiber on the performances of the system.

Design of hybrid automatic repeat request (HARQ) for TDD-OFDM system

Reliability-based hybrid automatic repeat request （HARQ） （RB-HARQ） is a recently developed form of incremental-redundancy ARQ. It achieves good performance whereas large retransmission request packets should be fed back. In this paper, in order to reduce the number of the fed back bits, we propose a HARQ scheme applied in time duplex division orthogonal frequency division multiplexing （TDD- OFI）M） system over the slow fading channel which is named channel-based HARQ （CB-HARQ）. Because one bit which meets deep fading is always with small value of log likelihood ratio （LLR） during the process of decoding of LDPC code, the bits transmitted on the carrier with deep fading are retransmitted. At the receiver, the decoder will compute the locations of retransmission bits according to the channel fading values which are gotten by utilizing the feature of channel symmetry in TDD mode. So the indices of retransmission bits are avoided to be transmitted. Simulation results show that this method achieves better BER performance and requires much smaller request packets in feedback link.

Analysis and Research of Multiplexing System

The development of optical transmission was summarized. The multiplexing system was show in detail. The concepts, characteristic, key technology, expand trend and application prospect of frequency division multiplexing, time division multiplexing, code division multiplexing and wave division multiplexing were illustrated.

平场输入/输出蚀刻衍射光栅的设计

光通信中波分复用技术是解决通信网络瓶颈的有效手段 ,近年来得到很大发展。以平面波导波分复用器件为核心的密集波分复用技术已经得到成功商用。蚀刻衍射光栅是平面波导密集波分复用器件中很有发展潜力的一种。原有蚀刻衍射光栅采用罗兰圆设计 ,输入输出在圆弧曲线上由条形波导引出 ;而平场输入 /输出的蚀刻衍射光栅在很多应用中可以省去制作输入输出波导 ,大大简化制作工艺 ,同时能够保持良好的线性色散和聚集效果。给出了平场输入和输出蚀刻衍射光栅的设计方法 ,并利用标量衍射理论对设计的结果进行模拟 ,验证了平场输出蚀刻衍射光栅具有很好的分波效果。