Development of FEC and ESC performance characteristics for IDR carriers greater than 10 Mb/s

The requirement for restoration of high capacity fibre optic cables and the new tariffs approved for INTELSAT digital services has created a requirement to develop performance characteristics for IDR carriers greater than 10 Mb/s. This paper presents the trade-offs used in this development, and estimates the coding gains needed to meet these requirements. A number of FEC schemes are evaluated and a rate 3/4 convolutional code with soft decision Viterbi decoding is selected. Engineering service circuits (ESC) performance characteristics for IDR carriers greater than 10 Mb/s are also presented.     

Exact solutions for nonlinear Schr?dinger equation in phase space: applications to Bose－Einstein condensate

The stationary-state nonlinear Schr?dinger equation, which models the dilute-gas Bose－Einstein condensate, is introduced within the framework of the quantum phase-space representation established by Torres-Vega and Frederick. The exact solutions of equation are obtained in the phase space, by means of the wave-mechanics method. The eigenfunctions in position and momentum spaces are obtained through the ‘Fourier-like' projection transformation from the phase space eigenfunctions. The eigenfunction with a hypersecant part is discussed as an example.     

3G移动通信系统中的新型宽带语音编码VMR-WB

本文介绍了一种将应用于第三代移动通信的新型语音声码器-变速率多模式宽带(VMR-WB)声码器。VMRWB 专为CDMA2000标准设计,有效语音带宽扩展为:50 Hz=7000 Hz,有四种不同速率的运行模式,每一种模式对应一定质量的平均数据速率。在相同的速率下,VMR-WB语音声码器的主观质量和性能较现有的窄带和宽带编码标准都有明显的提高。本文主要介绍其编码原理以及一些特性。     

TURBO TRELLIS CODE MODULATION USING MQAM

The paper presents a kind of reasonable structure for implementing MQAMT-TCM based on the principles of turbo codes and TCM for the first time.It can also be expanded to PSK T-TCM system,and the corresponding decoding algorithm is derived .By computer simulation,its performance is analyzed .The results show that T-TCM takes the advantages of turbo codes and TCM technology,and is a kind of bandwisth-efficient coded-modulation technique obtaining high coding gain .So,in the future,T-TCM would be applied in many fields.     

MRICOM–MRI COntrast Modelling using 2D T1–T2 correlation spectra and relaxation signatures

Image contrast is calculated by inputting experimental 2D T₁–T₂ relaxation spectra into the ODIN software interface. The method involves characterising a magnetic resonance imaging pulse sequence with a “relaxation signature” which describes the sensitivity of the sequence to relaxation and is independent of sample parameters. Maximising (or minimising) the overlap between the experimental 2D T₁–T₂ relaxation spectra and the relaxation signature can then be used to maximise image contrast. The concept is illustrated using relaxation signatures for the echo planar imaging and Turbo spin-echo imaging sequences, together with in-vitro 2D T₁–T₂ spectra for liver and cartilage.     

并行级联分组码的一种新的迭代译码算法

并行级联分组码比串行级联分组码具有更高的码率,基于LLR计算的Turbo迭代译码算法使其内外分量码均做到了软判决译码。通过引入校正因子a（m）,将接收信息与子译码器的输出软信息进行线性叠加反馈能在省去繁琐的LLR计算的情况下实现并行级联分组码的Turbo迭代译码。仿真研究表明,若将译码器的输出进行简单的相关运算,可进一步改善译码器性能。     

极小化互信息的独立分量分析方法应用于多用户检测

论文针对直接序列扩频码分多址（DS-CDMA）通信系统的远近效应,提出了一种将极小化互信息的独立分量分析（MMI—ICA）应用于多用户检测的方法。这种盲多用户检测方法能够有效地抑制远近效应,并能够成功地检测出期望用户信号。仿真结果表明,该算法的抗远近效应能力相对传统的匹配接收机有很大的提高,并能够有效地抑制多址干扰。     

卷积码和Turb0码在甚低频通信系统中的应用研究

甚低频通信具有传播稳定、损耗较小的特点,在对潜通信、远洋通信、导航等方面得到广泛应用。但是在甚低频传播信道中存在传播距离远信号衰减大、大气噪声干扰强烈等问题,这些问题导致了接收机收信误码率比较高,降低了系统整体性能。高性能信道编码的使用可以提高系统整体性能。通过对卷积码和Turbo码的基本原理介绍,并结合甚低频信道特点在MATLAB中设定参数进行仿真,证明了Turbo码在与卷积码复杂度相差不大甚至小于卷积码的情况下,有更好的性能。