基于分形的多径衰落信道估计

该文研究了多径衰落的分形性质,提出了一种利用分形维数和小波重构来改进最小均方误差方法的新型多径衰落信道估计算法。该算法改进了衰落信道参数估计的准确度,并消除了判决方法的错误传递性。仿真结果表明该算法能较准确地估计出多径衰落信道的参数,显著提高快衰落条件下接收机的误码性能。     

Turbo码及其在第3代移动通信中的应用

文章在介绍级联码、迭代译码算法以及软判决的基础上,系统阐述了Turbo码的基本概念、关键技术及其在现代移动通信系统中的应用。     

采用QPSK调制的导频辅助CDMA系统的分析和优化

该文分析了有导频辅助的采用QPSK调制方式的直扩(DS-CDMA)系统,计算出由于信道估测的不精确而造成的系统性能的损失,并由此得到了数据信道功率和导频信道功率的最佳比及相应的系统误码率。最后给出仿真结果。     

OFDM系统中一种新的信道估计方法

在OFDM系统中,传统的基于导频的信道估计算法(如梳妆滤波器)都有一个共同的缺点,就是需要大量的导频符号,降低了系统的频谱效率。本文主要致力于研究新的信道估计算法,明确提出了将多径信道的时延估计和幅度估计分开的信道估计方案。对于时延估计,采用周期性插入块状导频估计时延。对于幅度估计,提出了一种全新的动态导频方式来估计多径的幅度,并在数学上证明了这种方法可以节省大量导频。仿真结果表明,本文提出的新算法和传统信道估计算法相比,可以节约至少百分之七十的导频,并且具有性能好,复杂度低的优点。     

多信道应答机信道增益的附加余量

本文指出了多信道应答机信道实际增益的影响因素，提出了多信道应签机信道增益的附加余量，为今后改进应答机信道设计方法提供了某些参考。     

Drain current thermal noise modeling for deep submicron n- and p-channel MOSFETs

The drain current thermal noise has been measured and modeled for the short-channel devices fabricated with a standard 0.18 μm CMOS technology. We have derived a physics-based drain current thermal noise model for short-channel MOSFETs, which takes into account the velocity saturation effect and the carrier heating effect in gradual channel region. As a result, it is found that the well-known Q_inv/L²––formula, previously derived for long-channel, remains valid for even short-channel. The model excellently explained the carefully measured drain thermal noise for the entire V_GS and V_DS bias regions, not only in the n-channel, but also in the p-channel MOSFETs. Large excess noise, which was reported earlier in some other groups, was not observed in both the n-channel and the p-channel devices.     

Time-Varying and Frequency-Selective Channel Estimation with Unequally Spaced Pilot Symbols

In this paper, an accurate and computationally efficient algorithm is proposed for estimating time-varying and frequency-selective fading channel with unequally spaced pilot symbols. By employing the time-varying coefficient polynomial interpolation method, it is proved that the time-varying channel impulse response can be estimated by the product of a constant matrix and the fading information at pilot symbol positions. Furthermore, a least square off-line training algorithm is presented to optimally calculate the constant matrix, taking into consideration of the statistics of channel fading and noise. The new algorithm can also be applied for estimating flat fading channel with equally spaced pilot symbols as a special case. Simulation results indicate that our new channel estimation algorithm leads to small mean square error for fading estimation and provides bit error rate performance close to that of the perfect channel estimation.     

CDMA无线系统中的寻呼信道负荷与短消息承载之间的关系探讨

从寻呼信道的负荷计算和短信业务在寻呼信道上发送机制两个方面来阐述信道负荷与短信业务发送之间的关系;并以石家庄系统为例计算寻呼信道负荷,分析了短消息在寻呼信道上的发送算法。     

一种结合自适应信道估计的差分TC-OFDM系统

本文结合正交频分复用(OFDM)、格形编码调制(TCM)与差分编码,提出一种使用子信道交织技术的差分TC—OFDM系统,并在此基础上将信道估计引入系统接收机,提出了与解码相联合的SEWRLS自适应信道估计方法。计算机仿真结果表明,本文提出的联合系统能有效地克服宽带无线通信中的多径衰落,并在快衰落环境中具有很强的抗信道干扰能力。     

BM-VF-SBD:一种支持QoS的光突发交换数据信道调度算法

在光突发交换(OBS)网络中,数据信道的调度算法是一个关键问题。然而,当前的调度算法大多只强调带宽利用效率,而忽略了QoS支持。该文提出了一个算法BM-VF-SBD,其基本思想为：若所有信道上没有一个Void能容纳新突发,则搬移一些突发到别的信道后,再为新突发分配信道资源;若还失败,则再选择性地丢弃一些低优先级的突发,重复前面操作,它是利用BM,VF和SBD 3种机制减少带宽碎片,支持QoS。若以平衡二叉树组织Void和突发相关信息,它的计算复杂度与LAUC-VF和ODBR接近,小于O((2w+1)log w)。仿真表明它在带宽碎片率和突发损失率(包括总的和各个优先级的)上优于LAUC-VF和ODBR。