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GLOBECOM '05. IEEE Global Telecommunications Conference, 2005.最新文献

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Set-theoretic DS/CDMA receivers for fading channels by adaptive projected subgradient method 基于自适应投影子梯度法的衰落信道集论DS/CDMA接收机
Pub Date : 2005-12-01 DOI: 10.1109/GLOCOM.2005.1578068
R. Cavalcante, M. Yukawa, I. Yamada
This paper presents a family of multiple access interference (MAI) suppression receivers based on the adaptive projected subgradient method. The proposed scheme can be applied to many different channel models and modulations in a unified manner. Moreover, it is suitable for both blind and nonblind receivers. The adaptive projected subgradient method realizes excellent convergence to a set including an optimal solution with high probability by asymptotically minimizing a sequence of nonnegative convex functions. Simulation results show much better (variable) tradeoff between speed and performance at steady-state as compared to existing techniques
提出了一种基于自适应投影子梯度法的多址干扰抑制接收机。该方案可统一应用于多种不同的信道模型和调制方式。此外,它适用于盲人和非盲人接收器。自适应投影子梯度法通过渐近极小化非负凸函数序列,实现了对包含高概率最优解集的极优收敛。与现有技术相比,仿真结果显示稳态下速度和性能之间更好的(可变)权衡
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引用次数: 12
Fast packet classification using bit compression 使用位压缩快速分组分类
Pub Date : 2005-12-01 DOI: 10.1109/GLOCOM.2005.1577738
Chia-Jen Hsu, Chien Chen, Chun-Yuan Lin
In order to support Internet security, virtual private networks, QoS, etc., Internet routers need to classify incoming packets quickly into flows. A packet classifier uses information contained in the packet header and a predefined rule table in the routers to classify the packets. This paper presents a novel packet classification algorithm, called the bit compression algorithm. Like the previously best known algorithm, bitmap intersection, bit compression is based on the multiple dimensional range lookup approach. Since the bit vectors of the bitmap intersection contain lots of '0' bits, the bit vectors could be compressed. We compress the bit vectors by preserving useful information but removing the redundant '0' bits of the bit vectors. Additionally, the wildcard rules also enable more extensive improvement. Comparing with the bitmap intersection algorithm, the bit compression algorithm reduces the storage complexity in the average-case from thetas (dN2) to thetas (dN-logN), where d denotes the number of dimensions and N represents the number of rules. By exploring the memory hierarchy, we show that bit compression algorithm requires much less memory access than bitmap intersection algorithm on Intel IXP1200 network processor. Since memory access dominates the lookup time, even though extra decompression time is required for bit compression scheme, the bit compression scheme in the average still outperforms bitmap intersection scheme on the classification performance
为了支持互联网安全、虚拟专用网、QoS等,互联网路由器需要将进入的数据包快速分类为流。报文分类器使用报文头中包含的信息和路由器中预定义的规则表对报文进行分类。本文提出了一种新的分组分类算法——位压缩算法。与之前最著名的位图交叉算法一样,位压缩基于多维范围查找方法。由于位图交叉点的位向量包含大量的“0”位,因此位向量可以被压缩。我们通过保留有用的信息来压缩位向量,但去掉位向量中多余的“0”位。此外,通配符规则还支持更广泛的改进。与位图相交算法相比,位压缩算法在平均情况下将存储复杂度从theta (dN2)降低到theta (dN-logN),其中d表示维数,N表示规则数。通过探索内存层次结构,我们发现在Intel IXP1200网络处理器上,位压缩算法比位图交叉算法需要更少的内存访问。由于内存访问占查找时间的主导地位,尽管位压缩方案需要额外的解压时间,但平均而言,位压缩方案在分类性能上仍然优于位图交叉方案
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引用次数: 5
Designs of cell edge routers in the optical cell switching (OCS) network 光单元交换(OCS)网络中单元边缘路由器的设计
Pub Date : 2005-12-01 DOI: 10.1109/GLOCOM.2005.1578022
Shing-Jeh Jiang, H. J. Chao
Optical cell switching (OCS) is a new flexible all-optical switching paradigm. An OCS consists of cell edge routers (CER) and core switches (OCX). The CER is the interface between the electrical domain and the optical domain, while the OCX is the all optical packet switch without opto-electro-optical (OEO) conversion. In our previous research we have proposed a low complexity and highly scalable switch architecture for the OCX with several high performance scheduling algorithms. In this paper, we focus on the design of the CER. To maximize the optical bandwidth utilization and minimize the packet delay within the OCS, most of OCS intelligence and functionalities are build in the CER. To ensure the performance and the quality of the OCS network, we propose two practical and scalable switch architectures and corresponding efficient scheduling algorithms for ingress and egress CERs accordingly. We show by simulations that with the proposed scheduling algorithms both CERs can achieve ~100% throughput. Additionally, the complexity of both scheduling algorithms at two routers is only O(log(N))
光单元交换(OCS)是一种新型的柔性全光交换模式。OCS由cell edge router (CER)和核心交换机(OCX)组成。CER是电域和光域之间的接口,OCX是不进行光电(OEO)转换的全光分组交换机。在我们之前的研究中,我们提出了一种具有几种高性能调度算法的低复杂性和高可扩展性的OCX交换机架构。在本文中,我们重点研究了CER的设计。为了最大限度地提高光带宽利用率和最小化OCS内的分组延迟,OCS的大部分智能和功能都建立在CER中。为了保证OCS网络的性能和质量,我们提出了两种实用且可扩展的交换机架构以及相应的入口和出口cer的高效调度算法。通过仿真表明,采用所提出的调度算法,两个cer都可以达到~100%的吞吐量。另外,两种调度算法在两台路由器上的复杂度仅为O(log(N))。
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引用次数: 0
Relaxed threaded space-time codes 松弛线程空时码
Pub Date : 2005-12-01 DOI: 10.1109/GLOCOM.2005.1578315
M. Janani, Aria Nosratinia
It is well-known that diversity, despite being widely used as a design criterion, may not be enough to ensure good performance of a wireless system, because the diversity factor may "kick in" at unrealistically high values of SNR. This paper proposes a new class of layered space-time codes with a new design criterion that works well in moderate SNR's. Specifically, we propose to relax some of the constraints of threaded algebraic space-time (TAST) codes, leading to a class of codes with better error performance, which we call relaxed threaded space time (RTST) codes. We also propose a modified design criterion, the average union bound (AUB), which ensures good performance at medium SNR. For a 2 times 2 system operating at 6 b/s/Hz, improvements of more than 1.5 dB have been observed
众所周知,尽管分集被广泛用作设计标准,但可能不足以确保无线系统的良好性能,因为分集因子可能会在不切实际的高信噪比值下“发挥作用”。本文提出了一种新的分层空时码,其设计准则在中等信噪比条件下也能很好地工作。具体来说,我们建议放宽线程代数空时码(TAST)的一些约束,从而产生一类具有更好错误性能的码,我们称之为放宽线程空时码(RTST)。我们还提出了一个改进的设计准则,即平均联合界(AUB),以确保在中等信噪比下具有良好的性能。对于以6 b/s/Hz工作的2 × 2系统,已经观察到超过1.5 dB的改进
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引用次数: 2
Analysis of virus and anti-virus spreading dynamics 病毒和反病毒传播动态分析
Pub Date : 2005-12-01 DOI: 10.1109/GLOCOM.2005.1577963
Xi Zhang, D. Saha, Hsiao-Hwa Chen
Viruses spreading over the Internet can cause significant damage and the loss of network security. On the other hand, the anti-virus process also plays an important part affecting the dynamics of the virus spreading. The spreading dynamics of most viruses depend on the underlying network topology. While much research attention has been paid in developing the anti-virus software/tools, the dynamics and propagating model of the virus and anti-virus spreading in the topology-aware networks is neither well understood, nor thoroughly studied. To remedy this deficiency, we model and analyze the spreading characteristics of viruses as coexisting with the anti-virus spreading process in the two-layer small-world topology. Applying the fluid analysis, we derive the analytical solutions to the two-layer model. The simulations experiments confirm the validity of our fluid analyses in characterizing both virus and anti-virus spreading dynamics.
病毒在互联网上的传播会造成严重的损害和网络安全的损失。另一方面,反病毒过程对病毒的传播动态也起着重要作用。大多数病毒的传播动态取决于底层网络拓扑结构。虽然人们对反病毒软件/工具的开发投入了大量的研究,但对拓扑感知网络中病毒和反病毒传播的动力学和传播模型却知之甚少,研究也不够深入。为了弥补这一缺陷,我们在两层小世界拓扑结构中对病毒与反病毒传播过程共存的传播特征进行了建模和分析。应用流体分析方法,导出了双层模型的解析解。模拟实验证实了我们的流体分析在描述病毒和反病毒传播动力学方面的有效性。
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引用次数: 12
Large system capacity of MIMO block channels with least squares linear adaptive receivers 最小二乘线性自适应接收机的MIMO块信道大系统容量
Pub Date : 2005-12-01 DOI: 10.1109/GLOCOM.2005.1577904
Yakun Sun, M. Honig
The performance of a wireless channel with multiple antennas benefits from channel knowledge at the receiver, which is typically unknown a priori. We study the capacity of a block fading multiple-input/multiple-output (MIMO) channel with a linear receiver, which is estimated from a training sequence via a least squares (LS) algorithm. Given a fixed block size, the amount of training overhead plays a key role in balancing the quality of the receiver estimate and the data transmission time. Here we study the optimal training length, which maximizes the large system MIMO capacity, i.e., the number of transmit and receive antennas go to infinity with fixed ratio. In order to obtain a meaningful limit, the training length and packet length also increase in fixed proportion to the number of antennas. We show that the optimal amount of training grows as the square root of the block size, as the block size becomes large. Furthermore, only a slight benefit is obtained from optimizing the allocation of power across training and data symbols. Numerical results show that for a fixed block length, the capacity can be increased somewhat by adding a properly chosen diagonal loading factor to the LS algorithm.
具有多天线的无线信道的性能受益于接收机的信道知识,这通常是先验未知的。本文研究了带线性接收机的块衰落多输入/多输出(MIMO)信道的容量,该信道通过最小二乘(LS)算法从训练序列中估计。在给定固定块大小的情况下,训练开销的多少在平衡接收方估计质量和数据传输时间方面起着关键作用。这里我们研究最优训练长度,使大系统MIMO容量最大化,即发射天线和接收天线的数量以固定的比例趋于无穷大。为了得到一个有意义的极限,训练长度和分组长度也随天线数量的增加而定比例增加。我们表明,当块大小变大时,最佳训练量随着块大小的平方根而增长。此外,通过优化跨训练符号和数据符号的功率分配,只获得了很小的好处。数值结果表明,在块长度固定的情况下,通过适当选择对角加载因子,LS算法的容量可以有所提高。
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引用次数: 6
Joint MIMO channel tracking and symbol detection with EM algorithm and soft decoding 基于EM算法和软解码的MIMO信道跟踪和符号检测
Pub Date : 2005-12-01 DOI: 10.1109/GLOCOM.2005.1578094
Fu-Hsuan Chiu, Sau-Hsuan Wu, C.-C. Jay Kuo
An expectation maximization (EM) algorithm for joint channel tracking and symbol detection in a multi-input multi-output (MIMO) time-varying frequency-selective fading environment is proposed in this research. Based on the recursive EM procedure in conjunction with soft decoding, we develop an iterative algorithm that performs the minimum mean squared error (MMSE) channel estimation and the maximum a posterior (MAP) probability symbol detection jointly. Two soft decoders are examined; namely, the BCJR algorithm and the soft sphere decoder. The performance of the proposed algorithm is evaluated via simulation and compared with that of Kalman filtering with hard decision feedback. It is demonstrated by numerical simulation that the proposed algorithm has robust performance in the presence of a severe channel model mismatch
针对多输入多输出(MIMO)时变选频衰落环境下的联合信道跟踪和符号检测问题,提出了一种期望最大化算法。基于递归电磁过程与软译码相结合,我们开发了一种迭代算法,该算法同时进行最小均方误差(MMSE)信道估计和最大后验(MAP)概率符号检测。研究了两种软解码器;即BCJR算法和软球解码器。通过仿真对该算法的性能进行了评价,并与带有硬决策反馈的卡尔曼滤波进行了比较。数值仿真结果表明,该算法在信道模型严重失配的情况下具有良好的鲁棒性
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引用次数: 3
Blind recursive tracking of carrier frequency offsets in MC-CDMA systems MC-CDMA系统中载波频偏的盲递归跟踪
Pub Date : 2005-12-01 DOI: 10.1109/GLOCOM.2005.1577890
Feng-Tsun Chien, C.-C. Jay Kuo
A blind recursive algorithm to effectively update the carrier frequency offset (CFO) vector in a multicarrier code-division multiple-access (MC-CDMA) system is studied in this research. The recursive relation is developed based on the expectation maximization (EM) algorithm with a quadratic constraint. This new perspective enables the use of linear estimation theory to deal with the blind CFO estimation problem, leading to an analytic CFO estimate in closed-form. The multiple access interference (MAI) is mitigated using the second order statistics of the interference-plus-noise vector, which can also be updated in a recursive manner under the EM formulation. Finally, we verify the effectiveness of the proposed algorithm with computer simulation.
研究了多载波码分多址(MC-CDMA)系统中有效更新载波频偏矢量的盲递归算法。基于二次约束下的期望最大化算法建立递归关系。这一新的视角使得利用线性估计理论来解决财务总监的盲目估计问题,从而得到封闭式的财务总监分析估计。利用干扰加噪声矢量的二阶统计量减轻了多址干扰(MAI),该矢量也可以在EM公式下以递归方式更新。最后,通过计算机仿真验证了算法的有效性。
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引用次数: 0
Analysis of TCP over optical burst-switched networks with burst retransmission 具有突发重传的光突发交换网络TCP协议分析
Pub Date : 2005-12-01 DOI: 10.1109/GLOCOM.2005.1578012
Qiong Zhang, V. Vokkarane, Yuke Wang, J. Jue
Due to the bufferless nature of OBS networks, random burst losses may occur, even at low traffic loads. For optical burst-switched (OBS) networks in which TCP is implemented at a higher layer, these random burst losses may be mistakenly interpreted by the TCP layer as congestion in the network, leading to serious degradation of the TCP performance. In this paper, we reduce random burst losses by a burst retransmission scheme in which the bursts lost due to contention in the OBS network are retransmitted at the OBS layer. The OBS retransmission scheme can then reduce the probability that the TCP layer falsely detects congestion, thereby improving the TCP throughput. We analyze the TCP throughput when OBS networks employ the burst retransmission scheme and develop a simulation model to validate the analytical results. Based on our simulation results, we show that an OBS layer with burst retransmission provides an improvement of up to ten times the TCP throughput over an OBS layer without burst retransmission. This significant improvement is primarily because the TCP layer triggers fewer time-out based retransmissions when the OBS retransmission scheme is used
由于OBS网络的无缓冲特性,即使在低流量负载下也可能发生随机突发损失。对于在较高层实现TCP的OBS网络,这些随机突发损失可能被TCP层错误地解释为网络中的拥塞,从而导致TCP性能严重下降。在本文中,我们通过一种突发重传方案来减少随机突发损失,该方案在OBS网络中由于争用而丢失的突发在OBS层重传。OBS重传方案可以降低TCP层错误检测拥塞的概率,从而提高TCP的吞吐量。我们分析了OBS网络采用突发重传方案时的TCP吞吐量,并建立了仿真模型来验证分析结果。基于我们的仿真结果,我们表明具有突发重传的OBS层比没有突发重传的OBS层提供了高达十倍的TCP吞吐量改进。这种显著的改进主要是因为当使用OBS重传方案时,TCP层触发的基于超时的重传更少
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引用次数: 85
Adaptive frequency correction method for enhanced sensitivity CDMA acquisition 增强灵敏度CDMA采集的自适应频率校正方法
Pub Date : 2005-12-01 DOI: 10.1109/GLOCOM.2005.1577463
A. Schmid, A. Neubauer, C. Günther
Location based services with Galileo/GPS satellite receivers integrated in mobile phones are expected to experience a substantial market growth. Satellite signals are usually received on the earth surface with very low signal energy. Attenuation, shadowing, and multipath fading in urban canyons and moderate indoor environments impose challenging acquisition conditions for the state-of-the-art enhanced sensitivity mobile satellite receivers. Residual frequency deviations between the down-conversion frequency and the received signal frequency due to unknown Doppler frequency shifts significantly reduce the signal acquisition sensitivity of current satellite receivers. This paper shows how the residual frequency deviation can be reduced incrementally towards zero much faster than the CDMA code synchronization be detected with sufficient probability. This paper furthermore derives the probability density functions for the signal detection using the adaptive frequency correction method and illustrates the acquisition sensitivity gain of around 4 dB for different Galileo and GPS satellite receiver configurations.
在移动电话中集成伽利略/GPS卫星接收器的基于位置的服务预计将经历一个可观的市场增长。卫星信号通常在地球表面接收,信号能量很低。衰减、阴影和多径衰落在城市峡谷和中等室内环境中对最先进的增强灵敏度移动卫星接收机的采集条件提出了挑战。未知多普勒频移导致的下变频频率与接收信号频率之间的剩余频率偏差显著降低了当前卫星接收机的信号采集灵敏度。本文展示了如何以足够的概率检测到CDMA码同步时,将剩余频率偏差逐渐减小到零。本文进一步推导了采用自适应频率校正方法进行信号检测的概率密度函数,并举例说明了不同伽利略和GPS卫星接收机配置下的采集灵敏度增益约为4 dB。
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引用次数: 2
期刊
GLOBECOM '05. IEEE Global Telecommunications Conference, 2005.
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