Connection anonymity analysis in coded-WDM PONs

A coded wavelength division multiplexing passive optical network (WDM PON) is presented for fiber to the home (FTTH) systems to protect against eavesdropping. The proposed scheme applies spectral amplitude coding (SAC) with a unipolar maximal-length sequence (M-sequence) code matrix to generate a specific signature address (coding) and to retrieve its matching address codeword (decoding) by exploiting the cyclic properties inherent in array waveguide grating (AWG) routers. In addition to ensuring the confidentiality of user data, the proposed coded-WDM scheme is also a suitable candidate for the physical layer with connection anonymity. Under the assumption that the eavesdropper applies a photo-detection strategy, it is shown that the coded WDM PON outperforms the conventional TDM PON and WDM PON schemes in terms of a higher degree of connection anonymity. Additionally, the proposed scheme allows the system operator to partition the optical network units (ONUs) into appropriate groups so as to achieve a better degree of anonymity.     

基于施工电梯的N∶1无线呼叫系统

针对建筑施工电梯的工作需要，采用先进的编／译码器，研制成一种结构新颖、操作方便、成本低廉的Ｎ∶１无线呼叫通讯系统。文章介绍了系统的功能要求及各组成部分的设计原理。接收系统使用４片ＭＣ１４５０２７，可译出６４个楼层的呼梯信号。由于设计了一种独特的发射互锁环，有效地解决了多个楼层同时呼梯的冲突问题。本系统可用于建筑施工及其它场合。     

一种基于GSM／GPRS的动态信道分配策略

针对GSM／GPRS网络中某些小区因频繁切换导致掉话率高的问题,提出了一种新的动态信道分配策略。该方案将信道划分为数据业务专用信道和语音／数据业务共享信道,并在共享信道中为切换型语音呼叫预留保护信道以降低其呼叫失败率。对于数据业务采用FIFO排队机制。最后利用一种近似计算方法求取该策略的呼叫阻塞率等指标。实验结果表明该方案能有效降低语音呼叫掉话率。     

密集光码分多址系统

基于一种新型光码分多址(OCDMA)的混合(DS/FH)编解码器,提出了多用户公用同一跳频(FH)码字但使用不同的直扩(DS)码字的密集光码分多址系统方案。在忽略噪声的情况下,采用随机过程理论对系统误码率进行了上线分析。分析表明,混合系统适于密集光码分多址通信,从而克服了单一(DS或FH)系统可用码字较少,不能承载多用户的问题。另外,还有效地解决了单一系统中存在的失配和群速度色散等问题。     

Optimal and Suboptimal Access and Transmission Polices for Dynamic Spectrum Access over Fading Channels in Cognitive Radio Networks

We propose a cross-layer optimal access and transmission framework for dynamic spectrum access to maximize expected long-term average throughput under power and collision constraints by a dynamic programming method namely Constrained Markov decision process （CMDP）. The optimal policy for CMDP is capable of guiding transmitter to choose an available channel and transmission rate at the beginning of each frame for its long-term goals according to current channel sensing results and prior channel fading information. The complexity of finding the optimal policy by Linear programming （LP） approach increases exponentially with the number of channels and fading levels, which incurs so-called curse of dimensionality. Therefore we propose two complexity- reduced suboptimal policies, namely, policy separation and heuristic algorithms. Finally, we compare the performances of policies by numerical results.     

Contour-Based Multi-Source Information Fusion for Motion Segmentation

A motion segmentation framework that effectively exploited the multiple sources of image information and fused these sources of the information synergisti-cally was proposed to serve the purpose of motion segmen- tation. A Markov process was formulated for motion seg- mentation in which two feature spaces were established to estimate the state transition Probability density function （PDF） and the initial state, respectively. An information fusion space was developed such that each motion struc-ture was described as a single distribution in this space. The proposed framework can naturally embed the evolution equations of the active contour methods into the seg-mentation to achieve contour-based segmentation results. Extensive empirical evaluations demonstrate the robust-ness and the promise of this framework.     

Service Migration Algorithm Based on Markov Decision Process with Multiple Service Types and Multiple System Factors

This paper proposes a Markov decision process based service migration algorithm to satisfy quality of service(QoS)requirements when the terminals leave the original server.Services were divided into real-time services and non-real-time services,each type of them has different requirements on transmission bandwidth and latency,which were considered in the revenue function.Different values were assigned to the weight coefficients of QoS par-ameters for different service types in the revenue and cost functions so as to distinguish the differences between the two service types.The overall revenue was used for migration decisions,rather than fixed threshold or instant revenue.The Markov decision process was used to maximize the overall revenue of the system.Simulation results show that the proposed algorithm obtained more revenue compared with the existing works.     

Fast handoff with reducing waste rate approach for wireless resources management in UMTS mobile networks

3G Wideband CDMA systems adopt the Orthogonal Variable Spreading Factor code tree as the channelization codes management for achieving high data rate transmission in personal multimedia communications. It assigns a single channelization code for each accepted connection. Nevertheless, it wastes the system capacity when the required rate is not powers of two of the basic rate. One good solution is to assign multiple codes for each accepted connection but it causes two inevitable drawbacks: long handoff delay and new call setup delay due to high complexity of processing with multiple channelization codes, and high cost of using more number of rake combiners. Especially, long handoff delay may result in more call dropping probability and higher Grade of Service, which will degrade significantly the utilization and revenue of the 3G cellular systems. Therefore, we propose herein an adaptive efficient codes determination algorithm based on the Markov Decision Process analysis approach to reduce the waste rate and reassignments significantly while providing fast handoff. Numerical results demonstrate that the proposed approach yields several advantages, including the lowest GOS, the least waste rate, and the least number of reassignments. Meanwhile, the optimal number of rake combiners is also analyzed in this paper. This research was supported in part by the National Science Council of Taiwan, ROC, under contract NSC-93-2213-E-324-018.     

Dynamic wavelength selection and delayed burst assignment schemes for Optical Burst Switching networks

Optical Burst Switching (OBS) has been proposed as a promising switching technology for the next generation of optical transport networks. In this paper, we address the issue of how to provide proportional differentiated services in OBS networks. Firstly, a Dynamic Wavelength Selection (DWS) scheme is introduced to provide proportional differentiated services in bufferless OBS networks by dynamically assigning more and longer periods of wavelengths to high priority classes. This scheme can also utilize wavelengths efficiently because the wavelengths are shared among different classes. Next, a Delayed Burst Assignment (DBA) scheme is introduced, by which bursts of the high priority class are given a higher probability for reserving wavelengths by scheduling the bursts of the low priority class with a delay to provide quality of service (QoS) in OBS networks. The integration of these two schemes provides proportional differentiated services and improves the burst loss performance by giving the burst head packet (BHP) two opportunities of scheduling its data burst (DB).     

嵌入式通信中间件的马尔可夫路由决策与选择

针对嵌入式设备互连环境和嵌入式通信中间件的特点,结合马尔可夫决策过程理论,建立了解决路由问题的有限阶段模型,并修改马尔可夫有限阶段模型的向后递归迭代算法,提出了马尔可夫有限阶段决策路由算法MFHDR(Markov Finite Horizon Decision Routing).该算法具有分布计算和自我学习的特性,从而降低了单台嵌入式设备的工作强度,均衡了各台设备的负载,具有较好的时间和空间复杂度,并且能够有效的避免环路的产生.     

基于马尔可夫决策理论的无人机视情维修策略

视情维修可以根据设备工作状况安排预防性维修措施,是解决退化失效问题、保证设备可用度的有效途径。以无人机核心部件为研究对象,将部件在运行中发生的缓慢劣化过程,划分为若干个性能劣化状态。利用连续时间马尔可夫链理论建立状态维修及更换策略模型。以设备的稳态最大可用度为决策指标,同时考虑相邻两个阶段的平均劣化时间、平均检测时间、平均预防性维修时间以及更换部件时间等因素的影响。根据马氏过程平稳状态下的统计平衡原理,采用递归求解的算法对模型进行求解,最终确定系统最优检测频率、视情维修阈值和更换策略。实验结果表明,该模型能有效描述设备的劣化过程,实现设备维修优化。     

光CDMA编解码器的误差分析

对光CDMA编解码器在的误差及其对系统误码率的影响进行了分析,研究了表明：对于时间编码系统,编解码器的误差都将引起信噪比的损失而导致误率上升;光谱编码系统受误差的影响要比时间编码系统大;光谱编码系统的可容纳用户数比时间编码系统多,误码率也低得多。     

Strategies for Dense Optical CDMA Communication Systems

1　Introduction　Recently, considerable interest has been focused on Opti cal Code Division Multiple Access (OCDMA)[1~15], be cause of the advantages of flexible bandwidth management,asynchronous access, and the potential network scalabilityetc. In an OCDMA system, many users can simultaneouslyshare the same channel through the allocation of specific ad dress codes. All users signals are transmitted by the sameoptical fiber channel. At the receiver end, the matched de coder can re…