Reliability evaluation of a communication system considering a multistate model

The methods most often suggested for reliability evaluation of communication systems/flow networks consider two states, namely the good state and the bad state. This paper considers multistate modelling of the network elements. The states which permit a flow less than the maximum assigned capacity are assumed as parallel and mutually exclusive elements in the network. A method is proposed for reliability evaluation of a communication network considering multistate modelling of the network elements. The proposed method has been implemented on a computer and results obtained using the proposed method are compared with the existing methods for the two state model conditions.     

On a stochastic model of a non-Markovian time-dependent queueing system with general intertransition time distribution

This paper studies the stochastic behaviour of a non-Markovian queueing system in continuous and discrete time. The system deals with a non-Markovian type of a departure mechanism, wherein, the intertransition time distribution is general, so that results corresponding to the situation where intertransition times are governed by a particular process could be easily derived.Further, the arrival mechanism dealt with here is Markovian. The analysis of the system leads to Laplace transforms of the probability generating function of the time-dependent queue length distribution in transient and steady-states. Finally, some important particular cases are derived.     

A stochastic geometrical vector model of macro- and megacellular communication channels

This paper describes a physically based stochastic approach that allows to predict the narrowband fading statistics for macro- and megacellular networks operating in urban areas. On one hand, macrocellular channels have been mainly covered in the literature by means of empirical models. On the other hand, megacells are typical of upcoming communication systems, such as broadband wireless access and high-altitude platform-based networks. Generally, the path gain of a wireless fading channel can be statistically characterized by a Ricean distribution, which includes Rayleigh fading as a particular case. The key parameter of the distribution is the K-factor K, defined as the ratio of the dominant component to the scatter contribution. The K-factor is estimated by means of a physical model, conditionally to a set of geometrical parameters, such as the building height, the street width and the base station-to-terminal distance. These parameters are statistically described by analytical distributions. The model is successfully compared with experimental data at 1.6 GHz and typical applications are presented. Finally, because of its physical background, the model performs very well in analyzing polarization (MIMO) multiplexing schemes.     

Performance of anM-ary orthogonal communication system using stationary stochastic signals

This paper considers the performance of a communication system which transmits forTseconds the real part of a sample function of one ofMstationary complex Gaussian processes whose spectral densities are all frequency translations of the functionS_{xi (f). At the receiver white Gaussian noise of one-sided densityN_{0}is added. The center frequencies of the processes are assumed to be sufficiently separated that theMcovariance functions are orthogonal overT. Exponently tight bounds are obtained for the error probability of the maximum likelihood receiver. It is shown that the error probability approaches zero exponentially withTfor all ratesR = (ln M)/Tup toC= int_{-infty}^{infty} [S_{xi (f)/N_{0}] df - int_{- infty}^{infty} ln [1 + S_{xi}(f)/N_{0}] dfwhich is shown to be the channel capacity. Similar results are obtained for the case of stochastic signals with specular components.     

Analysis of a communication system with imperfect repair

This paper is devoted to the modelling and the calculation of dependability measures of a complex communication system with dormant failure modes and imperfect repair. Steady state availability, interval availability and mean time to failure are evaluated with Markov chain technique. Furthermore, a sensitivity analysis is performed to quantify system specificities. Numerical results are provided.     

Theoretical model of optical fiber secure communication system with chaotic multiple-quantum-well lasers

Chaotic synchronization of injected multiple-quantum-well lasers of optical fiber system and a theoretical model of optical fiber chaotic secure communication system are presented by coupling a chaotic multiple-quantum-well laser synchroniza- tion system and a fiber channel. A new chaotic encoding method of chaos phase shift keying On/Off is proposed for optical fiber secure communications. Chaotic synchronization is achieved numerically in long-haul fiber system at wavelength 1.55 μm. The effect of the nonlinear-phase of fiber is analyzed on chaotic signal and synchronization. A sinusoidal signal of 0.2 GHz frequency is simulated numerically with chaos masking in long-haul fiber analog communication at wavelength 1.55 μm while a digital signal of 0.5 Gbit/s bit rate is simulated numerically with c1haos masking and a rate of 0.05 Gbit/s are also simulated numerically with chaos shift keying and chaos phase shift keying On/Off in long-haul fiber digital communica- tions at wavelength 1.55 μm     

面向新一代通信服务的沟通网络系统模型研究

在分析互联网为代表的通信网络系统的服务能力基础上,提出了面向新一代通信服务的STL网络系统模型.该新一代通信系统具有空间域、时间域和语言域3个维度,并由传输、存储、计算3个基本能力组成,在此基础上推导得到通信能力相互转化的原理.通过对已有互联网应用服务的解释,可以看出,STL系统模型对于通信科学和网络技术的发展,具有一定的借鉴作用.     

兼顾照明的可见光MIMO通信系统模型

可见光通信要同时兼顾照明和通信的双重作用,因此需要同时考虑光源布局及通信可靠性问题。为保证国际照明标准,在总LED灯珠不变的情况下,首先对光源布局进行了分析并数值计算了在同样功耗条件下3个及4个阵列布局方式的照度分布及均匀性。其次,为了提高多阵列可见光通信系统有效性及可靠性,将MIMO技术应用于VLC中,采用STBC编码数值计算了多阵列布局方式下系统可靠性。结果表明,在同样功耗条件下,4个阵列的MIMO系统照度均匀性较3个阵列提高了20.9%,当误码率为10-4时,41系统较31系统的误码性能大约可提高2 dB,42与32系统分别较41与31系统误码性能提高了6 dB与5 dB。     

通信网络系统可信性测度模型

针对通信网络的安全性、可控性和可生存性的测度问题,采用连续时间多态有奖马尔可夫方法建立网络模型,定量分析其性能并构建可信性测度模型.提出了系统结构方程方法解决传统状态分析法中的状态爆炸问题.运用通用生成函数方法优化状态转换概率求解步骤,降低计算复杂度.实例仿真实验表明,计算模型正确、可行.     

CYCLOSTATIONARY MODEL IN DS SPREAD SPECTRUM COMMUNICATION SYSTEM

During the past research,Direct Sequence(DS) Spread Spectrum(SS) signal is modeled as stationary in most cases.Cyclostationary model for SS signal is introduced in this letter.Compared with stationary model,cyclostationary model can preserve more information,and its advantages are shown throrgh example.     

室内无线通信系统的路径损耗模型研究

随着移动通信技术的蓬勃发展,室内无线通信也得到了广泛的应用,然而,室内环境的复杂性和多变性,也为室内无线通信技术的发展和普及带来了许多挑战。信号在传输时,要受到反射、绕射、散射、多径传播等多种因素的影响,这给研究无线信道带来很多困难,因此建立路径损耗模对于研究室内通信系统的特性十分必要。无线信道的路径损耗模型包括位置通用模型(像ITU模型,WINNER模型等)和位置专用模型(像d1-d2模型,Supachai Phaiboon模型等),文章将会对这两类模型分别进行分析。     

Optimum stochastic inspection policies for a system with safety device

In this paper we discuss an optimal stochastic inspection policy for systems that consist of a safefy related module which is supervised by a second module. The life time distributions of the modules are arbitrary. A failure of the safety relevant module is determined by the supervising module provided the latter is functioning. Function of the supervising module can be determined only upon inspection. An inspection returns the system into a state as good as new. The system fails if the safety relevant module fails undetected. The optimal inspection policy is searched among stochastic strategies, i.e. strategies that are able to consider different inspection times with various probabilities.     

Blind identifiability of a quadratic stochastic system

Quadratic systems appear in various fields of signal processing, in particular in detection and estimation. In this paper, we establish some conditions to determine the order and identify the coefficients of any discrete and finite extent quadratic system driven by a sequence of independent and identically distributed random variables. The input sequence is assumed unobservable and the conditions are based on some properties of the output cumulant functions up to the third order. Necessary and sufficient conditions ensuring the determination of the order are given. A sufficient condition of uniqueness to recover the parameters is presented. Lastly, some examples are given     

Secure communication with a chaotic system owning logic element

In recent years, various chaotic systems have been introduced in literature to be used in different branches of science. In the field of secure chaotic communication, more complex chaotic systems are proposed, such as high dimensional (4D, 5D), multi-scroll, surface equilibrium point, to enhance communication security level. In this study, a chaotic system owning logic element is used for increasing the level of security of chaotic communication system, which has not been previously implemented for this purpose in the literature. The used chaotic system includes signum functions, maximum function and absolute operation term. Also, there are analog devices and digital device in the electronic circuit of this chaotic system. These properties increase the complexity of the chaotic system and the security level. Sliding mode control method is preferred for the synchronization part of the secure communication. In this regard, numerical analysis and electronic circuit design of the secure chaotic communication system by using the chaotic system owning logic element have been performed successfully.     

Analysis of a new thruway communication system with discreteminimal zones

A mobile communication system for high-speed thruways is currently under consideration in Japan. The system consists of fixed stations installed at regular intervals (2-5 km) along the thruway which are connected to a host computer. Subscribing customers can communicate with the system as they drive through each station's communication zone of minimal type (40-100 m). The authors develop and analyze a stochastic model for this new communication system. The model closely follows the sequence of operations which actually take place according to a communication protocol for handling collisions, and requires no exponential assumptions for the underlying service times. The tradeoff between the total number of stations installed and the probability of successful completion of a task within z km after the initial submission is investigated. Some numerical results are also given for illustrating the tradeoff, with validation via SIMAN simulation     

Reliability of a laser communication system

Reliability function of a laser communication system is found with the help of a probability of error bound. Attention is restricted to the special case when the average photon arrivals at the receiver of the communication system is large. This reliability function is a complicated function and depends on number of parameters such as average number of signal photons, average number of noise photons, information rate and the channel capacity. The system reliability function and the corresponding curves can give the idea of system parameters which may be useful for the implementation of an optimum laser communication system.     

基于非最大纠缠态的受控量子安全直接通信协议

基于非最大纠缠两粒子态,提出一种多方控制的量子安全直接通信协议.通信过程利用decoy光子来检测窃听,保证信道安全.发送方直接将秘密消息编码在不同的两粒子态中,控制方对其中一粒子序列随机的执行一个幺正操作,接收方只有在得到所有控制方的同意之后,才能恢复出发送方的秘密消息.该协议中信道是非最大纠缠信道,不易受噪声的影响;由于两粒子态易制备,该协议现有技术可实现;所有粒子都用于传输秘密消息,量子比特效率较高.     

Channel model for satellite indoor communication,system design

In this paper the development of a channel model for wireless indoor communication, specifically with regard to indoor retransmission of satellite signals and reception by fixed and portable receivers in the L band, is described. The study is confined to the channel model, though it does not include the assessment of particular transmission forms. The theories and approaches used in the model are mainly derived from the field of mobile communication. They are combined to a straightforward chain from large- to small-scale variations yielding information about the several stages of fading. One of the features is the evaluation of the complex field distribution across a local area that can be transformed into a time-varying fading when assuming a moving receiver or a non-stationary environment. © 1998 John Wiley & Sons, Ltd.     

简化振动模型下空间光通信系统误码率分析

在空间光通信系统中,由于卫星振动将对系统的误码率产生影响,在探讨振动对误码率影响问题时,应分析不同振动类型的影响问题.侧重分析了正弦振动,并分别对方波、三角波、锯齿波型振动进行了分析.结果表明,对于正弦振动,当振动持续时间为整周期时,误码率仅为振幅的函数,此时误码率随振幅的增加迅速上升,而与振动频率无关;当振动持续时间为非整周期时,误码率随时间的增加而起伏,误码率的改变越来越小,且趋于仅与振幅有关的常数.其它类型的振动也有类似的结果.     

卫星移动通信系统体系设计及应用模型

为发展我国的卫星移动通信业务,建设我国自己的卫星移动通信系统,针对卫星移动通信的特点,提出了一种卫星移动通信体系架构,从传输模型、通信体制和信令结构几方面时体系进行设计,通信体制使用COPSK调制方式,对功率放大器利用率高,减少用户对星上功率的要求从而增加系统的容量.信令结构使用3层传输模型,划分不同的逻辑信道,对不同的逻辑信道的信号速率,编码方式,编码率,使用频率等进行配置.并针对此系统提出了卫星移动通信的呼叫模型,作为卫星移动通信系统的应用模型,为卫星移动通信系统的实际应用提供参考.