Modular design principles for protocols with an application to thetransport layer

A method for specifying services, specifying protocols, and constructing protocol specifications by stepwise refinement of service specifications is presented. The method is based on assertional reasoning and a refinement relation between state transition systems. The method is demonstrated on the transport layer, which is used by application protocols such as electronic mail, file transfer, remote login, etc. A succession of specifications is constructed, starting from a very abstract transport service and culminating in specific transport protocols comparable to TCP and ISO TP4. Each specification offers both connection management and connection-specific data transfer. It is shown how any connection-independent data transfer protocol can be transformed to offer connection-specific data transfer service     

FTAM联机计费采集技术及应用

介绍了联机计费采集的提出背景,FTAM协议作为交换机联机计费数据采集协议的实现过程,重点阐述了EWSD交换机FTAM联机采集连接方式、OSI协议栈的功能和计费策略,并提出了EWSD联机采集实施中应注意的问题。     

应用层多播协议的多维特性研究

从数据转发策略、服务模型、优化目标、优化技术和容错机制等5个维度综合研究分析了应用层多播领域的主要协议,并针对应用层多播协议设计过程中所需考虑的协议开销、可靠性、拓扑适配性、可伸缩性和优化目标等若干问题给出建议,最后对未来的研究作了展望。     

Fuzzy-associative-memory-based knowledge construction with anapplication to a human-machine interface

A fuzzy knowledge construction method is proposed for application to human-machine interfaces. This paper considers a human movement estimation system to be one of the interfaces. This estimation system transforms human physical movements into qualitative linguistic labels. For example, the degrees of magnitude and speed of the physical movement are represented by qualitative words. It is difficult to construct the transformation knowledge because the relation between the movements and the labels is fuzzy. This paper proposes a method of constructing the knowledge. This proposed method uses a fuzzy associative memory organizing units system and is applied to estimating human sports movements. Experimental results show that the proposed method is suitable for application to human-machine interfaces     

TETRA空中接口第二层协议的分析与实现

TETRA是欧洲电信标准协会制定的全数字集群通信标准，TETRA系统是当今最先进的移动通信系统之一。文章详细分析了TETRA空中接口的第二层及其各子层的通信协议，并简要介绍了第二层协议的软件实现方法。     

Services and protocols of the physical layer

Among the more important new works on the Physical Layer are perhaps the CCITT Draft Recommendation X.211, Physical Layer Service Definition, and the emerging Physical Layer protocols of the ISDN's (Integrated Services Digital Networks). Discussed along with these new developments, which came in time after the definition of the OSI model, are some of the widely used classic older standards and specifications, such as X.21, V.24, and V.54, which do not always fit nicely within the model layers but which deal substantively with the Physical Layer. This paper starts with an overview of Physical Layer documents, continues with-a detailed discussion of architectural service specifications, and concludes with a discussion of related standards.     

Probabilistic testing of OSI protocols

Protocols are large and complex software systems. Complete conformance testing of an implementation against its standard may not be feasible in terms of the resources available. This paper discusses a new approach, the P-method, to the testing of meaningful subsets of communication protocols for an asynchronous model of communication. The approach is based on the probabilistic verification of protocols, which is carried out on the more probable part of the protocol first. The technique can be used for generating probabilistic test sequences for the conformance testing of communication protocols to standards. The proposed method yields meaningful protocol test sequences which test the most probable behaviors of a protocol when the testing of the complete protocol is not feasible. Probabilistic test sequences can be categorized into different classes. The higher the class a probabilistic test sequence is in, the larger the extent of the protocol it covers, and the better is the fault coverage. If the class of a test sequence is high enough, its fault coverage is comparable to the fault coverage of test sequences generated by other methods. Results from a study of the P-method, using alternating bit protocol (ABP) and a subset of NBS TP4 as examples, support the claims above. It can also be shown that if errors are introduced only to the more probable part of the protocol, the fault coverage of P-method is also comparable to other methods     

Technique for designing biorthogonal wavelet filters with anapplication to image compression

A technique for designing new symmetric biorthogonal wavelets from a given symmetric regular filter is presented. The main idea is to find a symmetric complementary filter of a given regular filter such that it has the least mean square (LMS) amplitude deviation from the ideal halfband lowpass filter. New biorthogonal wavelet filter pairs can be obtained via factoring the product of the complementary polynomial and the given binomial. By applying these new symmetric biorthogonal wavelet filters to the compression of some complicated images an improved result in reducing artefacts may be achieved     

OSI session layer: Services and protocols

This paper describes the principles of the Session Layer of Open Systems Interconnection and the current standardization status. The Session Layer provides the means necessary for cooperating Presentation-entities to organize and synchronize their dialogue, and to manage their data exchange. To do this, the Session Layer provides services to establish a session connection between two Presentation-entities, and to support orderly data exchange interactions.     

Services and protocols of the data link layer

Data Link control protocols are among the oldest recognized communication protocols. The protocol provides a well-defined set of rules which govern the interchange of supervisory information and user data over the interconnecting communication link. Such rules are essential to successful and efficient operation. Data Link protocols have evolved continuously from the early free-wheeling protocols, through the widely implemented character-oriented protocols, to the increasingly popular bit-oriented protocols. Data Link protocols play a vital role in the drive toward Open Systems Interconnection (OSI). Constituting Layer 2 of the International Standards Organization (ISO) Reference Model, these procedure and the services that they offer, are directed at assuring successful and reliable transfer of information over point-to-point or multipoint data links. This paper reviews the role of link protocols in the open systems environment. It discusses the objectives and functions of these protocols and delineates the services provided to the higher layers. A review, with examples, of the protocols suitable for use within the framework of OSI is included. The paper concludes with a look at some of the current Data Link issues.     

An engineering basis for statistical lifetime models with anapplication to tribology

The authors propose a method for incorporating engineering information about failure mechanisms into a statistical lifetime model. The central idea is that wear, stress, and strain are more directly related to failure than is component age. With an application to tribology, they use the method to derive a lifetime model which explicitly uses information about wear. The model is contrasted with the more common technique of fitting the parameters of a statistical distribution. A primary benefit of an engineering-based model is its interpretability for connecting lifetime data for similar components used under differing operating conditions, such as during accelerated lifetime testing     

Performance study of link layer and MAC layer protocols to support TCP in 3G CDMA systems

Providing support for TCP with good quality link connection is a key issue for future wireless networks in which Internet access is going to be one of the most important data services. A number of schemes have been proposed in literature to improve the TCP performance over wireless links. In this paper, we study the performance of a particular combination of link layer protocol (e.g., radio link protocol or RLP) and MAC retransmissions to support the TCP connections over third generation (3G) wireless CDMA networks. We specifically investigate two metrics - the packet error rate and the delay provided by RLP and MAC retransmissions - both of which are important for TCP performance. For independent and identically distributed (i.i.d) error channels, we propose an analytical model for RLP performance with MAC retransmission. The segmentation of TCP/IP packets into smaller RLP frames, as well as the RLP buffering process, is modeled using a Markov chain. For correlated fading channels, we introduce an analytical metric called RLP retransmission efficiency. We show that: 1) the RLP frame size has significant impact on the overall 3G system performance, 2) MAC layer retransmissions significantly improve the TCP performance, and 3) the RLP retransmission scheme performs better in highly correlated channels, while other scheme performs better in low correlated channels. Simulation results also confirm these conclusions.     

Two-dimensional equirotational stack subspace fitting with anapplication to uniform rectangular arrays and ESPRIT

A two-dimensional (2-D) multiple invariance technique for computing signal subspaces for uniform rectangular arrays (URAs) of size M×N sensors is introduced. The method is based on a multiple maximum overlap configuration of the sensors in the array with m×n subarrays of (M-m+1)×(N-n+1) sensors each. We exploit the fact that the stacked subspace of the subarray sensor output signals admits a two-level equirotational stack parametrization. We introduce a TLS-type algorithm for estimating the parameters of this equirotational stack subspace model. Based on this method of equirotational stack subspace fitting, the overall array signal subspace can be estimated with a much higher accuracy than with conventional unstructured SVD and TLS techniques. Detailed experiments validate the theoretical results. We propose a variant of 2-D ESPRIT based on equirotational stack subspace fitting. This 2-D equirotational stack ESPRIT (2-D ES-ESPRIT) algorithm clearly outperforms conventional unstructured variants of 2-D ESPRIT. A detailed comparison with 2-D unitary ESPRIT is presented     

Transport layer protocols and architectures for satellite networks

Designing efficient transmission mechanisms for advanced satellite networks is a demanding task, requiring the definition and the implementation of protocols and architectures well suited to this challenging environment. In particular, transport protocols performance over satellite networks is impaired by the characteristics of the satellite radio link, specifically by the long propagation delay and the possible presence of segment losses due to physical channel errors. The level of impact on performance depends upon the link design (type of constellation, link margin, coding and modulation) and operational conditions (link obstructions, terminal mobility, weather conditions, etc.). To address these critical aspects a number of possible solutions have been presented in the literature, ranging from limited modifications of standard protocols (e.g. TCP, transmission control protocol) to completely alternative protocol and network architectures. However, despite the great number of different proposals (or perhaps also because of it), the general framework appears quite fragmented and there is a compelling need of an integration of the research competences and efforts. This is actually the intent of the transport protocols research line within the European SatNEx (Satellite Network of Excellence) project. Stemming from the authors' work on this project, this paper aims to provide the reader with an updated overview of all the possible approaches that can be pursued to overcome the limitations of current transport protocols and architectures, when applied to satellite communications. In the paper the possible solutions are classified in the following categories: optimization of TCP interactions with lower layers, TCP enhancements, performance enhancement proxies (PEP) and delay tolerant networks (DTN). Advantages and disadvantages of the different approaches, as well as their interactions, are investigated and discussed, taking into account performance improvement, complexity, and compliance to the standard semantics. From this analysis, it emerges that DTN architectures could integrate some of the most efficient solutions from the other categories, by inserting them in a new rigorous framework. These innovative architectures therefore may represent a promising solution for solving some of the important problems posed at the transport layer by satellite networks, at least in a medium‐to‐long‐term perspective. Copyright © 2006 John Wiley & Sons, Ltd.     

Survey on recent advances in IoT application layer protocols and machine learning scope for research directions

The Internet of Things (IoT) has been growing over the past few years due to its flexibility and ease of use in real-time applications. The IoT's foremost task is ensuring that there is proper communication among different types of applications and devices, and that the application layer protocols fulfill this necessity. However, as the number of applications grows, it is necessary to modify or enhance the application layer protocols according to specific IoT applications, allowing specific issues to be addressed, such as dynamic adaption to network conditions and interoperability. Recently, several IoT application layer protocols have been enhanced and modified according to application requirements. However, no existing survey articles focus on these protocols. In this article, we survey traditional and recent advances in IoT application layer protocols, as well as relevant real-time applications and their adapted application layer protocols for improving performance. As changing the nature of protocols for each application is unrealistic, machine learning offers means of making protocols intelligent and is able to adapt dynamically. In this context, we focus on providing open challenges to drive IoT application layer protocols in such a direction.     

通信顺序进程的扩充及其在协议形式化技术中的应用

讨论了为进行协议形式化描述而进行的CSP扩充问题。向CSP中引入了可终止进程的概念，并给出了可终止进程的判定方法：针对CSP只能进行同步通信描述的缺陷，提出了用CSP来描述异步通信的手段：最后给出了AB协议的CSP描述，并在此基础上初步讨论了协议规范的正确性及测试用例的生成。     

移动协议网络层切换时延分析

对移动协议网络层切换时延进行了研究。提出合适的网络模型,从理论上分析了各移动协议的路径更新时间,并采用数值仿真的方法对采用微观移动协议和只使用移动IP协议以及采用不同的微观移动协议的情形进行了比较。研究结果表明路径更新时间与所采用的移动协议的路径更新方法相关;采用微观移动协议时的路径更新时间远小于只使用移动IP协议时的情形;在所有的微观移动协议中,MIP-RR协议中使用的路径更新方法性能最佳。     

Information protection in distributed systems with the help of different layer protocols

The problem of secure information transmission over networks in distributed systems is considered. It is shown that protective measures that are used in such systems only on the network layer are insufficient. Analysis of the data packets transmitted between the system components has shown that, in the systems with high requirements for information security, the application-level security protocols should be used. It is shown that the maximum independence of security protocols from the remaining data-transmission protocols should be provided.     

OSGi框架服务层分析及应用

作为OSGi框架中最上面的一层,服务层带来了更多的动态性,并且使用了大众基本了解过的面向服务编程模型,其好处是显而易见的。文中讲解了什么是服务层和服务层对于OSGi框架的意义,此外,还将提出什么时候应该使用服务,什么时候不应该使用。最后将会是OSGi服务层的一些基础,包括如何定义、注册和发现服务。