Discrete Event Systems: Models and Applications; Proceedings of an IIASA Conference, Sopron, Hungary, August 3-7, 1987

Work in discrete event systems has just begun. There is a great deal of activity now, and much enthusiasm. There is considerable diversity reflecting differences in the intellectual formation of workers in the field and in the applications that guide their effort. This diversity is manifested in a proliferation of DEM formalisms. Some of the formalisms are essentially different. Some of the "new" formalisms are reinventions of existing formalisms presented in new terms. These "duplications" reveal both the new domains of intended application as well as the difficulty in keeping up with work that is published in journals on computer science, communications, signal processing, automatic control, and mathematical systems theory - to name the main disciplines with active research programs in discrete event systems. The first eight papers deal with models at the logical level, the next four are at the temporal level and the last six are at the stochastic level. Of these eighteen papers, three focus on manufacturing, four on communication networks, one on digital signal processing, the remaining ten papers address methodological issues ranging from simulation to computational complexity of some synthesis problems. The authors have made good efforts to make their contributions self-contained and to provide a representative bibliography. The volume should therefore be both accessible and useful to those who are just getting interested in discrete event systems

SAVCBS 2005 Proceedings: Specification and Verification of Component-Based Systems

This workshop is concerned with how formal (i.e., mathematical) techniques can be or should be used to establish a suitable foundation for the specification and verification of component-based systems. Component-based systems are a growing concern for the software engineering community. Specification and reasoning techniques are urgently needed to permit composition of systems from components. Component-based specification and verification is also vital for scaling advanced verification techniques such as extended static analysis and model checking to the size of real systems. The workshop will consider formalization of both functional and non-functional behavior, such as performance or reliability. This workshop brings together researchers and practitioners in the areas of component-based software and formal methods to address the open problems in modular specification and verification of systems composed from components. We are interested in bridging the gap between principles and practice. The intent of bringing participants together at the workshop is to help form a community-oriented understanding of the relevant research problems and help steer formal methods research in a direction that will address the problems of component-based systems. For example, researchers in formal methods have only recently begun to study principles of object-oriented software specification and verification, but do not yet have a good handle on how inheritance can be exploited in specification and verification. Other issues are also important in the practice of component-based systems, such as concurrency, mechanization and scalability, performance (time and space), reusability, and understandability. The aim is to brainstorm about these and related topics to understand both the problems involved and how formal techniques may be useful in solving them

Advances in parameter estimation, source enumeration, and signal identification for wireless communications

Parameter estimation and signal identification play an important role in modern wireless communication systems. In this thesis, we address different parameter estimation and signal identification problems in conjunction with the Internet of Things (IoT), cognitive radio systems, and high speed mobile communications. The focus of Chapter 2 of this thesis is to develop a new uplink multiple access (MA) scheme for the IoT in order to support ubiquitous massive uplink connectivity for devices with sporadic traffic pattern and short packet size. The proposed uplink MA scheme removes the Media Access Control (MAC) address through the signal identification algorithms which are employed at the gateway. The focus of Chapter 3 of this thesis is to develop different maximum Doppler spread (MDS) estimators in multiple-input multiple-output (MIMO) frequency-selective fading channel. The main idea behind the proposed estimators is to reduce the computational complexity while increasing system capacity. The focus of Chapter 4 and Chapter 5 of this thesis is to develop different antenna enumeration algorithms and signal-to-noise ratio (SNR) estimators in MIMO timevarying fading channels, respectively. The main idea is to develop low-complexity algorithms and estimators which are robust to channel impairments. The focus of Chapter 6 of this thesis is to develop a low-complexity space-time block codes (STBC)s identification algorithms for cognitive radio systems. The goal is to design an algorithm that is robust to time-frequency transmission impairments

Visszaemlékezéseim : 1956-2003

A szerző szakmai pályafutásának története

Propagation channel model between unmanned aerial vehicles for emergency communications

The aim of the thesis is to create a radio propagation channel model for communication between unmanned aerial vehicles (UAVs) during emergency scenarios. The propagation channel model is designed at 2.4 GHz based on ray-tracing simulations performed over the Sendai City terrain, Japan and over the sea. During the post-disaster scenario with the loss of communication infrastructure and loss of power, it is essential to provide a means of communication to the people in the affected area. One of the possible solutions is to provide for a relay link from a functioning base station to the affected area using unmanned aerial vehicles. The relay link is established for every 3 km such that each UAV is circling with a radius of about 100 m over a given area. To establish such relay links, characterization of the radio propagation channel is essential in designing the communication systems. The path loss at the desired frequency, effect of various multipath components occurring based on the terrain, small scale fading, the effect of Doppler shift due to the movement of the UAVs and the delay dispersion are characterized. The excess delay and coherence bandwidth are compared to the guard interval and sub-carrier spacing of IEEE 802.11g/n and 802.16 WiMAX standards. The channel modeling is performed for different altitudes of UAV operation (150 m and 500 m) for both horizontal and vertical polarizations of transmitting and receiving fields. The guard interval of 802.16 WiMAX systems is sufficient to prevent inter-symbol interference for all UAV propagation scenarios. Frequency at fading occurs for each Orthogonal Frequency Division Multiplexing (OFDM) sub-carrier and frequency selective fading occurs over the entire channel bandwidth. In case of 802.11g/n systems, the guard interval is not sufficient for all propagation scenarios and at fading for OFDM sub-carriers occurs at UAV altitudes of 150 m for typical cases. The effect of Doppler shift is detrimental for 802.16 OFDM systems

On the design of application protocols

In the last decades, much effort has been spent on the design and provision of sophisticated communication infrastructures. The development of end-user oriented distributed system applications, leaning on top of these communication infrastructures, so far has attracted little attention. This is regrettable, since communication infrastructures can only become useful and profitable if they can be deployed in the context of a sufficient number of distributed applications.\ud Two important factors determine the success of distributed applications: (1) the provision of high quality application services and protocols at short time scales; and (2) the availability of standards for these services and protocols that can be used for the construction of �open� distributed systems. The achievement of both (1) and (2) can be supported by a suitable design methodology.\ud A design methodology entails a systematic approach to carry out complex designs, and therefore should incorporate proper concepts that enable the effective structuring of such designs. Concepts currently used for the design and structuring of application protocols appear to be inadequate for this purpose. Also a step-wise design approach that would help to master complexity and shorten development times is currently lacking.\ud Standards are necessary since individual users of distributed system applications prefer to be independent on any particular manufacturer or vendor when procuring products, while manufacturers prefer to have maximum implementation freedom when developing such products. An �open� protocol standard defines necessary and sufficient conditions for system parts to interact, such that the system parts can be implemented independently of each other.\ud ISO and ITU-TSS base the development and definition of protocol standards on a �reference model�, called the Reference Model for Open Systems Interconnection (OSIRM). This model comprises a rudimentary form of a design approach and a reference architecture that can be derived with this approach. According to the OSI-RM, the overall application protocol functionality is distributed over three hierarchical protocol layers. Each layer has been assigned a specific functionality, except the highest layer, the Application\ud Layer, which is made responsible for all remaining protocol functions. Because the functionality of the Application Layer is not delimited it cannot, as opposed to the other layers, be covered by a single protocol standard or a fixed set of protocol standards. Several identified sets of Application Layer protocol functions are defined by separate Application Service Elements (ASEs).\ud The appropriateness of the OSI-RM for the development and definition of application protocol standards can be criticized on a number of points:\ud - the reference architecture defined by the OSI-RM is not flexible enough to adequately cope with the diversity of interaction requirements of distributed applications.\ud - some design concepts are not clearly defined, thus prohibiting their effective application to structuring problems;\ud - the relationship between high level application requirements and proposed application protocol solutions is unclear;\ud - the development of application protocol standards generally takes a long time.\ud This thesis aims at the development of a methodology for the design of application protocols, including application protocol standards, and so addresses the problems mentioned above. The following contributions are made to achieve this aim:\ud - design quality criteria are proposed that can be used to guide design decisions and to evaluate designs;\ud - OSI design decisions and design concepts with respect to application protocols are evaluated;\ud - general-purpose, elementary design concepts are proposed;\ud - milestones in the application protocol design process are presented;\ud - behaviour composition and structuring techniques are developed that can be used to represent design results corresponding to the identified milestones;\ud - design methods are proposed to support the correct performance of design steps between milestones;\ud - a flexible reference architecture is proposed.\ud A (potential) result of the design methodology is that layered application protocol hierarchies can be avoided if they are not required by the class of distributed applications that must be supported