Communication Network Environment Research Articles

Observability and controllability of systems with limited data rate

Some fundamental properties of observability and controllability are studied for linear discrete-time systems in a bandwidth-limited communication network environment shared by a number of sensors and actuators and a remote controller. The concepts of finite time set-observability and set-controllability are introduced for such systems. Sufficient and necessary conditions on quantisation level for set-observability and set-controllability are derived. Especially, the admissible data rates of the communication network are obtained that are sufficient and necessary for the system to be finite time set-observable or finite time set-controllable. In addition, less conservative sufficient and necessary rates based on quantisation level of system states are given too.

Generation of Facial Interface Media for Network Communication Environment

Generation of Facial Interface Media for Network Communication Environment

Security Functional Components for Building a Secure Network Computing Environment

ABSTRACT It is difficult to define reliable security policy components that should be applied to validate a secure computing environment. The job gets further complicated when one has to deal with multiple policies in single computing environment. This paper demonstrates how we can overcome the difficulties of defining reliable security components by using evaluation criteria. In this paper we use common criteria to derive the security functional components for a multipolicy-based network computing environment. In the verification process, the derived policy components are related to the specific security objectives of the network communication environment. The evidence listed in the case study supports the claims that the proposed network security policy interpretation framework is a complete and cohesive set of requirements.

Simulated courtship interactions elicit neighbour intrusions in the whitethroat, Sylvia communis

Animals often signal in communication network environments that include nonintended receivers that may constitute a risk to the signalling animals. Unpaired male songbirds, which sometimes intrude into neighbouring territories and interrupt courtship, may be an example of nonintended receivers of vocal courtship signals. We investigated this in the whitethroat, using dyads of unmated territorial males. Each dyad consisted of a resident male, who was part of the experimental treatment, and a neighbouring male, whose responses to the treatment stimuli were tested. Each dyad received two playback treatments: a courtship treatment in which the treatment male was induced to court a remotely controlled calling and jumping stuffed female, and a song duel treatment in which playbacks of male song were used to induce the focal male to countersing. The neighbours responded with more song flights to the courtship treatment than to the song duel treatment, perhaps to achieve an overview of the courtship activity or attract the female. Only the courtship treatment resulted in neighbouring intrusions and immediate chasing of the intruder by the treatment male. The males that suffered intrusions did not sing less than those that did not suffer intrusions. Reduced singing therefore may not be able to explain the intrusions. Every intrusion except one occurred after the first courtship vocalization, making it likely that the courtship per se caused the intrusions. This emphasizes the necessity of restricting the transmission range of courtship vocalizations in a network and therefore also explains why the courtship vocalizations of whitethroat males are relatively short ranging.

Implementation of wireless network environments supporting inter access point protocol and dual packet filtering

With advances in wireless technologies, future internetworks will include large numbers of mobile hosts roaming across wireless cells. The goal of this paper is to provide a wireless network communication environment, in which mobile hosts can roam among various access points (wireless cells) and across different subnets. For this purpose, we develop methods to implement and integrate the communication mechanisms of Mobile IP and Inter Access Point Protocol (IAPP). For efficient transmission, we also devise a dual packet filtering technique to filter out unnecessary packet transmission, thereby reducing traffic on wireless networks. Such filtering is especially important because of the limited bandwidth of wireless links. Our work can serve as the reference once IAPP has been approved as standard.

Design of Mobile Emergency Telemedicine System Based on CDMA2000 1X-EVDO

The medical service with a high data rate can be supported in mobile emergency telemedicine system by development of cellular communications networks. In Korea, the commercial service of CDMA2000 1X-EVDO is provided since 2002. In this paper, we designed the system that transfers biological signal and video signal information of patients simultaneously based on this communication network environment. In CDMA2000 1X-EVDO, the maximum backward speed is observed to be 153.6Kbps. Several field tests are performed using commercial CDMA2000 1XEVDO to realize the emergency telemedicine system fitted to feature of CDMA2000 1X-EVDO. With the designed system, we could transmit biological signals and MPEG4 images of spatial resolution 640x480 simultaneously. We set up the system in an ambulance and tested it on the road.

Dependable information infrastructures as complex adaptive systems

AbstractInformation infrastructures, such as the Internet and Computational Grids, have enabled a networked computing and communication environment. Although many organizations depend on network‐centric information operations to support critical missions, existing information infrastructures provide little guarantee of the dependability of network‐centric computing and communication. This paper discusses some problems with the dependability of existing information infrastructures, such as stateless or centralized resource management. A Complex Adaptive Systems approach to dependability of futuristic information infrastructures is then presented with emphasis on the detection of emergent states at the regional and global levels of these infrastructures, and the self‐synchronized control of such infrastructures in response to emergent states. The key concept underlying our control strategy at the regional or global level is that the two attributes of the Complex Adaptive System in a dynamic environment, accessibility to many states and sensitivity to small perturbation, present us with an opportunity to manipulate the system's dynamics. © 2003 Wiley Periodicals, Inc. Syst Eng 6: 225–237, 2003

2542 3 者間身体的バーチャルウェーブコミュニケーションシステム

VirtualWave (VW) is an abstracted avatar in which human head motion is simplified as the rhythmic motion of a wave to clarify an essential interaction and communication. By using 3VWs, the embodies virtual face-to-face communication system is developed for three human interaction analysis by synthesis. The system provides networked virtual communication environment in which three remote talkers can share embodied interaction by observing their interaction of VWs including themselves in the same virtual space. The effectiveness of the system is demonstrated in 7 groups, 3 talkers per group by the sensory evaluation of the remote communication experiment as the roles of a speaker and the other two listeners.

Dynamic reblocking RSA-based multisignatures scheme for computer and communication networks

This investigation utilized dynamic reblocking to enhance the RSA-based multisignatures scheme and solve the moduli clashes problem. In contrast to other RSA-based multisignature schemes, the proposed scheme has fewer modular exponentiations operations, overcomes the signing order problem, and minimizes the keys requirements. Consequently, the proposed scheme is suitable for application to all computer communication network environments.

F-0102 3者間身体的バーチャルコミュニケーションシステムの評価(S31-1 ヒューマンインタフェース(1))(S31 ヒューマンインタフェース)

The embodied virtual face-to-face communication system is developed for three human interaction analysis by synthesis. The system provides networked virtual communication environment in which three remote talkers can share embodied interaction by observing their interaction of Virtual Actors including themselves in the same virtual space. The effectiveness of the system is demonstrated by sensory evaluation.

Performance analysis of a hybrid DS/SFH CDMA system using analytical and measured pico cellular channels

This paper presents the throughput and delay analysis of a packet-switched code division multiple access (CDMA) network based on the hybrid direct sequence (DS)/slow frequency hopping (SFH) spread-spectrum multiple access (SS MA) technique with Q-, B-, and D-PSK modulation using analytical and measured pico cellular channels. The performance of the hybrid DS/SFH, DS, and SFH multiple access techniques have been compared in a pico cellular personal communications network (PCN) environment. Multipath and multiple access interference are considered. The performance is evaluated for a given delay spread and a fixed bandwidth. The effects of forward error correction (FEC) coding and diversity techniques, such as selection diversity and maximal ratio combining on the performance, are also investigated.

A theoretical analysis of the performance of code division multiple access communications over multimode optical fiber channels-part I: transmission and detection

This paper presents results of a theoretical investigation to evaluate the performance of code division multiple access communications over multimode optical fiber channels in an asynchronous, multiuser communication network environment. The system is evaluated using Gold sequences for spectral spreading of the baseband signal from each user employing direct-sequence biphase shift keying and intensity modulation techniques. The transmission channel model employed is a lossless linear system approximation of the field transfer function for the /spl alpha/-profile multimode optical fiber. Due to channel model complexity, a correlation receiver model employing a suboptimal receive filter was used in calculating the peak output signal at the ith receiver. The performance measures for the system, i.e., signal-to-noise ratio and bit error probability for the ith receiver, are derived as functions of channel characteristics, spectral spreading, number of active users, and the hit energy to noise (white) spectral density ratio. >

Delay bounds on a queueing system with consistent priorities

A discrete-time queueing system operating under a two-level, consistent priority service policy is studied. The consistency of the policy guarantees that no low priority customer will be served before a previously (or simultaneously) arrived high priority one. Unlike the well known head of the line priority policy (which is consistent), the considered policy provides for limited service to low priority customers, even in the presence of high priority ones. The proposed policy may be viewed as a consistent version of the straightforward gated/limited service priority policy. It may also be viewed as a compromise between the head of the line priority policy and the straightforward gated/limited priority service policy. The customer service time is assumed to be deterministic and equal to one time unit, which makes the queueing model applicable to a packet communication network environment; potential relevant applications are presented. Based on renewal arguments, the theory of infinite dimensional linear equations and a work-conservation law, a general methodology is developed for the derivation of arbitrarily tight bounds on the induced mean packet delay. >

Packet CDMA versus dynamic TDMA for multiple access in an integrated voice/data PCN

A comparative evaluation of dynamic time-division multiple access (TDMA) and spread-spectrum packet code-division multiple access (CDMA) approaches to multiple access in an integrated voice/data personal communications network (PCN) environment are presented. After briefly outlining a cellular packet-switching architecture for voice/data PCN systems, dynamic TDMA and packet CDMA protocols appropriate for such traffic scenarios are described. Simulation-based network models which have been developed for performance evaluation of these competing access techniques are then outlined. These models are exercised with example integrated voice/data traffic models to obtain comparative system performance measures such as channel utilization, voice blocking probability, and data delay. Operating points based on typical performance constraints such as voice blocking probability 0.01 (for TDMA), voice packet loss rate 10/sup -3/ (for CDMA), and data delay 250 ms are obtained, and results are presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Standards for the evolving ISDNs progress and challenges a road map

Pushed by advances in telecommunications technology and pulled by increased diversification in end user requirements, the need has been created for a uniform customer access and network structure in the public communications network environment. Driven by these trends and accelerated by national and international standardization, Integrated Services Digital Networks (ISDNs) are evolving to provide such a structure.The scope of this paper is to (1) present a brief account of the driving forces for ISDNs, (2) identify the major standards forums and sources of standards information and (3) present a brief account of some key ISDN characteristics, their associated standards and some of the current standards work items and trends. While private ISDNs are being contemplated, this paper considers ISDNs from a public network point of view and, in particular, a North American point of view. The purpose of this paper is to provide a skeletal primer on ISDNs and their standards on to which flesh and blood can be added as acquired by the reader.