2,007 research outputs found
Cross-Layer Adaptive Feedback Scheduling of Wireless Control Systems
There is a trend towards using wireless technologies in networked control
systems. However, the adverse properties of the radio channels make it
difficult to design and implement control systems in wireless environments. To
attack the uncertainty in available communication resources in wireless control
systems closed over WLAN, a cross-layer adaptive feedback scheduling (CLAFS)
scheme is developed, which takes advantage of the co-design of control and
wireless communications. By exploiting cross-layer design, CLAFS adjusts the
sampling periods of control systems at the application layer based on
information about deadline miss ratio and transmission rate from the physical
layer. Within the framework of feedback scheduling, the control performance is
maximized through controlling the deadline miss ratio. Key design parameters of
the feedback scheduler are adapted to dynamic changes in the channel condition.
An event-driven invocation mechanism for the feedback scheduler is also
developed. Simulation results show that the proposed approach is efficient in
dealing with channel capacity variations and noise interference, thus providing
an enabling technology for control over WLAN.Comment: 17 pages, 12 figures; Open Access at
http://www.mdpi.org/sensors/papers/s8074265.pd
Dual protocol performance using WiFi and ZigBee for industrial WLAN
The purpose of this thesis is to study the performance of a WNCS based on utilizing IEEE 802.15.4 and IEEE 802.11 in meeting industrial requirements as well as the extent of improvement on the network level in terms of latency and interference tolerance when using the two different protocols, namely WiFi and ZigBee, in parallel. The study evaluates the optimum performance of WNCS that utilizes only IEEE 802.15.4 protocol (which ZigBee is based on) without modifications as an alternative that is low cost and low power compared to other wireless technologies. The study also evaluates the optimum performance of WNCS that utilizes only the IEEE 802.11 protocol (WiFi) without modifications as a high bit network. OMNeT++ simulations are used to measure the end-to-end delay and packet loss from the sensors to the controller and from the controller to the actuators. It is demonstrated that the measured delay of the proposed WNCS including all types of transmission, encapsulation, de-capsulation, queuing and propagation, meet real-time control network requirements while guaranteeing correct packet reception with no packet loss. Moreover, it is shown that the demonstrated performance of the proposed WNCS operating redundantly on both networks in parallel is significantly superior to a WNCS operating on either a totally wireless ZigBee or WiFi network individually in terms of measured delay and interference tolerance. This proposed WNCS demonstrates the combined advantages of both the IEEE 802.15.4 protocol (which ZigBee is based on) without modifications being low cost and low power compared to other wireless technologies as well the advantages of the IEEE 802.11 protocol (WiFi) being increased bit rate and higher immunity to interference. All results presented in this study were based on a 95% confidence analysis
Simulation of Wireless Networked Control Systems
Embedded systems are becoming increasingly networked and are deployed in application areas that require close interaction with their physical environment. Examples include distributed mobile agents and wireless sensor/actuator networks. The complexity of these applications make co-simulation a necessary tool during system development. This paper presents a simulation environment that facilitates simulation of computer nodes and communication networks interacting with the continuous-time dynamics of the real world. Features of the simulator include interrupt handling, task scheduling, wired and wireless communication, local clocks, dynamic voltage scaling, and battery-driven operation. Two simulation case studies are presented: a simple communication scenario and a mobile robot soccer game
Developing an Efficient DMCIS with Next-Generation Wireless Networks
The impact of extreme events across the globe is extraordinary which
continues to handicap the advancement of the struggling developing societies
and threatens most of the industrialized countries in the globe. Various fields
of Information and Communication Technology have widely been used for efficient
disaster management; but only to a limited extent though, there is a tremendous
potential for increasing efficiency and effectiveness in coping with disasters
with the utilization of emerging wireless network technologies. Early warning,
response to the particular situation and proper recovery are among the main
focuses of an efficient disaster management system today. Considering these
aspects, in this paper we propose a framework for developing an efficient
Disaster Management Communications and Information System (DMCIS) which is
basically benefited by the exploitation of the emerging wireless network
technologies combined with other networking and data processing technologies.Comment: 6 page
A Secure Lightweight Approach of Node Membership Verification in Dense HDSN
In this paper, we consider a particular type of deployment scenario of a
distributed sensor network (DSN), where sensors of different types and
categories are densely deployed in the same target area. In this network, the
sensors are associated with different groups, based on their functional types
and after deployment they collaborate with one another in the same group for
doing any assigned task for that particular group. We term this sort of DSN as
a heterogeneous distributed sensor network (HDSN). Considering this scenario,
we propose a secure membership verification mechanism using one-way accumulator
(OWA) which ensures that, before collaborating for a particular task, any pair
of nodes in the same deployment group can verify each other-s legitimacy of
membership. Our scheme also supports addition and deletion of members (nodes)
in a particular group in the HDSN. Our analysis shows that, the proposed scheme
could work well in conjunction with other security mechanisms for sensor
networks and is very effective to resist any adversary-s attempt to be included
in a legitimate group in the network.Comment: 6 page
Hierarchical fault tolerance in wireless networked control systems
Wireless Networked Control Systems (WNCS) have recently emerged as a replacement for wired control networks. Wireless networked control systems are more suitable for environments that require higher flexibility and robustness. In previous literature a wireless manufacturing line was proposed. The work-cells communication was through IEEE 802.11 technologies and a switched Ethernet backbone. This thesis is aiming to improve the current solution by adding a supervisor to the existing system. The supervisor could be either in passive or active mode. Passive supervisor would intervene when all controllers in the network fail, while active supervisor would act once any controller on the line fail. The system was simulated using OPNET software with 95% confidence analysis. The ability of the system to withstand external interference was assessed through adding a single band jammer to the OPNET simulation. The system was able to hold up to 8KB interfering file sent from a single band jammer affecting the full Wi-Fi spectrum. All results were subjected to a 95% confidence analysis The performability of passive and active supervisor systems was compared. A Markov model of both systems was built. It was shown that by time, the performability of a passive supervisor system is enhanced while that of an active supervisor system degraded. However, the active supervisor showed a better performability in all cases
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