Akramul Azim

Hybrid LEACH: A relay node based low energy adaptive clustering hierarchy for wireless sensor networks

Prolonging the lifetime of a sensor node powered by battery in both homogeneous and heterogeneous wireless sensor networks is a massive challenging area of research now-a-days. To achieve this target many research works including low energy adaptive clustering hierarchy (LEACH) and its variants use clustering techniques to reduce energy spent by keeping most of the nodes in sleeping mode whenever possible. LEACH cannot solve the problem of extending the networks life time due to loosing huge energy of sensor nodes selected as cluster heads for communications. To save energy of cluster heads, relay node based schemes use independent relay nodes as cluster heads. These schemes, however, still suffer from the problems of relay node placement, blind spots and immature death of cluster heads. Addressing the above mentioned problems, this paper proposes a new robust relay node based hybrid LEACH which incorporates the recently developed energy comparison LEACH within the relay nodes based technique so that the network still operates, in absence of relay nodes, as long as even a single node having energy to communicate. The proposed scheme also maintains the efficiency of energy utilization through controlling the size of cluster in a distributed manner for the first time. Simulation results prove the superiority of the proposed scheme over the relay node based scheme with an improvement of 6%-30% extra network lifetime and significant reduction of packet loss during communications.

DTS: Dynamic TDMA scheduling for Networked Control Systems

Networked Control Systems (NCSs) are pervasively applied in modern industry. With increasing functionalities, modern NCSs tend to have dynamic workload by holding a variety of applications via a shared network. To handle workload variations and provide performance guarantees, dynamic network scheduling scheme is highly desired in NCSs. In this paper, we propose a network scheduling scheme, referred to as DTS, that can make on-the-fly decisions to schedule the applications in NCSs. DTS aims at NCSs that use time-triggered network as shared medium and Time division multiple access (TDMA) as network access method. DTS dynamically changes the network accessing sequence of the applications in a way to provide optimal system performance and maintain control stability in NCSs. DTS adopts a decentralized schedule mechanism where each application can make its local schedule decision, enhancing the scalability of NCSs. Simulation results demonstrate the effectiveness of the proposed scheme by improving the network bandwidth and providing better system performance in NCS comparing with the existing time-triggered scheduling schemes.

A dynamic round-time based fixed low energy adaptive clustering hierarchy for wireless sensor networks

Extending the lifetime of energy constrained wireless sensor network is an immense demanding part of research. To attain this goal many research works including low energy adaptive clustering hierarchy (LEACH) and its variants use clustering techniques to reduce energy consumption by dividing the network coverage area into clusters and sending the accumulated information through a representative of each region, known as cluster head. All of these schemes, except fixed LEACH, suffer from the problem of accomplishing huge energy of sensor nodes due to forming repeated cluster at each fixed time interval. Fixed LEACH surmounts the repeated clustering formation problem by forming fixed clusters only once. This scheme, however, still wastes huge energy and incurs loss of information due to premature dead of cluster heads before expiring the fixed round time. The research work in this paper presents a novel dynamic round time based fixed LEACH where round time is determined based on the remaining energy, at the same time special care is taken to avoid the increase of complexity in round time measurement. The proposed scheme, therefore, provides better quality of services by circumventing packet loss periods and lengthens the network life time significantly. Simulation results proved the superior performances of proposed dynamic round time based fixed LEACH compared with the traditional fixed one.

D-RES: Correct transitive distributed service sharing

With the growth of complexity in the embedded domain, the use of distributed systems to support multiple realtime applications has become commonplace. These applications may share processor and network resources, and real-time scheduling policies can guarantee that these applications do not interfere with each others ability to meet their temporal constraints. We believe that these applications should also be able to transparently share services and chains of services, without the coupling that such sharing typically implies. To solve this problem, we propose D-RES, a resource management system that guarantees temporal isolation between service-sharing applications in a distributed system. D-RES transparently tracks which application uses which service, billing the correct application even in case of nested service calls. We implemented D-RES, and demonstrate its ability to isolate service-sharing applications even in case of overload.

Design choices for high-confidence distributed real-time software

Safety-critical distributed real-time systems, such as networked medical devices, must operate according to their specification, because incorrect behaviour can have fatal consequences. A systems design and architecture influences how difficult it is to provide confidence that the system follows the specification. In this work, we summarize and discuss three design choices and the underlying concepts that aim at increasing predictability and analyzability. We investigate mandatory resource reservation to guarantee resource availability, separation of resource consumptions to better manage resource inter-dependency, and enumerative reconfiguration. We use the example of a distributed monitoring system for the human cardiovascular system to substantiate our arguments.

Dynamic service policy-based clustered wireless sensor networks

Energy is one of the main obstacles to deploying wireless sensor networks (WSNs) because tiny sensor nodes cannot accommodate sufficient energy for achieving the desired level of usage. The clustering protocols of wireless sensor network attain the acme popularity among researchers because of effective usage clustering concepts based on locality and the election of a cluster head for each of them. We derive motivation from energy saving clustering schemes and propose an enhancement by saving energy and prolonging the lifetime of a sensor network significantly. The Low Energy Adaptive Clustering Hierarchy (LEACH) achieves popularity for its simplicity and applicability in WSNs. A large number of works exist that modify LEACH to strengthen the applicability of this scheme in practice, but only limited to the cluster set-up phase. In this paper, we observe a major problem that exists in all of the clustering protocols based on LEACH. That is, LEACH and its variants encounter premature death of cluster heads because data transmission time of each cycle of communication is fixed. Our proposed dynamic service policy-based scheme decreases the premature death of cluster heads and packet loss significantly.

Efficient Jammed Area Mapping in Wireless Sensor Networks

Wireless sensor networks (WSN) are vulnerable to different kinds of denial-of-Service attacks. One such common and easy-to-launch attack is physical or link layer jamming, where an adversary emits constant, high-amplitude noises disrupting the communication among nodes. An intelligent solution is to collaboratively map the jammed region and avoiding traffic through the jammed area. Wood propose such a jammed area mapping (J.A.M) protocol. However, the protocol has the problem of broadcast storm inside the jammed area. In this letter, a technique is presented that finds the nodes inside the jammed area without extensive flooding, thus reducing the traffic inside the jammed region substantially, while retaining the basic operation of J.A.M around the boundary. The solution relies on the localization services present in WSN and exploits this prepared knowledge of neighborhood for deducing the entire area from the perimeter. The result is a reliable and low-traffic version of J.A.M protocol. Simulation results show that the overall traffic involved in mapping can be reduced by 20%-25% using this approach.

An Efficient Periodic Resource Supply Model for Workloads with Transient Overloads

Real-time applications have deadline constraints. The system should provision sufficient resources for the application to meet the deadlines, and use supply and demand bound functions to analyze the schedulability of workloads. The concept of the demand bound function describes the upper bound on the resources required by the application, while the supply-bound function specifies the lower bound on the resources supplied to the tasks. If the system provides fewer resources than required, the application will experience an overload. Most work concentrates on designing systems that cannot experience short periods of overloads. This work explores resource provisioning for control applications that can tolerate overloads. It introduces analysis techniques for supply and demand bound functions that specifically consider overloads and delays in a periodic resource model. With this extended model, the work addresses three problems: (1) determine the worst-case delay for a given resource demand and supply under a periodic resource model, (2) find a periodic resource supply for a given workload and worst-case tolerable delay, and (3) for a control system with a given robustness criterion, identify a periodic resource supply with a worst-case delay.

CSS: Conditional State-Based Scheduling for Networked Control Systems

Modern industrial networked control systems(NCSs) tend to be complicated and have dynamic workload by holding a variety of applications via a shared network. The static network scheduling algorithms fit most NCSs due to their deterministic characteristics and timing guarantees, but they cannot handle dynamic workloads for lack of making on the-fly decisions. The conditional state-based scheduling adds the dynamism in the static scheduling algorithms by automata or more explicitly state chart like formalisms with conditional transitions. In this paper, we propose CSS scheme that applies the conditional state-based scheduling to dynamically schedule different applications in the industrial NCSs. CSS aims at the time-triggered network in the NCSs and uses time division multiple access (TDMA) method to let the applications access the network. To enhance the scalability of the NCSs, we design CSS as a decentralized scheme where each application in NCSs has a local scheduler to make its schedule decisions. Appropriate algorithms are applied to ensure the scheduling decisions made by the local schedulers are consistent and the desired system performance can be achieved. Simulation results demonstrate the effectiveness of the proposed scheme compared to the static TDMA used in real-time networks.

Analyzing consensus in multi-mode real-time communication using history information

State consistency in safety-critical distributed systems is mandatory for synchronizing distributed decisions as found in dynamic time division multiple access (TDMA) schedules in the presence of faults. A dynamic TDMA schedule that supports multi-mode communication is sensitive to transient faults because stations can make incorrect local decisions at run time and cause state inconsistency. Faulty decisions are especially undesirable for safety-critical systems with hard real-time constraints. Therefore, real-time communication schedules must have the capability of detecting state inconsistency within a fixed amount of time. In this work, a reliable state consistency checking mechanism is proposed that uses history information for achieving superior goodput in comparison to the well-known controller state (C-State) based CRC approach and the two phase commit (2PC) protocol.