Mohammad Alaei

Node Clustering Based on Overlapping FoVs for Wireless Multimedia Sensor Networks

Wireless Multimedia Sensor nodes sense areas that are uncorrelated to the areas covered by radio neighbor sensors. Thus, node clustering for coordinating multimedia sensing and processing cannot be based on classical sensor clustering algo-rithms. This paper presents a clustering mechanism for Wireless Multimedia Sensor Networks based on overlapped Field of View (FoV) areas. Today, for random deployments, dense networks of low cost, low resolution and low power multimedia nodes are preferred than sparse cases of high cost, high resolution and high power nodes. Overlapping FoVs in dense networks causes wasting power of system because of redundant sensing of area. The main aim of the proposed clustering method is energy conservation and prolonging network lifetime. This aim is achiev-ed through coordination of nodes belonging to the same cluster in assigned tasks, avoiding redundant sensing or processing.

A method for clustering and cooperation in wireless multimedia sensor networks.

Wireless multimedia sensor nodes sense areas that are uncorrelated to the areas covered by radio neighbouring sensors. Thus, node clustering for coordinating multimedia sensing and processing cannot be based on classical sensor clustering algorithms. This paper presents a clustering mechanism for Wireless Multimedia Sensor Networks (WMSNs) based on overlapped Field of View (FoV) areas. Overlapping FoVs in dense networks cause the wasting of power due to redundant area sensing. The main aim of the proposed clustering method is energy conservation and network lifetime prolongation. This objective is achieved through coordination of nodes belonging to the same cluster to perform assigned tasks in a cooperative manner avoiding redundant sensing or processing. A paradigm in this concept, a cooperative scheduling scheme for object detection, is presented based on the proposed clustering method.

Real-time multimedia monitoring in large-scale wireless multimedia sensor networks: Research challenges

Wireless Sensor Networks (WSNs) have enjoyed dramatic developments over the last decade. The availability of CMOS cameras and microphones enlarged the scope of WSNs paving the way to the development of Wireless Multimedia Sensor Networks (WMSN). Among the envisaged WMSN applications, Real-time Multimedia Monitoring constitutes one of the most promising. However, the resource requirements of these applications place difficult challenges in terms of network lifetime and scalability. This paper starts by identifying the main characteristics and requirements of Real-time Multimedia Monitoring applications and then highlights key research directions that may help to overcome those challenges.

Priority-Based node selection and scheduling for wireless multimedia sensor networks

A critical aspect of applications with wireless sensor networks is network lifetime. Sensing and communications consume energy particularly in wireless multimedia sensor networks (WMSN) due to huge amount of data generated by the multimedia sensors. Therefore, judicious power management and sensor scheduling can effectively extend network lifetime. In this paper we consider the problem of scheduling multimedia sensor activities to maximize network lifetime. The environment is divided in domains monitored by clusters of multimedia sensor nodes. Network lifetime increment is achieved by cooperation between multimedia sensors in two priority-based ways: Intra-cluster cooperation and Inter-cluster cooperation. We will see that the lifetime of cluster nodes is considerably increased under the proposed node selection and scheduling procedures. As for big clusters, the lifetime even is prolonged to 5.5 times with respect to the ordinary un-cooperative node awakening.

MCM: multi-cluster-membership approach for FoV-based cluster formation in wireless multimedia sensor networks

Clustering techniques are proposed for developing performance of wireless sensor networks from several points of view. Multimedia nodes have different sensing region than scalar sensors that usually sense a circle or polygon regions centred by the node, and thus traditional clustering methods do not satisfy a Wireless Multimedia Sensor Network (WMSN). In this paper, a novel formation algorithm, Multi-Cluster-Membership (MCM), for multimedia node clustering is proposed. The proposed algorithm establishes clusters overlapping each other and the common members of clusters are coordinated to make cooperation among clusters. Therefore, MCM offers not only intra-cluster cooperation but also inter-cluster cooperation through coordinating members and also clusters. This differs from other coordinating ways in the fact that nodes may participate sensing in multiple clusters. We show the enhancement in power conservation efficiency of network resulted from applying MCM with respect the Single-Cluster-Membership (SCM) algorithm.

A cluster-based scheduling for object detection in wireless multimedia sensor networks

Network lifetime is always an important topic in wireless sensor networks. The case of Wireless Multimedia Sensor Networks present additional features such as the fact of transmitting multimedia rich data or the fact of having directional sensing areas. This paper presents a scheduling scheme for clustered nodes according to overlapped Field of View (FoV) regions. This approach schedules nodes applying coordination and collaborations among members of clusters to sense the environment while each cluster covers a specific region defined by the degree of overlapping FoV. The objective of this mechanism is to increase power conservation by avoiding similar sensing and redundant processing. Evaluation shows that the proposed scheduling reduces the average energy consumption and thus improves network lifetime.

An Acoustic-Visual Collaborative Hybrid Architecture for Wireless Multimedia Sensor Networks

Prolongation of the lifetime has become a key challenge in design and implementation of Wireless Multimedia Sensor Networks (WMSNs). The energy consumed in multimedia sensor nodes is much more than in the scalar sensors; a multimedia sensor captures images or acoustic signals containing a huge amount of data while in the scalar sensors a scalar value is measured (e.g., temperature). On the other hand, given the large amount of data generated by the visual nodes, both processing and transmitting image data are quite costly in terms of energy in comparison with other types of sensor networks. Therefore, energy efficiency is a main concern in WMSNs. In this paper an energy efficient collaborative mechanism for monitoring is proposed. The proposed scheme employs a mixed random deployment of acoustic and visual sensor nodes. Acoustic sensors detect and localize the occurred event/object(s) in a duty-cycled manner by sampling the received signals and then trigger the visual sensor nodes covering the objects to monitor them. Hence, visual sensors are warily scheduled to be awakened just for monitoring the object(s) detected in their domain, otherwise they save their energy.

Duo-MAC: Energy and time constrained data delivery MAC protocol in wireless sensor networks

We present Duo-MAC, an asynchronous cascading wake-up scheduled MAC protocol for heterogeneous traffic forwarding in low-power wireless networks. Duo-MAC deals with energy-delay minimization problem and copes with transmission latency encountered by Todays duty-cycled protocols when forwarding heterogeneous traffic types. It switches, according to the energy and delay requirements, between Low Duty cycle (LDC) and High Duty Cycle (HDC) operating modes, and it quietly adjusts the wake-up schedule of a node according to (i) its parents wake-up time and (ii) its estimated load, using an effective real-time signal processing linear traffic estimator. As a second contribution, Duo-MAC, proposes a service differentiation through an improved contention window adaptation algorithm to meet delay requirements of heterogeneous traffic classes. Duo-MACs efficiency stems from balancing between the two traffic award operation modes. Implementation and experimentation of Duo-MAC on a MicaZ mote platform reveals that the protocol outperforms other state-of-the-art MAC protocols from the energy-delay minimization perspective.

HoneyWiN : Novel honeycomb-based wireless NoC architecture in many-core era

Although NoC-based systems with many cores are commercially available, their multi-hop nature has become a bottleneck on scaling performance and energy consumption parameters. Alternatively, hybrid wireless NoC provides a postern by exploiting single-hop express links for long-distance communications. Also, there is a common wisdom that grid-like mesh is the most stable topology in conventional designs. That is why almost all of the emerging architectures had been relying on this topology as well. In this paper, first we challenge the efficiency of the grid-like mesh in emerging systems. Then, we propose HoneyWiN, a hybrid reconfigurable wireless NoC architecture that relies on the honeycomb topology. The simulation results show that on average HoneyWiN saves 17% of energy consumption while increases the network throughput by 10% compared to its wireless mesh counterpart.

Power Management in Sensing Subsystem of Wireless Multimedia Sensor Networks

A wireless sensor network consists of sensor nodes deployed over a geographical area for monitoring physical phenomena like temperature, humidity, vibrations, seismic events, and so on. Typically, a sensor node is a tiny device that includes three basic components: a sensing subsystem for data acquisition from the physical surrounding environment, a processing subsystem for local data processing and storage, and a wireless communication subsystem for data transmission. In addition, a power source supplies the energy needed by the device to perform the programmed task. This power source often consists of a battery with a limited energy budget. In addition, it is usually impossible or inconvenient to recharge the battery, because nodes are deployed in a hostile or unpractical environment. On the other hand, the sensor network should have a lifetime long enough to fulfill the application requirements. Accordingly, energy conservation in nodes and maximization of network lifetime are commonly recognized as a key challenge in the design and implementation of WSNs. Experimental measurements have shown that generally data transmission is very expensive in terms of energy consumption, while data processing consumes significantly less (Raghunathan et al., 2002). The energy cost of transmitting a single bit of information is approximately the same as that needed for processing a thousand operations in a typical sensor node (Pottie & Kaiser, 2000). The energy consumption of the sensing subsystem depends on the specific sensor type. In some cases of scalar sensors, it is negligible with respect to the energy consumed by the processing and, above all, the communication subsystems. In other cases, the energy expenditure for data sensing may be comparable to, or even greater (in the case of multimedia sensing) than the energy needed for data transmission. In general, energy-saving techniques focus on two subsystems: the communication subsystem (i.e., energy management is taken into account in the operations of each single node, as well as in the design of networking protocols), and the sensing subsystem (i.e., techniques are used to reduce the amount or frequency of energy-expensive samples).