Daichi Kominami

Performance evaluation of intermittent receiver-driven data transmission on wireless sensor networks

An intermittent transmission control in the MAC layer protocol is very important for managing the energy consumption of wireless sensor networks. This research focuses on an intermittent receiver-driven data transmission (IRDT) protocol in which communication starts when multiple receiver nodes transmit their own IDs intermittently and a sender node receives them. This method aims at prolonging network life time under the conditions that data-generating frequency is comparatively small. In this paper, we clarify the performance characteristics of this method by comparing it with the low power listing (LPL) method, which is a sender-driven protocol. By simulation, we show that IRDT can result in a higher reduction of energy consumption than LPL, especially at small loads. We also propose an improved IRDT scheme. While all nodes have equal and constant intermittent intervals in the original IRDT, the improved IRDT changes each nodes intermittent intervals adaptively. This achieves more than 98% packet collection ratio and 50% lower power consumption than adaptive LPL, which also sets the intermittent interval adaptively.

Controlled and self-organized routing for large-scale wireless sensor networks

Improving the scalability and robustness of wireless sensor networks is an important task, and much research on self-organization has been conducted toward this end. However, desired behavior is not yet guaranteed in much larger networks based on pure self-organization. In this article, we propose a controlled potential-based routing protocol implementing a novel controlled self-organization scheme that also allows for external control. The scheme obtains close-to-optimal network behavior by this external control which controls a part of nodes in the network. We show that global traffic flow can be controlled through simulation experiments with a multi-sink sensor network. For example, traffic loads can be equalized among heterogeneously distributed sink nodes, and load balancing among the relay nodes based on remaining energy can bring an approximate four times extension of network lifetime. The proposed method is furthermore robust to message loss and resilient to failure of the sink node.

Energy-Efficient Receiver-Driven Wireless Mesh Sensor Networks

A major challenge in wireless sensor networks research is energy efficiency. In the intermittent receiver-driven data transmission (IRDT) protocol, which aims at saving energy, communication between two nodes commences when multiple receiver nodes transmit their own IDs and the sender nodes receive them. This protocol can be used to construct a mesh network which is robust against node failure and wireless channel fluctuations. In our work, we improve this protocol by implementing a collision avoidance method for control packets. First, we refer to the probability of control packet collision as a function of the intermittent interval. We then introduce procedures to determine the interval which decreases or minimizes this probability. Afterwards, we include a data aggregation mechanism into IRDT to reduce data transmission frequency and the occurrence of control packet collisions. Through computer simulation, we show that IRDT can offer greater reduction of the average energy consumption compared with RI-MAC and X-MAC, especially at small loads, and we also demonstrate that IRDT with collision avoidance for control packets can attain higher performance than the original IRDT. This method ensures a packet collection ratio of more than 99% and an average energy consumption 38% lower than that of EA-ALPL and 90% lower than that of the original IRDT.

Controlled potential-based routing for large-scale wireless sensor networks

Improving the scalability of wireless sensor networks is an important task, and toward this end, much research on self-organization has been conducted. However, the problem remains that much larger networks based on pure self-organization cannot be guaranteed to behave as desired. In this paper, we propose a controlled potential-based routing protocol. This protocol is based on a novel concept: a controlled self-organization scheme, which is a self-organization scheme accompanied by control from outside the system. This scheme ensures desired network behavior by controlling a portion of nodes operated in self-organization. Through simulation experiments with a multi-sink network, we show that traffic loads can be equalized among heterogeneously distributed sink nodes, and moreover, that load balancing among the relay nodes can bring about a 138% extension of network lifetime.

Controlling Large-Scale Self-Organized Networks with Lightweight Cost for Fast Adaptation to Changing Environments

Self-organization has potential for high scalability, adaptability, flexibility, and robustness, which are vital features for realizing future networks. Convergence of self-organizing control, however, is slow in some practical applications compared to control with conventional deterministic systems using global information. It is therefore important to facilitate convergence of self-organizing controls. In controlled self-organization, which introduces an external controller into self-organizing systems, the network is controlled to guide systems to a desired state. Although existing controlled self-organization schemes could achieve this feature, convergence speed for reaching an optimal or semioptimal solution is still a challenging task. We perform potential-based self-organizing routing and propose an optimal feedback method using a reduced-order model for faster convergence at low cost. Simulation results show that the proposed mechanism improves the convergence speed of potential-field construction (i.e., route construction) by at most 22.6 times with low computational and communication cost.

Potential-based routing for supporting robust any-to-any communication in wireless sensor networks

In most applications, wireless sensor networks are supposed to operate in an unattended manner for a long period after sensor nodes’ deployment. However, in such networks, sensor nodes frequently become faulty and unreliable because of the harsh environment of the observed area. Therefore, protocols used in wireless sensor networks must be designed to be robust. Moreover, because the battery capacity of a node is limited, energy savings are crucial in wireless sensor networks. To meet the requirements of future diverse wireless sensor networks, a sophisticated any-to-any routing protocol is thus required. As well as meeting the typical demands of wireless sensor networks, an any-to-any routing protocol needs to achieve low energy consumption, high scalability, robustness, and reliability. In this paper, we realize a potential-based any-to-any routing protocol (PBAR) by merging potential-based upstream and downstream routing. In PBAR, sensor nodes can send data to a certain sensor node by routing the data via a sink node. In simulation experiments, we show that, given a suitable node density, PBAR attains a data delivery ratio greater than 99.7%. We also show that the data delivery ratio recovers immediately after failure of 30% of sensor nodes or failure of a sink node.

Lifetime extension based on residual energy for receiver-driven multi-hop wireless network

For sensor networks, the extension of operating time by controlling power consumption is an important research subject. In a receiver-driven communication protocol, a receiver node transmits its ID to the sender node periodically, and in response the sender node sends an acknowledgment. The average power consumption of the network can be controlled, but a part of the network shuts down when the battery of the node that consumes the most power is completely discharged. To extend the network lifetime, we propose a method where information on residual energy is exchanged through ID packets in order to balance power consumption. We show that the network lifetime can be extended by about 75% while maintaining network performance such as the packet collection ratio and delay.

Application of evolutionary mechanism to dynamic Virtual Network Function Placement

Recently, communication network services have become increasingly diverse and dynamic. Network Function Virtualization (NFV) is an effective technique to deal with these dynamic situations. Most related work on the VNF placement problem does not consider the dynamics of requests, but only static scenarios. The important goals of the dynamic VNF placement problem include accommodating new requests following the traffic dynamics and reducing the time to calculate solutions. To tackle this problem, we utilize the concept of Modularly Varying Goals (MVG), which is based on a genetic algorithm (GA) and generates solutions that can easily adapt to time-varying goals in short time. In this paper, we propose Evolvable VNF Placement (EvoVNFP) that applies the concept of MVG to the dynamic VNF placement problem to reduce the time to obtain solutions. Results from numerical evaluations show that our method is able to better follow the dynamics of VNF requests and also reduce time until adapting to successive objectives.

Virtual Wireless Sensor Networks: Adaptive Brain-Inspired Configuration for Internet of Things Applications.

Many researchers are devoting attention to the so-called “Internet of Things” (IoT), and wireless sensor networks (WSNs) are regarded as a critical technology for realizing the communication infrastructure of the future, including the IoT. Against this background, virtualization is a crucial technique for the integration of multiple WSNs. Designing virtualized WSNs for actual environments will require further detailed studies. Within the IoT environment, physical networks can undergo dynamic change, and so, many problems exist that could prevent applications from running without interruption when using the existing approaches. In this paper, we show an overall architecture that is suitable for constructing and running virtual wireless sensor network (VWSN) services within a VWSN topology. Our approach provides users with a reliable VWSN network by assigning redundant resources according to each user’s demand and providing a recovery method to incorporate environmental changes. We tested this approach by simulation experiment, with the results showing that the VWSN network is reliable in many cases, although physical deployment of sensor nodes and the modular structure of the VWSN will be quite important to the stability of services within the VWSN topology.

Enhancing Convergence with Optimal Feedback for Controlled Self-Organizing Networks.

To tackle with problems emerging with rapid growth of information networks in scale and complexity, selforganization is one of promising design principles for future networks. Convergence of self-organizing controls, however, is pointed out to be comparatively slow in some practical applications. Therefore, it is important to reveal and enhance convergence of self-organizing controls. In controlled self-organization, which introduces an external observer/controller into self-organizing systems, systems are controlled in order to guide them to the desired state. Although previous controlled self-organization schemes could achieve this feature, convergence speed for reaching an optimal or a semi-optimal solution is still a challenging task. In this paper, we take potential-based self-organizing routing and provide an optimal feedback for faster convergence using the future state of the system. Simulation results show that the convergence speed of potentials is improved by 7.3 times with a proposed mechanism.