Rui Teng

On-Demand Information Retrieval in Sensor Networks with Localised Query and Energy-Balanced Data Collection

On-demand information retrieval enables users to query and collect up-to-date sensing information from sensor nodes. Since high energy efficiency is required in a sensor network, it is desirable to disseminate query messages with small traffic overhead and to collect sensing data with low energy consumption. However, on-demand query messages are generally forwarded to sensor nodes in network-wide broadcasts, which create large traffic overhead. In addition, since on-demand information retrieval may introduce intermittent and spatial data collections, the construction and maintenance of conventional aggregation structures such as clusters and chains will be at high cost. In this paper, we propose an on-demand information retrieval approach that exploits the name resolution of data queries according to the attribute and location of each sensor node. The proposed approach localises each query dissemination and enable localised data collection with maximised aggregation. To illustrate the effectiveness of the proposed approach, an analytical model that describes the criteria of sink proxy selection is provided. The evaluation results reveal that the proposed scheme significantly reduces energy consumption and improves the balance of energy consumption among sensor nodes by alleviating heavy traffic near the sink.

Dynamic Recovery of Wireless Multi-Hop Infrastructure With the Autonomous Mobile Base Station

Wireless multihop infrastructures (WMIs) are promising network platforms that facilitate applications, such as smart cities, emergency responses, and outdoor events. WMIs can allow coverage over large areas with low setup and maintenance overheads. However, WMIs may be susceptible to loss of network connectivity caused by node damage or energy depletion. The end-to-end reachability is essential for the WMI to provide network service to users. This paper studies the problem of network self-recovery to sustain reachability in a WMI network by utilizing autonomous mobile base stations (MBSs). It is assumed that MBS is able to move to and pause or stop at positions in the network area. An MBS could be a self-driving robotic vehicle, or vehicle driven directly or remotely by a human. The proposed MBS approach, MBS-Fit, is a distributed and packet-interaction-based mechanism that allows MBS to automatically construct new routes, assess, and adaptively respond to the fitness of pause positions, such that MBS can provide links to recover the disconnected WMIs. We adopt packet-level evaluation to study the automatic interactions of MBS with the static WMI objects. In particular, the network reachability is measured by the amount of packets successfully delivered from users to the gateway through the WMI. Simulation results reveal that the proposed MBS-Fit approach achieves up to 30% improvement of network reachability in terms of successfully packet delivery compared with the conventional MBS. MBS-Fit mechanism also enables up to 80% improvement in terms of number of packets forwarded at MBS.

Local Recovery of Wireless Multihop Infrastructure with the Autonomous Mobile Base Station

Wireless Multihop Infrastructures (WMIs) are promising network platforms for the applications such as smart cities, emergency responses, and outdoor events. On the other hand, the low cost maintenance and large coverage of WMIs are subject to the network dis-connectivity, which can be caused by node damage or energy depletion, especially in the emergency situations and off-grid locations. The end to end reach ability is essential for the WMI to provide the network service to users. To enable the sustainable network reach ability in the disconnected WMI, this paper studies local maintaining and recovery of network infrastructure by utilizing autonomous mobile base stations (MBSs). The proposed MBS approach, MBS-Fit, is a distributed mechanism that addresses pause control problem in terms of pause length and fitful pause positions such that MBS can provide reach ability for the disconnected WMIs. The network reach ability is mainly measured by the amount of packets arrived from users to the gateway through the WMI. We adopt packet level evaluation to study the automatic interactions of MBS with the static WMI objects for local recovery of network infrastructure. Simulation results reveal that the proposed MBS-Fit approach achieves up to 30 percent improvement of network reach ability in term of packet delivery compared with conventional MBS. MBS-Fit mechanism also enables up to 80 percent improvement in terms of packet forwarding number at MBS.

The Localized Discovery and Recovery for Query Packet Losses in Wireless Sensor Networks with Distributed Detector Clusters

An essential application of wireless sensor networks is to successfully respond to user queries. Query packet losses occur in the query dissemination due to wireless communication problems such as interference, multipath fading, packet collisions, etc. The losses of query messages at sensor nodes result in the failure of sensor nodes reporting the requested data. Hence, the reliable and successful dissemination of query messages to sensor nodes is a non-trivial problem. The target of this paper is to enable highly successful query delivery to sensor nodes by localized and energy-efficient discovery, and recovery of query losses. We adopt local and collective cooperation among sensor nodes to increase the success rate of distributed discoveries and recoveries. To enable the scalability in the operations of discoveries and recoveries, we employ a distributed name resolution mechanism at each sensor node to allow sensor nodes to self-detect the correlated queries and query losses, and then efficiently locally respond to the query losses. We prove that the collective discovery of query losses has a high impact on the success of query dissemination and reveal that scalability can be achieved by using the proposed approach. We further study the novel features of the cooperation and competition in the collective recovery at PHY and MAC layers, and show that the appropriate number of detectors can achieve optimal successful recovery rate. We evaluate the proposed approach with both mathematical analyses and computer simulations. The proposed approach enables a high rate of successful delivery of query messages and it results in short route lengths to recover from query losses. The proposed approach is scalable and operates in a fully distributed manner.

Differentiation Presentation for Sustaining Internet Access in a Disaster-Resilient Homogeneous Wireless Infrastructure

A wireless multihop infrastructure (WMI) employs homogeneous and easily deployable wireless routers to facilitate disaster-resilient Internet access in smart cities, emergency situations, and the Internet of Things. On the other hand, however, a WMI is subject to energy constraints, carries unbalanced traffic, and has weaknesses in terms of maintenance, such as the lack of human management. Therefore, efficiently sharing network tasks and energy consumption in a WMI are essential to network sustainability. In this paper, we consider the problem of explicit differentiation presentation for improving network sustainability, which involves two aspects. One is the problem of quantifying the differentiation of network activities and energy consumption. The other is the problem of utilizing the differentiation factor of each node for routing operations so as to regulate network packet flows for sustaining Internet access in a WMI. We examine the differentiation of network activities and energy consumption in WMIs by considering network activities, including not only packet transmission and reception but also packet overhearing, and other types of energy consumption. Based on the quantification of energy differentiation at each base station (BS), we design a novel router metric that enables an efficient sharing of network activities among BSs. The theoretical analyses of energy differentiation were validated based on the packet-level simulation. The simulation results demonstrate that our proposed router metric based on energy differentiation outperforms various other competitive metrics of multihop wireless networks to improve network sustainability for different network models.

Mobile base station with conformational selections for the network maintenance in wireless multihop infrastructure

Wireless multihop infrastructure (WMI) networks can provide essential support for information exchange and the Internet access, particularly during emergencies and in smart cities. However, limited network resources during emergencies may result in node energy depletion and network disconnection, leading to service failures to users in the WMI network. This paper aims to use mobile base stations (MBSs) to automatically form paths and spontaneously maintain network availability as a connected infrastructure. The problems to deal with are the limited information and resources for MBS to quickly construct efficient connections in a WMI network. We propose a bio-inspired approach, which enables MBS to interact with the network based on insights from conformational selections in enzyme-substrate binding. In analogy to selective binding of enzyme-substrates, the proposed MBS approach uses selective pauses based on the traffic status of selective packet forwarding at appropriate positions, at which MBS is capable of sustaining WMI connectivity. The proposed MBS approach reduces energy consumption of base stations that have energy constraints and heavy traffic to handle, and it improves WMI network availability. Evaluation using packet-level simulation reveals that the proposed MBS approach achieves up to 40% improvement for the availability of network as a full connected infrastructure.

Sustaining the emergency wireless multihop infrastructure by distributed sharing of energy consumption

Wireless multihop infrastructures WMIs facilitate low-cost and quick deployable network infrastructures for emerging applications in emergency responses and smart cities. Cooperative sharing of energy consumption is essential for network sustainability. This paper studies the problem of cooperative sharing of routing services in an emergency WMI E-WMI by examining the regulation of route switching from perspectives of network-wide and long-time energy efficiency. A key idea in the regulation of route switching is employing explicit routing terms among base stations in an E-WMI, allowing tolerance of temporary imbalance of energy consumption in the network. A routing term refers to a period for a base station to continuously serve routing in an E-WMI. By taking into account the specific features of E-WMIs, this paper overcomes the challenging problems of complexity and difficulty in examining the explicit route switching and energy distribution in multihop networks. We find that there exists the optimal routing term and number of route switching for the long-time energy efficiency. With the optimal routing terms, a network can take a principle of distributed energy sharing by route switching management rather than only applying end-to-end energy-efficient routing that does not have a long-time management of network energy consumption.

Performance Evaluation of the Network Sustainability in Wireless Multi-hop Infrastructures with Biased User Mobility

Wireless Multi-hop Infrastructures (WMIs) enable mobile users to access the Internet through wireless multi-hop connections. Compared with conventional network infrastructures, WMIs have the low cost and flexible network deployment. The applications of WMI include smart cities, emergency responses and Internet of things. In emergency situations, WMI networks may have energy constraint. Furthermore, user mobility may be restricted to a limited area. In this paper, we study the network sustainability performance in WMI networks that have energy constraint and limited scope of user mobility. The sustainability of the WMI depends on network energy, connectivity, as well as user distributions. The collective sharing of network tasks among infrastructure nodes highly affects the network sustainability. However, few studies to date addressed the sustainability performance of network with the decreasing of both node energy and network connectivity. This paper specially examines the impact of decreasing energy and connectivity depletion in WMIs that have biased scope of user mobility. Performance evaluation is conducted based on packetlevel simulations. The evaluation show spatio-temporal features of energy-and-connectivity in WMI networks. With the investigation of various routing metrics, evaluation results show that energyaware metric leads to the collective sharing of packet forwarding with 16-30 percent improvement at the BSs out of the user mobility scope. The results also show that limited scope of user mobility leads to a decrease of network lifetime.