Xinhua Liu

An Optimal Power-Controlled Topology Control for Wireless Sensor Networks

The efficacy of topology control has been shown to be a vital process to maximize the network lifetime of wireless sensor networks. In this paper, we present a distributed topology algorithm with transmission power adjustment based on optimal number of neighbors to raise the network energy-efficiency and the network throughput by reducing channel competition intensity and simplifying the complexity of initial network topology. In the algorithm, every node can adjust its transmission power level and calculate its optimal transmission power according to the optimal number of neighbors, and a virtual clustering scheme based on optimal transmission power is proposed for network topology control, where the network connectivity is also guaranteed. Analysis and simulation results demonstrate the correctness and effectiveness of our algorithm.

Data Transfer Protocol in Bridge Structural Health Monitor System using Wireless Sensor Network

In this paper, a structure health monitor (SHM) system for the bridge is introduced, of which wireless communication and embedding techniques are deployed. After summing up the wireless communication techniques and time synchronization requirements in practical application, a data transfer protocol based on clock synchronization and reliability in wireless sensor networks is proposed, and then its time synchronization error analysis are discussed. All of the related work contributes to the development of a commercial, cost-effective, and reliable SHM system

A Vehicle Steering Recognition System Based on Low-Cost Smartphone Sensors

Recognizing how a vehicle is steered and then alerting drivers in real time is of utmost importance to the vehicle and driver’s safety, since fatal accidents are often caused by dangerous vehicle maneuvers, such as rapid turns, fast lane-changes, etc. Existing solutions using video or in-vehicle sensors have been employed to identify dangerous vehicle maneuvers, but these methods are subject to the effects of the environmental elements or the hardware is very costly. In the mobile computing era, smartphones have become key tools to develop innovative mobile context-aware systems. In this paper, we present a recognition system for dangerous vehicle steering based on the low-cost sensors found in a smartphone: i.e., the gyroscope and the accelerometer. To identify vehicle steering maneuvers, we focus on the vehicle’s angular velocity, which is characterized by gyroscope data from a smartphone mounted in the vehicle. Three steering maneuvers including turns, lane-changes and U-turns are defined, and a vehicle angular velocity matching algorithm based on Fast Dynamic Time Warping (FastDTW) is adopted to recognize the vehicle steering. The results of extensive experiments show that the average accuracy rate of the presented recognition reaches 95%, which implies that the proposed smartphone-based method is suitable for recognizing dangerous vehicle steering maneuvers.

A street lamp clustered-control system based on wireless sensor and actuator networks

In order to resolve the problems of city street lamp control and management, a street lamp clustered-control system based on wireless sensor and network (WSANs) is proposed in this paper. In the system, the related information of vehicles running on the road will be detected by the sensors deploying along the both side of the road, and then the sensing data will be passed to the actuators being equipped on the lamps through multi-hop wireless communication. The actuators gather the information from the sensors and regulate the brightness of the lamp by the distributed and cooperated control algorithm. According the security rulers of driving a vehicle, a certain number of lamps in a security distance before and after the vehicle will be turned on. The street lamp clustered-control system is good at energy saving and validated by the experiment results.

Disturbance based dynamic load balancing routing mechanism under SDN

In Data center network, with the rapid development of network applications, how to balance the network load has become the focus of everyones attention. It is required to fully utilize the resources such as bandwidth to provide high bandwidth for various cloud computing service. In this paper, we propose a dynamic load balancing routing mechanism based on disturbance under SDN. The proposed scheme has two critical parts: 1) A static load balancing routing algorithm called S-LBR is proposed. 2) A disturbance based re-routing scheme called D-LBR is proposed to balance the load and improve the link utilization. Normally, the controller uses the S-LBR to form a flow table entry. When the network load imbalance, we adjust the load according to the network load, then we start D-LBR, each adjustment is a disturbance. We finally combine the two algorithms to derive the D-ALBR.

An efficient backoff algorithm for QoS guaranteeing in wireless networks

Wireless networks are required to guarantee the Quality of Service (QoS), including throughput, fairness, delay, etc. IEEE802.11 MAC protocol employs a typical backoff mechanism, Binary Exponential Backoff (BEB) algorithm, to avoid collisions when multiple users try to access the shared wireless channel. Many works on QoS guaranteeing point out that the BEB algorithm introduces the unfairness and serious delay problem into channel access. To solve the problem above, this paper proposes a novel backoff algorithm, which adopts a retransmission counter to measure the network congestion situation. The proposed algorithm also divides the contention window interval into small intervals, and in different intervals, it leverages different backoff strategies. Performance of this algorithm is compared with BEB and other improved backoff algorithms through simulation. The analysis and simulation results show that the proposed backoff algorithm can provide better QoS guaranteeing in terms of throughput, fairness, and delay.

A generic model of multi-interface and multi-channel for multi-hop wireless networks

The performance of multi-hop wireless networks can be improved through using multi-interface and multi-channel (MIMC). In this paper, a generic model of MIMC (abbreviated as GMM) for multi-hop wireless networks is proposed for NS2. The architecture of GMM consists of an MIMC control sublayer, separated interfaces, and dynamic channels. The MIMC control sublayer manages all interfaces and channels, and provides MIMC services to upper layers. Each separated interface has its own physical layer, MAC layer, link layer, and propagation model so that it can support heterogeneous interfaces. The dynamic channels are shared by all the interfaces, and each interface can be assigned to one or more channels by a preset channel assignment algorithm. Compared with other existing MIMC models, the proposed GMM is more generic and more flexible. The proposed GMM is validated through experiments, and network performances are discussed as well.

An actuator real-time placement algorithm based on regular hexagonal grid for wireless sensor and actuator networks

Network coverage is one of key issues for designing a practical Wireless Sensor and Actuator Network (WSANs). In view of real-time coverage and convergence of mobility coverage, an actuator real-time placement algorithm based on regular hexagonal grid for WSANs (ARP-RGH) is proposed. In this algorithm, firstly, a regular hexagonal grid plot algorithm is used to choose the idea location of actuators for maximizing the monitoring area coverage of the network from a theoretical perspective; and then, the actuators are spreaded in the form of uniform distribution by a moving algorithm based on virtual forces; at last, according to the ideal location calculated before, the optimal location of actuators is given by real-time coverage rounds algorithm. ARP-RHG algorithm implements the optimal coverage of actuators under real-time coverage constrain conditions, and makes the actuators avoid moving into the holes of sensor distribution. The results of the simulation show that the ARP-RHG algorithm has good coverage and convergence.