Cai Wenyu

UUV mobility management for underwater acoustic sensor networks

Underwater acoustic sensor networks typically comprised of sensor nodes that are deployed in sufficiently large numbers for data collection, monitoring and surveillance. Multi-hop relay transmission manner is used to deliver acquired data from sensor nodes to the sink node; nevertheless, hot spots around sink node will bring severe problems. In underwater sensor networks model of this paper, nodes are divided into two components: static sensor nodes and mobile UUV (Underwater Unmanned Vehicles), i.e., conventional sink node is replaced by mobile UUV. The mobile UUV in this novel framework takes charge of collecting sensory data from different sensor nodes and delivering all the sensory data to the monitoring center. Comparing with traditional model of underwater sensor networks, it is beneficial to use mobile UUV to ferry sensory information instead of using multi-hop relay transmission method, because the energy of sensor nodes in harsh oceanic environment is very limited. In order to improve energy efficiency, we therefore proposed a novel UUV mobility management scheme for underwater acoustic sensor networks that aims to achieve robustness and energy efficiency under harsh underwater acoustic channel conditions. The proposed mobility management scheme determines UUV movement routing using directional metric functions considering location information and energy level of sensor nodes. Furthermore, a hierarchical model based on cluster structure is induced where sensor nodes are grouped into clusters after they are deployed, therefore, UUV will only collect fused data of cluster heads but not every cluster members, thus to simplify route of UUV. Finally, the simulation results verified the efficacy of the proposed mobility management scheme.

Distributed Power Control Algorithm with Multi-QoS Constraints for Wireless Sensor Networks

In this paper, we present a Distributed Power Control algorithm with Multi-QoS Constraints (MQDPC) for WSNs (wireless sensor networks). Energy consumption, reliability and QoS provisioning are three key objectives in WSNs. In MQDPC algorithm, each sensor node independently builds its local maximum QoS topology according to the local information collected from its one-hop neighbors using MST (minimum spanning tree) scheme, therefore MQDPC algorithm is a fully distributed algorithm. The QoS metrics considered in this algorithm comprise node residual energy, end-to-end delay and link loss ratio. We analytically prove that MQDPC algorithm preserves the network QoS topology connectivity and show that MQDPC algorithm is scalable to large-scale wireless sensor network and multidimensional QoS metrics. The simulation results demonstrate that MQDPC algorithm dynamically builds network topology when wireless sensor network topology status varies over the time, and MQCTC algorithm can efficiently prolong the network life span and improve QoS performance while meeting certain QoS requirements.

CDS-based coverage control algorithm for buoys based sensor networks

Underwater acoustic sensor networks (UASN) based on the advances in underwater data collection and observing systems may play an important role in oceanographic research. UASN typically comprises of sensor nodes that are deployed in sufficiently large numbers for data collection, monitoring and surveillance, where sensor nodes are also energy limited without easy way to replenish power unfortunately. Due to severely limited energy constraints of nodes and poor transmission feature in the harsh oceanic environment, how to conserve energy while maintaining network coverage has been one of the most difficult problems. As one special kind of UASN, Buoys based sensor networks (BSN) proposed by ourselves comprises a mass of buoy-based vertical detection chains, which are regard as surface buoy nodes in one planar sea level. Compared with UASN, BSN can extend coverage distance and improve wireless transmission rate, therefore, it is one more promising method to perform oceanic three-dimensional exploration. This paper investigates the utility of a Connected Dominating Set (CDS) based coverage control algorithm for buoys based sensor networks. Traditional CDS-based algorithm maintains a connected virtual backbone of awaking nodes to enable necessary information delivery. Surface buoy nodes belonging to CDS virtual backbone remain awake until the next new round, whereas non-CDS buoy nodes go to low-powered sleep mode. However, how to maintain network coverage of BSN has not been considered. Surface buoy nodes are more sparsely deployed because of their much higher prices, therefore, wireless communication links are prone to break and regions of interest (ROI) are prone to blind monitoring since lack of accurate placement. This paper used CDS-based coverage control algorithm to decide buoys scheduling policy so as to guarantee network reliability and robustness.

Multi-source Distributed Video Coding in Wireless Video Sensor Networks for Water Conservancy Engineering

Based on analysis of characteristics of UV (Ultraviolet) light power envelope and the output signal of the detector, a modulation scheme for UV communication system employing low pressure mercury lamp as lamp house was proposed. In the scheme, the frequency of UV power envelope is controlled by the current frequency in the electronic ballast and the scheme is similar to the BFSK (Binary Frequency-Shift keying). The modulation experiment was carried out using low pressure mercury lamp as lamp-house. Results show that the modulation scheme is viable.

OpenCV based computer vision of deep-sea visual exploration system

Deep-sea visual exploration system plays an important role in the area of deep-sea expedition. Because of the harsh ocean environment, the deep-sea visual exploration system may face many problems such as high press of deep sea, instantaneous impact, deep-sea surge, local high temperature etc. Therefore, most current deep-sea visual exploration systems are not practicable. In this paper, considering the strongpoint of MPEG-4 coding and decoding technology with G.SHDSL modulation and demodulation technology, we designed a deep-sea visual exploration device based on 10000 m coaxial cable and MPEG-4 video server. Moreover, as a step up, computer vision based on OpenCV development kit has been introduced in this deep-sea visual exploration device. As a scientific discipline, computer vision is concerned with the theory for building artificial systems that obtain information from images, on the other hand, computer vision technology studies and describes artificial vision system that is implemented in software and/or hardware. With computer vision technology, deep-sea visual exploration system can obtain better performance and is intelligent enough to deal with some simply instance. As a consequence, the proposed deep-sea visual exploration device has been working on the ship named as ocean-one for many years, and has obtained many wonderful deep-sea video material, as a result, has made important contributions to ocean investigation enterprise of China.