Ning Huang

Deployment-Based Lifetime Optimization Model for Homogeneous Wireless Sensor Network under Retransmission

Sensor-deployment-based lifetime optimization is one of the most effective methods used to prolong the lifetime of Wireless Sensor Network (WSN) by reducing the distance-sensitive energy consumption. In this paper, data retransmission, a major consumption factor that is usually neglected in the previous work, is considered. For a homogeneous WSN, monitoring a circular target area with a centered base station, a sensor deployment model based on regular hexagonal grids is analyzed. To maximize the WSN lifetime, optimization models for both uniform and non-uniform deployment schemes are proposed by constraining on coverage, connectivity and success transmission rate. Based on the data transmission analysis in a data gathering cycle, the WSN lifetime in the model can be obtained through quantifying the energy consumption at each sensor location. The results of case studies show that it is meaningful to consider data retransmission in the lifetime optimization. In particular, our investigations indicate that, with the same lifetime requirement, the number of sensors needed in a non-uniform topology is much less than that in a uniform one. Finally, compared with a random scheme, simulation results further verify the advantage of our deployment model.

A new model of network cascading failures with dependent nodes

As real network systems are becoming ever more complex and widely-used, network failures often bring about devastating effects on our personal and professional lives. Therefore, failure regularity and reliability issues of real-world networks are primary concerns for network science researchers. In many real-world networks, cascading failures are not only caused by dynamical redistribution of network loads. Dependency relations among network nodes could also increase the spread of network failures, and even markedly impact the process of cascading failures. However, most of the existent cascading failure models used for network reliability analysis still merely focus on the dynamics of network loads for causing cascades without considering the joint effect of dependencies among network nodes. Based on previous studies and complex network theories, a new cascading failure model considering the synergies existing between dependency clusters of nodes and the dynamic distribution of network loads is proposed, upon which we analyze the effect of dependencies among network nodes on propagation of network failures. Firstly, we group network nodes into dependency clusters. Then, by triggering random break down of network nodes, we simulate cascading failures on random networks. The simulation results show that dependencies among network nodes will severely accelerate failure propagation and exacerbate the damage of cascading failures, in accordance with real situations. The obtained results firmly verify that the proposed cascading failure model describes the actual mixed failure behavior of networks with dependent nodes.

A sensor deployment optimization model of the wireless sensor networks under retransmission

Wireless sensor networks (WSN) are widely applied in the supervisory control of the agriculture, biology, transportation, military and many other fields. An excellent node deployment strategy can largely reduce the energy consumption and optimize the lifetime of WSN. In this paper, a new node deployment model based on regular hexagon grids is proposed for a homogeneous flat WSN. Both the data transmission and energy consumption of each sensor in a data gathering cycle are analyzed based on energy consumption models, a routing algorithm, a retransmission model and a sleep/wakeup mechanism. Two optimization models for uniform and non-uniform sensor deployment schemes are proposed to minimize the energy consumption under the constraints of connectivity and coverage requirements. The results of our case studies show that when retransmission is considered, there are much less nodes and initial energy needed in the deployment of the WSN.

Cyber-physical avionics systems and its reliability evaluation

Avionics systems play a significant role in civil aircraft, and its reliability is directly related to the flight safe. In this paper, integrated modular avionics (IMA), as the most advanced avionics systems, is analyzed. Via exploration of the interaction mechanism of IMA and real physical system, its property of cyber-physical systems (CPS) is determined. Hence, according to different functional modules, a cyber-physical avionics systems model is established for IMA, meanwhile task-oriented state spaces of sub-units in CPS architecture are assigned to construct the hierarchical model for reliability model of IMA. A mathematic formula is presented to calculate reliability. The key contribution is that task-oriented cyber-physical idea is applied, and a hierarchical model for reliability analysis of IMA is presented. At last, reliability model is applied to a case study, which shows that two different way to raise IMA reliability.

Fault propagation model in mobile ad hoc network based on random walk model

In this paper, a fault propagation model (FPM) of mobile ad hoc network (MANET) is proposed based on random walk model. We adopt the random walk model to describe the movement behavior of the nodes in MANET. Based on this model, the influence of the average transmission range, the nodes number and the size of the simulation areas on MANETs connectivity is studied. And the comparison of the influence of different causes on the message loss fault in different conditions is given. Finally, according to the state of the nodes and the paths, the position distribution of the congestion nodes and paths is presented. Using the model can distinctly describe the congestion state of the whole network, and the fault data could be directly collected from the FPM, which can make great contributions to MANETs network control and optimization.

Lifetime optimisation for linear wireless sensor networks under retransmission

The lifetime of wireless sensor networks WSN is strongly affected by the energy consumption, which is partly attributed to retransmission. In this paper, the energy consumption of a linear WSN is analysed based on basic energy consumption models and a retransmission model. Optimisation models are proposed with the objective of maximising WSN lifetime under the coverage and success transmission rate constraints. In particular, for traditional uniform and non-uniform sensor deployment problems without considering the sleep/wakeup mechanism, the number of sensors and their distances are optimised. Moreover, for a linear WSN with a sleep/wakeup mechanism, a sensor deployment scheme is developed by optimally assigning sensors to fixed locations. The genetic algorithm and the generalised reduced gradient method are applied to solve these problems. Our case studies illustrate that the lifetime of WSN with and without retransmission are different, and it is important to consider retransmission in WSN lifetime optimisation.

Performability optimization design of virtual links in AFDX networks

The Avionics Full Duplex switched Ethernet (AFDX) is widely used in the new generation of civil aircraft, such as A380 and Boeing787. Some research works have been conducted to optimize virtual links (VLs) design. However, a method that optimizes the VLs design scheme from the perspective of network performability is still missing. Furthermore, the configuration parameters interact with each other, making the optimization more complicated. Therefore, it is urgent to propose an effective and feasible optimization design scheme for VLs to improve the network performability. In this paper, we focus on optimizing the VLs design scheme in the view of Interface Control Document (ICD). Firstly, according to the ICD messages, other authors methods are utilized to obtain the initial VLs design scheme. Secondly, two-layer network model is used to model the AFDX. According to the correspondence between the parameters with two-layer, the parameters are divided into two parts. For each layer, optimization model is established. Network calculus is utilized to calculate the end-to-end delay in the physical layer. Thirdly, we put forward the corresponding optimization algorithm. Operations research method is used to obtain the reasonable parameters in the whole network. For the logical layer, we use an improved Frank Wolfe algorithm to get VL routing. And for the physical layer, we use heuristic algorithm to get {BAGi, Lmaxi}. At last, we evaluate the performance of the proposed scheme by a case study with airborne application flows, and the optimization results are analyzed in detail. After the optimization process, the performability meets the requirement and the average bandwidth utilization and the average end-to-end delay are observably reduced.

Traffic chaotic dynamics modeling and analysis of deterministic network

Network traffic is an important and direct acting factor of network reliability and performance. To understand the behaviors of network traffic, chaotic dynamics models were proposed and helped to analyze nondeterministic network a lot. The previous research thought that the chaotic dynamics behavior was caused by random factors, and the deterministic networks would not exhibit chaotic dynamics behavior because of lacking of random factors. In this paper, we first adopted chaos theory to analyze traffic data collected from a typical deterministic network testbed — avionics full duplex switched Ethernet (AFDX, a typical deterministic network) testbed, and found that the chaotic dynamics behavior also existed in deterministic network. Then in order to explore the chaos generating mechanism, we applied the mean field theory to construct the traffic dynamics equation (TDE) for deterministic network traffic modeling without any network random factors. Through studying the derived TDE, we proposed that chaotic dynamics was one of the nature properties of network traffic, and it also could be looked as the action effect of TDE control parameters. A network simulation was performed and the results verified that the network congestion resulted in the chaotic dynamics for a deterministic network, which was identical with expectation of TDE. Our research will be helpful to analyze the traffic complicated dynamics behavior for deterministic network and contribute to network reliability designing and analysis.

Traffic dynamics on networks with competitive services

Competitive services have large effects on traffic congestion. Based on the investigation on Chinese railway network, a competitive services model is proposed to capture traffic correlations between different services. According to the value of the weight parameter 𝜃, competitive services are grouped into assortative, disassortative and neutral ones, in which their traffic loads show strongly positive, weakly positive and non-significant correlations, respectively. Simulation results illustrate that our model can effectively capture the service correlations by adjusting the weight parameter. Using this model, we analyze the influence of different types of competitive services on network congestion. Our results indicate that both capacity and efficiency of network is the lowest when it supports assortative services.

An application oriented evaluation method for network performance reliability

Congestion phenomenon has been observed in communication networks for many years, and one important reason for this is the effect of network applications. In actual networks, different applications may be provided by the same server node. This results in coupling between the applications. This coupling relationship makes it difficult to evaluate actual network reliability, with network applications. So an effective method to evaluate the network reliability considering the actual use of network applications is required. In this paper, we focus on the evaluation of network performance reliability with the consideration of two different network applications. First, the actual use of two network applications are divided into three different situations: DCA (double coupled applications), SCA (single coupled applications) and NCA (no coupled applications) respectively. Then, considering the network applications, we improve the traffic model, which is commonly used to analyze the dynamics of traffic in complex network. Finally, based on the improved traffic model, an application oriented evaluation method is proposed to evaluate the network performance reliability considering the users tolerance thresholds. The coupling coefficient is used to measure the coupling strength between two applications. The network performance reliability on a lattice network adopting the shortest path routing strategy with the DCA, SCA and NCA are studied respectively and some interesting results are observed. When the number of application server nodes is small enough compared with the network scale, coupled nodes in the network have significant impact on the network performance reliability and congestion is more likely to happen in coupled no des. When the number of the server nodes is fixed, the network is more reliable with the NCA and more unreliable with the DCA. With the same coupling coefficient, the network is more reliable with the DCA than that with the SCA. With the SCA and the same coupling coefficient, the smaller the bias from the average applications scale is, the more reliable the network is.