Cheng Pan

Task Allocation for Wireless Sensor Network Using Modified Binary Particle Swarm Optimization

Many applications of wireless sensor network (WSN) require the execution of several computationally intense in-network processing tasks. Collaborative in-network processing among multiple nodes is essential when executing such a task due to the strictly constrained energy and resources in single node. Task allocation is essential to allocate the workload of each task to proper nodes in an efficient manner. In this paper, a modified version of binary particle swarm optimization (MBPSO), which adopts a different transfer function and a new position updating procedure with mutation, is proposed for the task allocation problem to obtain the best solution. Each particle in MBPSO is encoded to represent a complete potential solution for task allocation. The task workload and connectivity are ensured by taking them as constraints for the problem. Multiple metrics, including task execution time, energy consumption, and network lifetime, are considered a whole by designing a hybrid fitness function to achieve the best overall performance. Simulation results show the feasibility of the proposed MBPSO-based approach for task allocation problem in WSN. The proposed MBPSO-based approach also outperforms the approaches based on genetic algorithm and BPSO in the comparative analysis.

Analytical study of the IEEE 802.11p EDCA mechanism

The Enhanced Distributed Channel Access (EDCA) mechanism has been adopted by media access control (MAC) layer of IEEE 802.11p to provide contention-based differentiated channel access for packets with different priorities. To analyze the performance of EDCA mechanism, the two-dimensional Markov chain model with the different contention windows(CW) and the internal collision and the frozen mechanism, has been proposed to calculate the normalized throughput and the time delay. The results show that the normalized throughput decreases and the time delay increases with the number of vehicles increasing; and the packets with higher priority have a larger numerical value of normalized throughput and lower time delay than the lower priority packets. The delay for high priority ACs satisfy their requirements, which verify that the IEEE 802.11p EDCA can provide effective service for the safety related time critical applications.

Performance evaluation of IEEE 802.11p vehicle to infrastructure communication using off-the-shelf IEEE 802.11a hardware

IEEE 802.11p standard was ratified in July 2010 to enhance road safety. Though its performance has been evaluated theoretically or by simulations in the past, field tests are not widely conducted because IEEE 802.11p hardware is rare and expensive. This paper is aimed at proposing a program to solve this problem. Firstly, we analyze the similarities and differences between IEEE 802.11p and IEEE 802.11a/e contrastively. Secondly, a communication platform of approximate IEEE 802.11p is implemented using off-the-shelf IEEE 802.11a hardware with specific parameters amending. Thirdly, vehicular networking field tests are conducted in order to analyze the impact of distance, antenna settings (e.g. height, angle and gain) and vehicle speed on the performance metrics (e.g. link variability, delay and packet loss rate,) of IEEE 802.11p in vehicle-to-infrastructure(V2I) communications. Finally, we draw conclusions and provide guidance for the future deployment of RSU(Roadside Unit) and OBU(On Board Unit).

Learning-based routing approach for direct interactions between wireless sensor network and moving vehicles

Wireless sensor network (WSN) has been applied to traffic information collection in many researches. Moving vehicles in the road need to acquire real time traffic information directly from WSN to make proper decisions and avoid potential accidents. Due to the large scale deployment of WSN, routing is necessary to deliver real time information to vehicles in a multi-hop way. Taking the moving vehicle as a mobile sink, a reinforcement learning-based routing approach is proposed to support sink mobility and enable direct interactions between WSN and vehicles. Multiple metrics including time delay, network lifetime and reliability are ensured by designing a comprehensive reward function for learning. The convergence speed of learning is improved with sink announcement. Simulation results show the feasibility of the proposed approach for direct interactions between WSN and moving vehicles. Comparisons are also carried out to show the superiority of the proposed approach over other approaches.

SN-UTIA: A sensor network for urban traffic information acquisition

An architecture of sensor network for urban traffic information acquisition is proposed. The hybrid communication modes include CAN, ZigBee and Ethernet, which can satisfy the requirements of wired and wireless, real-time and massive data transmission. The various kinds of nodes and the prototype sensor network were developed and deployed in Beijing. The test results show the architecture, hybrid communication mode, various sensor nodes and the sensor network proposed in the paper are practical and feasible. This kind of sensor network can be used in traffic surveillance to resolve the problems of present information acquisition.

Comprehensive Performance Evaluation of VANETs for Safety-Related Applications

Abstract In vehicular ad hoc networks (VANETs), broadcast communication is an effective approach to disseminate the safety-related messages to inform the neighboring vehicles. However, the characteristics of broadcast environments lead to poor reliability of the messages. This paper focuses on the comprehensive evaluation to investigate the performance of the safety-related applications, from which we could obtain the optimum performance and ensure quality of service of VANETs. The proposed comprehensive evaluation scheme comprises three parts, with the first applying an analytic hierarchy process (AHP) to decide the relative weights of access categories according to the user preferences, i.e. safety-related applications; the second using the entropy and its combination with AHP to determine the weights of performance metrics; and the third adopting the grey relation analysis to rank the alternatives. The analysis results show that the proposed comprehensive evaluation scheme can obtain the optimum performance and also effectively investigate on capabilities and constraints of VANETs.

Safety applications modeling methodology and performance optimization in road vehicle communication

For the safety applications in road vehicle communication, the existing research did not take it into account that the generation of the safety messages is event driven and the network traffic is self-similar. We propose an ON/OFF Pareto process based safety application self-similar model according to the above features and prove the effectiveness of this model analytically. Then we verify the model on NS2 simulation platform by showing the network traffic generated by our model is self-similar. At last, we use this model to simulate and analyze the performance of safety applications (adopting IEEE 802.11p) by computing the average delay and packet delivery ratio (PDR) with different vehicle densities, speeds and packets generation rates. The simulation results show that IEEE 802.11p can be used for safety applications in road vehicle communication. We also find the optimal working range for safety applications on vehicle density and packets generation rate except vehicle speed, which shows that we must make compromises between short delay and high packet delivery ratio. The conclusion is highly valued for safety applications applied in actual environment.

Reliability and Real-Time Analysis of Safety-Related Messages in VANET

In vehicular ad hoc network (VANET), IEEE 802.11p protocol has been adopted for transmitting the information through vehicle-to-vehicle and vehicle-to-infrastructure communication. Due to the dynamic topology and the real-time constraints, broadcast is an effective approach to deliver the safety-related messages. The reliability and real-time analysis of the safety-related messages can make better decisions on the adaptation and improvement of the standard. In this paper, a Markov chain model has been proposed to investigate the broadcast performance of IEEE 802.11p with two access categories (ACs). Based on the proposed model, closed form expressions, such as packet delivery ratio (PDR) and total delivery delay are derived, taking different ACs, hidden terminal problem and frozen mechanism into account. The obtained numerical results can be used to determine a good tradeoff between the implementation and the network parameters and also help to analyze the capabilities and limitations of the standard.

A pollution monitoring system with hybrid wireless transmission

This paper presents an on-line pollution monitoring system to gather the real time information of the pollutant emission for the railway system which is complicated and extensively distributed. The developed system consists of monitoring nodes, sink nodes, a data center and the communication network. Interface for multiple kinds of detectors is included in the monitoring nodes. Both the separately and intensively deployed monitoring scenarios are considered, utilizing ZigBee and GPRS respectively for short range and long distance transmission. The monitoring data are presented to the Web users by the data center which acts as both a data server and a Web server. Deployment and test of the system has shown its capability and stability to automatically detect, transmit, process and present the information of pollution in the railway system to the users in real time.