Guozhen Tan

A Distributed Threshold Algorithm for Vehicle Classification Based on Binary Proximity Sensors and Intelligent Neuron Classifier

To improve the accuracy of real time vehicle surveillance, utilize the advances in wireless sensor networks to develop a magnetic signature and length estimation based vehicle classification methodology with binary proximity magnetic sensor networks and intelligent neuron classifier. In this algorithm, we use the low cost and high sensitive magnetic sensors to measure the magnetic field distortion when vehicle crosses the sensors and detect vehicle via an adaptive threshold. The vehicle length is estimated with the geometrical characteristics of the proximity sensor networks, and finally identifies vehicle type from an intelligent neural network classifier. Simulation and on-road experiment obtains high recognition rate over 90%. It verified that this algorithm enhances the vehicle surveillance with high accuracy and solid robustness.

Vehicle Classification Algorithm based on Binary Proximity Magnetic Sensors and Neural Network

To improve the classification accuracy, a new algorithm is developed with binary proximity magnetic sensors and back propagation neural networks. In this scheme, we use the low cost and high sensitive magnetic sensors that detect the magnetic field distortion when vehicle pass by it and estimate vehicle length with the geometrical characteristics of binary proximity networks, and finally classify vehicles via neural networks. The inputs to the neural networks are the vehicle length, velocity and the sequence of features vector set, and the output is predefined vehicle category. Simulation and on-road experiment obtains the high recognition rate of 93.61%. It verified that this scheme enhances the vehicle classification with high accuracy and solid robustness.

Traffic Congestion Evaluation and Signal Control Optimization Based on Wireless Sensor Networks: Model and Algorithms

This paper presents the model and algorithms for traffic flow data monitoring and optimal traffic light control based on wireless sensor networks. Given the scenario that sensor nodes are sparsely deployed along the segments between signalized intersections, an analytical model is built using continuum traffic equation and develops the method to estimate traffic parameter with the scattered sensor data. Based on the traffic data and principle of traffic congestion formation, we introduce the congestion factor which can be used to evaluate the real-time traffic congestion status along the segment and to predict the subcritical state of traffic jams. The result is expected to support the timing phase optimization of traffic light control for the purpose of avoiding traffic congestion before its formation. We simulate the traffic monitoring based on the Mobile Century dataset and analyze the performance of traffic light control on VISSIM platform when congestion factor is introduced into the signal timing optimization model. The simulation result shows that this method can improve the spatial-temporal resolution of traffic data monitoring and evaluate traffic congestion status with high precision. It is helpful to remarkably alleviate urban traffic congestion and decrease the average traffic delays and maximum queue length.

Implementation and evaluation of WAVE 1609.4/802.11p in ns-3

Since the IEEE 1609/WAVE standards were published, much research has continued on validation and optimization. However, precise simulation models of these standards are lacking recently, especially within the ns-3 network simulator. In this paper, we present the ns-3 implementation details of the IEEE 1609.4 and IEEE 802.11p standards which are key elements of the WAVE MAC layer. Moreover we discuss some implementation issues and describe our solutions. Lastly, we also analyze and evaluate the performance of the WAVE MAC layer with the implemented model. Our simulation results show that multiple channel operation specified in the WAVE standards could impact vehicular wireless communication differently, depending on the different scenarios, and the results should be considered carefully during the development of VANET applications.

APDM: An adaptive multi-priority distributed multichannel MAC protocol for vehicular ad hoc networks in unsaturated conditions

Abstract Vehicular ad hoc networks (VANETs) employ multichannel to provide a variety of safety and non-safety applications. Safety applications require reliable and timely transmission, while non-safety applications need high network throughput. IEEE 802.11p and IEEE 1609.4 protocol divide the bandwidth into seven channels. One control channel (CCH) is to serve safety applications and the other six service channels (SCHs) to serve non-safety applications. The IEEE 1609.4 protocol specifies an alternating scheme to allow vehicles to switch between two types of applications. However, the IEEE 1609.4 multichannel media access control (MAC) protocol has limitations on its capability of supporting either delay- or throughput-sensitive applications. In this paper, we propose an adaptive multi-priority distributed multichannel (APDM) MAC protocol for VANETs. Considering that in realistic VANETs, the queue of MAC layer is far from saturated. We assume that generated packets with different priorities arrive at the MAC layer in a Poisson manner. A Markov analytical model is conducted to optimize the packet transmission probabilities and adjust the ratio between CCH interval and SCH interval dynamically according to the real-time traffic in a distributed way. An M/M/1 queue model is then adopted to analyze the time performance. Extensive simulation results show that the APDM MAC protocol can ensure prioritized transmission of safety packets, reduce the transmission delay of packets and enhance the unsaturated and saturated throughput of SCHs.

An enhanced XOR-based scheme for wireless packet retransmission problem

Solving wireless packet retransmission problem WPRTP using network coding NC is increasingly attracting research efforts. However, existing NC-based schemes for WPRTP are with high computational complexity resulting from computation on larger Galois field GF2q, or the solutions on GF2 found by the schemes are less efficient. In this paper, combining the basic ideas in two existing schemes, denoted as ColorNC and CliqueNC, respectively, we present a new scheme named as ColorCliqueNC. The advantages of ColorCliqueNC include the following: i it is suitable for all kinds of WPRTP instances; ii it works on GF2; thus, it is computationally efficient than the schemes working on larger Galois fields; and iii the solutions found by ColorCliqueNC usually have fewer packet retransmissions than those by ColorNC and CliqueNC despite that they all work on GF2. Theoretical analysis indicates that ColorCliqueNC is superior to ColorNC and CliqueNC. Simulation results show that ColorCliqueNC generally outperforms ColorNC and CliqueNC. Compared with ColorNC, ColorCliqueNC can save up to 10% packet retransmissions. Copyright

Vehicle Speed Estimation Based on Sensor Networks and Signal Correlation Measurement

This paper proposed a novel method for accurate vehicle speed estimation based on magnetic sensors. The estimation system consists of triple sensors and signals are collected synchronously when vehicles travel over it. Taking into consideration the difference of sensor sensitivity and self-disturbance of Earths magnetic field, a signal correlation model is introduced to improve the measurement precision of vehicle traveling time. Spectrum analysis and correlation model are used to accurately estimate the phase difference of sensor signals. In addition, an efficient clock synchronization algorithm based on active compensation is designed to reduce the time estimation error and enhance the vehicle speed estimation accuracy. Simulation and on-road experiment show that the method introduced in this paper has better performance and robustness than other approaches.

Distributed Algorithm for Traffic Data Collection and Data Quality Analysis Based on Wireless Sensor Networks

The growing need of the real-time traffic data has spurred the deployment of large-scale dedicated monitoring infrastructure systems, which mainly consist of the use of inductive loop detectors. However, the loop sensor data is prone to be noised or even missed under harsh environment. The state-of-the-art wireless sensor networks provide an appealing and low-cost alternative to inductive loops for traffic surveillance. Focusing on the urban traffic data collection, this paper proposes a distributed algorithm to collect the traffic data based on sensor networks and improve the reliability of data by quality analysis. Considering the certain correlated characteristics, this algorithm firstly processes the data samples with an aggregation model based on the mean filter, and then, the data quality is analyzed, and partial bad data are repaired by the cusp catastrophe theory. The performance of this algorithm is analyzed with a number of simulations based on data set obtain in urban roadway, and the comparative results show that this algorithm could obtain the better performance.

An Efficient and QoS Supported Multichannel MAC Protocol for Vehicular Ad Hoc Networks

Vehicular Ad Hoc Networks (VANETs) employ multichannel to provide a variety of safety and non-safety (transport efficiency and infotainment) applications, based on the IEEE 802.11p and IEEE 1609.4 protocols. Different types of applications require different levels Quality-of-Service (QoS) support. Recently, transport efficiency and infotainment applications (e.g., electronic map download and Internet access) have received more and more attention, and this kind of applications is expected to become a big market driver in a near future. In this paper, we propose an Efficient and QoS supported Multichannel Medium Access Control (EQM-MAC) protocol for VANETs in a highway environment. The EQM-MAC protocol utilizes the service channel resources for non-safety message transmissions during the whole synchronization interval, and it dynamically adjusts minimum contention window size for different non-safety services according to the traffic conditions. Theoretical model analysis and extensive simulation results show that the EQM-MAC protocol can support QoS services, while ensuring the high saturation throughput and low transmission delay for non-safety applications.

A novel key generation method for wireless sensor networks based on system of equations

Many key management schemes were proposed for protecting wireless sensor networks (WSNs). While applying key management to the network, it is important to ensure that the efficiency of the network is not greatly affected by key connectivity. Poor connectivity might lead to many messages forwarding. Consequently, a large amount of energy of the involved nodes would be consumed during message forwarding, which is not suitable for the resources-constraint sensor nodes. In this work, we analyze the impact of key connectivity on the efficiency of communication. Then, a novel key generation method based on system of equations is proposed to improve key connectivity of key management. The involved equations are applied to establish secret keys and each node uses these keys for protecting their communication. The system of equations is constructed to have one and only one solution so that the unique solution can also be used to establish a shared hidden key for enhancing the association among nodes. As a result, neighbors can directly communicate with each other through the shared hidden key even though they do not have common keys. To differentiate from normal keys, keys generated by the proposed method are called associated-keys. According to the analyses, we recommend that systems of linear equations (linear systems) instead of systems of polynomial equations are used to realize the proposed method with respect to the computation complexity. Furthermore, we illustrate that linear systems of two variables are sufficient to generate keys for large scale of networks. The Exclusion Basis System (EBS) is used as a instance to illustrate the implementation of key management with associated-keys. The theoretical analyses and simulation results show that key management schemes with associated-keys have better key connectivity than the corresponding schemes with normal keys. Meanwhile, other performance metrics are unaffected.