Weiwen Deng

Modeling and simulating traffic congestion propagation in connected vehicles driven by temporal and spatial preference

Differing from the traditional traffic, connected vehicles enable information sharing between vehicles at vicinity to facilitate cooperative path planning, which may positively affect the congestion propagation process. In this paper, we propose to modeling and simulating traffic congestion propagation in such new situation where the path planning is driven by a temporal or spatial preference with aims at investigating the effects of various factors on traffic congestion, e.g. traffic light, mobility pattern, traffic density and communication radius. Simulations show that the traffic congestion is indeed affected by the concerned factors; however, the traffic congestion fails to be mitigated persistently as the communication radius increases beyond a certain threshold. The result is helpful for understanding the traffic congestion propagation in connected vehicles.

The Joint Adaptive Kalman Filter (JAKF) for Vehicle Motion State Estimation

This paper proposes a multi-sensory Joint Adaptive Kalman Filter (JAKF) through extending innovation-based adaptive estimation (IAE) to estimate the motion state of the moving vehicles ahead. JAKF views Lidar and Radar data as the source of the local filters, which aims to adaptively adjust the measurement noise variance-covariance (V-C) matrix ‘R’ and the system noise V-C matrix ‘Q’. Then, the global filter uses R to calculate the information allocation factor ‘β’ for data fusion. Finally, the global filter completes optimal data fusion and feeds back to the local filters to improve the measurement accuracy of the local filters. Extensive simulation and experimental results show that the JAKF has better adaptive ability and fault tolerance. JAKF enables one to bridge the gap of the accuracy difference of various sensors to improve the integral filtering effectivity. If any sensor breaks down, the filtered results of JAKF still can maintain a stable convergence rate. Moreover, the JAKF outperforms the conventional Kalman filter (CKF) and the innovation-based adaptive Kalman filter (IAKF) with respect to the accuracy of displacement, velocity, and acceleration, respectively.

Image-based modeling and simulating physical channel for vehicle-to-vehicle communications

Abstract Vehicle-to-vehicle (V2V) communication systems have received ever-increasing attention since IEEE 802.11p is proposed and approved. The scenarios in V2V communication are quite different from that in traditional wireless communications, e.g. short-lived link holding time, high-speed motion of transmitters and receivers, and low height of antennas. Due to these significant differences, V2V wireless channels are characterized by distinctive spatial as well as temporal impulse responses. From perspective of geometrical optics theory, the paper proposes to comprehensively model V2V physical channel and integrate the proposed models with CarSim and Simulink in order to obtain necessary scenario parameters in real time. A series of traffic and environmental models, including vehicle, road, building, tree, and weather are presented in this paper. Moreover, image method is used to determine potential wave propagation paths consisting of line-of-sight, reflections, diffractions, scatterings and their combinations. Furthermore, typical and prime channel characteristics such as impulse response and average received power are analyzed theoretically, which drive the subsequent V2V communication simulations under various combinations of traffic situation and network scenario.

Non-cooperative game of effective channel capacity and security strength in vehicular networks

Abstract Vehicular ad-hoc networks pose stringent requirements on quality-of-service (QoS) and security strength in parallel because of their open channels and highly dynamic topology. Harmonizing these two conflicting goals is an urgent challenge, especially in VNs that are characterized by restrictive resources, e.g. bandwidth and link lifetime. This paper aims to balance the anticipated QoS and security strength in context to fully utilize limited network and computing resources to attain a satisfactory performance rating without compromising any security. To this end, we use non-cooperative game theory to formulate node utility, synthesizing the channel capacity and security strength from the perspective of adaptively controlling the transmit power and encryption block length in Nakagami multipath fading (NMF) channels. Moreover, we analyze the non-cooperative behavior of a “communication player” in controlling the transmit power and a “security player” in deciding the encryption block length, both of whom together strive to maximize the utility function at minimum cost. We then theoretically derive the pure strategy Nash equilibrium. Extensive numerical calculations are conducted to comprehensively investigate the reaction of the Nash equilibrium against the various combinations of the considered parameters. The results show that the proposed joint optimization method is capable of self-adapting to the vehicular context and improving the communication quality without compromising on security.

Computational Security for Context-Awareness in Vehicular Ad-Hoc Networks

Vehicular ad hoc networks can be viewed as a typical context-aware system where the experienced context frequently varies as vehicles move along road, e.g., signal-to-noise ratio (SNR), velocity, and traffic flow. In particular, the adopted security protection mechanisms often depend on the node state, location, and/or surrounding risk, which need the capability of context-aware security quantification. This paper views the security level as a users inherent property that is only correlated with the users behaviours and the situated context and independent of the suffered attack ways. We propose a formalized methodology to especially quantify the security level in real time from the perspective of state transition probability through estimating the stable probability of staying in the security state in inhomogeneous continuous time Markov chain. This paradigm enables users to customize the security protection mechanisms for adapting to the frequently varying context. We conduct the extensive numerical calculations and empirical analysis to comprehensively investigate the response of the proposed security quantification framework to the various combinations of the concerned parameters, e.g., SNR, velocity, and traffic flow. The results show that the proposed framework is capable of capturing the real-time security level adaptively to the vehicular context and provides a dependable decision basis to security protection, which can restrict the security to a target value.

VIKE: vehicular IKE for context-awareness

Vehicular ad-hoc networks differ from the wired networks and behave in a highly dynamic context, e.g. frequently changing signal-to-noise ratio (SNR) and security risks, which undoubtedly affects the experienced quality-of-service (QoS) and security. In this paper, we propose to dynamically balance the anticipated QoS and security for adapting to the varying vehicular context and the served applications with aims to attain a satisfactory performance rating but without compromising any security. To this end, a variant of IKEv2 called Vehicular Internet Key Exchange (VIKE) is put forward to autonomously negotiate the optimal encryption and integrity algorithms and the related profile that particularly suit to the current context with respect to the confronted SNR, security risk and application requirements. We theoretically derive the relations between the QoS and security for analytical solutions in terms of four categories of vehicular applications. The extensive numerical calculations are conducted to comprehensively investigate how the proposed VIKE responses to the various combinations of the SNR, modulation scheme and key length. The results show that the VIKE is capable of self-adapting to the vehicular context, and of contributing to the quality of communication performance without compromising any security. The proposed VIKE is expected to port the mass-deployed IKE into securing the emerging numerous vehicular applications and services.

Network-layer abstraction and simulation of vehicle communication stack

Vehicular ad-hoc networks (VANETs) display many characteristics that are different from the traditional wireless networks, e.g. the rapidly changing topology and short-lived link. The vehicle communication stack is thus redesigned differently from the traditional TCP/IP architecture in order to accommodate these diversities. The network layer bears the function of the reliable routing and delivery of packets from sources to destinations over a highly dynamic path. We investigate the network layer within the vehicle communication stack and present an abstraction approach, with aims at filling the gap between the simplified and the very detailed models by incorporating more realistic routing protocols and network topologies. We study how the network dynamics, as monitored by multiple network performance indicators (e.g. transmission delay, path length, throughput, and loss rate), is affected by various combinations of routing algorithms, packet sizes, moving speeds, communication ranges, processing rates, boundary conditions, and movement patterns. The proposed suite can be modified and expanded easily to incorporate more features of the real VANET, e.g. traffic light control.

AST: Activity-Security-Trust driven modeling of time varying networks

Network modeling is a flexible mathematical structure that enables to identify statistical regularities and structural principles hidden in complex systems. The majority of recent driving forces in modeling complex networks are originated from activity, in which an activity potential of a time invariant function is introduced to identify agents’ interactions and to construct an activity-driven model. However, the new-emerging network evolutions are already deeply coupled with not only the explicit factors (e.g. activity) but also the implicit considerations (e.g. security and trust), so more intrinsic driving forces behind should be integrated into the modeling of time varying networks. The agents undoubtedly seek to build a time-dependent trade-off among activity, security, and trust in generating a new connection to another. Thus, we reasonably propose the Activity-Security-Trust (AST) driven model through synthetically considering the explicit and implicit driving forces (e.g. activity, security, and trust) underlying the decision process. AST-driven model facilitates to more accurately capture highly dynamical network behaviors and figure out the complex evolution process, allowing a profound understanding of the effects of security and trust in driving network evolution, and improving the biases induced by only involving activity representations in analyzing the dynamical processes.

Performance analysis of prioritized broadcast service in WAVE/IEEE 802.11p

In this paper, we propose a more accurate model to capture the prioritized broadcast service in WAVE/IEEE 802.11p and comprehensively analyze the related performance indicators accordingly. We construct a 2-D Markov chain to characterize the IEEE 802.11p EDCA backoff process and subsequently build a 1-D infinite discrete-time Markov chain to identify the contention period for establishing the relation between the transmission probabilities and the channel state. We also consider the impacts of the multichannel operation defined by IEEE 1609.4 in the modeling. Unlike most previous work, we define the transmission probability as a function of the fluctuating numbers of continuous idle slots, introduce a proactive backoff stage into the 2-D Markov chain to profile the backoff procedure where the transmission queue is empty, and characterize the access delay extension and transmission synchronization caused by channel switching. We perform extensive numerical analyses and investigate the access delay, packet delivery rate, and other performance indicators. The results uncover the relations among the metrics of concern underlying various priority access categories as a function of the experienced traffic loads. The effectiveness of the proposed performance model is faithfully verified by the simulation results.

SAV4AV: securing authentication and verification for ad hoc vehicles

Information exchange is not easily secured in the emergency cases where the normal telecommunication infrastructure might have been collapsed. When vehicles are moving on a highway, communications between the vehicles and the base stations always result in a high delay that causes a vehicle to fail to verify all the messages received from the neighbors in real time. These situations may result in message losses and even security risks. To address these issues, we propose a scheme that combines the technologies of trusted network connect and multi-secret sharing to securing authentication and verification for ad hoc vehicles SAV4AV, in which a new vehicle is permitted to flexibly join in a platoon through collaborating with t existing vehicles and thereby to accomplish identity authentication and integrity verification. We list several possible attacks and provide a detailed security analysis on how to avoid these threats in SAV4AV. Moreover, we perform extensive simulations to investigate the performance of SAV4AV against various network scenarios with respect to time consumption and network throughput. Copyright