Accurately determining the geographic location of an Internet host is important for location-aware applications such as location-based advertising and network diagnostics. Despite their fast response time, widely used database-driven geolocation approaches provide only inaccurate locations. Delay measurement based approaches improve the estimation accuracy but still suffer from a limited precision (about 10 km) and a long response time (tens of seconds) to localize a single PC, which cannot meet the demand of precise and real-time geolocation for locationaware applications. In this paper, we propose a new geolocation approach, Checkin-Geo, which exploits geolocation resources fundamentally different from existing database-driven (using DNS, Whois, etc.) or network delay measurement based approaches. In particular, we leverage the location data that users are willing to share in location-sharing services and logs of user logins from PCs for real-time and accurate geolocation. Experimental results show that compared to existing geolocation techniques, Checkin-Geo achieves 1) a median estimation error of 799 meters (an order of magnitude smaller than existing approaches), and 2) a negligible response time, which are promising for accurate location-aware applications.

Due to the distributed and dynamic characteristics of the Internet of Vehicles (IoV) and the continuous growth in the number of devices, content-centric decentralized vehicular named data networking (VNDN) has become more suitable for content-oriented applications in IoV. However, the existing centralized architecture is prone to the failure of single points, which results in trust problems in key verification between cross-domain nodes and consuming more power and reducing the lifetime. Focusing on secure key management and power-efficient routing, this article proposes a blockchain-based key management and green routing scheme for VNDN. A blockchain-based key management scheme is presented to achieve secure and efficient distribution and verification of keys. Specifically, all trusted agencies (TAs) form a consortium blockchain for storing public key hashes to ensure the authenticity of users’ public keys. A green global routing scheme based on node relaying pressure (GGNRP) is proposed to save power consumption and reduce the forwarding delay. A new node relay pressure metric is introduced to assist with routing decisions. Detailed experiments and analysis show that, compared with the existing scheme, the proposed scheme can achieve secure key management and GGNRP can decrease the power consumption and average delay by 15.8% and 63.2%, respectively.

In order to reduce traffic conflicts on cross-intensive roads, this paper proposes a new early warning system based on the active safety concept. The system collects real-time vehicle data using roadside sensors and transmits the results to drivers on the major road in a timely manner via roadside warning lights. In this research, the principles of the warning system are discussed in detail, including how the vehicle dynamics data are collected and how potential collisions are identified and avoided. Through a driving simulation experiment, the speed prediction model after implementation of the warning system was examined. Results indicated that it can accurately identify the vehicle operating status, accurately guide driving behavior, and effectively reduce traffic conflict. To verify the reliability of the proposed warning logic and algorithm, numerical simulations were carried out via CarSim/Simulink cosimulation. The simulation results indicate that the proposed system enables drivers to perceive conflicting vehicles in advance, avoid the sudden braking phenomenon, and ensure safe driving.

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