Reliable safety message dissemination is a fundamental primitive for constructing intersection safety systems. Normally, the dissemination is based on vehicular communications, of which the de-facto standard is Dedicated Short Range Communications (DSRC). However, due to high frequency operations, a DSRC signal is seriously attenuated when being propagated in Non Line-Of-Sight (NLOS) conditions. Previous schemes leveraged the use of centralized infrastructures or relay vehicles enabling a safety message to bypass large obstacles. However, implementing the infrastructures in all intersections would be very costly; one may not find proper relay vehicles in low density, and frequent rebroadcasts cause serious network congestion in high density. To address this challenge, we propose a novel scheme that exploits excellent propagation characteristics of a TV White Space (TVWS) band (in addition to a DSRC band) for reliable dissemination in NLOS intersections. To ensure reliable dissemination throughout a broad range of densities without infrastructures, our scheme employs two innovative mechanisms: a collaborative procedure and a Dynamic optimal Configuration (DoC). To our knowledge, this is the first that simultaneously satisfies two vital demands for intersection safety system: 1) lacking infrastructures and 2) working well in all densities. Simulation studies show that the proposed scheme outperforms previous infrastructure-based schemes.

In wireless networks, broadcasting is a fundamental communication primitive for network management and information sharing. However, in multichannel networks, broadcast efficiency is very poor as devices are distributed across various channels. Thus, a sender tries all channels to broadcast a single message, causing large overhead. In this paper, we propose a novel, drastically different scheme for efficient broadcast in multichannel networks. Our scheme leverages an overlapped band of adjacent channels, which is the frequency range that partially overlapped channels share within their channel boundaries. Specifically, a sender advertises a rendezvous channel through the overlapped band of adjacent channels; message sharing is done on the rendezvous channel. Our scheme employs signaling via overlapped band (SOB), which defines a new signal processing mechanism for communication via the overlapped band. SOB is integrated with the following Multiple Access Control (MAC) layer mechanisms: 1) Reserve idle spectrum fragment to reduce waiting time, 2) multisender agreement on rendezvous channel to support multisender broadcasts, and 3) reinforce switch notification to reduce the residing time at a wrong channel. Our scheme can also be integrated with two remarkably simple but efficient mechanisms for improving the packet delivery ratio and reducing delay in a multiple contention domain. We implemented our scheme on the SORA software radio platform. Experimental results validated communication through the overlapped band. Intensive simulation studies showed that our scheme dramatically outperformed a previous approach.

As the capabilities for vehicular communications have become widespread, periodic beaconing is becoming fundamental to tracking neighbors. Specifically, a vehicle periodically broadcasts its kinematic data and receivers estimate the sender's evolving position. To ensure safety, tracking neighbors via beaconing requires position errors and transmission delay to be small. To satisfy stringent requirements, previous proposals have employed multiple RF devices based on the unrealistic assumption that vehicles have the same type of RF devices. In reality, vehicles possess different RF devices (heterogeneous vehicle conditions). Satisfying the requirements under heterogeneous conditions is challenging because network connectivity is low and multi-hop transmissions to improve the connectivity aggravate network congestion. To address this challenge, we propose a novel scheme using a model-based trajectory prediction and multi-hop transmissions adaptively. To maintain accuracy of the model, each vehicle creates a model for predicting its own trajectory and distributes the model. For reliable multi-hop transmissions, our scheme employs Periodic Scan for Translator & disconnected Neighbors (PSTN) and Probabilistic Relay (PR). To our knowledge, this is the first to consider heterogeneous vehicle conditions for tracking neighbors via beaconing. Evaluation confirms that our scheme tracks neighbors more accurately than previous work.

This paper proposes a continuous identification scheme monitoring a driver's behavior and a detection scheme for an impostor. The proposed scheme uses Long Short-Term Memory (LSTM) to create a classifier of the driver's behavior according to acceleration data and classifies a driver. Additionally, it also detects an impostor according to statistical information of output from the classifier. Experimental results show that an acceleration sensor on a real vehicle is enough to classify 15 drivers according to real-time driver's behavior. Additionally, the proposed scheme can detect an impostor through the verification of real experimental data.