Sponser: National Science Foundation – NeTS Core Program (NSF-NeTS)
PI(s): Dr. Wenye Wang and Dr. Min Song
Duration: October 2015 – September 2019
Scope of the project
Vehicular networks have been playing an increasingly important role in promoting mobile applications, driving safety, network economy, and people’s daily life. In this project, a systematic investigation of vehicular networking properties, which is so called ontology of inter-vehicle communications, will be carried out to acquire in-depth scientific understanding and engineering guidelines that are critical to achieving theoretical performance limits and desirable services. We hope the results of this research can advance the knowledge of opportunistic communications and facilitate engineering practice for much-needed applications in vehicular environments.

Why Vehicular Networks?
It is predicted that there will be over 50 million self-driving cars on the road by 2035; the sheer number and density of vehicles have provided non-negligible resources for computing and communication in vehicular environments. In addition, vehicular communications are also driven by the demands and enforcement of intelligent transportation system (ITS) and standardization activities on DSRC and IEEE 802.11p/WAVE.

Many applications, either time-sensitive or delay-tolerant have been proposed and explored, such as cooperative traffic monitoring and control, and recently exChunstended for blind crossing, prevention of collision, real-time detour routes computation, and many others as defined by Car2Car Communication Consortium (C2CCC). Along with the popularity of (smart) mobile devices, there is also an explosion of mobile applications in various categories, including terrestrial navigation, mobile games, and social networking, through Apple’s App store, Google Play, and Windows phonestore etc. Each aforementioned application seemingly is well-suited for either vehicle-to-vehicle (V2V) ad hoc networks or vehicle-to-infrastructure (V2I) communications.

Technical Impact
We studied the performance analysis and protocol design for cognitive-radio enabled vehicle networks. While we focused on using 4G-LTE cellular systems to assist content sharing in vehicular networks, our approach to studying how to share content among vehicles that may have frequent link breakage and connectivity, can be applied to generic wireless networks with dynamic spectrum access and information delivery over wireless and wired networks in reality. In particular, we studied how likely a user can fetch the requested content from its nearby devices (e.g., hit ratio) and how many users can fetch the requested content from a nearby provider (e.g., sharing capacity). Moreover, we studied how to use road infrastructures to improve message coverage in 2-D environments, e.g., urban areas. Considering that vehicle density is inhomogeneous, we initially investigated the coverage of message for V2V networks by deriving analytical bounds of message dissemination distance for areas with different densities of vehicles. We then employed the obtained upper bounds to obtain the message coverage for a set of connected components of vehicles, and further to the optimal placement problem of Road Side Units (RSUs) under budget constraints. Therefore, our approach and results can greatly beneficial to vehicular networks, and even general cyber-physical systems over dynamic spectrum access networks.

Educational Activities
We have been actively involved in curriculum development and devoted significant efforts to attract students from minority and underrepresented students. PI Wang integrated the research results in a graduate course, Introduction to Wireless Networking, in the areas of algorithms design, topology control, system optimization, spectrum sensing and monitoring; PI Song has been advising one female M.S. student working on this project, and recently recruited one female undergraduate student and has been directing her on an Independent Study in the areas of vehicle network simulations and performance analysis. PI Song also supported two undergraduate students to attend the Grace Hopper conference in September 2017. As a faculty representative in Council on the Status of Women in NC State, PI Wang has teamed undergraduate students in the past two years, including two female and one African-American student. The PIs have also participated K-12 extension activities, such as meeting with talented high school students Open House to broaden the impact of the project on autonomous and connected vehicles in particular, and wireless and mobile technologies in general.

Objectives
In this project, a systematic investigation of vehicular networking properties, which is so called ontology of inter-vehicle communications, will be carried out to acquire in-depth scientific understanding and engineering guidelines that are critical to achieving theoretical performance limits and desirable services.

Updates (in progress)
Content Sharing in Cellular-Assisted V2V Communications
In vehicular communications, to mitigate the pressure on cellular networks as well as to adapt to vehicles on the move, content sharing through cellular-assisted V2V communications emerge to be a preferred means for mobile data traffic offloading. Our objective is to demystify the opportunities that emerge from cellular-assisted V2V communications for content sharing applications through analysis of content distribution, content fetching probability and sharing capacity.

By both analytical and simulation results, we find that i)there exists temporal and spatial locality of content popularity; ii) content can be opportunistically fetched from near-close devices through cellular-assisted V2V communications, which is significantly impacted by content popularity, delay tolerance, caching time, device storage and user contact duration; iii) the number of copies of content is an exponential or a power law function of content popularity under constant time caching and recency-based caching policies, respectively; iv) content sharing through V2V communication is especially beneficial for popular content and delay-tolerance requests, otherwise it achieves little success for less popular content.

Theoretical limits of the coverage of messages in V2V and V2Inetworks
RSUs deployed along the roadside assist in connectivity and routing to achieve highly reliable transmissions. However, deploying enough RSUs to provide a full coverage is not feasible at the initial stage of VANETs due entirely to the considerable cost of their placement and maintenance. Therefore, it is essential to study how to optimally utilize roadside units (RSUs) based on the objective of message coverage maximization in an urban environment. We formulate it into a message coverage maximization problem and designed a a forwarding disseminator selection algorithm for infrastructure-based vehicular networks (FDS-I).

We first prove that the problem of optimal placement of RSUs is NP-hard. Then, we introduce a mechanism called Message Coverage Maximization (MCM) to solve the problem. Lower bounds of the message dissemination distance for qunit square are derived for different densities of vehicles, which reveals the coverage area of messages using V2V network. Then a component’s message coverage algorithm (MCCA) to locally find the regions tha tcan be relatively covered by the components of vehicles. With the regions as input, a heuristic algorithm is proposed to find the optimal positions of RSUs deployment to maximize the message coverage area.

Conference Publications
A. Jalooli, K. Zhang, M. Song, and W. Wang, “A Novel Clustering Scheme for Heterogeneous Vehicular Networks,” submitted to IEEE ICC, 2020. (This NSF grant is acknowledged).

Rui Zou and Wenye Wang, “Change Detection Based Segmentation and Modeling of LTE Spec- trum Tenancy,” in Proceedings of 2019 IEEE Global Communications Conference: Cognitive Radio and AI-Enabled Network Symposium (Globecom2019 CRAEN), Waikoloa, USA, Dec. 2019.

A. Adebayo, D.B. Rawat, L. Ni, and M. Song, “Group-Query-as-a-Service for Secure Low- Latency Opportunistic RF Spectrum Access in Mobile Edge Computing Enabled Wireless Networks,”Proc. of the International Conference on Computer Communication and Networks (ICCCN), Aug. 2018. (This NSF grant is acknowledged).

Sigit Pambudi, Wenye Wang, and Cliff Wang, “Fast Rendezvous for Spectrum-Agile IoT Devices with Limited Channel Hopping Capability,” in Proc. of IEEE INFOCOM, April 2018. (This NSF grant is acknowledged)

Sigit Pambudi, Jie Wang, Wenye Wang, Min Song, and Xiaoyan Zhu, “The Aftermath of Broken Links: Resilience of IoT Systems from A Networking Perspective,” in Proc. of IEEE ICCCN, August 2018. (This NSF grant is acknowledged)

Li Gou, Xiaohua Xu, Chongqing Zhang, and Min Song, “Guaranteed Rendezvous for Cognitive Radio Networks Based on Cycle Length,” Proc. of IEEE/CIC International Conference on Communications in China (ICCC), Oct. 2017. (This NSF grant is acknowledged).

Ali Jalooli, Min Song, Xiaohua Xu, “Delay Efficient RSU Placement Algorithm for VANET Safety Applications,” Proc. of the 2017 IEEE Wireless Communications and Networking Conference (WCNC), March 2017.

Sigit Pambudi, Wenye Wang, and Cliff Wang, “On The Resilience of D2D-based Social Networking Service Against Random Failures,” Proc. of IEEE GLOBECOM, December 2016.

Sigit Pambudi and Wenye Wang, “Modeling and Estimating the Structure of D2D-Based Mobile Social Networks,” Proc. of IEEE ICC, May 2016.

Sigit Pambudi, Wenye Wang, and Cliff Wang, “How Robust Is A D2D-Based Messaging Service?” Prof. IEEE GLOBECOM, December 2016.

Journal Publications
A. Jalooli, M. Song, and W. Wang, “Message Coverage Maximization in Infrastructure-Based Urban Vehicular Networks,” Elsevier Vehicular Communications, April 2019. DOI: https://doi.org/10.1016/j.vehcom.2019.02.001. (This NSF grant is acknowledged).

C. Xin, P. Paul, M. Song, and Q. Gu, “On Dynamic Spectrum Allocation in Geo-location Spectrum Sharing Systems,” IEEE Transactions on Mobile Computing, April 2019. DOI: 10.1109/TMC.2018.2848250. (This NSF grant is acknowledged).

J. Wang, S. Pambudi, W. Wang, M. Song, “Resilience of IoT Systems Against Edge-induced Cascade-of-Failures: A Networking,” IEEE Internet of Things Journal, Apr., 2019.

D. Rawat, R. Alsabet, C. Bajracharya, and M. Song, “On the Performance of Cognitive Internet-of-Vehicles with Unlicensed User Mobility and Licensed User Activity,”Elsevier Computer Networks, Apr. 2018. (This NSF grant is acknowledged).

Ali Jalooli, Min Song, and Wenye Wang, “Message Coverage Maximization in Infrastructure-Based Urban Vehicular Networks,” accepted to Elsevier Vehicular Communications. (This NSF grant is acknowledged).

Sigit Pambudi, Wenye Wang, and Cliff Wang, “How to Reach the Cloud in Mobile Networks?” In preparation for submission to IEEE Transactions of Wireless Communications, December, 2018. (NSF grant will be acknowledged).