Coalition Formation Games for Distributed Cooperation Among Roadside Units in Vehicular Networks

Vehicle-to-roadside (V2R) communications enable vehicular networks to support a wide range of applications for enhancing the efficiency of road transportation. While existing work focused on non-cooperative techniques for V2R communications between vehicles and roadside units (RSUs), this paper investigates novel cooperative strategies among the RSUs in a vehicular network. We propose a scheme whereby, through cooperation, the RSUs in a vehicular network can coordinate the classes of data being transmitted through V2R communications links to the vehicles. This scheme improves the diversity of the information circulating in the network while exploiting the underlying content-sharing vehicle-to-vehicle communication network. We model the problem as a coalition formation game with transferable utility and we propose an algorithm for forming coalitions among the RSUs. For coalition formation, each RSU can take an individual decision to join or leave a coalition, depending on its utility which accounts for the generated revenues and the costs for coalition coordination. We show that the RSUs can self-organize into a Nash-stable partition and adapt this partition to environmental changes. Simulation results show that, depending on different scenarios, coalition formation presents a performance improvement, in terms of the average payoff per RSU, ranging between 20.5% and 33.2%, relative to the non-cooperative case.Comment: accepted and to appear in IEEE Journal on Selected Areas in Communications (JSAC), Special issue on Vehicular Communications and Network

Cache Invalidation Strategies for Internet-based Vehicular Ad Hoc Networks

Internet-based vehicular ad hoc network (Ivanet) is an emerging technique that combines a wired Internet and a vehicular ad hoc network (Vanet) for developing an ubiquitous communication infrastructure and improving universal information and service accessibility. A key design optimization technique in Ivanets is to cache the frequently accessed data items in a local storage of vehicles. Since vehicles are not critically limited by the storage/memory space and power consumption, selecting proper data items for caching is not very critical. Rather, an important design issue is how to keep the cached copies valid when the original data items are updated. This is essential to provide fast access to valid data for fast moving vehicles. In this paper, we propose a cooperative cache invalidation (CCI) scheme and its enhancement (ECCI) that take advantage of the underlying location management scheme to reduce the number of broadcast operations and the corresponding query delay. We develop an analytical model for CCI and ECCI techniques for fasthand estimate of performance trends and critical design parameters. Then, we modify two prior cache invalidation techniques to work in Ivanets: a poll-each-read (PER) scheme, and an extended asynchronous (EAS) scheme. We compare the performance of four cache invalidation schemes as a function of query interval, cache update interval, and data size through extensive simulation. Our simulation results indicate that the proposed schemes can reduce the query delay up to 69% and increase the cache hit rate up to 57%, and have the lowest communication overhead compared to the prior PER and EAS schemes

Cache Invalidation Strategies for Internet-based Vehicular Ad Hoc Networks

Internet-based vehicular ad hoc network (Ivanet) is an emerging technique that combines a wired Internet and a vehicular ad hoc network (Vanet) for developing an ubiquitous communication infrastructure and improving universal information and service accessibility. A key design optimization technique in Ivanets is to cache the frequently accessed data items in a local storage of vehicles. Since vehicles are not critically limited by the storage/memory space and power consumption, selecting proper data items for caching is not very critical. Rather, an important design issue is how to keep the cached copies valid when the original data items are updated. This is essential to provide fast access to valid data for fast moving vehicles. In this paper, we propose a cooperative cache invalidation (CCI) scheme and its enhancement (ECCI) that take advantage of the underlying location management scheme to reduce the number of broadcast operations and the corresponding query delay. We develop an analytical model for CCI and ECCI techniques for fasthand estimate of performance trends and critical design parameters. Then, we modify two prior cache invalidation techniques to work in Ivanets: a poll-each-read (PER) scheme, and an extended asynchronous (EAS) scheme. We compare the performance of four cache invalidation schemes as a function of query interval, cache update interval, and data size through extensive simulation. Our simulation results indicate that the proposed schemes can reduce the query delay up to 69% and increase the cache hit rate up to 57%, and have the lowest communication overhead compared to the prior PER and EAS schemes

Road-side units operators in competition: A game-theoretical approach

International audienceWe study the interactions among Internet providers in vehicular networks which offer access to commuters via road side units (RSUs). Namely, we propose a game-theoretical framework to model the competition on prices between vehicular Internet providers to capture the largest amount of users, thus selfishly maximizing the revenues. The equilibria of the aforementioned game are characterized under different mobile traffic conditions, RSU capabilities and users requirements and expectations. In particular, we also consider in the analysis the case where mobile users modify the price they accept to pay for the access as the likeliness of finding an access solution decreases. Our game-theoretical analysis gives insights on the outcomes of the competition between vehicular Internet providers, further highlighting some counter-intuitive behaviors; as an example, comparing with the case when users have constant price valuation over time, having users inclined to increasing their "acceptable" price may force vehicle Internet providers to charge lower prices due to competition

Cars as roadside units: a selforganizing network solution

Abstract Deploying Roadside Units (RSUs) for increasing the connectivity of vehicular ad hoc networks is deemed necessary for coping with the partial penetration of Dedicated Short Range Communications (DSRC) radios into the market at the initial stages of DSRC deployment. Several factors including cost, complexity, existing systems, and lack of cooperation between government and private sectors have impeded the deployment of RSUs. In this paper, we propose to solve this formidable problem by using a biologically inspired self-organizing network approach whereby certain vehicles serve as RSUs. The proposed solution is based on designing local rules and the corresponding algorithms that implement such local rules. Results show that the proposed approach can increase the message reachability and connectivity substantially

Study on vehicular network application and simulation

VANET is an emerging mobile ad hoc network paradigm that facilitates vehicle-to-vehicle and vehicle-to-infrastructure communication. The most important application of the VANET is for driving safety. Road condition-awareness is critical for driving safety. Existing VANET-based systems usually assume drivers detect and report safety related road conditions, which however may be untrue because, drivers may not be willing to perform these duties, or such duties may distract drivers and thus make driving even unsafe. Therefore, automatic detection without human intervention is desired. As the first contribution of this thesis work, an automatic road condition detection system has been designed based on the idea of collecting and analysing the footprints of vehicles to infer anomaly. It has also been studied how to utilize inexpensive roadside devices, such as sensors, to facilitate the information collection and analysis, especially in the absence of connectivity between vehicles. Due to the difficulty of conducting large-scale experiments on real roads, simulation plays an important role in VANET research. To make simulation close to the reality, it is desired to include detailed and realistic simulation of vehicle behaviour under various road conditions, and this is especially needed for studies targeted at driving safety. In the past, however, the simulation of vehicle behaviours are often overly simplified and implemented as a trivial extension of the network simulator. As a second contribution of this thesis work, a detailed and realistic simulator of vehicle behaviour has been developed based on the car-following and lane-changing models. As the simulation of vehicle behaviour and that of communication behaviour are different tasks, they should be implemented separately for better modularity and meanwhile they should be seamlessly integrable. As another contribution of this thesis work, the online and seamless integration of vehicle behaviour simulator and network simulator has been studied. Specifically, a set of APIs has been designed and implemented atop the vehicular behaviour simulator to facilitate its integration with network simulator. Being a concrete example, the integration of ns2 and SUMO, an open-source vehicular behaviour simulator, has been implemented, and applied to simulate an electric vehicular network

DORA: Dynamic Optimal Random Access for Vehicle-to-Roadside Communications

Abstract-In this paper, we study random access in a drivethru scenario, where roadside access points (APs) are installed on a highway to provide temporary Internet access for vehicles. We consider vehicle-to-roadside (V2R) communications for a vehicle that aims to upload a file when it is within the APs' coverage ranges, where both the channel contention level and transmission data rate vary over time. The vehicle will pay a fixed amount each time it tries to access the APs, and will incur a penalty if it cannot finish the file uploading when leaving the APs. First, we consider the problem of finding the optimal transmission policy with a single AP and random vehicular traffic arrivals. We formulate it as a finite-horizon sequential decision problem, solve it using dynamic programming (DP), and design a general dynamic optimal random access (DORA) algorithm. We derive the conditions under which the optimal transmission policy has a threshold structure, and propose a monotone DORA algorithm with a lower computational complexity for this special case. Next, we consider the problem of finding the optimal transmission policy with multiple APs and deterministic vehicular traffic arrivals thanks to perfect traffic estimation. We again obtain the optimal transmission policy using DP and propose a joint DORA algorithm. Simulation results based on a realistic vehicular traffic model show that our proposed algorithms achieve the minimal total cost and the highest upload ratio as compared with some other heuristic schemes. In particular, we show that the joint DORA scheme achieves an upload ratio 130% and 207% better than the heuristic schemes at low and high traffic densities, respectively. Index Terms-Random access, medium access control, vehicular ad hoc networks, dynamic programming, Markov decision processes, threshold policy

Efficient channel allocation and medium access organization algorithms for vehicular networking

Due to the limited bandwidth available for Vehicular Ad-hoc Networks (VANETs), organizing the wireless channel access to efficiently use the bandwidth is one of the main challenges in VANET. In this dissertation, we focus on channel allocation and media access organization for Vehicle-to-Roadside Units (V2R) and Vehicle-to-Vehicle (V2V) communications. An efficient channel allocation algorithm for Roadside Unit (RSU) access is proposed. The goal of the algorithm is to increase system throughput by admitting more tasks (vehicles) and at the same time reduce the risk of the admitted tasks. The algorithm admits the new requests only when their requirements can be fulfilled and all in-session tasks\u27 requirements are also guaranteed. The algorithm calculates the expected task finish time for the tasks, but allocates a virtual transmission plan for the tasks as they progress toward the edges of the RSU range. For V2V mode, we propose an efficient medium access organization method based on VANETs\u27 clustering schemes. In order to make this method efficient in rapid topology change environment like VANET, it\u27s important to make the network topology less dynamic by forming local strongly connected clustering structure, which leads to a stable network topology on the global scale. We propose an efficient cluster formation algorithm that takes vehicles\u27 mobility into account for cluster formation. The results of the proposed methods show that the wireless channel utilization and the network stability are significantly improved compared to the existing methods

DESIGN OF EFFICIENT IN-NETWORK DATA PROCESSING AND DISSEMINATION FOR VANETS

By providing vehicle-to-vehicle and vehicle-to-infrastructure wireless communications, vehicular ad hoc networks (VANETs), also known as the “networks on wheels”, can greatly enhance traffic safety, traffic efficiency and driving experience for intelligent transportation system (ITS). However, the unique features of VANETs, such as high mobility and uneven distribution of vehicular nodes, impose critical challenges of high efficiency and reliability for the implementation of VANETs. This dissertation is motivated by the great application potentials of VANETs in the design of efficient in-network data processing and dissemination. Considering the significance of message aggregation, data dissemination and data collection, this dissertation research targets at enhancing the traffic safety and traffic efficiency, as well as developing novel commercial applications, based on VANETs, following four aspects: 1) accurate and efficient message aggregation to detect on-road safety relevant events, 2) reliable data dissemination to reliably notify remote vehicles, 3) efficient and reliable spatial data collection from vehicular sensors, and 4) novel promising applications to exploit the commercial potentials of VANETs. Specifically, to enable cooperative detection of safety relevant events on the roads, the structure-less message aggregation (SLMA) scheme is proposed to improve communication efficiency and message accuracy. The scheme of relative position based message dissemination (RPB-MD) is proposed to reliably and efficiently disseminate messages to all intended vehicles in the zone-of-relevance in varying traffic density. Due to numerous vehicular sensor data available based on VANETs, the scheme of compressive sampling based data collection (CS-DC) is proposed to efficiently collect the spatial relevance data in a large scale, especially in the dense traffic. In addition, with novel and efficient solutions proposed for the application specific issues of data dissemination and data collection, several appealing value-added applications for VANETs are developed to exploit the commercial potentials of VANETs, namely general purpose automatic survey (GPAS), VANET-based ambient ad dissemination (VAAD) and VANET based vehicle performance monitoring and analysis (VehicleView). Thus, by improving the efficiency and reliability in in-network data processing and dissemination, including message aggregation, data dissemination and data collection, together with the development of novel promising applications, this dissertation will help push VANETs further to the stage of massive deployment