A new clustering structure for VANET

The Vehicular Ad-Hoc Network (VANET) paradigm offers the opportunity of extending Intelligent Transport System (ITS) by supporting its applications through vehicle-to-vehicle communications, notably in the areas where the infrastructure is inexistent, in failure, or overloaded. However, the complexity induced by ad hoc network management raises many challenges that have to be solved such as the sharing of bandwidth resources, the limitations on the duration of the connections between the vehicles, and the application-specific quality of service (QoS) requirements. Recently, the Chain-Branch-Leaf clustering scheme (CBL) has been proposed for vehicle-to-vehicle ad hoc routing that combines the information of road configuration, vehicle mobility, and link quality in order to build an efficient clustering connecting the entire VANET through a flexible backbone. This work presents a comparative study between the native Multipoint relaying clustering used in the Optimized Link State Routing (OLSR) and CBL scheme. The results show that CBL reduces significantly the routing traffic overhead compared to native OLSR, thus freeing up more bandwidth for ITS applications and reducing the IP delays for peer-to-peer applications

MIFaaS: A Mobile-IoT-Federation-as-a-Service Model for dynamic cooperation of IoT Cloud Providers

In the Internet of Things (IoT) arena, a constant evolution is observed towards the deployment of integrated environments, wherein heterogeneous devices pool their capacities to match wide-ranging user requirements. Solutions for efficient and synergistic cooperation among objects are, therefore, required. This paper suggests a novel paradigm to support dynamic cooperation among private/public local clouds of IoT devices. Differently from . device-oriented approaches typical of Mobile Cloud Computing, the proposed paradigm envisages an . IoT Cloud Provider (ICP)-oriented cooperation, which allows all devices belonging to the same private/public owner to participate in the federation process. Expected result from dynamic federations among ICPs is a remarkable increase in the amount of service requests being satisfied. Different from the Fog Computing vision, the network edge provides only management support and supervision to the proposed Mobile-IoT-Federation-as-a-Service (MIFaaS), thus reducing the deployment cost of peripheral micro data centers. The paper proposes a coalition formation game to account for the interest of rational cooperative ICPs in their own payoff. A proof-of-concept performance evaluation confirms that obtained coalition structures not only guarantee the satisfaction of the players' requirements according to their utility function, but also these introduce significant benefits for the cooperating ICPs in terms of number of tasks being successfully assigned

Exponential and power law distribution of contact duration in urban vehicular ad hoc networks

Contact duration between moving vehicles is one of the key metrics in vehicular ad hoc networks (VANETs), that critically influences the design of routing schemes and network throughput. Due to prohibitive costs to collect enough realistic contact records, little experimental work has been conducted to study the contact duration in urban VANETs. In this work, we carry out an extensive experiment involving tens of thousands of operational taxis in Beijing city. Based on studying this newly collected Beijing trace and the existing Shanghai trace, we find an invariant characteristic that there exists a characteristic time point, up to which the contact duration obeys an exponential distribution that includes at least 80% of the whole distribution, while beyond which it decays as a power law one. This property is in sharp contrast to the recent empirical data studies based on human mobility, where the contact duration exhibits a power law distribution. Our observations thus provide fundamental guidelines for the design of new urban VANETs’ routing protocols and their performance evaluatio

Optimising message broadcasting in opportunistic networks

[EN] Message Broadcasting in Opportunistic Networks is based on the opportunity of establishing contacts among mobiles nodes for message exchange. Nevertheless, as the amount of information transmitted in a contact is limited by the transmission speed and the contact duration, large messages are less likely to be exchanged, and thus their diffusion is severely limited. Furthermore, these failed transmissions can also lead to an important waste of network resources, since the message transmission is aborted when the contact ends and the message needs to be transmitted again in the next contact. Therefore, in this paper we study the impact that contact duration has on the broadcast of messages, showing that splitting a large message into smaller parts can improve its diffusion. Based on this idea, we propose an extension of the epidemic protocol called Xpread. The efficiency of this protocol mainly depends on how the original message is partitioned. Thus, in order to evaluate the impact and the efficiency of the partition scheme, we have developed an analytical model based on Population Processes, showing that a fixed size partition is the best option, while also providing a simple expression to obtain the optimal size. The Xpread has been evaluated exhaustively using four different mobiles traces, comprising both pedestrian and vehicular scenarios. The results show that the diffusion of large messages is improved up to four times with a slight reduction in the delivery time and overhead, minimising also message forwarding failures.This work was partially supported by the Ministerio de Ciencia, Innovacion y Universidades, Spain, under Grant RTI2018-096384-B-I00; and the Secretaria Nacional de Educacion Superior, Ciencia, Tecnologia e Innovacion del Ecuador (SENESCYT), Ecuador.Chancay-García, L.; Hernández-Orallo, E.; Manzoni, P.; Vegni, AM.; Loscrí, V.; Cano, J.; Tavares De Araujo Cesariny Calafate, CM. (2020). 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