Towards Scalable Beaconing in VANETs

Beaconing is envisioned to build a cooperative awareness in future intelligent vehicles, from which many ITS applications can draw their inputs. The problem of scalability has received ample attention over the past years and is primarily approached using power control methods. We reason power control alone will not be sufficient if we are to meet application requirements; the rate at which beacons are generated must also be controlled. Ultimately, adaptive approaches based on actual channel and traffic state can tune MAC and beaconing properties to optimal values in the dynamic VANET environment

Approximation of the IEEE 802.11p standard using commercial off-the-shelf IEEE 802.11a hardware

IEEE 802.11p hardware is hard to find. Previous research efforts often relied on project-specific prototype implementations which are characterized by a high cost and are not always available to the entire research community. Commercially available turnkey implementations are rare and quite expensive compared to commercial of-the-shelf (COTS) IEEE 802.11a/b/g hardware. However, the difference between the IEEE 802.11p amendment and the other IEEE 802.11 standards is quite small. It can be seen as a combination of the IEEE 802.11a and IEEE 802.11e standards, with some specific adjustments. This paper presents how an approximation of the IEEE 802.11p standard can be implemented using COTS IEEE 802.11a hardware and some specific software adjustments. This way, vehicular test infrastructures can be established in a much more cost effective manner, and existing IEEE 802.11 wireless testbeds can be used to support VANET research

A density-based contention window control scheme for unicast communications in vehicular ad hoc networks

[EN] Achieving a well-designed medium access control (MAC) protocol is a challenging issue to improve communications efficiency due to the dynamic nature of vehicular ad hoc networks (VANETs). IEEE 802.11p standard was selected as the best choice for vehicular environments considering its availability, maturity, and cost. The common problem in all IEEE 802.11 based protocols is scalability, exhibiting performance degradation in highly variable network scenarios. Experimental results for the IEEE 802.11-based MAC protocol show the importance of contention window adjustment on communications performance; However the vehicular communications community has not yet addressed this issue in unicast communication environments. This paper proposes a novel contention window control scheme for VANET environments based on estimating the network density, which is then used to dynamically adapt the CW size. Analysis and simulation results showthat our proposal provides better overall performance compared with previous proposals, even in high network density scenarios.This work was supported by the Ministerio de Economía y Competitividad, Programa Estatal de Investigación, Desarrollo e Innovación Orientada a los Retos de la Sociedad, Proyectos I+D+I 2014, Spain, under Grant TEC2014-52690-R.Balador, A.; Tavares De Araujo Cesariny Calafate, CM.; Cano, J.; Manzoni, P. (2017). A density-based contention window control scheme for unicast communications in vehicular ad hoc networks. International Journal of Ad Hoc and Ubiquitous Computing. 24(1-2):65-75. doi:10.1504/IJAHUC.2017.080913S6575241-

Enhancing the Physical Layer in V2V Communication Using OFDM - MIMO Techniques

Vehicular Ad hoc network (VANET) has recently been attracting the attention of researchers as a new technology in the wireless communication system. Vehicle-to-vehicle V2V communication can be considered an important way to help the drivers to satisfy requirements such as less congestion, accident warning, road exploration, etc. The propagation issues such as multipath fading significantly affect the reliability of V2V communication. The goal of this work is to enhance the performance of the physical layer PHY in V2V communication. However, the cellular phone channel has been used to evaluate the possibility of apply it in the vehicular communication V2V. The simulation results observed that the transmitted signal is affected by a multipath fading channel. In order to overcome this problem two techniques are used: Orthogonal Frequency Division Multiplexing (OFDM) technique and Multiple-Input-MultipleOutput (MIMO) diversity technique. The simulation results showed that the OFDM technique overcomes the multipath fading with high transmission power. On the other hand, MIMO diversity technique called Alamouti Space-Time Code for two transmitters and two receivers (MIMO 2x2) is used to improve the error degradation with less transmission power

Cognitive radio-enabled Internet of Vehicles (IoVs): a cooperative spectrum sensing and allocation for vehicular communication

Internet of Things (IoTs) era is expected to empower all aspects of Intelligent Transportation System (ITS) to improve transport safety and reduce road accidents. US Federal Communication Commission (FCC) officially allocated 75MHz spectrum in the 5.9GHz band to support vehicular communication which many studies have found insufficient. In this paper, we studied the application of Cognitive Radio (CR) technology to IoVs in order to increase the spectrum resource opportunities available for vehicular communication, especially when the officially allocated 75MHz spectrum in 5.9GHz band is not enough due to high demands as a result of increasing number of connected vehicles as already foreseen in the near era of IoTs. We proposed a novel CR Assisted Vehicular NETwork (CRAVNET) framework which empowers CR enabled vehicles to make opportunistic usage of licensed spectrum bands on the highways. We also developed a novel co-operative three-state spectrum sensing and allocation model which makes CR vehicular secondary units (SUs) aware of additional spectrum resources opportunities on their current and future positions and applies optimal sensing node allocation algorithm to guarantee timely acquisition of the available channels within a limited sensing time. The results of the theoretical analyses and simulation experiments have demonstrated that the proposed model can significantly improve the performance of a cooperative spectrum sensing and provide vehicles with additional spectrum opportunities without harmful interference against the Primary Users (PUs) activities