Barbara M. Masini

IEEE 802.11p for cellular offloading in vehicular sensor networks

The use of vehicles as sensors is a new paradigm to enable an efficient environment monitoring and an improved traffic management. In most cases, the sensed information must be collected at a remote control center and one of the most challenging aspects is the uplink acquisition of data from vehicles, which is presently performed through cellular networks. With the objective to offload cellular networks, in this paper we propose and discuss the adoption of the WAVE/IEEE 802.11p protocols, which represent the state of the art for short range vehicle-to-vehicle and vehicle-to-roadside communications. More specifically, we discuss the system design and assess the cellular resource saving that can be obtained in urban scenarios through the deployment of WAVE/IEEE 802.11p devices on the vehicles and roadside units, evaluating the impact of the percentage of equipped vehicles, of the number of deployed road side units, and of the adopted routing protocol. Results, obtained through an integrated simulation platform taking both realistic vehicular environments and wireless network communication aspects into account, show that the deployment of few road side units and the use of low complexity routing protocols leads to a significant reduction of cellular resource occupation, even approaching 100% with a high density of equipped vehicles.

Performance Analysis of V2V Beaconing Using LTE in Direct Mode With Full Duplex Radios

Vehicles will soon be equipped with wireless communication systems enabling a variety of new services. At the basis of each service is the transmission of beacon messages that advertise the vehicles presence. In this letter, we investigate long term evolution (LTE) as the enabling technology for vehicle to vehicle (V2V) beaconing by exploiting: 1) the direct device to device (D2D) communication provided by Release 12 of LTE; and 2) the full duplex (FD) radio, which allows a wireless device to transmit and receive at the same time. Furthermore, we introduce a novel analytical framework to evaluate the resource occupation of the beaconing service in LTE and compare the results with those obtained using LTE for vehicle to infrastructure (V2I) communications.

On the Frequent Acquisition of Small Data Through RACH in UMTS for ITS Applications

Wireless communications are currently considered the most promising solutions to provide real-time traffic information, suggest alternative routes, and help to reduce congestion. These new services are all based on the real-time acquisition of traffic information directly from vehicles, which act as sensors that travel on the roads. With the idea of having new widespread and real-time infomobility services in the short-medium term, neither installations onboard nor new roadside infrastructures that have been set up can be taken into account. Hence, in this paper, we aim at verifying the feasibility of the real-time acquisition of traffic information from vehicles in dense areas through the universal mobile telecommunication system (UMTS). In particular, we first analytically evaluate the capacity and the coverage of a UMTS cell when multiple users frequently transmit their traffic measurements to a remote control center through a shared (common) channel. Then, we extend our results to a realistic urban scenario by investigating, through simulations, the feasibility of the service and its impact on the quality of service (QoS) perceived by other users (e.g., voice).

On the down-link performance of multi-carrier CDMA systems with partial equalization

This paper addresses the performance evaluation of multi-carrier code division multiple access systems. A partial equalization technique depending on a parameter adapted to different conditions such as the number of sub-carriers, the number of active users and the mean signal-to-noise ratio is evaluated for the down-link. We analytically derive the performance of this system and the value of the equalization parameter that maximizes the performance. The partial equalization technique is shown to have the same complexity of the well known maximal ratio combining, equal gain combining and orthogonality restoring combining techniques, with significative performance improvement. Analytical results are compared with simulations showing a perfect agreement

Bluetooth and IEEE 802.11 coexistence: analytical performance evaluation in fading channel

The performance in terms of the mean packet error probability (PEP) in a Rayleigh fading channel with thermal noise is analytically derived for a Bluetooth transmission interfered by IEEE 802.11b. The methodology proposed carefully takes PHY as well MAC aspects into account. Simulations are used to verify methodology assumptions. Moreover, we derive the coexistence domain, in terms of relative distances between the two systems, for a fixed quality of service, i.e., a target mean PEP.

V2V and V2R for cellular resources saving in vehicular applications

Considering vehicles as sensors for traffic and pollution information is a new paradigm to monitor the environment and to open the way to an efficient smart navigation. In this work we focus on the uplink acquisition of traffic information from vehicles toward a remote control center. With the increase in the number of vehicles equipped with on board units (OBUs) enabling cellular transmissions, this service is leading to higher loads for the cellular network itself and, consequently, to higher costs. In this paper we discuss the opportunity to take advantage of vehicle-to-vehicle (V2V) and vehicle-to-roadside communications in addition to vehicle-to-infrastructure cellular transmissions. The objective is twofold: to investigate the potential reduction of data transmitted over the cellular networks and to verify the potential transmission delay reduction, by sharing and aggregating information through V2V communications. Results are obtained through an integrated simulation platform jointly taking into account both realistic vehicular environments and wireless network communication aspects.

Partial Equalization for MC–CDMA Systems in Non-Ideally Estimated Correlated Fading

Multicarrier code-division multiple access (MC-CDMA) can support high data rates in next-generation multiuser wireless communication systems. Partial equalization (PE) is a low-complexity technique for combining the signals of subcarriers to improve the achievable performance of MC-CDMA systems in terms of their bit error probability (BEP) and bit error outage (BEO) in comparison with maximal ratio combining, orthogonality restoring combining, and equal-gain combining techniques. We analyze the performance of the multiuser MC-CDMA downlink and derive the optimal PE parameter expression, which minimizes the BEP. Realistic imperfect channel estimation and frequency-domain (FD) block-fading channels are considered. More explicitly, the analytical expression of the optimum PE parameter is derived as a function of the number of subcarriers, number of active users (i.e., the system load), mean signal-to-noise ratio (SNR), and variance of the channel-estimation errors for the aforementioned FD block-fading channel. We show that the choice of the optimal PE technique significantly increases the achievable system load for the given target BEP and BEO.

Architecture of a simulation platform for the smart navigation service investigation

Efficient mobility management is an issue of vast economic importance for its consequences on urban and suburban mobility. In this context, telecommunications are gaining a key role, allowing to increase people safety, traffic efficiency, and travel comfort. To investigate the telecommunication systems behavior in new infomobility scenarios, advanced simulations tools are needed jointly taking into account realistic road traffic mobility and telecommunication networks protocols in all their aspects. In this paper we discuss the architecture of a complex and complete simulation platform we are developing on the behalf of the Italian project PEGASUS: the choice of traffic simulators, the network simulation and their interface will be presented and described.

Relay-Assisted Diversity Communications

Relaying and diversity methods improve wireless communications by jointly exploiting the benefits of node cooperation, multiple-channel reception, and distributed processing. We develop a framework for design and analysis of relay-assisted diversity communications accounting for: 1) node positions; 2) link characterization; 3) diversity methods; 4) distributed coding and constellation signaling; and 5) power allocation. The framework is built on a simple model for assessing the frame error probability (FEP) as a function of radio-link characteristics, and it enables a clear understanding of how the aforementioned aspects affect the performance. A novel FEP-optimal power allocation is developed and compared with other allocation techniques such as uniform, destination-balanced (D-balanced), and relay-balanced (R-balanced) power allocations. Results show the effectiveness of the novel power allocation technique for various distributed codings and provide insights into the operation of relay-assisted diversity systems.

Visible light communications as a complementary technology for the internet of vehicles

The paradigm of vehicular visible light network (VVLN) is introduced, highlighting its peculiarities, and discussing the present state of the art focusing on standardization and real experimentations.The limits of visible light communication (VLC) for pure VVLNs are discussed and its potentiality when used as complementary wireless technology is highlighted.An algorithm (called congestion-adaptive VLC-DSRC) is proposed to jointly manage VLC and dedicated short range communications (DSRC) in heterogeneous vehicular networks.Example results of VLC added to DSRC are shown focusing on the example application of crowd sensing vehicular networks (CSVNs) through simulations in realistic urban scenarios. The paradigm of connected vehicles is moving from research to implementation, thus enabling new applications that start from safety improvement and widen to the so called Internet of vehicles (IoV). The candidate enabling technologies in the radio frequency (RF) bands are cellular and short range technologies. However, the limited bandwidth shared among several applications pushes researchers to look at new technological solutions. To this end, an option is provided by visible light communication (VLC). Based on the use of the light emission diodes (LEDs) that are already available on the majority of vehicles, VLC would enable short range communication in large, unlicensed, and uncongested bands with limited costs. In this work we first highlight the main properties of VLC in vehicular networks and revise the state of the art focusing on both the IEEEź802.15.7 standard and on the performance demonstrated by field tests that have been conducted worldwide. Then, we discuss the limitations of using VLC for pure vehicular visible light networks (VVLNs) and its application as complementary technology, to be implemented with other wireless standards in future heterogeneous vehicular networks. Finally, we show numerical results provided by simulations in a realistic urban scenario focusing, as a case study, on the crowd sensing vehicular network application with VLC added to short range IEEEź802.11p technology. Results demonstrate that the addition of VLC improves the performance of a conventional vehicular network based only on IEEEź802.11p.