Impact of blockage and mobility on collaborative sensing and millimeter wave based communication

This dissertation considers the impact of blockage and mobility on collaborative sensing and millimeter wave (mmWave) based communication networks. We first study the character of interference and MAC performance in dense indoor mmWave wearable networks. Using simple stochastic geometric models for propagation in mmWave bands, we quantify the number of strong interferers as seen by a typical receiver and show that it is limited due to blockage. We propose a model to evaluate the performance of current MAC designs using clustering and hierarchical scheduling. Our results show that the MAC overheads are scalable, i.e., the performance optimal cluster size does not grow with user density in dense scenarios. Furthermore, we show that at high densities the per user throughput is eventually constant. Next we consider the impact of blockage mobility on MAC overheads and performance in such networks. We propose a stochastic geometric model to capture the temporal dynamics of strong interfering channels resulting from blocking in networks comprising both fixed and mobile blockages. Based on our analysis, we derive the rate of change in channels' states, i.e., Line-of-Sight (LOS) and Non-LOS (NLOS), and estimate the signaling overheads resulting from blockage mobility. We argue that while the overheads to track the interference environment may in fact be limited, MAC protocols will most likely be better off not coordinating with distant and/or mobile nodes. We then move on to another area where obstructions have a major impact, i.e., collaborative sensing for automated driving applications. Both the sensing and communication for collaborative sensing may be subject to obstructions (blockages) in such a collaborative setting. We introduce new models for vehicular collaborative sensing and networking under obstructions and evaluate how "performance" scales. In particular, we quantify the coverage and reliability gains obtained by collaborative sensing as a function of the penetration of collaborative vehicles. We further evaluate the associated communication loads in terms of vehicle-to-vehicle (V2V) and/or vehicle-to-infrastructure (V2I) capacity requirements and how these depend on penetration. Sensing by a single vehicle can be greatly limited by obstructing neighboring vehicles and objects, while collaborative sensing is shown to greatly improve sensing performance, e.g., improves coverage from 20% to 80% with a 20% penetration. Furthermore, the volume of sensor data a vehicle generates and needs to share for collaborative sensing does not necessarily increase with the density of objects. In scenarios with limited penetration and enhanced reliability requirements, infrastructure can be used to sense the environment and relay data. Once penetration is high enough, vehicular collaborative sensing provides good coverage and V2V connectivity. Data traffic can be effectively 'offloaded' to V2V network, making V2I resources available to support other services. Finally we present a more detailed evaluation of the performance of collaborative sensing assisted by sensing capable infrastructure, including Road Side Units (RSUs) and sensors on cellular infrastructure. We compare the performance of different infrastructure and deployment schemes in terms of collaborative sensing coverage. Unless deployed along roads, cellular based sensors off the roads are more obstructed and RSUs deployed at intersections and at even spacings appear more desirable. Simulation results show that RSUs see fewer environmental obstructions when placed higher than vehicles and can benefit from temporal diversity in sensing. Although RSUs have good sensing coverage, in order to communicate with the relevant vehicle, they will require relatively high communication range, rate and reliability. Even if RSUs provide complete coverage of the roads, to increase reliability of sensing, e.g., redundancy in sensing, collaboration amongst sensing capable vehicles may still be desirable.Electrical and Computer Engineerin

A City-Scale ITS-G5 Network for Next-Generation Intelligent Transportation Systems: Design Insights and Challenges

As we move towards autonomous vehicles, a reliable Vehicle-to-Everything (V2X) communication framework becomes of paramount importance. In this paper we present the development and the performance evaluation of a real-world vehicular networking testbed. Our testbed, deployed in the heart of the City of Bristol, UK, is able to exchange sensor data in a V2X manner. We will describe the testbed architecture and its operational modes. Then, we will provide some insight pertaining the firmware operating on the network devices. The system performance has been evaluated under a series of large-scale field trials, which have proven how our solution represents a low-cost high-quality framework for V2X communications. Our system managed to achieve high packet delivery ratios under different scenarios (urban, rural, highway) and for different locations around the city. We have also identified the instability of the packet transmission rate while using single-core devices, and we present some future directions that will address that.Comment: Accepted for publication to AdHoc-Now 201

Study on QoS support in 802.11e-based multi-hop vehicular wireless ad hoc networks

Multimedia communications over vehicular ad hoc networks (VANET) will play an important role in the future intelligent transport system (ITS). QoS support for VANET therefore becomes an essential problem. In this paper, we first study the QoS performance in multi-hop VANET by using the standard IEEE 802.11e EDCA MAC and our proposed triple-constraint QoS routing protocol, Delay-Reliability-Hop (DeReHQ). In particular, we evaluate the DeReHQ protocol together with EDCA in highway and urban areas. Simulation results show that end-to-end delay performance can sometimes be achieved when both 802.11e EDCA and DeReHQ extended AODV are used. However, further studies on cross-layer optimization for QoS support in multi-hop environment are required

Optimal Content Downloading in Vehicular Networks

We consider a system where users aboard communication-enabled vehicles are interested in downloading different contents from Internet-based servers. This scenario captures many of the infotainment services that vehicular communication is envisioned to enable, including news reporting, navigation maps and software updating, or multimedia file downloading. In this paper, we outline the performance limits of such a vehicular content downloading system by modelling the downloading process as an optimization problem, and maximizing the overall system throughput. Our approach allows us to investigate the impact of different factors, such as the roadside infrastructure deployment, the vehicle-to-vehicle relaying, and the penetration rate of the communication technology, even in presence of large instances of the problem. Results highlight the existence of two operational regimes at different penetration rates and the importance of an efficient, yet 2-hop constrained, vehicle-to-vehicle relaying

Benets of tight coupled architectures for the integration of GNSS receiver and Vanet transceiver

Vehicular adhoc networks (VANETs) are one emerging type of networks that will enable a broad range of applications such as public safety, traffic management, traveler information support and entertain ment. Whether wireless access may be asynchronous or synchronous (respectively as in the upcoming IEEE 8021.11p standard or in some alternative emerging solutions), a synchronization among nodes is required. Moreover, the information on position is needed to let vehicular services work and to correctly forward the messages. As a result, timing and positioning are a strong prerequisite of VANETs. Also the diffusion of enhanced GNSS Navigators paves the way to the integration between GNSS receivers and VANET transceiv ers. This position paper presents an analysis on potential benefits coming from a tightcoupling between the two: the dissertation is meant to show to what extent Intelligent Transportation System (ITS) services could benefit from the proposed architectur