Operating ITS-G5 DSRC over Unlicensed Bands: A City-Scale Performance Evaluation

Future Connected and Autonomous Vehicles (CAVs) will be equipped with a large set of sensors. The large amount of generated sensor data is expected to be exchanged with other CAVs and the road-side infrastructure. Both in Europe and the US, Dedicated Short Range Communications (DSRC) systems, based on the IEEE 802.11p Physical Layer, are key enabler for the communication among vehicles. Given the expected market penetration of connected vehicles, the licensed band of 75 MHz, dedicated to DSRC communications, is expected to become increasingly congested. In this paper, we investigate the performance of a vehicular communication system, operated over the unlicensed bands 2.4 GHz - 2.5 GHz and 5.725 GHz - 5.875 GHz. Our experimental evaluation was carried out in a testing track in the centre of Bristol, UK and our system is a full-stack ETSI ITS-G5 implementation. Our performance investigation compares key communication metrics (e.g., packet delivery rate, received signal strength indicator) measured by operating our system over the licensed DSRC and the considered unlicensed bands. In particular, when operated over the 2.4 GHz - 2.5 GHz band, our system achieves comparable performance to the case when the DSRC band is used. On the other hand, as soon as the system, is operated over the 5.725 GHz - 5.875 GHz band, the packet delivery rate is 30% smaller compared to the case when the DSRC band is employed. These findings prove that operating our system over unlicensed ISM bands is a viable option. During our experimental evaluation, we recorded all the generated network interactions and the complete data set has been publicly available.Comment: IEEE PIMRC 2019, to appea

Connected vehicles for internet access: deployment and spectrum policies

Internet traffic from mobile users has been growing sharply. To meet the needs of thoseusers, it is important to expand capacity of networks that provide Internet access in cost effectiveways. This capacity has traditionally been provided by cellular networks. However,expanding the capacity of those networks alone may not be the most cost-effective way to meetthe present and future growth of mobile Internet under some circumstances. In this dissertation,we show that networks of connected vehicles can be an important way to complement thecapacity of cellular networks to provide mobile Internet access under several scenarios.Connected vehicles may soon be widely deployed, forming mesh networks of short-rangeconnections among vehicles and between vehicles and roadside infrastructure. Theseconnections are collectively referred to as vehicle-to-everything, or V2X. Deployment ofconnected vehicles and infrastructure is primarily intended to enhance road safety, and the U.S.Department of Transportation has recently proposed a mandate of V2X devices in vehiclesusing Dedicated Short Range Communications (DSRC) technology. Other applications are alsoenvisioned that include Internet access in vehicles connecting to roadside infrastructure servingas gateways to the Internet.In this work, we find that V2X-based networks are more cost-effective than cellular toprovide Internet access, in scenarios which DSRC devices are mandated in vehicles to enhanceroad safety. This is true initially for densely populated urban areas, but over time V2X-basednetworks would be cost-effective in less populated areas as well, as long as Internet traffic orpenetration of V2X devices grow as expected.Local and state governments are expected to deploy roadside infrastructure for safetyapplications. If that infrastructure is shared with Internet Service Providers for a fee, then V2XABSTRACT based networks are cost-effective in locations with even lower population densities than thelocations where it is cost-effective to deploy infrastructure for Internet access only. Moreover,the sharing fee could help governments save in infrastructure costs. We find the pricingstrategies that maximize either cost-effectiveness or government savings. We estimate thatgovernments could save about one-fifth of the total cost to deploy safety infrastructurenationwide in the U.S., if fees are set to maximize government savings. Although we find thatthese prices may differ from the pricing strategy that maximizes cost-effectiveness, maximizinggovernment savings results in near-optimal cost-effectiveness.The U.S. Federal Communications Commission has allocated 75 MHz of spectrum to beused exclusively by DSRC devices, and it has been hotly debated whether all or part of thatbandwidth should be shared with unlicensed devices. We find that it is highly efficient to shareany spectrum allocated to V2X communications beyond the portion of that spectrum that isneeded for safety-critical DSRC messages. V2X and unlicensed devices require up to 50% lessbandwidth on shared spectrum to achieve given throughputs, compared to V2X and unlicenseddevices using separate bands. We conclude that the spectrum available for V2X should bemaintained or increased, as long as much of that spectrum is shared with non-V2X devices.Conclusions are derived from an engineering-economic approach, in which part of theassumptions are based on data from a citywide deployment of connected vehicles in Portugal.The data is used in a detailed and realistic packet-level simulation model of V2X-basednetworks used to provide Internet access with DSRC technology. In some scenarios, thesimulation also includes unlicensed devices using Wi-Fi technology. The results of the networksimulation are then fed into engineering-economic models to compare costs of V2X-basednetworks with costs of macrocellular networks to carry given amounts of Internet traffic, and toestimate other measures such as government revenues and spectrum usage. Those measureshelp inform decisions about where and when to deploy V2X-based networks, decisions about whether and how to promote public-private partnerships to deploy V2X infrastructure, anddecisions about sharing spectrum used for V2X communications with non-V2X devices. <br