Bluetooth Low Energy performance and robustness analysis for Inter-Vehicular Communications
Introduction
Smartphones are increasingly equipped with sensors and communication interfaces. One of the latest additions to the communication technologies is Bluetooth Low Energy (BLE), also called Bluetooth Smart. Although similar in some regards, BLE is not backwards compatible with previous Bluetooth versions as it uses a different controller (i.e. physical and link layer). However, most devices that support BLE implement both protocol stacks in dual-mode.
This low energy and low latency communication protocol has been developed to facilitate communication between mobile devices and other peripherals (e.g. smartwatches [1]). Common application areas include fitness, healthcare and smart homes, among others. The protocol defines several upper layer functionalities that allow fast and easy message exchange between devices.
In this paper we investigate the potential of BLE for Inter-Vehicular Communications (IVC). This work is motivated by the fact that the deployment of specifically designed IVC technologies such as Dedicated Short Range Communications (DSRC) based on IEEE 802.11p, is taking longer than initially expected [2]. It is our belief that the ubiquity of BLE enabled mobile devices would allow a fast deployment of new Intelligent Transportation Systems (ITS) in a near future. This is especially true as more and more car manufacturers provide interfaces to tightly integrate mobile devices within new vehicles (e.g. Apple CarPlay [3]). It is expected that by 2018, 90% of mobile devices will support the low energy standard [4]. Another advantage is that due to the low energy requirements, BLE services can run in the background on battery powered mobile devices without limiting the usage of other applications. Although this technology has originally been designed for short-range single hop communications, we show that it is possible to send short messages from one device to another up to a maximum distance of 100 m. By the means of experiments, we evaluate different driving scenarios and investigate the impact of wireless channel interference on BLE communications.
We developed a proof-of-concept mobile application that uses off-the-shelf smartphones to show how BLE can be used to send data over multiple hops, which significantly increases the scope of the application.
To further proof BLE in its current state for IVC, we show how co-existence between Wi-Fi and BLE looks in practice and investigate how resilient BLE communications are to interferences on the same Radio Frequency (RF) band coming from IEEE 802.11 devices operating at maximum capacity.
During our experiments, we measured performance in terms of delivery ratio and round-trip time for multiple dynamic vehicular scenarios and static interference scenarios. We also identify and discuss several shortcomings that make the current version of BLE not suitable for all kind of applications. We conclude that BLE can, indeed, be used to exchange information between vehicles while driving. This makes BLE an interesting candidate for specific deployment but, given the obtained results, it cannot be considered as a complete replacement for on-board communication interfaces such as DSRC/802.11p.
The remainder of this paper is organised as follows. In Section 2 we provide a literature review. Next, in Section 3, we present an overview of the BLE protocol stack. In Section 4, we describe how BLE can be used in a vehicular context. The vehicular experimental setup and results are discussed in Section 5. A study on BLE robustness to interferences can be found in Section 6. In Section 7 we conclude the paper and provide directions for future work.
Section snippets
Related work
Bluetooth Low Energy (BLE) has been standardised by the Bluetooth Special Interest Group (SIG) under the Bluetooth 4.0 specification [5]. Gomez et al. [6] provided a concise overview of the BLE protocol stack and investigated the impact of several critical parameters on its performance. They identified that there exists a trade-off between energy consumption and network performance that depends on several configuration parameters.
As BLE is mainly used for low power communications and
BLE overview
Bluetooth Low Energy, marketed as Bluetooth Smart, initially introduced by Nokia in 2006 under the name Wibree, was included into the Bluetooth Version 4.0 Core Specification in 2010 [19].
BLE was developed as a single-hop communication technology with a multitude of different applications in mind; healthcare, sport and fitness, consumer electronics, smart homes, security and proximity sensing.
Given the widespread availability of Bluetooth technology it is fair to assume BLE success based on
BLE for vehicular communications
Bluetooth Low Energy was not developed with vehicular applications in mind. Nevertheless a piconet between one or more vehicles can be engineered using off-the-shelf smartphones fixed to a car’s dashboard. We can imagine that in a near future, where entertainment systems in cars will provide a stronger bound between one’s smartphone and car (e.g. Apple CarPlay [3]), the BLE interface from the smartphone or from the car itself can be used for fast and reliable communication to neighbour vehicles.
Performance evaluation
For each scenario described in Section 4 we analysed different data taken from our mobile application logs regarding delivery ratio, round-trip time, distance between the vehicles and packet rate as well as end-to-end delay for our multi-hop experiment.
The role of the mobile application is crucial for the performance evaluation since data connection and messages exchanged are directly logged on the devices used for all scenarios. These logs are then extracted after each test run and combined to
Robustness analysis
As previously demonstrated, the current version of BLE might mainly be applied to low speed vehicular scenarios (e.g. city intersections, urban environments). We took as a challenge to study its behaviour in a congested RF spectrum by reproducing in our laboratory an interference testbed. Previous work of Giordano et al. [25] shows how, in highly populated areas, we can easily detect more than 200 Access Points (APs) mainly occupying the non-overlapping channels 1,6 and 11. It is thus
Conclusion and future work
In this paper we studied the potential of Bluetooth Low Energy (BLE) for Inter-Vehicular Communications (IVC). We described a mobile application specifically developed to work for hardware already on the market that allows for multi-hop communications between moving vehicles.
We measured performance in terms of delivery ratio and round-trip time for multiple single-hop scenarios and end-to-end delay for a multi-hop proof-of-concept application. Furthermore, we analysed the impact on
Acknowledgement
The authors would like to thank Telindus Luxembourg for their support and their industrial insight on the topic.
Walter Bronzi is a Ph.D. student working at the Interdisciplinary Center of Security Reliability and Trust (SnT) for the VehicularLab in Luxembourg. Prior to beginning the Ph.D. program, Walter successfully completed the Bachelor and Master of Computer Sciences at the University of Luxembourg. Walters main interests lie in vehicular networks, short-range radio technologies and mobile app development.
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Walter Bronzi is a Ph.D. student working at the Interdisciplinary Center of Security Reliability and Trust (SnT) for the VehicularLab in Luxembourg. Prior to beginning the Ph.D. program, Walter successfully completed the Bachelor and Master of Computer Sciences at the University of Luxembourg. Walters main interests lie in vehicular networks, short-range radio technologies and mobile app development.
Raphael Frank is a Research Scientist at the Interdisciplinary Centre for Security, Reliability and Trust (SnT), University of Luxembourg and head of the VehicularLab. Frank received his Ph.D. in Computer Science from the University of Luxembourg in 2010. He is currently involved in several European and national research projects. His research interests include wireless networks and mobile computing.
German Castignani is research associate at the Interdisciplinary Centre for Security, Reliability and Trust (SnT). He received his Computer Sciences Engineer degree at the University of Buenos Aires (FIUBA, Argentina) and a Ph.D. in Computer Sciences at Institut Mines-Telecom, Telecom Bretagne (Rennes, France). His research interests include vehicular and wireless networks, mobility management, Intelligent Transportation Systems (ITS) and advanced driving assistance systems.
Thomas Engel is Professor for Computer Networks and Telecommunications and Vice-Director of the Interdisciplinary Center for Security, Reliability and Trust (SnT) at the University of Luxembourg. Thomas Engel is member of the Information and Communication Security Panel ICS of NATO and Civil High-Level Expert for Electronic Communications (representing Europe) of NATO CEP/CCPC. Since 2009 he is chairman of the National IPv6 Council Luxembourg and appointed Vice-Director of the newly created Interdisciplinary Center for Security, Reliability and Trust (SnT) at the University of Luxembourg.