Communication advances Chapter | 2 27Bluetooth technology employs the 2.4 GHz ISM band which is unlicensed
and open in most countries. The Class 2 radio that is used in most cases oper-
ates at 2.5 mW and is shut down after a period of inactivity in an effort to keep
power consumption at a low-level. Bluetooth uses adaptive frequency hopping
(AFH) at 1600 hops/sec which employs a spread spectrum of 79 frequencies at
1 MHz intervals. The adaptive technology detects other devices and wireless
technologies that use the same spectrum and switches to empty frequencies,
thus achieving reduced interference with other devices and maximum use of the
available frequency spectrum. With the adaptive hopping, Bluetooth achieves
maximum performance even when more wireless technologies use the same
spectrum.
The latest Bluetooth version 4.0, or Bluetooth Smart, provides ultra-low
power consumption at all operating modes which makes it ideal for small bat-
tery-powered devices that can work for using standard coin-cell batteries, It is a
low-cost technology, supported by multiple vendors, offers interoperability and
an enhanced connectivity range, allowing device to connect directly with exist-
ing laptop, tablet, or smartphone Bluetooth nodes.
Apart from intravehicle and V2V communications, Bluetooth can be used
for V2I communication scenarios, for example, for allowing vehicles to interact
with the traffic signal system. Many companies that provide devices for the road
infrastructure are using Bluetooth to collect traffic flow information. The Blue-
tooth-enabled devices are embedded in the transportation network infrastruc-
ture, for example, at major intersections or bus stops and terminals and collect
anonymous Bluetooth signals transmitted by on-board Bluetooth devices or the
pedestrians’ smartphones. They use the collected data to calculate traffic jour-
ney times and estimate passenger and vehicle flows. The device identification
is achieved by using the unique MAC address that each Bluetooth device car-
ries and match MAC addresses across locations in order to accurately measure
journey time, thus solving any privacy concerns which are usually associated
with probe systems.
2.9 ETSI and CEN standards for V2X communications
Two European standardization bodies, (ETSI and CEN) are constantly con-
ducting research on new standards that can further improve communications in
the automotive and transportation domains. In this respect, the connected-car
standard (EC, 2014) defines how V2V and V2I communications should be in
Europe and lists all potential security risks from cyber-attacks against the wire-
lessly connected vehicles. The two technical specifications described in Release
1 of ETSI ITS are:
• EN 302 637-2: which defines the Cooperative Awareness Basic Service
• EN 302 637-3: that specifies the Decentralized Environmental Notification
Basic Service.