Then, the paper identi? es the key networking technologies used for in-vehicle and inter-vehicle applications, comparing their properties and indicating future challenges in the area of wireless automotive communications, with a focus on realtime aspects. inter-vehicle communications are presented and compared, pointing out real-time related aspects, in Section 3. Finally, the paper is summarised in Section 4. 2 Telematics Automotive telematics enables the deployment of a number of new services and applications integrating wireless communication technology into a vehicle.
As a result, the vehicle acquires new capabilities and offers more services to its users. Examples of telematics services and applications are: • Navigation and traf? c information systems – A vehicle equipped with a telematics unit can direct a driver to a desired location, while providing real-time traf? c information for a given route. • Voice recognition and wireless Internet connection Drivers and their passengers can receive and send voiceactivated e-mails while on the road. • Safety systems – Collision avoidance systems, unsafe driving pro? ling, intelligent airbag deployment systems.
Communications between the vehicle and its surroundings, e. g. , other vehicles and roadside objects. Automatic airbag deployment noti? cation. Accident and roadside assistance. An example is given by the General Motors Advanced Automatic Crash Noti? cation (AACN) system available on many GM OnStar TM -equipped vehicles. • Security systems – Vehicle antitheft and stolen vehicle tracking services. Tracking and remote door unlocking is provided by OnStar TM -equipped vehicles. • Diagnostics and maintenance services – Remote diagnostics and/or maintenance systems, vehicle and driver monitoring. 1 Introduction
Nowadays the two areas that are getting most attention in automotive communications are protocols and technologies supporting x-by-wire applications, e. g. , Flexray , and protocols and technologies for telematics and wireless applications. Automotive telematics refers to any kind of vehicle information or communication service that relies on a wireless communication link. There are several applications pushing for the adoption of wireless communications in automotive systems, both within the vehicle (in-vehicle communications) and between the vehicle and its surroundings (inter-vehicle communications).
Looking at in-vehicle communications, more and more portable devices, e. g. , mobile phones, portable GSM devices and laptop computers could exploit the possibility of interconnection with the vehicle. Also, several new applications will exploit the possibility of inter-vehicle communications, e. g. , vehicle-to-vehicle  and vehicle-toroadside communications. This paper presents the most common wireless protocols used for in-vehicle and inter-vehicle communications in the automotive industry, and the ones that might be used in the near future.
Originally devised for PAN deployment for low-cost, low-power, short-range wireless ad hoc interconnection, Bluetooth technology has fast become very appealing also for the automotive environment, as a potential automotive wireless networking technology. In response to interest by the automotive industry, in December 1999 the Bluetooth Special Interest Group (SIG) formed the Car Working Group. The Hands-Free pro? le was the ? rst of several application level speci? cations from the Car Working Group. Using the new Hands-Free pro? le, products that implement the Bluetooth speci? ation can facilitate automatic establishment of a connection between the car’s hands-free system (typically part of its audio system) and a mobile phone. Bluetooth wireless products incorporating these new enhancements enable a seamless, virtually automatic interface between the car and wireless products. Today, Bluetooth allows hands-free use of a mobile phone either through the car’s audio system or wireless headsets, resulting in better sound and control, and a safe solution to legislation banning mobile phone use while driving. The Bluetooth SIG, in November 2004, laid out a threeyear roadmap for future improvements to Bluetooth.
Prioritised targets include Quality of Service (QoS), security, power consumption, multicast capabilities, privacy enhancements. Long-range performance improvements are expected to increase the range of very low power Bluetoothenabled sensors to approximately 100 meters. systems raised signi? cant interoperability problems which ZigBee technology solves, providing a standardized base set of solutions for sensor and control systems.