Design and implementation of a vehicle interface protocol using an IEEE 1394 network

Abstract

A wide variety of in-vehicle devices such as camera sensors, navigation systems, telematics and communication equipments have been incorporated into a vehicle to realize Intelligent Transport Systems (ITS) applications. Because an efficient standardized network is required, ITS Data Bus (IDB) has been discussed to carry high-speed multimedia data for audio, video and other real-time ITS applications. For connecting devices in a standardized manner, the IDB network has architecture with a gateway called vehicle interface which is located between automaker’s proprietary network and the standardized IDB network. IEEE 1394 (also known as iLink or FireWire), which can transport multimedia data for consumer electronics, is a good candidate for IDB network. In this paper, we analyze the issues for existing AV/C protocol (application layer protocol over IEEE 1394) to comprise the IDB network. In addition, we designed and implemented the vehicle interface protocol as a higher layer of IEEE 1394 to address the AV/C protocol issues for realizing the whole IDB network architecture.

Introduction

Towards realizing ITS applications, the SAE (Society of Automotive Engineers) is studying the ITS Data Bus (IDB) [1] for the transfer of multimedia data for audio, video, and other real-time applications among various devices such as cameras, navigation devices, telematics, and communication devices connected via an on-board automobile network. The configuration of an IDB network is illustrated in Fig. 1. The automobile manufacturer’s own proprietary network and the standardized IDB network are connected via the vehicle interface (gateway). The IDB devices are connected on the IDB network side. The objective is to allow common IDB devices to be connected to and operate over networks whose specifications vary among the automobile manufacturers.

As a medium for IDB networks, we, the Automotive Multimedia Interface Collaboration (AMI-C) [2] are investigating the IEEE 1394 high-speed serial bus [3], [4], [5], which is used for consumer electronics and personal computers. IEEE 1394 has been developed for consumer electronics and PCs, and the original specification is not suitable for automotive environment. In the 1394 Trade Association [6], physical layers, communication method, power mode, and Customer Convenience Port are specified as IDB-1394 specification [7], in which higher layer protocols are not included. As shown in [8], the basic AMI-C concept is that gateway architecture is useful to interconnect automaker’s proprietary network with public standardized multimedia networks (IDB-C [9], [10] and IEEE 1394). The IEEE 1394 high-speed serial bus currently supports a transfer speed of 800 Mbps, and the communication protocols provided include the asynchronous transfer mode and the isochronous transfer mode for stream data transmission. The network does not require an overall master controller, and a network that guarantees the QoS (Quality of Service) of stream data can be set up by simply defining nodes that correspond to the various consumer devices, without having to use a PC or other such device. Network specifications other than IEEE 1394 have also been considered as medium candidates, but they pose problems with respect to use as an IDB network. USB, for example, requires a master controller within the network and data transfer is done via the master, thus concentrating load on the device that has the master function. Ethernet employs CSMA/CD for media access control, which makes QoS guarantee difficult for stream data. While connection of devices to an Ethernet switch that has a CoS (Class of Service) function could be considered, that configuration would also not completely guarantee QoS and would furthermore require multiple Ethernet switches to maintain flexibility in network topology. On the other hand, while MOST (Media Oriented Systems Transport) [11] is sometimes used as an on-vehicle multimedia network, the use of TDMA transfer, in which the entire network is synchronized by a single clock, disallows dynamic allocation of bandwidth according to the stream data to be transferred, so efficiency is poor when multiple types of stream data are being transferred.

When the IEEE 1394 high-speed serial bus is used for general consumer electronics applications, the following standard upper layer protocol is used. The network administration and stream data transfer format are specified by the IEC 61883 consumer audio–video digital interface. Furthermore, the AV/C protocol [12] serves as the specifications for IEC 61883 upper layer control of consumer devices [13]. We describe the relations among the various protocol specifications in detail. Construction of a network based on these specifications allows the transfer of uncompressed video camera data as well as the digital broadcasting and transfer of DVD video multimedia data with protection of copyright. Here, we refer to a basic network built on IEEE 1394 high-speed serial bus specifications and IEC 61883 consumer electronics device control as an IEEE 1394 network. We refer to a protocol that includes the AV/C protocol and consumer electronics device control commands as the AV/C protocol.

Here, we report on (1) an investigation of problems that arise in constructing an IDB network using the IEEE 1394 network and AV/C protocol that have been standardized for use with consumer electronics, (2) the design a new protocol for solving the problems, and (3) an implementation of the protocol and confirmation of its operation. After describing the architecture of an IDB network in Section 2, we comment on the specifications of an IEEE 1394 network in Section 3. In Section 4, we analyze the problems involved in constructing an IDB network using an IEEE 1394 network. Section 5 explains in detail the structure and operation of a new vehicle interface protocol that was designed to solve the problems identified in Section 4. Section 6 describes the operation of a system that implements the vehicle interface protocol and the measurement of its boot time. Section 7 describes related works and Section 8 concludes this report.