After the revision to version 1.5, ISO 15628 with which this ARIB standard complies, and the ISO 14906 quoted in this standard had been established and/or revised, and in this version 1.6, modifications have been made to correspond to these revised ISO standards.

In addition, corresponding to the revisions to the article numbers of the Radio Act and other related ministerial ordinances, Ordinance Regulating Radio Equipment etc. after the 1.4 version, the relevant numbers have been corrected. Furthermore, in accordance with the definition of the Ordinance of the Ministry of Radio Law etc., some technical terms have been reviewed.

Also, some of the use cases of communication control parameters in DSRC communication environment (base stations arrangement) have been reviewed.

The amendment of the Radio Equipment Regulations related to the Dedicated Short-Range Communication was enforced on November 29, 2007. In accordance with this amendment, the specification of the radio communication system was revised by adding the broadcast communication and the simplex communication.

Also, the specification of QPSK modulation was reviewed as QPSK modulation method had been commercialized, and the specification of the modulation accuracy in the base station and the test equipment, as well as the receiver sensitivity of the land mobile station, was revised.

Furthermore, the specification of the polarization for the base station and the test equipment was revised assuming that a leaky waveguide would be used as an antenna.

The Version 1.2 was prepared in accordance with the modifications of ISO/IEC, etc. standards, and to guarantee the reliable connectivity between the base stations installed on road side and the land mobile station mounted in vehicle.

The main revised points are shown below;

(1) The data structure of this Standard had initially been written by referring to the ISO CD 15628, however the ISO CD15628 was modified to ISO DIS 15628, so that Annex H was revised in accordance with the ISO DIS 15628 and to define “Action Type (sendMessage and waitMessage)” which corresponds to the data transmission service and the data inquiry service.

(2) The description of the reference to the ISO/IEC 8802 was deleted, as it is no longer adequate to refer to the ISO/IEC 8802 1999 which was revised from the ISO/IEC 8802 1994.

(3) The note to restrict the simultaneous slot accesses in the same frame at the land mobile station was added in order to guarantee the more reliable connection between the base stations installed on road side and the land mobile station mounted in vehicle under this Standard.

The Version 1.1 was prepared to guarantee the more reliable mutual connection among the base stations installed on road side, the land mobile station mounted in vehicle and the test equipment for the radio equipment of the land mobile station, and to realize the usage in the wide range communication circumstance.

The outline of the revised points are shown below:

(1) The intensity of spurious emission was partly changed from 25 µW to 2.5 µW based on the WRC-97.

(2) The high accuracy measurement method was added with the clarification of the definition for the transmission characteristics (modulation degree, etc.) to achieve the more reliable connectivity among the equipment.

(3) The identifiers of the available applications were extended to allow for the use with a wider variety of systems.

(4) The description of the applicable radio communication circumstance was improved by considering the actual usage situation.

(5) New requirement on the test equipment about the state restoration after tests was added for smoother system operation.