FM subcarrier systems
FM broadcast signals can carry additional data information. An important application is in Road Transportation, in particular for Advanced Traveller Information Systems.
Such data signals can be added on a subcarrier (e.g. at 57 kHz) to the base band audio multiplex signal of an FM broadcast transmission.
Autofahrer information (ARI)
A traffic information system based on this idea is in use by the German ARD broadcasters since the early seventies.
Radio Data System (RDS)
The Radio Data System (RDS) was standardized in 1984 by the European
Broadcasting Union (EBU) in the Tech 3244 Specification.
RDS receivers can tune automatically to a certain radio station or to a station carrying a particular type of programming. RDS is in operation in about 15
European countries. A U.S. version is called Radio Broadcast Data System (RBDS).
RDS was adopted as CCIR Recommendation 643, Dubrovnik
1986.
RDS provides approx 1200 bit/s data, e.g.
- Program / format type codes (PTY)
- Traffic information (TMC) at 300 bit/s. The maximum capacity of RDS TMC allows transmission of about 300 messages per hour. Messages can be used for route guidance systems.
- Alternative Frequencies (AF)
- Radio Paging (RP)
and
- Enhanced Other Networks (EON).
RDS requires small reduction (1 dB) of loudness of audio signal
RDS Traffic Message Channel (TMC)
RDS is particularly useful for FM reception in a car.
Snap shot from and RDS car stereo radio, receiving
information about congested traffic ("FILE " in Dutch) in The Netherlands
Provision of road traffic information is seen as an important feature of RDS.
TMC information is coded in a way that it is language independent
so that all European citizens can use RDS-TMC in whatever
European country they are but still receive information in their own language.
Moreover advanced navigation systems can filter and process TMC data
to present only relevant information to the user, or to compute optimum routes and travel times.
The major European car radio manufacturers (Philips, Blaupunkt,
Grundig) cooperate in the European Association
of Consumers Electronic Manufacturers (EACEM) developing such systems.
Traffic data can also be carried by DAB broadcast or GSM telephone systems.
High Speed Data System (HSDS)
HSDS by Seiko/ ACTTIVE
- Widespread availability of chips should allow installation in watches or other devices
- higher data speed than RDS
- Applications include paging
- Info: traffic, weather, financial, sport
- Portland and Seattle (20.000 subscribers each pay 80-100$ for watch + 10$ per month)
- Plans to cover 80% of US by end 1996
- HSDS is introduced in The Netherlands and in France in 1995
U.S. High Speed Subcarrier Systems
The National Association of Broadcasters (NAB) and Consumer Electronics Manufacturers Associatition
(CEMA) are testing three systems at NASA Lewis Research Center in Cleveland, Ohio.
The Federal Highway Administration is particularly interested in HSDS and STIC for use in Intelligent
Highway Systems (ITS).
