RDS Germany - TMCpro: Multi-group messages

TMCpro Multi-Group Messages Cause Incomplete or Modified Traffic Messages in Germany

Applies To

· HERE RDS-TMCpro integration

· RDS-TMC data processing systems

· TMC version 1.0 (RDS-TMCpro)

Symptoms / Triggers

· Incomplete or missing details in TMC messages received in Germany

· Traffic event details change or appear fragmented (e.g., message direction, extent, or importance modifies unexpectedly)

· Log shows incomplete event data (e.g., missing Label 4 or Label 5 quantifiers)

Summary

TMCpro messages in Germany may be sent as Multi-Group Messages (MGM), which require special handling to assemble the full event data. Failure to process these sequences correctly can result in incomplete or incorrect traffic information.

Answer

TMCpro messages in Germany use multiple RDS groups to transmit event information, which must be combined in sequence. Receivers must verify group order and merge all parts of the message to avoid missing or modified event details. Ensure TMC decoder logic supports MGM decoding by checking for multi-group continuity flags and merging data in the correct sequence.

Root Cause

In Germany, due to high event complexity and data volume for TMCpro services, some messages cannot fit into a single 37-bit RDS group. These messages are sent as Multi-Group Messages (MGMs), consisting of 2–5 Type 8A RDS groups. The system combines these groups in order to reconstruct the full event.

Impact

· Without proper MGM handling, traffic messages may appear incomplete or inaccurate

· Users may perceive incorrect event details (e.g., wrong direction or missing location)

· Receivers may ignore multi-group messages if not configured properly

Recommended Actions

1. Validate TMC decoder compatibility with RDS-TMCpro Multi-Group Messages

2. Check if the decoder can detect and reassemble consecutive TMC groups

3. Ensure that Labels 4 and 5 are retained during processing (these contain quantifiers and cannot be omitted)

4. Implement logic to validate the sequence order of groups using continuity flags (e.g., Group 2 must modify data in Group 1)

5. If unsure about handling, refer to RDS-TMCpro specification v5 or higher

Notes

· This issue is specific to RDS-TMCpro in Germany

· Ensure decoder firmware or software is updated to support TMC version 1.0 (TMCpro)

· The TMC specification (ETSI EN 301 530-1 + Amd.2) provides full instructions on handling Multi-Group Messages

Related Information or documentation

· RDS-TMC Technical Overview (https://docs.here.com/map-content/docs/tmc-code-attribute)

Keywords or Tags

TMCpro, multi-group messages, MGM, RDS-TMC, Germany, TMC 1.0, incomplete messages, RDS group sequence, Label 4, Label 5, quantifier missing, RDS-TMCpro decoder,