TRDS4002
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User Manual
Rev. 1.0 - 03/08/05
Fig.5 shows the protection ratio curves for the three services.
Figure 5
The structure of the data signal is shown in fig.5.
Base-band structure of Radiodata
The structural element is the “group” containing 104 bits.
Each group comprises 4 blocks of 26 bits each, of which 16 are information and 10
are for protection.
Each block is directly identifiable by an 8 bit word which is summed in module-2 with
the 10 protection bits.
The transmission is completely synchronous and there are no interruptions between
consecutive groups and blocks.
Each block is protected by a self-synchronizing, compressed, cyclical code (26,16),
having the following properties:
•
detects all single and double errors;
•
detects error strings of up to and including 10 bits;
•
detects approximately 99.8% of error strings over 10 bits long.
The code (26,16) performs well in correcting error strings which occur frequently in
in-car reception.
All error strings of upto 5 bits can be corrected.
It should be noted that the correction of reception errors implies a finite possibility of
accepting as correct, an incorrect message that has not been detected.