Decoding the DAB Transmitter Identification Information Signal.
The Transmitter Identification Information signal (TII) uniquely identifies each transmitter in a DAB network. The TII is optional. It's slipped in every other NULL "Sync" symbol within the 96 ms frame. That's an update of around 5 times a second.
DAB uses a signal frequency network (SFN). Every transmitter in that network sends identical OFDM carriers - the "Multicarrier Modulation" of 1536 frequencies.
The TII is unique for each transmitter, so breaks that "identical" rule.
During the NULL symbol each transmitter switches on some of the 1536 available OFDM carriers in a unique pattern. This pattern is duplicated 4 times to improve signal to noise. So that's 384 carriers. We're looking for pairs of carriers, so that's 192 pairs. Sub-identifier codes are repeated 8 times - we getting to 192/8 = 24. Sub-identifier codes range between [0..23].
The Main code is encoded by the sub-identifier code repetition. There's another rule: the Sub-identifier code can only use 4 out of the 8 pairs. There are 70 combinations of 4 objects from a set of eight.
So that give the range of main codes [0..69].
See the DAB standard, section 14.8.
QIRX is the open source project used by this demo. Their DABTII dll source is closed, but their
C# interface wasn't. I put something together.
The DAB standard (ETSI EN 300 401)
Read section 14.8 Transmitter Identification Information signal and Figure 64.
Design and Implementation of the DAB/DMB Transmitter Identification Information Decoder
Receiver synchronization for Digital Audio Broadcasting Ofcom - Technical parameters for broadcast radio transmitters
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Can you really have a yagi covering 174–240 MHz?
Page last edited 3rd April 2019. [email protected]