UMTS Layers Mapping for 12.2kbps AMR Call

Every freshman needs to learn the channel mapping of different layers when comming into UMTS fields. I don’t want to repeat those mapping relationships which could be found in almost every wireless book.

Here is an abstract figure showing the mapping of Logical Channels and Transport Channels, taking 12.2kbps AMR call as an example. Wheneven my mind is messed up about it, I will glance below picture and recall quickly.

12.2kbps AMR call

The biggest pipe stands for a radio link. And there are four Transport Channels for this radio link: DCH1, DCH2, DCH3 and DCH24.

  • DCH24 carries four SRBs, which map to four Logical Channels through RLC.
  • DCH1/2/3 map to three Logical Channels respectively. These three DCHs correspond to three classes of voice quality: Class A, Class B and Class C. They share the same AAL2 channels with the same Binding ID.