PDCH: Packet Data Channel in GPRS
PDCHs may also be used by TBFs in Dual Transfer Mode (DTM). The DTM TBFs may either use PDCHs already allocated for normal GPRS/EGPRS traffic or trigger allocation of additional PDCHs that then can be used for normal GPRS/EGPRS traffic too. Some PDCHs can later be returned to the CSD when they are no longer needed, or when CS traffic or Abis demand requires it. There are different types of PDCHs; dedicated PDCHs, semi-dedicated PDCHs and on-demand PDCHs. Dedicated PDCHs: The number of dedicated PDCHs in a cell is set by the operator. These PDCHs are allocated at configuration from the CSD to the PSD for GPRS/EGPRS traffic and can then not be pre-empted by CS traffic. A GSL resource and an Abis resource is allocated at the time of allocation. The number of dedicated PDCHs can only be decreased by the operator. Semi-dedicated PDCHs: The number of semi-dedicated PDCHs in a cell is also set by the operator. These PDCHs are allocated at configuration from the CSD to...