MSC is a time-interleaved data channel divided into a number of sub-channels, which are individually convolutionally coded, with equal or unequal error protection. Each sub-channel may carry one or more service components (audio, data). Information about sub-channel parameters is transmitted within FIC.
MSC consists of Common Interleaved Frames. Every CIF contains 55 296 bits. The smallest addressable unit of the CIF is the Capacity Unit (CU), comprising 64 bits. Therefore, the CIF contains 864 CUs, which shall be identified by the CU addresses 0 to 863.
Let's assume that an audio service has following parameters:
startAddress = 84 CU and
subchannelSize = 96 CU.
- ETSI EN 300 401 pp. 34-42