The GSM data transmission occurs in bursts where TDMA frames a transmitted. It is however organized in a hierarchical structure for efficient transmission and encryption.
- A GSM frame is divided into eight time slots where each slot represents a physical TDM channel. Different types of data are transmitted in time slots. The total time required for a GSM time-slot to complete transmission with guard time is 577µs.
- Eight such time slots constitute together to form a frame.
- In case of traffic channels and control channels associated with them, 26 frames create a Multiframe. (i.e TCH Multiframe)
- In case of broadcast channels and control channels associated with them, 50 frames create a Multiframe. (i.e. BCH Multiframe)
- 51 TCH Multiframes combine together to form a Superframe.
- In case of BCH Multiframes, 26 BCH Multiframes combine to form a Superframe.
- In both the cases of TCH and BCH , 2048 superframes create a Hyperframe.
- A Hyperframe is the highest unit of GSM hierarchy.
- It lasts for 3 hours 53 seconds 760 milliseconds.