To minimize the effect of sudden fades on the data that is received, the 456 encoded bits are split into eight 57 bit sub-blocks. 

The eight blocks comprise a single speech frame. They are spread over eight successive TCH time slots. 

Must Read>> Traffic Channel (TCH)

If any burst is lost because of fading or interference, the channel coding ensures that sufficient bits will be received correctly to allow error correction to operate.

A TCH time slot carries two 57 bit blocks of data from two different 20 ms speech segments.

The above figure shows how speech frames are diagonally interleaved within the time slots.

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