I was reading about the GSM frames used in GSM communication. One thing pretty unusual caught my eye.
Training Sequence: This is used by the receiver’s equalizer as it estimates the transfer characteristic of the physical path between the BTS and the MS. The training sequence is 26 bits long.
26 bits training sequence: This training sequence is used as a timing reference and for equalisation. There is a total of eight different bit sequences that may be used, each 26 bits long. The same sequence is used in each GSM slot, but nearby base stations using the same radio frequency channels will use different ones, and this enables the mobile to differentiate between the various cells using the same frequency.
These are the definitions about the Training Sequence from 2 different sources. But, why would someone put the training sequence in the middle of a frame? Wouldn't it be more clever for the training sequence to be in the beginning of the frame so it can train the equalized for what is to come next?