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Reply To: FACCH SIGNALLING

#52799
MKT
Guest

Hi pix

thanks for your reply

Second question.. here it is

Suppose i want to make a phone call to you.

I dial your MS from my MS.

Connection is establish.

we are talking.

What iam speaking is heard by you 80 ms later. This delay is question here.

Voice is first collected for 20 ms and then processed by vocoder. This gives a delay of 20ms

After x y z we get 456 bits corresponding to 20ms speech. These 456 are then divided into 8 blocks(8 x 57=456). These blocks are then sent one by one over “normal” burst. The first 57 bits of normal burst represents the 20 ms speech block no N, and the second 57 bits of normal burst represents the 20 ms speech block no N+1,.
For this we have to wait for the N+1 speech block to arrive. This again induces a delay of 20 ms.

Thus interleaving induces a delay of 20 ms.

so total delay at my MS is 40 msec.

My call reaches the MSC.

MSC send it towards you.

At transcoder again we will have 64/16 conversion ie RPE-LTP which gives 20ms delay.

At BTS the interleaving takes place. and this again induces the delay of 20 msec.

hence the total delay will be

20+20+20+20=80 msec.

This theory doesn’t includes transmission delays.

Is it ok?

Also i don’t know reverse of vocoding and de-interleaving will induce the equal delays or not?

If yes..then

MS to MSC total delay we have

20+20 at MS(vocoding+interleaving)

20 at BTS —deinterleaving

20 at transcoder for reverse of vocoding

This gives 80 ms in one direction.

considering equal delay in other end direction

we have 80+80 =160 ms delay for a MS TO MS CALL.

Just for comments from every body

Regrads