Links btw MSC-BSC-BTS

[guess.who]

does any one have a good document or manual that describes how Links travel between MSC , BSC and BTS... i mean the conversion of Time slots and data rate between these different nodes...

[guess.who]

come on guyz.....there are so many experienced ppl here..... please spare a bit of time and share your experience.... i just need to know the overview of how links travel as E1s between their entities...
Thanks in advance

[ghassen]

come on guyz.....there are so many experienced ppl here..... please spare a bit of time and share your experience.... i just need to know the overview of how links travel as E1s between their entities...
Thanks in advance

the times slots are mapped into the abis depending on the manufacturer but they have almost the same concept
between the bts and the MS the interface is called A interface
timeslots have a bitrate of 16kbps = 13+3 kbps
why ??
because every 20 ms we have 260 bit of speech and these bits are divided into 3 groupes :
-group I wich is composed by 50 bit very portected
-group IIa wich is composed by 132 bit that protected
-groups IIb wich is composed by 78 unprotected
then how these bits are organised
we protect the first groupe by 3 bit
50+3 = 53
then we add the second groupe and we protect the all by 4 bit
((50+3)+132)+4 = 189
now we aplys the convulotional code
189 * 2 = 378
and then we add these 378 + 78 = 456
i have to mention that a burst is composed by two block of 57 user data
then these bits are divided to 8 blocks of 57 bit each one
this for the air interface
depending on the manufacturer these bit will be mapped into the abis interface between the bsc and the bts these timslots are 64 kb/s and divided into 4 subslot each one with 16Kb/sec
each timeslot coming from the air will be mapped into one subslot on abis for CS only
the signaling on the abis is done by lapd (link protocol for d channel)

[guess.who]

first of all......thanks a lot for the reply...

in 13 + 3 kbps ....13 is understandable ....but whats 3kbps for ??
the rest is understood but can u elaborate on what u have told abt bts to bsc...like subslots...etc....

[ghassen]

first of all......thanks a lot for the reply...

in 13 + 3 kbps ....13 is understandable ....but whats 3kbps for ??
the rest is understood but can u elaborate on what u have told abt bts to bsc...like subslots...etc....

the 3 bits are overhead

[guess.who]

overhead for what?

[ghassen]

overhead for what?

i think for to know wich codec is used

[atif]

3Kbps is Inband signaling for the system.
Its basically deals with the Codec type, Time allignment command,and control information.
If you want to get detail please read out 3GPP TS 48.060.Which will clear you out about the 3Kbps