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# Reply To: mapping of E1 channels

#48263
Pix
Guest

Hello Raji,

I don’t want to be rude, but if you don’t know what is the RSL on the ABIS, I don’t think the answers to your initial questions will ever satisfy you 🙂

RSL is the physical channel that carries the signalling of ONE trx (SACCH and SDCCH, if there are SDCCH on the TRX)

Now the whole purpose is to use ABIS as much as possibl for TCH. So we need to multiplex several RSL together as much as possible, and even multiplex them with OML. Of course, by doing so, you reduce the capacity for RSL, risking some ABIS congestion.

So those are the possible solutions (ts = 1 64kbps on the abis):
1. No multiplexing
1 OML = 1 ts
1 RSL = 1 ts
1 TRX = 2 ts

2. Static Mx
1 OML = 1ts
1 RSL = 0.25 ts (16kbps) (only one config : 4 RSL will be put on one ts)
1 TRX = 2 ts

3. 64kb/s statistical Mx
1 OML + 4 RSL = 64 kbps (one RSL can use up to 64kbps if the 3 others don’t use their bandwidth. Contrarily to the static mx, where 1 RSL cannot use more than 16 kbps)
1 TRX = 2 ts

4. 16kb/s statistical Mx
this is a particular configuration : each radio TS0 of each TRX must carry the BCCH or a SDCCH. No TCH allowed on TS0 !!
1 TRX = 1.75ts
OML+RSL = 0.25 ts (for the first TRX)
RSL = 0.25 ts (for the other TRX’s)

So with the solution “16kb/s statistical mx”, a cell with 4 TRX will use only 8 abis ts
0 – SYNC
1 … 31 = 15 TRX + 1 abis ts unused.

Finally, even if one BTS cannot use 14 TRX, one ABIS link can be shared by several BTS

FYI, an alcatel bts can go up to 24 trx 🙂 French rocks !!