Abis Optimization Questions

[islam wagih]

Dears,

anyone has any answers about below questions;

1- Why Flexible Abis can not be used together with Abis Optimization for the same TG?
2- Why LAPD Concentration and LAPD Multiplexing is not possible to combine with Abis Optimization for
the same TG and why it is not needed?

Thanks alot

[s52d]

Dears,

anyone has any answers about below questions;

1- Why Flexible Abis can not be used together with Abis Optimization for the same TG?
2- Why LAPD Concentration and LAPD Multiplexing is not possible to combine with Abis Optimization for
the same TG and why it is not needed?

Thanks alot

Hello!

Classic ABis uses PDH over E1: each 64 kbit/s Abis TS is assigned to specific TRX/TG and it can be routed separately, and it is treated separately. A lot of functionality tries to make better use of Abis capacity.

Packet Abis groups all TRXes in TG into one big pipe. It can be PDH or IP: when PSH, TS 64 kbit/s sructure does not exist and all TS have to be routed over same paths.

Now to answers: Flex/Abis is redundand: packet Abis has same functionality build in (it is packet...).
Same with LAPD: as everything is multiplexed in one big pipe, there is no need for special functionality to multiplex
data streams into specific PDH TS.

BR
s52d

[islam wagih]

Hello!

Classic ABis uses PDH over E1: each 64 kbit/s Abis TS is assigned to specific TRX/TG and it can be routed separately, and it is treated separately. A lot of functionality tries to make better use of Abis capacity.

Packet Abis groups all TRXes in TG into one big pipe. It can be PDH or IP: when PSH, TS 64 kbit/s sructure does not exist and all TS have to be routed over same paths.

Now to answers: Flex/Abis is redundand: packet Abis has same functionality build in (it is packet...).
Same with LAPD: as everything is multiplexed in one big pipe, there is no need for special functionality to multiplex
data streams into specific PDH TS.

BR
s52d

Really, thank you for your reply but could you explain with more details as I didn't get the point.

[s52d]

Hi!

Cicuit switched system, like old telephone:
- You need three pairs of wires to handle three telephones

Packet switched system, like ethernet:
- three PCs share same line, they just use capacity when they need.


Classic Abis: each TRX has twice two wires (64 k timeslots in 2 Mbit/sec E1 line) + some for signalling.
Each capacity is assagned and used regardless of the traffic.
So, you know exactly which bit in 2 Mbit/s belongs to which TRX and which TS or signalling.


Packet Abis: all TRXes, users + signalling are multiplexed into ONE big pipe.
So every bit can be used by any TRX.

Thus, functionality to handle TS more efficient (Flex Abis etc) make sense in CS/PDH world, but it is not needed
in packet system. Multiplexing is essential part of any packet system.

Of course, you might enjoy more obvious optional features. Also, you can do packet Abis over PDH, fractional E1 or Ethernet.
In my mind, only real native packet Abis/ethernet is to be used (yes, you need SIU/TCU with E/// RBSes).

Good checkpoint to test any Abis system: what happens if there is no traffic on GSM cell?
Real Abis/IP is almoust empty, while pseudowire (CES) still keeps transport buys by sending empty frames.

BR
s52d