• GSM Interface Capacity Planning

By breif, before going to the calcuation, if you are fully understandning about E1/T1 capacity, that is fine to go through the method below. But if you are beginner, I would suggest you to see the E1/T1 to get an idea and concept first.

Well, I would mention that all the calcuation is based on my working experience, so that if I'm wrong or if you have more idea to share, please! I'm very pleased to join with you.

A-bis Interface Capacity Planning: 
4 Tyep of information can be transmitted over the A-bis:

1. User Information
2. Synchronization Data
3. Sysnalling Data and
4. Data for operation and maintenance of the BTS, known as O&M alarm

Let talk abit about E1:

 1E1=32TS (2Mbps), 30 TS for Traffic Channel (PCM30). (TS0= Synchronizing and TS16=Signalling)

- 1 TS E1=64kbps. (Containing of 4 Sub TS, 1 Sub TS=16kbps)
- 1 TRx = 8 TS (1 TS TRx= 16kbps, 13kbps for payload data, 3kbps for inband signalling)

==> 1TRx = 8TS *16kbps= 128kbps. By: 128kbps/64kbps =2 TS E1
So,   1 TRx occupied 2 TS E1
==> 30TS E1 can configure up to 15TRx, but I would suggest to configure in max 13TRx.
* BSC6900: Optic Interface Board IOUa can configue up 63E1 (1 STM-1) in which can support 384 TRx

Ater Interface Capacity Planning:
Introduction: The Ater interface is an internal interface between the MPS/EPS and the TCS in the Huawei BSS equipment. With this feature, the Ater resources are classified into 16 kbit/s timeslots and 8 kbit/s timeslots. The BSC allocates the Ater resources according to the channel type during the call establishment. If TCHFs are allocated on the Um interface, 16 kbit/s timeslots are used on the Ater interface. If TCHHs are allocated on the Um interface, 8 kbit/s timeslots are used on the Ater interface. Thus, the Ater resources are fully utilized.

The Ater resources of Huawei BSC are classified into 16 kbit/s Ater resource pool and 8 kbit/s Ater resource pool. If TCHFs are allocated on the Um interface, 16 kbit/s Ater resources are allocated; if TCHHs are allocated on the Um interface, 8 kbit/s Ater resources are allocated. The BSC not only allocates and manages the resources in the pools but also adjusts the allocation of Ater resources between the two pools according to the remains in each pool.

Well, now please you ignore about TCHF and TCHH that how ater will be switching resource pool, there is a feature of Flex Ater to work on this job. 

Now, again there is a related closed with E1!

 Tips:

 120 Traffic Channel = PCM30 (2Mbps)
- 64Kbps for S7
- 64kbps for NMS
- Blocking 1%

Quiz: At Busy hour, BSC Traffic reach 9800Erl, So how many E1 we need to handle the Ater Traffic ? 

Now let start with Microsoft Excel to assist you with this job. 
Assume that there are 120 Traffic Channel (16kpbs) in 1 E1. So let use erlangB_traffic to convert from number of TS to Erlang with blocking rate 1%.

- erlangB_traffic(120,0.01)=102.963Erl
- BSC Peak traffic: 9800Erl, So 9800/102.963=95.179 E1
* To prevent over load usage, so you have to set the Threshold: 85%
==> Add 85% Gap=95.179 +95.179 *(1-0.85)=109.45~110 E1
Totally, you need 106 E1 Ater interface to handle the BSC traffic at busy hour 9800Erl 
*Ater interface Board, 1 OIUa=63E (STM-1), so  110/63=1.74~2 Boards (Active) + 2 Boards (standby)

TC Resource Capacity Board Planing
- Suppose that 1 BSC has 1506 TRx (Boad: DPUc/DPUa)
- 1 TRx = 3.6Erl
- So, 3.6*1506 = 5421 Erl (Traffic that TC will be handle)
- 1 DPUc/DPUa =960 Erl
==> 5421/960 = 5.64~ 6 Boards
* Add 1 more board to prevent the traffic increas in some case and hardware protection.
Totally you need 7 Boards for TC Resource pool.

A Interface Capacity Planing

I think that there is no need to talk much about A Interface, just see the illustrate below than I believe can image how to plan.

See? just mutiply by 4 is OK !