ND SatCom SKYWAN IDU 1070, Руководство пользователя

Страница: 48 / 154

44 Network Design and Engineering Guide 2010-10-26
General Carrier Design
Network Traffic Estimation
2.4.1 Capacity Calculation Tool
To calculate the traffic requirement for the whole network a spreadsheet like the ’ND SatCom
Academy Capacity Calculator’ may be used which will be presented in the following pages. The
capacity calculator is an Excel tool which consists of several worksheets:
- Capacity calculation
- Erlang calculation sheet
- Voice traffic sheet
- Carrier configuration
- TDMA calculator input.
Capacity Calculation Worksheet
The capacity calculation worksheet allows the input of the following parameters:
- Number of stations per type (up to 4 station types possible).
- Number of voice interfaces per station.
- Real-time traffic (either per station or for the whole network) in receive direction.
- IP and Frame Relay non real-time traffic per station in receive direction.
Input fields in this spreadsheet are indicated by a grey background. The following picture
presents a work sheet filled with data from the example presented in this section:
Figure 2-26 Traffic Calculation Example - Capacity Worksheet
The main results in this worksheet are:
- Network traffic requirement per traffic type (voice, real-time, FR non real-time, IP non real-
time)
- Total network traffic requirement
Voice traffic requirements will be calculated with the Erlang worksheet. The result of this calcu-
lation is indicated by the blue fields in the capacity calculation sheet.
Whereas the definition of non real-time traffic per station is straightforward, high bandwidth
real-time traffic may be more difficult to specify.
In the example considered so far, only one bidirectional video conference between the two sta-
tions of type 1 (head office) with a data rate of 256 kbps per direction is required. In this case
it is correct to define a real-time traffic requirement of 256 kbps per station of type 1.
In another scenario the situation is not so clear anymore. Let’s assume that the customer re-