33(57)
Datum/Date
Rev
Dokumentnr/Documentnr
Uppgjord/Prepared
Dokansv/Godkänd - Doc respons/Approved
Kontr/Checked
Tillhör/Referens-File/Reference
1999-07-15
V
1531-BDV 113 08 Uen
INSTALLATION INSTRUCTION
Faktaansvarig - Subject responsible
feeding Pairs (EPP) need to be wired. The maximum wire length between BS (fed locally) and IC-LU is only data lim-
ited and may reach up to 1900 meters.
In any case the total current capability of the power supply(s) has to be considered. Refer to chapter power consump-
tion of the telephones when calculating total system power demand.
Usually the ranges mentioned above will be sufficient for most installations. For special cases where greater distanc-
es have to be covered, see
. Install the board in the cabinet, after the prerequisites mentioned
in
have been provided.
6.2
Traffic capacity
The traffic capacity of the Cordless part of the PBX is mainly determined by the IC-CU_ and in exceptional cases also
by the Base Stations. The IC-CU can handle a maximum of 56 simultaneous calls and the IC-CU2 can handle up to
60 simultaneous calls. Each Base Station has a capacity of 8 simultaneous calls.
The traffic capacity of the IC-CU_ is determined by:
•
the Grade Of Service (GOS) required by the customer
•
the number of speech circuits available, with a limit of 64.
The Grade Of Service is the probability that a call is rejected because of system congestion. The customer has to in-
dicate which Grade Of Service is acceptable. A Grade Of Service of 1%, or 0.01, means an average of 1 lost call in
every 100 calls.
The IC-CU2 and each IC-LU is equipped with a SPU providing 8 speech circuits that are shared by the whole cord-
less system. So the number of installed (up to 7) IC-LUs determine how many circuits are available to the system.
The two parameters mentioned above (GOS and the number of speech circuits) and the total amount of traffic (Er-
lang) that is required, are related to each other. The table below shows the capacity at a required GOS. Practically,
this table is used to calculate from a given GOS and Erlang value the number of IC-LUs needed. The Erlang value is
the total traffic generated by all portables. The table below shows the Erlang values for a number of speech channels
and at a required GOS.
For the calculation it is necessary to estimate the time the portables actually make calls. The table below shows the
Erlang value depending on the estimated mean call-minutes for a portable telephone. These values may be different
between departments depending on their activities. These values multiplied by the number of portables result in a
traffic capacity that has to be provided.
Speech
Systems with IC-CU2
Grade of service (GOS)
2%
1%
0.5%
0.1%
1
8
2
16
3
24
4
32
5
40
6
48
3.6
9.8
16.6
23.8
31
38.4
3.2
8.9
15.3
22.1
29
36.1
2.7
8.1
14.2
20.6
27.3
34.2
2.1
6.7
12.2
18.2
24.5
30.9
7
56
45.9
43.3
41.2
37.5
circuits
Number of IC-LUs
1
2
3
4
5
6
7
64
0
-
Systems with IC-CU
Number of IC-LUs
Note: 64 speech chan-
nels are available but only
60 portables can simulta-
neously initiate calls
53.4
50.6
48.3
44.2