Product manual
Configuration directions, Traffic capacity of the system
Technical Product Manual - DCT1800-GAP
TD 92093 (1/LZBNB 103 108 R4D) / 2006-03-09/ Ver.C
© 2006
31
Chapter 6 Traffic capacity of the system
The traffic capacity of the DCT1800-GAP system is mainly determined by the radio exchange and in
exceptional cases also by the base stations. The radio exchange can handle a maximum of 60
simultaneous calls and a single base station has a capacity of 8 simultaneous calls.
6.1 Traffic capacity of the radio exchange
The traffic capacity of the radio exchange is determined by:
• Grade Of Service (GOS) accepted by the customer
• Number of speech circuits available, with a limit of 60
The grade of service is the probability that a call cannot be made because of congestion in the system.
The customer has to indicate 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.
SPU-S and SLU boards provide for 8 speech circuits. So, if totally 8 SPU-S and SLU boards are
installed, 64 circuits are available, of which only 60 can be used simultaneously, as the DCT1800-
GAP system can handle only a maximum of 60 simultaneous calls.
The two parameters mentioned above (GOS and number of speech circuits) and the total amount of
traffic (erlang) that is required, are related to each other. Table
5 below shows an excerpt of these
relations. Practically, this table is used to calculate from a given GOS and erlang value the number of
SPU-Ss/SLUs needed. The erlang value is the total traffic generated by all cordless phone users.
Table 6 shows what erlang values practically mean in call-minutes for a cordless phone
.
Number of
SPU-Ss/
SLUs
Speech
circuits
Grade Of Service (GOS)
2% 1% 0.5% 0.1%
1 8 3.6 3.2 2.7 2.1
2 16 9.8 8.9 8.1 6.7
3 24 16.6 15.3 14.2 12.2
4 32 23.8 22.1 20.6 18.2
5 40 31.0 29.0 27.3 24.5
6 48 38.4 36.1 34.2 30.9
7 56 45.9 43.3 41.2 37.5
8 60 49.7 46.9 44.8 40.8
Table 5 Erlang table-B values for given GOS and number of speech circuits
mE Minutes per hour mE Minutes per hour
50
100
150
200
3
6
9
12
250
300
500
750
15
18
30
45
Table 6 Erlang values expressed in call-minutes