34(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
Example:
A customer ordering a system with 55 portable telephones estimates that each portable generates 200 mE traffic in
average. These values require a system with a traffic capacity of 11 E (0,2x55). With an accepted GOS of 0.5% the
number of IC-LUs is found as follows:
The total traffic is 11 E. In the column of 0.5% GOS, the next higher value of 11 E is 14.2 E, resulting in 3 IC-LUs.
So, the system shall be equipped with 3 IC-LUs, offering the client 14.4 E in stead of 11. This means that the sys-
tem has an over-capacity of 3.2 E, which allows expansion of the system with 16 portables without reducing the
Grade Of Service nor the need of more IC-LUs.
Thus 56 circuits with an accepted GOS of 0.5% result in a maximum traffic capacity of 41.2 E for the system.
6.2.1
Traffic Capacity of Base Stations
A Base Station, having 8 channels available, has an Erlang value of 2.7 with a GOS of 0.5%. This means that each
Base Station can serve 18 portables, assuming each portable generates 150 mE during busy hour or 13.5 portables
generating 200 mE each.
Example:
Assuming a full coverage in a building can be achieved with 4 Base Stations means that 55 portables generate to-
gether 55 x 0.200 = 11 E, while the Base Stations traffic capacity is only 4 x 2.7 = 10.8 Erlang. This is insufficient so
another Base Station in the area of the busiest part of the company has to be added.
Practically, the total capacity offered by the cordless network is generally more than sufficient, but this is from an av-
erage point of view. In certain places, traffic demands may vary such that locally the network is often blocked, or has
a lower GOS than required. For instance a purchase department may easily generate 300 mE per Portable during
busy hour, thus, when e.g. with 6 persons giving a very high load on the Base Station close by. It may be necessary
to add a Base Station in this area to have enough capacity for others to call as well. Also think of e.g. canteens during
lunch time etc.
mErlang
Minutes
per hour
50
3
100
6
150
9
200
12
mErlang
Minutes
per hour
250
15
300
18
500
30
750
45