Contents Telektronikk - Telenor

Table 9 Number of call attempts, successful rate for outgoing calls, and traffic
128
istrations from 1989 [4] show that the
number of successful outgoing calls was
only about 10 % more than that for incoming
calls3 . The reasons for the first
explanation are:
- incoming call attempts are not registered
until they have reached the main
exchange in UNIT/SINTEF, which has
virtually no blocking
- the exchange has advanced forwarding
functions
- all outgoing call attempts are registered
before they reach the public network
- outgoing calls are made to an inhomogeneous
group of users, which on average
has a higher probability of busy or
no answer.
One reason that outgoing calls have
shorter holding times is that users tend to
make shorter calls when they know that
their telephone calls are registered internally.
(When the METRO-system was
installed, a reduction in mean call holding
was observed). Another reason could
be that many users outside UNIT/SIN-
TEF do not have forwarding functions,
Table 10 The busy hour for outgoing traffic
Outgoing Incoming Total
Number of call attempts (percentage) 93278 (58.4 %) 66431 (41.6 %) 159709 (100 %)
Number of successful calls (success rate) 57438 (61.6 %) (N/A) (N/A)
Traffic (percentage) 54.0 (47.6 %) 59.4 (52.4 %) 113.4 (100 %)
3 To be correct we should notice that
RiT was connected to the exchange in
1989, but not to the present one.
so several short calls (attempts) could be
made instead of one long call (which
uses forwarding).
3.6.2 Use of switchboard operators
The charging files register whether a successful
outgoing call is set up manually
by switchboard operators. The number of
such calls is then compared with the total
number of (successful, outgoing) calls
during the same periods (Periods 1 and
2). The results show that less than 1 % of
these calls have been set up manually. In
Period 1, only 836 out of 114,949 were
set up manually, while the corresponding
numbers in Period 2 are 824 and
121,935. The result is a bit surprising,
since the percentage was considerably
higher (2.7 %) in an earlier study made
only 2 years before (in 1989 [4]). It indicates
that the use of switchboard operators
had been very much reduced from
1989 to 1991.
For incoming calls the registration was
based on the number of call attempts.
The registration took place in Period 4
(Jan. 13 – 14 1992). A total of 31,693
incoming call attempts were registered,
and among them 3,323 (i.e. 10.5 %) were
set up by switchboard operators. In other
words, 89.5 % of call attempts were
made directly without use of switchboard
operators. The observations made in
Period 1 (Oct 7 – 20, 1991) Period 2 (Nov 25 – Dec 8, 1991)
Day of week Traffic Time interval Traffic Time interval
Monday 90.433 1400 – 1500 95.227 1430 – 1530
Tuesday 84.694 1415 – 1515 96.139 1345 – 1445
Wednesday 85.547 1345 – 1445 93.646 1300 – 1400
Thursday 84.687 1315 – 1415 92.512 1315 – 1415
Friday
Time consistent
83.586 1315 – 1415 91.356 1430 – 1530
busy hour 83.715 1315 – 1415 92.205 1315 – 1415
1989 [4] show that 82.6 % of incoming
call attempts used direct dialling. Thus,
even the incoming traffic load on operators
has been reduced a lot.
When comparing our results with the
results from 1989 [4] we should notice
that the Regional Hospital of Trondheim
(RiT) was connected to the exchange in
1989, but not since January 1990. It is
likely that a larger portion of the calls
made to RiT use switchboard operators
than that to UNIT and SINTEF. Apart
from that there is reason to believe that
better information and a more convenient
system from users’ point of view contribute
to the reduced need for manual
assistance.
3.6.3 Traffic concentration
Traffic concentration is a measure of
traffic variations over time.
Before we start discussing the traffic
concentration, we first take a look at the
Busy hour.
The busy hour is defined as the 4 consecutive
15 minute periods during a day
with the highest traffic.
We have calculated busy hour (for outgoing
traffic) for each weekday in Periods 1
and 2. The results are shown in Table 10.
In the table we also show the Time consistent
busy hour, which is defined in a
similar way as the busy hour, but the traffic
in each period is the average over all
days of the observation period.
Table 10 shows that the busy hour without
exception appears after lunch. The
time consistent busy hour for Periods 1
and 2 coincide, and the busy hour for
each day starts between 1300 and 1400.
The traffic intensity during the busy hour
follows the same pattern as for the average
traffic intensity during a day: Most
traffic in the beginning of a week, and
least traffic on Friday. There is also a
clear increase of traffic during busy hour
from Period 1 to Period 2.
Based on the available data the busy hour
for the total two-way traffic in Period 3
(Nov. 25 – 29 1991 between 0700 and
1900) have also been calculated. The
results are shown in Table 11. It shows
that the busy hour for total traffic occurs
at approximately the same intervals, i.e.
starting at between 1300 and 1400.
Now we can give the definition of the
Traffic concentration, which is the relation
between the mean traffic in the busy
hour and the mean traffic in the 24 hour