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Fascicle II.3 _ Rec. E.521 11
All drawings appearing in this Recommendation have been done in
Autocad.
Recommendation E.521
CALCULATION OF THE NUMBER OF CIRCUITS IN A
GROUP CARRYING OVERFLOW TRAFFIC
A calculation of the number of circuits in a group carrying
overflow traffic should be based on this Recommendation and on
Recommendation E.522 dealing with high_usage groups.
The objective grade of service used is that the average
blocking during the busy_hour busy_hour of the 30 busiest days of
the year will not exceed 1%.
To determine the number of circuits in a group carrying
overflow traffic group carrying overflow traffic, three traffic
parameters are required: the average traffic offered to the group,
the weighted peakedness factor weighted peakedness factor, and the
level of day_to_day traffic variations.
The level of day_to_day traffic variations indicates the
degree to which the daily busy_hour traffic deviates from the
overall mean traffic, and is determined by the sample variance of
the 30 busy_hour traffic.
The peakedness factor indicates the degree to which the
variability of the traffic deviates from pure chance traffic within
a single hour, and in statistical terms is the variance_to_mean
ratio of the distribution of simultaneous overflow traffic.
1 Determination of the level of day_to_day traffic variations
Let M1, M2, . . ., M30 denote the 30 busy_hour loads of the
traffic offered to the final group. Determine the mean traffic M of
the daily traffic by
Equation was removed from the ASCII text version of this document.
Determine the sample variance Vd of the daily traffic by
Equation was removed from the ASCII text version of this document.
Determine the point (M, Vd) on Figure 1/E.521; M on the
horizontal axis, and Vd on the vertical axis.
i)If the point (M, Vd) is below the bottom curve, the level
of variation is Null.
ii) If the point is between the lower two curves, the level
of variation is Low.
iii) If the point is between the upper two curves, the level
of variation is Medium.
iv) If the point is above the highest curve, the level of
variation is High.
Default procedures: if the data are not available to compute
the variance Vd use the following guidelines:
a)If no more than 25 per cent of the traffic offered to the
final group is overflow from other groups, assume the level
of day_to_day variation is Low.
b)Otherwise, assume a Medium level of variation.
Figure 1/E.521 - CCITT 48080
2 Determination of peakedness factor z
Peakedness factors depend principally upon the number of
high_usage circuits over which random traffic has access. When the
number of such high_usage circuits does not exceed 30, the actual
peakedness of the traffic overflowing from a high_usage group will
be only slightly below the maximum peakedness values1),2). The
maximum peakedness values are given in Table 1/E.521.
TABLE 1/E.521
Maximum peakedness factor zi
Number of Peakedness Number of Peakedness
high_usage factor high_usage factor
circuits (zi) circuits (zi)
(ni) (ni)
1 1.17 16 2.44
2 1.31 17 2.49
3 1.43 18 2.55
4 1.54 19 2.61
5 1.64 20 2.66
6 1.73 21 2.71
7 1.82 22 2.76
8 1.90 23 2.81
9 1.98 24 2.86
10 2.05 25 2.91
11 2.12 26 2.96
12 2.19 27 3.00
13 2.26 28 3.05
14 2.32 29 3.09
15 2.38 30 3.14
For more than 30 circuits, the peakedness of the traffic
overflowing from a high_usage group i of ni circuits is given by
Equation was removed from the ASCII text version of this document.
where
Aiis the mean (random) traffic offered to the ni circuits and
ßiis the traffic overflowing. The overflow traffic ßi is
found by employing the standard Erlang loss formula E1, ni
(Ai):
Equation was removed from the ASCII text version of this document.
The weighted mean peakedness factor z, is then calculated
from:
Equation was removed from the ASCII text version of this document.
for the h parcels of traffic being offered to the final group.
Note that for the traffic directly offered to the final group,
the peakedness factor is zi = 1.
3 Determination of the mean traffic offered to the final group
and the number of circuits required
3.1 For planning future network requirements, the traffic
overflowing to a final group should be determined theoretically
from forecasts of traffics offered to the high_usage groups.
The mean traffic overflowing to the final group from a
high_usage group high_usage group is determined in two steps:
i)the "single_hour" overflow traffic ßi overflowing from ni
circuits is given as above by
Equation was removed from the ASCII text version of this document.
when Ai is the forecast of traffic offered to the ith
high_usage group;
ii) the average overflow traffic overflowing from the ni
circuits is then determined by adjusting the single_hour
traffic ßi for the effect of day_to_day traffic variations.
Equation was removed from the ASCII text version of this document.
The adjustment factor ri is given in Table 2/E.521; it is a
function of:
_ the offered traffic Ai,
_ the traffic AiEi, ni_1 (Ai) _ ßi carried by the last trunk
i, and
_ the level of day_to_day variations of the traffic offered
to the high_usage group.
This level can be determined using the method described in 1
above, but applying it to measurements of traffic offered to the
high_usage group. If such measurements are not available a medium
level can be used.
The mean traffic offered to the final group is then the sum of
all over the h parcels of traffic:
Equation was removed from the ASCII text version of this document.
It can be assumed that the level of day_to_day traffic
variations on the final group remains constant over the forecast
time period.
Using the level of day_to_day traffic variation as determined
in 1 above on the final group and the peakedness factor of 2
above, the appropriate table of Tables 3/E.521 to 6/E.521 is used
to derive the number of circuits required.
Note 1 _ This method of calculation of the mean traffic
offered to the final group is valid only if the overflow traffic
due to blocking encountered in the exchange in the attempts to
connect to a high_usage, is negligible.
Note 2 _ Table 3/E.521 differs slightly from the previous
tables published by CCITT, although in Table 3.1/E.521 there is no
allowance for day_to_day variations. The new table takes into
account a systematic bias in the measurement procedure that is
based on a finite period of time (1 hour), instead of an infinite
period as was assumed in the previous table [5].
Note 3 _ Tables 4/E.521, 5/E.521 and 6/E.521 are based on the
calculation of the average blocking from the formula:
Equation was removed from the ASCII text version of this document.
where
B(m) is the single_hour expected blocking and
f(m) is the density distribution of day_to_day traffic (m),
assuming a Pearson Type III distribution:
Equation was removed from the ASCII text version of this document.
M and Vd are the mean and day_to_day variance of the traffic as
calculated [5] in 1 above.
TABLE 2/E.521
Overflow adjustment for high_usage trunk groups
Factor ri
Last trunk traffic
Offered
traffic Low daily Medium daily High daily
Ai variation variation variation
0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.
25 3 4 5 6 25 3 4 5 6 25 3 4 5 6
3 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1.
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
5 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1.
0 0 0 0 0 1 1 1 0 0 2 2 1 1 0
7 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1.
0 0 0 0 0 2 2 1 1 0 4 3 2 1 1
10 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1.
1 1 1 0 0 3 2 2 1 1 5 4 3 2 1
15 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1.
2 1 1 1 0 5 4 2 2 1 8 6 4 3 1
20 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 2. 1. 1. 1. 1.
2 2 1 1 0 6 5 3 2 1 0 8 5 3 2
25 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 2. 2. 1. 1. 1.
3 2 2 1 1 8 6 4 3 1 3 0 7 4 2
30 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 2. 2. 1. 1. 1.
3 3 2 1 1 8 7 4 3 2 4 1 7 5 3
TABLE 3/E.521
Single_hour capacity, in Erlangs, as a function of the number of
trunks and of the peakedness factor
Parameters: _ Blockage 0.01;
_ No allowance for day_to_day variation;
_ Weighted mean peakedness factor.
Numb
er 1. 1. 1. 1. 1. 2. 2. 2. 2. 2. 3. 3. 3. 4.
of 0 2 4 6 8 0 2 4 6 8 0 4 8 0
trun
ks
requ
ired
1 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.
06 0 0 0 0 0 0 0 0 0 0 0 0 0
2 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.
22 0 0 0 0 0 0 0 0 0 0 0 0 0
3 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.
53 33 0 0 0 0 0 0 0 0 0 0 0 0
4 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.
94 69 50 0 0 0 0 0 0 0 0 0 0 0
5 1. 1. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.
42 14 89 67 0 0 0 0 0 0 0 0 0 0
6 1. 1. 1. 1. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.
97 64 36 08 0 0 0 0 0 0 0 0 0 0
7 2. 2. 1. 1. 1. 0. 0. 0. 0. 0. 0. 0. 0. 0.
56 19 86 58 31 0 0 0 0 0 0 0 0 0
8 3. 2. 2. 2. 1. 1. 0. 0. 0. 0. 0. 0. 0. 0.
19 81 44 11 81 53 0 0 0 0 0 0 0 0
9 3. 3. 3. 2. 2. 2. 1. 1. 0. 0. 0. 0. 0. 0.
83 42 03 67 36 03 75 50 0 0 0 0 0 0
10 4. 4. 3. 3. 2. 2. 2. 2. 1. 0. 0. 0. 0. 0.
53 08 67 28 92 58 28 00 75 0 0 0 0 0
11 5. 4. 4. 3. 3. 3. 2. 2. 2. 1. 0. 0. 0. 0.
22 75 31 89 53 17 83 53 25 97 0 0 0 0
12 5. 5. 4. 4. 4. 3. 3. 3. 2. 2. 2. 0. 0. 0.
94 44 97 56 14 78 42 08 78 47 22 0 0 0
13 6. 6. 5. 5. 4. 4. 4. 3. 3. 3. 2. 0. 0. 0.
67 14 64 19 81 39 03 67 33 03 72 0 0 0
14 7. 6. 6. 5. 5. 5. 4. 4. 3. 3. 3. 2. 0. 0.
42 86 36 89 44 03 67 28 94 61 28 69 0 0
15 8. 7. 7. 6. 6. 5. 5. 4. 4. 4. 3. 3. 0. 0.
17 58 06 58 11 69 31 92 56 19 86 22 0 0
16 8. 8. 7. 7. 6. 6. 5. 5. 5. 4. 4. 3. 3. 0.
94 33 78 28 81 36 94 56 17 81 44 81 19 0
17 9. 9. 8. 8. 7. 7. 6. 6. 5. 5. 5. 4. 3. 3.
72 08 50 00 50 06 61 19 81 42 06 39 75 44
18 10 9. 9. 8. 8. 7. 7. 6. 6. 6. 5. 4. 4. 4.
.5 83 25 72 22 75 31 86 44 06 69 97 31 00
0
19 11 10 10 9. 8. 8. 7. 7. 7. 6. 6. 5. 4. 4.
.3 .6 .0 44 92 44 97 53 11 72 33 58 89 58
1 1 0
20 12 11 10 10 9. 9. 8. 8. 7. 7. 6. 6. 5. 5.
.0 .3 .7 .1 67 14 67 22 81 39 97 22 50 17
8 9 8 9
21 12 12 11 10 10 9. 9. 8. 8. 8. 7. 6. 6. 5.
.8 .1 .5 .9 .3 86 39 92 47 06 64 86 11 78
9 9 3 4 9
22 13 13 12 11 11 10 10 9. 9. 8. 8. 7. 6. 6.
.7 .0 .3 .6 .1 .6 .0 61 17 72 31 50 75 39
2 0 1 9 4 1 8
23 14 13 13 12 11 11 10 10 9. 9. 8. 8. 7. 7.
.5 .7 .0 .4 .8 .3 .8 .3 86 42 97 17 39 00
3 8 8 7 9 6 1 3
24 15 14 13 13 12 12 11 11 10 10 9. 8. 8. 7.
.3 .5 .8 .2 .6 .0 .5 .0 .5 .1 67 83 03 64
6 8 9 2 4 8 6 3 6 1
25 16 15 14 14 13 12 12 11 11 10 10 9. 8. 8.
.1 .3 .6 .0 .3 .8 .2 .7 .2 .8 .3 50 69 31
9 9 7 0 9 3 8 8 8 1 6
26 17 16 15 14 14 13 13 12 12 11 11 10 9. 8.
.0 .2 .4 .8 .1 .5 .0 .5 .0 .5 .0 .1 36 94
3 2 7 1 7 8 3 0 0 3 6 9
27 17 17 16 15 14 14 13 13 12 12 11 10 10 9.
.8 .0 .2 .5 .9 .3 .7 .2 .7 .2 .7 .8 .0 61
6 3 8 8 4 3 8 2 2 2 5 6 3
28 18 17 17 16 15 15 14 13 13 12 12 11 10 10
.6 .8 .0 .3 .7 .1 .5 .9 .4 .9 .4 .5 .6 .2
9 6 8 6 2 1 3 7 4 4 7 6 9 8
29 19 18 17 17 16 15 15 14 14 13 13 12 11 10
.5 .6 .8 .1 .5 .8 .2 .7 .1 .6 .1 .2 .3 .9
6 9 9 7 0 6 8 2 9 7 9 8 9 4
30 20 19 18 17 17 16 16 15 14 14 13 12 12 11
.3 .5 .7 .9 .2 .6 .0 .4 .9 .4 .9 .9 .0 .6
9 3 2 7 8 4 6 7 2 2 2 7 8 4
31 21 20 19 18 18 17 16 16 15 15 14 13 12 12
.2 .3 .5 .7 .0 .4 .8 .2 .6 .1 .6 .6 .7 .3
5 6 3 8 8 2 1 2 7 4 4 9 8 3
32 22 21 20 19 18 18 17 17 16 15 15 14 13 13
.1 .1 .3 .5 .8 .2 .5 .0 .4 .8 .3 .3 .4 .0
1 9 6 8 9 2 8 0 2 9 6 9 7 3
33 22 22 21 20 19 19 18 17 17 16 16 15 14 13
.9 .0 .1 .3 .6 .0 .3 .7 .1 .6 .1 .1 .1 .7
7 6 9 9 7 0 6 5 9 4 1 1 7 2
34 23 22 22 21 20 19 19 18 17 17 16 15 14 14
.8 .8 .0 .2 .4 .8 .1 .5 .9 .3 .8 .8 .8 .4
3 9 0 2 7 1 4 3 4 9 6 6 9 2
35 24 23 22 22 21 20 19 19 18 18 17 16 15 15
.6 .7 .8 .0 .2 .5 .9 .3 .6 .1 .6 .5 .6 .1
9 5 3 3 8 8 2 1 9 4 1 8 1 4
36 25 24 23 22 22 21 20 20 19 18 18 17 16 15
.5 .5 .6 .8 .1 .3 .7 .0 .4 .8 .3 .3 .3 .8
8 8 9 6 1 9 2 8 7 9 6 1 1 3
37 26 25 24 23 22 22 21 20 20 19 19 18 17 16
.4 .4 .5 .6 .9 .1 .5 .8 .2 .6 .1 .0 .0 .5
4 4 3 9 2 9 0 6 5 7 1 6 6 6
38 27 26 25 24 23 23 22 21 21 20 19 18 17 17
.3 .3 .3 .5 .7 .0 .3 .6 .0 .4 .8 .8 .7 .2
1 1 6 3 2 0 1 4 3 4 6 1 8 8
39 28 27 26 25 24 23 23 22 21 21 20 19 18 18
.1 .1 .2 .3 .5 .8 .1 .4 .8 .1 .6 .5 .5 .0
9 7 2 6 6 1 1 4 1 9 4 3 0 0
40 29 28 27 26 25 24 23 23 22 21 21 20 19 18
.0 .0 .0 .1 .3 .6 .8 .2 .5 .9 .3 .2 .2 .7
8 3 6 9 9 1 9 2 8 7 9 8 5 2
41 29 28 27 27 26 25 24 24 23 22 22 21 19 19
.9 .8 .9 .0 .1 .4 .6 .0 .3 .7 .1 .0 .9 .4
4 9 2 3 9 4 9 3 6 5 7 6 7 7
42 30 29 28 27 27 26 25 24 24 23 22 21 20 20
.8 .7 .7 .8 .0 .2 .5 .8 .1 .5 .9 .8 .7 .1
3 5 8 6 3 5 3 1 7 3 4 1 2 9
43 31 30 29 28 27 27 26 25 24 24 23 22 21 20
.7 .6 .6 .7 .8 .0 .3 .6 .9 .3 .6 .5 .4 .9
2 4 1 2 6 8 3 1 4 1 9 6 7 4
44 32 31 30 29 28 27 27 26 25 25 24 23 22 21
.6 .5 .4 .5 .6 .8 .1 .4 .7 .1 .5 .3 .2 .6
1 0 7 6 9 9 4 2 5 1 0 3 2 9
45 33 32 31 30 29 28 27 27 26 25 25 24 22 22
.5 .3 .3 .4 .5 .7 .9 .2 .5 .8 .2 .0 .9 .4
0 9 3 2 3 2 4 2 6 9 8 8 7 2
46 34 33 32 31 30 29 28 28 27 26 26 24 23 23
.3 .2 .1 .2 .3 .5 .7 .0 .3 .6 .0 .8 .7 .1
9 5 9 5 9 6 8 3 3 9 6 6 2 7
47 35 34 33 32 31 30 29 28 28 27 26 25 24 23
.2 .1 .0 .1 .2 .3 .5 .8 .1 .4 .8 .6 .4 .9
8 4 8 1 2 9 8 6 4 7 3 4 7 2
48 36 35 33 32 32 31 30 29 28 28 27 26 25 24
.1 .0 .9 .9 .0 .2 .4 .6 .9 .2 .6 .4 .2 .6
7 0 4 7 6 2 2 7 4 8 4 2 5 9
49 37 35 34 33 32 32 31 30 29 29 28 27 26 25
.0 .8 .8 .8 .9 .0 .2 .4 .7 .0 .4 .1 .0 .4
6 9 1 1 2 6 5 7 5 8 2 9 0 4
50 37 36 35 34 33 32 32 31 30 29 29 27 26 26
.9 .7 .6 .6 .7 .8 .0 .3 .5 .8 .2 .9 .7 .1
7 8 7 7 5 9 8 1 8 9 2 7 8 9
TABLE 4/E.521
Single_hour capacity, in Erlangs, as a function of the number of
trunks and of the peakedness factor
Parameters: _ Blockage 0.01;
_ Low day_to_day variation allowance;
_ Weighted mean peakedness factor.
Numb
er 1. 1. 1. 1. 1. 2. 2. 2. 2. 2. 3. 3. 3. 4.
of 0 2 4 6 8 0 2 4 6 8 0 4 8 0
trun
ks
requ
ired
1 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.
06 0 0 0 0 0 0 0 0 0 0 0 0 0
2 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.
22 0 0 0 0 0 0 0 0 0 0 0 0 0
3 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.
53 33 0 0 0 0 0 0 0 0 0 0 0 0
4 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.
94 69 50 0 0 0 0 0 0 0 0 0 0 0
5 1. 1. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.
39 14 89 67 0 0 0 0 0 0 0 0 0 0
6 1. 1. 1. 1. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.
89 64 36 08 0 0 0 0 0 0 0 0 0 0
7 2. 2. 1. 1. 1. 0. 0. 0. 0. 0. 0. 0. 0. 0.
44 14 86 58 31 0 0 0 0 0 0 0 0 0
8 3. 2. 2. 2. 1. 1. 0. 0. 0. 0. 0. 0. 0. 0.
03 69 42 11 81 53 0 0 0 0 0 0 0 0
9 3. 3. 2. 2. 2. 2. 1. 1. 0. 0. 0. 0. 0. 0.
64 28 97 67 36 03 75 50 0 0 0 0 0 0
10 4. 3. 3. 3. 2. 2. 2. 2. 1. 0. 0. 0. 0. 0.
25 89 56 22 92 58 28 00 75 0 0 0 0 0
11 4. 4. 4. 3. 3. 3. 2. 2. 2. 1. 0. 0. 0. 0.
92 53 17 83 50 17 83 53 25 97 0 0 0 0
12 5. 5. 4. 4. 4. 3. 3. 3. 2. 2. 2. 0. 0. 0.
58 17 78 44 08 78 42 08 78 47 22 0 0 0
13 6. 5. 5. 5. 4. 4. 4. 3. 3. 3. 2. 0. 0. 0.
25 81 42 06 69 36 03 67 33 03 72 0 0 0
14 6. 6. 6. 5. 5. 4. 4. 4. 3. 3. 3. 2. 0. 0.
94 50 08 69 33 97 64 28 94 61 28 69 0 0
15 7. 7. 6. 6. 5. 5. 5. 4. 4. 4. 3. 3. 0. 0.
64 17 75 33 97 61 25 92 56 19 86 22 0 0
16 8. 7. 7. 7. 6. 6. 5. 5. 5. 4. 4. 3. 3. 0.
33 86 42 00 61 25 89 53 17 81 44 81 19 0
17 9. 8. 8. 7. 7. 6. 6. 6. 5. 5. 5. 4. 3. 3.
06 56 11 67 28 89 53 17 81 42 06 39 75 44
18 9. 9. 8. 8. 7. 7. 7. 6. 6. 6. 5. 4. 4. 4.
81 28 81 36 94 56 17 81 44 06 69 97 31 00
19 10 10 9. 9. 8. 8. 7. 7. 7. 6. 6. 5. 4. 4.
.5 .0 50 06 61 22 83 44 08 72 33 58 89 58
3 0
20 11 10 10 9. 9. 8. 8. 8. 7. 7. 6. 6. 5. 5.
.2 .7 .2 75 31 89 50 11 72 36 97 22 50 17
8 2 2
21 12 11 10 10 10 9. 9. 8. 8. 8. 7. 6. 6. 5.
.0 .4 .9 .4 .0 56 17 78 39 03 64 86 11 78
3 4 4 4 0
22 12 12 11 11 10 10 9. 9. 9. 8. 8. 7. 6. 6.
.7 .1 .6 .1 .6 .2 83 44 06 67 31 56 75 39
8 9 7 7 9 5
23 13 12 12 11 11 10 10 10 9. 9. 8. 8. 7. 7.
.5 .9 .3 .8 .4 .9 .5 .1 72 33 94 19 39 00
3 4 9 9 2 4 3 1
24 14 13 13 12 12 11 11 10 10 10 9. 8. 8. 7.
.3 .6 .1 .6 .1 .6 .2 .8 .3 .0 61 86 03 64
1 9 4 1 1 7 2 1 9 0
25 15 14 13 13 12 12 11 11 11 10 10 9. 8. 8.
.0 .4 .8 .3 .8 .3 .9 .5 .0 .6 .2 50 67 31
8 4 6 3 3 6 2 0 8 7 8
26 15 15 14 14 13 13 12 12 11 11 10 10 9. 8.
.8 .2 .6 .0 .5 .0 .6 .1 .7 .3 .9 .1 33 94
6 2 1 8 6 8 1 9 5 6 4 7
27 16 15 15 14 14 13 13 12 12 12 11 10 10 9.
.6 .9 .3 .8 .2 .8 .3 .8 .4 .0 .6 .8 .0 61
4 7 6 1 8 1 3 9 4 3 4 3 0
28 17 16 16 15 15 14 14 13 13 12 12 11 10 10
.4 .7 .1 .5 .0 .5 .0 .5 .1 .7 .3 .5 .6 .2
2 5 4 6 3 3 6 8 4 2 1 0 7 8
29 18 17 16 16 15 15 14 14 13 13 13 12 11 10
.2 .5 .8 .3 .7 .2 .7 .3 .8 .4 .0 .1 .3 .9
2 3 9 1 8 5 8 1 6 2 0 9 6 4
30 19 18 17 17 16 16 15 15 14 14 13 12 12 11
.0 .3 .6 .0 .5 .0 .5 .0 .5 .1 .6 .8 .0 .6
0 1 7 6 0 0 0 3 6 1 9 6 6 4
31 19 19 18 17 17 16 16 15 15 14 14 13 12 12
.8 .0 .4 .8 .2 .7 .2 .7 .2 .8 .3 .5 .7 .3
1 8 4 3 5 2 2 2 8 3 9 6 5 3
32 20 19 19 18 18 17 16 16 16 15 15 14 13 13
.6 .8 .1 .5 .0 .4 .9 .4 .0 .5 .1 .2 .4 .0
1 9 9 8 0 7 4 7 0 3 1 5 4 3
33 21 20 19 19 18 18 17 17 16 16 15 14 14 13
.3 .6 .9 .3 .7 .2 .6 .1 .7 .2 .8 .9 .1 .7
9 7 7 6 8 2 9 9 2 5 1 4 4 2
34 22 21 20 20 19 18 18 17 17 16 16 15 14 14
.2 .4 .7 .1 .5 .9 .4 .9 .4 .9 .5 .6 .8 .4
2 7 5 1 3 7 2 2 4 7 3 7 3 2
35 23 22 21 20 20 19 19 18 18 17 17 16 15 15
.0 .2 .5 .8 .2 .7 .1 .6 .1 .6 .2 .3 .5 .1
3 5 6 9 8 2 7 7 7 9 2 6 6 1
36 23 23 22 21 21 20 19 19 18 18 17 17 16 15
.8 .0 .3 .6 .0 .4 .9 .3 .8 .4 .9 .0 .2 .8
3 6 3 7 6 7 2 9 9 2 4 8 5 1
37 24 23 23 22 21 21 20 20 19 19 18 17 16 16
.6 .8 .1 .4 .8 .2 .6 .1 .6 .1 .6 .7 .9 .5
4 6 4 4 3 5 7 4 4 4 7 8 4 0
38 25 24 23 23 22 22 21 20 20 19 19 18 17 17
.4 .6 .9 .2 .6 .0 .4 .8 .3 .8 .4 .5 .6 .1
7 7 2 5 1 0 4 9 6 9 2 0 4 9
39 26 25 24 24 23 22 22 21 21 20 20 19 18 17
.2 .4 .7 .0 .3 .7 .1 .6 .1 .6 .1 .2 .3 .8
8 7 2 3 9 8 9 4 1 1 4 2 3 9
40 27 26 25 24 24 23 22 22 21 21 20 19 19 18
.1 .2 .5 .8 .1 .5 .9 .3 .8 .3 .8 .9 .0 .6
1 8 3 1 7 3 4 9 6 6 6 4 6 1
41 27 27 26 25 24 24 23 23 22 22 21 20 19 19
.9 .0 .3 .6 .9 .3 .7 .1 .6 .1 .6 .6 .7 .3
2 8 1 1 4 1 2 4 1 1 1 7 8 1
42 28 27 27 26 25 25 24 23 23 22 22 21 20 20
.7 .9 .1 .3 .7 .0 .4 .9 .3 .8 .3 .3 .4 .0
5 2 1 9 2 8 7 2 6 3 3 9 7 3
43 29 28 27 27 26 25 25 24 24 23 23 22 21 20
.5 .7 .9 .1 .5 .8 .2 .6 .1 .5 .0 .1 .1 .7
8 2 2 9 0 6 5 7 1 8 8 1 9 5
44 30 29 28 28 27 26 26 25 24 24 23 22 21 21
.4 .5 .7 .0 .3 .6 .0 .4 .8 .3 .8 .8 .9 .4
2 6 5 0 1 4 3 4 9 3 3 6 2 4
45 31 30 29 28 28 27 26 26 25 25 24 23 22 22
.2 .3 .5 .8 .0 .4 .8 .2 .6 .1 .5 .5 .6 .1
5 6 6 1 8 4 1 2 4 1 8 8 4 7
46 32 31 30 29 28 28 27 26 26 25 25 24 23 22
.0 .1 .3 .6 .8 .2 .5 .9 .4 .8 .3 .3 .3 .8
8 9 6 1 9 2 8 7 2 6 3 3 6 9
47 32 32 31 30 29 29 28 27 27 26 26 25 24 23
.9 .0 .1 .4 .6 .0 .3 .7 .1 .6 .0 .0 .1 .6
2 3 7 2 9 0 6 5 7 1 8 6 1 4
48 33 32 32 31 30 29 29 28 27 27 26 25 24 24
.7 .8 .0 .2 .4 .8 .1 .5 .9 .3 .8 .8 .8 .3
5 3 0 2 7 1 4 3 4 9 3 1 3 6
49 34 33 32 32 31 30 29 29 28 28 27 26 25 25
.5 .6 .8 .0 .2 .5 .9 .3 .7 .1 .5 .5 .5 .0
8 7 1 3 8 8 4 1 2 4 8 6 6 8
50 35 34 33 32 32 31 30 30 29 28 28 27 26 25
.4 .5 .6 .8 .0 .3 .7 .0 .5 .9 .3 .3 .3 .8
4 0 4 3 8 9 2 8 0 2 6 1 1 3
TABLE 5/E.521
Single_hour capacity, in Erlangs, as a function of the number of
trunks and of the peakedness factor
Parameters: _ Blockage 0.01;
_ Medium day_to_day variation allowance;
_ Weighted mean peakedness factor.
Numb
er 1. 1. 1. 1. 1. 2. 2. 2. 2. 2. 3. 3. 3. 4.
of 0 2 4 6 8 0 2 4 6 8 0 4 8 0
trun
ks
requ
ired
1 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.
06 0 0 0 0 0 0 0 0 0 0 0 0 0
2 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.
22 0 0 0 0 0 0 0 0 0 0 0 0 0
3 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.
53 33 0 0 0 0 0 0 0 0 0 0 0 0
4 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.
94 69 50 0 0 0 0 0 0 0 0 0 0 0
5 1. 1. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.
39 14 89 67 0 0 0 0 0 0 0 0 0 0
6 1. 1. 1. 1. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.
86 61 36 08 0 0 0 0 0 0 0 0 0 0
7 2. 2. 1. 1. 1. 0. 0. 0. 0. 0. 0. 0. 0. 0.
39 11 83 58 31 0 0 0 0 0 0 0 0 0
8 2. 2. 2. 2. 1. 1. 0. 0. 0. 0. 0. 0. 0. 0.
94 64 36 08 81 53 0 0 0 0 0 0 0 0
9 3. 3. 2. 2. 2. 2. 1. 1. 0. 0. 0. 0. 0. 0.
53 19 89 61 33 03 75 50 0 0 0 0 0 0
10 4. 3. 3. 3. 2. 2. 2. 2. 1. 0. 0. 0. 0. 0.
11 78 47 17 86 58 28 00 75 0 0 0 0 0
11 4. 4. 4. 3. 3. 3. 2. 2. 2. 1. 0. 0. 0. 0.
72 39 03 72 42 14 83 53 25 97 0 0 0 0
12 5. 4. 4. 4. 4. 3. 3. 3. 2. 2. 2. 0. 0. 0.
36 97 64 31 00 69 39 08 78 47 22 0 0 0
13 6. 5. 5. 4. 4. 4. 3. 3. 3. 3. 2. 0. 0. 0.
00 61 25 89 56 25 94 67 33 03 72 0 0 0
14 6. 6. 5. 5. 5. 4. 4. 4. 3. 3. 3. 2. 0. 0.
64 22 86 50 17 83 53 22 92 61 28 69 0 0
15 7. 6. 6. 6. 5. 5. 5. 4. 4. 4. 3. 3. 0. 0.
31 89 47 11 78 42 11 78 47 19 86 22 0 0
16 7. 7. 7. 6. 6. 6. 5. 5. 5. 4. 4. 3. 3. 0.
97 53 11 75 39 03 69 39 06 75 44 81 19 0
17 8. 8. 7. 7. 7. 6. 6. 5. 5. 5. 5. 4. 3. 3.
64 19 78 36 00 64 31 97 64 33 03 39 75 44
18 9. 8. 8. 8. 7. 7. 6. 6. 6. 5. 5. 4. 4. 4.
33 86 42 03 64 28 92 58 25 92 61 97 31 00
19 10 9. 9. 8. 8. 7. 7. 7. 6. 6. 6. 5. 4. 4.
.0 53 08 67 28 89 53 19 86 53 19 58 89 58
3
20 10 10 9. 9. 8. 8. 8. 7. 7. 7. 6. 6. 5. 5.
.6 .1 75 33 92 53 17 81 47 14 81 17 50 17
9 9
21 11 10 10 9. 9. 9. 8. 8. 8. 7. 7. 6. 6. 5.
.4 .8 .4 97 56 17 81 44 08 75 42 75 11 78
2 9 2
22 12 11 11 10 10 9. 9. 9. 8. 8. 8. 7. 6. 6.
.1 .5 .1 .6 .2 83 44 06 69 36 03 36 72 39
1 8 1 4 2
23 12 12 11 11 10 10 10 9. 9. 8. 8. 7. 7. 7.
.8 .2 .7 .3 .8 .4 .0 69 33 97 64 97 33 00
3 8 8 3 9 7 8
24 13 13 12 12 11 11 10 10 9. 9. 9. 8. 7. 7.
.5 .0 .4 .0 .5 .1 .7 .3 97 61 25 58 94 61
3 0 7 0 6 4 2 6
25 14 13 13 12 12 11 11 11 10 10 9. 9. 8. 9.
.2 .6 .1 .6 .2 .8 .3 .0 .6 .2 89 19 56 19
5 9 7 9 5 1 9 0 1 5
26 14 14 13 13 12 12 12 11 11 10 10 9. 9. 8.
.9 .4 .8 .3 .9 .4 .0 .6 .2 .8 .5 83 17 81
7 2 6 9 2 7 6 4 8 9 3
27 15 15 14 14 13 13 12 12 11 11 11 10 9. 9.
.6 .1 .5 .0 .6 .1 .7 .3 .9 .5 .1 .4 78 42
9 1 8 8 1 4 2 1 2 3 7 4
28 16 15 15 14 14 13 13 12 12 12 11 11 10 10
.4 .8 .2 .7 .2 .8 .3 .9 .5 .1 .8 .0 .3 .0
4 3 8 8 8 3 9 7 8 9 1 8 9 6
29 17 16 16 15 14 14 14 13 13 12 12 11 11 10
.1 .5 .0 .4 .9 .5 .0 .6 .2 .8 .4 .7 .0 .6
7 6 0 7 7 3 8 4 5 3 7 2 3 7
30 17 17 16 16 15 15 14 14 13 13 13 12 11 11
.9 .2 .7 .1 .6 .1 .7 .3 .9 .5 .1 .3 .6 .3
2 8 2 7 7 9 5 1 2 0 1 6 4 1
31 18 18 17 16 16 15 15 15 14 14 13 13 12 11
.6 .0 .4 .8 .3 .8 .4 .0 .5 .1 .7 .0 .2 .9
4 3 2 9 9 9 4 0 8 7 8 3 8 4
32 19 18 18 17 17 16 16 15 15 14 14 13 12 12
.3 .7 .1 .5 .0 .5 .1 .6 .2 .8 .4 .6 .9 .5
9 5 4 8 8 8 1 7 5 3 4 7 2 6
33 20 19 18 18 17 17 16 16 15 15 15 14 13 13
.1 .4 .8 .3 .7 .2 .8 .3 .9 .5 .1 .3 .5 .1
4 7 6 1 8 8 1 6 2 0 1 3 8 9
34 20 20 19 19 18 18 17 17 16 16 15 14 14 13
.8 .2 .6 .0 .5 .0 .5 .0 .6 .1 .7 .9 .2 .8
9 2 1 3 0 0 0 6 1 7 8 7 2 6
35 21 20 20 19 19 18 18 17 17 16 16 15 14 14
.6 .9 .3 .7 .2 .6 .1 .7 .2 .8 .4 .6 .8 .5
4 7 3 5 2 9 9 5 8 6 4 4 6 0
36 22 21 21 20 19 19 18 18 17 17 17 16 15 15
.3 .6 .0 .4 .9 .4 .9 .4 .9 .5 .1 .3 .5 .1
9 9 6 7 2 2 2 4 7 3 1 1 3 4
37 23 22 21 21 20 20 19 19 18 18 17 16 16 15
.1 .4 .8 .1 .6 .1 .6 .1 .6 .2 .8 .9 .1 .8
4 4 1 9 4 1 1 4 7 2 1 7 9 1
38 23 23 22 21 21 20 20 19 19 18 18 17 16 16
.8 .1 .5 .9 .3 .8 .3 .8 .3 .9 .4 .6 .8 .4
9 9 3 4 6 3 1 3 6 2 7 4 6 7
39 24 23 23 22 22 21 21 20 20 19 19 18 17 17
.6 .9 .2 .6 .0 .5 .0 .5 .0 .6 .1 .3 .5 .1
4 4 8 7 8 6 3 3 6 1 7 3 3 1
40 25 24 24 23 22 22 21 21 20 20 19 19 18 17
.4 .6 .0 .3 .8 .2 .7 .2 .7 .3 .8 .0 .1 .7
2 9 3 9 1 5 5 5 5 1 6 0 9 8
41 26 25 24 24 23 22 22 21 21 21 20 19 18 18
.1 .4 .7 .1 .5 .9 .4 .9 .4 .0 .5 .6 .8 .4
7 4 8 4 6 7 4 4 7 0 6 9 6 4
42 26 26 25 24 24 23 23 22 22 21 21 20 19 19
.9 .1 .5 .8 .2 .7 .1 .6 .1 .6 .2 .3 .5 .1
4 9 0 6 8 2 7 7 7 9 5 6 3 1
43 27 26 26 25 25 24 23 23 22 22 21 21 20 19
.7 .9 .2 .6 .0 .4 .8 .3 .8 .3 .9 .0 .1 .8
2 7 5 1 0 4 9 6 6 9 4 6 9 1
44 28 27 27 26 25 25 24 24 23 23 22 21 20 20
.4 .7 .0 .3 .7 .1 .6 .0 .5 .0 .6 .7 .8 .4
7 2 0 6 5 7 1 8 8 8 4 5 9 7
45 29 28 27 27 26 25 25 24 24 23 23 22 21 21
.2 .4 .7 .1 .4 .8 .3 .8 .3 .8 .3 .4 .5 .1
5 7 8 1 7 9 3 1 1 1 3 4 6 4
46 30 29 28 27 27 26 26 25 25 24 24 23 22 21
.0 .2 .5 .8 .2 .6 .0 .5 .0 .5 .0 .1 .2 .8
3 5 3 6 2 4 6 3 0 0 3 4 5 3
47 30 30 29 28 27 27 26 26 25 25 24 23 22 22
.8 .0 .2 .6 .9 .3 .7 .2 .7 .2 .7 .8 .9 .5
1 0 8 1 7 6 8 5 2 2 5 3 4 0
48 31 30 30 29 28 28 27 26 26 25 25 24 23 23
.5 .7 .0 .3 .7 .1 .5 .9 .4 .9 .4 .5 .6 .1
8 8 3 6 2 1 3 7 4 4 4 3 4 9
49 32 31 30 30 29 28 28 27 27 26 26 25 24 23
.3 .5 .8 .1 .4 .8 .2 .6 .1 .6 .1 .2 .3 .8
6 6 1 1 4 3 5 9 7 4 7 2 3 9
50 33 32 31 30 30 29 29 28 27 27 26 25 25 24
.1 .3 .5 .8 .1 .5 .0 .4 .8 .3 .8 .9 .0 .5
4 1 6 6 9 8 0 2 9 6 6 2 3 8
TABLE 6/E.521
Single_hour capacity, in Erlangs, as a function of the number of
trunks and of the peakedness factor
Parameters: _ Blockage 0.01;
_ High day_to_day variation allowance;
_ Weighted mean peakedness factor.
Numb
er 1. 1. 1. 1. 1. 2. 2. 2. 2. 2. 3. 3. 3. 4.
of 0 2 4 6 8 0 2 4 6 8 0 4 8 0
trun
ks
requ
ired
1 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.
06 0 0 0 0 0 0 0 0 0 0 0 0 0
2 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.
22 0 0 0 0 0 0 0 0 0 0 0 0 0
3 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.
53 33 0 0 0 0 0 0 0 0 0 0 0 0
4 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.
94 69 50 0 0 0 0 0 0 0 0 0 0 0
5 1. 1. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.
36 14 89 67 0 0 0 0 0 0 0 0 0 0
6 1. 1. 1. 1. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.
86 61 36 08 0 0 0 0 0 0 0 0 0 0
7 2. 2. 1. 1. 1. 0. 0. 0. 0. 0. 0. 0. 0. 0.
36 08 83 58 31 0 0 0 0 0 0 0 0 0
8 2. 2. 2. 2. 1. 1. 0. 0. 0. 0. 0. 0. 0. 0.
89 61 33 06 81 53 0 0 0 0 0 0 0 0
9 3. 3. 2. 2. 2. 2. 1. 1. 0. 0. 0. 0. 0. 0.
44 14 86 58 31 03 75 50 0 0 0 0 0 0
10 4. 3. 3. 3. 2. 2. 2. 2. 1. 0. 0. 0. 0. 0.
03 69 39 11 83 56 28 00 75 0 0 0 0 0
11 4. 4. 3. 3. 3. 3. 2. 2. 2. 1. 0. 0. 0. 0.
61 25 94 64 36 08 81 53 25 97 0 0 0 0
12 5. 4. 4. 4. 3. 3. 3. 3. 2. 2. 2. 0. 0. 0.
19 83 50 19 89 61 33 06 78 47 22 0 0 0
13 5. 5. 5. 4. 4. 4. 3. 3. 3. 3. 2. 0. 0. 0.
81 42 08 78 44 17 86 58 31 03 72 0 0 0
14 6. 6. 5. 5. 5. 4. 4. 4. 3. 3. 3. 2. 0. 0.
42 03 67 33 03 72 42 14 83 58 28 69 0 0
15 7. 6. 6. 5. 5. 5. 4. 4. 4. 4. 3. 3. 0. 0.
03 64 28 92 61 28 97 69 39 11 83 22 0 0
16 7. 7. 6. 6. 6. 5. 5. 5. 4. 4. 4. 3. 3. 0.
67 25 86 53 19 86 56 25 94 67 36 81 19 0
17 8. 7. 7. 7. 6. 6. 6. 5. 5. 5. 4. 4. 3. 3.
31 86 47 11 78 44 11 81 50 22 92 36 75 44
18 8. 8. 8. 7. 7. 7. 6. 6. 6. 5. 5. 4. 4. 4.
94 50 11 72 36 03 69 39 08 78 47 89 31 00
19 9. 9. 8. 8. 7. 7. 7. 6. 6. 6. 6. 5. 4. 4.
58 14 72 33 97 64 31 97 64 33 03 44 89 58
20 10 9. 9. 8. 8. 8. 7. 7. 7. 6. 6. 6. 5. 5.
.2 78 36 94 58 22 89 56 22 92 61 00 44 14
2
21 10 10 9. 9. 9. 8. 8. 8. 7. 7. 7. 6. 6. 5.
.8 .4 97 58 19 83 50 14 83 50 19 58 00 69
9 2
22 11 11 10 10 9. 9. 9. 8. 8. 8. 7. 7. 6. 6.
.5 .0 .6 .2 83 44 08 75 42 08 78 17 56 25
3 6 1 2
23 12 11 11 10 10 10 9. 9. 9. 8. 8. 7. 7. 6.
.1 .7 .2 .8 .4 .0 69 36 00 67 36 72 14 83
9 2 8 3 4 6
24 12 12 11 11 11 10 10 9. 9. 9. 8. 8. 7. 7.
.8 .3 .9 .4 .0 .6 .3 94 61 28 94 31 69 39
6 6 2 7 8 9 1
25 13 13 12 12 11 11 10 10 10 9. 9. 8. 8. 7.
.5 .0 .5 .1 .6 .3 .9 .5 .2 89 56 92 28 97
3 3 6 1 9 1 4 6 2
26 14 13 13 12 12 11 11 11 10 10 10 9. 8. 8.
.1 .6 .2 .7 .3 .9 .5 .1 .8 .4 .1 50 86 56
9 9 2 5 3 4 6 9 3 7 4
27 14 14 13 13 12 12 12 11 11 11 10 10 9. 9.
.8 .3 .8 .4 .9 .5 .1 .8 .4 .0 .7 .0 44 14
9 6 6 2 7 8 9 1 4 8 5 8
28 15 15 14 14 13 13 12 12 12 11 11 10 10 9.
.5 .0 .5 .0 .6 .2 .8 .4 .0 .6 .3 .6 .0 72
6 3 3 6 4 2 1 2 6 9 6 9 3
29 16 15 15 14 14 13 13 13 12 12 11 11 10 10
.2 .6 .1 .7 .2 .8 .4 .0 .6 .3 .9 .3 .6 .3
5 9 9 2 8 6 4 6 9 3 7 1 4 1
30 16 16 15 15 14 14 14 13 13 12 12 11 11 10
.9 .3 .8 .3 .9 .5 .0 .6 .3 .9 .5 .8 .2 .9
2 6 6 6 2 0 8 9 1 4 8 9 2 2
31 17 17 16 16 15 15 14 14 13 13 13 12 11 11
.6 .0 .5 .0 .5 .1 .7 .3 .9 .5 .1 .5 .8 .5
1 6 3 3 8 4 2 3 4 6 9 0 3 0
32 18 17 17 16 16 15 15 14 14 14 13 13 12 12
.3 .7 .1 .6 .2 .7 .3 .9 .5 .1 .8 .1 .4 .1
1 2 9 9 2 8 6 4 6 9 3 1 4 1
33 18 18 17 17 16 16 16 15 15 14 14 13 13 12
.9 .4 .8 .3 .8 .4 .0 .5 .1 .8 .4 .7 .0 .6
7 2 6 6 9 4 0 8 9 1 4 2 6 9
34 19 19 18 18 17 17 16 16 15 15 15 14 13 13
.6 .0 .5 .0 .5 .0 .6 .2 .8 .4 .0 .3 .6 .3
7 8 3 3 6 8 7 5 3 4 8 6 7 1
35 20 19 19 18 18 17 17 16 16 16 15 14 14 13
.3 .7 .2 .6 .2 .7 .3 .8 .4 .0 .6 .9 .2 .9
6 8 2 9 2 5 1 9 7 8 9 7 8 2
36 21 20 19 19 18 18 17 17 17 16 16 15 14 14
.0 .4 .8 .3 .8 .4 .9 .5 .1 .7 .3 .6 .8 .5
6 7 9 6 9 2 7 3 1 2 3 1 9 3
37 21 21 20 20 19 19 18 18 17 17 16 16 15 15
.7 .1 .5 .0 .5 .0 .6 .1 .7 .3 .9 .2 .5 .1
5 4 8 6 6 8 1 9 8 6 7 2 0 4
38 22 21 21 20 20 19 19 18 18 18 17 16 16 15
.4 .8 .2 .7 .2 .7 .2 .8 .4 .0 .6 .8 .1 .7
4 3 5 2 2 2 8 3 2 0 1 6 4 8
39 23 22 21 21 20 20 19 19 19 18 18 17 16 16
.1 .5 .9 .3 .8 .3 .9 .5 .0 .6 .2 .5 .7 .3
7 3 4 9 9 9 4 0 6 4 5 0 5 9
40 23 23 22 22 21 21 20 20 19 19 18 18 17 17
.8 .2 .6 .0 .5 .0 .5 .1 .7 .3 .8 .1 .3 .0
6 2 4 8 6 6 8 4 2 1 9 1 9 0
41 24 23 23 22 22 21 21 20 20 19 19 18 18 17
.5 .9 .3 .7 .2 .7 .2 .8 .3 .9 .5 .7 .0 .6
6 2 3 5 2 5 5 1 6 4 3 5 0 4
42 25 24 24 23 22 22 21 21 21 20 20 19 18 18
.2 .6 .0 .4 .9 .4 .9 .4 .0 .5 .1 .3 .6 .2
8 1 0 4 2 2 2 7 3 8 9 9 4 9
43 25 25 24 24 23 23 22 22 21 21 20 20 19 18
.9 .3 .6 .1 .5 .0 .5 .1 .6 .2 .8 .0 .2 .8
7 1 9 4 8 8 8 4 7 5 3 3 8 9
44 26 26 25 24 24 23 23 22 22 21 21 20 19 19
.6 .0 .3 .8 .2 .7 .2 .7 .3 .9 .4 .6 .8 .5
7 3 9 1 8 5 5 8 3 2 7 7 9 3
45 27 26 26 25 24 24 23 23 23 22 22 21 20 20
.3 .7 .0 .5 .9 .4 .9 .4 .0 .5 .1 .3 .5 .1
9 2 8 0 4 4 4 4 0 6 4 3 3 7
46 28 27 26 26 25 25 24 24 23 23 22 21 21 20
.0 .4 .7 .1 .6 .1 .6 .1 .6 .2 .7 .9 .1 .8
8 2 8 9 4 1 1 4 7 2 8 7 7 1
47 28 28 27 26 26 25 25 24 24 23 23 22 21 21
.8 .1 .4 .8 .3 .8 .2 .8 .3 .8 .4 .6 .8 .4
1 4 7 9 3 1 8 1 3 9 4 1 1 4
48 29 28 28 27 27 26 25 25 25 24 24 23 22 22
.5 .8 .1 .5 .0 .4 .9 .4 .0 .5 .1 .2 .4 .0
3 3 9 8 0 7 7 7 0 6 1 8 7 8
49 30 29 28 28 27 27 26 26 25 25 24 23 23 22
.2 .5 .8 .2 .6 .1 .6 .1 .6 .1 .7 .9 .1 .7
2 3 9 8 9 7 4 4 7 9 5 2 1 2
50 30 30 29 28 28 27 27 26 26 25 25 24 23 23
.9 .2 .5 .9 .3 .8 .3 .8 .3 .8 .4 .5 .7 .3
4 5 8 7 9 3 1 1 3 6 2 8 5 6
3.2 Computer implementation
When computer facilities are available, it is possible to
automate the use of Tables 3/E.521 to 6/E.521. For that purpose,
numerical algorithms have been developed and are described in [5].
4 Example
4.1 Level of day_to_day traffic variations
If the traffics offered to a final group over the 30 busiest
days are given (M1 to M30) and if the mean load and variance are
calculated to be 10 and 20 respectively, then applying Figure
1/E.521, a high level of day_to_day traffic variations should be
used.
4.2 Future traffic offered to the final group and peakedness
factor
If the forecast of future traffics indicates that three
parcels of traffic will be offered to the final group:
_ the overflow from 6 circuits offered 7.8 Erlangs,
_ the overflow from 12 circuits offered 10 Erlangs,
_ 7 Erlangs offered directly,
then Table 7/E.521 can be developed.
Table 7/E.521
Numbe Traff Numbe Adjus- Averag
r of ic r of Single- Last Peake bizi temen e
parce offer high- hour trunk dness t overfl
ls of ed to usage overflow traff facto facto ow
traff high- circu bi ic r zi r ri
ic i usage it ni
group
Ai
1 7.8 6 2.95 0.69 1.73 5.1 1.0 2.95
2 10.0 12 1.20 0.44 2.19 2.6 1.2 1.44
3 7.0 0 7.0 _ 1.0 7.0 1.0 7.00
Note that the values of ri are derived from Table 2/E.521 for
medium level of day_to_day traffic variations; if the 30 busiest
day traffics for each of the high_usage groups were available, a
more appropriate level could be used for each group.
Now all the information required is available: using the
capacity Table 6/E.521 for high level of day_to_day traffic
variations, the average traffic offered to the final group M =
11.39 and a peakedness factor z = 1.3 (from interpolating between z
= 1.2 and z = 1.4), it is calculated that 23 circuits are required.
Note that if the measurements used in 4.1 above were not
available, then to determine the level of day_to_day traffic
variations it would have been necessary to use the default
procedure of 1 above.
Overflow traffic offered to the final group = 4.15 Erlangs.
Total traffic offered to the final group = 11.15 Erlangs.
The ratio 4.15/11.15 = 0.37 is higher than 0.25 and hence a
medium level of day_to_day traffic variations would have been used.
References
[1] Tabellen für die Planung von Fernsprecheinrichtungen, Siemens
u. Halske, München, 1961.
[2] WILKINSON (R. I.): Theories for toll traffic engineering in
the USA (Figures 12 and 13), Bell System Technical Journal,
Vol. 35, March 1956.
[3] WILKINSON (R. I.): Simplified engineering of single stage
alternate routing systems, Fourth International Teletraffic
Congress, London, 1964.
[4] WILKINSON (R. I.): Non_random traffic curves and tables, Bell
Telephone Laboratories, 1970.
[5] HILL (D. W.) and NEAL (S. R.): The traffic capacity of a
probability_engineered trunk group, Bell System Technical
Journal, September 1976.
_______________________________
1) Tables giving:
_ the exact mean of the overflow traffic, and
_ the difference between variance and mean of the overflow
have been computed and are set out in [1].
2) Curves giving the exact mean and variance of overflow traffic
are given in [2]. See also a more detailed description of the
method in [3] and [4].