1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 % TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU4%,%0(/.%G0G0.%47/2+G0G0!.$G0G0)3$.15!,)49G0G0/ii) the marginal utilization factor M applicable to the overflow routes is regarded as constant within a range ofcircuit group sizes;Size of group(number of circ
2、uits)Value of MFor less than 10 . . . . . . . . . . . . . . . . . . .For 10 or more . . . . . . . . . . . . . . . . . . . .0.60.8iii) each high-usage group will be dimensioned against the cheapest alternative route to which trafficoverflows. (That is, the effect of parallel alternative routes is ign
3、ored.)Where greater precision is required in either network or individual route dimensioning, more sophisticatedmethods may be employed (see 5 and 7.2.4 Determination of cost ratioIn continental and intercontinental working, the number of circuits to be provided in high-usage circuit groupsdepends u
4、pon the ratio of the annual charges estimated by the Administrations involved. The annual charge ratio (seeTable 1/E.522) is defined as:R = annual charge of one additional circuit on the alternative routeannual charge of one additional circuit on the high - usage routeThe “annual charge of one addit
5、ional circuit on the alternative route” is calculated by summing: the annual charge per circuit of each link comprising the alternative route, and the annual charge of switching one circuit at each intermediate switching centre.When a third Administration is involved, it may be necessary to calculat
6、e the annual charge for switching at theintermediate centre from the transit switching charge per holding minute3). This may be done as follows:Annual charges for switching = M 60 F 26 12 transit switching charge per holding minute.In the calculation of the conversion factor F from busy hour to day,
7、 its dependence on the traffic offered to thehigh usage route, the overflow probability and the time difference should be taken into account. As a guideline,Table 1/E.522, which is calculated using the standard traffic profiles of Table 1/E.523, may be used._3)It may be necessary to calculate transi
8、t switching charge per holding minute from charge per conversation minute (efficiency factor is described in Recommendation E.506).Fascicle II.3 - Rec. E.522 3TABLE 1/E.522OfferedtrafficOverflowprobabilityTime difference(erlangs) (%)0123456789101121 2.6 3.2 3.7 3.8 2.7 2.3 2.3 1.7 3.2 2.4 2.2 2.0 2.
9、710 3.7 4.5 4.8 4.7 3.5 3.1 3.0 2.5 4.1 3.2 2.9 2.8 3.620 4.5 5.2 5.4 5.3 4.0 3.7 3.5 3.1 4.7 3.8 3.4 3.4 4.25 30 5.1 5.8 6.0 5.8 4.6 4.2 4.0 3.7 5.1 4.3 3.9 4.0 4.840 5.7 6.4 6.5 6.3 5.1 4.7 4.5 4.2 5.6 4.8 4.4 4.6 5.350 6.3 6.9 7.0 6.8 5.6 5.2 5.0 4.7 6.0 5.3 5.0 5.1 5.81 2.1 2.6 3.3 3.5 2.5 2.1 2
10、.1 1.4 2.8 2.0 2.0 1.8 2.410 3.2 4.0 4.4 4.3 3.1 2.7 2.6 2.1 3.8 2.8 2.6 2.4 3.220 4.0 4.8 5.1 4.9 3.6 3.3 3.1 2.7 4.3 3.4 3.0 3.0 3.810 30 4.7 5.4 5.6 5.4 4.2 3.8 3.6 3.3 4.8 3.9 3.4 3.6 4.440 5.3 6.0 6.1 5.9 4.7 4.4 4.2 3.8 5.3 4.4 4.0 4.2 4.950 5.9 6.6 6.7 6.4 5.3 4.9 4.7 4.4 5.7 5.0 4.6 4.8 5.51
11、 1.6 2.0 2.8 3.1 2.2 1.8 2.0 1.2 2.4 1.7 1.8 1.6 2.110 2.7 3.3 3.9 3.9 2.7 2.4 2.3 1.7 3.3 2.4 2.3 2.0 2.720 3.5 4.2 4.6 4.4 3.2 2.8 2.7 2.2 3.9 3.0 2.6 2.5 3.325 30 4.2 5.0 5.2 5.0 3.7 3.4 3.2 2.8 4.4 3.5 3.0 3.1 3.940 4.8 5.6 5.8 5.5 4.3 3.9 3.8 3.4 4.9 4.0 3.5 3.7 4.550 5.5 6.2 6.3 6.1 4.9 4.5 4.
12、3 4.0 5.4 4.6 4.1 4.4 5.11 1.3 1.7 2.4 2.9 2.1 1.6 2.0 1.1 2.1 1.5 1.6 1.4 2.010 2.3 2.8 3.5 3.6 2.5 2.2 2.1 1.4 3.1 2.2 2.2 1.8 2.420 3.1 3.9 4.3 4.2 3.0 2.6 2.4 1.9 3.7 2.7 2.5 2.2 3.050 30 3.9 4.7 5.0 4.8 3.4 3.1 2.9 2.5 4.2 3.3 2.8 2.8 3.640 4.6 5.4 5.6 5.3 4.0 3.7 3.5 3.2 4.7 3.8 3.2 3.5 4.350
13、5.3 6.0 6.1 5.9 4.7 4.3 4.2 3.8 5.2 4.3 3.8 4.2 4.9Note Linear interpolation may be used to obtain intermediate results.The value determined for R should then be employed to select in Table 2/E.522 the precise (or next higher)value of annual charges ratio for use in traffic tables. The value of annu
14、al charges ratios may be grouped in thefollowing general sets:a) Within a single continent or other smaller closely connected land mass involving distances up to 1000miles, high traffic and frequently one-way operation:4 Fascicle II.3 - Rec. E.522Annual charges ratio: R = 1.5; 2.0 ; 3.0; 4.0; 5.0; 6
15、.0 and 7.04)b) Intercontinental working involving long distances, small traffic and usually two-way operation:Annual charges ratio: R = 1.1; 1.3 ; 1.5; 2.0; 3.0; 4.0 and 5.04).2.5 Use of methodHigh-usage circuit groups carrying random traffic can be dimensioned from Table 2/E.522.Step 1 Estimate the
16、 annual charges ratio R as described under 2.4 above. (There is little difference betweenadjacent ratios.) If this ratio is difficult to estimate, the values underlined in a) and b) of 2.4 above, should be used.Step 2 Consult Table 2/E.522 to determine the number of high-usage circuits N.Note When t
17、wo values of N are given the right-hand figure applies to alternative routes of more than10 circuits, the left-hand figure applies to smaller groups. The left-hand figure is omitted when it is no longer possiblefor the alternative route to be small.3 24-hour traffic profilesThe traffic value used in
18、 the method in 2 should be the value of traffic offered to the high-usage route duringthe busy hour of the final route. In the case that some of the busy hours of the circuit groups or links forming analternative route do not coincide with the busy hour of the relation, the ensuing method should be
19、followed to take24-hour traffic profiles into account (see 6, 8 and 9).The method consists of the following three basic steps:i) prepare hourly traffic demands for which dimensioning is to be done;ii) size all circuit groups, high usage and final, for one hourly traffic demand;iii) iterate the proce
20、ss in step ii) for each additional hourly matrix.3.1 Preparation of hourly traffic demandsEach Administration gathers historical traffic data on an hourly basis in accordance withRecommendations E.500 and E.523. Using historical data and information contained in Recommendation E.506,hourly traffic d
21、emand forecasts are made, resulting in a series of hourly demands for each exchange to every otherexchange.3.2 Sizing circuit groups for one-hourly traffic demandUsing the methods in 2 and Recommendation E.521, trunk group sizes are prepared for the first hourly trafficdemand disregarding other hour
22、ly traffic demands._4)These values are tentative. Ranges and representative values of annual charges ratio require further study.Fascicle II.3 - Rec. E.522 5TABLE 2/E.522Number of high-usage circuits for different values of offered traffic, annual charges ratios and sizes of overflow groupsAnnual ch
23、arges ratios1.1 1.3 1.5 2.0 3.0 4.0 5.0 6.0 7.0 Number of circuitsTraffic offeredduring networkMinimum circuit occupancies for high-usage trafficif there isno overflowbusy hour(erlangs)0.545/0.727 0.46/0.615 0.4/0.53 0.3/04 0.2/0.26 0.15/0.2 0.12/0.16 0.0/0.13 0.085/0.114route, forp = 0.01N, number
24、of high usage circuits A/B, whereA is for less than 10 circuits in the overflow group (M = 0.6)B is for 10 or more circuits in the overflow group (M = 0.8)1.5 1/0 1/0 2/1 2/2 3/2 3/3 4/3 4/3 4/4 61.75 1/0 2/1 2/1 3/2 3/3 4/3 4/4 4/4 4/4 62.0 1/0 2/1 2/2 3/2 4/3 4/4 4/4 5/4 5/5 72.25 2/0 2/1 3/2 3/3
25、4/4 5/4 5/4 5/5 5/5 72.5 2/0 3/1 3/2 4/3 5/4 5/5 5/5 6/5 6/5 72.75 2/1 3/2 3/2 4/3 5/4 5/5 6/5 6/6 6/6 83.0 3/1 3/2 4/3 4/4 5/5 6/5 6/6 6/6 7/6 83.5 3/1 4/2 4/3 5/4 6/5 7/6 7/6 7/7 7/7 94.0 4/2 4/3 5/4 6/5 7/6 7/7 8/7 8/7 8/8 104.5 4/2 5/3 6/4 6/6 7/7 8/7 8/8 9/8 9/8 105.0 5/3 6/4 6/5 7/6 8/7 9/8 9/
26、9 9/9 10/9 115.5 5/3 6/5 7/5 8/7 9/8 9/9 10/9 10/10 10/10 126.0 6/3 7/5 7/6 8/7 9/9 10/9 11/10 11/10 11/11 137.0 7/4 8/6 8/7 10/8 11/10 11/11 12/11 12/12 13/12 148.0 8/5 9/7 10/8 11/10 12/11 13/12 13/13 14/13 14/13 159.0 /6 /8 /9 /11 /12 /13 /14 /14 /15 1710.0 /7 /9 /10 /12 /14 /15 /15 /16 /16 1812.
27、0 /9 /11 /12 /14 /16 /17 /18 /18 /19 2015.0 /12 /14 /16 /18 /20 /21 /21 /22 /22 2420.0 /16 /19 /21 /23 /25 /27 /28 /28 /29 3025.0 /21 /24 /26 /29 /31 /33 /33 /34 /35 3630.0 /26 /29 /31 /34 /37 /38 /39 /40 /41 4240.0 /36 /39 /42 /45 /48 /50 /51 /52 /52 5350.0 /45 /49 /52 /55 /59 /61 /62 /63 6460.0 /5
28、5 /60 /62 /66 /70 /72 /73 7580.0 /74 /80 /83 /87 /92 /94 /95 96100.0 /94 /100 /103 /108 /113 /116 117120.0 /113 /120 /124 /129 /134 /137 Direct final circuit groups are 138150.0 /143 /150 /154 /160 /166 /169 economical within this area. 170200.0 /192 /200 /205 /212 /219 221250.0 /241 /250 /256 /263
29、/271 273300.0 /290 /300 /306 /315 /323 3246 Fascicle II.3 - Rec. E.5223.3 Iterating for each additional hourly traffic matrixIn sizing the circuit groups for the second hourly traffic demand, the method is provided with the circuit quantitiesresulting from the previous step, and is constrained solel
30、y to increasing circuit group sizes; i.e., if the circuit group sizes forthe first hourly traffic demand were greater than for the second hourly demand, then the circuit group sizes for the firsthourly traffic demand would be retained.All additional hourly traffic demands are processed in the same i
31、terative manner. The resulting circuit group sizesthen satisfy the traffic demands for all hours being considered (see Annex A for a computational example).3.4 Processing sequenceProcessing may start with the first hour of traffic demand, however, experiments have indicated that efficiencies ofthe n
32、etwork can be improved if processing starts with the hour with the smallest total traffic demand. It should be noted thatthis method gives us suboptimal networks, which may be improved by manual refinements.4 Minimum outlay alternate routing networksThe method below allows Administrations to adjust
33、alternate routing networks to take into account existing revenueaccounting divisions.The method consists of the following steps:i) Obtain 24-hour traffic profiles in accordance with Recommendations E.500 and E.523;ii) Compute circuit quantities and costs for a no-overflow network in accordance with
34、Recommendation E.520;iii) Compute monthly overflow minutes (holding time) at varying percentages of busy-hour overflow. This is doneby applying three conversion factors to the busy hour overflow erlangs: Ratio of holding minutes to erlangs: a fixed value of 60. Daily overflow to busy-hour overflow r
35、atio: a value that depends on the 24-hour traffic profile and thedegree of overflow. Monthly overflow to daily overflow ratio (Recommendation E.506): a value that depends on the day-to-daypattern within a month and the degree of overflow.iv) Starting with the network calculated in step ii): reduce t
36、he high usage circuits by one circuit, calculate overflow to final circuit groups, dimension final circuit groups in accordance with Recommendation E.521, calculate circuit costs and transit charges;v) Iterate step iv) until the minimum outlay (circuit costs plus transit charges) for terminal admini
37、strations isreached (see Annex B for computational example).5 Service considerationsOn intercontinental circuits, where both-way operation is employed, a minimum of two circuits may be economical.Service considerations may also favour an increase in the number of direct circuits provided, particular
38、ly where the annualcharges ratio approaches unity.Although the dimensioning of high-usage groups is normally determined by traffic flows and annual charges ratios,it is recognized that such groups form part of a network having service requirements relative to the subscriber. The ability tohandle the
39、 offered traffic with acceptable traffic efficiency should be tempered by the overall network considerations onquality of service.The quality of service feature, which is of primary importance in a system of high-usage and final circuit groups, isthe advantage derived from direct circuits versus mul
40、ti-link connections. A liberal use of direct high-usage circuit groups,taking into account the economic factors, favours a high quality of service to the subscriber. It is recommended that newhigh-usage groups should be provided whenever the traffic flow and cost ratios are not conclusive. This prac
41、tice may resultin direct high-usage groups of two circuits or more.Fascicle II.3 - Rec. E.522 7The introduction of high-usage groups improves the overall grade of service and provides better opportunities ofhandling traffic during surges and breakdown conditions. When high-usage links bypass the mai
42、n final routes theintroduction of high-usage routes can assist in avoiding expenses which might otherwise be incurred in keeping below themaximum number of long-distance links in series. In the future, more measurements of traffic flows may be necessary forinternational accounting purposes and high-
43、usage circuits should make this easier.ANNEX A(to Recommendation E.522)Example of network dimensioning taking into account24-hour traffic profilesA.1 Assumptions (see also Figure A-1/E.522)Calculations are performed under the following conditions:1) Time difference:A is 9 hours west of BC is 5 hours
44、 west of AB is 10 hours west of C2) Traffic profiles:24-hour traffic profiles as per Table l/E.523 are used.3) Busy hour traffic:A-B 50 erlangsA-C 100 erlangsC-B 70 erlangs4) Cost ratio:R = 1.3A.2 Numerical results24 hourly traffic demands are processed. The order of processing are from the hour wit
45、h the smallest total trafficdemand to the hour with the largest total traffic demand. Computational results are given in Table A-1/E.522.8 Fascicle II.3 - Rec. E.522TABLE A-1/E.522Numerical resultsHour Hourly traffic demandNumber of circuitsobtained by single hourdimensioning(disregarding lowerbound
46、s imposed by theprevious iterative stage)Number of circuitsobtained consideringlower bounds imposed bythe previous iterativestageNumber of circuitsrequired to meet multiplehourly traffic demandsA-B A-C C-B A-B A-C C-B A-B A-C C-B A-B A-C C-B6 17.50 5.00 3.50 17 19 17 17 19 17 17 19 1775489320.002.50
47、2.5037.5040.002.505.005.005.005.005.005.003.5028.0035.003.503.5045.50191137391201414232414184149222361191919191919201111384111183947374059191919191919202020384141183947474759181019202222.5050.002.502.5012.502.5050.005.0060.0060.0030.005.003.503.503.503.5024.5063.0014911121662677774514122512123980199
48、19191219646175754511959993978191919191919646475757575595959595978171231121122.502.5020.0047.5012.5042.5070.005.0020.0025.0055.0030.003.5070.0042.0017.5024.5021.0011194712428714364673501287603839411919193123851136857385985607739761919191919198585858585857885858585851601315142.5020.0030.0017.5027.5090
49、.0020.0065.00100.0095.003.5066.5035.0028.0038.50119291727109368612111712875444571919519191073610712012498776436419191919191071071071201248587878787This example relates to an intercontinental network where busy hours of the three traffic relations are widelydifferent among each other. The busy hour of the relation A-C, i.e. hour 15, is a low traffic period for the relations A-B andC-B. The busy hour
