1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 % TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU4%,%0(/.%G0G0.%47/2+G0G0!.$G0G0)3$.15!,)49G0G0/ M on the horizontal axis, and Vdon 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 betwe
2、en 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 Vduse the f
3、ollowing guidelines:a) If no more than 25 per cent of the traffic offered to the final group is overflow from other groups, assumethe level of day-to-day variation is Low.b) Otherwise, assume a Medium level of variation.2 Fascicle II.3 - Rec. E.5212 Determination of peakedness factor zPeakedness fac
4、tors depend principally upon the number of high-usage circuits over which random traffic hasaccess. When the number of such high-usage circuits does not exceed 30, the actual peakedness of the trafficoverflowing from a high-usage group will be only slightly below the maximum peakedness values1),2).
5、The maximumpeakedness values are given in Table 1/E.521._1) Tables giving:- the exact mean of the overflow traffic, and- the difference between variance and mean of the overflowhave been computed and are set out in 1.2)Curves giving the exact mean and variance of overflow traffic are given in 2. See
6、 also a more detailed description of the methodin 3 and 4.Fascicle II.3 - Rec. E.521 3TABLE 1/E.521Maximum peakedness factor ziNumber ofhigh-usage circuits(ni)Peakedness factor(zi)Number ofhigh-usage circuits(ni)Peakedness factor(zi)1234567891011121314151.171.311.431.541.641.731.821.901.982.052.122.
7、192.262.322.381617181920212223242526272829302.442.492.552.612.662.712.762.812.862.912.963.003.053.093.14For more than 30 circuits, the peakedness of the traffic overflowing from a high-usage group i of nicircuits isgiven byzAnAiiiiii= + 11whereAiis the mean (random) traffic offered to the nicircuits
8、 andiis the traffic overflowing. The overflow traffic iis found by employing the standard Erlang loss formulaE1, ni(Ai):iiniAE Ai=1,().The weighted mean peakedness factor z, is then calculated from:zihiiiihZ=11for the h parcels of traffic being offered to the final group.Note that for the traffic di
9、rectly 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 required3.1 For planning future network requirements, the traffic overflowing to a final group should be determinedtheoretically from forecasts
10、of traffics offered to the high-usage groups.4 Fascicle II.3 - Rec. E.521The mean traffic overflowing to the final group from a high-usage group is determined in two steps:i) the “single-hour“ overflow traffic ioverflowing from nicircuits is given as above byiiiniAE Ai=,(),when Aiis the forecast of
11、traffic offered to the ithhigh-usage group;ii) the average overflow traffic ioverflowing from the nicircuits is then determined by adjusting the single-hour traffic ifor the effect of day-to-day traffic variations.i= riiThe adjustment factor riis given in Table 2/E.521; it is a function of: the offe
12、red traffic Ai, the traffic ()AE Aiin i ii,1carried 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 oftraffic offered to the high-usage group
13、 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 iover the h parcels of traffic:Mihi=1It can be assumed that the level of day-to-day traffic variations on the final group remains constant over theforecast time peri
14、od.Using the level of day-to-day traffic variation as determined in 1 above on the final group and the peakednessfactor 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
15、the final group is valid only if the overflowtraffic 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 inTable 3.1/E.521 there is no allowance for day-to-
16、day variations. The new table takes into account a systematic bias inthe measurement procedure that is based on a finite period of time (1 hour), instead of an infinite period as wasassumed 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 avera
17、ge blocking from theformula: = Bmf m dm()() , whereB (m) is the single-hour expected blocking andf (m) is the density distribution of day-to-day traffic (m), assuming a Pearson Type III distribution:Fascicle II.3 - Rec. E.521 5()()()()()fmMVmeMVMVMVMVdddmd=/2221M and Vdare the mean and day-to-day va
18、riance of the traffic as calculated 5 in 1 above.TABLE 2/E.521Overflow adjustment for high-usage trunk groupsFactor riLast trunk trafficOfferedtrafficAiLow daily variation Medium daily variation High daily variation0.25 0.3 0.4 0.5 0.6 0.25 0.3 0.4 0.5 0.6 0.25 0.3 0.4 0.5 0.635710152025301.01.01.01
19、11.21.21.31.31.01.01.01.11.11.21.21.31.01.01.01.11.11.11.21.21.01.01.01.01.11.11.11.11.01.01.01.01.01.01.11.11.01.11.21.31.51.61.81.81.01.11.21.21.41.51.61.71.01.11.11.21.21.31.41.41.01.01.11.11.21.21.31.31.01.01.01.11.11.11.11.21.01.21.41.51.82.02.32.41.01.21.31.41.61.82.02.11.01.11.21.31.41.51.71
20、71.01.11.11.21.31.31.41.51.01.01.11.11.11.21.21.36 Fascicle II.3 - Rec. E.521TABLE 3/E.521Single-hour capacity, in Erlangs, as a function of the number of trunksand of the peakedness factorParameters: Blockage 0.01; No allowance for day-to-day variation; Weighted mean peakedness factor.Numberof tru
21、nksrequired1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.4 3.8 4.012345678910111213141516171819202122232425262728293031323334353637383940414243444546474849500.060.220.530.941.421.972.563.193.834.535.225.946.677.428.178.949.7210.5011.3112.0812.8913.7214.5315.3616.1917.0317.8618.6919.5620.3921.2522.11
22、22.9723.8324.6925.5826.4427.3128.1929.0829.9430.8331.7232.6133.5034.3935.2836.1737.0637.970.00.00.330.691.141.642.192.813.424.084.755.446.146.867.588.339.089.8310.6111.3912.1913.0013.7814.5815.3916.2217.0317.8618.6919.5320.3621.1922.0622.8923.7524.5825.4426.3127.1728.0328.8929.7530.6431.5032.3933.25
23、34.1435.0035.8936.780.00.00.00.500.891.361.862.443.033.674.314.975.646.367.067.788.509.2510.0010.7811.5312.3113.0813.8914.6715.4716.2817.0817.8918.7219.5320.3621.1922.0022.8323.6924.5325.3626.2227.0627.9228.7829.6130.4731.3332.1933.0833.9434.8135.670.00.00.00.00.671.081.582.112.673.283.894.565.195.8
24、96.587.288.008.729.4410.1910.9411.6912.4713.2214.0014.8115.5816.3617.1717.9718.7819.5820.3921.2222.0322.8623.6924.5325.3626.1927.0327.8628.7229.5630.4231.2532.1132.9733.8134.670.00.00.00.00.00.01.311.812.362.923.534.144.815.446.116.817.508.228.929.6710.3911.1411.8912.6413.3914.1714.9415.7216.5017.28
25、18.0818.8919.6720.4721.2822.1122.9223.7224.5625.3926.1927.0327.8628.6929.5330.3931.2232.0632.9233.750.00.00.00.00.00.00.01.532.032.583.173.784.395.035.696.367.067.758.449.149.8610.6111.3612.0812.8313.5814.3315.1115.8616.6417.4218.2219.0019.8120.5821.3922.1923.0023.8124.6125.4426.2527.0827.8928.7229.
26、5630.3931.2232.0632.890.00.00.00.00.00.00.00.01.752.282.833.424.034.675.315.946.617.317.978.679.3910.0810.8111.5612.2813.0313.7814.5315.2816.0616.8117.5818.3619.1419.9220.7221.5022.3123.1123.8924.6925.5326.3327.1427.9428.7829.5830.4231.2532.080.00.00.00.00.00.00.00.01.502.002.533.083.674.284.925.566
27、196.867.538.228.929.6110.3311.0311.7812.5013.2213.9714.7215.4716.2217.0017.7518.5319.3120.0820.8621.6422.4423.2224.0324.8125.6126.4227.2228.0328.8629.6730.4731.310.00.00.00.00.00.00.00.00.01.752.252.783.333.944.565.175.816.447.117.818.479.179.8610.5611.2812.0012.7213.4414.1914.9215.6716.4217.1917.9
28、418.6919.4720.2521.0321.8122.5823.3624.1724.9425.7526.5627.3328.1428.9429.7530.580.00.00.00.00.00.00.00.00.00.01.972.473.033.614.194.815.426.066.727.398.068.729.4210.1110.8111.5312.2212.9413.6714.4215.1415.8916.6417.3918.1418.8919.6720.4421.1921.9722.7523.5324.3125.1125.8926.6927.4728.2829.0829.890.
29、0000.00.00.00.00.00.00.00.00.02.222.723.283.864.445.065.696.336.977.648.318.979.6710.3611.0611.7512.4713.1913.9214.6415.3616.1116.8617.6118.3619.1119.8620.6421.3922.1722.9423.6924.5025.2826.0626.8327.6428.4229.220.00.00.00.00.00.00.00.00.00.00.00.00.02.693.223.814.394.975.586.226.867.508.178.839.501
30、0.1910.8611.5612.2812.9713.6914.3915.1115.8616.5817.3118.0618.8119.5320.2821.0621.8122.5623.3324.0824.8625.6426.4227.1927.970.00.00.00.00.00.00.00.00.00.00.00.00.00.00.03.193.754.314.895.506.116.757.398.038.699.3610.0310.6911.3912.0812.7813.4714.1714.8915.6116.3117.0617.7818.5019.2519.9720.7221.4722
31、2222.9723.7224.4725.2526.0026.780.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.03.444.004.585.175.786.397.007.648.318.949.6110.2810.9411.6412.3313.0313.7214.4215.1415.8316.5617.2818.0018.7219.4720.1920.9421.6922.4223.1723.9224.6925.4426.19Fascicle II.3 - Rec. E.521 7TABLE 4/E.521Single-hour capacit
32、y, in Erlangs, as a function of the number of trunksand of the peakedness factorParameters : Blockage 0.01; Low day-to-day variation allowance; Weighted mean peakedness factor.Numberof trunksrequired1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.4 3.8 4.01234567891011121314151617181920212223242526272
33、8293031323334353637383940414243444546474849500.060.220.530.941.391.892.443.033.644.254.925.586.256.947.648.339.069.8110.5311.2812.0312.7813.5314.3115.0815.8616.6417.4218.2219.0019.8120.6121.3922.2223.0323.8324.6425.4726.2827.1127.9228.7529.5830.4231.2532.0832.9233.7534.5835.440.00.00.330.691.141.642
34、142.693.283.894.535.175.816.507.177.868.569.2810.0010.7211.4412.1912.9413.6914.4415.2215.9716.7517.5318.3119.0819.8920.6721.4722.2523.0623.8624.6725.4726.2827.0827.9228.7229.5630.3631.1932.0332.8333.6734.500.00.00.00.500.891.361.862.422.973.564.174.785.426.086.757.428.118.819.5010.2210.9411.6712.39
35、13.1413.8614.6115.3616.1416.8917.6718.4419.1919.9720.7521.5622.3323.1423.9224.7225.5326.3127.1127.9228.7529.5630.3631.1732.0032.8133.640.00.00.00.00.671.081.582.112.673.223.834.445.065.696.337.007.678.369.069.7510.4411.1711.8912.6113.3314.0814.8115.5616.3117.0617.8318.5819.3620.1120.8921.6722.4423.2
36、524.0324.8125.6126.3927.1928.0028.8129.6130.4231.2232.0332.830.00.00.00.00.00.01.311.812.362.923.504.084.695.335.976.617.287.948.619.3110.0010.6911.4212.1112.8313.5614.2815.0315.7816.5017.2518.0018.7819.5320.2821.0621.8322.6123.3924.1724.9425.7226.5027.3128.0828.8929.6930.4731.2832.080.00.00.00.00.0
37、0.00.01.532.032.583.173.784.364.975.616.256.897.568.228.899.5610.2510.9411.6712.3613.0813.8114.5315.2516.0016.7217.4718.2218.9719.7220.4721.2522.0022.7823.5324.3125.0825.8626.6427.4428.2229.0029.8130.5831.390.00.00.00.00.00.00.00.01.752.282.833.424.034.645.255.896.537.177.838.509.179.8310.5311.2211.
38、9212.6113.3314.0614.7815.5016.2216.9417.6918.4219.1719.9220.6721.4422.1922.9423.7224.4725.2526.0326.8127.5828.3629.1429.9430.720.00.00.00.00.00.00.00.01.502.002.533.083.674.284.925.536.176.817.448.118.789.4410.1110.8111.5012.1912.8913.5814.3115.0315.7216.4717.1917.9218.6719.3920.1420.8921.6422.3923.
39、1423.9224.6725.4426.2226.9727.7528.5329.3130.080.00.00.00.00.00.00.00.00.01.752.252.783.333.944.565.175.816.447.087.728.399.069.7210.3911.0811.7512.4413.1413.8614.5615.2816.0016.7217.4418.1718.8919.6420.3621.1121.8622.6123.3624.1124.8925.6426.4227.1727.9428.7229.500.00.00.00.00.00.00.00.00.00.01.972
40、473.033.614.194.815.426.066.727.368.038.679.3310.0010.6711.3612.0312.7213.4214.1114.8315.5316.2516.9717.6918.4219.1419.8920.6121.3622.1122.8323.5824.3325.1125.8626.6127.3928.1428.920.00.00.00.00.00.00.00.00.00.00.02.222.723.283.864.445.065.696.336.977.648.318.949.6110.2810.9411.6412.3113.0013.6914.
41、3915.1115.8116.5317.2217.9418.6719.4220.1420.8621.6122.3323.0823.8324.5825.3326.0826.8327.5828.360.00.00.00.00.00.00.00.00.00.00.00.00.02.693.223.814.394.975.586.226.867.568.198.869.5010.1710.8311.5012.1912.8613.5614.2514.9415.6716.3617.0817.7818.5019.2219.9420.6721.3922.1122.8623.5824.3325.0625.812
42、6.5627.310.00.00.00.00.00.00.00.00.00.00.00.00.00.00.03.193.754.314.895.506.116.757.398.038.679.3310.0010.6711.3612.0612.7513.4414.1414.8315.5616.2516.9417.6418.3319.0619.7820.4721.1921.9222.6423.3624.1124.8325.5626.310.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.03.444.004.585.175.786.397.007.648.
43、318.949.6110.2810.9411.6412.3313.0313.7214.4215.1115.8116.5017.1917.8918.6119.3120.0320.7521.4422.1722.8923.6424.3625.0825.838 Fascicle II.3 - Rec. E.521TABLE 5/E.521Single-hour capacity, in Erlangs, as a function of the number of trunksand of the peakedness factorParameters : Blockage 0.01; Medium
44、day-to-day variation allowance; Weighted mean peakedness factor.Numberof trunksrequired1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.4 3.8 4.012345678910111213141516171819202122232425262728293031323334353637383940414243444546474849500.060.220.530.941.391.862.392.943.534.114.725.366.006.647.317.978.6
45、49.3310.0310.6911.4212.1112.8313.5314.2514.9715.6916.4417.1717.9218.6419.3920.1420.8921.6422.3923.1423.8924.6425.4226.1726.9427.7228.4729.2530.0330.8131.5832.3633.140.00.00.330.691.141.612.112.643.193.784.394.975.616.226.897.538.198.869.5310.1910.8911.5812.2813.0013.6914.4215.1115.8316.5617.2818.031
46、8.7519.4720.2220.9721.6922.4423.1923.9424.6925.4426.1926.9727.7228.4729.2530.0030.7831.5632.310.00.00.00.500.891.361.832.362.893.474.034.645.255.866.477.117.788.429.089.7510.4211.1111.7812.4713.1713.8614.5815.2816.0016.7217.4218.1418.8619.6120.3321.0621.8122.5323.2824.0324.7825.5026.2527.0027.7828.5
47、329.2830.0330.8131.560.00.00.00.00.671.081.582.082.613.173.724.314.895.506.116.757.368.038.679.339.9710.6411.3312.0012.6913.3914.0814.7815.4716.1716.8917.5818.3119.0319.7520.4721.1921.9422.6723.3924.1424.8625.6126.3627.1127.8628.6129.3630.1130.860.00.00.00.00.00.01.311.812.332.863.424.004.565.175.78
48、6.397.007.648.288.929.5610.2210.8911.5612.2512.9213.6114.2814.9715.6716.3917.0817.7818.5019.2219.9220.6421.3622.0822.8123.5624.2825.0025.7526.4727.2227.9728.7229.4430.190.00.00.00.00.00.00.01.532.032.583.143.694.254.835.426.036.647.287.898.539.179.8310.4711.1411.8112.4713.1413.8314.5315.1915.8916.58
49、17.2818.0018.6919.4220.1120.8321.5622.2522.9723.7224.4425.1725.8926.6427.3628.1128.8329.580.00.00.00.00.00.00.00.01.752.282.833.393.944.535.115.696.316.927.538.178.819.4410.0810.7211.3912.0612.7213.3914.0814.7515.4416.1116.8117.5018.1918.9219.6120.3121.0321.7522.4423.1723.8924.6125.3326.0626.7827.5328.2529.000.00.00.00.00.00.00.00.01.502.002.533.083.674.224.785.395.976.587.197.818.449.069.6910.3611.0011.6412.3112.9713.6414.3115.0015.6716.3617.0617.7518.4419.1419.8320.5321.2521.9422.6723.3624.0824.8
