џWPCL ћџ2BJ|xа АH аа АА X агJга ХА6p&А6p&Х аебI а Hx аааУ Уб cмˆ4 PŽТ б styleref head_footRecommendation G.763Ф ФPAGE331У Уб cмˆ4 PŽТ ббееЌ† а HH аааб cмˆ4 PŽТ бPAGE330б cмˆ4 PŽТ бУ Уstyleref head_footRecommendation G.763 Ќеа HH ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаа X Ш аб cмˆ4 PŽТ бRecommendation G.763 аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬа‚Ср8OСб cмˆ4 PŽТ бANNEX B Ср8FСб cмˆ4 PŽТ б(to Recommendation G.763) B.1Тh  ТУУAn example of a DLC double averaging techniqueФФЦЦ а H аС СThe average number of encoding bits per sample is obtained using a double average process. а H аТа ТТ№ ТС€ Сa)СpСThe first stage averaging is computed at discrete time instances once every n DCME frames, where n is operator selectable (n = 4, 16, 32, 64 or 128). The result of the computation is the ensemble average taken over the ensemble of BCs which are carrying voice traffic and will result in one of the following possible outcomes:ЦЦ Та ТТ№ ТРIРТhpТ = 4 for N РCР MЦЦ Та ТТ№ ТРIРТhpТ = 4M/N for 3N/4 РCР M < NЦЦ а H аТа ТТ№ ТТhpТТhи ТС€pСС€Сwith M =СЈ Сtotal number of 4 bit bearer time slots in the pool which are not used for voice band data, bit banks and 64 kbit/s onЉdemand traffic counted in the measurement frame.ЦЦ а H аТа ТТ№ ТТhpТN =СЈ Сtotal number of connected active voice ITs, counted in the measurement frame.ЦЦ Та ТТ№ ТТhpТС€СTwo ensemble averages should be determined:ЦЦ а H аТа ТТ№ ТРIРТhpТ РIР which is the УУactualФФ measured ensemble average of encoding bits/sample based on  РIР actual counts of M and N.ЦЦ а Hh аТа ТТ№ ТРIРТhpТ РIР which is the УУpredictedФФ ensemble average of encoding bits/sample based on the  РIР actual count of N and a reduced count of MРIР2.ЦЦ а H аТа ТТ№ ТС€ Сb)СpСThe second stage averaging should be a moving discrete time averaging of and :ЦЦ а H аТа ТТ№ ТРIРТhpТSta РIР which is the moving discrete time average of 100 consecutive values of .ЦЦ а H аТа ТТ№ ТРIРТhpТStp РIР which is the moving discrete time average of 100 consecutive values of .ЦЦ а H аСR ССR СThe value of Sta may be used as a measure of the average number of encoding bits/sample when determining the dynamic load control condition for voice and voice band data channels.ЦЦ а H аТа ТТ№ ТThe value of Stp may be used as a measure of the average number of encoding bits/sample when determining the dynamic load control condition for onЉdemand 64 kbit/s channels.ЦЦ а H аB.2Тh  ТУУTransmit activity detector threshold and operate time characteristicФФЦЦ а H аС СA typical response to a sinusoidal stimulus signal in the band 300 to 3400 Hz will be as given below: С СУУAverage signal powerФФ (see Note)С,/СС/`4СУУOperate timeФФ ‚С С< Љ40 dBm0СЈ СС СС X%СС%А*СС*/СOFF С СР Р Љ40 dBm0, РCР Љ30 dBm0С#X%СС%А*СFigure BЉ1/G.763 С С> Љ30 dBm0СЈ СС СС X%СС%А*СС*/С2 ms < t < 4 ms С СThe operate time requirements will be satisfied while permitting tolerances on the average signal power of any stimulus signal in the frequency band at boundary conditions as follows: С СЉ40 dBm0 ггУУ+ФФ 1.5 dB С СЉ30 dBm0 УУ+ФФ 1.0 dB С СA typical rate of change of the transmit activity detector adaptive threshold will be between 2.5 dB/s and 20.0 dB/s. а H аС СУУNoteФФ РIР The activity detector should not indicate activity for idle channel noise less than Љ40 dBm0. ‚Ср RСб cмˆ4 PŽТ бFIG. BЉ1/G.763 б cмˆ4 PŽТ б B.3Тh  ТУУData/speech discriminatorФФЦЦ а H аС СFunctionally, the data/speech (D/S) discriminator determines whether the activity on each transmit IT is speech or data and provides a speech/data indication to the hangover control and signal classification process. С СThe implementation of the D/S discriminator may be performed by a combination of spectral analysis and 2100 Hz tone detection. С СThe following requirements should be met with the modem types and bit rates given in Table 7/G.763. Та ТB.3.1Си СУУOutput conditionsФФЦЦ а H аС СThe D/S discriminator analyzes the activity on each transmit IT and provides the following output conditions: С СУУActivityФФСЈ СС СС X%СС%А*СС*/СС/`4СУУOutput conditionФФ С СSpeechСи ССЈ СС СС X%СС%А*СС*/СР"РVoiceР"Р С СTones except 2100 HzС!X%СС%А*СС*/СР"РVoiceР"Р С СData signal (see Note)С#X%СС%А*СС*/СР"РDataР"Р С С2100 HzСP ССЈ СС СС X%СС%А*СС*/СР"РDataР"Р С СУУNoteФФ РIР V.23 modem signals may be classified as either voice or data dependent upon the design of the data/speech discriminator. а H аС СThe D/S discriminator provides a continuous output condition indicating the presence of either speech or data on the ITs. The current output condition should be maintained upon termination of activity on the IT or until the output condition of a subsequent activity is determined. Upon system startЉup or map change, the D/S discriminator should be reset to Р"РVoiceР"Р. Та ТС€ HСB.3.2 С СУУAccuracyФФЦЦ С СThe missed detection probability of data as speech or speech as data should be less than 0.5%. Та ТС€ HСB.3.3 С СУУResponse timeФФЦЦ а H аС СThe D/S discriminator should update its output condition within 200 ms after any of the following changes in the signal characteristics on the IT: Та ТРIРТ№ ТInactiveЉtoЉspeechЦЦ Та ТРIРТ№ ТInactiveЉtoЉdataЦЦ Та ТРIРТ№ ТSpeechЉtoЉdataЦЦ Та ТРIРТ№ ТDataЉtoЉspeechЦЦ а HH аТа ТС€ HСB.3.4С СУУ2100 Hz tone detectionФФЦЦ а Hh аС СThe 2100 Hz tone detector should meet the following requirements: аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи ˆXА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТа ТРIРТ№ ТFrequency range of tone:С'А*СС*/СС/`4С2100 УУ+ФФ 21 HzЦЦ Та ТРIРТ№ ТMinimum amplitude of tone:С)/СС/`4СЉ25 dBm0ЦЦ Та ТРIРТ№ ТResponse time:СˆССX%СС%А*С< 100 ms (for further study)ЦЦ а HH ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаB.4Тh  ТУУ2400 Hz tone detectorФФЦЦ а Hh аС СThe 2400 Hz tone detector should meet the following requirements: аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи ˆXА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТа ТРIРТ№ ТFrequency of tone:С!X%СС%А*СС*/С2400 Hz УУ+ФФ 15 HzЦЦ Та ТРIРТ№ ТMinimum amplitude of tone:С)/СС/`4СЉ25 dBm0ЦЦ Та ТРIРТ№ ТResponse time:СˆССX%СС%А*С< 50 msЦЦ Та ТРIРТ№ ТMissed detection probability:С,/СС/`4С< 0.5%.ЦЦ а HH ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаB.5Тh  ТУУSpeech detector/echo control device interactionsФФЦЦ а H аС СConsideration must be given to minimizing excessive channel loading which may exist as the result of network interactions between the DCME speech detector and an echo control device (see Figure BЉ2/G.763). а H аС СIf the DCME utilizes an adaptive threshold speech detector, interaction between the speech detector threshold adjustment and the echo control operation may generate excessive activity in the channel. The echo control device modulates the terrestrial circuit noise accumulated between the telephone and the sendЉinput port of the echo control device. The adaptive threshold speech detector may falsely classify this change in terrestrial circuit noise as speech and increase the load on the DCME. This will increase the occurrence of overload channels and/or freezeЉout, thereby degrading the performance in the baseband channel. This interaction occurs as follows: а H аТа ТТ№ ТС€ Сa)СpСReceive speech arrives at the receive input (Rin) port of the echo control unit.ЦЦ а H аТа ТТ№ ТС€ Сb)СpСThe echo suppression switch or canceller centre clipper activates, stopping the echo or residual echo and attenuating the nearЉendЉgenerated analogue terrestrial noise (N1) present at the send input (Sin) port.ЦЦ а H аТа ТТ№ ТС€ Сc)СpСIf very little noise is generated between the echo control send output (Sout) port and the DCME speech detector input, the speech detector threshold will adapt to its minimum level (typically Љ50 dBm0).ЦЦ а H аТа ТТ№ ТС€ Сd)СpСWhen the receive speech stops, after a suitable echo control unit handover time the echo suppression switch or canceller centre clipper will close and the nearЉendЉgenerated terrestrial noise, as seen by the DCME speech detector will reappear as a step change in noise level.ЦЦ а H аТа ТТ№ ТС€ Сe)СpСThis step change in noise level may exceed the speech detector threshold, causing the DCME to transmit a noise spurt as if it were speech. The noise spurt duration will be a function of the adaptation speed of the speech detector and the nearЉendЉgenerated terrestrial noise level.ЦЦ а H аС СThis sequence will be repeated for every speech spurt and will produce a very annoying speechЉcorrelated noise spurt heard by the farЉend talkers every time they stop speaking. С СThis interaction is not limited to single echo control device network configurations. A typical network configuration with multiple echo control devices interacting with a DCME speech detector is shown in Figure B-3/G.763. In this configuration, the DCME speech detector may respond to unit step increases in noise power which result from echo suppressor switch or echo canceller centre clipper activations in the send paths of echo control devices 1 and 3. The DCME speech detector will first experience a unit step increase in noise power from echo control device 3 switch activation, followed by a second step increase from echo control device 1 switch activation. The extent to which the DCME speech detector incorrectly responds to these step increases in noise power will be a function of the noise power levels Nб cмˆ4 PŽТ бУУ1ФФб cмˆ4 PŽТ б, Nб cмˆ4 PŽТ бУУ2ФФб cмˆ4 PŽТ б, Nб cмˆ4 PŽТ бУУ3ФФб cмˆ4 PŽТ б, and Nб cмˆ4 PŽТ бУУ4ФФб cмˆ4 PŽТ б, and the specific DCME speech detector threshold adaptation algorithm. For example, the dual step increases in noise presented to the DCME speech detector which result from switch or centre clipper activation at locations 1 and 3 will be masked if the power level of Nб cмˆ4 PŽТ бУУ4ФФб cмˆ4 PŽТ б is excessively high. Likewise, high noise power levels at Nб cмˆ4 PŽТ бУУ2б cмˆ4 PŽТ б ФФor NУУб cмˆ4 PŽТ б3б cмˆ4 PŽТ бФФ may mask step increases in noise power caused by echo control unit 1. а H аС СThere are several methods for dealing with the interactions between the echo control devices and the DCME speech detector. In one approach, the а H аecho control device could be modified to monitor the terrestrialЉgenerated noise at the sendЉinput port. When the send transmission path is broken, noise at а H аthe proper level is injected into the send-output toward the DCME, keeping the noise seen by the speech detector at a constant level and avoiding speech а H аdetector activation. This approach is unacceptable due to the number of different echo control devices in use and the uniqueness of the application. In a second approach, the speech detector adaptive threshold would be frozen in the presence of speech on the corresponding receive channel. A third approach would be to specify an adaptive speech detector with a fast adaptation feature which would track step changes in noise level and minimize the noise spurts. С СThe transmit activity detector threshold should not adapt to Gaussian noise level variations which are due to the action of echo suppressors or echo cancellers. This may be accomplished by any means which is functionally equivalent to providing the transmit activity detector with a threshold inhibit signal from a receive activity detector when activity is present on the receive channel (see РSР 12.4).‚б cмˆ4 PŽТ б Ср NСFig. BЉ2/G.763 = 7,5 cm б cмˆ4 PŽТ б Ср OСб cмˆ4 PŽТ бFig. BЉ3/G.763 = 6 cm б cмˆ4 PŽТ б B.6Тh  ТУУTiming synchronizationФФЦЦ С СThe following figures provide a number of examples of Doppler and plesiochronous slip buffer placements for a variety of network synchronization schemes. In the figures it is assumed that all buffers will derive their write clocks from the input bit stream. Та ТС€ HСB.6.1С СУУPointЉtoЉpoint operationФФЦЦ Та ТС€ HСB.6.1.1СpСУУTerrestrial operation within a national networkФФЦЦ С СFigures BЉ4/G.763 and BЉ5/G.763 show methods of DCME terminal synchronization for operation within a national network.‚б cмˆ4 PŽТ б Ср KСFig. BЉ4 y BЉ5/G.763 = 12 cm б cмˆ4 PŽТ б Та ТС€ HСB.6.1.2СpСУУTerrestrial operation between national networksФФЦЦ С СFigures BЉ6/G.763, BЉ7/G.763 and BЉ8/G.763 show methods of terminal synchronization for operation between national networks via terrestrial networks. Plesiochronous buffers are required for networks as shown in Figures B-6/G.763 and BЉ7/G.763. Figure BЉ8/G.763 utilizes loop timing and therefore does not require plesiochronous buffering. ‚Ср NСб cмˆ4 PŽТ бFig. BЉ6/G.763 = 6,5 cm б cмˆ4 PŽТ бб cмˆ4 PŽТ б Ср KСFig. BЉ7 y BЉ8/G.763 = 13 cm б cмˆ4 PŽТ б а H аТа ТС€ HСB.6.1.3СpСУУSatellite operation between national networks based upon continuous digital carrier type servicesФФЦЦ а H аС СFigures BЉ9/G.763, BЉ10/G.763, BЉ11/G.763 and BЉ12/G.763 show methods of terminal synchronization for operation between national networks over a satellite link based upon asynchronous continuous digital carrier type services. Figure BЉ9/G.763 introduces controlled slips between the DCMEs which are limited to 1 in 70 days if G.811 clocks are available in both networks. The configuration shown in Figures BЉ10/G.763, BЉ11/G.763 and BЉ12/G.763 permit slip free operation between the DCMEs. ‚б cмˆ4 PŽТ б Ср EСFig. BЉ9, BЉ10 y Fig. BЉ11/G.763 = 6,5 cm б cмˆ4 PŽТ бб cмˆ4 PŽТ б Ср OСBЉ12 /G.763 = 6,5 cm б cмˆ4 PŽТ б а H аТа ТС€ HСB.6.1.4СpСУУSatellite operation between national networks based upon TDMA type servicesФФЦЦ С СFigures BЉ13/G.763 and BЉ14/G.763 show a method of DCME terminal synchronization for operation between national networks over a satellite link based on TDMAЉtype services. An appropriate interface is provided in the TDMA terminal to permit interfacing the DCME with and without multiЉclique over a primary multiplex port. The configuration shown in Figure BЉ13/G.763 permits slip free operation between the DCMEs. Та ТС€ HСB.6.2С СУУMultiЉclique operationФФЦЦ Та ТС€ HСB.6.2.1СpСУУTerrestrial operation within a national networkФФЦЦ С СFigure BЉ15/G.763 shows a method of DCME terminal synchronization for operation within a national network. The cross connect function provides a means of assembling the received multiЉclique pools on to a single primary multiplex. Та ТС€ HСB.6.2.2СpСУУTerrestrial operation between national networksФФЦЦ С СFigure BЉ16/G.763 shows a method of DCME terminal synchronization for operation between national networks via terrestrial facilities. Plesiochronous buffers are required to resolve timing differences between the various plesiochronous networks. Due to the multiple source nature of the multiЉclique configuration, the plesiochronous buffers must be placed before the cross connect function. а H аТа ТС€ HСB.6.2.3СpСУУSatellite operation between national networks based upon continuous carrier type servicesФФЦЦ С СFigure BЉ17/G.763 shows a method of DCME terminal synchronization for operation between national networks based on continuous digital satellite carriers. Plesiochronous/doppler buffers are required to resolve timing differences between the various plesiochronous networks and to remove satellite induced doppler shifts on the received data streams. Due to the multiple а H аsource nature of the multiЉclique configuration, the plesiochronous/doppler buffers must be placed before the cross connect function.‚б cмˆ4 PŽТ б Ср NСFig. BЉ13/G.763 = 22 cm Ср NСFig. BЉ14G.763 = 22 cm Ср NСFig. BЉ15/G.763 = 22 cm Ср NСFig. BЉ16/G.763 = 22 cm б cмˆ4 PŽТ бб cмˆ4 PŽТ б Ср NСFig. BЉ17/G.763 = 22 cm б cмˆ4 PŽТ б Та ТС€ HСB.6.3С СУУMultiЉdestination operationФФЦЦ Та ТС€ HСB.6.3.1СpСУУTerrestrial operation within a national networkФФЦЦ С СFigure BЉ18/G.763 shows a method of DCME terminal synchronization for operation within a national network. The received data streams are assumed to originate from mutually synchronized sources. Та ТС€ HСB.6.3.2СpСУУTerrestrial operation between national networksФФЦЦ С СFigure BЉ19/G.763 shows a method of DCME terminal synchronization for operation between national networks via terrestrial facilities. Plesiochronous buffers are required to resolve timing differences between the various plesiochronous networks. Due to the multiple source nature of the multiЉ destination configuration, the plesiochronous buffers must be placed before the DCME receive function. а H аТа ТС€ HСB.6.3.3СpСУУSatellite operation between national networks based upon continuous carrier type servicesФФЦЦ С СFigure BЉ20/G.763 shows a method of DCME terminal synchronization for operation between national networks based on continuous digital satellite carriers. Plesiochronous/doppler buffers are required to resolve timing differences between the plesiochronous networks and to remove satellite induced doppler shifts on the received data streams. Due to the multiple source nature of the receive signals in the multiЉdestination configuration, the plesiochronous/doppler buffers must be placed before the DCME receiver. а H аТа ТС€ HСB.6.3.4СpСУУSatellite operation between national networks based upon TDMAЉtype servicesФФЦЦ С СFigures BЉ21/G.763 and BЉ22/G.763 show a method of DCME terminal synchronization for operation between national networks over a satellite link based on TDMAЉtype services. An appropriate interface is provided in the TDMA terminal to permit interfacing the DCME over a primary multiplex port. The configuration shown in Figure BЉ21/G.763 permits slip free operation between the DCMEs. B.7Тh  ТУУPerformanceФФЦЦ Та ТС€ HСB.7.1 С СУУSpeech performanceФФ (provisional)ЦЦ а H аС СRecommendation P.84 describes a subjective test method for comparing the performance of DCME systems against suitable reference conditions for carefully defined input signals. Recommendation P.84 consists of listening tests and is the recommended source of information about subjective testing of DCME. These tests are a first step and do not preclude the need for conversational tests. а H аС СIt is recommended that a fixed delay be inserted in the transmit speech path to reduce the probability of front end clipping. This delay compensates for activity detection time and DCME assignment message connection delay. The delay should be such as to assure that the main speech spurt clipping is less than 5 ms. Та ТС€ HСB.7.2С СУУVoice band data performanceФФЦЦ С СExtensive testing has demonstrated satisfactory voice band data performance for the 40 kbit/s algorithm specified in Recommendation G.726 for voice band data rates up to 9600 bit/s. С СVoice band data at rates up to 12 000 bit/s can be accommodated by 40 kbit/s ADPCM. The performance of V.33 modems operating at 14 400 bit/s over 40 kbit/s ADPCM is for further study. Selection of a 64 kbit/s unrestricted channel through a DCME is also possible and may be used for V.33 modems operating at 14 400 bits.‚б cмˆ4 PŽТ б Ср NСFig. BЉ18/G.763 = 22 cm б cмˆ4 PŽТ б Ср NСб cмˆ4 PŽТ бFig. BЉ19/G.763 = 22 cm б cмˆ4 PŽТ б Ср NСб cмˆ4 PŽТ бFig. BЉ20/G.763 = 22 cm б cмˆ4 PŽТ б Ср NСб cмˆ4 PŽТ бFig. BЉ21/G.763 = 22 cm б cмˆ4 PŽТ б Ср NСб cмˆ4 PŽТ бFig. BЉ22/G.763 = 22 cm б cмˆ4 PŽТ б У УSupplement No. 1 Ср SСб cмˆ4 PŽТ бDCME TUTORIAL б cмˆ4 PŽТ бФ Ф Ср MС(to Recommendation G.763) У У1ТX ТUse of digital circuit multiplication system (DCMS)Ф ФЦЦ С СDCMS provide the means to reduce the cost of transmission (e.g. long distance transmission) by making use of the combination of digital speech interpolation (DSI) and low rate encoding (LRE) techniques. а H аС СDSI is used to concentrate a number of input channels (generally referred to as trunk channels) onto a smaller number of output channels (generally referred to as bearer channels). It does this by connecting a trunk channel to a bearer channel only for the period that the trunk channel is active, i.e. is carrying a burst of speech or voiceЉband data. Since in average conversations one direction of transmission is active only for 30% to 40% of the time, if the number of trunks is large the statistics of the speech and silence distributions will permit a significantly smaller number of bearer channels (bearer channel pool) to be used. Control information must also be passed between the terminals to make sure that bearer and trunk channel assignments at each end remain synchronized. С СLRE uses digital filtering techniques to construct an estimate of the waveform at both the encoder and the decoder. Since the actual information rate of speech is much lower than the channel Nyquist rate the link used between the LRE encoder and the decoder can operate at a rate which is dependent mainly on the quality of the models and the permissible amount of transmission degradation. The CCITT has standardized in Recommendations G.726 and G.727 a type of LRE known as ADPCM, the performance of which has been extensively characterized. DCME uses the ADPCM defined in Recommendation G.726. а H аС СFacsimile compression uses recognition and decoding of some or all of the voiceЉband signals sent by the modem to enable the subЉmultiplexing of the digital information from a number of trunk channels onto a reduced number of bearer channels with the object of enhancing both the quality and the efficiency of transmission as compared to rate reduction of the signals using ADPCM. This is under study. а H аС СThe simplest way to use DCMS is in the single destination mode as shown in Figure 1/G.763. This mode of operation is most economic for the largest routes. For smaller routes there are two options: Та ТРIРТ№ Тoperation in multiЉclique mode,ЦЦ Та ТРIРТ№ Тoperation in multiЉdestination mode.ЦЦ а H аС СOperation in multiЉclique mode, see Figure 2/G.763, divides the bearer channels into a number of blocks or cliques, each associated with a different route. There is normally a fixed boundary between cliques, and trunk/bearer channel assignments are generally carried in a control channel within the clique to which they refer. This limits the dynamic processing of received channels to those which are contained in the wanted clique; selection of the wanted clique channels can be done using a simple static digital switch without reference to the assignment information. With a 2048 kbit/s bearer system in multiЉclique DCMS the statistics of the DSI are unpromising with more than three routes. Recommendation G.763 provides for two cliques. С СOperation in multiЉdestination mode, see Figure 3/G.763, permits any bearer channel to be associated with any trunk channel of any of a number of different routes. There is no segregation of routes on the bearer, and therefore at the receive terminal it is impossible to select the wanted channels without reference to the assignment information. MultiЉdestination mode is economic for very small routes via satellite, but practical difficulties limit the number of routes which it is desirable to have on a single DCMS.‚У У Та Т2СpСLocationФ ФЦЦ а H аС СLocation of DCME depends on its use. Equipment used in single destination mode or in multiЉclique mode can in general be located at: Та ТРIРТ№ ТISC,ЦЦ Та ТРIРТ№ Тearth station,ЦЦ Та ТРIРТ№ Тcable head,ЦЦ а H аwithout significant restrictions. Equipment used in the multiЉclique mode will typically be located at the ISC so that the advantages of DCMG can be extended over the national section. Equipment used in the multiЉdestination mode will typically be located at the earth station or cable head. The reason for this is that whereas in multiЉclique mode the number of receive bearer channels at the DCME terminal is approximately equal to the number of transmit bearer channels, in multiЉdestination mode the number of receive bearer channels at the DCME terminal is the number of transmit bearer channels multiplied by the number of destinations. It therefore may be uneconomic to provide sufficient transmission capacity between earth station and ISC to permit location of multiЉdestination DCME at an ISC. ‚У У3ТX ТTransmission requirementsФ ФЦЦ а H аС СDCMS are usually required to carry any traffic which can be carried on ordinary General Switched Telephone Network (GSTN) connections. That includes voiceЉband data using VЉSeries Recommendation GSTN modems, facsimile calls following Recommendations T.4 and T.30 and using V.29 modems. In addition, in the ISDN 64 kbit/s unrestricted onЉdemand digital data and alternate speech/64 kbit/s unrestricted bearer services must be carried. С СDCMS are primarily designed to maximize the efficiency of speech transmission. Use with voiceЉband data, especially at high rates, presents problems. These problems are mainly due to the difficulty for 32 kbit/s ADPCM of encoding voiceЉband data waveforms. ‚У У4ТX ТDCME gain (DCMG)Ф ФЦЦ а H аС СThe gain of DCME is the input trunk channel transmission multiplication ratio, which is achieved through application of DCME, including LRE and DSI (for a specified speech quality at a certain level of bearer channel activity). The maximum available gain depends on: Та ТРIРТ№ Тnumber of trunk channels;ЦЦ Та ТРIРТ№ Тnumber of bearer channels;ЦЦ Та ТРIРТ№ Тtrunk channel occupancy;ЦЦ Та ТРIРТ№ Тspeech activity;ЦЦ Та ТРIРТ№ ТvoiceЉband data traffic;ЦЦ Та ТРIРТ№ Тratio of half duplex to full duplex voiceЉband data;ЦЦ Та ТРIРТ№ Тtype of signalling;ЦЦ Та ТРIРТ№ Т64 kbit/s traffic;ЦЦ Та ТРIРТ№ Тminimum acceptable speech quality;ЦЦ Та ТРIРТ№ Тdynamic load control threshold.ЦЦ а H аС СOf these the factor which has the greatest significance is the percentage of 64 kbit/s digital data traffic. This is because a trunk channel carrying 64 kbit/s traffic requires two 32 kbit/s bearer channels to be removed from the pool of channels available to the DSI process. а H аС СThe peak percentage of voiceЉband data may vary between 5 and 30 per cent, depending on route. This is discussed in greater detail in Supplement No. 2. а H аС СThe type of signalling system used on the route can significantly affect the gain. Continuously compelled signalling systems hold channels active а H аfor undesirably long periods. In the case of CCITT R2 digital signalling via a DCMS used on a satellite, the channel might be active for 5 to 14 seconds. С СThe measured speech activity depends on the characteristics of the activity detector. It is usual to assume 35 to 40 per cent. Channels with high ambient background noise can increase this activity factor. Outside of the route busy hour the occupancy of the trunk channels by traffic will be lower than in the route busy hour. The effect of this is to reduce the ensemble activity measured by the activity detector to about 27 per cent outside the route busy hour, whereas it will be close to the speech activity factor, i.e. about 40 per cent during the route busy hour. а H аС СThe speech quality is governed by two main factors; the LRE encoding rate, and the amount of speech lost while a newly active trunk channel is а H аawaiting connection to a bearer channel. If there are a great many newly active trunk channels in competition the beginning of a burst of speech is more likely to be clipped or frozen out than if relatively few trunk channels are active. С СThe speech quality of a DCME in a network with external echo control devices may be affected by clipping introduced by echo control devices and by a possible noise contrast effect. In particular when echo suppressors or echo cancellers are used on circuits where the near end generated noise is high with respect to the noise generated in the remainder of the link, suppression of the far end noise may be objectionable due to noise contrast. Possible means of eliminating this problem are use of echo control devices which insert idle line noise at the appropriate level during suppression periods, or insertion of idle line noise at the DCME during the relevant period when the echo control device is integrated in the DCME. Another approach is discussed in Annex B, РSР B.5 to Recommendation G.763. а H аС СWhen commissioning a new DCMS, observations should be made of the type and characteristics of the traffic which will use it. It is unwise to rely solely on customer complaints to indicate when a system is poorly dimensioned. This is because interactions between the DCMS and echo control (note) may obscure the true problem. Furthermore the consequence of trying to concentrate too many trunk channels onto too few bearers may be simply to increase the calling rate and to reduce the call holding time. This may result in greatly reduced quality, especially where continuously compelled signalling systems are used, and levels of trunk channel activity occur far above what was envisaged in the original system dimensioning. С СУУNoteФФ РIР This highest speech quality is obtained when echo cancellers conforming to Recommendation G.165 (Red Book) are used for echo control. However echo suppressors conforming to Recommendations G.164 (Red Book) and G.161 (Yellow Book) may be used. а H аС СTwo possible criteria for acceptable speech performance are an average of 3.7 bits per sample and less than 2.0% probability of clipping exceeding 50 ms, or alternatively that less than 0.5% of speech should be lost due to clipping. а H аС СUsing the above criteria, approximations have been derived that relate the percentage of voiceЉband data and the number of trunk channels to the gain of a DCME. Approximations intended for use in initial system dimensioning are given in Supplement No. 2 to Recommendation G.763. а H аС СIf a more accurate representation is required, then it will be necessary to do the first order Markov chain analyses referred to in the literature on DSI [1], [2], [3].‚У У Та Т5СpСISDN bearer servicesФ ФЦЦ а Hx аС СDCMS are generally required to carry the full range of ISDN bearer services which can be provided on a 64 kbit/s channel as specified in Recommendation I.230 (Blue Book). These are: а H аТа ТРIРТ№ ТCircuit mode 64 kbit/s unrestricted, 8 kHz structured bearer service category.ЦЦ а H аТа ТТ№ ТThis may be used among other things for speech, multiple subЉrate information streams multiplexed by the user, or for transparent access to an X.25 public network.ЦЦ а H аТа ТРIРТ№ ТCircuit mode 64 kbit/s, 8 kHz structured bearer service category, usable for speech information transfer.ЦЦ а H аТа ТТ№ ТТhpТС€СThis is broadly similar to the preceding category, but with different access protocols.ЦЦ а H аТа ТРIРТ№ ТCircuit mode 64 kbit/s, 8 kHz structured bearer service category, usable for 3.1 kHz audio information transfer.ЦЦ а H аТа ТТ№ ТThis bearer service provides the transfer of 3.1 kHz bandwidth audio information, such as for example voiceЉband data via modems, Group I, II and III facsimile information, and speech.ЦЦ а H аТа ТРIРТ№ ТCircuit mode alternate speech/64 kbit/s unrestricted 8 kHz structured bearer service category.ЦЦ а H аТа ТТ№ ТThis service is similar to both the unrestricted and speech 64 kbit/s circuitЉmode bearer services, but provides for the alternate transfer of either voice or unrestricted digital information at 64 kbit/s within the same call.ЦЦ а HH а‚У У6ТX ТRestoration of servicesФ ФЦЦ а H аС СFor most applications the loss of traffic under failure conditions would be such that it would be insufficient to install a single pair of terminals on a route without a means of rapid changeover to spare equipment in the event of failure. This means that DCME is often used in a cluster of N active DCMEs for one standby. Automatic changeover permits the standby to be loaded with the configuration and synchronization information of the failed terminal. Other automatic fallback modes may be considered. а H аС СFailure of the transmission system between DCME terminals can be handled by normal transmission system restoration procedures. Failure of the transmission systems entering the DCME terminals from the exchanges may result in a wide range of different alarm conditions being experienced particularly where a multiЉdestination DCME terminal serves more than one exchange and more than one route. It is desirable to limit the generation of alarm conditions to the channels which have actually failed. ‚У У7ТX ТControl of transmission overloadФ ФЦЦ С СThe reduction in the number of bearer channels available to the interpolation process, due to the high activities of voice band and 64 kbit/s data services or statistical variations in the ensemble input speech activity can occur when the number of instantaneously active trunk channels exceeds the number of available bearer channels. Either event requires action to be taken to safeguard speech quality. There are four possible solutions: а H аТа ТРIРТ№ ТThe system can be dimensioned so that with the maximum anticipated shortЉterm trunk channel activities there is negligible probability of violating the speech quality criteria. This employs the DCMS very inefficiently outside the busy hour.ЦЦ а H аТа ТРIРТ№ ТA multiЉdestination system can be made to carry routes with widely different busy hours, so that though the trunk channels might have relatively low nonЉbusy hour occupancy, the bearer channels would always be well loaded.ЦЦ а H аТа ТРIРТ№ ТSignals can be sent from the DCME to the exchange to busy out part of the route when the quality criteria are violated. This is known as dynamic load control (DLC), and can be an effective control method, but it cannot be retrospective and it is slow to take effect. Furthermore care must be taken to ensure that when circuits are returned to service the increase in bearer channel activity is not sufficient to result in the immediate reapplication of DLC.ЦЦ а Hx аТа ТРIРТ№ ТThe signal to quantization performance can be traded against the clipping of speech bursts. By using variable rate ADPCM algorithms it is possible to quantize to three or optionally two rather than four bits on individual speech channels on a pseudoЉcyclic basis for a given number of samples. In this way the system can be given a gradual degradation characteristic, rather than suddenly overloading.ЦЦ а H аС СIn a DCME conforming to Recommendation G.763 all of these techniques may be used. ‚У У8ТX ТTransmission link performance monitoringФ ФЦЦ а H аС СExperience with DCMEs has shown the value of using cyclic redundancy check information in the detection and tracing of certain faults. In order to provide a comprehensive set of longЉterm and shortЉterm indicators the DCME should provide the following means of monitoring the performance of any digital path(s) terminated upon it: Та ТРIРТ№ Тcyclic redundancy check (CRC);ЦЦ Та ТРIРТ№ Тframe alignment signal (FAS);ЦЦ Та ТРIРТ№ Тother primary rate alarms;ЦЦ Та ТРIРТ№ Тfar end block error information of distant CRC (FEBE);ЦЦ Та ТРIРТ№ ТDCME control channel FAS;ЦЦ Та ТРIРТ№ Тviolations of the Golay FEC of the control channel(s).ЦЦ аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаС  СС  С‚У УReferencesФ ФЦЦ а H ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬа[1]Тh  ТKOU (K.Y.), O'NEAL (J.B.), NILSON (A.A.): Computations of DSI (TASI) overload as a function of the traffic offered, УУIEEE Trans. on CommunicationsФФ, Vol. COMЉ33, No. 2, February 1985.ЦЦ [2]Тh  ТBRADY (P.T.): A model for generating onЉoff speech patterns in 2Љway conversation, УУBell System Technical JournalФФ, page 2445 УУet seqФФ, September 1969.УУ ФФЦЦ [3]Тh  ТSpecial issue on bit rate reduction and speech interpolation, Guest Editors M.R. Aaron and N.S. Tayant, УУIEEEФФ УУTrans. on communicationsФФ, Vol. COMЉ30, No. 4, April 1982.ЦЦ ‚У У Supplement No. 2 Ср 8Сб cмˆ4 PŽТ бDCME DIMENSIONING METHODS FOR DIFFERENT ROUTE CHARACTERISTICS б cмˆ4 PŽТ бФ Ф Ср MС(to Recommendation G.763) У У1ТX ТIntroductionФ ФЦЦ а H аС СThis supplement draws attention to the implications of the measurements of channel occupancy and voiceЉband data levels which have been done on particular routes for which the number of voiceЉband data calls is either large in absolute terms, or large compared to the total number of calls. ‚У У2ТX ТRoute profilesФ ФЦЦ С СFigure 1 shows the kind of profile which has been obtained from measurements on an FDM route between the United Kingdom and a country for which the proportion of voiceЉband data calls was suspected to be high. It can be seen from this that there are two peaks which are of interest in DCME dimensioning РIР one (the voice peak) where voice is the dominant feature with a relatively small amount of voiceЉband data, and another (the data peak) where voiceЉband data dominates voice. С СУУNoteФФ РIР The data profile is not symmetric in each direction of transmission. а H аС СVoiceЉband data requires more bearer capacity than voice in a DCME system incorporating digital speech interpolation (DSI) and low rate encoding (LRE) and therefore it is not immediately obvious which of these peaks is the limiting factor when calculating the achievable gain of a DCME on a particular route. Each route has to be examined carefully to determine the achievable gain. The limiting value of the gain does not necessarily occur at either of the peaks and in practice a scan across several daysР$Р profiles is necessary to determine the achievable gain. ‚Ср VСб cмˆ4 PŽТ бFIG. 1 б cмˆ4 PŽТ б а H аС СFigure 2 shows a typical profile obtained from the TDMA route for the same country. Due to different traffic origins and loading distributions the voice and data peaks are coincident, and the transmit and receive profiles are more nearly symmetrical in this case. ‚Ср UСб cмˆ4 PŽТ бFIGURE 2 б cмˆ4 PŽТ б У У3ТX ТDCME operationФ ФЦЦ а H аС СFigure 3 shows a DCME consisting of a DSI stage and an LRE stage. Voice and voiceЉband data have to be treated separately in each of these stages when trying to access the achievable gain of a particular DCME faced with a particular route profile. 3.1Тh  ТУУDSI gain for voiceФФЦЦ а H аС СThis is dependent upon the number of input trunks carrying voice and it is УУnot a linear relationshipФФ. ‚б cмˆ4 PŽТ б Ср SСFig. 3 = 6 cm б cмˆ4 PŽТ б 3.2Тh  ТУУDSI gain for dataФФЦЦ С СFacsimile is the dominant data service and can be considered as half duplex, i.e. on a particular call if data is flowing in one direction of transmission at a particular time, then the opposite direction is silent. If а H аthe total amount of facsimile traffic in one direction of transmission is balanced by an equivalent amount in the opposite direction of transmission then a technique known as silence elimination can be employed to free the opposite channel when data is flowing in one direction. This leads to a theoretical DSI gain of 2. However, if the total facsimile traffic on a route is not balanced in each direction of transmission, making silence elimination difficult to implement (or if silence elimination has not been built into a particular DCME) then the DSI gain for voice-band data is 1. 3.3Тh  ТУУLRE gain for voiceФФЦЦ а H аС СStudies have indicated that the minimum acceptable average number of bits per sample is of the order of 3.6, which will be the threshold for operation of dynamic load control. Therefore the LRE gain for voice is unlikely to exceed 8/3.6. 3.4Тh  ТУУLRE gain for dataФФЦЦ а H аС СThe LRE gain for data depends on how many bits/sample a particular system allocates to a data call. С СIn this supplement all calculations assume the use of the 40 kbit/s encoding rate for voiceЉband data, in conformity with Recommendation G.763, therefore the LRE gain for data = 8/5. С СExamples for facsimile compression are not presented. ‚У У4ТX ТCalculation of DCME gainФ ФЦЦ а H аС СTable 1 gives some approximate nonЉanalytical formulas for calculation of the voice part of the DCME gain. It should be noted that these approximations are strictly valid only for DCMEs conforming to Recommendation G.763 and having ideal speech detection (i.e. the activity indicated by the speech detector is the same as the actual speech activity). ‚Ср NСб cмˆ4 PŽТ бinclude 04ЉT01ЉETABLE 1 Ср DСУ УFormulas for voice interpolation gain (Gv)Ф Ф б cмˆ4 PŽТ бвЦ„HШ И H8X Цв‡аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаСр VСааб cмˆ4 PŽТ бNo. of Ср VСNo. of Ср VСFormula аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHш@˜№X џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаActivity factor (AF) а 8 ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџ8ш@˜№X џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бˆа 8 аб cмˆ4 PŽТ бвЦ†HШ И H8јpЈ X Цв‡аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџpи 8џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаСр)ШjСб cмˆ4 PŽТ бbits/sam Ср)ШmСple Ср)ШiСtrunks (N) аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџxрHH8џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬа аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџ8ј`PџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаСр)ШmС33% Ср)ШmС35% Ср)ШmС37% а  ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџј`P џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бˆа  аб cмˆ4 PŽТ бвЦ†HШ И H8јpЈ X Цв‡аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџpи џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ б аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџ` Ш 0 ˜ џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬа аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџxрHH џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬа аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџј`P џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаСр<}Сa = 0.23 Ср<}Сa = 0.04 Ср<}Сa = 0.30 а  аб cмˆ4 PŽТ бˆа  аб cмˆ4 PŽТ бвЦ†HШ И H8јpЈ X Цв‡аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџpи џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ б аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџ` Ш 0 ˜ џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаСр<~СN < 80 а h ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџxрHH џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаGv = a + b РР 1n(N) аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџј`P џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬа а  аб cмˆ4 PŽТ бˆа  аб cмˆ4 PŽТ бвЦ†HШ И H8јpЈ X Цв‡аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџpи џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаСр<€Сб cмˆ4 PŽТ б3.6 аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџ` Ш 0 ˜ џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬа аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџј`P џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаСр<}Сb = 0.61 Ср<}Сb = 0.60 Ср<}Сb = 0.51 а  аб cмˆ4 PŽТ бˆа  аб cмˆ4 PŽТ бвЦ†HШ И H8јpЈ X Цв‡аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџpи џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ б аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџ` Ш 0 ˜ џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬа Ср<}СN > = 80 а x ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџxрHH џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаGv = eq \f(1.1388 РР N,N РР AF + \r(N РР AF)) аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџј`P џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬа Ср<а ‰СAF = 0.33 Ср<а ‰СAF = 0.35 Ср<а ‰СAF = 0.37 а  аб cмˆ4 PŽТ бˆа  аб cмˆ4 PŽТ бвЦ†HШ И H8јpЈ X Цв‡аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџpи џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ б аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџ` Ш 0 ˜ џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬа аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџxрHH џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬа аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџј`P џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаСр<}Сa = 0.23 Ср<}Сa = 0.04 Ср<}Сa = 0.27 а  аб cмˆ4 PŽТ бˆа  аб cмˆ4 PŽТ бвЦ†HШ И H8јpЈ X Цв‡аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџpи џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ б аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџ` Ш 0 ˜ џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаСр<~СN < 80 а h ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџxрHH џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаGv = a + b РР 1n(N) аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџј`P џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬа а  аб cмˆ4 PŽТ бˆа  аб cмˆ4 PŽТ бвЦ†HШ И H8јpЈ X Цв‡аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџpи џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаСр<€Сб cмˆ4 PŽТ б3.7 аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџ` Ш 0 ˜ џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬа аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџј`P џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаСр<}Сb = 0.61 Ср<}Сb = 0.60 Ср<}Сb = 0.52 а  аб cмˆ4 PŽТ бˆа  аб cмˆ4 PŽТ бвЦ†HШ И H8јpЈ X Цв‡аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџpи џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ б аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџ` Ш 0 ˜ џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬа Ср<}СN > = 80 а x ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџxрHH џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаGv = eq \f(1.1081 РР N,N РР AF + \r(N РР AF)) аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџј`P џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬа Ср<а ‰СAF = 0.33 Ср<а ‰СAF = 0.35 Ср<а ‰СAF = 0.37 а  аб cмˆ4 PŽТ бˆа  аб cмˆ4 PŽТ бвЦ†HШ И H8јpЈ X Цв‡аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџpи џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ б аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџ` Ш 0 ˜ џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬа аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџxрHH џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬа аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџј`P џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаСр<}Сa = 0.24 Ср<}Сa = 0.01 Ср<}Сa = 0.28 а  аб cмˆ4 PŽТ бˆа  аб cмˆ4 PŽТ бвЦ†HШ И H8јpЈ X Цв‡аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџpи џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ б аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџ` Ш 0 ˜ џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаСр<~СN < 80 а h ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџxрHH џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаGv = a + b РР 1n(N) аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџј`P џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬа а  аб cмˆ4 PŽТ бˆа  аб cмˆ4 PŽТ бвЦ†HШ И H8јpЈ X Цв‡аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџpи џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаСр<€Сб cмˆ4 PŽТ б3.8 аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџ` Ш 0 ˜ џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬа аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџј`P џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаСр<}Сb = 0.59 Ср<}Сb = 0.61 Ср<}Сb = 0.51д Д-дŒа  аб cмˆ4 PŽТ бˆа  аб cмˆ4 PŽТ бвЦ†HШ И H8јpЈ X Цв‡аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџpи џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ б аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџ` Ш 0 ˜ џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬа Ср<}СN > = 80 а x ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџxрHH џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаGv = eq \f(1.0789 РР N,N РР AF + \r(N РР AF)) аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџј`P џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬа Ср<а ‰СAF = 0.33 Ср<а ‰СAF = 0.35 Ср<а ‰СAF = 0.37 а  аб cмˆ4 PŽТ бˆа HH ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬа аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬа4.1Тh  ТУУLimitationsФФЦЦ а H аС СIdeally the calculation of the DCME gain would be done by a comprehensive computer modelling of the system in the way which has already been demonstrated with great success by Swedish Telecom Radio. Given an intimate knowledge of the route, in terms of its hourly, daily and seasonal variations in voice and voiceЉband data traffic flow, signalling systems, call holding times and effective/ineffective ratios over a period of time it may be possible to model the route with a high degree of accuracy, at least retrospectively. However the major limitation is the quality of the information fed into the model. To overcome this limitation the digital channel occupancy analyser (DCOA) has been developed. If the DCOA is used on a group of circuits which previous sampling or other information has shown to be typical then very useful dimensioning information results. The limitation then is the total permissible measuring time. In most cases, for operational reasons, greater than two weeks is unlikely to be feasible. This represents a severe limitation on the attempt to create an accurate model, such that for dimensioning (as opposed to the verification of the operation of the equipment) Monte Carlo type simulations do not appear to be necessary. 4.2Тh  ТУУExample gain calculations using simplified techniquesФФЦЦ С СThe following examples illustrate the concepts outlined in РSР 2, and demonstrate the use of a simplified technique for DCME dimensioning using DCOA route profiles. а H аТа ТС€ HС4.2.1С СУУDCME dimensioning using the profile of a route without silence eliminationФФЦЦ С СУУAssumptions:ФФ С СNumber of trunk channels at service date = 240. С СFigure 4 is the applicable DCOA route profile. ‚Ср VСб cмˆ4 PŽТ бFIG. 4 б cмˆ4 PŽТ б С СУУRemark:ФФ а H аС СFrom experience or from rough calculations it can be seen that for the given number of trunk channels and quantity of voiceЉband data traffic at least three DCMEs each using 30 bearer channels are likely to be required, but let us assume that four DCMEs are to be used on the route in order to calculate the gain for the voice traffic (this gain is dependent upon how many DCMEs the voice traffic is spread over). This is to ensure that the DCMEs are not overloaded and may also allow for growth on the route. In practice an iterative procedure would have to be used to determine the optimum number of DCMEs for each route. а H аС СFrom Figure 4 there are two peaks to be considered. One is dominated by the amount of data (data peak) and the other is dominated by the amount of voice (voice peak): аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаС СУУData peakФФ аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТа ТТ№ ТС€ С59% data:ЦЦ аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТа ТТ№ ТТhpТС€Сnumber of data trunksС$А*С=  240 РР 0.59ЦЦ Та ТТ№ ТТhpТСи СС С=  142 trunks,ЦЦ а Hр аТа ТТ№ ТТhpТС€Сeq \a\al\hs2(number of data trunks,per DCME)С;>Сeq =  \f(142,4)ЦЦ Та ТТ№ ТТhpТСи СС С=  036ЦЦ а H ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТа ТТ№ ТТhpТТhи ТТаЈ ТС€и СС€pСС€СDSI gainСЈ СС СС X%С=  001 (no silence elimination advantage to be gained because almost allЦЦ СF ССF ССpС=  001 the data is in one direction of transmission)ЦЦ аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТа ТТ№ ТТhpТС€СLRE gainС СС X%С=    eq \f(8,5)ЦЦ аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТа ТТ№ ТС€ С17% voice:ЦЦ аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаТа ТТ№ ТТhpТС€Сnumber of voice trunksС%А*С=  240 РР 0.17ЦЦ Та ТТ№ ТТhpТСи СС С=  041 trunks totalЦЦ Та ТТ№ ТТhpТштnumber of voice trunksЦЦ С& СС& Сper DCMEС С=  010ЦЦ Та ТТ№ ТТhpТС€СDSI gain (for 10 trunks)С'А*С=  1.25 (from tables)ЦЦ Та ТТ№ ТТhpТС€СLRE gainС СС X%С=   eq \f(8,3.6)ЦЦ а HH аС СHence the 64 kbit/s bearer channel requirement is: С СС Сeq \f(36 РР 5,8)  +  \f(10 РР 3.6,1.25 РР 8) С СС С=  23 (data) + 4 (voice) С СС С=  УУ27 bearer channels.ФФ С СThe total bearer requirement is therefore: С СС С27 РР 4 С СС С=  УУ108 bearer channels.ФФ С СУУVoice peakФФ С С13% data: Та ТТ№ ТТhpТС€Сnumber of data trunksС$А*С=  240 РР 0.13ЦЦ Та ТТ№ Т‚ТhpТСи СС С=  032 trunks total,ЦЦ а HX аТа ТТ№ ТТhpТС€Сeq \a\al\hs2(number of data trunks,per DCME)С;>Сeq =  \f(32,4)ЦЦ Та ТТ№ ТТhpТСи СС С=  8ЦЦ а H аТа ТТ№ ТТhpТС€СDSI gainС СС X%С=  001 (no silence elimination advantage to be gained because almost all tС-/СС/`4СС4И9С=  001 tthe data is in one direction of transmission),ЦЦ Та ТТ№ ТТhpТС€СLRE gainС СС X%С=     eq \f(8,5)ЦЦа HH а С С83% voice: С СС Сnumber of voice trunksС%А*С=  240 РР 0.83 С СС ССpССи СС С=  200 trunks total ‚С СТ№ Тnumber of voice trunks ЦЦ per DCMEСpС=  050 С СС СDSI gain (for 50 trunks)С'А*С=  1.92 (from tables) С СС СLRE gainС СС X%С=   eq \f(8,3.6) С СHence the 64 kbit/s bearer channel requirement per DCME is: С СС Сeq \f(8 РР 5,8)  +  \f(50 РР 3.6,1.92 РР 8) С СС С=  5 (data) + 12 (voice) С СС С=  УУ17 bearer channels.ФФ С СThe total bearer requirement is therefore: С СС С17 РР 4 С СС С=  УУ68 bearer channels.ФФ С СУУInference:ФФ а H аС СIt seems therefore that in this case the DCME dimensioning is determined by the number of trunk channels required to cope with the speech peak, and by the number of bearer channels required to handle the data peak. Since the number of channels shown as active by the DCOA is an average over the measurement interval, it is reasonable to assume that all 240 trunk channels, rather than only 132 were active for some brief duration. Assuming that only the wanted bearer channels are used, and neglecting the assignment channel, the achievable gain will be: С СС Сeq \f(240,108) = 2.22. а H аТа ТС€ HС4.2.2С СУУDCME dimensioning using the profile of a route with silence eliminationФФЦЦ С СУУAssumptions:ФФ С СNumber of trunk channels at service date = 347. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬа‚аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬа С СFigure 5 is the applicable DCOA route profile. аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬа‚Ср QСб cмˆ4 PŽТ бFig. 5 = 13,5 cm б cмˆ4 PŽТ б аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаС СУУRemark:ФФ а H аС СOn this route it appears that use of silence elimination will give some benefits. Other DCOA measurements have indicated that there is approximately twice as much voiceЉband data activity in the transmit direction as in the receive direction. Therefore the achievable DSI gain on voiceЉband data due to silence elimination is of the order of 1.5. This assumes that there are as many transmit as receive bearer channels on each DCME terminal. Rough calculations and experience indicate that because of the relatively low voiceЉband data percentage of this example three DCMEs will probably be sufficient. С СFrom Figure 5 there is only one peak to be considered: С С15% data: С СС Сnumber of data trunksС$А*С=  347 РР 0.15 С СС ССpССи СС С=  052 trunks ‚С СТ№ Тeq \a\al\hs2(number of data trunks,per DCME)С;>Сeq =  \f(52,3)ЦЦ С СС ССpССи СС С=  018 С СС СDSI gainС СС X%С=  1.5 (due to silence elimination) С СС СLRE gainС СС X%С=    eq \f(8,5) С С72% voice: С СС Сnumber of voice trunksС%А*С=  347 РР 0.72 С СС ССpССи СС С=  250 trunks total ‚С СТ№ Тnumber of voice trunks ЦЦ per DCMEСpС=  083 С СС СDSI gain (for 83 trunks)С'А*С=  2.08 (from tables). С СHence the 64 kbit/s bearer channel requirement per DCME is: С СС Сeq \f(18 РР 5,1.5 РР 8)  +  \f(83 РР 3.6,2.08 РР 8) С СС С=  8 (data) + 19 (voice) С СС С=  УУ27 bearer channels.ФФ С СThe total bearer requirement is therefore: С СС С27 РР 3 С СС С=  УУ81 bearer channels.ФФ С СУУInference:ФФ а H аС СIn this case, assuming that only the wanted bearer channels are used, the DCME can achieve a gain of: С СС Сeq \f(347,81)  = 4.28. а H ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаС СHowever, as was shown by the previous example, it would be very unwise to assume that a DCME gain as high as four will be achievable for all types of DCME, without careful consideration of the route conditions. A corollary to this is that when a DCME has been installed on a route its performance must be continually monitored to ensure that changes in the traffic distribution on the route do not impact seriously upon the transmission quality. 4.3Тh  ТУУTwo pitfalls for the unwaryФФЦЦ а H аС СFigure 6 shows a plausible example of a DCOA record, covering a typical two hour period. On the basis of the trunk occupancy percentage for the route it might be thought that the maximum bearer occupancy would be coincident with the peak in voice traffic, however this is not so. The actual maximum occurs immediately before, as Figure 7 shows, during period 2. The reason for this is that the voiceЉband data traffic peaks before the voice traffic. Administrations may wish to consider whether this is a likely state of affairs; whether for example the facsimile transmission of financial results at close of business on any particular day is likely to result in followЉup telephone conversations. The relevant information for each period is summarized in Table 2.‚б cмˆ4 PŽТ б Ср VСFIG. 6 б cмˆ4 PŽТ б Ср WСб cмˆ4 PŽТ бFIG 7 б cмˆ4 PŽТ б ‚Ср NСб cмˆ4 PŽТ бinclude 04ЉT02ЉETABLE 2 Ср DСУ УComparison of trunk and bearer occupanciesФ Ф б cмˆ4 PŽТ бвЦ‚Hши ЈЦв‡аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ б аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH0 ˆр8ш@ЈџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаPeriod а и Ш ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџи 0 ˆр8ш@ЈџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бˆа и Ш аб cмˆ4 PŽТ бвЦ…Hши ˜ ˆH8јpЈЦв‡аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџpи џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ б аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџи 0 ˜ hџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаСрРPС1 СрРPС2 СрРPС3 СрРPС4 а pШ ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџ0 ˜ hpџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бˆа pШ аб cмˆ4 PŽТ бвЦ…Hши ˜ ˆH8јpЈЦв‡аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџpи pџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ б %С3`4Сchs аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHHpџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџ Ьа%СH3`%Сchsƒ %С3`4Сchs аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџp@Ј˜џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬа%С3@8Сchs а pШ аб cмˆ4 PŽТ бˆа pШ аб cмˆ4 PŽТ бвЦ…Hши ˜ ˆH8јpЈЦв‡а pј ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџpи pџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бData occupancy 20С4и5С26 аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHHpџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџ Ьа25СH4и#С032.5ƒ 15С4и5С019.5 аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџp@Ј˜џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬа10С4@8С13 а pШ аб cмˆ4 PŽТ бˆа pШ аб cмˆ4 PŽТ бвЦ…Hши ˜ ˆH8јpЈЦв‡а p ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџpи pџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бSpeech occupancy 55С4и5С71.5 аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHHpџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџ Ьа55СH4и#С071.5ƒ 80С4и5С104.5 аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџp@Ј˜џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬа60С4@8С78 а pШ аб cмˆ4 PŽТ бˆа pШ аб cмˆ4 PŽТ бвЦ…Hши ˜ ˆH8јpЈЦв‡а p€ ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџpи pџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бTotal occupancy 75С4и5С97.5 аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHHpџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџ Ьа80СH4и#С104.5ƒ 95С4и5С123.5 аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџp@Ј˜џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬа70С4@8С91 а pШ аб cмˆ4 PŽТ бˆа pШ аб cмˆ4 PŽТ бвЦ…Hши ˜ ˆH8јpЈЦв‡а pш ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџpи pџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бData bearers С2ш3С13 аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHHpџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџ ЬаСH2ш#С016.5ƒ С2ш3С010.5 аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџp@Ј˜џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаС2@8С06.5 а pШ аб cмˆ4 PŽТ бˆа pШ аб cмˆ4 PŽТ бвЦ…Hши ˜ ˆH8јpЈЦв‡а pј ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџpи pџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бSpeech bearers С2ш3С15 аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHHpџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџ ЬаСH2ш$С15.5ƒ С2ш3С021.5 аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџp@Ј˜џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаС2@8С16 а pШ аб cмˆ4 PŽТ бˆа pШ аб cмˆ4 PŽТ бвЦ…Hши ˜ ˆH8јpЈЦв‡а pp ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџpи pџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаб cмˆ4 PŽТ бTotal bearers С2ш3С28 аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHHpџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџ ЬаСH2ш$С31.5ƒ С2ш3С031.5 аЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџp@Ј˜џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаС2@8С22.5 а pШ аб cмˆ4 PŽТ бˆа HH ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџH јP Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬа а H ааЬџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџHpи P Ј XА`ИhР!(#џџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџџЬаС СCare must be taken when the shortЉterm characteristics of a measured route are not known. This may be especially significant when the route is small, since the presentation of voiceЉband data traffic may not be very uniform. Over a five minute period 2:1 variations in the shortЉterm voiceЉband data activity level are not unusual events. It might therefore be prudent to repeat any dimensioning exercises which use a DCOA profile, but doubling all the voiceЉband data occupancies, for comparison against the absolute maximum number of channels available when УУallФФ voice activity is allocated 3 bits. If that comparison shows that clipping would be experienced under those conditions then a lower gain setting should be chosen, based on whichever is believed to be the limiting period. ‚У У5ТX ТConclusionФ ФЦЦ С СAn approach to dimensioning DCME systems has been demonstrated, which though not statistically rigorous, is nevertheless capable of giving reasonable estimates of system capabilities, given adequate input data. A number of potential dimensioning problems have been described, and the solutions outlined. These methods have been used successfully in the introduction of DCMEs on a number of routes.