WPCL 2BJ|x ` H   x|@  6'6' 8.HRecommendation G.738 (CHARACTERISTICS OF PRIMARY PCM MULTIPLEX EQUIPMENT )OPERATING AT 2048 KBIT/S AND OFFERING SYNCHRONOUS +DIGITAL ACCESS AT 320 KBIT/S AND/OR 64 KBIT/S 9(Melbourne, 1988) A   HThis Recommendation gives the characteristics of a PCM multiplex equipment operating at 2048kbit/s and providing one or several of the following internal digital access options: H bidirectional synchronous 64 kbit/s channels (see Figure1a/G.738; H unidirectional synchronous 320 kbit/s channels (see Figure1b/G.738.  X HThe 320 kbit/s channel is based on the allocation of 5x64kbit/s time slots, e.g., for setting up soundprogramme circuits according to RecommendationsJ.43 and J.44. HBecause these circuits are specified as unidirectional, the equipment for insertion/extraction has to be separated as shown in Figures1b/G.738. 1.HGeneral characteristics 1.1HFundamental characteristics for voice channel encoding HThe encoding law used is the Alaw as specified in RecommendationG.711. The sampling rate, load capacity and the code are also specified in that Recommendation. HThe number of quantized values is 256. Note The inversion of bits 2, 4, 6 and 8 is covered by the encoding law and is applicable only to voice channel time slots. 1.2HBit rate HThe nominal bit rate is 2048 kbit/s. The tolerance on this rate is +Ġ50 parts per million (ppm). 1.3HTiming signal HIt should be possible to derive the transmit timing signal from any of the following: Ha)h  from the received 2084 kbit/s signal; Hb)  from an external source at 2048 kHz (see 5); Hc)  from an internal oscillator. Note The provision of a timing signal output, available for the purpose of synchronizing other equipments, is an option that might be required depending upon national synchronization arrangements. 1.4HTypes of access Ha)h  access for bidirectional synchronous 64 kbit/s channels (see Figure1a/G.738); Hb)h  access for unidirectional synchronous 320 kbit/s channels (see Figure 1b/G.738). Note The synchronous insertion of a digital sound programme signal into a 320 kbit/s channel requires the internal regeneration of a timing signal T synchronized by the 2048 kbit/s signal I1. the timing signal is used for synchronizing the sampling frequency of the analogue/digital converters producing the digital sound programme signal. 2.HFrame structure and use of derived channel time slot 2.1HFrame structure of 2048 kbit/s signal HRefer to 2.3 of Recommendation G.704. Bit 1 of the frame should be used in accordance with 2.3.3/6.706, i.e., for a CRC check bit procedure. 2.2HUse of derived channel time slots 2.2.1HTelephone channels HIt should be possible to assign channel time slots 1 to 15 and 17 to 31 to 30 telephone channels numbered from 1 to 30. 2.2.2H64 kbit/s access HThe number of accessible channel time slots should be at least four and the equipment shall allow access to any of channel time slots 1 to 15 and 17 to 31. Note Equipment exists which provides access to at least four channel time slots in the following order to priority:  H HH6 22 14 30 2 18 10 26 4 20 12 28 8 24 5 21 13 29 1 17 9 25 3 19 11 27 7 23 15 31.  `  2.2.3H320 kbit/s access   HThe time slot allocation for digital channels with bit rate at 320kbit/s is given in the following table: h#   h#  320 kbit/s channels (Note 1)  DSP  h# ACCESS  h#  A  B  C  D  E  F  POINTS  h# h#  1 2  6 7  11 12  17 18  22 23  27 28  I3, T, E3  h#  3 4  8 9  13  19  24  29  Figure  h#  5  10  14 15  20 21  25 26  30 31  1b/G.738  h#     Note 1 The six possible 320 kbit/s channels in a 2048 kbit/s stream are numbered A to F. Preferably the channel pairs AB, CD, and EF should be used for stereophonic transmission.   Note 2 If the channel time slot 16 which is assigned to signalling as covered in 5 below is not needed for signalling, it may be used for purposes other than , a voice channel encoded within the PCM multiplex equipment. Ha)h  Bidirectional synchronous insertion/extraction of 64 kbit/s data channels Hb)h  Unidirectional synchronous insertion and extraction of digital soundprogramme (DSP) into/out of a 320 kbit/s channel HI,E: insertion side; extraction side HI1,E1: 2048 kbit/s interface HI2,E2 64 kbit/s interface HI3,E3: synchronous; digital sound programme signal access HT: timing signal JFIGURE 1/G.738 Q 9PCM multiplex equipment operating at 2048 kbit/să 6and offering access to digital soundprogramme signalsă ;and/or to synchronous 64 kbit/s data channelsă 3.HFrame alignment and CRC procedures H(An illustration of the procedure is given in Figure2/G.706.) 3.1HLoss of frame alignment HRefer to 4.1.1. of Recommendation G.706. 3.2HRecovery of frame alignment HRefer to 4.1.2 of Recommendation G.706. 3.3HCRC multiframe alignment in TSO HRefer to 4.2 of Recommendation G.706. 3.4HCRC bit monitoring HRefer to 4.3 of Recommendation G.706. 4.HFault conditions and consequent actions 4.1HFault conditions HThe PMC multiplex equipment should detect the following conditions: 4.1.1HFailure of power supply. 4.1.2HFailure of codec (except when using single channel codecs). HAs a minimum requirement, this fault condition should be recognized when for at least one signal level in the range 21 to 6dBmO, the signalto quantizing noise ration performance of the local codec is 18 dB or more below the level recommended in RecommendationG.712. 4.1.3HLoss of incoming signals at the 64 kbit/s and 320 kbit/s tributary input ports. Note 1 This detection is not mandatory when contradirectional interfaces are used. Note 2 The detection of this fault condition is not mandatory for channel time slot 16 when channel associated signalling is used and the signalling multiplex equipment is situated within a few metres of the PCM multiplex equipment. 4.1.4HLoss of the incoming signal at 2048 kbit/s. Note 1 The detection of this fault condition is required only when it does not result in an indication of loss of frame alignment. Note 2 Where separate circuits are used for the digital signal and the timing signal, the loss of either or both should constitute loss of the incoming signal. 4.1.5HLoss of frame alignment. 4.1.6HExcessive bit error ratio detected by monitoring the frame alignment signal.  x 4.1.6.1 With a random bit error ratio of < 10é4, the probability of activating the indication of fault condition in a few seconds should be less than 10é6. HWith a random bit error ratio of > 10é3, the probability of activating the indication of fault condition in a few seconds should be higher than 0.95. 4.1.6.2 With a random bit error ratio of > 10é3, the probability of deactivating the indication of fault condition in a few seconds should be almost0. HWith a random bit error ratio of < 10é4, the probability of deactivating the , indication of fault condition in a few seconds should be higher than 0.95. Note The activating and deactivating period specified as "a few seconds" is intended to be in the order of 4 to 5 seconds. 4.1.7HAlarm indication received from the remote PCM multiplex equipment (see 4.2.3). 4.2HConsequent actions HFurther to the detection of a fault condition, appropriate actions should be taken as specified in Table1/G.738. The consequent actions are as follows: 4.2.1HService alarm indication generated to signify that the service provided by the PCM multiplex is no longer available. This indication should be forwarded at least to the switching and/or signalling multiplex equipment depending upon the arrangements provided. The indication should be given as soon as possible and not later than 2ms after detection of the relevant fault condition. HThis specification, taking into account the specification given in 2.5, is equivalent to recommending that the average time to detect a loss of frame alignment or a loss of the incoming 2048kbit/s signal and to give the relevant indication should not be greater than 3ms. HWhen using common channel signalling the indication should be forwarded to the switching equipment by means of a separate interface on the PCM multiplex equipment. 4.2.2HPrompt maintenance alarm indication generated to signify that performance is below acceptable standards and maintenance attention is required locally. When the AIS (see general note below to 4.2) at 2048kbit/s input is detected the prompt maintenance alarm indication, associated with loss of frame alignment (see 4.1.5) and excessive error rate (see 4.1.6), should be inhibited, while the rest of the consequent actions are in accordance with those associated in Table1/G.738 with the two fault conditions. Note The location and provision of any visual and/or audible alarm activated by the alarm indications given in 4.2.1 and 4.2.2, is left to the discretion of each administration. 4.2.3HAlarm indication to the remote end transmitted by changing bit 3 of channel time slot 0 from the state 0 to the state 1 in those frames not containing the frame alignment signal. This should be effected as soon as possible. 4.2.4HTransmission suppressed at the analogue voicefrequency outputs 4.2.5HAIS applied to all 64 kbit/s and 320 kbit/s outputs (see general note below to 4.2). For 64 kbit/s outputs this action should be taken as soon as possible and not later than 2ms after the detection of the fault condition. 4.2.6HAIS applied to relevant time slots in the composite 2048kbit/s output signal (if suspension of incoming 64 kbit/s and 320 kbit/s signals is provided). Notes to 4.2 Note 1 The equivalent binary content of the alarm indication signal (AIS) is a continuous stream of binary 1s. The strategy for detecting the presence of the AIS should be such that with a high probability the AIS is detectable even in the presence of random errors having a mean error rate of 1 in 103. Nevertheless, a signal in which all the binary elements, with the exception of the frame alignment signal, are in the state 1, should not be taken as an AIS. Note 2 All timing requirements quoted apply equally to restoration, subsequent to the fault condition clearing. 5.HSignalling HText as in Recommendation G.732. 6.HInterfaces 6.1HAudio frequency interface HThe analogue audio frequency interfaces should be in accordance with RecommendationsG.712, G.713, G.714 and G.715. 6.2HDigital interfaces HThe digital interfaces at 2048 kbit/s should be in accordance with Recommendation G.703. HThe digital interfaces at 64 kbit/s should be of either the codirectional or the contradirectional type specified in RecommendationG.703. The specification for 64 kbit/s interfaces are not mandatory for channel associated signalling. The interface for external synchronization of the transmitting timing signal should be in accordance with RecommendationG.703. HThe need to define a digital interface operating at 320 kbit/s is under study. Note 1 It should be noted that, according to the principle of minimizing the number of different types of interfaces, the information rate of 320kbit/s will be offered to customers at the user/network interface level using the 2048kbit/s interface as defined in Recommendation I.431 and RecommendationG.703. Note 2 In the case of the 64 kbit/s codirectional interface, the design of the input ports should take into account the need to provide octet alignment, to allow controlled slips when the tributary timing and that of the multiplexer timing source are plesiochronous, and to absorb jitter and wander up to the limits given in RecommendationG.823.   O H&'H&' TABLE 1/G.738 U 2Fault conditions and consequent actions for the PCM multiplex equipmentă U       Equipment Fault  Consequent actions (see 3.2)     part  conditions      (see 4.1)  Service  Prompt  Alarm  Transmission  AIS applied  AIS applied       alarm  maintenance  indication  suppressed at  to 64 kbit/s  to the       indication  alarm  remote end  the analogue  and 320 kbit/s  relevant time       generated  indication  transmitted  voice  outputs  slot of the          frequency   2048 kbit/s          outputs   composite            signal         Failure of  Yes  Yes  Yes (if  Yes (if  Yes (if  Yes (if     Multiplexer  power supply    practicable)  practicable)  practicable)  practicable)     and  ,Ԍ   demultiplexer  Failure of  Yes  Yes  Yes  Yes        codec              Multiplexer  Loss of   Yes     Yes     only  incoming            signal at            64 kbit/s            and/or            320 kbit/s            inputs (see            note under            4.1.3)            ITABLE 1/G.738 (continued)       Equipment Fault  Consequent actions (see 3.2)     part  conditions      (see  4.1)  Service  Prompt  Alarm  Transmission  AIS applied  AIS applied       alarm  maintenance  indication  suppressed at  to 64 kbit/s  to the       indication  alarm  remote end  the analogue  and 320 kbit/s  relevant time       generated  indication  transmitted  voice  outputs  slot of the          frequency   2048 kbit/s          outputs   composite            signal         Loss of  Yes  Yes  Yes  Yes  Yes       incoming            signal at            2048 kbit/s                Loss of frame  Yes  Yes (see  Yes  Yes  Yes       alignment    4.2.2)          (see Note 2            4.2/G.706)           Demultiplexer     only  Error ratio  Yes  Yes (see  Yes  Yes  Yes       1 103   4.2.2)          alignment            signal                Alarm  Yes           indication            received from            the remote end             `  6'6'   Note to Table 1/G.738 A "Yes" in the table signifies that an action should be taken as a consequence of the relevant fault condition. An open space in the table signifies that the relevant action should not be taken as a consequence of the relevant fault condition, if this condition is the only one present. If more than one fault condition is simultaneously present, the relevant action should be taken if, for at least one of the conditions, a "Yes" is defined in relation to this action. 7.HJitter 7.1HJitter at 2048 kbit/s output (see Figure 2/G.823) 7.1.1HIn the case where the transmitting timing signal is derived from an internal oscillator, the peaktopeak jitter at the 2048 kbit/s output should not exceed 0.05 UI when it is measured within the frequency range from f1Ġ=20Hz to f4 = 100 kHz. 7.1.2HIn the case where the transmitting timing signal is derived from an external source having no jitter, the peaktopeak jitter at the 2048kbit/s output should not exceed 0.05UI when it is measured within the frequency range from f1Ġ=20Hz to f4Ġ=100kHz. 7.1.3HIn the case where the transmitting timing signal is derived from the incoming 2048kbit/s signal having no jitter, the peaktopeak jitter at the 2048kbit/s output should not exceed 0.10UI when it is measured within the frequency range from f1Ġ=20Hz to f4 = 100 kHz. The equivalent binary content of the test signal applied at the 2048kbit/s input shall be a pseudorandom bit sequence of length 215ĩ1 as specified in Recommendation0.151.  ԌNote It may be necessary to include a frame alignment signal in the test signal to enable the measurement to be carried out. 7.2HJitter at tributary outputs 7.2.1HJitter at 64 kbit/s output HIn the case where the incoming 2048 kbit/s signal has no jitter, the peaktopeak jitter at the 64 kbit/s output should not exceed 0.025UI when it is measured within the frequency range from f1 = 20Hz to f4Ġ=10kHz. The equivalent binary content of the test signal applied to the 2048kbit/s input shall be a pseudorandom bit sequence of length 215ĩ1 as specified in Recommendation0.151. Note In order to carry out this measurement without invoking AIS at the 64kbit/s output it will normally be necessary to include a frame alignment signal in the test signal. 7.2.2HJitter at 320 kbit/s output HSince the physical and electrical characteristics of a 320 kbit/s interface are identical to those of the 2048 kbit/s interface, the specification of this parameter is the same as that given in 7.1.3 above. 7.3HJitter transfer functions 7.3.1HThe jitter transfer function between the 2048 kbit/s external synchronization signal and the 2048kbit/s output signal should not exceed the gain/frequency limits given in Figure2/G.738. The 2048kHz signal shall be modulated with sinusoidal jitter. HSome administrations require that equipment is fitted with jitter reducers. In this case, the jitter transfer function should not exceed the gain/frequency limits given in Figure3/G.738. 7.3.2HIn the case where the transmitting timing is derived from the incoming signal the jitter transfer function between the 2048kbit/s input and the 2048kbit/s output shall be as specified in 7.3.1. Note 1 The 2048kbit/s test signal shall be modulated by sinusoidal jitter. The equivalent binary content of the test signal shall be 1000. Note 2 It may be necessary to include a frame alignment signal in the test signal to enable the measurement to be carried out. Note 1 The frequency f0 should be less than 20Hz and as low as possible (e.g., 10Hz), taking into account the limitations of measuring equipment. Note 2 To achieve accurate measurements, the use of a selective method is recommended with a bandwidth sufficiently small referred to the relevant measurement frequency but not wider that 40Hz. Note 3 For interfaces within national boundaries, this characteristic may be used. JFIGURE 2/G.738 Note 1 The frequency f0 should be less than 20 Hz and as low as possible (e.g., 10Hz), taking into account the limitations of measuring equipment. Note 2 To achieve accurate measurement, the use of a selective method is recommended with a bandwidth sufficiently small referred to the relevant measurement frequency but not wider than 40Hz. JFIGURE 3/G.738 7.3.3HThe jitter transfer function between the 2048kbit/s input and the , 64kbit/s output should not exceed 29.6dB when measured over the frequency range f0 to 10kHz. The frequency f0 should be less than 20Hz and as low as possible (e.g., 10Hz), taking into account the limitations of measuring equipment. Note 1 The 2048 kbit/s test signal shall be modulated by sinusoidal jitter. The equivalent binary content of the test signal shall be 1000. Note 2 In order to carry out this measurement without invoking AIS at the 64kbit/s output it will normally be necessary to include a frame alignment signal in the test signal. Note 3 The jitter reduction of 1/32 due to demultiplexing is equivalent to 30.1dB. 7.3.4HSince the physical and electrical characteristics of a 320kbit/s interface are identical to those of 2048kbit/s interface, the jitter transfer function between 2048kbit/s input and 320kbit/s output is the same as that given in 7.3.1 and 7.3.2 above.