1、 AMERICAN NATIONAL STANDARD FOR TELECOMMUNICATIONS ATIS-0900105.03.2013 SYNCHRONOUS OPTICAL NETWORK (SONET) JITTER AND WANDER AT NETWORK AND EQUIPMENT INTERFACES As a leading technology and solutions development organization, ATIS brings together the top global ICT companies to advance the industrys
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11、sclaimer specific jitter generation requirements for individual network elements are in Table A.9. NOTE 2 - At the lower (high-pass) cutoff frequency F1or F2, the measurement filter is a first-order filter, which has a roll-off of 20 dB/decade. At the upper (low-pass) cutoff frequency F3, the measur
12、ement filter has a maximally-flat Butterworth characteristic and a roll-off of 60 dB/decade. NOTE 3 - For OC-192, the effect of dispersion and non-linearities on the eye opening and on the choice of this value is for further study. NOTE 4 The OC-768 (STM-256) values were taken from ITU-T G.825 Amend
13、ment 1. 6 Jitter on Payload Signals This clause provides specifications for jitter on payload signals from SONET networks due to mapping and pointer adjustments. The jitter specifications for DS1 and DS3 signals were developed based upon hypothetical SONET island network models and respective jitter
14、 budgets (Annex B for DS1 and Annex D for DS3), and the SONET timing short-term stability characteristics (in ATIS-0900101). More information on the effects of SONET on payload jitter can be found in T1.TR.17-1993. In addition, Table 2 lists the cutoff frequencies of the filters specified for use in
15、 the measurements described in this clause. Table 2 - SONET payload jitter measurement filter characteristics DSn level Lower cut-off frequencyNote 1(Hz) Minimum upper cut-off frequencyNote 2(kHz) DS1 10 40DS1A 20 100DS2 10 60 DS3 10 400NOTE 1 - At the lower (high-pass) cutoff frequency the measurem
16、ent filter is a first-order filter, which has a roll-off of 20 dB/decade. NOTE 2 - At the upper (low-pass) cutoff frequency the measurement filter is a first-order filter for DS1, DS2 and DS3, and has a maximally-flat Butterworth characteristic and a roll-off of 60 dB/decade for DS1A. ATIS-0900105.0
17、3.2013 6 6.1 Jitter Caused by Mapping 6.1.1 VT Level Payloads These requirements are specified to control jitter generated in the VT mapping process. The mapping jitter specifications for DS1 payloads when using the asynchronous mapping are given below in 6.1.1.1. For other VT level payloads when us
18、ing the asynchronous mapping, the stuffing mechanism that generates the C-bits (justification control bits) shall be chosen such that, given a desynchronizer whose characteristics are that of a second-order low-pass filter with the 3 dB bandwidths specified in Table 3, the output jitter shall be les
19、s than 1.0 UIppand 0.3 UIrms. The previous requirement assumes the following: There is no jitter or wander on the payload signal at the input to the SONET network; and There is no pointer adjustment activity. Table 3 - VT assumed desynchronizer bandwidths VT payload signal Desynchronizer bandwidth (
20、Hz) DS1A 300 DS2 5006.1.1.1 DS1 Payloads DS1 mapping jitter is specified such that the allocation allowed for asynchronous and SONET mapping jitter described in Annex B can be achieved. DS1 mapping jitter is the jitter on a DS1 signal caused by the process of mapping the DS1 payload into a VT1.5 SPE
21、 and then desynchronizing back to a DS1. The jitter on the DS1 payload signals out of a SONET island shall be less than 0.7 UIpp, given no jitter or wander on the DS1 payload as it enters the network and no pointer adjustment activity in the SONET network. To ensure synchronizer-desynchronizer inter
22、operability, the DS1 mapping mechanism shall meet the following requirement: The stuffing mechanism that generates the C-bits (justification control bits) shall be implemented such that, given a desynchronizer, the characteristics of which are that of the transfer mask given in Figure 1, the mapping
23、 jitter shall be no more than 0.7 UIpp. In addition, to limit jitter accumulation through tandem SONET islands, the following requirement applies to the DS1 desynchronizer: In the process of extracting the DS1 from the VT1.5 SPE, the mapping jitter shall be filtered by a desynchronizer whose transfe
24、r characteristic is under the mask given in Figure 1. ATIS-0900105.03.2013 7 0.1 40Jitter transfer (dB) Frequency (Hz) Slope = -20 dB/decade Figure 1 - Jitter transfer mask for DS1 and DS3 desynchronizers 6.1.2 STS Level Payloads 6.1.2.1 DS3 Payloads DS3 mapping jitter is specified such that the all
25、ocation allowed for asynchronous and SONET mapping jitter described in Annex D can be achieved. The jitter on DS3 payload signals out of a SONET island shall be less than 0.4 UIpp, given no pointer adjustment activity in the network, and no jitter or wander on the DS3 payload signal as it enters the
26、 network. To ensure synchronizer/desynchronizer interoperability, the DS3 mapping mechanism shall meet the following requirement: The stuffing mechanism that generates the C-bits (justification control bits) shall be implemented such that, given a desynchronizer the characteristics of which are that
27、 of the transfer mask given in Figure 1, the mapping jitter shall be no more than 0.4 UIpp. In addition, to limit jitter accumulation through tandem SONET islands, the following requirement applies to the DS3 desynchronizer: In the process of extracting the DS3 from the STS-1 SPE, the mapping jitter
28、 shall be filtered by a desynchronizer whose transfer characteristic is under the mask given in Figure 1. 6.2 Jitter Caused by Pointer Adjustments Pointer adjustments are the mechanism within SONET to compensate for frequency and phase differences between SPEs and outgoing SONET frames. Because they
29、 are byte wide adjustments, and ATIS-0900105.03.2013 8 because they can occur randomly, they can cause significant amounts of payload signal jitter. It is therefore necessary to control the jitter on payload signals that is due to pointer adjustments. SONET pointer adjustment activity within a netwo
30、rk is a function of the synchronization characteristics of that network. Refer to ATIS-0900101 for information on synchronization specifications. Pointer adjustment activity can range from randomly spaced individual pointer adjustments due to clock noise, to pointer adjustment bursts due to clock no
31、ise or clock rearrangements and their alignment with buffer fills, and periodic pointer adjustments due to synchronization failures. Stratum 3 clock characteristics in accordance with ATIS-0900101 were used in the development of these specifications. Because pointer adjustment statistics can vary so
32、 widely, it is difficult to specify jitter predictably. A solution to this problem is to develop a set of test sequences that adequately simulates network pointer adjustment activity. These sequences correspond to isolated single pointer adjustments, pointer adjustment bursts, and periodic pointer a
33、djustments. Associated with each test sequence is an output payload jitter specification. Jitter due to single pointer adjustments is specified to control jitter accumulation across cascaded SONET islands. Jitter due to pointer adjustment bursts and due to synchronization failures are both specified
34、 to control the jitter generated in a single SONET island. The test sequences are provided in Figures 2 through 8. Table 9 and its general notes are an integral part of the sequence descriptions. Annex G provides a test methodology for measuring payload signal jitter due to pointer adjustments. 6.2.
35、1 Single Pointer Adjustments The jitter on payload signals out of SONET networks shall be less than A1 from Table 4 when the pointer adjustment test sequence described in Figure 2 is applied to the final PTE and no jitter is applied at the input to the SONET network. Table 4 - Single pointer adjustm
36、ent jitter specifications Payload signal A1 Single pointer adjustment (UIpp) DS1 A0Note 1+ 0.6 DS1A Under study DS3 A0Note 1+ 0.30 NOTE 1 - A0 is the amount of jitter generated by the island that is solely due to DSn mapping. For measurement methodology considerations and information on mapping jitt
37、er, refer to clause 6.1.1.1 and G.3.5 in Annex G for DS1, and 6.1.2.1 and G.3.6 for DS3. ATIS-0900105.03.2013 9 Pointer adjustment Initialization (see Annex G.3.3) Cool down Measurement period 30 s TimeFigure 2 - Single pointer adjustment test sequence 6.2.2 Pointer Adjustment Bursts The jitter on p
38、ayload signals out of SONET networks shall be less than A2 from Table 5 when the pointer adjustment test sequence described in Figure 3 is applied to the final PTE and no jitter is applied at the input to the SONET network. Table 5 - Pointer adjustment burst jitter specifications Payload signal A2 P
39、ointer adjustment burst (UIpp) DS3 1.3Note 1NOTE 1 - This number is based on 0.4 (mapping) + 3 0.3 (triple pointer adjustment burst). Pointer adjustment Initialization (see Annex G.3.3) Cool down Measurement period 30 s 30 st tt tNote 1Note 1: Refer to Table 9 for the value for parameter t.TimeFigur
40、e 3 - Pointer adjustment burst test sequence ATIS-0900105.03.2013 10 6.2.3 Phase Transient Pointer Adjustment Bursts The jitter on payload signals out of SONET networks shall be less than A3 from Table 6 when the pointer adjustment test sequence described in Figure 4 is applied to the final PTE and
41、no jitter is applied at the input to the SONET network. Table 6 - Phase transient pointer adjustment burst jitter specifications Payload signal A3 Phase transient pointer adjustment burst (UIpp) DS3 1.2 Initialization (see Annex G.3.3) Cool down Measurement period Time 30 s 30 s 0.25 s 0.5 s Pointer
42、 adjustment burstPointer adjustment Figure 4 - Phase transient pointer adjustment burst test sequence ATIS-0900105.03.2013 11 6.2.4 Periodic Pointer Adjustments 6.2.4.1 With No Added or Canceled Pointer Adjustments The jitter on payload signals out of a SONET network shall be less than A4 from Table
43、 7 when the pointer adjustment test sequences described in Figures 5(b) and 6(b) for STS pointer adjustments,6and Figures 7(b) and 8(b) for VT1.5 pointer adjustments7, without added or canceled pointer adjustments, are applied to the final PTE, and no jitter is applied at the input to the SONET netw
44、ork. Table 7 - Periodic pointer adjustment jitter specifications (without added or canceled pointer adjustments) Payload signal A4 Periodic pointer adjustments (UIpp) DS1 1.3Note 1DS1A Under study DS3 1.0Note 2NOTE 1 - This number is based on 0.7 (mapping) + 0.6 (synchronization failure). NOTE 2 - T
45、his number is based on 0.4 (mapping + 0.6 (synchronization failure). 6.2.4.2 With Added & Canceled Pointer Adjustments The jitter on payload signals out of a SONET network shall be less than A5 from Table 8 when the pointer adjustment test sequences described in Figures 5(c), 5(d), 6(c), and 6(d) fo
46、r STS pointer adjustments and Figures 7(c), 7(d), 8(c), and 8(d) for VT1.5 pointer adjustments, are applied to the final PTE and no jitter is applied at the input to the SONET network. Table 8 - Periodic pointer adjustment jitter specifications (with added or canceled pointer adjustments) Payload si
47、gnal A5 Periodic pointer adjustments with added or canceled pointer adjustments (UIpp) DS1 1.9Note 1DS1A Under study DS3 1.3Note 2NOTE 1 - This number is based on 0.7 (mapping) + 0.6 (added or canceled single pointer adjustment) + 0.6 (synchronization failure). NOTE 2 - This number is based on 0.4 (
48、mapping) + 0.3 (added or canceled single pointer adjustment) + 0.6 (synchronization failure). _ 6The 87-3 pattern depicted in Figure 5(b) is expected to result from pointer processor implementations that use fixed adjustment thresholds. The continuous pattern depicted in Figure 6(b) results from poi
49、nter processor implementations that use variable adjustment thresholds. Although the sequences defined in this standard consider these two implementations, no judgment is made here on any particular pointer processor implementation. 7The 26-1 pattern depicted in Figure 7(b) is expected to result from pointer processor implementations that use fixed adjustment thresholds. The continuous VT1.5 patterns depicted in Figure 8(b) results from pointer processor implementations that use variable adjustment thresholds. Although the sequences defined in this
