1、 I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n ITU-T Series G TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU Supplement 56 (02/2016) SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS OTN transport of CPRI signals ITU-T G-series Recommendations Supplement
2、 56 ITU-T G-SERIES RECOMMENDATIONS TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS INTERNATIONAL TELEPHONE CONNECTIONS AND CIRCUITS G.100G.199 GENERAL CHARACTERISTICS COMMON TO ALL ANALOGUE CARRIER-TRANSMISSION SYSTEMS G.200G.299 INDIVIDUAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEP
3、HONE SYSTEMS ON METALLIC LINES G.300G.399 GENERAL CHARACTERISTICS OF INTERNATIONAL CARRIER TELEPHONE SYSTEMS ON RADIO-RELAY OR SATELLITE LINKS AND INTERCONNECTION WITH METALLIC LINES G.400G.449 COORDINATION OF RADIOTELEPHONY AND LINE TELEPHONY G.450G.499 TRANSMISSION MEDIA AND OPTICAL SYSTEMS CHARAC
4、TERISTICS G.600G.699 DIGITAL TERMINAL EQUIPMENTS G.700G.799 DIGITAL NETWORKS G.800G.899 DIGITAL SECTIONS AND DIGITAL LINE SYSTEM G.900G.999 MULTIMEDIA QUALITY OF SERVICE AND PERFORMANCE GENERIC AND USER-RELATED ASPECTS G.1000G.1999 TRANSMISSION MEDIA CHARACTERISTICS G.6000G.6999 DATA OVER TRANSPORT
5、GENERIC ASPECTS G.7000G.7999 PACKET OVER TRANSPORT ASPECTS G.8000G.8999 ACCESS NETWORKS G.9000G.9999 For further details, please refer to the list of ITU-T Recommendations. G series Supplement 56 (02/2016) i Supplement 56 to ITU-T G-series Recommendations OTN transport of CPRI signals Summary The na
6、ture of common public radio interface (CPRI) signals is such that they require special consideration when carried as a client signal over the ITU-T G.709 optical transport network (OTN). One consideration is the stringent frequency accuracy requirements for CPRI. Another consideration is that the na
7、tive line coding of the CPRI signals can be transcoded into a more bandwidth efficient coding, which allows the carriage of additional CPRI client signals in some important applications. Supplement 56 to ITU-T G-series Recommendations describes alternatives for mapping and multiplexing CPRI client s
8、ignals into the OTN. This Supplement relates to Recommendations ITU-T G.872, ITU-T G.709/Y.1331, ITU-T G.798 and ITU-T G.959.1. History Edition Recommendation Approval Study Group Unique ID* 1.0 ITU-T G Suppl. 56 2015-07-03 15 11.1002/1000/12576 2.0 ITU-T G Suppl. 56 2016-02-26 15 11.1002/1000/12838
9、 * To access the Recommendation, type the URL http:/handle.itu.int/ in the address field of your web browser, followed by the Recommendations unique ID. For example, http:/handle.itu.int/11.1002/1000/11830-en. ii G series Supplement 56 (02/2016) FOREWORD The International Telecommunication Union (IT
10、U) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and iss
11、uing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these to
12、pics. The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. NOTE In this publication, the expression “
13、Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this publication is voluntary. However, the publication may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and com
14、pliance with the publication is achieved when all of these mandatory provisions are met. The words “shall“ or some other obligatory language such as “must“ and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the publication is re
15、quired of any party. INTELLECTUAL PROPERTY RIGHTSITU draws attention to the possibility that the practice or implementation of this publication may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectu
16、al Property Rights, whether asserted by ITU members or others outside of the publication development process. As of the date of approval of this publication, ITU had received notice of intellectual property, protected by patents, which may be required to implement this publication. However, implemen
17、ters are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2016 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written p
18、ermission of ITU. G series Supplement 56 (02/2016) iii Table of Contents Page 1 Scope . 1 2 References . 1 3 Definitions 1 4 Abbreviations and acronyms 1 5 Conventions 2 6 Introduction . 2 7 Mappings based on normative methods . 3 7.1 Single CPRI signal mapping into ODUk (k = 0, 1, flex(CBR) . 3 7.2
19、 Multiple CPRI client signal mapping using GFP-T . 9 8 Multiple CPRI option 3, 4 or 5 signal mapping into ODU2r . 11 8.1 OPU2r overhead description 11 8.2 OPU2r payload mappings . 13 8.3 PCS receiver . 14 8.4 OTU2r structure 14 8.5 Bit rates and tolerances . 14 G series Supplement 56 (02/2016) 1 Sup
20、plement 56 to ITU-T G-series Recommendations OTN transport of CPRI signals 1 Scope This Supplement describes alternatives for mapping and multiplexing common public radio interface (CPRI) client signals into the optical transport network (OTN). Other viable means of carrying CPRI over OTN are known
21、to exist and this Supplement is intended to give examples only. It is not intended to provide an exhaustive list of alternatives. The alternatives in this Supplement are for various applications and requirements. Some are based on new methods and others are to explain how to use standardized tools f
22、or carrying CPRI over OTN. The mappings in this Supplement include direct mappings for native CPRI client signals and mappings that apply transcoding in order to gain bandwidth efficiency. This Supplement relates to ITU-T G.872, ITU-T G.709, ITU-T G.798 and ITU-T G.959.1. 2 References ITU-T G.709 Re
23、commendation ITU-T G.709/Y.1331 (2012), Interfaces for the optical transport network. ITU-T G.798 Recommendation ITU-T G.798 (2012), Characteristics of optical transport network hierarchy equipment functional blocks. ITU-T G.806 Recommendation ITU-T G.806 (2012), Characteristics of transport equipme
24、nt Description methodology and generic functionality. ITU-T G.872 Recommendation ITU-T G.872 (2012), Architecture of optical transport networks. ITU-T G.959.1 Recommendation ITU-T G.959.1 (2016), Optical transport network physical layer interfaces. ITU-T G.7041 Recommendation ITU-T G.7041/Y.1303 (20
25、16), Generic framing procedure. CPRI CPRI Specification V7.0 (2015), Common public radio interface (CPRI), interface specification. 3 Definitions None. 4 Abbreviations and acronyms This Supplement uses the following abbreviations and acronyms: AIS Alarm Indication Signal AMP Asynchronous Mapping Pro
26、cedure BaFN Basic Frame Number BFP Basic Frame Pointer CBR Constant Bit Rate CID Channel ID CPRI Common Public Radio Interface 2 G series Supplement 56 (02/2016) CSF Client Signal Fail FEC Forward Error Correction GFP-T Transparent Generic Framing Procedure GMP Generic Mapping Procedure HO High Orde
27、r LO Low Order NE Network Element ODU Optical channel Data Unit ODUk Optical channel Data Unit-k ODU2r overclocked Optical channel Data Unit-2 OMFI OPU2r Multiframe Identifier OPU Optical channel Payload Unit OPUk Optical channel Payload Unit-k OTN Optical Transport Network PCS Physical Coding Subla
28、yer PSI Payload Structure Identifier PT Payload Type RE Remote Equipment RRH Remote Radio Head UIpp Unit Intervals peak-to-peak UPI User Payload Identifier 5 Conventions Transmission order: The order of transmission of information in all the figures in this Supplement is first from left to right and
29、 then from top to bottom. Within each byte, the most significant bit is transmitted first. The most significant bit (bit 1) is illustrated at the left in all the figures. 6 Introduction This Supplement first describes methods for mapping CPRI client signals into the OTN that make use of existing ITU
30、-T Recommendations. CPRI signals are treated as a normal constant bit rate (CBR) client for the ITU-T G.709 OTN, but stringent frequency and clock tolerance requirements are specified for CPRI clients. Second, this Supplement describes a method that uses a combination of transcoding and multiplexing
31、 (interleaving) of multiple CPRI clients into an overclocked optical channel data unit-2 (ODU2), called the ODU2r, in order to optimize transport bandwidth efficiency in some important CPRI applications. Note that OTN transport of CPRI is intended for use within an administrative domain. Users of th
32、is Supplement should not assume that the required performance for the CPRI client is met. It is the responsibility of the network operator to determine if the required performance can be met. For example, the OTN network should also be designed in order to meet the applicable symmetry requirements.
33、Considerations for maintaining adequate frequency accuracy for CPRI clients are addressed in the respective clauses. G series Supplement 56 (02/2016) 3 The definition of CPRI replacement signals during fault conditions is for further study for all mappings. 7 Mappings based on normative methods This
34、 clause describes methods for mapping CPRI client signals into ITU-T G.709 payloads using techniques that are currently defined for use with other client signal mappings in ITU-T G.709. The descriptions also describe special considerations that may be needed. NOTE It is the responsibility of the net
35、work operator to determine if the required performance can be met. The noise generated by the OTN would have to be handled by the CPRI system in order to meet the application requirements. This is considered as a complex task according to the current OTN specification. 7.1 Single CPRI signal mapping
36、 into ODUk (k = 0, 1, flex(CBR) CPRI CBR signals (CPRI options 1 to 10) may be transported over an optical channel data unit-k (ODUk) connection. These CBR signals are mapped into a low order (LO) optical channel payload unit-k (OPUk) via the generic mapping procedure (GMP) as specified in clause 17
37、.7 of ITU-T G.709 for CPRI options 1 to 3 and via the bit-synchronous mapping procedure as specified in clause 17.9 of ITU-T G.709 for CPRI options 4 to 10. Two CPRI signals (options 1 and 2) are transported via OPU0, one CPRI signal (option 3) is transported via OPU1 and the remaining CPRI signals
38、(options 4 to 10) are transported via OPUflex. The GMP Cm and Cn (n = 1) values associated with the CPRI options 1 to 3 signals are presented in Tables 7-1a, 7-1b, 7-2a and 7-2b. The use of the “experimental mapping“ payload type (code 0x01) is suggested. Further details are provided below: Simulati
39、on analyses were done for the transport of CPRI option 2, option 3 and option 4 clients over OTN for the following four cases: a) Option 2 client signal ODU0 ODU2 OTU2 ODU2 ODU0 option 2 client signal b) Option 3 client signal ODU1 ODU2 OTU2 ODU2 ODU1 option 3 client signal c) Option 3 client signal
40、 ODU1 OTU1 ODU1 option 3 d) Option 4 client signal ODU2 OTU2 ODU2 option 4 As described by this Supplement, the mappings of the CPRI option 2 client to ODU0 and the CPRI option 3 client to ODU1 are via GMP. The CPRI option 4 client is mapped to ODUflex, and the ODUflex is mapped to ODU2 via GMP. Fin
41、ally, in a) the ODU0 is mapped to ODU2 via GMP and in b) the ODU1 is mapped to ODU2 via asynchronous mapping procedure (AMP). Cases a) and b) have a single mapping of the CPRI client to OTN and one level of OTN multiplexing. Cases c) and d) have a single mapping to OTN and no OTN multiplexing. Simul
42、ations were run for no use of additional phase information for the CPRI client to LO ODU mapper (i.e., Cn with n = 8) and 1 UI of additional phase information for the CPRI client to LO ODU mapper (i.e., Cn with n = 1). The desynchronizer bandwidth for the high order (HO) ODU to LO ODU demappers was
43、300 Hz. The simulation results indicated that, for CPRI client desynchronizer bandwidth in the range 100 to 300 Hz (current OTN client desynchronizers are 300 Hz or, in a few cases, 100 Hz or 200 Hz) RMS frequency offset ranges from approximately 113 ppb to 190 ppb for transport of CPRI option 2 for
44、 case a) and 156 ppb to 317 ppb for transport of CPRI option 3 for case b). In addition, for the same range of desynchronizer bandwidths, RMS frequency offset ranges from approximately 4 G series Supplement 56 (02/2016) 29 ppb to 116 ppb for CPRI option 3 for case c) and 32 ppb to 130 ppb for CPRI o
45、ption 4 for case d). The simulation results also indicated that, for CPRI client desynchronizer bandwidth in the range 100 to 300 Hz, peak-to-peak jitter ranges from approximately 6.9 to 14.2 unit intervals peak-to-peak (UIpp) for transport of CPRI option 2 for case a) and 6.7 to 14.1 UIpp for trans
46、port of CPRI option 3 for case b). In addition, for the same range of desynchronizer bandwidths, peak-to-peak jitter ranges from approximately 0.8 to 7.2 UIpp for CPRI option 3 for case c) and 0.76 to 7.2 UIpp for CPRI option 4 for case d). In order to allow compatibility with OTN transport, CPRI re
47、mote equipment (RE) would need to be designed to tolerate and filter properly at least the noise added by the OTN transport, which is not currently budgeted by CPRI. Additional sources of noise may also exist. The OTN network should also be designed in order to meet the applicable CPRI stringent sym
48、metry requirements; this is something that has not been studied. Interworking between OTN and the CPRI RE, in terms of jitter and wander, is still unknown and has to be considered. The CPRI replacement signal is for further study. Table 7-1a Cm (m = 8) for su1.238G clients into OPU0 CPRI client sign
49、al Nominal bit rate (kbit/s) Bit rate tolerance (ppm) Floor C8,min Minimum c8 Nominal c8 Maximum c8 Ceiling C8,max Option 1 614 400 100 7552 7552.674 7 553.580 7554.487 7555 Option 2 1 228 800 100 15105 15105.348 15107.160 15108.973 15109 Table 7-1b Cn (n = 8 or 1) for su1.238G clients into OPU0 CPRI client signal Nominal bit rate (kbit/s) Bit rate tolerance (ppm) Floor C8,min Minimum c8 Nominal c8 Maximum c8 Ceiling C8,max
