1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T H.248.33TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (01/2005) SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMSInfrastructure of audiovisual services Communication procedures Gateway control protocol: PCM frame spare bit package ITU-T Recommendation H.248.
2、33 ITU-T H-SERIES RECOMMENDATIONS AUDIOVISUAL AND MULTIMEDIA SYSTEMS CHARACTERISTICS OF VISUAL TELEPHONE SYSTEMS H.100H.199 INFRASTRUCTURE OF AUDIOVISUAL SERVICES General H.200H.219 Transmission multiplexing and synchronization H.220H.229 Systems aspects H.230H.239 Communication procedures H.240H.25
3、9 Coding of moving video H.260H.279 Related systems aspects H.280H.299 Systems and terminal equipment for audiovisual services H.300H.349 Directory services architecture for audiovisual and multimedia services H.350H.359 Quality of service architecture for audiovisual and multimedia services H.360H.
4、369 Supplementary services for multimedia H.450H.499 MOBILITY AND COLLABORATION PROCEDURES Overview of Mobility and Collaboration, definitions, protocols and procedures H.500H.509 Mobility for H-Series multimedia systems and services H.510H.519 Mobile multimedia collaboration applications and servic
5、es H.520H.529 Security for mobile multimedia systems and services H.530H.539 Security for mobile multimedia collaboration applications and services H.540H.549 Mobility interworking procedures H.550H.559Mobile multimedia collaboration inter-working procedures H.560H.569 BROADBAND AND TRIPLE-PLAY MULT
6、IMEDIA SERVICES Broadband multimedia services over VDSL H.610H.619 For further details, please refer to the list of ITU-T Recommendations. ITU-T Rec. H.248.33 (01/2005) i ITU-T Recommendation H.248.33 Gateway control protocol: PCM frame spare bit package Summary The H.248 PCM Frame Spare Bit package
7、 provides support for spare bits Siand Sa4-Sa8, which are defined for the ITU-T Rec. G.704 2048 kbit/s basic frame structure. The PCM Frame Spare Bit package may be applied for PCM30 and PCM31 systems. Source ITU-T Recommendation H.248.33 was approved on 8 January 2005 by ITU-T Study Group 16 (2005-
8、2008) under the ITU-T Recommendation A.8 procedure. ii ITU-T Rec. H.248.33 (01/2005) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of
9、ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing 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
10、 for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. 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 prepar
11、ed on a collaborative basis with ISO and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Recommendation may
12、contain certain mandatory provisions (to ensure e.g. interoperability or applicability) and compliance with the Recommendation 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 expre
13、ss requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Prope
14、rty Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. As of the date of approval of this Recommendation, ITU had received notice of inte
15、llectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. ITU 2005 All rights reserved. No part of this p
16、ublication may be reproduced, by any means whatsoever, without the prior written permission of ITU. ITU-T Rec. H.248.33 (01/2005) iii CONTENTS Page 1 Scope 1 2 References. 1 2.1 Normative references 1 2.2 Informative references 1 3 Definitions 1 4 Abbreviations 2 5 PCM systems and E1 operation modes
17、 2 5.1 Background from transmission perspective . 2 5.2 PCM systems for E1. 3 5.3 E1 operation modes 4 5.4 Conclusion for the PCM Frame Spare Bit package 5 6 PCM Frame Spare Bit package. 5 6.1 Properties 5 6.2 Events . 6 6.3 Signals 7 6.4 Statistics 8 6.5 Error code . 8 6.6 Procedures 8 Annex A Spar
18、e bit coding. 9 A.1 Sub-multiframe based codeword coding 9 A.2 Single bit coding. 9 ITU-T Rec. H.248.33 (01/2005) 1 ITU-T Recommendation H.248.33 Gateway control protocol: PCM frame spare bit package 1 Scope This package defines H.248 methods to allow the following functions for the Siand Sa4-Sa8bit
19、s of the 2048 kbit/s basic frame structure defined in ITU-T Rec. G.704: 1) The MGC instructs the MG to monitor and report changes in received spare bit states. 2) The MG reports changes in received spare bits to the MGC. 3) The MGC instructs the MG to change the state of spare bits being sent. In or
20、der to support various applications in an efficient manner, the coding allows changes to be specified either for individual bits or for the 4-bit codewords that occupy a sub-multiframe. Spare Bits are intended for national and international usage according to 2.3.3/G.704. The G.704 scope is still ap
21、plicable for H.248 systems using the H.248.33 PCM Frame Spare Bit package. 2 References The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated
22、were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recomme
23、ndations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation 2.1 Normative references ITU-T Recommendation G.704 (1998), Synchronous frame structures used at 1544, 6312, 2048, 8448 and 44 736 kbit/
24、s hierarchical levels. ITU-T Recommendation H.248.1 (2002), Gateway control protocol: Version 2. 2.2 Informative references ITU-T Recommendation G.705 (2000), Characteristics of plesiochronous digital hierarchy (PDH) equipment functional blocks. ITU-T Recommendation G.711 (1988), Pulse code modulati
25、on (PCM) of voice frequencies. ITU-T Recommendation G.732 (1988), Characteristics of primary PCM multiplex equipment operating at 2048 kbit/s. ITU-T Recommendation G.962 (1993), Access digital section for ISDN primary rate at 2048 kbit/s. 2 ITU-T Rec. H.248.33 (01/2005) 3 Definitions This Recommenda
26、tion defines the following terms: 3.1 PCM3x system: A G.704 E1 frame where there are “3x“ 64-kbit/s channels available for user traffic. Common E1 structures are PCM30, PCM31, or PCM32 systems. 3.2 PCM3xC system: A PCM3x system with an additional Cyclic Redundancy Check procedure according to clause
27、 2.3.3/G.704. Common CRC-protected E1 structures are PCM30C, and PCM31C systems. 4 Abbreviations This Recommendation uses the following abbreviations and symbols: CRC Cyclic Redundancy Check CW Codeword FAS Frame Alignment Signal IC Incoming ID Identifier MF Multiframe MG Media Gateway MGC Media Gat
28、eway Controller NFAS Non-Frame Alignment Signal OG Outgoing PCM Pulse Code Modulation PDH Plesiochronous Digital Hierarchy SaAdditional Spare Bit (ITU-T Rec. G.704) SiSpare Bit reserved for international use (ITU-T Rec. G.704) SB Spare Bit (also abbreviated as “sb“) SMF Sub-Multiframe (e.g., ITU-T R
29、ec. G.704: MFE1= SMF I + SMF II) SSM Synchronization Status Message (ITU-T Rec. G.704) TS Time-Slot 5 PCM systems and E1 operation modes The purpose of this clause is to outline the use of the PCM Frame Spare Bit package in G.704 environments. 5.1 Background from transmission perspective ITU-T Rec.
30、G.704 specifies frame structures for synchronous transmission interfaces. This H.248 Package is exclusively scoping the 2048 kbit/s basic frame structure according to 2.3/G.704. This hierarchy level is traditionally called E1 in ITU-T, or P12 in ITU-T Rec. G.705. Every G.704 frame defines in structu
31、red mode (see below) a number of 64-kbit/s channel time-slots, see clause 5/G.704 (E1 frames carrying 64-kbit/s channels are commonly termed as “channelized E1“). These frame structures were originally developed for the digitization of the transmission infrastructure in fixed telecommunication netwo
32、rks. ITU-T Rec. H.248.33 (01/2005) 3 Thus, the prime scope were PCM signals, which is still reflected in ITU-T Recs G.732 and G.704: Each 64-kbit/s channel time-slot can accommodate, for example, a PCM-encoded voiceband signal conforming to G.711, or data information with a bit rate up to 64-kbit/s.
33、 The term “PCM system“ came into use due to that background and is still common vocabulary, particularly for E1 usage in circuit-switched telephone networks. 5.2 PCM systems for E1 An E1 frame consists of 32 code words called time-slots and are numbered from 0 to 31 (see 5.1.1.2/G.704). This general
34、 structure is often also known as PCM32 system. The abbreviation “PCM“ points out again that in telephone networks the dominant application of individual E1 time-slots is for the PCM-based voice codec G.711. The number “3x“ denotes how many 64-kbit/s channels of the G.704 frame are available for use
35、r traffic, typically PCM encoded traffic. A PCM31 comprises 31 time-slots for user traffic (referred to as channels 1 to 31), and one time-slot primarily for frame synchronization (= E1 TS0, channel 0). A PCM30 comprises 30 time-slots for user traffic (referred to as channels 1 to 15, and 17 to 31),
36、 one time-slot for frame synchronization (channel 0), and one time-slot for signalling traffic (channel 16). The PCM Frame Spare Bit package solely focuses on PCM30 and PCM31 systems; PCM32 and other potential interface types are out of scope (Figure 1). 4 ITU-T Rec. H.248.33 (01/2005) Figure 1/H.24
37、8.33 Scope of the PCM Frame Spare Bit package 5.3 E1 operation modes A PCM system conforms to specific operation modes of a G.704 interface. E1 interfaces may be fundamentally operated either in unstructured mode or in structured mode. Unstructured mode is typically used for cell-, frame-, or packet
38、-switched traffic (e.g., ATM-over-E1 according to ITU-T Rec. G.804), and is out of scope for the PCM Frame Spare Bit package. The structured mode is intended for circuit-switched traffic, and may be further subdivided into modes with or without multiframing. Both are in scope for the PCM Frame Spare
39、 Bit package, but with a slightly different focus due to the different usage of spare bits in these modes. 5.3.1 E1 multiframes and sub-multiframes (SMF) Multiframing is applied where there is a need to provide additional protection against simulation of the frame alignment signal, and/or where ther
40、e is a need for an enhanced error monitoring capability. The structured E1 multiframing mode is realized by introducing a CRC-4 procedure, and is defined in 2.3.3/G.704. ITU-T Rec. H.248.33 (01/2005) 5 In case of structured H.248 MG E1 interfaces operated in multiframing mode, spare bits carried in
41、the four odd-numbered frames of the E1 SMF are in scope for the PCM Frame Spare Bit package, whereas the four even-numbered frames are out of scope. For instance, any G.704 CRC procedures are not considered. NOTE Table 5B/G.704 (E1 CRC-4 multiframe structure): odd numbered frames do carry CRC-4 mult
42、iframing information, which is a prerequisite to define Sacode words per SMF; thus, at least the usage of Sibit signals are forbidden in this mode (setting of Siwould destroy multiframing detection capability of the receiving side). The PCM Frame Spare Bit package may be applied for PCM30C and PCM31
43、C systems. 5.3.2 E1 structure without multiframing The use of structured H.248 MG E1 interfaces without multiframing is characterized by alternating FAS and NFAS patterns in successive E1 frames. Annex A coding is simplified in this case. Since no SMF structure exists, spare bit signals and events d
44、egenerate into binary code words (see A.2). Whereas Saspare bits are carried only in the odd numbered frames, the Sibit is carried in every frame. The PCM Frame Spare Bit package may be applied for PCM30 and PCM31 systems. 5.4 Conclusion for the PCM Frame Spare Bit package This package defines H.248
45、 methods for accessing the Si-bit and the Sa-bits of an E1 frame described previously. NOTE These bits are typically designated for national and international use, specific point-to-point applications, etc. Further applications are, e.g., G.704 E1 frame-based data link protocols, or spare-bit-based
46、protocol procedures for access digital sections for ISDN primary rate at 2048 kbit/s ITU-T Rec. G.962. These spare bits belong to channel 0 in structured E1 frames. Other channel 0 bits or protocol control information are out of scope of this package. This time-slot (channel 0) cannot be used in suc
47、h dedicated E1 operation modes as a bearer channel for user plane traffic, and must remain therefore in the H.248 Null Context. In some applications, it may be possible for a signalling channel to be defined using one or more of the spare bits of this time-slot as a data link, but such operation is
48、outside the scope of this Recommendation. From the H.248 perspective, this channel represents an H.248 TDM Termination; however, it cannot leave the Null Context or be associated with a “regular H.248 call Context“. 6 PCM Frame Spare Bit package Package name: PCM Frame Spare Bit package PackageID: p
49、cmsb (0x0085) Description: This package defines H.248 methods for accessing Si-Bit and Sa4-Sa8Bits of the 2048 kbit/s Basic Frame Structure according to ITU-T Rec. G.704. Spare bit coding is defined in Annex A. Version: 1 Extends: None 6.1 Properties None. 6 ITU-T Rec. H.248.33 (01/2005) 6.2 Events 6.2.1 Reading State of Spare bit SBy Event name: Spare bit SBy is detected as z (see Table 1). NOTE SBy may be G.704 bit Sifor y = 1, or Sayfor y = 4, 5, 8. EventID: sby_z (0x00yz) Description: Identifies Spare bit SBy with value z. Value z represe
