1、 ITU-T RECflN*G.L73 93 m 4862591 0589507 878 m INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU G.173 (03193) TRANSMISSION SYSTEMS AND MEDIA TRANSMISSION PLAN ASPECTS OF SPECIAL CIRCUITS AND CONNECTIONS USING THE INTERNATIONAL TELEPHONE CONNECTION NETWORK T
2、RANSMISSION PLANNING ASPECTS OF THE SPEECH SERVICE IN DIGITAL PUBLIC LAND MOBILE NETWORKS ITU-T Recommendation G.173 (Previously “CCITT Recommendation”) ITU-T RECMN*G=L73 93 m 4862593 0589508 704 m FOREWORD The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the Internat
3、ional Telecom- munication Union. The 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 Conference (WTSC), which meets every
4、four years, established the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics. ITU-T Recommendation G. 173 was prepared by the ITU-T Study Group XII (1 988- 1993) and was approved by the WTSC (Helsinki, March 1-12, 1993). NOTES 1 As a consequenc
5、e of a reform process within the International Telecommunication Union (ITU), the CCITT ceased to exist as of 28 February 1993. In its place, the ITU Telecommunication Standardization Sector (ITU-T) was created as of 1 March 1993. Similarly, in this reform process, the CCIR and the IFRB have been re
6、placed by the Radiocommunication Sector. In order not to delay publication of this Recommendation, no change has been made in the text to references containing the acronyms “CCIT, CCIR or IFRB“ or their associated entities such as Plenary Assembly, Secretariat, etc. Future editions of this Recommend
7、ation will contain the proper terminology related to the new ITU structure. 2 telecommunication administration and a recognized operating agency. In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a O ITU 1994 All rights reserved. No part of this publica
8、tion may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. CONTENTS i Introduction 2 Transmission performance . 2 .i Loudness ratings . 2.2 Stability . 2.3 Propagation time . 2.4 Echo con
9、trol 2.5 Quantizing distortion 2.6 Clipping 2.7 Noise contrast . 2.8 Other requirements . Annex A - Definitions and detailed transmission aspects A.1 Definitions A.2 Detailed model of the digital land mobile system . A.3 Detailed transmission performance . References Annex B - Examples of interconne
10、ctions . B.l Connections between MSs B.2 Connections from the PLMN to PSTNASDN B.3 Connections from the PSTNASDN to PLMN Recommendation 6.173 (03/93) Page 1 1 2 2 2 2 3 3 3 3 4 4 5 7 13 13 14 14 14 1 ITU-T RECflNxG-173 93 4862571 0587510 362 Recommendation 6.173 TRANSMISSION PLANNING ASPECTS OF THE
11、SPEECH SERVICE IN DIGITAL PUBLIC LAND MOBILE NETWORKS (Helsinki, 1993) 1 Introduction The purpose of this Recommendation is to describe the special transmission planning aspects of digital public land mobile networks (PLMN). This Recommendation is limited to PLMN implemented with terrestrial-based f
12、acilities only. Mobile networks that include satellite links are not covered by this Recommendation, but are under separate consideration. In addition, this Recommendation provides guidelines and advice to Administrations and recognized network operators as to the kind of precautions, measures and m
13、inimum requirements which are needed for a successful interworking of digital public land mobile networks with the national and intemational PSTN and ISDN. Transmission planning aspects of analogue public land mobile networks are not covered in this Recommendation. The performance objectives of digi
14、tal public land mobile networks are to reach a quality as close as possible to CCITT Recommendations. Due to the technical and economical factors of such mobile networks a full compliance with the general characteristics of international telephone connections and circuits recommended by CCIT is not
15、guaranteed on all connections. The interworking between a public land mobile network and the PSTNASDN, especially the signalling system between both networks is described in Recommendation Q.70. A summary of transmission requirements for digitai public land mobile systems is presented below. Annex A
16、 provides a more complete discussion of definitions and factors which my prevent full compliance with CCITT Recommendations. Annex B gives examples of PLMN and ISDNPSTN interconnections and configurations, Supplement No. 32 (to this Recommendation) provides information on characteristics of specific
17、 systems. 2 Transmission performance A model of a connection between a PLMN and the PSTNDSDN is shown in Figure 1. A more detailed model of PLMN and the relevant interfaces are described in Annex A. II - I In PLMN - Ici I I Acoustic Interface x interiace I NCP FIGURE lK3.173 Connection between a PLM
18、N and PSTNiSDN Reeommendation 6.173 (03D3) 1 ITU-T RECMN*G-273 93 4862593 0589521 2T9 SLR The overall transmission performance of a connection from the PLMN to the PSTNASDN can be considered as a summation of the effects of: Short-term objectives Long-term objectives 7 dB to 9 dB 8 dB - - the audio
19、part between the acoustic interface and interface X; the speech transcoder part including the effects of radio transmission and speech processing between interface X and the network connection point (NCP), see A. 1.5; the overall characteristics of the connection between the NCP and the other user.
20、- RLR There is not only a linear addition of these effects but there is also an influence from different parts of the connection on the performance of the speech transcoder and other speech processing devices. 1 dB to 3 dB 2 dB However, in several cases the main determining factors are the character
21、istics of the audio part when the additional call path in the PLMN is digital. Where possible, the transmission performance is specified between the acoustic interface and interface X. The transmission aspects of the whole digital mobile system depend on the technical design and may be different fro
22、m network operator to network operator. To control the end-to-end transmission quality recommended by CCIT the requirements given below should be met by the PLMN. 2.1 Loudness ratings The recommended values for the loudness ratings are: These values are directly applicable to the case of a mobile st
23、ation operating in a conventional non-mobile noise environment. Studies have shown that in a PLMN noise environment, speech levels are likely to be higher. Hence, in order to avoid clipping in the speech transcoder it may be necessary to increase the value of the SLR. The loudness rating values shou
24、ld be measured between the acoustic interface and the interfacex. In the usual case where the PLMN introduces no additional loss or attenuation distortion between interface X and the NCP, the loudness ratings up to the PSTNASDN will be the same as loudness ratings measured at interface X. For more d
25、etails see A.3.1. 2.2 Stability The stability requirements will be met if the attenuation between the digital input and digital output of the PLMN at the NCP is at least 6 dB. For more details see A.3.2. 2.3 Propagation time The following values are given for the mean one-way propagation time of the
26、 PLMN: recommended value c 40 ms (see Note). NOTE -Technical and practical considerations do not permit the recommended value to be achieved at this time. Existing PLMNs should provide acceptable service on many connections but compliance with Recommendations G. 1 14 and G. i 3 I may not be assured
27、on ali connections (see A.3.3). 2.4 Echo control Due to the high propagation time, echo control is necessary within the PLMN. For reducing the PSTNASDN network echo, an echo control device is needed at the NCP. The PLMN echo loss at the NCP shall be greater than 45 dB. If there is no additional loss
28、 in the PLMN, the terminal coupling loss of the MS has to fulfil the echo requirements. 2 Recommendation G.173 (03/93) ITU-T RECMNxG.173 93 Li625L 0589512 135 m For discussion related to connections involving PLMN echo control devices and PSTNDSDN echo control devices, see A.3.4. Subclause A.3.4 als
29、o included discussion on PLMN echo loss objectives for the evolving PSTNiSDN. Technical and practical considerations do not permit the recommended value to be achieved at this time. According to Recommendation P.31 the weighted terminai coupling loss (TCLw) of a digital telephone should be greater t
30、han 40 dB. The characteristics of the PLMN, including the PLMN canceller used to cancel PSTNDSDN network echoes, must not compromise the operation of network based G. 165 cancellers. 2.5 Quantizing distortion For the quantizing distortion of the PLMN in error free conditions between the acoustic int
31、erface and the NCP. the following values are given: recommended value 4 qdu (see Note 1). The qdu of PLMN under realistic bit-error-rate conditions (conditions to be determined): recommended value 7 qdu (see Note 1). NOTES 1 Technical and practical considerations do not permit the recommended values
32、 to be achieved at this time by all systems. Existing PLMNs should provide acceptable service on many connections but compliance with Recommendation G. 113 may not be assured on all connections (see A.3.5). It should be noted that in some cases such as low bit rate (5 8 kbit/s) non-waveform codecs.
33、the concept of quantizing 2 distortion units (qdu) may not apply. 2.6 Clipping For clipping no specific requirement is given. For more information see A.3.6. 2.7 Noise contrast For noise contrast no specific requirement is given. For more information see A.3.7. 2.8 Other requirements The PLMN should
34、 be designed to be in accordance with relevant CCIIT Recommendations concerning: - sidetone; - noise; - sensitivity/frequency characteristics; - distortion; - out-of-band signals; - goheturn crosstalk. The transmission requirements of handset MS should be derived from the requirements of digital tel
35、ephones stated in Recommendation P.3 1. For headset telephones, information can be found in Recommendation P.38 and for handsfree telephones using loudspeakers, see Recommendation P.34. Recommendation G.173 (03/93) 3 Annex A Definitions and detailed transmission aspects (This annex forms an integral
36、 part of this Recommendation) A.l Definitions For the purpose of this Recommendation, the following definitions apply: A.l.l base station (BS): A base station (BS) is a radio transmitter/receiver station in a PLMN which provides the radio transmission path to the mobile station. Several base station
37、s are connected via leased lines to a mobile services switching centre. A.1.2 digital mobile system: The basic configuration of a digital mobile system is shown in Figure A.1. A digital mobile system consists of the mobile station, radio transmission path, base station, leased line and the mobile se
38、rvices switching centre up to the network connection point (NCP). I fjg i q=j+ BS MSC Air interface NCP T1205620Wd2 FIGURE A. 1/G. 173 Basic configuration of a digital mobe system A.1.3 mobile services switching centre (MSC): The MSC performs all necessary signalling and transmission functions in or
39、der to establish connections to and from mobile stations. A mobile station is registered at one MSC which functions as its home-MSC for charging and billing purposes. In order to obtain radio coverage in a given geographical area, a number of base stations are normally required, i.e. each MSC is int
40、erconnected with several base stations. In addition, several MSCs may be required in order to cover the area of a PLMN. A.1.4 to the customer in a PLMN. It provides access via a base station to the PSTN/ISDN and to other mobile stations. mobile station (MS): A mobile station (MS) is transportable te
41、rminal equipment providing different services A.1.5 network connection point (NCP): A network connection point is a point at which, in general, two independent networks are interconnected. In the context of this Recommendation, NCP refers to the connection point between a PLMN and the PSTNASDN. A.1.
42、6 services switching centre areas within a common numbering plan and a common routing plan. public land mobile network (PLMN): A public land mobile network may be defined as a number of mobile With respect to their functions, the PLMNs may be regarded as independent communications entities, even tho
43、ugh different PLMNs miy be interconnected through the PSTN/ISDN for the forwarding of calls or network information. The MSCs of a PLMN can be interconnected similarly to allow interaction. 4 Recommend at ion G -173 (03/93) ITU-T RECMN*G.273 93 48b2591 0589534 TO8 The use of the PLMN concept is illus
44、trated in Figure A.2 where various PLMNs and their interfaces to the fixed networks are shown. It should be noted that a PLMN may have several interfaces with the fmd network (e.g. one for each MSC). Interworking between two PLMNs may be performed via an international switching centre. Figure A.2 al
45、so shows the information paths between a PSTNASDN and a PLMN and between two different PLMNs. The solid lines indicate a possible physical path between the PLMNs through the PSTNASDN. The dotted line indicates that for some interactions an end-to-end information path may exist between the PLMNs. The
46、 PLMN is connected via an NCP to the PSTNASDN. if there are two mobile service suppliers in the same country, they can be connected through the same PSTNASDN. FIGURE A.YG.173 The useofthe PLMN concept for country A and amtry B A.2 Detailed model of the digital land mobile system A.2.1 General A more
47、 detailed model of the digital land mobile system used for the consideration of transmission planning issues for the speech service is shown in Figure A.3. This model is an example of the relevant functions and does not necessarily imply any particular physical realization. In a digital mobile syste
48、m three mobile stations with different acoustic interfaces have to be considered: - handset MS; - headset MS; - handsfree MS using loudspeakers. Several coding methods with low rate encoding (LE) have been proposed to achieve spectrum efficiency on the radio path. In addition to the LRE, it is also
49、possible to include digital speech interpolation via the radio path. For transmission planning aspects the transmission system (leased line) between the BS and the MSC have to be taken into account. Because of speech coding and/or other channel processing techniques, the propagation time is of such magnitude that echo control devices may be required at both ends of the digital mobile system. Any acoustic echo control in the MSs will be provided by analogue processing or digital processing or a combination of both techniques. The electric echo control device at the NCP shoul
