SDSL Test Loops. Dirk Daecke Contact: Josef Hausner Marc Kimpe Infineon Technologies AG ADTRAN, Inc.

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1 ETSI TM6 Edinburgh, UK September 1999 TD08 Project: Title: Source: Author: SDSL SDSL Test Loops Dirk Daecke Contact: Josef Hausner Marc Kimpe Infineon Technologies AG ADTRAN, Inc. Balanstr Explorer Blvd. D München Huntsville, AL voice: voice: fax: fax: Armin Tannhäuser Siemens AG Hofmannstr. 51 D München voice: fax: Status: For discussion and decision General goals for SDSL loop reaches and requirements on loop models have already been defined by ETSI TM6 in previous meetings. In this contribution these requirements are used to develop a clear set of SDSL test loops which is consistent with existing ISDN and HDSL test loops. The configuration of ETSI HDSL loops is used and the cable lengths shall be scaled and adapted for the various SDSL data rates. This contribution has been prepared to assist ETSI TM6. This document is offered to the committee as a basis for discussion and is not a binding proposal on Siemens AG, Infineon Technologies AG, Inc. or ADTRAN, Inc.. The requirements are subject to change in form and numerical values after further study. Siemens AG, Infineon Technologies AG. and ADTRAN, Inc. specifically, reserve the right to add to, or amend, the statements contained herein.

2 In previous meetings ETSI made several decisions which set goals and requirements for the range and configuration of SDSL test loops. The progress in SDSL standardization now requires the definition of a complete set of test loops [3]. Two philosophies have emerged regarding the selection of test loops for SDSL. One is based on the work done for VDSL [8][9], the other approach, which is presented here is based on the work done in HDSL [1] and ISDN [1]. In both cases the loops will need to be scaled as a function of the bit rates. The main objectives for SDSL test loops have already been defined in previous ETSI documents [4]. In Grenoble the following goals for SDSL loops were formulated [5]: Existing cable types should be used as a basis for the design of SDSL test loops. As few loops as possible should be defined. A loop with bridge taps is required. Loop reach goals were derived from ISDN and HDSL requirements as 4.5 km for 384 kbit/s on 0.4 mm cable km for 2048 kbit/s on 0.4 mm cable 1 A complete set of SDSL test loops was determined by the Editing group for draft specification RE/TM (SDSL part 1) in their Geneva meeting (July 99). The predetermined outlines were taken to define a set of adequate test loops for the various SDSL bit rates. One premise was to develop test loops which are consistent with ISDN loops at 384 kbit/s and HDSL loops at 2048 kbit/s. Thereby these loops should also allow direct performance comparisons between ISDN, HDSL and SDSL. The following steps were taken: Reuse of HDSL [1] and ISDN [2] loop configurations Reuse of ISDN/HDSL cable parameters Meet loop reach requirements for 384 kbit/s (4.5 km) and 2048 kbit/s (2.4 km) Scale HDSL/ISDN loops for SDSL data rates In figure 1 the SDSL loop configurations are shown. The cable length Y depends on both the cable diameter and the data rate and has got to be scaled. The loop lengths of the 0.4 mm PE cables for 384 and 2048 kbit/s are used as fixed values. In [6] an adequate interpolation method is developed which can be used to scale the SDSL loops for the data rates in between. Since SDSL is a multi bit rate system it would be very complex and confusing to define distinct loop lengths for any realizable data rate. Approaches which require the usage of These loop reach goals were submitted by ETSI to ITU [3]. Since the SDSL linecode has not yet been completely specified and PSDs are not yet defined modification of these values might be necessary. 2

3 special formulas to determine a loop length at a certain data rate are possible, but the complexity of the conversion of these values contradicts ETSI s requirement of clarity [5]. In order to define a clear set of test loops it is important to limit their number. Therefore 384 kbit/s, 512 kbit/s, 768 kbit/s, 1024 kbit/s, 1280 kbit/s, 1536 kbit/s, 2048 kbit/s and 2304 kbit/s are chosen as principal SDSL payload data rates. The further data rates are grouped around these principal data rates. Other data rates classifications are possible. In that way eight classes of loop lengths and scaled SDSL loops are created. Each of these classes applies to a small range of data rates. Figure 2 generally illustrates the scaling of cables for the principal data rates as well as the associated classes of data rates. ÃPÃ%ULGJHÃ7DS ÃPPÃ3( ÃÃPÃ%ULGJHÃ7DS ÃÃPPÃ3( &RPPRQÃPRGH LQVHUWLRQÃFLUFXLW ÃG%ÃORVVÃDWÃÃN+] In [1] the loop length Y is defined by the sine wave insertion loss of the individual sections when measured at 150 khz as 22 db for the one pair system, 27 db for the two pair system and 31 db for the three pair system. Correspondingly the loop length in [2] is defined as 36 db when measured at 40 khz. 3

4 The insertion loss values Y (in db) can be converted to the physical lengths of the specific cable types. For the 0.4 mm PE cable (loop 2) the converted values are 2100 m for the single pair HDSL, 2500 m for the two pair HDSL, 2900 m for the three pair HDSL and 4463 m for the ISDN loop. In order to make the performance goals more transparent the scaled cable lengths in Table 1 may be given in meters. If the electrical lengths (Y in db) are converted to physical lengths (Y in m), the length of Y [m] depends on the cable type (0.4 mm, 0.5 mm, 0.6 mm or 0.8 mm) and on the data rate. A definition of these cables is given in the annex of this contribution. loop length 4500 m 2400 m payload bit rate [kbit/s] Group of payload bit rates kbit/s tbd tbd tbd kbit/s Tbd tbd tbd tbd kbit/s Tbd tbd tbd tbd kbit/s Tbd tbd tbd tbd kbit/s Tbd tbd tbd tbd kbit/s Tbd tbd tbd tbd kbit/s tbd tbd tbd kbit/s Tbd tbd tbd tbd If the cables are described by their physical lengths the fractional lengths (0.25Y, 0.5Y, 0.8Y etc.) can be easily calculated by multiplying the fraction with the values in Table 1. 4

5 The total attenuation of the composite loops 2, 3,4 and 5 is almost commensurate. Otherwise if the fractional lengths were defined by their attenuation the variations of the total attenuation of the loops are generally larger. The SDSL test loops which have been described above have been defined in such a way, that they can be realized with the actual HDSL loop simulators which are widely deployed. A similar proposal to reuse existing HDSL line simulators had already been made in [11]. The only adaptions which have to be made are due to the new FSAN noise model : Depending on the loop simulator model either the software has to be updated, the noise module has to be exchanged or FSAN noise is fed in from an external source. HDSL test equipment can be reused No large extra investments SDSL equipment can be evaluated in laboratories which have been equipped for HDSL tests. In this contribution a set of SDSL loops is developed. The HDSL/ISDN loop configurations shall be used and scaled for the new SDSL data rates. The cable lengths shall be derived from the ETSI requirements and goals and an interpolation method shall be applied. These SDSL loops can be realized with actual HDSL loop simulators. [1] ETSI, TS V1.5.1, High bit rate Digital Subscriber Line (HDSL) Third Edition, November 1998 [2] ETSI TS , Integrated Services Digital Network (ISDN) basic rate access, Third Edition, November 1998 [3] ITU Editor, G.shdsl, Updated Issues List for G.shdsl, Geneva, July 1999, TD 027R1(WP1/15) [4] Rob van den Brink, KPN, Performance tests for SDSL and other long range xdsl systems, ETSI-TM6 permanent documents TM6(98)10, (980p10a1), Grenoble, May 1999 [5] ETSI Access Networks, Report of meeting No.14 held in Grenoble 3 rd -7 th May 1999, ETSI TC/TM WG TM6(99)2 [6] Infineon Technologies, Scaling of SDSL test loops for different bit rates, Edinburgh, September 1999, 993t10a2 [7] ETSI STC TM6(97)02, Cable reference models for simulating metallic access networks, Third Edition, June 1998 [8] Rob van den Brink, KPN, Results of the ad hoc group on SDSL test loops, WD 19 (formerly WD 18), Grenoble, May 1999 [9] ETSI TS V1.1.5, Very high speed Digital Subscriber Line (VDSL), June 1999 [10] ETSI TS , Asymmetric Digital Subscriber Line (ADSL), November 1998 [11] Consultronics, Wirelines and Test Loops for SDSL, Villach, February 1999, 991t18a0 Defining SDSL loops by their physical length (in meters) is consistent with the FSAN noise model, where the calculated crosstalk also depends on this physical cable length. 5

Date: December 5, 1999 Dist'n: T1E1.4

Date: December 5, 1999 Dist'n: T1E1.4 12/04/99 1 T1E1.4/99-560 Project: T1E1.4: VDSL Title: Revisiting Bridged Tap and Spectrum Issue for VDSL Performance (560) Contact: J. Cioffi, W. Yu, and G. Ginis Dept of EE, Stanford U., Stanford, CA