W. Yu, G.Ginis, J. Cioffi Information Systems Laboratory Stanford University Stanford, CA Phone: ; Fax:

Transcription

1 04/19/99 1 T1E1.4/ T1E1.4/ Project: T1E1.4: VDSL and ITU Title: VDSL Performance Requirement Verification for ITU (99-200) Contact: W. Yu, G.Ginis, J. Cioffi Information Systems Laboratory Stanford University Stanford, CA Phone: ; Fax: K. Jacobsen Texas Instruments 2043 Samaritan Dr. San Jose, CA Phone: ; Fax: Date: April 20, 1999 Dist'n: T1E1.4 Abstract: This contribution seeks US consensus position to be formally decided at US Study Group B in June 1999 that verifies VDSL system requirements performance compliance according to [1] for the transmission technique in [2]. Results for the test situations in Section 6.5 are presented using the standardized methods in the ANSI spectrum management project [3]. NOTICE This contribution has been prepared to assist Standards Committee T1 - Telecommunications. This document is offered to the Committee as a basis for discussion and is not a binding on any of the companies listed as authors. The requirements are subject to change after further study. The authors specifically reserve the right to add to, amend, or withdraw the statements contained herein.

2 04/19/99 2 T1E1.4/ VDSL Performance Requirement Verification for ITU W. Yu, G.Ginis, J. Cioffi Information Systems Laboratory Stanford University, Stanford, CA Phone: Fax: K. Jacobsen Texas Instruments 2043 Samaritan Dr. San Jose, CA Phone: Fax: Abstract This contribution seeks US consensus position to be formally decided at US Study Group B in June 1999 that verifies VDSL system requirements performance compliance according to [1] for the transmission technique in [2]. Results for the test situations in Section 6.5 are presented using the standardized methods in the ANSI spectrum management project [3]. 1. Introduction Section 6.5 of the T1E1.4 VDSL System Requirements Document ([1]) details several tests for verification of compliance of a VDSL transmission method. This contribution evaluates the transmission method proposed in [2] for each of those test conditions according to standardized evaluation procedures specified in the spectrum management standard (draft in [3]). The results indicate compliance at the levels indicated and further that these levels are consistent with performance objectives generally outlined in Section 6 of [1]. This contribution seeks consensus support through US Study Group B in June 1999 for a US position validating the results within. 1 Section 2 further describes the transmission method used, specifically detailing a consistent frequencydivision duplexing format for each of the cases of symmetric and asymmetric transmission. Section 2 further outlines some rationale for the selection that goes beyond current US VDSL system requirements to encompass protection of Home Phone Network of American (HPNA) signals as detailed in [4]. Section 3 lists results in tabular form. 2. VDSL Transmission System Description The VDSL transmission system is detailed in [2], but uses DMT transmission technology with the following parameters: Tone width khz Maximum bandwidth MHz Transmit power 11.5 dbm (following ADSL-compatible PSD mask in [1]) parameters A-ON, N-OFF and N-ON (see tables), V-ON For duplexing, the maximum bandwidth is partitioned into 16 subbands corresponding to the frequencies 1 The time of the T1E1.4 full meeting in June is such that Study Group B occurs first, so US position papers will go directly to Study Group B, but this contribution seeks to inform US participants of such intent and to solicit comment prior to the SG B meeting.

3 04/19/99 3 T1E1.4/ ( MHz) < f < ( k + 1) ( MHz) k = 0,..., 15 k. Each of these 16 frequency bands is allocated to either upstream or to downstream transmission according to the digital frequency duplexing method with cyclic prefix and suffix described in [2], which does not require guard bands for reversal of transmission direction on adjacent frequencies. However, the use of 16 bands allows a reduction in the analysis-complexity of attempting to find best duplexing option. To protect both ADSL and HPNA, upstream transmission was forbidden in the band with k=0 and the bands for k=5,6,,8 (presuming transmitter windowing for sharp decay of out-of-band energy). Thus there are 11 = possible band assignments that need to be investigated. The band selection method for symmetric service was the following: Band assignments were ranked with respect to total achieved data rate for the following 6 scenarios: Length (ft.) noise x cable 1) 300m VDSL1, 20 VDSL FEXT, Noise A, cable 26 2) 300m VDSL1, 20 VDSL FEXT, Noise B, cable 26 3) 1000m VDSL1, 20 VDSL FEXT, Noise A, cable 26 4) 1000m VDSL1, 20 VDSL FEXT, Noise B, cable 26 5) 300m VDSL1 with BT, 20 VDSL FEXT, White noise, cable 26 6) 1000m VDSL1 with BT, 20 VDSL FEXT, White noise, cable 26 For each scenario, a ranking of the 165 assignments is produced (lower rates to higher rates). Each assignment receives a total score, which is equal to the sum of its rank positions for each of the 6 scenarios. The assignment with the maximum score is then chosen. This particular assignment may not be optimum (but optimum is hard to define in this context of multiple channel types and multiple data rates), but produced assignments for the asymmetric and symmetric 2 transmission that appear to meet requirements. k=0 corresponds to the same band as ADSL and is downstream in both cases. k=5,6,,8,9 overlap HPNA band and so were allocated downstream in both cases also (although k=9 was not forced, the optimization produced it as downstream anyway in both cases, further protecting the HPNA band). The two frequency allocations then were ("ZIP-CODE 16"): k Asymmetric Symmetric 0 down down 1 down down 2 down up 3 down up 4 up up 5 down down 6 down down down down 8 down down 9 down down 10 down up 11 down up 12 down up 13 down up 14 down up 15 down down 2 For the symmetric band allocation, we only tested allocations with equal number of upstream and downstream bands. This symmetric searching leads to the number 11 choose 3, or 165. (Of 16 bands, 5 are decided, or choose 3 more out of 11 remaining.) The asymmetric assignment only requires search of the 11 bands to see which is best for upstream transmission.

4 04/19/99 4 T1E1.4/ While these particular allocations are not optimum for all situations, they prevent VDSL self-next. Also long-range asymmetric VDSL is affected by symmetric VDSL NEXT only in the bands for k=2 and k=3. However, upstream symmetric is then affected by VDSL NEXT in the same two bands, which may be a more substantial reduction in symmetric range reduction. Thus, medium and long-range asymmetric performance (which are closest to the minimum requirements) is less degraded by mixture than is symmetric performance (which exceeds requirements substantially in most cases). Such mixture is not required by T1E1.4, but may be required by the ITU, but performance requirements are not yet specified so no testing is possible. (Additional information is available from authors on request.) 3. Performance Results Performance is to be specified in achievable range for 26 and twisted pair for 4 testing situations in Section 6.5 of [1]: TEST 1: Tests (VDSL FEXT and AWGN only) TEST 2: Radio Tests (add Radio notching of PSD in [1] to TEST 1) TEST 3: Xtalk limited Tests - (add Noise Models A and B to TEST 1) TEST 4: Optional Bridged-tap Tests (add 50' bridged tap to TEST 1) For each test, a table summarizes the achievable range rounded to the nearest 150 feet as mandated in [1]. 10. Results are presented for 3.8 and.3 db 3 of coding gain with a 6 db margin at probability of error Rough objectives as outlined in [1] are High-speed short range ft. of (1500 ft of ) Medium-speed, medium range ft. Low-speed, long range ft. Tests are considered past if within 10% of the objective (either way) and those that are 10% or more off objective are shaded, underlined, and in bold face for easy location. 3.1 TEST 1 TEST 1 results for (with 20 VDSL FEXT) Short sym Med sym Short asym Med asym Long asym Results for.3 db coding gain could reflect margin reduction, soft-decoding of Reed Solomon FEC codes, concatenated coding with trellis or turbo codes, or a modest improvement caused by various crosstalk reduction/mitigation schemes (multiuser detection). This figure is intended to provide some information on the potential performance should more complex decoding methods be used with the proposal in [2], or should 6 db margin be reduced as in HDSL-2 project.

5 04/19/99 5 T1E1.4/ TEST 1 results for (with 20 VDSL FEXT) Coding gain is.3 db, margin is 6 db, at 10 error rate Short sym Med sym Short asym Med asym Long asym TEST 2 TEST 2 results for RF Noise (and 20 VDSL FEXT) Short sym Med sym Short asym Med asym Long asym TEST 2 results for RF Noise (and 20 VDSL FEXT) Coding gain is.3 db, margin is 6 db, at 10 error rate Short sym Med sym Short asym Med asym Long asym TEST 3 TEST 3 results for Noise Model A (and 20 VDSL FEXT) Short sym Med sym Short asym Med asym Long asym

6 04/19/99 6 T1E1.4/ TEST 3 results for Noise Model A (and 20 VDSL FEXT) Coding gain is.3 db, margin is 6 db, at 10 error rate Short sym Med sym Short asym Med asym Long asym TEST 3 results for Noise Model B (and 20 VDSL FEXT) Short sym Med sym Short asym Med asym Long asym TEST 3 results for Noise Model B (and 20 VDSL FEXT) Coding gain is.3 db, margin is 6 db, at 10 error rate Short sym Med sym Short asym Med asym Long asym The only test at full coding gain to be 10% in below required range (in fact, it is exactly 10% in error) is the Noise-B test. Note the upstream data rate is well above the required 1.6 Mbps - this means that if the duplexing scheme were further subdivided into a larger number of bands than 16 as here, this requirement could be met. However, it is sufficiently close at the 10% limit to suggest such further partitioning is unnecessary.

7 04/19/99 T1E1.4/ TEST 4 TEST 4 results for Bridged Tap (and 20 VDSL FEXT) Short sym Med sym Short asym Med asym Long asym TEST 4 results for Bridged Tap (and 20 VDSL FEXT) Coding gain is.3 db, margin is 6 db, at 10 error rate Short sym Med sym Short asym Med asym Long asym Conclusion The VDSL transmission system from [2] was found to meet the performance system requirements. This set of transmission calculations according to the standardized transmission calculation method in [3] is important in that it establishes the US VDSL performance requirements as feasible, thus supporting their inclusion in ITU requirements. The verification of meeting such requirements with a US consensus position to the ITU through US Study Group B meeting in June should strengthen US position with respect to a rapidly moving ITU VDSL standardization process. 5. References [1] ANSI T1E1.4 Contribution R8, "VDSL System Requirements Document," December 1998 (Editor, J. Cioffi). [2] " Physical Medium Specific Specification for G.vdsl," Alcatel et al., ITU SG15/Q4 Temporary Document MA-050R2, March 29, 1999, (Editor, T. Pollet), Melbourne, Australia. [3] ANSI T1E1.4 Contribution R2, "T1E1.4: Spectrum Compatibility for Twisted-Pair Loop Transmission Systems," Draft Spectrum Management Standard (Editors, R. McDonald and B. Rezvani), April 20, 1999, Arlington, VA. [4] "Home PNA 1.0 Spectral Compatibility," 3COM et al, ANSI Contribution T1E1.4/99-190, (Editor D. Shaver), April 20, 1999, Arlington, VA.