EFM Capabilities with Plan 998 Performance analysis of the standard VDSL technology using spectral plan 998 Vladimir Oksman Broadcom Corporation October 2001 Slide 1
Supporters Sabit Say, Todd Pett: Next Level Communications Danny Gur, Idan Alrod: Metalink Steven Haas, John Egan: Infineon Rami Verbin: Tioga Technologies Juri Sipila: VDSL Systems Ron McConnell: Telebyte Slide 2
Goal Intensive analysis of spectral plan 998, aimed to: Check compliance with the requirements indicated by service providers Find ways for improvement NOTE: All presented results are based on the current standard single-carrier modulation (SCM) technology. It uses the worst-case description of the loop topology and noise environment, and considers all transmit signal limitations adopted for North American access networks. Slide 3
Requirements Analysis of extensive discussions on EFM reflector leads to the following conclusions regarding the copper EFM performance requirements Reach: Minimum: Maximum : 2.5 kft with at least 10 Mb/s aggregate up to CSA (9 kft @ 26AWG) and more Main services: 2-3 video channels (VoD and broadcast) high speed data high quality audio Spectral compatibility Environment: unbundled Compliance: T1.417, NRIC-V (spectral plan 998), ITU-T, ETSI Consideration: HPNA Slide 4
Typical installation OLT CO AN Local Exchange ONU ETU-O FTTEx Customer Premises NT ETU-R Core Network Access Network Other xdsl Feeder Cable (200-2000 pairs) Cabinet ONU ETU-O FTTCab BR-ISDN HDSL, ADSL Customer Premises NT ETU-R AN ONU ETU - access network - optical network unit - EFM transmission unit Distribution Cable (25-50 pairs) Drop Cable (2-5 pairs) Slide 5
Plan 998: Background Plan 998 was proposed by international group of operators (FSAN) in 1999 to accommodate the most popular services Plan 998 was accepted by T1E1.4 and NRIC-V as the only spectral plan above 1.104 MHz to be used in North America Plan 998 is currently proposed to ITU-T as a U.S. position to be internationally recognized for only use in North America Plan 998 was accepted by ETSI as a regional plan for Europe Japan requested ITU-T to consider 998 as the national spectral plan Slide 6
Plan 998: Overview Five bands of 998 allow accommodation of symmetric and asymmetric services over loops of different length 0.25 0.138 3.75 5.2 8.5 12.0 O 1D 1U 2D 2U 1. Band O is optional and could be used for either upstream or downstream transmission 2. Band O can t be used if EFM shares the same pair with BR-ISDN Slide 7
Plan 998 for short and medium loops Case 1: Short loops: < 2.5 kft @ 26 AWG 1D 1U 2D 2U MHz 0 0.138 3.75 5.2 8.5 12 Case 2: Medium loops: 2.5-3.5 kft @ 26 AWG 1D 1U 2D MHz 0 0.138 3.75 5.2 8.5 12 Slide 8
Plan 998 for medium and long loops Case 3: Medium loops: 3.5-4 kft @ 26 AWG 2U 1D 1U MHz 0 0.138 3.75 5.2 8.5 12 Case 4: Long and very loops: 4-15 kft @ 26 AWG 2U 1D MHz 0 0.138 3.75 5.2 8.5 12 Slide 9
Method of performance evaluation Performance of any loop of length L in both upstream and downstream direction is evaluated by its channel capacity C: SNR f L C L (, ) ( ) = log + 2 1 df G, F - SNR(f,L) - receiver signal-to-noise ration - G - SNR gap SNR = S( f FEXT ( n, 2 ) H ( f, L) f, L) + BGN ( f ), - S(f) - PSD of the transmit signal - H(f,L) - module of the loop transfer function - FEXT - self-fext PSD from n EFM disturbers - BGN - background noise PSD, includes WGN, quantization noise, and crosstalk from other xdsl. Slide 10
Noise environment Self-FEXT of 20 EFM disturbers - FEXT coupling function for the 99% worst case: FEXT = 8 10 20 L f 2 n fext 49 0.6 H 2 ( f, L) Self-NEXT is not considered (FDD duplexing) Background noise - WGN of -140 dbm/hz - Quantization noise of -146 dbm/hz - Alien crosstalk (NEXT and FEXT from other xdsl) Slide 11
Alien crosstalk It was adopted in standard bodies to specify alien crosstalk by noise models T1E1.4 specifies two models: A and F. Additional model D was also considered in this analysis Model A - applied for cabinet-based deployments (FTTCab) - crosstalkers: 16 BR-ISDN, 10 EC-ADSL, 4 HDSL - 3 kft minimal distance from the exchange Models D,F - applied for exchange-based deployments (FTTEx) - crosstalkers D: 16 BR-ISDN, 10 EC-ADSL, 4 HDSL - crosstalkers F: 16 BR-ISDN, 10 EC-ADSL, 4 HDSL, 2 T1 - T1 only in the adjacent binders Slide 12
Combined PSD of alien crosstalk -20-40 -60 ANSI alien noise PSD DS, noise D US, noise A,D DS, noise A DS, noise F US, noise F PSD, dbm/hz -80-100 -120-140 0 2 4 6 8 10 12 frequency, MHz Slide 13
Upstream power back-off The standard (T1E1.4/ITU-T/ETSI) UPBO method used The transmit PSD in the upstream direction set by estimation of the electrical length l e of the loop as: TxPSD = min{ PSD_REF + kl e f, PSD 0 }, dbm/hz The used standard value of Reference PSD (PSD_REF) is optimized for service bit rates between 3 to 9 Mb/s The worst case loop topology considered for upstream performance (concentrated topology) Slide 14
-40 dbm/hz Transmit PSD mask M2, Cabinet-based M2, CO-based -50-53 -55-60 U 1U 2U -100-120 25 khz 138 khz 1 MHz 1.6MHz 2MHz 3.5MHz 7MHz 12MHz 30MHz F Slide 15
Other simulation data Transmit PSD Standard T1E1.4 Mask M2 Transmit power 14.5 dbm, except 11.5 dbm for FTTCab downstream Shaping Square-root raised cosine (Tx and Rx) Excess bandwidth 20% Coding gain 3.8 db Noise margin 6.0 db Shannon gap 9.8 db SNR gap 9.8-3.8 + 6 = 12 db Loop type Bridged taps Universal loop model of mixed TP1 (26AWG) and TP2 (24AWG), CSA=10.3 kft NO Slide 16
Plan 998: Short and medium loops 40 35 30 Capacity (998, M2, A,D,F AWG=-140, gb=0, eb=20%, Univ. Loop) US FTTEx, noise D DS FTTEx, noise D DS FTTEx, noise F US FTTEx, noise F DS FTTCab, noise A US FTTCab, noise A channel capacity, Mb/s 25 20 15 10 5 Note: no optional band used 0 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 loop length, kft Slide 17
Observation 1 Plan 998 allows - downstream bit rates greater than 22 Mb/s (three video channels) with upstream bit rates more than 3 Mb/s for distance of about 3.5 kft - symmetric bit rates greater than 10 Mb/s (20 Mb/s aggregate) for distance of about 2.7 kft Performance of a standard 998 with no optional band used is limited by the upstream capacity Slide 18
Optional band for more upstream Upstream capacity (998, M2, A,D,F, AWG=-140, gb=0, eb=20%, Univ.loop) 12 10 FTTEx, noise F, standard FTTEx, noise F, opt band FTTEx, noise D, opt band FTTEx, noise D, standard FTTCab, noise A, standard FTTCab, noise A, opt band channel capacity, Mb/s 8 6 4 2 0 3 4 5 6 7 8 9 loop length, kft Note: No restrictions on signal constellation applied for the optional band Slide 19
Plan 998: Long loops Capacity (998, M2, A,D,F, AWG=-140, gb=0, eb=20%, Univ.loop) 20 US, FTTCab, noise A US, FTTEx, noise D DS, FTTCab, noise A DS, FTTEx, noise D DS, FTTEx, noise F US, FTTEx, noise F channel capacity, Mb/s 15 10 5 0 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 loop length, kft Slide 20
Plan 998: Very long loops 6 5 Capacity (998, M2, A,D, AWG=-140, gb=0, eb=20%, Univ.loop) DS, FTTEx, noise D US, FTTCab, noise A DS, FTTCab, noise A US, FTTEx, noise D channel capacity, Mb/s 4 3 2 1 0 8 9 10 11 12 13 14 15 16 17 18 loop length, kft Slide 21
Observation 2 With optional upstream band used plan 998 allows: - reach of up to 10 kft with at least 1/1 Mb/s capacity - reach of up to 16 kft with at least 0.5 Mb/s capacity for Exchange-based deployments - reach of up to 12 kft with at least 0.5 Mb/s capacity for Cabinet-based deployments Performance of 998 with optional upstream band used is limited by the downstream capacity Slide 22
Plan 998: performance summary Service (channel capacity) Maximum reach (no T1) kft 3 video channels and data (~ 22 Mb/s) 3.8 2 video channels and data (~ 16 Mb/s) 4.2 Data (10/10 Mb/s) 2.7 Data (16/1 Mb/s) 4.2 Maximum reach with no optional band 4.4 Data (1/1 Mb/s) 10 Maximum reach (data 0.5/0.5 Mb/s) 16 Slide 23
How to improve it? Upstream performance for long loops can be improved by extending the upstream band up to 300-500 khz. The improvement of the upstream performance, however, comes on the account of downstream performance. Expected to be good for 4-7 kft loops. Slide 24
Conclusion Standard plan 998 demonstrates excellent performance characteristics for video and data transmission for deployments with loop length below 4 kft For longer loops performance is limited by the upstream, however usage of optional upstream band extends the reach up to 10 kft with channel capacity of at least 1 Mb/s The absolute maximum reach is limited by the downstream to 16 kft with channel capacity of at least 0.5 Mb/s Further improvement for long loops may be achieved by extending the optional upstream band over 138 khz Slide 25