ADSL (Asymmetrical Digital Subscriber Line) details

Transcription

1 ADSL (Asymmetrical Digital Subscriber Line) details A D S L Asymmetrical Digital Subscriber Line Central Office Customer premises High- Rate channel Low- Rate channel LP HP Spectrum At the beginning two competing transmission schemes: CAP and DMT; Finally chosen: DMT

2 ADSL details ADSL variants: ANSI: T1.413 (POTS-ADSL), ETSI: DTS/TM (ISDN-ADSL), ITU-T: G.dmt (G.992.1, up to carrier no. 255), G.lite (G.992.2, half the number of carriers, up to 127), ADSL2 (G.992.3,all digital loop), ADSL2+ (G twice as many carriers, up to 511) Downstream rate: max. 8,192 Mbit/s Upstream rate (Duplex): max. 640 kbit/s Rate choosable in 32-kb/s staps

3 Standard ADSL (G.991.1) LDS in db(mw/hz) f in MHz Downstr. rate: max. 8,192 Mbit/s Upstr. rate (duplex): max. 640 kbit/s N = 512 N akt < N/2 = 256 Carrier spacing: 4,3125 khz POTS Downstream: Upstream: 6-31 ISDN : Downstream: 32(33) Upstream: 32(33) - 63 Used band: 21,5625/138 khz 1,104 MHz DS pilot at 276 khz, i.e., carrier 64

4 Standard ADSL (G.991.1) Interleaved (slow) and non-interleaved (fast) buffers Parameter Parity bytes per R-S codeword DMT symbols per R-S codeword Interleave depth S = 1 Fast buffer R F = 0, 2, 4, 6, 8, 10, 12, 14, 16 (Note 1) Not applicable Interleaved buffer R I = 0, 2, 4, 6, 8, 10, 12, 14, 16 (Notes 1 and 2) S = 1, 2, 4, 8, 16 D = 1, 2, 4, 8, 16, 32, 64 Bit allocation up to 15 bits per carrier

5 "bits" "Bits" & "Gains" AS0 AS1 AS2 AS3 LS0 LS1 LS2 NTR Mux/ Sync Control crc f crc i scrambler & FEC scrambler & FEC Interleaver Tone ordering Constellation encoder and gain scaling IDFT n=0 Output Parallel/ Serial Buffer OAM V-C EOC/AOC ib Reference Points A Mux Data Frame B FEC Output Data Frame C Constellation Encoder Input Data Frame Z i i=1 to 255 DAC and Analogue processing T NOTE Solid versus dashed lines are used to indicate required versus optional capabilities respectively. This figure is not intended to be complete in this respect, see clauses 6 and 7 for specific details. "Bits" & "Bits" "Gains" ATM0 ATM1 NTR AS0 Cell TC Cell TC AS1 Mux/ Sync Control crc f crc i scrambler & FEC scrambler & FEC Interleaver Tone ordering Constellation encoder and gain scaling IDFT n=0 Output Parallel/ Serial Buffer OAM V-C EOC/AOC ib Reference Points A Mux Data Frame B FEC Output Data Frame C Constellation Encoder Input Data Frame Z i i=1 to 255 DAC and Analogue processing T NOTE Solid versus dashed lines are used to indicate required versus optional capabilities respectively. This figure is not intended to be complete in this respect, see clauses 6 and 7 for specific details.

6 AS0 (n 0 32 kbit/s) AS1 (n 1 32 kbit/s) AS2 (n 2 32 kbit/s) STM Layer AS3 (n 3 32 kbit/s) and interface to Digital Network LS0 ("C"; 16 or m 0 32 kbit/s) LS1 (m 1 32 kbit/s) LS2 (m 2 32 kbit/s) ATU-C twisted pair NTR Operations, administration, maintenance and control V-C T NOTE Optional bearer channels (both duplex and simplex) and features are shown with dotted lines.

7 G (G.lite, splitterless ADSL ) AS0(downstream) shall support the transport of data at all integer multiples of 32 kbit/s from 64 kbit/s to Mbit/s. Bearer channel LS0 (upstream) shall support all integer multiples of 32 kbit from 32 kbit/s to 512 kbit/s Number of carriers: 32/128, CP 16 No ISDN compatibility! In the downstream direction, pilot at carrier 64 Splitterless is not true! It requires a mini-filter (a highpass) at every outlet. WHY? Reduced parameter sets apply, as far as bit-allocation, RS, interleaving depth, S are concerned.

8 G ADSL2 = ADSL with some extensions 36.5 peak DOWN Power 20.4 dbm PSD db/octave 97.5 peak +15 dbrn 0-4 khz 92.5 peak 36 db/octave dbm power in any 1 MHz sliding window above 4545 khz Frequency T peak 21.5 db/octave dbrn 0-4 khz 92.5 peak 48 db/octave 90 peak 50 dbm power in any 1 MHz sliding window above 1630 khz UP Power 12.5 dbm PSD Frequency 1630 T

9 G ADSL2 With a data symbol rate of 4 khz, a DMT subcarriers spacing of f= khz and an IDFT size of 2xNSC, a cyclic prefix of (2 x NSC x 5/64) samples could be used. That is, (2 x NSC + 2 x NSC x 5/64) 4.0 khz = (2 x NSC) khz = fs (the sample frequency) The cyclic prefix shall, however, be shortened to (2 x NSC x 4/64 = NSC/8) samples, and a synchronization symbol (with a length of 2 x NSC x 68/64 samples) is inserted after every 68 data symbols. That is, (2 x NSC x 4/ x NSC) 69 = (2 x NSC x 5/ x NSC) 68

10 G ADSL2: ISDN support Number of upstream carriers: 32 or 64 Power: down 19.8 dbm, up 13.8 dbm peak 24 db/octave 90 peak 48 db/octave 36 db/octave 90 peak 50 dbm max power in any 1 MHz sliding window above 4545 khz Frequency PS in peak 48 db/octave 12 db/octave 90 peak 90 peak 50 dbm max power in any 1 MHz sliding window above 1630 khz Frequency

11 G ADSL2: all digital loop 12 db/octave 48.5 peak 36.5 peak 36 db/octave 90 peak 20.4 dbm 50 dbm max power in any 1 MHz sliding window above 4545 khz PSD (db) Frequency 12 db/octave 48.5 peak 34.5 peak 48 db/octave 90 peak 12.5 dbm 50 dbm max power in any 1 MHz sliding window above 1630 khz Frequency (khz)

12 G ADSL2 Relative to the Recommendation G.992.1, the following application related features have been added: Improved application support for an all digital mode of operation and voice over ADSL operation; Packet TPS-TC function, in addition to the existing STM and ATM TPS-TC functions; Mandatory support of 8 Mbit/s downstream and 800 kbit/s upstream for TPS-TC function #0 and frame bearer #0; Support for IMA in the ATM TPS-TC; Improved configuration capability for each TPS-TC with configuration of latency, BER and minimum, maximum and reserved data rate. A more flexible framing, including support for up to 4 frame bearers, 4 latency paths; Parameters allowing enhanced configuration of the overhead channel; Frame structure with receiver selected coding parameters; Frame structure with optimized use of RS coding gain; Frame structure with configurable latency and bit error ratio; OAM protocol to retrieve more detailed performance monitoring information; Enhanced on-line reconfiguration capabilities including dynamic rate repartitioning.

13 G ADSL2plus 16 Mbit/s downstream and 800 kbit/s upstream. Support of net data rates above 16 Mbit/s downstream and support of net data rates above 800 kbit/s upstream are optional relative to the Recommendation Extended downstream bandwidth to MHz (512 subcarriers) for all operation modes (POTS/ISDN/All Digital Mode); Downstream spectrum control with individual maximum transmit PSD at U-C reference point per subcarrier, under operator control through CO-MIB, allows configuration per the regional requirements (e.g., North-America, Europe or Japan) and deployment scenarios (e.g., CO or Remote). Downstream spectrum shaping during Showtime (shaped transmit the passband, i.e., non-flat) for improved downstream transmit PSD flexibility.

14 G ADSL2plus - PSD over POTS db/octave 3 db/octave 21 db/octave 97.5 peak +15 dbrn 0-4 khz db/octave 78 db/octave above 3750 khz Frequency db/octave 97.5 peak +15 dbrn 0-4 khz db/octave -15 db/dec 100 above 3750 khz Frequency

15 G ADSL2plus:Non-overlapped mode 36 db/octave 4.63 db/octave 97.5 peak +15 dbrn 0-4 khz db/octave 3 db/octave 65 db/octave db/octave 100 above 3750 khz Frequency db/octave 97.5 peak +15 dbrn 0-4 khz db/octave -15 db/dec 100 above 3750 khz Frequency

16 G ADSL2plus: Overlapped for ISDN 12 db/octave db/octave db/octave 77.4 db/octave 65 db/octave db/octave 100 above 3750 khz Frequency db/octave 12 db/octave db/octave -15 db/dec above 1411 khz Frequency

17 G ADSL2plus: ISDN non-overlapped 24 db/octave db/octave db/octave db/octave db/octave db/octave 100 above 3750 khz Frequency db/octave 12 db/octave db/octave -15 db/dec above 1411 khz Frequency

18 G ADSL2plus: All-digital loop db/octave db/octave 3 db/octave 65 db/octave db/octave 100 above 3750 khz Frequency db/octave db/octave -15 db/dec 100 above 3750 khz Frequency