391:----------------------------------------------------------------------------- Bin SNR Gain Bi - Bin SNR Gain Bi - Bin SNR Gain Bi - Bin SNR Gain Bi dB dB ts dB dB ts dB dB ts dB dB ts --- ----- ---- -- - --- ----- ---- -- - --- ----- ---- -- - --- ----- ---- -- 0 0.0 0.0 0 * 1 0.0 0.0 0 * 2 0.0 0.0 0 * 3 0.0 0.0 0 <- unused 4 0.0 0.0 0 * 5 0.0 0.0 0 * 6 0.0 0.7 0 * 7 0.0 0.7 0 <- unused 8 0.0 0.9 2 * 9 0.0 1.2 4 * 10 0.0 1.0 5 * 11 0.0 0.8 5 <- upstream 12 0.0 1.0 6 * 13 0.0 0.9 6 * 14 0.0 0.9 6 * 15 0.0 1.1 7 <- upstream 16 0.0 1.1 7 * 17 0.0 1.0 7 * 18 0.0 0.9 7 * 19 0.0 0.7 7 <- upstream 20 0.0 1.0 6 * 21 0.0 0.9 5 * 22 0.0 0.9 4 * 23 0.0 1.2 4 <- upstream 24 0.0 1.3 3 * 25 0.0 1.0 2 * 26 0.0 0.7 0 * 27 0.0 0.7 0 <- upstream 28 0.0 0.7 0 * 29 0.0 0.0 0 * 30 0.0 0.0 0 * 31 39.9 0.9 6 <- downstream 32 38.4 0.9 6 * 33 39.9 1.1 7 * 34 256.0 1.0 0 * 35 39.8 1.2 7 <- downstream (1 unused bin - interference?) 36 39.8 1.1 7 * 37 35.3 1.1 6 * 38 39.5 0.9 6 * 39 37.5 1.0 6 <- downstream 40 36.4 0.8 5 * 41 37.5 0.9 5 * 42 32.3 1.0 4 * 43 34.8 1.1 5 <- downstream 44 31.6 1.0 4 * 45 37.7 0.9 5 * 46 35.7 1.1 6 * 47 34.3 1.2 5 <- downstream 48 37.8 1.1 6 * 49 36.9 0.9 5 * 50 36.1 1.0 5 * 51 34.5 1.2 5 <- downstream 52 32.3 1.0 4 * 53 31.6 1.0 4 * 54 33.6 0.9 4 * 55 31.6 1.1 4 <- downstream 56 34.3 1.1 5 * 57 31.9 0.9 4 * 58 33.7 0.9 4 * 59 31.5 1.2 4 <- downstream 60 30.6 1.1 5 * 61 30.2 1.1 4 * 62 17.3 1.1 3 * 63 25.7 1.1 3 <- downstream 64 21.9 0.8 2 * 65 22.8 0.8 2 * 66 256.0 1.0 0 * 67 255.9 1.0 0 <- downstream (2 unused bins - interference?) 68 255.9 1.0 0 * 69 19.5 1.1 3 * 70 25.8 0.9 3 * 71 23.1 1.0 3 <- downstream (1 unused bin - interference?) 72 23.3 1.0 3 * 73 16.9 1.2 4 * 74 21.7 0.8 2 * 75 23.2 0.7 2 <- downstream 76 22.0 1.0 3 * 77 25.3 0.7 2 * 78 24.7 0.7 2 * 79 20.8 0.9 2 <- downstream 80 19.1 1.0 2 * 81 255.9 1.0 0 * 82 256.0 1.0 0 * 83 255.9 1.0 0 <- downstream 84 0.1 1.0 0 * 85 255.8 1.0 0 * 86 255.8 1.0 0 * 87 255.9 1.0 0 <- unused 88 256.0 1.0 0 * 89 256.0 1.0 0 * 90 255.9 1.0 0 * 91 255.9 1.0 0 <- unused 92 256.0 1.0 0 * 93 255.9 1.0 0 * 94 255.8 1.0 0 * 95 255.3 1.0 0 96 0.1 1.0 0 * 97 255.6 1.0 0 * 98 255.8 1.0 0 * 99 255.9 1.0 0 higher frequencies suffer greater 100 255.9 1.0 0 * 101 255.8 1.0 0 * 102 255.8 1.0 0 * 103 0.0 1.0 0 loss rates over longer lines 104 255.8 1.0 0 * 105 255.7 1.0 0 * 106 255.2 1.0 0 * 107 255.6 1.0 0 108 255.6 1.0 0 * 109 254.6 1.0 0 * 110 255.9 1.0 0 * 111 254.6 1.0 0 112 254.7 1.0 0 * 113 255.4 1.0 0 * 114 254.7 1.0 0 * 115 255.2 1.0 0 116 256.0 1.0 0 * 117 256.0 1.0 0 * 118 256.0 1.0 0 * 119 256.0 1.0 0 120 256.0 1.0 0 * 121 256.0 1.0 0 * 122 256.0 1.0 0 * 123 256.0 1.0 0 124 256.0 1.0 0 * 125 256.0 1.0 0 * 126 256.0 1.0 0 * 127 256.0 1.0 0 128 256.0 1.0 0 * 129 256.0 1.0 0 * 130 256.0 1.0 0 * 131 256.0 1.0 0 132 256.0 1.0 0 * 133 256.0 1.0 0 * 134 256.0 1.0 0 * 135 256.0 1.0 0 136 256.0 1.0 0 * 137 256.0 1.0 0 * 138 256.0 1.0 0 * 139 256.0 1.0 0 140 256.0 1.0 0 * 141 256.0 1.0 0 * 142 256.0 1.0 0 * 143 256.0 1.0 0 144 256.0 1.0 0 * 145 256.0 1.0 0 * 146 256.0 1.0 0 * 147 256.0 1.0 0 148 256.0 1.0 0 * 149 256.0 1.0 0 * 150 256.0 1.0 0 * 151 256.0 1.0 0 152 256.0 1.0 0 * 153 256.0 1.0 0 * 154 256.0 1.0 0 * 155 256.0 1.0 0 156 256.0 1.0 0 * 157 256.0 1.0 0 * 158 256.0 1.0 0 * 159 256.0 1.0 0 160 256.0 1.0 0 * 161 256.0 1.0 0 * 162 256.0 1.0 0 * 163 256.0 1.0 0 164 256.0 1.0 0 * 165 256.0 1.0 0 * 166 256.0 1.0 0 * 167 256.0 1.0 0 168 256.0 1.0 0 * 169 256.0 1.0 0 * 170 256.0 1.0 0 * 171 256.0 1.0 0 172 256.0 1.0 0 * 173 256.0 1.0 0 * 174 256.0 1.0 0 * 175 256.0 1.0 0 176 256.0 1.0 0 * 177 256.0 1.0 0 * 178 256.0 1.0 0 * 179 256.0 1.0 0 180 256.0 1.0 0 * 181 256.0 1.0 0 * 182 256.0 1.0 0 * 183 256.0 1.0 0 184 256.0 1.0 0 * 185 256.0 1.0 0 * 186 256.0 1.0 0 * 187 256.0 1.0 0 188 256.0 1.0 0 * 189 256.0 1.0 0 * 190 256.0 1.0 0 * 191 256.0 1.0 0 192 256.0 1.0 0 * 193 256.0 1.0 0 * 194 256.0 1.0 0 * 195 256.0 1.0 0 196 256.0 1.0 0 * 197 256.0 1.0 0 * 198 256.0 1.0 0 * 199 256.0 1.0 0 200 256.0 1.0 0 * 201 256.0 1.0 0 * 202 256.0 1.0 0 * 203 256.0 1.0 0 204 256.0 1.0 0 * 205 256.0 1.0 0 * 206 256.0 1.0 0 * 207 256.0 1.0 0 208 256.0 1.0 0 * 209 256.0 1.0 0 * 210 256.0 1.0 0 * 211 256.0 1.0 0 212 256.0 1.0 0 * 213 256.0 1.0 0 * 214 256.0 1.0 0 * 215 256.0 1.0 0 216 256.0 1.0 0 * 217 256.0 1.0 0 * 218 256.0 1.0 0 * 219 256.0 1.0 0 220 256.0 1.0 0 * 221 256.0 1.0 0 * 222 256.0 1.0 0 * 223 256.0 1.0 0 224 256.0 1.0 0 * 225 256.0 1.0 0 * 226 256.0 1.0 0 * 227 256.0 1.0 0 228 256.0 1.0 0 * 229 256.0 1.0 0 * 230 256.0 1.0 0 * 231 256.0 1.0 0 232 256.0 1.0 0 * 233 256.0 1.0 0 * 234 256.0 1.0 0 * 235 256.0 1.0 0 236 256.0 1.0 0 * 237 256.0 1.0 0 * 238 256.0 1.0 0 * 239 256.0 1.0 0 240 256.0 1.0 0 * 241 256.0 1.0 0 * 242 256.0 1.0 0 * 243 256.0 1.0 0 244 256.0 1.0 0 * 245 256.0 1.0 0 * 246 256.0 1.0 0 * 247 256.0 1.0 0 248 256.0 1.0 0 * 249 256.0 1.0 0 * 250 256.0 1.0 0 * 251 256.0 1.0 0 252 256.0 1.0 0 * 253 256.0 1.0 0 * 254 256.0 1.0 0 * 255 256.0 1.0 0 --- ----- ---- -- - --- ----- ---- -- - --- ----- ---- -- - --- ----- ---- -- Bin SNR Gain Bi - Bin SNR Gain Bi - Bin SNR Gain Bi - Bin SNR Gain Bi dB dB ts dB dB ts dB dB ts dB dB ts
325:(COFDM). In the context of G.992.1, the term "Discrete Multi-Tone" (DMT) is used instead, hence the alternative name of the standard, G.dmt. Using DMT is useful since it allows the communications equipment (user modem/router and exchange/DSLAM) to select only bins which are usable on the line thus effectively obtaining the best overall bit rate from the line at any given moment in time. With COFDM, a combined signal containing many frequencies (for each bin) is transmitted down the line. Fast Fourier Transform (and the inverse iFFT) is used to convert the signal on the line into the individual bins.
341:(PSK) is used to encode the bits within each bin. This is a complex and mathematical subject and will not be discussed further here. However, much research has been done on these modulation techniques and they are used for transmission because they allow the SNR to be improved, thus lowering the noise floor and enabling more reliable transmission of a signal with fewer errors. The gain obtainable above the noise floor can be anything from 0.5 to 1.5 dB and these small amounts make a vast difference when sending signals over long distance copper lines of 6 km or more.
200:
151:
is a North
American standard, G.992.1 (G.dmt) is an ITU (United Nations Telecom committee) standard. G.dmt is used most commonly today, throughout the world, but the ANSI standard was formerly popular in North America. There is a difference in framing between the two, and selecting the wrong standard
143:
DMT allocates from 2 to 15 bits per channel (bin). As line conditions change, bit swapping allows the modem to swap bits around different channels, without retraining, as each channel becomes more or less capable. If bit swapping is disabled then this does not happen and the modem needs to retrain in
382:
Below are examples of how the bin layout may look on various ADSL modems. Both show similar information and in each example there are 256 bins with a varied number of bits being encoded on each one. We can see that at around the frequency range of bin 33, the SNR is 40 dB with the bits per bin
364:
SNR may differ for each bin and this plays an important factor for deciding how many bits can be encoded reliably on it. Generally speaking, 1 bit can be encoded reliably for each 3 dB of available dynamic range above the noise floor within a transmission medium so, for example, a bin with an
273:
Discrete Multi-Tone (DMT), the most widely used modulation method, separates the ADSL signal into 255 carriers (bins) centred on multiples of 4.3125 kHz. DMT has 224 downstream frequency bins and up to 31 upstream bins. Bin 0 is at DC and is not used. When voice
232:
Modulation is the overlaying of information (or the signal) onto an electronic or optical carrier waveform. There are two competing and incompatible standards for modulating the ADSL signal, known as discrete multitone modulation (DMT) and
373:
Echo cancellation can be used so the downstream channel overlaps the upstream channel, or vice versa, meaning simultaneous upstream and downstream signals are sent. Echo cancellation is optional and is typically not used.
254:
is of more importance since it is attenuation which is the governing factor for line speed because attenuation rate over distance can vary significantly between various copper lines due to their quality and other factors.
308:
Typically, a few bins around 31-32 are not used in order to prevent interference between upstream and downstream bins either side of 138 kHz. These unused bins constitute a guard band to be chosen by each
140:(DMT). G.dmt full-rate ADSL expands the usable bandwidth of existing copper telephone lines, delivering high-speed data communications at rates up to 8 Mbit/s downstream and 1.3 Mbit/s upstream.
259:
is able to extend the reach of extremely long lines that have around 90 dB attenuation. Standard ADSL is only able to provide a service on lines with an attenuation no greater than about 75 dB.
520:
Relative capacity occupation (RCO) - Percentage of the attainable line bit rate that is in use. This takes into account interference on the line and the target noise margin at the remote DSLAM.
891:
281:
The centre frequency of bin N is (N x 4.3125) kHz. The spectrum of each bin overlaps that of its neighbours: it is not confined to a 4.3125 kHz wide channel. The orthogonality of
468:
Too many errors that cannot be corrected by the built in error correction would lead to the end user modem/router losing sync with the remote exchange (DSLAM or MSAN).
322:
282:
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349:
The quality of the line (how well it performs) at the frequency of the bin in question determines how many bits can be encoded within that bin. As with all
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Attenuation - How much signal is lost on the line (should be <56 dB downstream, <37 dB upstream)
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237:(CAP). CAP was the original technology used for DSL deployments, but the most widely used method now is DMT.
625:
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66:
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The graphs on the right summarise the speeds obtainable for each ADSL standard based on line
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can cause frame alignment errors every 5 or so minutes. Error correction is done using
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550:
ITU-T Recommendation G.992.1: Asymmetric digital subscriber line (ADSL) transceivers
172:
494:
246:
205:
523:
SES - Severely
Errored Seconds - after 10 seconds of ES we start counting SES
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Figures in brackets have been shown to provide a stable service in practice.
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Up to 15 bits per symbol can be encoded in a bin on a good quality line.
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278:) is used on the same line, then bin 7 is the lowest bin used for ADSL.
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For each 3 dB of SNR within a bin, 1 bit can be encoded reliably.
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can also increase the robustness of the line but increases latency.
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Attainable bit rates - Maximum speed line is capable of supporting
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56:
570:"G.992.1: Asymmetric digital subscriber line (ADSL) transceivers"
809:
781:
725:
192:
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manufacturer - it is not defined by the G.992.1 specification.
147:
There are 2 competing standards for DMT ADSL - ANSI and G.dmt;
420:(carrier channels) using frequencies above voice on the line.
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can be used on the lower frequency (upstream) bins to allow
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The bandwidth used by each bin overlaps neighbouring bins.
203:
Line rate obtainable (Mbit/s) against corresponding line
176:
Line rate obtainable (Mbit/s) against corresponding line
526:
UAS - Unavailable
Seconds - Seconds where we had no sync
497:- 12 dB or higher, for both downstream and upstream
321:
The use of bins produces a transmission system known as
317:
Coded orthogonal frequency-division multiplexing (COFDM)
365:
SNR of 18 dB would be able to accommodate 6 bits.
22:
Asymmetric digital subscriber line (ADSL) transceivers
833:
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42:
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503:DMT bits per bin - Shows which channels are in use
892:Telecommunications-related introductions in 1999
539:LOF - Loss of Framing - DSL frames don't line up
435:138–1104 kHz, 224 downstream bins (32–255).
323:coded orthogonal frequency-division multiplexing
304:138–1104 kHz, 224 downstream bins (32-255).
156:encoding and further protection can be used if
610:
8:
144:order to adapt to changing line conditions.
16:
423:The frequency layout can be summarised as:
291:The frequency layout can be summarised as:
715:
637:
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285:makes this possible without interference.
15:
432:25–138 kHz, 25 upstream bins (7–31).
301:25–138 kHz, 25 upstream bins (7-31).
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171:
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109:https://www.itu.int/rec/T-REC-G.992.1
7:
440:Bin N is centered on a frequency of
329:Reducing bit errors with QAM or PSK
513:- number of seconds that have had
14:
429:4–25 kHz, unused guard band.
298:4–25 kHz, unused guard band.
399:
580:from the original on 2021-04-12
335:quadrature amplitude modulation
160:encoding is used at both ends.
887:ITU-T G Series Recommendations
1:
295:30 Hz-4 kHz, voice.
138:discrete multitone modulation
235:Carrierless Amplitude Phase
908:
846:Ethernet in the first mile
478:to be used for downstream.
168:DMT history and line rates
378:DMT bits-per-bin examples
21:
345:Bin quality and bit rate
877:Digital subscriber line
626:Digital subscriber line
269:Bins (carrier channels)
506:CV - Coding violations
229:
196:
882:ITU-T recommendations
460:signal to noise ratio
383:being around 6 or 7.
359:signal-to-noise ratio
264:DMT technical details
202:
175:
856:Single Pair Ethernet
812:(early CAP variants)
426:0–4 kHz, voice.
353:, it depends on the
67:ITU-T Study Group 15
851:Long Reach Ethernet
731:ANSI T1.413 Issue 2
719:ANSI / ETSI / ITU-T
641:ANSI / ETSI / ITU-T
462:(SNR) for that bin.
458:, depending on the
18:
628:(DSL) technologies
529:LOS - Loss of Sync
395:Graphical with SNR
351:transmission lines
339:phase-shift keying
230:
197:
118:telecommunications
864:
863:
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794:G.fast and MGfast
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706:
472:Echo cancellation
369:Echo cancellation
124:(better known as
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91:telecommunication
73:Related standards
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100:Freely available
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653:HDSL2 and HDSL4
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511:Errored Seconds
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483:ADSL statistics
454:on each bin is
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43:Latest version
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132:standard for
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48:December 2003
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582:. Retrieved
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495:Noise margin
486:
476:all 256 bins
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459:
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452:bits encoded
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252:second graph
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162:Interleaving
154:Reed–Solomon
146:
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121:
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53:Organization
35:Year started
803:Proprietary
667:Proprietary
574:www.itu.int
355:attenuation
247:attenuation
206:attenuation
149:ANSI T1.413
871:Categories
787:deployment
763:G.lite.bis
712:Asymmetric
584:2021-04-12
556:References
442:N Ă— 4.3125
416:to create
333:A type of
699:DSL Rings
689:Etherloop
634:Symmetric
412:DMT uses
337:(QAM) or
180:(km) for
63:Committee
578:Archived
418:256 bins
128:) is an
30:In force
834:Related
775:Annex M
758:Annex L
753:Annex J
407:Summary
387:Textual
158:Trellis
105:Website
97:License
81:G.992.3
77:G.992.2
46:(12/03)
17:G.992.1
770:ADSL2+
741:G.lite
517:errors
250:. The
242:length
226:ADSL2+
213:) for
187:ADSL2+
178:length
136:using
87:Domain
27:Status
841:DSLAM
816:RADSL
748:ADSL2
736:G.dmt
684:MSDSL
658:SHDSL
536:power
509:ES -
414:COFDM
311:DSLAM
283:COFDM
257:ADSL2
220:ADSL2
126:G.dmt
57:ITU-T
821:UDSL
810:ADSL
726:ADSL
694:HVDL
679:SDSL
674:IDSL
648:HDSL
444:kHz.
357:and
276:POTS
244:and
223:and
215:ADSL
193:VDSL
190:and
182:ADSL
134:ADSL
38:1999
534:CPE
515:CRC
130:ITU
116:In
873::
576:.
572:.
361:.
217:,
211:dB
184:,
120:,
79:,
618:e
611:t
604:v
587:.
274:(
209:(
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