TR (draft) V0.0.0 (2004-xx)

Transcription

1 Technical Report Transmission and Multiplexing (TM); Spectral management on metallic access networks; Part 2: Technical methods or perormance evaluations Work Item Reerence Permanent Document DTS/TM TM6(01)20 Filename m01p20a6.pd (rev 6) Date eb 4, 2004 Rapporteur/Editor Rob F.M. van den Brink tel: (on behal o KPN) TNO Telecom ax: PO Box R.F.M.vandenBrink@telecom.tno.nl 2260 AK Leidschendam PO-Box 5050 Mark the new changes, valid since nov 24, GB Delt The Netherlands

2 2 Reerence DTS/TM Keywords spectral management, unbundling, access network, local loop, transmission, modem, POTS, IDSN, ADSL, HDSL, SDSL, VDSL, xdsl 650 Route des Lucioles F Sophia Antipolis Cedex - FRANCE Tel.: Fax: Siret N NAF 742 C Association à but non lucrati enregistrée à la Sous-Préecture de Grasse (06) N 7803/88 Important notice Individual copies o the present document can be downloaded rom: The present document may be made available in more than one electronic version or in print. In any case o existing or perceived dierence in contents between such versions, the reerence version is the Portable Document Format (PDF). In case o dispute, the reerence shall be the printing on printers o the PDF version kept on a speciic network drive within Secretariat. Users o the present document should be aware that the document may be subject to revision or change o status. Inormation on the current status o this and other documents is available at I you ind errors in the present document, send your comment to: editor@etsi.r Copyright Notiication No part may be reproduced except as authorized by written permission. The copyright and the oregoing restriction extend to reproduction in all media. European Telecommunications Standards Institute All rights reserved.

3 3 Contents Intellectual Property Rights...5 Foreword Scope Reerences Deinitions and abbreviations Deinitions Abbreviations Transmitter signal models or xdsl Generic transmitter signal model Cluster 2 transmitter signal models Transmitter signal model or "ISDN.2B1Q" Transmitter signal model or "ISDN.MMS.43" Cluster 3 transmitter signal models Transmitter signal models or "HDSL.2B1Q" Transmitter signal models or "HDSL.CAP" Transmitter signal model or "SDSL" Cluster 4 transmitter signal models Transmitter signal model or "ADSL over POTS" Transmitter signal model or "ADSL over ISDN" Transmitter signal model or "ADSL.FDD over POTS" Transmitter signal model or "ADSL.FDD over ISDN" Cluster 5 transmitter signal models Transmitter signal model or "VDSL" Generic receiver perormance models or xdsl Generic input models or eective SNR First order input model Second order input model (with residual distortion) Second order input model (with residual echo) Third order input model Generic detection models Generic Shited Shannon detection model Generic PAM detection model Generic CAP/QAM detection model Generic DMT detection model Generic models or echo coupling Linear echo coupling model Speciic receiver perormance models or xdsl Receiver perormance model or "HDSL.2B1Q" Receiver perormance model or "HDSL.CAP" Receiver perormance model or "SDSL" Receiver perormance model or "ADSL over POTS" (EC) Building blocks o the receiver perormance model Parameters o the receiver perormance model Receiver perormance model or "ADSL.FDD over POTS" Receiver perormance model or "ADSL over ISDN" (EC) Building blocks o the receiver perormance model Parameters o the receiver perormance model Receiver perormance model or "ADSL.FDD over ISDN Receiver perormance model or "VDSL" Transmission and relection models Summary o test loop models...27

4 4 8 Cross talk models Overview o dierent network topologies Validity limitations o cross talk modeling Generic cross talk models or two-node co-location Basic diagram or two-node topologies Models or cross talk cumulation FSAN sum or cross talk cumulation Models or cross talk coupling Basic models or equivalent NEXT and FEXT Models or cross talk injection Forced noise injection Current noise injection Generic cross talk models or multi-node co-location Measurement methods Examples o evaluating various scenarios Example scenario A Assumed coniguration Assumed conditions Evaluated perormance or scenario A Example scenario B Example scenario C Example scenario D...34 Annex A: Bibliography...34 History...35

5 5 Intellectual Property Rights IPRs essential or potentially essential to the present document may have been declared to. The inormation pertaining to these essential IPRs, i any, is publicly available or members and non-members, and can be ound in SR : "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notiied to in respect o standards", which is available rom the Secretariat. Latest updates are available on the Web server ( Pursuant to the IPR Policy, no investigation, including IPR searches, has been carried out by. No guarantee can be given as to the existence o other IPRs not reerenced in SR (or the updates on the Web server) which are, or may be, or may become, essential to the present document. Foreword This Technical Report (TR) has been produced by Technical Committee Transmission and Multiplexing (TM). The present document is part 2 o a multi-part deliverable covering Transmission and Multiplexing (TM); Acces networks; Spectral management on metallic access networks, as identiied below: Part 1: Part 2: Part 3: "Deinitions and signal library". "Technical methods or perormance evaluations. "Construction methods or spectral management rules. NOTE: Part 3 is under preparation.

6 6 1 Scope The present document gives guidance on a common methodology or studying the impact on xdsl perormance (maximum reach, noise margin, maximum bitrate) in noisy cables when changing parameters within various Spectral Management scenarios. These methods enable reproducible results and a consistent presentation o the assumed conditions (characteristics o cables and xdsl equipment) and coniguration (choosen technology mixture and cable ill) o each scenario. The technical methods include computer models or calculating: xdsl receiver capability o detecting signals under noisy conditions; xdsl transmitter characteristics; cable characteristics cross talk cumulation in cables, originating rom a mix o xdsl disturbers; The objective is to provide the technical means or evaluating the perormance o xdsl equipment within a chosen scenario, such as calculations and measurements. This includes the description o perormance properties o equipment. Another objective is to assist the reader with applying this methodology by providing examples on how to speciy the coniguration and the conditions o a scenario in an unambiguous way. The distinction is that a coniguration o a scenario can be controlled by access rules while the conditions o a scenario cannot. Possible applications o this document include: Studying access rules, or the purpose o bounding the cross talk in unbundled networks. Studying deployment rules, or the various systems present in the access network. Studying the impact o cross talk on various technologies within dierent scenarios The scope o this Spectral Management document is explicitly restricted to the methodology or deining scenarios and quantiying the perormance o equipment within such a scenario. All judgement on what access rules are required, what perormance is acceptable, or what combinations are spectral compatible, is explicitly beyond the scope o this document. The same applies or how realistic the example scenarios are. 2 Reerences For the purposes o this Technical Report (TR) the ollowing reerences apply: SpM ISDN [1] TR " Transmission and Multiplexing (TM); Spectral Management on metallic access networks; Part 1: Deinitions and signal library V1.3.1 ( ), dec [2] ANSI T1E1.4/ R6 "Spectrum Management or loop transmission systems" drat; revision 6, November 2000 (or a more recent version) [3] TS (V1.3.2): "Transmission and Multiplexing (TM); Integrated Services Digital Network (ISDN) basic rate access; Digital transmission system on metallic local lines".

7 7 HDSL SDSL ADSL [4] TS (V1.5.3): "Transmission and Multiplexing (TM); High bit-rate Digital Subscriber Line (HDSL) transmission systems on metallic local lines; HDSL core speciication and applications or combined ISDN-BA and kbit/s transmission". [5] TS , v1.1.3: "Transmission and Multiplexing (TM); Access transmission system on metallic access cables; Symmetrical single pair high bitrate Digital Subscriber Line (SDSL)". Nov [6] ITU-T Recommendation G (2001): "Single-Pair High-Speed Digital Subscriber Line (SHDSL) transceivers". [7] TS , v1.3.1, ( ): "Transmission and Multiplexing (TM); Access transmission systems on metallic access cables; Asymmetric Digital Subscriber Line (ADSL) - European speciic requirements", may [8] ITU-T Recommendation G (1999): "Asymmetric digital subscriber line (ADSL) transceivers". 3 Deinitions and abbreviations 3.1 Deinitions ED NOTE When the deinitions added to SpM part 3 have been agreed by -TM6, and moved rom the living list to the drat o SpM-3, then these deinitions will be included here as well. For the purposes o the present document, the ollowing terms and deinitions apply: upstream transmission: transmission direction rom an NT-port to an LT-port, usually rom the customer premises, via the access network, to the telecommunication exchange downstream transmission: transmission direction rom an LT-port to an NT-port, usually rom the telecommunication exchange via the access network, to the customer premises Noise margin: the ratio by which the received noise may increase until the recovered signal does not meet the predeined quality criteria. This ratio is commonly expressed in db. Signal margin: the ratio by which the received signal may decrease until the recovered signal does not meet the predeined quality criteria. This ratio is commonly expressed in db. Max datarate: the maximum data rate that can be recovered according to predeined quality criteria, when the received noise is increased with a choosen noise margin (or the received signal is decreased with a choosen signal margin). Loop provider: company acilitating access to the local loop wiring. (In several cases the loop provider is historically connected to the incumbent network operator, but other companies may serve as loop provider as well) Network operator: company that makes use o a local loop wiring or transporting telecommunication services. This deinition covers incumbent as well as competitive network operators.

8 8 Access Rule (or metallic access rule): Mandatory rule or achieving access to the local loop wiring, equal or all network operators that make use o the same network cable, that bounds the cross talk in that network cable. Deployment Rule: Voluntary rule, irrelevant or achieving access to the local loop wiring and proprietary or each individual network operator. A deployment rule relects a network operators own view about what the maximum length or maximum bitrate may be or oering a speciic transmission service to ensure a chosen minimum quality o service. 3.2 Abbreviations For the purposes o the present document, the ollowing abbreviations apply: ADSL BER CAP DMT FDD HDSL ISDN LT-port LTU NT-port NTU PAM PSD QAM REC SDSL SNR TRA VDSL xdsl 2B1Q Asymmetric Digital Subscriber Line Bit Error Ratio Carrierless Amplitude/Phase modulation Discrete Multitone modulation Frequency Division Duplexing/Duplexed High bit rate Digital Subscriber Line Integrated Services Digital Network Line Termination port (commonly at central oice side) Line Termination Unit Network Termination port (commonly at customer side) Network Termination Unit Pulse Amplitude modulation Power Spectral Density (single sided) Quadrature Amplitude modulation Receiver Symmetrical (single pair high bitrate) Digital Subscriber Line Signal to Noise Ration (ratio o powers) Transmitter Very-high-speed Digital Subscriber Line (all systems) Digital Subscriber Line 2-Binary, 1-Quarternairy (Special variant o a 4-level PAM linecode) 4 Transmitter signal models or xdsl A transmitter model in this clause is mainly a PSD description o the transmitted signal under matched conditions, plus an output impedance description to cover mis-matched conditions as well. PSD masks o transmitted xdsl signals are speciied in several documents or various purposes, or instance in Part 1 o Spectral Management [1]. These PSD masks, however, cannot be applied directly to the description o a transmitter model. One reason is that masks are speciicing an upper limit, and not the expected (averaged) values. Another reason is that the deinition o the true PSD o a time limited signal requires no resolution bandwidth at all (it is deined by means o an autocorrelation, ollowed by a Fourier transorm) while PSD masks do rely on some resolution bandwidth. They describe values that are (a slightly) dierent rom the true PSD, especially at steep edges (e.g. guard bands), and or modeling purposes this dierence is sometimes very relevant. To dierentiate between several PSD descriptions, masks and templates o a PSD are given a dierent meaning. Masks are intended or proving compliance to standard requirements, while templates are intended or modeling purposes. This clause summarizes various xdsl transmitter models, by deining template spectra o output signals.

9 9 4.1 Generic transmitter signal model A generic model o an xdsl transmitter is essentially a linear signal source. The Thevenin equivalent o such a source equals an ideal voltage source U s having a real resistor R s in series. The output voltage o this source is random in nature (as a unction o the time), is uncorrelated with any other transmitter signal, and occupies a relatively broad spectrum. This generic model can be made speciic by deining: The output impedance R s o the transmitter. The template o the PSD, measured at the output port, when terminated with an external impedance equal to R s. This is identiied as the matched condition, and under these conditions the output power equals the maximum power that is available rom this source. Under all other (mis-matched) termination conditions the output power will be lower. 4.2 Cluster 2 transmitter signal models Transmitter signal model or "ISDN.2B1Q" The PSD template or modeling the "ISDN.2B1Q" transmit spectrum is deined by the theoretical sinc-shape o PAM encoded signals, with additional iltering and with a noise loor. The PSD is the maximum o both power density curves, as summarized in expression 1 and the associated table 1. The coeicient q N scales the total signal power o P 1 () to a value that equals P ISDN. This value is dedicated to the used ilter characteristics, but q N =1 when no iltering is applied ( L 0, H ). The source impedance equals 135Ω. P ( ) = P 1 ISDN 2 q X N 2 sinc X 1+ 1 H 2 N H 1 1+ L 2 [ W / Hz] 10 P ( ) = 2 ( Ploor _ dbm /10) 1000 [ W / Hz] P( ) = max Where: ( P ( ), P ( )) [ W / Hz] 1 ( 10 ) P /10 ISDN _ dbm 1000 P = [W] ISDN 2 R S = 135 [Ω ] sinc(x) = sin(π x) / (π x) Deault values or remaining parameters are summarized in table 1. Expression 1: PSD template or modeling "ISDN.2B1Q" signals. Dierent ISDN implementations, may use dierent ilter characteristics, and noise loor values. Table 1 speciies deault values or ISDN implementations, in case 2 nd order Butterworth iltering has been applied. The deault noise loor equals the maximum PSD level that meets the out-o-band speciication o the ISDN standard [3]. In case these deault values are not appropriated or speciic perormance studies, other values may apply as well (provided that they are speciied or these studies).

10 10 Type X H L N H q N P ISDN_dBm P loor_dbm [khz] [khz] [khz] [dbm] [dbm/hz] ISDN.2B1Q 80 1 x Table 1: Deault parameter values or the ISDN.2B1Q templates, as deined in expression 1. These deault values are based on 2 nd order Butterworth iltering Transmitter signal model or "ISDN.MMS.43" <or urther study> 4.3 Cluster 3 transmitter signal models Transmitter signal models or "HDSL.2B1Q" The PSD templates or modeling the spectra o various "HDSL.2B1Q" transmitters is deined by the theoretical sincshape o PAM encoded signals, with additional iltering and a noise loor. The PSD template is the maximum o both power density curves, as summarized in table 2. The coeicient q N scales the total signal power o P 1 () to a value that equals P 0. This value is dedicated to the used ilter characteristics, but equals q N =1 when no iltering is applied ( L 0, H ), The source impedance equals 135Ω. P ( ) = P 1 HDSL 2 q X N 2 sinc X 1 1+ L H1 2 N H H 2 2 N H 2 [ W / Hz] 10 P ( ) = 2 ( Ploor _ dbm /10) 1000 [ W / Hz] P( ) = max Where: ( P ( ), P ( )) 1 ( 10 ) P /10 HDSL _ dbm 1000 P = [W] HDSL 2 R S = 135 [Ω ] sinc(x) = sin(π x) / (π x) Deault values or remaining parameters are summarized in table 2. Expression 2: PSD template or modeling "HDSL.2B1Q" signals. [ W / Hz] Dierent HDSL implementations, may use dierent ilter characteristics, and noise loor values. Table 2 summarizes deault values or modeling HDSL transmitters, and alternative values in case higher order Butterworth iltering has been applied to dedicated implementations. It is recommended to use the deault values or spectral management studies, unless motivated why alternative values are more appropriated. The deault power level P HDSL equals the maximum power allowed by the HDSL standard [4], since a nominal speciication does not exist. The deault noise loor P loor equals a value observed or various implementations. When these measurements were not available, the maximum PSD level was chosen here that meets the out-o-band speciication o the HDSL standard [4].

11 11 Deault Type X L P loor_dbm dbm/hz H1 N H1 H2 N H2 q N P HDSL_dBm khz khz dbm HDSL.2B1Q/ x 3 N/A N/A HDSL.2B1Q/ x 3 N/A N/A HDSL.2B1Q/ x 3 N/A N/A Alternatives Type X L H1 N H1 H2 N H2 q N P HDSL_dBm khz khz dbm H2.1 HDSL.2B1Q/ x 4 N/A N/A H2.2 HDSL.2B1Q/ x x P loor_dbm dbm/hz Table 2: Deault parameter values or the HDSL.2B1Q templates, as deined in expression 2. The alternative values are based on higher order Butterworth iltering. Choose H2 = and N H2 =1 when not applicable (N/A) Transmitter signal models or "HDSL.CAP" The PSD templates or modeling signals generated by HDSL.CAP transmitters are dierent or single-pair and two-pair HDSL systems. The PSD templates or modeling the "HDSL.CAP/2" and "HDSL.CAP/1" transmit spectra or two-pair and single-pair systems are deined in terms o break requencies, as summarized in table 3. These template are taken rom the nominal shape o the transmit signal spectra, as speciied in the HDSL standard [4] The associated values are constructed with straight lines between these break requencies, when plotted against a logarithmic requency scale and a linear dbm scale. The source impedance equals R s =135Ω. HDSL.CAP/2 2 pair HDSL.CAP/1 1- pair 135 Ω 135 Ω [Hz] [dbm/hz] [Hz] [dbm/hz] ,98 k -57 <TBD> <TBD> 21,5 k ,02 k ,58 k ,10 k ,62 k ,00 k -90 1,188 M M -120 Table 3. PSD template values at break requencies or modeling "HDSL.CAP/2" and "HDSL.CAP/1" NOTE: A PSD template or HDSL.CAP/1 is currently or urther study Transmitter signal model or "SDSL" The PSD templates or modeling the spectra o "SDSL" transmitters is deined by the theoretical sinc-shape o PAM encoded signals, plus additional iltering and a noise loor. The transmit spectrum is deined in three distinct requency bands, as summarized in expression 3 and the associated table 4. The break requency int is the requency where the curves or P 1 () and P 2 () intersect. This PSD template is taken rom the nominal shape o the transmit signal spectrum, as speciied in the SDSL standard [5]. The source impedance equals R s =135Ω.

12 12 < int : K sdsl P1 ( ) = R s X 2 sinc X N H ( ) 1 ( L + ) H 2 [ W / Hz] int 1,5 MHz : P ( ) = K 2 x 0 1,5 [ W / Hz] > 1,5MHz : P ( ) = [ dbm / Hz] R s = 135 Ω sinc(x) = sin(π x) / (π x) int = is the lowest requency above H where the expressions or P 1() and P 2() intersect Parameter values are deined in table 4 Expression 3. PSD Tempate values or modeling both the symmetric and asymmetric modes o SDSL Mode Data Rate R TRA Symbol Rate sym X H L 0 N H K SDSL K X [kb/s] [kbaud] [khz] [Hz] [V 2 ] [W/Hz] Sym < 2048 both (R+ 8 kbit/s)/3 sym X/ Sym 2048 both (R+ 8 kbit/s)/3 sym X/ Asym 2048 LTU (R+ 8 kbit/s)/3 2 sym x 2/ Asym 2048 NTU (R+ 8 kbit/s)/3 sym x 1/ Asym 2304 LTU (R+ 8 kbit/s)/3 2 sym x 3/ Asym 2304 NTU (R+ 8 kbit/s)/3 sym x 1/ Table 4. Parameter values or the SDSL templates, as deined in expression Cluster 4 transmitter signal models Transmitter signal model or "ADSL over POTS" <or urther study> Transmitter signal model or "ADSL over ISDN" <or urther study> Transmitter signal model or "ADSL.FDD over POTS" <or urther study> Transmitter signal model or "ADSL.FDD over ISDN" 4.5 Cluster 5 transmitter signal models Transmitter signal model or "VDSL" <or urther study>

13 13 5 Generic receiver perormance models or xdsl A receiver perormance model is capable o predicting up to what perormance a data stream can be recovered rom a noisy signal. In all cases it assumes that this recovery meets predeined quality criteria such as a maximum BER (Bit Error Ratio). Values like BER<10 7, during a time interval o several minutes, are not uncommon. The word perormance reers within this context to a variety o quantities, including noise margin, signal margin and max data rate. When the receiver is ideal (zero internal receiver noise, ininite echo cancellation, etc), quantities like noise margin and signal margin become equal. Perormance models are implementation and line code speciic. Perormance modeling becomes more convenient when broken down into a cascade o smaller sub models: A line code independent input (sub)model that evaluates the eective SNR rom received signal, received noise, and various receiver imperections. Details are described in clause 5.1. A line code dependent detection (sub)model that evaluates the perormance (e.g. the noise margin at speciied bit rate) rom the eective SNR. Details are described in clause 5.2. An echo coupling (sub)model that evaluates what portion o the transmitted signal lows into the receiver. Details are described in clause 5.3. This clause details all the above mentioned sub models, being used or evaluating the perormance o receivers under noise conditions. This clause 5 is dedicated to generic perormance models only. Clause 6 is dedicated to speciic models by assigning values to all parameters o a generic model. 5.1 Generic input models or eective SNR An input (sub) model describes how to evaluate the eective SNR, as intermediate result (see igure 1), rom various input quantities and imperections. received signal P RS received noise P RN input block Eective SNR detection block echo P RE transmitted signal echo coupling P TS Transmitter block (or opposite direction) xdsl transceiver Figure 1: Flow diagram o a transceiver model, build up rom individual sub models.

14 14 On input, the input model or eective SNR requires values or signal, noise and echo. The low diagram in igure 1 illustrates this or an xdsl transceiver that is connected via a common wire pair to another transceiver (not shown). The received signal power P RS carries the data that is to be recovered. This signal originates rom the transmitter at the other side o the wire pair, and its level is attenuated by cable loss. The received noise power P RN is all that is received when the transmitters at both sides o the link under study are silent. The origin o this noise is mainly cross talk rom internal disturbers connected to the same cable (cross talk noise), and partly rom external disturbers (ingress noise). The received echo power P RE is all that is received when the transmitter at the other end o the wire pair is silent, as well as all internal and external disturbers. It is a residue that will be received when a transmitter and a receiver are combined into a transceiver en co-connected via a hybrid to the same wire pairs. When the hybrid o that transceiver is unbalanced due to mismatched termination impedances (o the cable), then a portion (P RE ) o the transmitted signal (P TS ) will leak into the receiver and is identiied as echo. On output, the input model evaluates a quantity called eective SNR (Signal to noise Ratio) that indicates to what degree the received signal is deteriorated by noise, residual echo and all kinds o implementation imperections. Due to signal processing in the receiver, the input SNR (the ratio between signal power, and the power-sum o noise and echo) will change into the eective SNR at some virtual internal point at the receiver. The eective SNR can be better or worse then the input SNR. Receivers with build-in echo cancellation can take advantage o a-priori knowledge on the echo, and can suppress most o this echo and thus improving the eective SNR. On the other hand, all analog receiver electronics produce shot noise and thermal noise, the A/D-converter produces quantization noise, and the equalization has its limitations as well. The combination o all these individual imperections deteriorates the eective SNR. In principle all parameters o the eective SNR can be assumed as requency dependent, but this dependency has oten been omitted here or reasons o simplicity. In addition, external change o signal and noise levels will modiy the value o this eective SNR. Eective SNR, in oset ormat or margin evaluations To simpliy urther analysis o perormance quantities like noise margin and signal margin, the eective SNR is oten expressed in its oset ormat, characterized by an additional parameter m. The associated expression is deined or each model individually. With this parameter m the external noise level can be increased (or noise margin calculations) or the external signal level can be decreased (or signal margin calculations). The convention is that when m=1 (equals zero db) the eective oset SNR equals the eective SNR itsel. When the value o parameter m increases, the eective oset SNR decreases First order input model This input model is quite a simpliied model that assumes that the SNR o the input signal is internally modiied by internal receiver noise (P RN0 ). Most imperections o the receiver (such as imperect echo suppression, imperect equalization and quantization noise) are assumed to be concentrated in a single virtual internal noise source (P RN0 ). Figure 2 shows the low diagram o an xdsl transceiver model that incorporates a linear irst order model or eective SNR evaluation.

15 15 received signal P RS (First order) input model Receiver Eective received noise P RN SNR detection block P RN0 internal receiver noise transmitted signal P TS Transmitter block (or opposite direction) xdsl transceiver Figure 2: Flow diagram o a transceiver model that incorporates a linear irst order input model or the determination o the eective SNR. Expression 4 summarizes how to evaluate the eective SNR or this model, and it has been speciied in plain and oset ormats. Table 5 summarizes the involved parameters. Plain ormat: SNR() = Noise oset ormat: SNR os,n(m, ) = Signal oset ormat: SNR os,s(m, ) = P P RN RN P RS + P P RN 0 RS m + P PRS / m P + P Expression 4: Eective SNR, in various ormats, or a irst order input model RN RN 0 RN 0 Input quantities linear In db remarks Received signal power P RS 10 log 10(P RS) Frequency dependent Received crosstalk noise P RN 10 log 10(P RN) External noise Model Parameters Receiver noise power P RN0 10 log 10(P RN0) Internal noise Output quantities Signal to noise ratio (eective) SNR 10 log 10(SNR) Frequency dependent Table 5: Involved parameters and quantities or a irst order input model Second order input model (with residual distortion) <or urther study> Second order input model (with residual echo) <or urther study; may be removed>

16 Third order input model <or urther study; may be removed> 5.2 Generic detection models This clause identiies several generic (sub) models or the detection block: one line code independent model derived rom the Shannon capacity limit, and various line code dependent models dedicated to PAM, CAP/QAM or DMT line coding. Table 6 summarizes the naming convention or input and output quantities. Input quantities linear In db remarks Signal to Noise Ratio SNR 10 log 10(SNR) Ratio o powers (requency dependent) Output quantities Noise margin m n 10 log 10(m n) Ratio o noise powers Signal margin m s 10 log 10(m s) Ratio o signal powers Table 6. Symbols used or input and output quantities o detection models On input, the detection block requires an eective SNR, as provided by the input block. This SNR is a unction o the requency. When the oset ormat is used or describing the SNR, it will also be a unction o the oset parameter m.this oset ormat is speciied individually or each model in clause 5.1. On output, the detection block evaluates a signal margin m n (or a noise margin m s when more appropriated). This margin parameter is a dominant measure or the transport quality that is achieved under noisy conditions. The Noise Margin m n indicates how much the received noise power can increase beore the transmission becomes unreliable. The Signal Margin m s indicates how much the received signal power can decrease beore the transmission becomes unreliable. Unless explicitly speciied otherwise, the word margin reers in this document to noise margin. NOTE From an xdsl deployment point o view, the analysis o noise margin is preerred over signal margin, since the (cross talk) noise is the quantity that may increase when more systems are connected to the same cable. Many xdsl implementations, however, do report margin numbers that are not exactly equal to this noise margin, since the detection circuitry cannot make a distinction between external noise (due to cross talk) and internal noise (due to imperect electronics). These margins are oten an estimate closer in value to the signal margin then the noise margin.

17 Generic Shited Shannon detection model The calculation o the margin m using the generic Shited Shannon detection model, is equivalent with solving the equation in expression 5. It has been derived rom Shannon's capacity theorem, by reducing the eective SNR ("shiting" on a db scale) by the SNR-gap Γ, to account or the imperections o practical detectors. The associated parameters are summarized in table 7. The eective SNR is to be evaluated by using one o the input models described in clause 5.1. Depending on what oset ormat is used or the SNR expression (see clause 5.1), the calculated margin m will represent the noise margin m n or the signal margin m s. b + B / 2 c = B / 2 c SNRos log 2 1+ Γ ( m, ) d Expression 5: Equation o the Shited Shannon detection model, or solving the margin m. Model Parameters linear In db remarks SNR gap Γ 10 log 10(Γ) Data rate d all payload bits that are transported in 1 sec Line rate b = DateRate + overhead bitrate Bandwidth B Width o most relevant spectrum Table 7. Parameters used or Shited Shannon detection models. The various parameters used within this generic detection model are summarized in table 7. The model can be made speciic by assigning values to all these model parameters. The SNR-gap (Γ) is a perormance parameter that indicates how close the detection approaches the Shannon capacity limit. The linerate is usually higher then the data rate (0 30%) to transport overhead bits or error correction, signaling and raming. The Bandwidth is a parameter that indicates what portion o the received spectrum is relevant or data transport. The model assumes that this portion passes the receive ilters Generic PAM detection model The calculation o the margin m using the generic PAM detection model is equivalent with solving the equation in expression 6. This model assumes ideal decision eedback equalizer (DFE) margin calculations. The associated parameters are summarized in table 8. The eective SNR is to be evaluated by using one o the input models described in clause 5.1. Depending on what oset ormat is used or the SNR expression (see clause 5.1), the calculated margin m will represent the noise margin m n or the signal margin m s. SNR req s N H 2 b = Γ ( ) = exp ln1+ SNRos ( m, + n s ) s 0 n= N L d Expression 6: Equation o the PAM-detection model, or solving the margin m.

18 18 The SNR gap Γ, being used in the above expression 6, is a combination o various eects. This Γ parameter is oten split-up into the ollowing three parts: Its theoretical value Γ PAM (in the order o 9.75 db, at BER=10 7 ) A theoretical coding gain Γ coding (usually in the order o 3-5 db), to indicate how much additional improvement is achieved by the chosen coding mechanism. An empirical implementation loss Γ impl (usually 1.6 db or more), indicating how much overall deterioration is caused by implementation dependent imperections in echo cancellation, equalization, etc, without identiying its true cause. When Γ is split-up into the above three parts, its value shall be evaluated as ollows: SNR gap (linear): Γ = Γ PAM / Γ coding Γ impl SNR gap (in db): Γ _db = Γ PAM_dB Γ coding_db + Γ impl_db Model Parameters linear In db remarks SNR gap (eective) Γ 10 log 10(Γ) = SNR req / (2 2 b 1) SNR gap in parts: Γ PAM 10 log 10(Γ PAM) Modulation gap or PAM Γ coding 10 log 10(Γ coding) Coding gain Γ impl 10 log 10(Γ impl) Implementation loss Required SNR SNR req 10 log 10(SNR req) = Γ (2 2 b 1) Data rate d all payload bits that are transported in 1 sec Line rate b = DateRate + overhead bitrate Symbol rate s = b / b Bits per symbol b = b / s (can be non-integer) Summation range N L, N H On deault: N L= 2 and N H=+1 Table 8. Parameters used or PAM detection models. The various parameters in table 8 used within this generic detection model have the ollowing meaning: The SNR-gap (Γ) and required SNR (SNR req ) are equivalent parameters and can be converted rom one to the other. The advantage o using Γ over SNR req is that Γ can be deined with similar meaning or all theoretical models in the requency domain (Shited Shannon, CAP, PAM, DMT). The advantage o using SNR req over Γ is that this quantity is closer related to the SNR observed at the decision point o the detection circuitry. The line rate is usually higher then the data rate (0 30%) to transport overhead bits or error correction, signaling and raming. The symbol rate is the line rate divided by the number o bits packed together in a single symbol. The summation range or n is rom N L to N H, and this range has to be deined to make this generic model speciic. Commonly used values or PAM, using over sampling, are N L = 2 and N H =+1. This correspond to T/3-spaced equalization. Wider ranges are not excluded.

19 Generic CAP/QAM detection model The calculation o the margin m using the generic CAP/QAM detection model is equivalent with solving the equation in expression 7. This model assumes ideal decision eedback equalizer (DFE) margin calculations. The associated parameters are summarized in table 9. The eective SNR is to be evaluated by using one o the input models described in clause 5.1. Depending on what oset ormat is used or the SNR expression (see clause 5.1), the calculated margin m will represent the noise margin m n or the signal margin m s. SNR req s N H b ( ) 1 Γ 2 1 = exp ln1+ SNRos ( m, + n s ) s 0 n= N L d Expression 7: Equation o the CAP/QAM-detection model, or solving the margin m. The (eective) SNR gap Γ, being used in the above expression 7, is a combination o various eects. This Γ parameter is oten split-up into the ollowing three parts: Its theoretical value Γ CAP (in the order o 9.8 db or BER=10-7 ) A theoretical coding gain Γ coding (usually in the order o 3-5 db), to indicate how much additional improvement is achieved by the chosen coding mechanism. An empirical implementation loss Γ impl (usually 1.6 db or more), indicating how much overall deterioration is caused by implementation dependent imperections in echo cancellation, equalization, etc, without identiying its true cause. When Γ is split-up into the above three parts, its value shall be evaluated as ollows: SNR gap (linear): Γ = Γ CAP / Γ coding Γ impl SNR gap (in db): Γ _db = Γ CAP_dB Γ coding_db + Γ impl_db Model Parameters linear In db remarks SNR gap (eective) Γ 10 log 10(Γ) = SNR req / (2 b 1) SNR gap in parts: Γ CAP 10 log 10(Γ PAM) Modulation gap or CAP/QAM Γ coding 10 log 10(Γ coding) Coding gain Γ impl 10 log 10(Γ impl) Implementation loss Required SNR SNR req 10 log 10(SNR req) = Γ (2 b 1) Data rate d all payload bits that are transported in 1 sec Line rate b = DateRate + overhead bitrate Symbol rate s = b / b Bits per symbol b = b / s (can be non-integer) Summation range N L, N H On deault: N L=0 and N H=+3 Table 9. Parameters used or CAP/QAM detection models. The various parameters in table 9 used within this generic detection model have the ollowing meaning: The SNR-gap (Γ) and required SNR (SNR req ) are equivalent parameters and can be converted rom one to the other. The advantage o using Γ over SNR req is that Γ can be deined with similar meaning or all theoretical models in the requency domain (Shannon, CAP, PAM, DMT). The advantage o using SNR req over Γ is that this quantity is closer related to the SNR observed at the decision point o the detection circuitry. The line rate is usually higher then the data rate (0..30%), to transport overhead bits or error correction, signaling and raming. The symbol rate is the line rate divided by the number o bits packed together in a single symbol.

20 20 The summation range or n is rom N L to N H, Commonly used values or CAP/QAM systems using over sampling are N L =0 and N H =+3. This holds when the carrier requency positions the spectrum low in the requency band (e.g. CAP-based HDSL). Other values may be more appropriated when the carrier requency moves the spectrum to higher requencies (e.g CAP based VDSL) Generic DMT detection model <let or urther study> 5.3 Generic models or echo coupling Linear echo coupling model ED. NOTE This text was moved rom clause 7.2, because it is more appropriated, and a slightly rephrased or clarity. The modeling o echo in general is subject o discussion within -TM6, and may be kept out completely o SpM-2 when TM6 has come to a conclusion. This model describes a property o linear hybrids in transceivers, and models what portion o the transmitted signal relects directly into the receiver. The hybrid is characterized by two parameters: R V, representing the output impedance o the transceiver. Commonly used values are the design impedances o the modems under test, including as 100Ω or ADSL and 135Ω or SDSL. Z B, representing the termination impedance that causes that the hybrid is perectly balanced. This means that when the hybrid is terminated with this "balance impedance", no echo will low into the receiver. For welldesigned hybrids, this balance impedance is a "best guess" approximation o the "average" impedance o cables being used. Figure 3 shows an equivalent circuit diagram o the above hybrid, represented as a Wheatstone bridge. The associated transer unction H E (jω) expresses what portion o the transmit signal will appear as echo. U S R V U E + R V + H E U ( jω) = U E T Z B = 1 R + Z V B U U S T ( Z = ( R L V Z Z B B ) R ) Z V L Z B U T Z L P P RE = TS H E ( jω) 2 Figure 3: Flow diagram o the basic model or echo loss. The identiiers P RE and P TS reer to power low values used in igure 1. When using this basic model or echo loss in a ull simulation, value R V can be made equal to the design impedance o the modem under test, and value Z B can be made equal to the complex and requency dependent input impedance o the cable, terminated at the other cable end with a load impedance equal to R V. Values or R V and Z B are implementation speciic.

21 21 6 Speciic receiver perormance models or xdsl This clause 6 deines parameter values or the generic perormance models o the previous clause 5, to provide speciic models or various xdsl modems. 6.1 Receiver perormance model or "HDSL.2B1Q" <let or urther study> 6.2 Receiver perormance model or "HDSL.CAP" This calculation model is capable or predicting a perormance that is benchmarked against the perormance requirements o an compliant HDSL-CAP modem [4]. The reach predicted by this model, under the stress conditions (loss, noise) o the associated the HDSL speciication [4], is close to the reach required by that speciication Building blocks o the receiver perormance model. The receiver perormance model or compliant HDSL-CAP is build-up rom the ollowing building blocks: A irst order (linear) input model or the input block, speciied in clause 5.1.1, that combines all imperections (ront-end noise, residual echo, equalization errors), in one virtual noise source. The generic CAP/QAM detection model, speciied in clause The parameter values speciied in table 10 o the succeeding clause. Parameters, o the receiver perormance model. The parameter values, used in the receiver perormance model or compliant HDSL-CAP, are summarized in table 10. Parts o them are directly based on HDSL speciications. The remaining values are based on theory, ollowed by an iterative it o the model to meet the reach requirements or HDSL-CAP under the associated stress conditions. Various parameters are derived directly rom the above-mentioned parameters. Their purpose is to simpliy the required expression o the used CAP/QAM-detection model.

22 22 Model Parameter HDSL.CAP/2 HDSL.CAP/1 SNR-Gap (eective) Γ _db 6.8 db 6.8 db SNR-Gap in parts Γ CAP_dB <TBD> <TBD> Γ coding_db <TBD> <TBD> Γ impl_db <TBD> <TBD> Receiver noise P RN0_dB 105 dbm 105 dbm Data rate d kb/s kb/s Line rate b 1168 kb/s 2330 kb/s Carrier requency c khz khz bits per symbol b 5 6 N H N L Summation bounds in the CAP/QAM model Derived Parameter Required SNR SNR req Γ (2 b -1) Γ (2 b -1) SNR req_db 21.7 db 24.8 db Symbol rate s b / b = kbaud b / b = kbaud Table 10. Values or the parameters o the perormance model, obtained rom requirements or HDSL-CAP [4]. 6.3 Receiver perormance model or "SDSL" This calculation model is capable or predicting a perormance that is benchmarked against the perormance requirements o an compliant SDSL modem [5]. The reach predicted by this model, under the stress conditions (loss, noise) o the associated the SDSL speciication [5] is close to the reach required by that speciication. Deviations o predictions and requirements are less then 4.5% in reach, and less then 125m. The validity o the predicted perormance holds or a wider range o stress conditions Building blocks o the receiver perormance model. The receiver perormance model or compliant SDSL is build-up rom the ollowing building blocks: A irst order (linear) input model or the input block, speciied in clause 5.1.1, that combines all imperections (ront-end noise, residual echo, equalization errors), in one virtual noise source. The generic PAM detection model, speciied in clause The parameter values speciied in table 11 o the succeeding clause. Parameters, o the receiver perormance model. The parameter values, used in the receiver perormance model or compliant SDSL, are summarized in table 11. Part o them are directly based on SDSL speciications. The remaining values are based on theory. Various parameters are derived rom the above-mentioned parameters. Their purpose is to simpliy the required expression o the used PAM-detection model.

23 23 Model parameter SDSL model 256 kb/s > 256 kb/s SNR-Gap (eective) Γ _db 6.95 db 6.25 db SNR-Gap in parts Γ PAM_dB 9.75 db 9.75 db Γ coding_db 4.4 db 5.1 db Γ impl_db 1.6 db 1.6 db Receiver noise P RN0_dB 140 dbm Data rate d kb/s Line rate b d + 8 kb/s bits per symbol b 3 Summation bounds in PAM model N H N L +1 2 Derived Parameter Required SNR SNR req Γ (2 2b -1) SNR req_db 18 db Symbol rate s b / 3 Table 11. Values or the parameters o the perormance model, obtained rom requirements or SDSL [5]. The echo suppression is captured in the overall implementation loss ( Γ impl ) 6.4 Receiver perormance model or "ADSL over POTS" (EC) This calculation model is capable o predicting a perormance that is benchmarked against the perormance requirements o an compliant ADSL over POTS modem. The reach predicted by this model, under the stress conditions o the associated ADSL speciication [7], is close to the minimum reach required by that speciication. Deviations between the predicted reach and this "benchmarked" reach are less then 100m. The validity o the predicted perormance holds or a wider range o stress conditions Building blocks o the receiver perormance model The receiver perormance model or compliant ADSL over POTS is build-up rom the ollowing building blocks: A irst order (linear) input model or the input block speciied in clause 5.1.1, that combines all imperections (ront-end noise, residual echo and equalization errors), in one virtual noise source. The generic DMT detection model, speciied in clause The parameter values speciied in table 12 o the succeeding clause.

24 Parameters o the receiver perormance model The parameter values, used in the receiver perormance model or compliant ADSL over POTS modems, are summarized in table 12. Parts o them are directly based on ADSL speciications. The remaining values are based on theory. Model parameter DMT model Upstream Downstream Remarks SNR-Gap (eective) Γ db 7.5 db 7.5 db SNR-Gap in parts Γ DMT_dB Γ coding_db Γ impl_db 9.75 db 4.25 db 2.0 db 9.75 db 4.25 db 2.0 db Receiver noise P RN0_dB 120 dbm 135 dbm Symbol rate s 69/ baud 69/ baud See clause sd 4000 baud 4000 baud Data rate d kb/s kb/s Line rate bd bl = d + 16 sd bh = ( d + 8 sd) 1.13 bd = max( bl, bh) bl = d + 16 sd bh = ( d + 8 sd) 1.13 bd = max( bl, bh) b b = 69/68 db b = 69/68 db Bits per symbol b bd / sd bd / sd See clause Available set o tones Center requency location o tone k; k tones tones [7:31] = [k 1 : k 2] k k = k = khz [7:63, 65:255] = [k 1 : k 2, k 3 : k 4] Tone 64 = pilot tone k = k = khz DMT tone k = 64 does not convey any bits because it is reserved as pilot tone. Bit-loading algorithm FBL FBL See (clause 5.2.4) Minimum bit-loading b min 2 2 Bits per sub-carrier Maximum bit-loading b max Bits per sub-carrier Table 12: Values or the perormance parameters extracted rom the perormance requirements under stress conditions. ED NOTE: Once the template PSDs o these ADSL variants are agreed, it is recommended to veriy i the above eective SNR gap is still adequate, or needs a minor modiication 6.5 Receiver perormance model or "ADSL.FDD over POTS" <let or urther study>

25 Receiver perormance model or "ADSL over ISDN" (EC) This calculation model is capable o predicting a perormance that is benchmarked against the perormance requirements o an compliant ADSL over ISDN modem. The reach predicted by this model, under the stress conditions o the associated ADSL speciication [7], is close to the minimum reach required by that speciication. Deviations between the predicted reach and this "benchmark" reach are in most cases less then 80m. The validity o the predicted perormance holds or a wider range o stress conditions Building blocks o the receiver perormance model The receiver perormance model or compliant ADSL over ISDN is build-up rom the ollowing building blocks: A irst order (linear) input model or the input block speciied in clause 5.1.1, that combines all imperections (ront-end noise, residual echo and equalization errors), in one virtual noise source. The generic DMT detection model, speciied in clause The parameter values speciied in table 13 o the succeeding clause.

26 Parameters o the receiver perormance model The parameter values, used in the receiver perormance model or compliant ADSL over ISDN modems, are summarized in table 13. Parts o them are directly based on ADSL speciications. The remaining values are based on theory. Model parameter DMT model Upstream Downstream Remarks SNR-Gap (eective) Γ db 7.8 db 7.5 db SNR-Gap in parts Γ DMT_dB Γ coding_db Γ impl_db 9.75 db 4.25 db 2.3 db 9.75 db 4.25 db 2.0 db Receiver noise P RN0_dB 120 dbm 135 dbm Symbol rate s 69/ baud 69/ baud See clause sd 4000 baud 4000 baud Data rate d kb/s kb/s Line rate bd bl = d + 16 sd bh = ( d + 8 sd) 1.13 bd = max( bl, bh) bl = d + 16 sd bh = ( d + 8 sd) 1.13 bd = max( bl, bh) b b = 69/68 db b = 69/68 db Bits per symbol b bd / sd bd / sd See clause Available set o tones Center requency location o tone k; k tones tones [33:63] = [k 1 : k 2] k k = k = khz [33:95, 97:255] = [k 1 : k 2, k 3 : k 4] Tone 96 = pilot tone k = k = khz DMT tone k = 96 does not convey any bits because it is reserved as pilot tone. Bit-loading algorithm FBL FBL See (clause 5.2.4) Minimum bit-loading b min 2 2 Bits per sub-carrier Maximum bit-loading b max Bits per sub-carrier Table 13: Values or the perormance parameters extracted rom the perormance requirements under stress conditions. ED NOTE: Once the template PSDs o these ADSL variants are agreed, it is recommended to veriy i the above eective SNR gap is still adequate, or needs a minor modiication 6.7 Receiver perormance model or "ADSL.FDD over ISDN <let or urther study> 6.8 Receiver perormance model or "VDSL" <let or urther study>