RE: IETF NCS Sig MIB Gain (loss) plan and tone Levels

>While it is recognized that current standard connection establishment
protocols (NCS, SIP) do not support dynamic gain (loss) plan negotiation or
assignment at this time, it should be recognized that by establishing the
MIB now will enable future protocol updates to improve the end user
experience.
 
Or sometimes, they interfere with future protocol updates. :^(
 
For example, do your proposed read-write MIB object value override the
NCS/SIP negotiated value? Or vice versa?
 
-- Rich, ordinary cable guy, Comcast

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of
Freyman Phillip-FPF300
Sent: Tuesday, February 15, 2005 2:07 PM
To: '[email protected]'; '[email protected]'
Subject: [ipcdn] IETF NCS Sig MIB Gain (loss) plan and tone Levels


Colleagues,

 

This is a proposal to establish the Transmit and Receive gain (loss) plan
parameters in the SigMIB to provide a solution to the setting of supervisory
tone levels at the a-b termination points and it also provides an
intelligent approach to future migration of a dynamic gain (loss) plan based
on the connection requirements.

 

The first point to consider in this proposal is when the MTA passes in band
signaling tones.  Per CableLabs and ETSI these tones are passed to the POTS
a-b (T/R) termination points through signal paths that apply a known loss.
This is usually implemented in the POTS SLIC circuitry either with fixed
loss devices or provisioned by the vendor/operators. 

 

However, when directed by the Call Agent the MTA may generate the
supervisory tones locally.  The same loss plan specifications per CableLabs
and ETSI for in band signaling are assumed to still be active when the tones
are locally generated.  Therefore it is necessary for the internal
supervisory tone generator to compensate for the analog gain (loss) in the
MTA (Typically in the POTS SLIC circuitry) to achieve the desired level at
the a-b (T/R) termination point.  While this gain (loss) may be known to a
vendor during manufacture, the second consideration in this proposal
suggests that this gain (loss) may be required to be changed based on far
end (analog loop) connection characteristics that change depending on the
actual far end connection point.

 

While CableLabs PKT-SP-EMTS-PRIMARY-I01-001128 Clause 8.4.4 and Telcodia
GR-909-CORE R5-17 guildance suggest a 2 dB loss plan default setting, there
is also guildance in GR-909-CORE R4-134 referencing ANSI T1.401-1988 Figure
24 that DTMF levels may be as high as +4 dBm under low loop current
conditions.  Per Telcordia GR-506-CORE Clause 15.1.5, the DTMF receiver
acceptance levels must be greater than -25 dBm and less than 0 dBm.
Considering a + 4dBm DTMF level applied to a 2 dB loss plan would resulting
a DTMF PCM coding level greater than the GR-506-CORE guidance of 0 dBm
maximum for the DTMF detector.  The setting of the default value to -4 dB
gain, ensures proper DTMF signal quality for proper detection and is also
consistent with Telcordia GR-909-CORE which references TR-NWT-000057 for
parameter settings and where 6.1.8 DLC System Loss O-11 suggests a DLC
transmission path loss in each direction o the RT line unit should be 4 dB
+/-2 dB (- 4 dB gain).  

 

Guidance in TIA/EIA TSB122-A and ETSI ES 202 020 further offers the need to
adjust the gain (loss) plan based on if a given MTA is attempting a
connection to one of several analog POTS termination points.  In reviewing
these documents if one considers the MTA as the referenced ONU unit, various
connection cases can be made (ONU to OPS, DGS, WAN, DAL, FXO, FXD, or ATT or
these terminations back to the ONU) where the recommended gain (loss) plan
per connection vary between 0 dB and 9 dB in loss or in some cases 3 dB of
gain.

 

While it is recognized that current standard connection establishment
protocols (NCS, SIP) do not support dynamic gain (loss) plan negotiation or
assignment at this time, it should be recognized that by establishing the
MIB now will enable future protocol updates to improve the end user
experience.

 

Finally, a text enhancement is proposed to clarify the pktcSigDevToneDbLevel
tone level setting measurement with respect to complex tones (tones
sometimes consisting of more than one frequency).

 

Respectfully,

 

Phillip Freyman

Distinguished Member of the Technical Staff

Motorola Connected Home Solutions (formally BCS)


 
============================================================================
==============================================




   pktcNcsEndPntConfigTxGain                  Integer32,  

       pktcNcsEndPntConfigRxGain                  Integer32  

 

   pktcNcsEndPntConfigTxGain    OBJECT-TYPE  

       SYNTAX       Integer32 

       UNITS        "dB"  

       MAX-ACCESS   read-write

       STATUS       current  

       DESCRIPTION  

           "The per line transmitter (A/D) gain.  A positive number reflects
a signal gain, a negative number reflects a signal loss.  This Object may
provision the gain or it may be used to document a non-provisionable gain
between the telco (POTS) a-b (T/R) terminals and the analog codec maximum
PCM coding limit (PCM maximum coding limit).  

 

Based on the default G.711 Vocoder maximum of 3.14 or 3.17 dBm the -4 dB
gain default provides Vocoder coding protection against TE maximum signals
while also providing an initial loss to minimize analog signal echo.  

       DEFVAL { -4 }  

       ::= { pktcNcsEndPntConfigEntry 42 }  

    

 




 

   pktcNcsEndPntConfigRxGain    OBJECT-TYPE  

       SYNTAX       Integer32 

       UNITS        "dB"  

       MAX-ACCESS   read-write  

       STATUS       current  

       DESCRIPTION  

           "The per line receiver (D/A) gain. A positive number reflects a
signal gain, a negative number reflects a signal loss.  This object may
provision the gain or it may be used to document a non-provisionable gain
for use with the pktcSigDevToneDbLevel Object to set the desired level at
the a-b (T/R) terminals.  

 

Based on the default G.711 Vocoder maximum of 3.14 or 3.17 dBm the -4 dB
gain default provides a maximum analog signal level at the a-b (T/R)
termination point. It should be noted that ETSI TS 101 909-4 provides
guidance of 11 dB loss (-11 dB gain) and based on this reference a DEFVAL {
-11 } in international markets may be considered.  

       DEFVAL { -4 }  

       ::= { pktcNcsEndPntConfigEntry 43 }  

    




pktcSigDevToneDbLevel    OBJECT-TYPE 

       SYNTAX       TenthdBm (-250..-30) 

       UNITS        "dBm"  

       MAX-ACCESS   read-write  

       STATUS       current  

       DESCRIPTION  

           "This is the decibel level for each analog signal (tone) that is
locally generated (verses in band supervisory tones) and sourced to the a-b
terminals (TE connection point).  Per the PktcSigDevToneEntry this DbLevel
represents the level required for each tone where each tone may consist of
multiple frequencies which may be summed or amplitude modulated. This Object
must reflect the desired level at the Telco (POTS) a-b (T/R) terminals
including the affect of the pktcNcsEndPntConfigRxGain setting on the
delivered tone.  The wide range of levels for this Object is required to
provide signal generator levels across the wide range of gains but does not
imply the entire range is to be achievable given the range of negative
values of gain (positive loss).     This Object must be set for each tone so
as to generate the combined frequency level at the a-b (T/R) terminals." 

       DEFVAL { -40 }  

       ::={pktcSigDevToneEntry 2 }

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