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

thanks Rich for the comments...you raise the question of future migration and use of the proposal.
 
the Tx and Rx levels vary based on locale (N.A. vs Euro vs Asia vs national standards), by providing MIB variables, this enable common designs to be applicable across national boundaries (but within an operators business area).  In this case it may be desireable to set the loss plans for one operator or even for one user (down to a single line number) without any need to adapt the loss in the future.  
 
In fact, it has been seen that some TE (CPE) devices detect the MTA loop current and based on the loop current they adjust their internal analog gain/loss.  Essentially relating low local loop current/voltage to high analog signal loss.  So if the MTA is configured to provide a minimum loop current (good to minimize power consumption), CPE devices may actually add gain to compensate for the historical analog loop signal loss (bad for MTAs configured with high analog levels (small loss plans) per current PacketCable guidance).  
 
Should it become desireable to support an adaptable loss plan (per connection type or service type within a connection) then this change would fall under the signalling protocol "solution".  It would seem logical that these adaptations would only be in effect for the duration of the connections or might even change within a single connection (start of call in voice mode with one loss, respond to a fax mode with a second loss and at the end of the fax to adapt back to the voice mode loss).  This adaptive loss would only be applicable during a single session since any change in loss would be related to a specific far end (short to long analog POTS loop variability) of that connection.  After the connection is terminated then the loss plan should revert to the SigMIB settings in preparation for the next call which may be within the VoIP network or may again be routed to another analog POTS 
 loop.
 
So there are three rationals for the MIB loss plan flexibility with two potential results...
a "one time" setting based on local operator/user needs (local standards or loop current) and ...
a future potential need for adaptive loss plan adjustments related to a specific far end connection requirement.
 
hope this explains the concept in more detail and the relationship between the MIB values verses a future protocol defined value.
 
Phil

-----Original Message-----
From: Woundy, Richard [mailto:[email protected]] 
Sent: Tuesday, February 15, 2005 6:48 PM
To: Freyman Phillip-FPF300
Cc: [email protected]; [email protected]
Subject: RE: [ipcdn] 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 e
 ach 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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