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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