Subject: Re: E.13.1 echo cancellation

From: Roy Spitzer <[email-masked]>
Date: Mon, 14 Feb 2000 09:42:46 -0500

Nancy,

I believe that there is confusion here.  Each endpoint has only one echo
control protocol resident.  That echo control protocol may be turned on or
off.  In addition there is a common feature of automatic echo control
disable which allows the echo control protocol to be turned off by tones
described in the associated standard for that echo control protocol.  This
is automatic echo control disable can be turned on or off, but it is a
separate parameter.

There are other echo control parameters that define the filtering spectrum
used by the echo cancellation protocol.  These parameters are not described
by the H.248 package and tend to be vendor specific.

Regards,
Roy

Roy Spitzer                              Telogy Networks
Phone: 301-515-6531                20250 Century Blvd.
FAX:    301-515-7954                Germantown, MD 20874
email:  [email-masked]

-----Original Message-----
From: Nancy-M Greene [mailto:[email-masked]]
Sent: Sunday, February 13, 2000 9:44 PM
To: [email-masked]
Subject: Re: E.13.1 echo cancellation

I would like ec to have values "on" "off" and "g165". "on" means turn on
echo cancellation and don't turn it off no matter what tones you see, and
"g165" means turn on echo cancellation, but turn it off if you see tones
such as those specified in G.165/G.168.

This is what I have already proposed. I also proposed  the "g164" option. If
no one sees a need for it, then that one can be removed.

Nancy
--------------------------------------------------------------------------
Nancy M. Greene
Internet & Service Provider Networks, Nortel Networks
T:514-271-7221 (internal:ESN853-1077) E:[email-masked]

        ----------
From:   Chip Sharp[SMTP:[email-masked]]
Sent:   Saturday, February 12, 2000 5:49 PM
To:     [email-masked]
Subject:        Re: E.13.1 echo cancellation

        At 02:41 PM 2/9/00 -0600, Nancy-M Greene wrote:

        >Hi Roy,
>G.165/G.168 is one option, and G.164 is a second option (or you choose to
>simply put echo cancellation "on", or you turn it off with "off"), but you
>never have more than one of these options. G.164 is there as an "older
>version" of echo cancellation, for backwards compatible reasons. We could
>change the text explaining ec to be as you say, echo cancellation/echo
>suppression, but I don't know whether it is worth it.

        I don't know why anyone would build a MG with a G.164 echo
suppressor.
G.165 has been out for ages.
My vote is to have ec equal ON or OFF and provide text that states that
this parameter is used to control echo cancellers and older echo
suppressors.  Or better yet, call it echo control.  It looks like you want
a way to turn on echo control and then let it be disabled in-band.  It
would then need a third option of STAYON.

        >Nancy
>-------
>Nancy M. Greene
>Internet & Service Provider Networks, Nortel Networks
>T:514-271-7221 (internal:ESN853-1077) E:[email-masked]
>----------  From:   Roy
>Spitzer[SMTP:[email-masked]]  Sent:   Wednesday, February 09, 2000
>2:11 PM  To:     [email-masked]  Subject:        Re:
>E.13.1 echo cancellation
>
>Nancy,
>
>There seems to be a terminology problem here.  G.165 and G.168 are
>echo  cancellation algorithms.  G.164 is an echo suppressor algorithm.  In
>general  echo cancellators are better than echo suppressors.  Only older
>style  equipment uses echo suppressors and it only works well for half
>duplex  communications.  If ec were defined as echo cancellation/echo
>suppression,  the text is correct.  There does not appear to be an
>application where echo  suppression and echo cancellation would be
>simultaneously active.
>
>Regards,  Roy
>
>Roy Spitzer                              Telogy Networks  Phone:
>301-515-6531                20250 Century
>Blvd.  FAX:    301-515-7954                Germantown, MD
>20874  email:  [email-masked]
>
>-----Original Message-----  From: Nancy-M Greene
>[< mailto:[email-masked] <mailto:[email-masked]> >
mailto:[email-masked] <mailto:[email-masked]> ]
>Sent: Thursday, February 03, 2000 10:53 AM  To:
>[email-masked]  Subject: E.13.1 echo cancellation
>
>
>
>Errata in v14 E.13.1:  Instead of just allowing Echo Cancellation to
>be  "on", or "off", we need to  allow these possibilities:
>
>Permanently enabled: "on"  Permanently disabled: "off"  Enabled but
>conformant to G.165/G.168: "g165"  Enabled but conformant to G.164: "g164"
>
>Default is "g165".
>
>Here is the text to be changed in E.13.1 (in blue, if you see it):
>
>E.13.1  Properties  Echo Cancellation
>
>         PropertyID: ec (0x0008)  By default, the telephony gateways
> always perform echo cancellation  according to  G.165/G.168. However, it
> is necessary, for some calls, to turn off these  operations.  Type:
> enumerated  Possible Values:
>
>         "on" (when the echo cancellation is permanently enabled and
> will  disregard any  incoming tones)  "g165" (when ec is according to
> G.165/G.168: ec is on, but will turn  itself off when it sees a 2100Hz
> tone with phase reversal (i.e. a CED fax  tone, or an  ANS modem
> tone)  "g164" (when ec is according to G.164)  "off" (when it is turned
> off.)  The default is "g165".
>
>         Defined In: LocalControlDescriptor          Characteristics:
> read/write
>
>Nancy
>
>--------------------------------------------------------------------------
 > Nancy M. Greene  Internet & Service Provider Networks, Nortel
>Networks  T:514-271-7221 (internal:ESN853-1077)
E:[email-masked]

        Support NetAid!  http://www.netaid.org <http://www.netaid.org>
--------------------------------------------------
Chip Sharp                 Consulting Engineering
Cisco Systems              Telco Bio-region
Reality - Love it or Leave it.
--------------------------------------------------

---

From: Michael Brown <[email-masked]>
Date: Mon, 14 Feb 2000 12:00:28 -0500

There have been discussions here in Geneva at the SG16 meeting regarding EC and
the following is consistent with those discussions. This reflects the basic EC
behavior. There is also a proposal to create another (future) package which
would allow for very specific control of the parameters for EC which is
envisioned to be used for applications such as offboard EC functions. The SG for
question 9 of SG11 has been engaged to consider and develop this package.

Being a relative neophyte in EC, I am not certain, but I believe that this is
reasonable and appropriate.

Michael Brown