DOS TSR for V.42bis/MNP5 ?
Date: 23 May 1995 11:34:03 -0800
From: "Baudman"
To: "Eduardo Lalo"
Eduardo,
Although we do not have any plans for a DOS TSR to do V.42bis/MNP5, we
are currently working on an improved driver for Windows.
--Baudman
________________________________________________________
lalo@mail.internet.com.mx (Eduardo) sent the following
comment about The DCD's WWW server:
------------------------------------------------------------
If you are developing a TSR to implement V42 and MNP with any comm
package, my questions are:
Will it be FREEWARE?
Will it be shareware??
Because if you'll be selling this via the modem vendors, for me
for example, will be easier to buy another modem (with the "right" chip
that implements V42 in hardware), because here in Mexico we don't have
much access to stores that sell software... must of them sell hardware
and very popular software (like ms-office and others) they don't sell
comm pack, here because we don't have many BBS, BUT we do have Internet
access (via WINSOCK)...
SO, I need this software, but i (and i think many others) preffer it to be
Shareware or free...
(it will only work with Rockwell modems)
Thanks a lot...
EQM explanation for FAQ
Date: 19 May 1995 09:42:07 -0800
From: "Baudman"
Subject: FW: EQM explanation for FAQ
_______________________________________________________________________________
To: baudman@nb.rockwell.com
From: Palm Stephen on Thu, May 18, 1995 2:53 AM
Subject: EQM explanation for FAQ
_______________________________________________________________________________
From: dan@supra.com (Dan Moore)
Subject: Re: Supra: line quality from at%%q command?
Date: Fri, 5 May 1995 16:21:33 LOCAL
Organization: Supra Corporation
In article burked@eskimo.com (Burke Dykes) writes:
>I'm having a problem interpreting the results of the at%%q command with a
>Supra v.34 (1.2.02):
>Does the value represent some sort of ratio of line noise level to the
>tolerable noise level? Or is it simply some sort of arbitrary number?
>The first possibility might explain the difference between the value when
>in v.32 and v.34
The %Q command reports the instantanious EQM (eye quality
measurement) of the connection. Exactly what this means varies with the
protocol being used by the connection. In non-trellis code modes it is the
square of the error vector and represents the average signal energy in the
error component. Basicly this is the square of the radius of a point in the
signal constellation (eye pattern). In trellis code modes it is the minimum
trellis path length.
EQM is not so much a measurement of noise on the line, but a
measurement of the magnitude of the errors being caused in the signal
constellation. The constellation errors can be caused by many things, noise,
limited bandwidth, etc. Small errors in the signal constellation will not
cause errors in data transfer. Errors in data transfer occur when the signal
constellation errors are large enough that two signalling states begin to
overlap. When this happens either an error correcting protocol (eg. LAPM) can
be relied upon to fix things or a lower data rate with a simplier
constellation can be used. If only an occasional data error occurs then
trusting LAPM is the best choice, this lets data transfer at a higher
average rate. But if lots of data errors are occuring then more time may be
lost in retransmissions by LAPM than is gained by the higher data rate, so
decreasing the data rate will result in higher throughput. At the higher data
rates a limited amount of signalling state overlap is expected even on perfect
lines (in other words don't use V.34 without error correction, you won't like
what happens otherwise).
Since the meaning of EQM varies with protocol you can't really compare
values between different types of connections. So while lower numbers are
always better than higher numbers, an EQM of 10 on a V.32bis connection is not
comparable to an EQM of 10 on a V.34 connection.
VFC and V.34 may have fairly high EQM values (10 to 30) on a good ****
connection. V.32bis typically has EQM values below 15 on a good connection.
--
Dan Moore
Supra Corporation
_______________________________________________________________________________
From palm Mon Apr 3 22:05:39 1995
To: rsamshe@rsa.ericsson.se
In-reply-to: Mattias Heinze's message of Mon, 3 Apr 1995 14:44:26 +0200
Subject: EQM
** > "Mattias" == Mattias Heinze
Hi:
Mattias> I wonder if you can help me with following issue: I have a
Mattias> question about EQM (Eye Quality Measurement). I only know
Mattias> that a low EQM value indicates good line quality and vice
Mattias> versa. Is it a standarized measure or does i vary between
Mattias> different manufacturers?
I believe there is some variance among manufacturers.
Mattias> Does it depend on group delays, attenuation or echoes, or is
Mattias> it a combination of all of them?
It depends on many things.
Also, even if you knew values for all of the items you listed above,
EQM would not be directly proportional... in generally
it would converge to a value over time... but that convergence
would depend on the quality of the algorithms in the modem.
Mattias> Is there any way to make a diagnosis of the line quality
Mattias> considering the EQM value?
yes, but only in vague terms.
Also given a certain EQM value, there is now way to extrapolate
what the particular impairments or their values are.
Mattias> I am also interested in litterature/contact persons related
Mattias> to this topic. Thanks in advance.
Below is some details info from our designer's guide.
regards, kiwin
-------------
Here is some text from the 288 Designer's Guide.
Note that the Functions/Addresses described can NOT be accessed from
the computer interface.
-----------------------
Function 46: Eye Quality Monitor Acc. Method: 4 Addr.: 20C
In V.32 4800 bps, V.29, V.27, V.22 bis, V.22 and Bell 212A modes, EQM
is the filtered squared magnitude of the error vector. However, for
all TCM modes (V.34, V.FC, and V.33 modes, and V.32 12000, 9600, and
7200 bps modes), EQM is the filtered minimum trellis path length (or
metric). This gives a better indication of signal quality for trellis
modes.
The error vector formed by the decision logic can be used to indicate
relative signal quality. As signal quality deteriorates, the average
error vector increases in magnitude. By calculating the magnitude of
the error vector and filter the results, a number inversely
proportional to signal quality is derived. This number is called the
eye quality monitor (EQM). Because of the filter time constant, EQM
should be allowed to stabilize for approximately 700 baud times
following RLSD going active.
The EQM value for the non-trellis configurations is the filtered
squared magnitude of the error vector and represents the average
signal power contained in the error component. The power is directly
proportional to the probability of errors occurring in the received
data and can be used to implement a discrete Data Signal Quality
Detector circuit (circuit 110 of CCITT Recommendation V.24 or circuit
CG of the RS-232-C standard) by comparing the EQM value against
experimentally determined criteria (Bit Error Rate curves). Figure 4-6
illustrates the relationship of the EQM number to an eye pattern
created by a 4-point signal structure (e.g., V.29/4800 bps) in the
presence of high level white noise. The EQM value is proportional to
the square of the radius of the disk around any ideal point. The
radius increases when signal to noise ratio (SNR) decreases. As the
radius approaches the ideal point's boundary values, the bit error
rate (BER) increases. Curves of BER as a function of the SNR are used
to establish a criteria for determining the acceptability of EQM
values. Therefore, from an EQM value, the host processor can determine
an approximate BER value. If the BER is found to be unacceptable, the
host may cause the modem to fallback to a lower speed to improve BER.
It should be noted that the meaning of EQM varies with the type of
line disturbance present on the line and with the various
configurations. A given magnitude of EQM in V.29/9600 does not
represent the same BER as in V.27/4800. The former configuration has
16 points that are more closely spaced than the four signal points in
the latter, resulting in a greater probability of error for a given
level of noise or jitter. Also, the type of line disturbance has a
significant bearing on the EQM value. For example, white noise
produces an evenly distributed smearing of the eye pattern with about
equal magnitude and phase error while phase jitter produces phase
error with little error in magnitude.
Since EQM is dependent upon the signal structure of the modulation
being used and the type of line disturbance, EQM must therefore be
determined empirically in each application. A typical eye pattern
generation circuit is shown in Figure 7-7. Note that the eye pattern
is not displayed when 2800 or 3429 baud is selected in V.34 or V.FC
modes. The use of precoding and shaping in V.34 and V.FC modes will
distort the eye pattern's appearance, even under ideal conditions.
The EQM value should be monitored in V.34 and V.FC modes to determine
the quality of the connection.
Note: Many modem manufacturers only include the UPPER byte in
their EQM report... so 300(hex) would be reported 3
Function 69: EQM Scale Factor (Gain) Acc. Method: 3 Addr.: A29
EQM ARA Bias (Offset) Acc. Method: 2 Addr.: 2A4, 2A5
The automatic rate adaptation (ARA) algorithm adjusts the data rate
based on the level of EQM. The algorithm is twofold, one being used
for initial train and retrain, the other for rate-renegotiation. In
both cases, ARA is enabled by setting the EARC bit (15:0), which
defaults off.
Upon initial train and retrain, the EQM is checked towards the end of
the training, just before the rate negotiation. The 4-point EQM is
compared against a table of values representing the necessary levels
to achieve the corresponding data rates with an EQM of around 2000h.
Once the maximum achievable rate is determined, the CONF register is
changed to reflect the estimate, and is then used to suggest a data
rate in the following negotiations.
In rate-renegotiation, only the instigating modem implements the
algorithm. The responding modem, as usual, indicates availability of
all rates. The instigating modem will attempt to go to a rate which
will result in an EQM of 1800h-3000h. To do that, it will check the
current EQM (at the start of rate-renegotiation), and change CONF
according to the following table:
EQM Before Rate Change Rate Change
Above 3000h Down 1
1800h-3000h No change
C00h-1800h Up 1
600h-C00h Up 2
300h-600h Up 3
Below 300h Up 4
The rates suggested in the rate-renegotiation will then be reflected the
CONF.
Rockwell microcontroller ROM code ...
Date: 19 May 1995 09:41:10 -0800
From: "Baudman"
Subject: FW: Rockwell code
_______________________________________________________________________________
To: drosenzw@its.brooklyn.cuny.edu
From: Palm Stephen on Wed, May 17, 1995 2:49 PM
Subject: Rockwell code
** > "Doni" == Doni
Daniel:
Doni> Thanks for the info... What is dependent on the ROM vs the chipset that
Doni> you provide. In other words... my modem had a problem with v.42 - they
Doni> said that the newer ROM which they have fixes the problem... I would
Doni> think that v.42 is implemented in the Rockwell Chipset? Could you
Doni> explain? Thanks...
All of the control functions (AT parsing, error correction, data
compression, blacklisting, etc) are run on a microcontroller
with the code in an External ROM (FlashROM or EPROM usually).
The ACx chip is one such controller.
The basic modem modulations are run on a DSP (the DPx chips)
but there again... most of it is just code. The DSP code
is in ROM inside the DSP chip since it is a lot cheaper.
A "complete chipset" is an ACx chip with an DPx chip.
The ACx controller does not have to be used... some OEMs pick their
favorite microcontroller (and pair it up with one of our DPx chips)
and writes all of their own control code from scratch.
The ATx chips are similar to the ACx chips, but some things like error
correction and data compression are not done on the microcontroller,
they are done on the host computer CPU. This saves RAM (and ROM) on
the modem board (which are plentiful in the host computer) and the
modem cost becomes lower.
To fix your V.42 problem, the microcontroller ROM code was updated.
Rockwell provides tha basic code to go into the ROM... but vendors can
(and do!) modify, add, or delete code as they see fit for their product.
regards, kiwin
Setting S-registers value
Date: 8 May 1995 09:04:05 -0800
From: "Baudman"
Subject: RE: [rcollins@mc.edu: Modem Init String]
To: "Ron Collins"
>How do you set the value of a setting in Stored Profile 0 and 1 that DOES
>NOT APPEAR in the Active Profile Setting? For Example: My Stored Profile
>0 and Stored Profile 1 settings include a value of S41:192. I need to
>change this to S41:193. When I try ATS41=193, I get an OK from the modem,
>but when I type AT&V, the profiles both still show S41:192. The Active
>Profile, however, does not have an S41 in it. Any help would be greatly
>appreciated.
>Thanks,
>Ron Collins
Ron,
The problem is not whether an S-register appears or doesn't appear in the
current profile of the AT&V display. The problem is that we can't change the
bit mapped S-registers using the ATSxx=yy command.
Bit mapped S-registers should be changed only by changing the associated AT
commands (AT%C, AT%E, AT-Q in the case of S41).
To summarize if you do:
AT%C3%E0-Q0&W1
AT&C1%E0-Q0&W0
you will find that the stored profile 1 has a value of 3 for S41 and stored
profile 0 has a value of 1.
--Baudman