Delaware Radio Technologies LLC et al v. Tesla Motors Inc.

Filing 1

COMPLAINT FOR PATENT INFRINGEMENT filed with Jury Demand against Tesla Motors Inc. - Magistrate Consent Notice to Pltf. ( Filing fee $ 400, receipt number 0311-1411796.) - filed by Wyncomm LLC, Delaware Radio Technologies LLC. (Attachments: # 1 Exhibit A, # 2 Exhibit B, # 3 Civil Cover Sheet)(els)

EXHIBIT A

111111111111111111111111111111111111111111111111111111111111111111111111111
US005506866A

United States Patent

[11]

Bremer et al.
[54]

Date of Patent:

SIDE-CHANNEL COMMUNICATIONS IN
SIMULTANEOUS VOICE AND DATA
TRANSMISSION

[75]

Inventors: Gordon Bremer, Clearwater; Kurt E.
Holmquist, Largo; Kenneth D. Ko,
Clearwater; Keith A. Souders, Tampa,
all of Fla.

[73]

Filed:

0490552
2210237

[51]
[52]
[58]

Int. Cl.

H04J 11100
U.S. Cl •............................................... 375/216; 370/20
Field of Search ..................................... 375/226, 261;
370/20, 110.1, 110.4

6/1992
6/1989

European Pat. Off......... H04L 27/34
United Kingdom .............. H04L 5/12

[57]

ABSTRACT

.••••.......•..••••.•••••••••••••••...••••..•.••••••••

[56]

References Cited
U.S. PATENT DOCUMENTS
4,558,317 12/1985 Armstrong ......................... 340/825.06
4,578,537 3/1986 Faggin et al .......................... 179/2 DP
4,627,077 12/1986 Armstrong ........................... 370/110.4
4,630,287 12/1986 Armstrong ........................... 3701110.4
4,736,377 4/1988 Bradley et al ............................ 371137
4,757,495 7/1988 Decker et al ............................. 370n6
4,899,384 2/1990 Crouse et al ............................. 381/31
5,023,903 6/1991 Bowen ...................................... 379/67
5,036,513 711991 Greenblatt ............................... 370/125

USER 1

20

Bremer et al ........................ 370/100.1
Betts et al ............................ 370/110.4
Greenblatt ............................ 370/110.4
Nakagawa et al ................... 370/110.4
Okouchi .................................... 370/84
Bremer et al ........................... 375/295
Bremer et al. ............................ 370/20

Primary Examiner-Stephen Brinich
Attorney, Agent, or Firm-J. J. Opalach; J. J. Trainor

Nov. 15, 1993
6

311992
411992
811992
9/1992
711993
711995
911995

Apr. 9, 1996

FOREIGN PATENT DOCUMENTS

Appl. No.: 151,686

[22]

5,099,478
5,105,443
5,136,586
5,144,295
5,228,033
5,436,390
5,448,555

Assignee: AT&T Corp., Murray Hill, N.J.

[21]

5,506,866

Patent Number:

[45]

[19J

10

100

SIMULTANEOUS
VOICE AND
~~--r-~ DATA MODEM

SYMBOL BLOCK 405

In a simultaneous voice and data communication system, a
stream of signal points is partitioned into a plurality of
symbol blocks, each symbol block including a data segment
and a control segment. The data segment carries information
from a user, i.e., user data, while the control segment
provides control information. A voice signal is then added to
at least a portion, or all, of the signal points of each symbol
block to provide for simultaneous voice and data transmission to an opposite endpoint. The control information may
represent information from a secondary data source, and/or
may include information about the characteristics of the
succeeding block, e.g., the user data rate, and information
pertaining to characteristics of the communications channel.
50 Claims, 6 Drawing Sheets

200

30

USER 2

SIMULTANEOUS
VOICE AND
41
DATA MODEM f--"---411~~40

SYMBOL BLOCK 410

Is1, s2, s3, ... sss, sssl ss7, ssa, ... ss9, S70 Is1, s2, S3, ... sss, sssl ss7, ssa, ... ss9, s7o I
TIME

d
•

FIG.

~

1

00
•
~

=
=
~

~

USER 1 10

, (11

20_;:t!!:!-"

1

200

100
SIMULTANEOUS 101
VOICE AND
•I DATA MODEM

30

300
301

PSTN

USER 2

SIMULTANEOUS
VOICE AND
41
DATA MODEM .. ~ ~40

I

~

>

"'0
!:1

::e
~

\C
\C

="

Cl:l

;

~

.....
~

s,

FIG. 2
SYMBOL BLOCK 405
./""-......

~---------

DATA SEGMENT 406

="

SYMBOL BLOCK 410
~

CONTROL SEGMENT 407

.../""-.....
-----------~

DATA SEGMENT 411

CONTROL SEGMENT 412

51, 52, 53, ... 555, 556 557, 558, ••• 569, 570 51, 52, 53, ... 555, 556 557, 558, ... 569, 570
TIME

•

til

"'
til

=
="

"'
QC)

="
="

d

•
00.
•
~

=
=

......
~
......

FIG. 3
CONTROL BIT ASSIGNMENTS, 3000S/SEC

"DATA-AND-ANALOG"
ANALOG PARAMETER

STATE
IDENTIFIER

~
:"I
ANALOG PARAMETER

'\

INTEGRITY

~
,.

1--&

~
~

="

f7.l

=-

"DATA-ONLV''

ANALOG PARAMETER

~

~

SECONDARY DATA

STATE
IDENTIFIER

N

sa,

ANALOG PARAMETER

INTEGRITY

="

Ut
-..
Ut

Q
-..

="
="
="

oc

U.S. Patent

Apr. 9, 1996

5,506,866

Sheet 3 of 6

FIG. 4B

FIG. 4A
CONSTELLATION A
TWO BITS PER SYMBOL
4800 bps

CONSTELL.ATION B
THREE BITS PER SYMBOL
7200 bps

•
• •
• •

• • •
• • •
•

FIG. 4C

FIG. 4D

CONSTELL.ATION C
FOUR BITS PER SYMBOL
9600 bps

CONSTELL.ATION D
FIVE BITS PER SYMBOL
12000 bps

• • •
• • • •
• • • •
• • • •
• • • •
• • •

• • • •
• • • •
• • • •
• • • •

FIG. 4E
CONSTELLATION E
SIX BITS PER SYMBOL
14400bps

•

• • •
• • • •
• • • •
• • • • •
• • • •
• • • •
• • • •
• • •
•

• • •
• • • •
• • • •
• • •
• • •
• • •
• • •
• • •

•
• •
•
•

•
• •
••

• •
• •
•

U.S. Patent

5,506,866

Sheet 4 of 6

Apr. 9, 1996

FIG. 5
C START

)

+

610

SET STATE IDENTIFIER FIELD OF CURRENT
SYMBOL BLOCK TO DDATA-ONLY'

615

SELECT "DATA-ONLY' SIGNAL SPACE

'
'

620

I

CHECK IF TELEPHONE 20 HAS
NO
GONE "OFF-HOOK"
JYES
SET STATE IDENTIFIER FIELD OF CURRENT
SYMBOL BLOCK TO "DATA-AND-ANALOG"

630
640_r

'

AFTER TRANSMmiNG CURRENT SYMBOL
BLOCK SELECT .DATA-AND-ANALOG"
SIGNAL SPACE

-,

NO

6so-A

CHECK IF TELEPHONE 20 HAS
GONE •ON-HOOK"

YES

FIG. 6
14400bps
12000bps
I
I

9600bps

I

I
I

I
I
I

7200bps

I
I
I
I

I
I
I
I

b4!

I

CONTROL BITS

U.S. Patent

Apr. 9, 1996

5,506,866

Sheet 5 of 6

FIG. 7

SECONDARY
DATA
SOURCE

60
~-+-"-

......,..._.,--__,

TO
PSTN

200

FIG. 8
101

TO
PSTN

200
I

170

I
I

I

21

I

!

I

TO
VOICE
TELEPHONE~---! DECODER ~---l

20

I
I

I
I
I
I

TO DTE
10

171
~---------__.

SECONDARY-+-----'-..;...;16.;;..8-------!CONTROL 167
DATA
159

I

L___________________ J
I

I

U.S. Patent

Apr. 9, 1996

5,506,866

Sheet 6 of 6

FIG. 9

SECONDARY
DATA
SOURCE
60
t--+-'--

..__,....--,-----'

FIG.

TO
PSTN
200

10
101
TO
PSTN
200

570

TO
TELEPHONE~.- - l

I

20

VOICE
~~~------+---~--~
DECODER
171

I

11

I
I

TO 10 .......,_ _ _ _ _ _ _ _ ___.
DTE
SECONDARY-+----'-.;..;.;..----------'
DATA

CPU

5,506,866

2

1
SIDE-CHANNEL COMMUNICATIONS IN
SIMULTANEOUS VOICE AND DATA
TRANSMISSION
BACKGROUND OF THE INVENTION

5

is then added to at least a portion, or all, of the symbols of
each symbol block to provide for simultaneous voice and
data transmission to the opposite endpoint.
In accordance with a feature of the invention, this control
information may represent any additional information. For
example, this control information may represent information
from a secondary data source, and/or may include information about the characteristics of a succeeding block-like the
user data rate, and information pertaining to characteristics
of the communications channel.
Also, the use of a symbol block makes it possible to send
"raw" asynchronous data from a data terminal without
sending the start and stop bits. This is possible because the
framing provided by the symbol block is used to preserve the
character boundaries so that these boundaries can be properly reconstructed at the receiving end of the data connection. As a result, there is no need to transmit the start and
stop bits-which effectively increases the available data
bandwidth by 25%.

The present invention relates to data communications
equipment and, more particularly, to the use of a sidechannel in a simultaneous voice and data communications
system.
10
The co-pending, commonly assigned, U.S. Patent application of Gordon Bremer and Kenneth D. Ko entitled
"Simultaneous Analog and Digital Communication," Ser.
No. 08/076505, now U.S. Pat. No. 5,448,555, issued Sep. 5,
1995, filed on Jun. 14, 1993, describes a simultaneous voice 15
and data communications system in which a voice signal is
added to a data signal for transmission over a communications channel to a receiving modem.
In this simultaneous analog and digital communication
20
system, the data signal to be transmitted is represented by a
sequence of data symbols, where each data symbol is
BRIEF DESCRIPTION OF THE DRAWING
associated with a particular N-dimensional signal point
FIG. 1 shows a block diagram of a simultaneous voice and
value taken from a signal space. Similarly, the analog signal,
data communications system embodying the principles of
which is represented by a voice signal, is processed so that
25 the invention;
it is mapped into the N-dimensional signal space to provide
a voice signal point. This voice signal point defines the
FIG. 2 shows an illustrative symbol block embodying the
magnitude and angle of a voice signal vector about the origin
principles of the invention;
of the signal space. The data symbol and the voice signal
FIG. 3 is an illustration of the control bit assignments for
vector are then added together to select a resultant N-di30 a control segment of a symbol block for both the "data-only"
mensional signal point, which is then transmitted to a
and "data-and-analog" states;
far-end modem.
FIGS. 4A-4E show a number of illustrative signal spaces
Upon reception of the transmitted N-dimensional signal
with different bit rates;
point, the receiver of the far-end modem detects the embedFIG. 5 is an illustrative flow diagram of a "voice actided data symbol and subtracts the data symbol from the 35
vated" data rate change method;
received N-dimensional signal point to yield the voice signal
FIG. 6 is an illustration of the availability of redundant
vector. This voice signal vector is then used to recreate the
bits for the control segment at data rates higher than 4800
voice signal.
bps;
Using this above-mentioned technique to simultaneously
FIG. 7 shows a block diagram of the transmitter portion
transmit voice and data, there is sometimes a need to 40
of a simultaneous voice and data modem embodying the
transmit additional information separate and apart from the
principles of the invention;
voice and data information. For example, the co-pending,
FIG. 8 shows a block diagram of the receiver portion of
commonly assigned, U.S. patent application of Gordon
a simultaneous voice and data modem embodying the prinBremer, Kenneth D. Ko, Luke J. Smithwick, and Edward S.
Zuranski, entitled "Autorate Method for Simultaneous 45 ciples of the invention;
Transmission of Voice and Data," Ser. No. 08/076,525, filed
FIG. 9 shows a block diagram of another embodiment of
on Jun. 21, 1993, now abandoned, describes that a "silence
the transmitter portion of a simultaneous voice and data
indicator" message can be additionally transmitted on a
modem embodying the principles of the invention; and
secondary, or side-channel, as is known in the art, where this
FIG. 10 shows a block diagram of another embodiment of
side-channel is separate and apart from the simultaneous 50 the receiver portion of a simultaneous voice and data modem
voice and data transmission.
embodying the principles of the invention.
SUMMARY OF THE INVENTION
In accordance with the invention, we have realized an
advantageous side-channel technique wherein the side-channel is multiplexed with the data signal, and the resultant
multiplexed signal is then added to the analog, e.g., voice,
signal to provide simultaneous voice and data transmission.
In an embodiment of the invention, a simultaneous voice
and data modem partitions a stream of symbols into a
plurality of symbol blocks, each symbol block including a
data segment and a control segment. In a "data-mode" of
operation, the data segment carries information from a user
to an opposite endpoint, i.e., user data, while the control
segment provides control information. In a "data-and-analog" mode of operation, an analog signal, e.g., a voice signal,

DETAILED DESCRIPTION
55

60

65

A block diagram of a simultaneous voice and data communications system is shown in FIG. 1. In the description
that follows it is assumed that a communications path has
already been established between user 1 and user 2 of FIG.
1. The communications equipment of user 1 includes data
terminal equipment (DTE) 10, telephone 20, and simultaneous voice and data (SVD) modem 100. The latter receives
two types of signals for transmission to SVD modem 300-a
data signal from DTE 10 and a voice signal from telephone
20. SVD modem 100 encodes both the data signal and the
voice signal to provide a combined voice and data signal for
transmission, via local loop 101, public switched telephone
network (PSTN) 200, and local loop 301, to SVD modem

5,506,866

4

3
300. The basic operation of a simultaneous voice and data
modem, other than the inventive concept, is described in the
above-mentioned Bremer et al. patent application entitled
"Simultaneous Analog and Digital Communication," Ser.
No. 08/076,505, filed on Jun. 14, 1993, now U.S. Pat. No.
5,448,555, issued Sep. 5, 1995, which is hereby incorporated
by reference. SVD modem 300 receives the combined voice
and data signal transmitted by SVD modem 100 and provides the data signal to DTE 30, and the voice signal to
telephone 40. Transmission of data and voice signals in the
opposite direction, i.e., from SVD modem 300 to SVD
modem 100, occur in a like fashion. In the description that
follows only SVD modem 100 is described, however, it is
assumed that SVD modem 300 also incorporates the inventive concept.
As noted earlier, it is sometimes desirable to transmit
additional information between the SVD endpoints of FIG.
1, i.e., SVD modem 100 and SVD modem 300. For example,
there may be periods of time during voice and data communications between SVD modems 100 and 300 when there
is no voice signal present. The presence or absence of a
voice signal may not only be important to any SVD autorating technique but also affects the number of data bits per
symbol as described in the co-pending, commonly assigned,
U.S. patent application of Gordon Bremer, Kenneth D. Ko,
and Luke J. Smithwick, entitled "Shaped Signal Spaces in a
Simultaneous Voice and Data System," Ser. No. 08/076,530,
filed on Jun. 14, 1993. Generally speaking, when transmitting data plus voice the number of symbols in the data signal
space is reduced to increase the quality of the voice transmission. The use of a side-channel provides the ability to
relay information as to the current data signal space to the
far-end SVD modem. This provides the ability to support
"voice activated" data rate changes (described below).
To that end, and in accordance with the inventive concept,
FIG. 2 shows a diagram of a transmission scheme that
includes a side-channel within an SVD signal. This SVD
side-channel not only provides for the transport of additional
information between the SVD endpoints of FIG. 1-but also
allows the voice signal to be transmitted across the full
bandwidth of the SVD data connection.
As can be observed from FIG. 2, information from an
SVD modem is provided in a frame, or "symbol block," e.g.,
symbol block 405. For the purposes of this example, a
symbol block comprises 70 symbols. Consecutive symbols
within each symbol block are identified as S1, S2, S3, .
.. , S70.
Each symbol block is further divided into a data segment,
e.g., data segment 406; and a control segment, e.g., control
segment 407. Let the group of symbols in the data segment
be, for example, S1 to S56. These are the "data symbols" and
always convey DTE data. For the purposes of the following
discussion the symbol rate is illustratively 3000 symbols/
second (s/sec.), although other symbol rates may be used,
e.g., 2800 s/sec. At a symbol rate of 3000 s/sec., the average
data symbol rate of a symbol block is equal to (56170)x
3000)=2400 s/sec. Consequently, if there are 6 bits of data
per data symbol, the resultant data rate is 14400 bits/sec
(bps). It is assumed that this data rate is high enough to meet
a user's needs so that the remaining bandwidth of the SVD
data connection can be allocated to the control segment,
which provides the side-channel.
The remaining symbols of the control segment, i.e., S57
to S70, are the "control symbols." Usually, the latter never
convey DTE data, but convey control information. Each
control symbol represents a number of "control bits." The

5

10

15

20

25

30

35

40

45

50

55

60

65

control symbols are encoded and scrambled the same as the
DTE data symbols, e.g., they use the same signal space. The
control symbols provide the side-channel for conveying
additional information between SVD modem 100 and SVD
modem 300. In accordance with the inventive concept,
although the data symbols represent user data and the
control symbols represent control information, both the data
and control symbols may also convey analog data, which in
this example is the voice signal that is provided to SVD
modem 100 by telephone 20 (described below). As a result,
the side-channel is a part of the simultaneous voice and data
transmission.
It should be noted that if a lower symbol rate is used, e.g.,
2800 s/sec., the size of the data segment and control segment
changes. For example, if it is assumed that both the size of
each symbol block is fixed at 70 symbols and that the
average symbol rate of 2400 s/sec. should be maintained,
then a symbol block at 2800 s/sec. has a data segment of 60
symbols and a control segment of 10 symbols.
Although the symbols of the control segment can represent any type of information, in this illustrative example the
control information is further divided as shown in FIG. 3 to
represent analog parameter information, a state identifier,
secondary data, and an integrity field. The number of bits
available to represent the analog parameter information is a
function of both the "state" of the symbol block and the
number of bits per control symbol (described below).
The "state" of a symbol block is represented by the value
of the "state identifier field" of the previous symbol block.
For example, the state of symbol block 410 of FIG. 2 is
defined by the value of the state identifier field of symbol
block 405, which preceded symbol block 410. The state of
any symbol block in this example is limited to two: "dataonly" or "data-and-analog." Consequently, the state identifier field is conveniently represented by one bit, illustratively
control bit number 14 shown in FIG. 3. A value of "one"
represents the "data-and-analog" state, while a value of
"zero" represents the "data-only" state.
SVD modem 100 defaults to the "data-only" state, e.g.,
upon power-up, and the state identifier bit is initially set to
represent the "data-only" state in any subsequent data connection established with SVD modem 300. FIGS. 4A-4E
show a number of illustrative signal spaces for transmitting
information between the SVD modem endpoints. Although
the data symbols represent user data and the control symbols
represent control information, both the data and control
symbols are selected from the same signal space. In the
"data-only" state any of these 6 signal spaces can be used to
transmit information between the SVD endpoints. Constellation "A" of FIGS. 4A-4E show a signal space where each
symbol represents two bits of information. Similarly, constellation "E" illustrates a signal space where each symbol
represents 6 bits of information. Preferably, constellation E
of FIGS. 4A-4E will be used since, conditions permitting, it
allows the highest transmission bit rate between the SVD
endpoints.
There is voice transmission between SVD endpoints only
in the "data-and-analog" state. As noted above, when simultaneously transmitting both voice and data, there is a tradeoff
between the quality of the voice transmission and the size of
the symbol constellation. For example, if constellation E of
FIGS. 4A-4E is used in the "data-and-analog" state, the
higher symbol density reduces the dynamic range of any
voice signal that is superimposed on any of the symbols
taken from this constellation- with the result that voice
quality is impaired. Therefore, it is desirable to select

5,506,866
5
constellation A during voice transmission because the fewer
symbols of constellation A allow a larger dynamic range for
the voice signal-and therefore improves the quality of the
voice signal transmission.
An illustrative method for use in SVD modem 100 for 5
switching between the signal spaces of FIG. 3 is shown in
FIG. 5. At power-up, or the beginning of each data connection, SVD modem 100 enters the "data-only" state in step
610. In step 615, SVD modem 100 selects that signal space
associated with the "data-only" state, i.e., the highest data 10
rate negotiated between SVD modem 100 and SVD modem
300. SVD modem 100 monitors telephone 20 in step 620 to
check if telephone 20 has gone "off-hook." As long as user
1 does not go off-hook, SVD modem 100 remains in the
"data-only" state by returning to step 610. However, when
15
SVD modem 100 detects that user 1 has taken telephone 20
off-hook, SVD modem 100 assumes that voice communications is desired and switches to the "data-and-analog"
state. In step 630, SVD modem 100 alters the state identifier
bit in the current symbol block, e.g., block 405 of FIG. 2, to
indicate to SVD modem 300 that the next symbol block, e.g., 20
block 410, will be in the "data-and-analog" state. Upon
completion of transmitting symbol block 405, SVD modem
100 then switches to constellation A of FIGS. 4A-4E in step
640 for the transmission of symbol block 410. Thus, when
user 1 goes off-hook at telephone 20, SVD modem 100 25
dynamically changes the bit rate to accommodate the presence of a voice signal. Consequently, upon reception of
block 405, SVD modem 300 not only knows which signal
space to use to decode the incoming symbol stream from
block 410, but also can infer the state of the switch hook at 30
telephone 20.
After switching to the "data-and-analog" state, SVD
modem 100 monitors telephone 20 to detect that user 1 has
gone "on-hook" in step 650. When user 1 goes "on-hook," 35
SVD modem 100 returns to step 610 to set the state identifier
field for the next symbol block to the "data-only" state and
thereafter switches data rates back to the last data rate
negotiated between SVD modem 100 and SVD modem 300.
Returning to FIG. 3, the number of control bits in the 40
control segment is shown as fixed at 28 bits. However,
generally speaking, assuming a constant symbol rate, the
number of control bits available for the control segment
varies with the number of bits per control symbol. For
example, in the "data-only" state any of the constellations of 4 s
FIG. 4 may be used. If constellation E is used, there are 6 bits
per symbol. Therefore, there are 84 bits available in any
control segment for transporting control information
between SVD modem 100 and SVD modem 300. However,
in the "data-and-analog" state, SVD modem 100 switches to 50
constellation A, which results in only 2 bits per symbol, or
28 bits in the control segment for the 14 control symbols S57
to S70. Consequently, while the number of bits in a control
segment could indeed vary as a function of the selected
signal space, in this embodiment, the number of bits in the 55
control segment is bounded by the number of control bits
available in the "data-and-analog" state, i.e., 28 bits.
In the "data-and-analog" state, control bits N1 to N13,
N15 to N22, and N28, are used to represent "analog parameter" information. Similar to the state indicator field, these 60
analog parameters convey information pertaining to the next
symbol block like "adaptive gain" information in bit locations 15-22, and 28. In this example, the analog parameter
bit locations 1-13 in the "data-and-analog" mode are
reserved for future use. It should be noted that information 65
conveyed by the control segment does not have to be
restricted to information about the "next" symbol block.

6
In a "data-only" symbol block, the transmission of "analog parameters" is optional. In fact, the number of control
bits available for the transport of analog parameter information is reduced so that in the "data-only" state secondary
data is transmitted by control bits N6 to N13. Any transmission of secondary data does not use all of the control bit
assignments even though there is no "analog parameter"
information transmitted in a "data-only" state. Using these
control bit assignments, the secondary data rates at 3000
s/sec. is 342 bits per sec.
As noted above, in the "data-only" state higher density
signal spaces may be used with the result that there are more
bits available for transport of control information than are
actually used in the above-defined control segment. However, there is nevertheless a way to use these additional data
bits in the SVD communications system of FIG.. 1 to
minimize errors in detecting the correct state of a received
SVD symbol block.
If an SVD receiver makes an error in detecting the correct
state of the received symbol block, this error has different
effects on a user depending on the correct state. For example,
if the state of a received symbol block is "data-only" but the
receiver interprets the state as "data-and-analog," then the
receiver will decode data with perhaps the wrong decision
regions and will enable the analog output-causing a "data
blast" to the listener. Conversely, if the state is "data-andanalog" but the receiver interprets the state as "data-only"
then the receiver will inadvertently silence the analog output. Of these two possible error conditions, it is likely that
an erroneous decision that the symbol block is in the
"data-only" state is more acceptable to a user since the user
will only hear silence. However, a mistaken decision that the
symbol block is in the "data-and-analog" state may be more
annoying to a user because of the likelihood a user will hear
a data blast. Therefore, it would be better if the possibility
of this latter type of error were minimized. Especially since
the possibility of this type of error increases as the data rate
increases.
To lessen the possibility of an erroneous detection of the
"data-and-analog" state while in the "data-only" state, some
of the additional bits heretofore unused in each control
symbol, at data rates higher than 4800 bps, are now utilized
as "redundant" state identifier bits. In particular, one additional bit per control symbol is used at data rates greater than
4800 bps. This provides an additional fourteen bits of
information, albeit redundant, to an SVD receiver. FIG. 6
shows a simple illustration of this technique. While in the
"data-only" state, data transmission can occur at data rates
from 4800 bps to 14400 bps as provided by the signal spaces
shown in FIGS. 4A-4E. Each control symbol therefore
represents a number of bits that is a function of the currently
selected signal space. This number of bits varies from b0 to
b5 as shown in FIG. 6. The data rate of 4800 bps provides
the minimum number of bits per symbol-b 0 and b 1 • As the
data rate increases, additional bits become available, e.g.,
one bit, b 2 , at a data rate of 7200 bps, and upto four bits, b 2
to b5 , at a data rate of 1400 bps. In this illustrative embodiment, only one additional bit, e.g., b 2 , is used; any additional
bit capacity at the higher data rates is simply ignored.
These fourteen bits are simply copies of the state identifier
bit transmitted in the control segment of the current symbol
block. The SVD receiver performs a "majority" vote of the
fourteen redundant bits and the state identifier bit from the
control segment to determine the appropriate state for the
next symbol block.
Although at data rates higher than 4800 bps an additional
redundant bit is used from the control symbols to protect

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against an erroneous decision by an SVD receiver as to the
of telephone 20, and analog gain information for transmisstate of the next symbol block, at the lower data rate of 4800
sion to far-end SVD modem 300. As discussed above, the
bps it is assumed that the integrity field of the control
"off-hook" signal alerts CPU 105 when user 1 at telephone
20 goes off-hook or on-hook so that SVD modem 100 can
segment, combined with the spatial separation provided in
the 4800 bps constellation, provides adequate protection of 5 select between the "data-only" state or the "data-and-analog" state as described above. CPU 105 controls the selecthe state identifier bit.
tion of the appropriate signal space in scrambler and encoder
From FIG. 3, it can be seen that five control bits define the
180 via the signal on line 124.
integrity field. In this example, the integrity field represents
DTE 10 provides a data signal to data buffer 125, which
the inverse of five other predefined control bits. These
integrity bits are used to bolster the decoding of the control 10 stores the data provided by DTE 10 for latter delivery to
multiplexer (MUX) 140. Control buffer 120 receives two
segment by an SVD receiver. The five control bits 14
through 18 are protected by the integrity field. These are the
signals on lines 107 and 118. The signal on line 118
state identifier bit, the equalizer lock bit for the upcoming
represents any secondary data source. In fact, secondary data
symbol block, and 3 bits that represent the most significant
source 60 represents the ability of SVD modem 100 to
bits of adaptive gain. The SVD receiver uses biased voting 15 provide additional bandwidth for data communications
to evaluate the integrity bits. For example, if received
albeit within the control segment during the "data-only"
mode of operation. Although shown for simplicity as an
adaptive gain bit is inconsistent with its respective integrity
bit, the receiver uses the gain value that results in a lower
independent source, secondary data source 60 can be DTE
volume to the audio speaker, on the premise that a brief
10. For example, control buffer 120 could be coupled to data
reduction in volume is more acceptable to the listener than 20 buffer 125 to allocate this additional data bandwidth to DTE
an unexpected increase in volume.
10. In comparison, the signal on line 107 represents the
analog parameter information as defined in FIG. 3. It can be
As shown in FIG. 3, the integrity field is located within
observed that while this embodiment sends a variety of
the control segment, as opposed to being located at either
different types of control information, there is no requireboundary of the control segment, to increase the probability
that a shift in timing will cause errors in the integrity field. 25 ment that any information peculiar to the SVD communications system be transmitted in the control segment.
An SVD receiver also keeps track of integrity errors over
The state of SVD modem 100 is provided from CPU 105
multiple symbol blocks as an indicator of gross channel
to control buffer 120 via line 119. This represents the value
conditions or loss of symbol counter synchronization
(described below). Either of these conditions causes the
used by control buffer 120 for the state indicator bit of the
SVD receiver to perform a retraining with the opposite SVD 30 control segment. If SVD modem 100 is in the "data-only"
endpoint.
state, then control buffer 120 multiplexes any analog parameter information, if any, along with the secondary data to
As described above, it is advantageous to protect against
provide the control segment as shown in FIG. 3 for the
the possible occurrence of an erroneous switch from one
"data-only" state. On the other hand, if SVD modem 100 is
state to the other. In the analog parameter field there is gain
35
in the "data-and-analog" state, then control encoder 120
information for the voice signal in the "data-and-analog"
provides the "data-and-analog" control segment, which only
state. However, it is not necessary to provide any gain
includes analog parameter information as provided by CPU
information in the "data-only" state since there is no voice
105 via line 107. Control encoder 120 also generates the
signal. Therefore, additional protection can be provided
against an erroneous switch from the "data-only" state to the 40 integrity field and, for signal spaces which accommodate it,
duplicates the state identifier bit to provide the above"data-and-analog" state by providing dummy gain informadescribed redundancy when the data rate is greater than
tion such that if an SVD receiver erroneously switches to the
4800 bps.
"data-and-analog" state the resulting amplification of the
Transmit counter 110 controls MUX 140, which provides
data signal, which appears as noise to a user, is low.
Reference should now be made to FIG. 7, which shows a 45 either data or control information to scrambler and encoder
180. The latter includes any of the well-known encoding
block diagram of transmitter 102 of SVD modem 100 that
techniques like scrambling, trellis-coding, etc., to provide
embodies the principles of this invention. Other than the
the sequence of symbols on line 181 at a symbol rate, Iff.
inventive concept, the individual components of SVD
The symbols are selected from one of the signal spaces
modem 100 are well-known and are not described in detail.
For example, CPU 105 is a microprocessor-based central 50 shown in FIGS. 4A-4E. The selection of the signal space is
controlled by CPU 105 via line 124.
processing unit and associated memory for storing program
data. Also, it is assumed that the operating data symbol rate
CPU 105 synchronizes transmit counter 110 in response
and the number of data bits per symbol in the "data-only"
to a training, or retraining, event between SVD modems 100
state are determined during the initial training and rate
and 300. As is known in the art, both modems of a data
negotiation sequences, and by any retraining sequences that 55 connection typically perform a hand-shaking procedure that
occur between SVD modems 100 and 300. Although it is
includes a training sequence to initialize the equalizers and
assumed that the symbol rate does not change during a
echo cancelers of each modem (not shown). The need to
communications session, the number of data bits per symbol
perform a retraining sequence is detected by the loss of
may also change in accordance with any of the well-known
synchronization. Loss of synchronization is detected be
autorating techniques.
60 CPU 110 when the receiver of SVD modem 100 (discussed
below) indicates that too many integrity field errors have
Telephone 20 provides a voice signal to voice encoder
occurred over a number of received symbol blocks.
130. The latter provides a sequence of two-dimensional
signal points, at a predefined symbol rate of Iff symbols per
Transmit counter 110 must be synchronized because
sec., on line 131. Each two-dimensional signal point repretransmit counter 110 frames the symbol blocks by counting
sents a "voice signal vector" about the origin of a signal 65 symbol periods. As described above, and shown in FIG. 2,
space (not shown). In addition, line 104 conveys signaling to
each symbol block includes 70 symbols. Therefore, transmit
provide CPU 105 with information on the "off-hook" status
counter 110 counts "modulo 70." During the first 56 symbol

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10

periods, i.e., the data segment, transmit counter 110 controls
modem is detected by demodulator 150, which notifies CPU
MUX 140 to provide the data segment information to
105 via line 152.
scrambler and encoder 180. During the last 14 symbol
Voice decoder 170 provides the voice signal during the
periods, i.e., the control segment, transmit counter 110
"data-and-analog" state to telephone 20. Voice decoder 170
controls MUX 140 to provide the control segment informa- 5 is enabled during the "data-and-analog" state by CPU 105
tion to scrambler and encoder 180.
via line 171. Receive counter 176 provides a synchronizaAdder 135 adds each voice signal vector on line 131, if
tion signal to voice decoder 170 so that the correct received
symbol is subtracted from the received signal point sequence
any, to a respective one of the symbols provided by scrambler and encoder 180 to provide a stream of signal points to
conveyed by line 151. The received symbol sequence is
modulator 145. The latter functions in accordance with the 10 provided by line 191 of decoder 190. Voice decoder 170
well-known quadrature amplitude modulation (QAM) to
includes buffering to accommodate any delays introduced by
provide a transmit signal to hybrid 146 for transmission to
decoder 190 in decoding the received signal points.
SVD modem 300 via PSTN 200.
The above-described inventive concept thus creates an
Receiver 103 of SVD modem 100 performs complemenSVD side-channel, where both the data and control symbols
tary functions to transmitter 102 described above and is 15 are available to carry the voice signal. Another embodiment
shown in block diagram form in FIG. 8. Common elements
of the inventive concept in shown in FIGS. 9 and 10. FIG.
in receiver 103 and transmitter 102 have the same reference
9 is a block diagram of the transmitter portion of an SVD
numeral, e.g., CPU 105, hybrid 115, etc. Hybrid 115 receives
modem and is similar to FIG. 7 except that the respective
a transmitted signal from SVD modem 300, via PSTN 200,
signal spaces used for the data and control segments are
and applies this received signal to demodulator 150. The 20 different.
latter provides a received signal point sequence to decoder
DTE 10 provides a data signal to data encoder 525, which
190, which performs the inverse function of scrambler and
provides a sequence of two-dimensional signal points at the
encoder 180 of transmitter 102 to provide an informationsymbol rate, lff. These two-dimensional signal points are
bearing signal each symbol period to demultiplexer
selected from one of the signal spaces shown in FIGS.
(DEMUX) 155. Receive counter 175 controls DEMUX 155 25 4A-4E, which is controlled by CPU 105 via line 524. Each
via line 177. After a training, or retraining, event, as
signal point is associated with a particular two-dimensional
described above, CPU 105 resets receive counter 175 to
data symbol. Data encoder 525 includes any of the wellbegin counting modulo 70. Receive counter 175 controls
known encoding techniques like scrambling, trellis-coding,
DEMUX 155 to apply the first 56 symbol periods of
etc., to provide the sequence of data symbols.
information to DTE 10 via line 11. This is the data segment. 30
Control encoder 520 receives two signals, as described
Then receive counter 175 controls DEMUX 155 to apply the
above, on lines 107 and 119 and provides a sequence of
last 14 symbol periods of information to control element
control symbols on line 521 at the symbol rate, 1T. Control
165. Receive counter 175 repetitively continues this demulencoder 520 functions in a similar fashion to data encoder
tiplexing of the received information stream until reset by
525 and includes any of the well-known encoding techCPU 105.
35
niques like scrambling, trellis-coding, etc., to provide the
As noted above, each SVD modem initially begins in the
sequence of control symbols. Similar to data encoder 525
"data-only" state. Consequently, receiver 103 assumes that
above, these two-dimensional symbols are selected from one
the first symbol block received is in the "data-only" state.
of the signal spaces shown in FIG. 4. These control symbols
The state indicator field of this first symbol block then 40 represent a control segment. The state of SVD modem 100
determines the state of the succeeding symbol block, etc.
is provided from CPU 105 via line 119. If SVD modem 100
is in the "data-only" state, then control encoder 520 multiControl element 165 provides CPU 105 with the value of
the state indicator bit on line 167; any analog parameter
plexes any analog parameter information, if any, along with
information on line 169; and an indicator if there was an
the secondary data to provide the control segment as shown
error in the integrity field on line 159. Control decoder 165 45 in FIG. 3 for the "data-only" state. On the other hand, if SVD
performs the majority vote for any duplicate state indicator
modem 100 is in the "data-and-analog" state, then control
encoder 520 provides the "data-and-analog" control segbits (as described above) when the data rate is greater than
ment, which only includes analog parameter information as
4800 bps. Additionally, control decoder 165 processes the
integrity field bits (as described above). Finally, control
provided by CPU 105 via line 107. Control encoder 520 also
decoder 165 provides any secondary data, via line 168.
50 generates the integrity field and, in the "data-only" state,
duplicates the state identifier bit to provide the aboveIn response to the information provided by control
described redundancy when the data rate is greater than
decoder 165, CPU 105 performs a number of actions. First,
4800 bps.
based on the value of the state indicator information, CPU
Transmit counter 110, which counts modulo 70, controls
105 controls the signal space used by decoder 190 to decode
the next symbol block via line 109. This allows receiver 103 55 multiplexer (MUX) 540, which provides the above mento correctly demultiplex and decode the received signal
tioned symbol blocks on line 541. CPU 105 synchronizes
point sequence. Next, CPU 105 adjusts any analog settings
transmit counter 110 in response to a training, or retraining,
event between SVD modems 100 and 300. During the first
based upon the analog parameter information, via line 172.
56 symbol periods, i.e., the data segment, transmit counter
In this embodiment, the analog parameter information is
only used by voice decoder 170. This allows receiver 103 to 60 110 controls MUX 540 to provide the data symbols from
data encoder 525 to adder 135. During the last 14 symbol
easily adapt gain settings for the voice signal and other
periods, i.e., the control segment, transmit counter 110
analog parameters (if any). Finally, CPU 105 generates a
controls MUX 540 to provide the control symbols from
retrain based upon the cumulative statistics of the number of
control encoder 520 to adder 135. Since transmit counter 110
errors in the integrity field over a period of time. When a
retrain event occurs, CPU 105 resets receive counter 175. It 65 switches MUX 540 between data encoder 525 and control
encoder 520, each of these encoders must include buffers to
should be noted that CPU 105 also resets the receive counter
provide storage for any data accumulated during that period
if a training, or retraining, sequence from the far-end SVD

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12

of time when the other encoder is providing symbols to
MUX 540.
Adder 135 adds each voice signal vector on line 131, if
any, to a respective one of the symbols provided by MUX
540 to provide a stream of signal points to modulator 145.
The latter functions in accordance with the well-known
quadrature amplitude modulation (QAM) to provide a transmit signal to hybrid 146 for transmission to SVD modem
300 via PSTN 200.
Receiver 503, shown in FIG. 10, performs complementary functions to transmitter 502 of FIG. 9. Hybrid 115
receives a transmitted signal from SVD modem 300, via
PSTN 200, and applies this received signal to demodulator
150. The latter provides a received signal point sequence to
demultiplexer (DEMUX) 555, which is controlled by
receive counter 175 via line 177. After a training, or retraining, event, as described above, CPU 105 resets receive
counter 175 to begin counting modulo 70. Receive counter
175 controls DEMUX 555 to apply the first 56 received
signal points to data decoder 560. Then receive counter 175
controls DEMUX 555 to apply the last 14 received signal
points of the received symbol block to control decoder 565.
Receive counter 175 repetitively continues this demultiplexing of the received signal point stream until reset by
CPU 105.
Control decoder 565 provides CPU 105 with the value of
the state indicator bit on line 167; any analog parameter
information on line 169; and an indicator if there was an
error in the integrity field on line 159. Control decoder 565
performs the majority vote for any duplicate state indicator
bits (as described above) when the data rate is greater than
4800 bps. Additionally, control decoder 565 processes the
integrity field bits (as described above). Finally, control
decoder 565 provides any secondary data, via line 168.
In response to the information provided by control
decoder 565, CPU 105 performs a number of actions. First,
based on the value of the state indicator information, CPU
105 controls the signal space used by data decoder 560 and
control decoder 565 to decode the next symbol block via line
109. This allows receiver 503 to correctly demultiplex and
decode the received signal point sequence. Next, CPU 105
adjusts any analog settings based upon the analog parameter
information, via line 172. Finally, CPU 105 resets receive
counter 175 in response to a training, or retraining, event as
described earlier.
Both data decoder 560 and control decoder 565 perform
the inverse of the coding functions of data encoder 525 and
control encoder 520, respectively. Voice decoder 570 provides the voice signal during the "data-and-analog" state to
telephone 20. Voice decoder 570 is enabled during the
"data-and-analog" state by CPU 105 via line 171. Receive
counter 176 provides a synchronization signal to voice
decoder 570 so that the correct received symbol is subtracted
from the received signal point sequence conveyed by line
151. Voice decoder 570 includes buffering to accommodate
any delays introduced by data decoder 160 and control
decoder 165 in decoding the received symbols.
An SVD symbol block conveys either synchronous data,
or asynchronous data, streams. However, the use of an SVD
symbol block makes it possible to send "raw" asynchronous
data (defined below) without sending the start and stop bits
of this data. The start and stop bits are removed after a
character is received from the DTE and restored at the other
end of the circuit before sending the character to the DTE.
The framing provided by the SVD block coding is used to
preserve the character boundaries so that they can be prop-

erly reconstructed at the receiving end of the link. The ability
to send asynchronous formatted data without the start and
stop bits provides a significant improvement in the overall
responsiveness of the system and effectively increases the
available data bandwidth by 25%.
The term "raw" asynchronous data means that the modem
is configured so that the modem's own error control and data
compression capabilities are not used. In this mode, commonly referred to as "buffered mode," characters received
from the DTE are sent bit for bit to the other modem.
Because flow control mechanisms are still available, the data
rate between the DTE and the modem can be different from
the rate used over the PSTN line, however the data content
of the two data streams are identical.
In this embodiment, this raw data mode is enabled by
CPU 105 in response to DTE 10 providing a "buffered
mode" command. As in known in the art, data terminal
equipment, like DTE 10, can configure or control various
options in a modem, like SVD modem 100, by putting the
modem in a "command mode." During the command mode
of operation, the modem interprets data from the data
terminal equipment as instructions for the modem. A user of
a modem may enter the command mode in a number of
ways, e.g., by applying power to the modem, or by sending
to the modem a predefined sequence of characters, like
"+++"as defined in the "AT command set." For the purposes
of this discussion, SVD modem 100 provides a command
mode that is similar to the "AT command set."
Referring back to FIG. 7, after receiving the buffered
modem command, CPU 105 of SVD modem 100 provides
not only the current state identifier to data buffer 125, but
also uses line 123 to provide a signal to data buffer 125 to
strip the start and stop bits from any data provided by DTE
10. One bit from the analog parameter field is then used to
identify this raw data mode to specify that the next data
segment includes raw data. As a result, receiving SVD
modem 300, upon detecting this information in the analog
parameter field, then controls DEMUX 155 to reconstruct
the data bytes by adding the start and stop bits before
sending the data to DTE 10.
This data transfer configuration may be performed for use
by "telegraphics" programs which are PC applications that
are designed for efficient transfer of graphical information
over PSTN circuits. These programs must communicate
with the modem using asynchronous data formats because
personal computers are not equipped with the interfacing
hardware needed for more bandwidth-efficient synchronous
g-ansmission.
For an SVD symbol block in which the number of data
symbols is an integral number of eight, no additional framing information is needed since, regardless of the number of
data bits per symbol, each block contains an integral number
of octets derived from asynchronous characters by stripping
the start and stop bits. However, for an SVD symbol block
in which the number of symbols is not an integral multiple
of eight, a "super-frame" structure is required. This requires
reserving at least one bit of the available "analog parameter
bits" (or some unique pattern of these bits) to periodically
mark the beginning of the super-frame.
The foregoing merely illustrates the principles of the
invention and it will thus be appreciated that those skilled in
the art will be able to devise numerous alternative arrangements which, although not explicitly described herein,
embody the principles of the invention and are within its
spirit and scope.
For example, although the invention is illustrated herein
as being implemented with discrete functional building

5

10

15

20

25

30

35

40

45

50

55

60

65

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blocks, e.g., encoders, decoders, transmitter, etc., the functions of any one or more of those building blocks can be
carried out using one or more appropriate programmed
processors, e.g., a digital signal processor.
In addition, the analog signal is not limited to a voice 5
signal, any analog signal can be used, e.g., even another
data-bearing signal. The order of the control and data
segments does not matter, and the inventive concept is
applicable to any N-dimensional signal space. Other techniques can be used to select the appropriate signal space as 10
a function of the state of an SVD modem, e.g., detecting the
presence of voice energy from the telephone. Also, the
integrity field is not limited to an inverse bit technique, other
error detection schemes, like parity, can be performed on a
portion, or all, of the control segment. Finally, while FIG. 1
15
illustratively coupled simultaneous voice and data modem
100 to DTE 10 and telephone 20 via local loop 101, the
inventive concept is also applicable to other communications environments like cellular.
We claim:
1. A method for transmitting a side-channel in a simulta- 20
neous analog and digital communications system, the
method comprising the steps of:
multiplexing a plurality of symbol streams to provide a
sequence of symbol blocks, where each symbol block
includes a predefined number of symbols from each 25
symbol stream; and
transmitting each symbol block;
wherein the step of transmitting further includes the step
of adding to each symbol of each symbol block a signal 30
point before transmission.
2. The method of claim 1 further including the step of
encoding an analog signal to provide the signal point.
3. The method of claim 2 wherein the analog signal is a
voice signal.
35
4. The method of claim 1 wherein the plurality of symbol
streams is a data symbol stream and a control symbol stream
and each symbol block includes a data segment and a control
segment, wherein the data symbols of each symbol block are
contiguously located within the data segment and the control 40
symbols of each symbol block are contiguously located
within the control segment.
5. The method of claim 4 wherein the control segment
represents a fixed number of bits, Y, which is equal to the
number of control symbols within a symbol block multiplied 45
by a y number of bits from each of these control symbols.
6. The method of claim 5 wherein each control symbol
represents x bits, and x:>y.
7. The method of claim 6 wherein duplicate control
information is conveyed by x-y bits of each control symbol. 50
8. The method of claim 4 wherein the data symbols
represent a synchronous data stream.
9. The method of claim 4 wherein the data symbols
represent an asynchronous data stream without the start and
stop bits.
55
10. The method of claim 4 wherein at least a portion of the
control information conveyed by a current control segment
is a function of the information conveyed by a succeeding
symbol block.
11. A method for transmitting side information in a 60
simultaneous analog and data communications system, the
method comprising the steps of:
encoding a data signal to provide a number of data
symbols, J, over a period of time equal to T 1 ;
encoding at least one control signal to provide a number 65
of control symbols, K, over a period of time equal to T 2 ,
where the control signal represents control information;

14
multiplexing the number of data symbols and the number
of control symbols to provide a symbol block comprising the J+K symbols;
encoding an analog signal to provide a number of signal
points over the time period T 1+T2 ;
adding each one of the signal points to a respective
symbol of the symbol block to provide a number of
resultant signal points; and
transmitting the number of resultant signal points.
12. The method of claim 11 wherein the symbol block has
a data segment and a control segment, wherein the J data
symbols are contiguously located within the data segment
and the K control symbols are contiguously located within
the control segment.
13. The method of claim 11 wherein the data symbols and
the control symbols are selected from the same signal space.
14. The method of claim 11 wherein the control information conveyed by a current symbol block is a function of a
succeeding symbol block.
15. The method of claim 14 wherein the control information represents adaptive gain information for the succeeding
block.
16. The method of claim 14 wherein the control information conveys data rate information for a succeeding symbol
block.
17. The method of claim 12 wherein the control segment
represents a fixed number of bits, Y, which is equal to the K
control symbols within a symbol block multiplied by a y
number of bits from each of these control symbols.
18. The method of claim 17 wherein each control symbol
represents x bits, and x>y.
19. The method of claim 18 wherein duplicate control
information is conveyed by x-y bits of each control symbol.
20. The method of claim 11 wherein the data symbols
represent a synchronous data stream.
21. The method of claim 11 wherein the data signal
represents an asynchronous character stream, each asynchronous character having a start and a stop bit.
22. The method of claim 21 wherein the data encoding
step removes the start and stop bit from each asynchronous
character.
23. A method for use in a modem comprising the steps of:
demultiplexing a stream of received signal points from a
far-end modem to provide a plurality of signal point
streams;
decoding each one of the plurality of signal points streams
to provide a respective plurality of symbol streams; and
decoding each one of the received signal points as a
function of the plurality of symbol streams to provide
an analog signal.
24. The method of claim 23 wherein the analog signal is
a voice signal.
25. The method of claim 23 wherein the step of decoding
each one of the plurality of signal points streams further
includes the steps of:
providing a data signal from one of the plurality of signal
point streams; and
providing a control signal :from a different one of the
plurality of signal point streams.
·
26. The method ·of claim 25 further including the step of
adjusting the analog signal as a function of information
conveyed by the control signal.
27. Apparatus for transmitting a side-channel in a simultaneous analog and digital communications system, the
apparatus comprising:
means for multiplexing a plurality of symbol streams to
provide a sequence of symbol blocks, where each

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39. The apparatus of claim 36 wherein the means for
symbol block includes a predefined number of symbols
transmitting is a quadrature amplitude modulator.
from each symbol stream; and
40. The apparatus of claim 36 wherein each symbol block
means for transmitting each symbol block;
includes a data segment and a control segment, wherein the
wherein the means for transmitting further includes a
means for adding to each symbol of each symbol block 5 number of data symbols are contiguously located within the
data segment and the number of control symbols are cona signal point before transmission.
tiguously located within the control segment.
28. The apparatus of claim 27 further including a means
41. The apparatus of claim 40 wherein at least one of the
for encoding an analog signal to provide the signal point.
control symbols represents information about a succeeding
29. The apparatus of claim 27 wherein the analog signal
10
is a voice signal.
symbol block.
30. The apparatus of claim 27 wherein the plurality of
42. The apparatus of claim 40 wherein the control symsymbol streams is a data symbol stream and a control
bols represent secondary data.
symbol stream and each symbol block includes a data
43. The apparatus of claim 40 wherein the data symbols
segment and a control segment, wherein the data symbols of
represent a synchronous data stream.
each symbol block are contiguously located within the data 15
44. The apparatus of claim 40 wherein the data signal
segment and the control symbols of each symbol block are
represents an asynchronous character stream, each asyncontiguously located within the control segment.
chronous character having a start and a stop bit and wherein
31. The apparatus of claim 30 wherein the control segthe means responsive to a data signal removes the start and
ment represents a fixed number of bits, Y, which is equal to
20 stop bit from each asynchronous character.
the number of control symbols within a symbol block
45. A modem apparatus comprising:
multiplied by a y number of bits from each of these control
means for demultiplexing a stream of received signal
symbols.
points from a far-end modem to provide a plurality of
32. The apparatus of claim 31 wherein each control
signal point streams;
symbol represents x bits, and x>y.
25
33. The apparatus of claim 32 wherein duplicate control
means for decoding each one of the plurality of signal
information is conveyed by x-y bits of each control symbol.
points streams to provide a respective plurality of
34. The apparatus of claim 30 wherein the data symbols
symbol streams; and
represent a synchronous data stream.
means for decoding each one of the received signal points
35. The apparatus of claim 30 wherein the data symbols
as a function of the plurality of symbol streams to
represent an asynchronous data stream without the start and 30
provide an analog signal.
stop bits.
46. The apparatus of claim 45 wherein the analog signal
36. Modem apparatus comprising:
is a voice signal.
means responsive to a data signal for providing a stream
47. The apparatus of claim 45 wherein the means for
of data symbols, each data symbol selected from a first 35
decoding each one of the plurality of signal points streams
signal space;
further includes:
means responsive to at least one control signal for promeans for providing a data signal from one of the plurality
viding a stream of control symbols, each control symof signal point streams; and
bol selected from a second signal space;
means for providing a control signal from a different one
means for developing a number of symbol blocks, each 40
of the plurality of signal point streams.
symbol block comprising a number of the data symbols
48. The apparatus of claim 47 further including a proand a number of the control symbols;
cessing means that is responsive to the control signal for
means responsive to an analog signal for providing a
adjusting a parameter of the means for decoding that prostream of signal points;
45 vides the analog signal.
means for adding each one of the signal points to at least
49. The apparatus of claim 47 wherein the data signal
some of the symbols of each symbol block to provide
represents a sequence of asynchronous characters and the
an stream of resultant signal points; and
means for providing a data signal adds a start bit and a stop
bit to each character in forming the data signal.
means for transmitting the resultant signal point stream.
37. The apparatus of claim 36 wherein the analog signal
50. The apparatus of claim 47 wherein the means for
50
is a voice signal.
providing a control signal also provides a secondary data
signal.
38. The apparatus of claim 36 wherein the means for
developing includes a counting means for counting each
dam symbol and control symbol in each symbol block.
* * * * *