Telephonic communications – Telephone line or system combined with diverse electrical... – Having transmission of a digital message signal over a...
Reexamination Certificate
2000-04-24
2004-03-09
Eng, George (Department: 2643)
Telephonic communications
Telephone line or system combined with diverse electrical...
Having transmission of a digital message signal over a...
C379S093320, C375S219000, C375S222000
Reexamination Certificate
active
06704399
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to communication systems. More particularly, the present invention relates to speeding up the connect time between communication systems.
BACKGROUND OF THE INVENTION
56 kbps modems are now standardized in accordance with the ITU V.90 Recommendation. However, many 56 kbps modems, particularly end user modems, may only be compatible with legacy modes such as K56flex, V.34, V.FC, and V.32. Such legacy modems, and downwardly compatible V.90 modems, may have an undesirably long connect or initialization time between dial-up and full rate data mode. The startup time can be up to 30 seconds, which can be rather annoying and unattractive from the perspective of the end user, especially in light of other data communication protocols that appear to operate in an “always connected” manner.
V.90 modems that support legacy modem protocols typically perform the functions shown in Table 1 during initialization. The time periods associated with the operations set forth in Table 1 may vary from connection to connection depending upon various factors such as the server speed and channel conditions.
TABLE 1
Conventional V.90 Modem Startup
PROTOCOL
OPERATION
TIME (seconds)
—
Dialing
1
—
Call Establishment
1
V.8bis
Capabilities
3.5
Exchange
V.8
Capabilities
3.5
Exchange
V.90 Phase 2
Probing & Ranging
1.5
V.90 Phase 3
Digital Impairment
8.5
Learning; Initial
APCM Training
V.90 Phase 4
Final APCM
2.5
Training; Set Power
Levels; Constellation
Transmission
V.42/V.42bis
Error Correction;
0.5
Data Compression
—
Login
0.55
TOTAL =
22.5-27.0
The V.8bis operation includes a relatively long timeout period that encompasses much of the time period associated with the operation. This operation is described in detail in ITU-T Recommendation V.8bis (International Telecommunication Union, August 1996), the content of which is incorporated by reference herein. The V.8bis protocol is an extension of the V.8 protocol, as described in ITU-T Recommendation V.8 (International Telecommunication Union, February 1998), the content of which is incorporated by reference herein. In accordance with V.8bis and/or V.8, the two modem devices exchange their individual capabilities such that compatible protocols may be utilized during subsequent initialization and data communication procedures.
The various V.90 startup phases are utilized to determine the analog and digital channel characteristics, to train the modem equalizers, and to otherwise attempt to optimize the current communication session. The details of the V.90 startup phases and other aspects of a V.90 modem system may be found in ITU-T Recommendation V.90 (International Telecommunication Union, September 1998), the content of which is incorporated by reference herein. Although a portion of the V.90 startup segments shown in Table 1 are required without regard to the location or status of the client modem, many of the operations could be eliminated or shortened upon repeated connections associated with the same (or nearly identical) channel characteristics.
In a conventional V.90 modem system, error correction and data compression techniques are performed during the V.42/V.42bis stage. The specifics of V.42 are contained in ITU-T Recommendation V.42 (International Telecommunication Union, October 1996), the content of which is incorporated by reference herein. The specifics of V.42bis are contained in ITU-T Recommendation V.42bis (International Telecommunication Union, January 1990), the content of which is incorporated by reference herein. The V.42 operation is desirable such that the modem system can perform the login procedure in a substantially “error free” mode. The login procedure may be conducted with CHAP and PAP protocols; both are utilized for security purposes in the context of point-to-point protocol (“PPP”) connections, e.g., a connection between a client computer and an internet service provider server. From the perspective of the V.90 modem devices, the login information is transmitted as data. Once the login procedure is performed, the dial-up connection is complete and data may be transmitted between the server and the host software associated with the client.
The widespread use of the internet as a daily research, entertainment, and communication tool has increased the deployment of 56 kbps modems. However, many channels can only support legacy modes such as V.34. Thus, although most newer modems (particularly those sold with new personal computers) are compatible with the V.90 Recommendation, many legacy modes are still in use. The long initialization period associated with V.90 modems that fall back into legacy modes may be annoying and undesirable in many applications and can be a serious hindrance where a user would like to establish an immediate connection after an unanticipated disconnect. In addition, even in the context of a connection between two V.90 modem devices, the long V.90 startup phases may test the mettle of an impatient end user. Accordingly, it would be highly desirable to reduce the initialization time normally associated with a conventional V.90 modem system.
A given modem communication session may be interrupted or disconnected for any number of reasons. For example, a call waiting signal may disrupt a modem connection to the extent that the modem call must either be reconnected or reinitialized. As another example, it may be possible to place a current modem connection on hold to enable the user to answer an incoming call in response to a call waiting signal or to enable the user to place an outgoing call without disconnecting the modem connection. Ideally, the modem connection could be re-established in an instantaneous manner. However, in a practical system, a retraining or reinitialization procedure must be carried out to ensure that the two end devices are properly synchronized and to ensure that the channel is adequately equalized. As discussed above, conventional V.90 modem systems may spend more than 20 seconds during such retraining and reinitialization. Accordingly, it would also be desirable to reduce the reconnection time between the same modem devices in response to a temporary disconnect or a temporary pause in the data communication.
One major time consuming portion of modem training and negotiation occurs during parameter exchanges, such as exchange of data signaling rate, preceding coefficient, spectral shaping, constellation information and etc. With reference to
FIG. 5
, it is shown that, for example, during V.90 negotiations, an analog pulse code modulation (“APCM”) modem 580 transmits a constellation parameter (“CP”) frame
510
to a digital pulse code modulation (“DPCM”) modem
590
that, in-exchange, transmits a modulation parameter (“MP”) frame
520
to the APCM modem
580
. The MP frame
520
and the CP frame
510
are in synchronous form and include many bits of information and CRC information for error checking purposes (see FIGS.
17
and
18
), as further described below.
As shown in
FIG. 5
, the APCM modem
580
continuously transmits CP frames
510
to the DPCM modem
590
until the APCM modem
580
receives a receipt acknowledgement from the DPCM modem
590
for one of the transmitted CP frames
510
. Similarly, the DPCM modem
590
continuously transmits MP frames
520
to the APCM modem
580
until the DPCM modem
590
receives a receipt acknowledgement from the APCM modem
580
for one of the transmitted MP frames
520
.
The receipt acknowledgement for the CP frame
510
is transmitted in the form of an MP frame
520
, including each and every bit of information and having the acknowledgement bit
33
of the MP frame
520
set to a “1”. The MP frame
520
having its acknowledgement bit
33
set to a “1” is denoted as MP′ frame
522
. Once the DPCM modem
590
receives a CP frame
510
, the DPCM modem
590
starts transmitting the MP′ frames
522
instead of the MP frames
520
. This repeated transmission of MP′ frames
522
continues until the DPCM modem
590
receives a receipt acknowledgement for the M
Conexant Systems Inc.
Eng George
Farjami & Farjami LLP
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