The Original Shareware 1.1/The Original Shareware (WeMake CDs)(Volume 1.1)(CDs, Inc)(1993).iso/7/comproto.zip/PAPER-03.TXT

Text File | 1991-01-03 | 16KB | 346 lines

                           9600 White Paper






                 THE MIGRATION TO 9600 BPS COMMUNICATIONS
                          FOR PERSONAL COMPUTERS







                    Hayes Microcomputer Products, Inc.
                             705 Westech Drive
                          Norcross, Georgia 30092






INTRODUCTION


        Whether you look at man's transportation of himself or the
"transportation" of his information, the trend has always been toward
a faster and more efficient means.

        Our trend in communications has enabled us to evolve from
carrier pigeons and the Pony Express to the telegraph and telephone
and into microwave and fiber optic data transmission.

        Our quest for faster communications continues.




MODEMS AND THE MIGRATION TOWARD INCREASED SPEED AND FUNCTIONALITY

        Early modems were not intelligent devices, but simply
translators which had to be opened prior to each hookup in order to
rather laboriously set a series of switches that controlled the
options that configured the modems' operation for the particular
system they were connected to.

        Acoustic couplers, suction cup-like receptacles used with
telephone handsets, while not as difficult to set up, were prone to
error because of external noise or vibration.  They also involved
manual operation of dialing the phone, listening for a special tone
from the receiving modem, and placing the headset in the coupler.
This hands-on requirement, of course, eliminated the possibility of
automated operation and bogged down the communications process.

        This unsophisticated environment of the late 1970s was ripe
for an automated product that could streamline establishing and
conducting data transmission activities in the Public Switched
Telephone Network (PSTN).



HAYES MODEMS AND THE HAYES STANDARD AT COMMAND SET

        Hayes Microcomputer Products, Inc. introduced its innovative
modem series to fill this void that existed in the communications
environment.  By providing modems that were both easy to use and
simple to connect directly to the PSTN, the problems the error-prone
acoustic connection had been solved.

        Using these new modems meant the terminal or personal
computer operator could control modem functions (such as dialing
numbers or switching from command to on-line modes) from a keyboard
or through communications software.  This meant that communications
had taken a great step forward since operation was now automated and
repetitive activities (calling an on-line service and automatically
logging on) could be stored and repeated quickly and more
efficiently.

        What made the automation possible?

        By this time, microprocessors had progressed to a significant
functional level and could provide a means for the modem to execute
instructions coming from the terminal or personal computer.  Since
the modem now had the ability to interpret character strings sent to
it and could respond with result codes, it was easier to control.
The microprocessor enabled the modem to become a system element that
was easier to integrate into the computer environment.

        The solution to modem control was the Hayes Standard AT
Command Set.  By taking all of the available standards for the data
and physical aspects of communications (Bell 103C modulation, RS-232C
physical interface, ASCII data format, and RJ-11 phone connector) and
innovating on top of them, Hayes developed a new industry standard.

        The results were the first intelligent modem products to
        enjoy widespread distribution and use.


INCREASED TECHNOLOGICAL ADVANCES

        Introduced in 1981, the Hayes Smartmodem 300 implemented the
Bell 103 telephone signalling standard which uses Frequency Shift
Keying (FSK).  FSK is limited to lower speeds as a result of band
width limitations of the voice telephone channel.

        True to history, personal computer modem users wanted more.
Specifically, they wanted more speed with high data transfer
accuracy.

        Modulation techniques were developed to permit increased data
rates.  Phase Shift Keying (PSK) allowed modems to quadruple their
speed to 1200 bits per second (bps) communications.  This method of
transmission is considerably more complex than and increased the
modulation/demodulation capabilities required of the modem.

        Both the Hayes Smartmodem 1200, introduced in 1982, and the
Smartmodem 1200B, introduced in 1983, adhere to the PSK standard
known as Bell 212A and can communicate with other modems which also
use this signalling standard.

        Users once again demanded more speed and functionality, and
2400 bps communication implementing Quadrature Amplitude Modulation
(QAM) was developed.  Higher speeds meant the modems needed more
sophisticated signal processing circuitry to enable reliable higher
speed data transfer over the PSTN.

        In addition to 2400 bps communication speed, both the Hayes
Smartmodem 2400, introduced in 1984, and Smartmodem 2400B, introduced
in 1985, included call progress monitoring, adaptive equalization,
self testing, and the ability to communicate both asynchronously and
synchronously.


EMPHASIS ON INTERNATIONAL STANDARDS

        Our evolution into a more global society presents new
challenges and opportunities for personal computer communications.

        The rise in importance of standards setting bodies such as
the International Telegraph and Telephone Consultative Committee
(CCITT) is a reflection of the need for the establishment of global
standards for interconnection of communications equipment.

        The work of the CCITT has resulted in the establishment of
the V.22 and V.22bis recommendations for 1200 bps and 2400 bps
communications.  Users can confidently purchase modems adhering to
these standards and be assured that communications with other modems
(even in foreign countries) applying these standards will be
compatible.

        All Hayes 1200 bps and 2400 bps modems are CCITT V.22 and
        V.22bis compatible and country-specific models have been
        approved for distribution in North America, Europe, Central
        America, the Middle-East, and the Pacific Basin.


9600 BPS COMMUNICATION

        When data transmission speed for personal computer modems
accelerated from 300 bps to 1200 bps, the technological hurdles were
rather lofty.  By comparison, the migration from 1200 bps and 2400
bps to 9600 bps for dial-up modems was far more complex than the
earlier advances.

        The CCITT V.29 recommendation originally addressed 9600 bps
communications over four wire leased lines.  At the time of the
recommendation's drafting, the opinion was that dial-up lines would
not support 9600 bps communications.

        As the quality of transmission lines on the PSTN improved,
manufacturers began to re-orient the CCITT standard by introducing
dial-up 9600 bps half-duplex V.29 modems using QAM techniques for
transmitting data.  This approach for modulation is similar to the
method used for handling 2400 bps transmission.

        Communications equipment manufacturers perceived the need for
full-duplex 9600 bps dial-up modems and the CCITT responded with its
V.32 recommendation.

        V.32 modems are very expensive due to the echo cancellation
technology the modems require.  Echo cancellation allows the modem to
ignore its own transmission and "focus" itself on the incoming data
signal from the remote modem during full-duplex transmission.  This
increases the complexity of the modem and the technology to
accomplish it is costly.

        Additionally, a characteristic associated with personal
computer data communications applications is one-way communication.
For example, in downloading a large data file from a mainframe to a
personal computer, the data flow is essentially in direction.  So,
V.32 full-duplex capability is not only expensive, but for most
personal computer data communications applications it is also
unnecessary.

        What, then, are the options for affordable 9600 V.32
communications?


HAYES V-SERIES 9600 BPS MODEMS

        Hayes has developed the V-series Smartmodem 9600 and the
V-series Smartmodem 9600B, 9600 bps half-duplex, fast-turnaround
modems providing simulated full-duplex V.32 dial-up communications at
a considerably lower price compared to V.32 modems.

        Both modems implement Hayes-exclusive fast turn-around
technology.  By providing such rapid turn-around of the
communications link, users receive the benefit of fast data transfer
through simulated full-duplex at a reasonable cost.  This fast
turn-around allows data alternately to flow at 9600 bps in either
direction.

        When high capacity is needed in one direction, that direction
gets use of the channel for longer periods.  These periods, however,
are always short enough that reverse data is not delayed appreciably.


TRELLIS CODE MODULATION

        Both Hayes 9600 bps modems implement the Trellis Code
Modulation (TCM) scheme as described in the CCITT V.32 specification
to add forward error correction to the basic signal.

        TCM is especially important as the telephone companies
continue to implement Adaptive Differential Pulse Code Modulation
(ADPCM).  ADPCM is a voice signal encoding scheme that allows the
phone companies to double the channel capacity of digital trunk
lines.  Unfortunately, V.29 and V.32 modems that use Quadrature
Amplitude Modulation (QAM) without Trellis Coding will not be able to
communicate successfully at 9600 bps when an ADPCM link is
encountered.  Modems without TCM will have their speed limited to
only 4800 bps on ADPCM lines.  The Hayes 9600 bps modems' TCM feature
makes them more readily adaptable to the present and future demands
and constraints of the PSTN.

        TCM can provide up to a four decibel improvement of
signal-to-noise ratio when compared to a non-TCM scheme such as V.29.
That improvement may appear small, but it provides huge dividends.
Improving the signal to noise ratio allows a TCM modem to provide
high quality, reliable communications over dial-up lines that can
eliminate the need for using costly, conditioned, leased lines for
9600 bps communications.  This enables the Hayes 9600 bps modems to
achieve dial-up line performance with that of the Smartmodem 2400 or
other V.22bis modems.


ERROR-CONTROL

        Both Hayes 9600 bps modems implement the LAPB link level
portion of the X.25 protocol for error-control at 2400 bps and 1200
bps.  CCITT X.25 is a versatile and widely used synchronous protocol
standard that enjoys popularity as a worldwide standard.  At 4800 bps
and 9600 bps both modems implement an error-control ping pong
protocol which is an extension of LAPB. Use of this protocol paves
the way for future Hayes products to continue the migration toward
the standardized, synchronous communications environment that lies in
the future.


ADAPTIVE COMPRESSION

        Adaptive Data Compression in Hayes 9600 bps modems typically
increases the data throughput to speeds of 19,200 bps.  Using a
Hayes-developed algorithm, data is compressed in real time,
dynamically adapting to changes in the data being transmitted.

        This operation is transparent to the user and the amount of
compression that occurs within the modem depends upon the type of
data being transferred.  Spreadsheet, data, and text files will
typically flow in and out of the modem at 19,200 bps using the
standard asynchronous data port.  Other files will also experience
improved throughput due to data compression between the modems.


AUTOMATIC NEGOTIATION

        Automatic Feature Negotiation capabilities in both the
V-series Smartmodem 9600 and V-series Smartmodem 9600B provide users
with automatic setup of the error-control link.

        During the initial modem "handshake" the local and remote
modems will connect at the data rate set in the answering modem.  If
the answering modem is set to a lower speed, the originating modem
can fall back from 9600 bps to 4800 bps, 2400 bps, 1200 bps, or 300
bps for maximum flexibility in establishing a connection.

        Once the "handshake" is completed, detection of a
non-V-series protocol device or synchronous-only device at the remote
end occurs.  Then, the negotiation of link parameters such as
synchronous or asynchronous transmission, asynchronous transparency
mode, or link address is conducted.  The devices can also coordinate
the use of X.25 LAPB or Asynchronous Framing Technique (AFT).  AFT is
an asynchronous augmentation for any bit-synchronous protocol such as
LAPB, LAPD, or SDLC.  It the lowest part of the link level of the
synchronous protocol and brings error-control operation to
asynchronous transmission links.  Again, an existing standard has
been built upon to continue the evolution of the communications
environment.


PRACTICAL APPLICATIONS FOR 9600 BPS COMMUNICATIONS

        The requirement for more speed is universal and the
applications for the V-series Smartmodem 9600 and V-series Smartmodem
9600B permeate virtually every area of business.  By combining high
speed and data compression to improve throughput over an
error-control link, the Hayes 9600 bps V-series system modems
continue the company's tradition for providing fast, reliable data
communications equipment.

        By using high speed communications when connecting personal
computers to corporate mainframes, users can save both money and
time.  Faster transfer of data means shorter long distance connect
time and translates quickly into significant dollar amounts.
Additionally, faster data transfer means better utilization of time
and shortening the length of time a personal computer is tied to the
mainframe frees both systems to undertake additional, more useful
activities.  So, whether the data transferred is a quarterly sales
report, monthly training schedule, or a credit application for
processing, 9600 bps error-control communications offers significant
opportunities to improve efficiency.

        Additionally, terminal to mainframe communications can
expedite functions essential to maximize customer service and
maintain a competitive edge.  Integrating order entry equipment and
cash registers into an inventory management system through 9600 bps
modems can improve an organization's ability to manage inventory and
ensure proper coordination throughout the distribution channel.


THE HAYES COMMITMENT

        As the leader in communications hardware and software
products for personal computers, Hayes has developed its products to
adhere to the established standards of the industry.  It is our
intention to do so in the future and to innovate where no standards
exist to augment the implementation of high speed, advanced
technology products.  Our commitment to quality, service, and value
will allow users of Hayes products to benefit from that commitment in
the future as they have in the past.