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A1: The International Telecommunications
Union (ITU-T), sets the standards for modem protocols
used worldwide. In early February, the ITU-T 56K
standard was "Determined". This means
that a published technical standard outlining the
method for communicating at 56K will be available
for all modem vendors to implement. This "Determination"
was approved on February 5, 1998. The ITU-T is expected
to ratify the V.90 standard in early Fall of 1998.
A2: Testing show that most users
are able to get a connections from 42-52 Kbps. There
are other factors that come into play as well, primarily
being how many analog-to-digital conversion occur
between your phone and the telephone comapny's central
site. These may factors may preclude your 56K modem
from performing optimally.
A3: The basic concept behind this
communications technology is that the public switched
telephone network (PSTN) is increasingly a digital
rather than analog network. Existing analog modems,
such as V.34, "see" the PSTN as an analog
system, even though the signals are digitized for
communications throughout most of the network. Rockwell's
56Kbps technology looks at the PSTN as a digital
network which just happens to have an "impaired"
section represented by the copper wire connection
between the central office and the user's home,
usually referred to as the analog local loop. To
make the technology work over that analog loop,
it must "equalize" the line using special
technology that converts the signal samples seen
by the user’s modem into the equivalent of
what is being sent from the central office.
A4: No, the techniques used in
V.34 (28.8Kbps) have been exploited to their limits.
This is a new technique where the network is viewed
as a digital transmission medium and the data is
encoded for transmission over the user’s telephone
line, also known as the analog local loop
A5: Yes, if one is a central-site
modem with a digital connection to the network.
On the other hand, two end-user modems incorporating
this technology will not connect using this technique.
Furthermore, 56Kbps speeds can only be achieved
on good line conditions.
A6: 56Kbps technology-will primarily
be used for faster web browsing and Internet access
and for faster remote access to corporate LANs that
digitally connect to the PSTN.
A7: Shannon's limit is theoretically
determined by the impairments (noise) in the telephone
link. This new technique relies on a reduced noise
environment due to a digital connection to the network
by the service provider and a new encoding technique
A8: Actually, the concept has
been around for a number of years but it hasn't
been practical because most modems installed at
service providers used to use analog connections
to interface to the network
A9: It is neither a compression
algorithm nor a modulation scheme. Data is actually
passed on the telephone line at 56Kbps. It is a
technique for encoding data for transmission over
the telephone line -- we prefer to refer to it as
an encoding technique instead of a modulation scheme.
A10: In modulation, a carrier
is modified so that it carries information. Ordinary
modems modulate a carrier to carry digital data.
In this new technique we encode the data. By "encoding,"
we mean that data is sent in digital form through
the network, and encoded in such a manner that it
can pass through the user's analog telephone link
at a high rate.
A11: There are no relationships.
In reference to all of these techniques the advantage
of this new technique is that it works over the
existing switched telephone network. It does not
require the telephone company to replace or add
any new equipment.
A12: ISDN, which provides two
64Kbps channels has not yet achieved a significant
penetration in the home market. This 56Kbps technology
will allow users to gain the speed advantages of
almost one ISDN channel without having to order
and pay for a new ISDN telephone line.
A13: This technology does not
require new services. It will utilize the existing
analog telephone service.
A14: Theoretically, the technology
can approach 64Kbps; however there are a number
of practical problems with achieving this speed
including line noise. non-linear distortion, the
quality of the network coded and others. The industry
is working to push the technology to its highest
possible data rate, and rates near 64Kbps may be
possible in the future.
A15: Similar to end-users the
ISP must have equipment that includes modems which
support this technique. Additionally, the ISP must
utilize a digital connection to the network. This
will be an extremely straightforward process for
ISPs who are installing new central-site equipment
featuring the new 56Kbps modems. However ISPs who
wish to upgrade existing central-site equipment
to the new 56Kbps technology face two additional
issues.Firsts ISPs will probably wish to use ISDN
Primary Rate Interface (PRI) network connections
rather than lower-performance T1 "robbed bit"
interfaces. All other things being equal, users
will be able to connect at a higher rate to an ISP
utilizing ISDN PRI than to one utilizing a T1 "robbed
bit" signaling. Many ISPs, therefore, will
want to upgrade their network interface to ISDN
PRI, as well as adding 56Kbps modem capability to
their central-site equipment.Second, ISPs will need
to make sure that their equipment provides adequate
compression performance at 56Kbps operation. Without
adequate compression performance, the "effective
throughput" may not be much better than what
users experienced at 28.8 Kbps or 33.6 Kbps. Some
of the central-site modems which are being promoted
as "upgradeable" to a 56Kbps encoding
scheme may only have enough processing power to
support adequate compression performance at 28.8Kbps
and 33.6Kbps speeds. In these cases, users may not
experience better throughput than when they were
operating at 28.8Kbps or 33.6Kbps speeds. This is
an especially insidious problem because it occurs
at the central site, out of the control of the user.
Even if the user has purchased a new 56 Kbps modem,
the throughput may be limited by poor compression
performance at the central site.
A16: It is important to first
understand how modems work. Data is first sent into
a modem, where it is compressed and sent over the
telephone line to another modem, where it is then
decompressed. The amount of data that can be sent
into the modem and effectively transmitted to the
other end is called the effective throughput. The
level of compression that the modem's processing
power can support affects the effective throughput.
The better the compression, the higher the effective
throughput. And the higher the effective throughput,
the faster the Web pages will come up on the user's
screen.
A17: Products incorporating this
new technology will also contain all previous modem
modulations, including V.34, V.32bis, and facsimile
modulations. During the initial stages of a connection
the two modems will determine what modulation and
at what speed the transmission will occur.
A18: It is more difficult to
equalize the upstream channel, and therefore more
difficult to achieve the same high data rates as
are achieved in the downstream charmed However,
for Internet access, the data rate in the upstream
direction is less important than downstream, since
the upstream channel transmits mostly "key
strokes and mouse clicks." At present, a data
rate of around 30 Kbps can be attained in the upstream
directional but research continues toward increasing
that rate.
A19: Although it appears that
most companies are using the same basic technique
to achieve 56Kbps operation the specific design
choices are unlikely to be the same. However, if
two modems are unable to connect at 56Kbps, they
will drop down to a mutually interoperable industry-standard
data rate like 28.8Kbps or 33.6Kbps. Rockwell is
working with the appropriate standards bodies, toward
the development of a ratified specification that
will serve as a worldwide interoperability vehicle.
A20: The ITU sets international
standards and thus would be the preferred standards
body for this technology. On November 13, 1996,
Rockwell Semiconductor Systems hosted the TR-30
Pulse Code Modulation (PCM) ad hoc group, the first
standards meeting aimed at creating draft standards
for PCM modem technology. These draft standards
are being developed to ensure interoperability between
56Kbps products from a broad spectrum of modem vendors
and other communications equipment suppliers. Rockwell
was joined at the meeting by a number of leading
U.S. PC and communications companies including Intel,
Lucent, gayest Motorola, IBM, Compaq and Cisco.
This ad hoc committee has been created under the
direction of the Electronics Industry Association
(EIA) and Telecommunications Industry Association
(TIA) to develop an EIA/TIA interim standard for
U.S. 56Kbps PCM modems by mid-1997. The TIA TR-30
group also will serve as the advisory committee
to the U.S. government on modem-related issues involving
the International Telecommunications Union (ITU).
It is expected that the group's interim work in
the U. S. will form the basis for a U.S. submission
to the ITU for a worldwide standard for 56Kbps modem
technology. Rockwell is a charter member of this
TIA group and is the assistant editor for the draft
standard, working with Motorola.
A21: Interoperability is critical
to any modem technology. In the case of 56Kbps modems
the technology introduces new issues which may require
slightly different handling by the industry standards
bodies as compared to previous 28.8Kbps and 33.6Kbps
efforts. Rockwell is working with a number of other
leading PC, modem, and telecommunications equipment
vendors to address these new issues which may impact
the future success of 56Kbps modems. Also, Rockwell
has joined with Lucent to announce that the two
companies will make their 56Kbps modem chipsets
interoperate at 56 Kbps. Agreements like this help
to ensure that customers who purchase a modem that
implements Rockwell's K56Plus will have the highest
probability of achieving a connection at speeds
up to 56Kbps.
A22: The diffusion rate for a
new modem technology like this will be slow, and
it is critical that the industry develop worldwide
standards. Early installations of 56Kbps will likely
be "show POPs" rather than general deployment.
Network operators will likely move slowly to avoid
problems for their users. The issue of "which
56Kbps?" will disappear when there are standards.
Rockwell is an active participant in the standards-development
process, and is also working very closely with the
central-site equipment suppliers who provide the
critical ISP technology to make 56Kbps work.
A23: No, this new technology
will work over a single existing analog phone line.
A24: The user must have a modem
which implements this new technology.
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