Q1: Is K56flex™
technology a further refinement of V.34 technology and will
it be used in the same home-to-home applications?
A: No. K56flex™ technology is based on a
totally different concept from the V.34 modems widely used
in home-to-home connections as shown in Figure 1. It takes
advantage of today's Internet access explosion which creates
a new connection topology where the end-user modem connects
via analog phone line to a server site modem which is
directly linked to the digital telephone network via a T1 or
PRI line (shown in Figure 2). This
new type of connection can therefore b e defined as a
home-to-ISP (Internet Service Provider) connection.
Figure 1. Typical home-to-home V.34 modem
connection
Figure 2. K56flex™ in home-to-ISP connection
Q2: What is
K56flex™ Technology?
A: Lucent and Rockwell on 11/15/96 announced their
intention to make their respective modem chip sets
interoperable. By agreeing to interoperate, Lucent &
Rockwell are providing the industry with an interoperable
high speed modem protocol that will revolutionize Internet
communications. The interoperable high speed modem protocol
is called K56flex™.
Q3: What companies have
announced support for K56flex™
technology?
A: So far, America Online, Ascend Communications,
BBN, Best Data, Compaq Computer, Earthlink, Concentric
Networks, Diamond Multimedia, Hayes Microcomputer Products,
Hewlett-Packard, Livingston, Multi-Tech Systems, Motorola,
Prodigy, UUNet, and Xirc om have announced they will use
K56flex™, and over 700 ISPs and manufacturers
are endorsing the K56flex™ technology. The main
thrust of these announcements is that these companies
endorse interoperability of the K56flex™ ;
technology because they recognize the importance of an
interoperable high-speed modem technology.
Q4: How can
K56flex™ achieve faster speeds than V.34 33.6
kbits/s which is already very close to the well-known
Shannon's limit of channel capacity?
A: Shannon's Law theoretically defines the maximum
channel capacity (line speed) based on the impairments
(including all kind of noise) in the telephone link between
two points and the bandwidth of the channel. In home-to-home
connections (shown in Figure 1), the
telephone network will first convert the analog signal
transmitted from user A's modem to a digital signal which
will the n be transmitted digitally from the central office
in user A's area to the central office in the user B's area
where the digital signal will be converted back to an analog
signal before being sent via analog phone line to user B's
modem. The noise introdu ced by the telephone network's
analog-to-digital converter is a dominant impairment (called
quantization noise) in this type of connection in which the
maximum speed is therefore determined by Shannon's Law at
around 35 kbits/s. In a home-to-ISP type of c onnection
(shown in Figure 2),
K56flex™ takes advantage of the fact that the
network has no analog-to-digital conversions in the
end-user's downloading (downstream) path and effectively
eliminates the quantization noise impairments introduced by
the telephone network.
Q5: What are the keys to
K56flex™?
A: K56flex™ takes advantage of having
direct access to the digital telephone network at one end of
a connection. First, the end point K56flex™
modem must synchronize with the telephone network's digital
system. Secondly, the ISP K56flex™ modem will
encode and map the bit stream into the different symbols
matching the telephone network's digital system (µ- or
A-law PCM). Those bit-encoded symbols will then be
represented as different voltage levels in an ana log format
and will be received by the end point K56flex™
modem. Lastly, the end point K56flex™ modem has
to equalize the channel with respect to analog loop
characteristics and intersymbol interference (ISI).
Q6: Will the upstream speed
be limited to V.34 rates?
A: Not necessarily. The initial version of
K56flex™ will use V.34 rates for upstream
(uploading), which has been selected by the TIA for the U.S.
interim high speed modem standard. Lucent is expecting to
upgrade its future K56flex™ product software,
via its RAM based solution, which will utilize additional
techniques to enable rates higher than V.34 rates in the
upstream direction. Again the key is having digital access
at one end of the connection which is not available in a
home-to-home connection. With only one analog loop in the
path, there are fewer impairments than conventional V.34
connections (2 loops). Higher rates and better performance
than V.34 are expected.
Q7: Is a modem useful if the
highest speed is offered in only one direction?
A: Traditional Internet access is a highly
asymmetrical process in that most data flows from the
Internet to the end user (downstream) in the form of
graphics or files. Most communications from the end user to
the Internet (upstream) is button clicks or address entries.
K56flex™ is therefore ideal for Internet
connections.
Q8: Is a "home-to-ISP" user
connection to the Internet the only application for
K56flex™ technology?
A: No. This technology is useful for several
applications where one end of the connection is digitally
terminated. Some alternate applications include enterprise
solutions where users connect to a private business server,
bridging connections where a service provider utilizes two
or more digitally terminated modems and two or more end
users call in to these modems and have their data bridged
digitally by the service, and finally, end-user digitally
terminated modems such as ISDN combo modems where an end
user is digitally terminated and can therefore communicate
with another end-user K56flex™ modem.
Q9: Can two
K56flex™ modems connect at rates higher than
V.34 when used in a home-to-home connection?
A: No. The K56flex™ technology is
uniquely designed for home-to-ISP connections with the
condition that one end (typically ISP site) has digital
access to the telephone network and the other end (typically
end-user) connects to an analo g phone line. However,
K56flex™ modems will automatically connect to
each other in V.34 mode when used in home-to-home
connections.
Q10: Will
K56flex™ modems interoperate with today's analog
modems such as V.34?
A: Yes. K56flex™ modems will
automatically detect the capabilities of a remote modem and
"automode" to the capability of the remote modem. Moreover,
if a combination of network and local loop conditions
prevent a K56flex™ connection, a fall back to a
V.34 connection will occur.
Q11: If I purchase a
K56flex™ modem, will I always connect at the
speeds possible with K56flex™
technology?
A: K56flex™ rates can be achieved
ONLY when they are used in pairs
(K56flex™ end-user modem connects to a
K56flex™ ISP-site modem). Therefore,
K56flex™ modems must be deployed at all the
sites you plan to call. As previously mentioned, a
K56flex™ modem will automode to V.34 if the
remote modem lacks K56flex™ capabilities or a
combination of network and or phone line conditions that
prevent a K56flex™ connection.
Q12: Will
K56flex™ modems connect with other high speed
modems announced recently by other manufacturers?
A: It appears that although the basic concepts used
in other high speed technologies are similar, it is unlikely
that the various protocols will interoperate.
K56flex™ compliant modems will interoperate with
ISPs that offer K56flex™ service.
K56flex™ modems will however fall back to a V.34
connection if the other modem is not a K56flex™
modem.
Q13: Won't this technology
hurt the market for ISDN?
A: Actually, ISDN can provide 128 kbits/s data
transmission without any compression, and can reach 512
kbits/s with compression. Also, keep in mind that the
fastest speed these modems can reach is dependent on the
phone line conditions and other network related issues. On
the other hand, with ISDN, 128 kbits/s is virtually
guaranteed. K56flex™ modems are designed to be
less expensive and easier to set up for end users that want
higher speed connections to the Internet.
Q14: Will
K56flex™ technology be available
internationally?
A: Yes. Although it will be initially deployed in the
United States, this technology will be deployed subsequently
in Europe and Asia. Most countries other than the United
States have A-law rather than µ-law compression, and
the algorithm takes this into account.
Q15: Who
Can Get 56flex™ Access
From Mia.Net?
A: All Mia.Net customers in the 514, 534, 537,
539, 763, and 767 dial prefixes (as of Feb 28, 1998)
Q16: Will my
dial in phone number change?
A: Yes. The new dial in number will change and you
will be notified by email and US mail of the new number.
Q17: Will
56flex™ Access cost
anymore?
A: No. Your access rate will remain the same.
Q17: How Fast is
56flex™?
A: It would be important to note the truth behind
56k. Is it really 56 kilobytes per second? Actually it is
closer to 31.900 or 37.600kilobytes per second. This
definitely is faster than the current speeds of 33.6,
however it is not as fast as 56k Flex, X2, and so many
others claim. For instance, an 56K modem can (theoretically)
receive at 56 kbps but transmits at 28.8 kbps. Also
important to note, your phone line may not be able to
support 56K speeds. For 56K to work, you can only have one
analog-to-digital conversion between your home or office and
the Internet service provider (ISP). If there's more than
one, you can't use 56K, and your connection will be limited
to V.34 speeds (a maximum of 33.6K).
Beyond all of this, do remember that according to FCC
Regulations, the telephone line can only be allowed to reach
53k speeds maximum.
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