Data Communication Technologies
Published in CORE, Sep/Oct, 1997
says computers are productivity tools but in today' s world of Internet
and Intranets, they are gradually taking up additional role of
communication tools. This transformation or encroachment into
communication area is mainly due to advancement in processing power,
better storage, reliable and faster communication technologies. In the
early days, computer communications were limited to simple text
transfers, now they are growing continually richer in feature and
function; as a result they are becoming more and more demanding. Today
computer communication includes multimedia, PC video conferencing, 3D
graphics which require millions of bytes to be transferred between
computers. It can now be mathematically proved that a picture (in
Megabytes) is worth a thousand words(in Kilobytes).
Massive growth of Internet in the
last couple of years has changed personal and business computing
paradigms. Many new applications such as database access via Internet,
teleconferencing, home office, distance learning, interactive TV
programming, video on demand, on line shopping are all closer reality
now. But trying to run these complex applications over a 28.8 Kbps (Kilo
~ Bits Per Second) dial-up connection or even a 10Mbps LAN is going to
be frustratingly slow.
Although no simple solution exists,
there are some new technologies on the horizon. Some of them are to
speed up remote and Internet access and the other accelerate LAN and WAN
connectivity. These technologies are likely to emerge between now and
the year 2000.
Unless you are one of those lucky ones using a
corporate or university LAN, you must be using an analog modem to access
Internet. Though analog modems have their limitations, they are still
the cheapest way to hook into the Internet. The new modems which utilize
V.34 protocol standards can achieve transfer rates up to 33.6 Kbps. But
it still does not help you much if you are downloading a good Cindy
In business sector ISDN (Integrated
Services Digital Network) is gradually getting its foothold, at least in
developed countries. As its name implies, ISDN can integrate voice and
data in the same communication channel and it is well suited for
multimedia applications. ISDN provides three separate channels on a
single copper telephone line, as opposed to one provided by analog
modems. These channels include two 64 Kbps B-Channels for voice and data
transmission and a 16 Kbps control channel. Protocols allow the two
B-channels to bond to become a single channel with transfer rate of 128
Kbps, which is nearly a few times that of the fastest among modems.
Present day communication
applications have become so demanding that even ISI)N does not look so
impressive as it was few years ago. People have already started calling
it "It Still Does Nothing". Also not all the countries offer
ISDN. Even if they are offered, the central telephone company switches
become the bottleneck as they were designed for basic voice
communication, hot for data communication.
Kbps Analog Modems
56 Kbps analog modem is on the lower end of
the emerging Internet technologies. This technology is based on chipsets
(K56Flex Technology) developed by Rockwell International Corp. US
Robotics already has released 56 Kbps modem under a trademark of x2:
Other modem vendors are also expected to follow suit.
Most developers and analysts still
believe that 33.6 Kbps is the maximum achievable rate for analog
transmission over normal telephone lines. This is due to the inherent
noise problem in telephone lines. The 56 Kbps modems work around this
limitation by capitalizing on digital conversion process that most
analog calls undergo at the phone company. In a typical client computer
to host computer communication, digital data from the client computer is
converted to analog signal, transmitted via public phone network and
finally converted back to digital signal at the host computer and vice
versa. The signal conversion is taken care of by analog modems. The
K56Flex technology takes advantage of the fact that many of the Internet
Service Providers use digital lines to connect to the telephone company.
So a higher speed can be achieved by eliminating the conversion process
at the server side. This imparts asynchronous characteristics to the 56
Kbps moderns making 56 Kbps transfer rate available for one way
(downstream, that is carrier to desktop) only, the upstream transfer
rate can be as high as 33.6 Kbps (US Robotics modem). The 56 Kbps
modem looks very attractive to a typical Internet user whose download
traffic is far more than upload traffic. Users can enjoy speeds close to
one ISDN B -Channel. This asynchronous transmission is however not well
suited for applications like video conferencing and large data uploads.
Another drawback is that it can only connect to digital modems, this
eliminates standard modem-to-modem transfer between home and office.
You have heard enough about cable TVs and
number of channels they provide. Now let' s talk about cat>le modems.
A cable modem is a device that sits between a PC (or other terminal) and
a cable TV network, and allows the PC to send and receive data. Isn't
that great? Imagine yourself accessing Internet while your folks are
enjoying Zee TV. Cable Modems do exactly the same job as analog modems
but at a much faster rate. This is because cable TV company uses coaxial
cable rather than twisted pair used by phone company, and can carry more
information, more quickly. Cable modems and hybrid fiber optic/coaxial
lines can transfer data at speeds of upto 30 Mbps downstream and upto 10
Mbps upstream, far surpassing the capabilities of ISDN, that also at a
fraction of the cost of ISDN. Another advantage is that they are always
online, no hassle of dialing the service provider.
Cable modem solutions are aimed at
both residential and business use with focus on Internet access. But it
can also be used to provide more sophisticated real-time services,
particularly for business community.
Like any other technology, the cable
modem also has its own drawbacks. The cable modem system effectively
turns the cable TV system into a very large LAN, which means users have
to share the available bandwidth with airy other active users on the
same node, resulting in a reduction in data throughput as the number of
users increases. Also the cable modem network is believed to be
insecure, because anyone with access to the cable network can tap the
Despite the obvious potential in
cable modems, the cable companies have a long way to go. The most
important factor is the huge investment required to upgrade the
infrastructure for data communications. Cable modems can succeed in the
market place only if the issues of standardization, security and
bandwidth guarantees are resolved.
Digital Subscriber Line (DSL) technology is
one of the latest additions in communication technologies making a big
impact in the industry. It is expected to have a dramatic societal
impact on both our personal and professional lives. Stated simply, DSL
provides high-speed multimedia services, such as video-on-demand,
super-fast Internet access, distance learning and video phoning to
anyone with a standard, copper telephone line.
Compared to other currently available
technologies, DSL modems offer the highest transmission reliability, the
fastest speeds and interactive capabilities, for the least investment.
DSL modems available today can download die entire Encyclopedia
Britannica in 31 minutes compared to 27 hours with a common 28,800 Bps
Among various DSL technologies, ADSL
has become a favorite buzz word among the communication technologist.
ADSL stands for Asymmetric Digital Subscriber line. With ADSL,
interactive Multimedia services can be provided to almost anyone with a
telephone line in their home or business. From a subscriber's
perspective, ADSL is completely transparent. It is a modem like
technology, in that it is placed at either end of a telephone line. ADSL
interfaces between digital sources containing information and provides a
channel of communication very much like a typical analog modem. The
primary difference however, is speed. ADSL is capable of throughputs
from 1.544 Mbps to 8 Mbps over standard telecommunication loops.
It does not, however look very
promising if compared with cable modems in terms of the raw data
transmission rate only. The major advantage of ADSL over cable modem is
that it uses standard telephone lines so new investment in
infrastructure is not required. AI)SL can also use a leased line, rather
than a switched one, which allows subscribers to have point-to-point
connection and hence better data security ADSL can also be an attractive
alternative to ISDN because the lines are specifically configured for
each connection and the connection is constant, rather than dependent on
the Public Switched Telephone network (PSTN) which is need by
traditional and ISDN and was designed for regular voice traffic .
Due to its feature and price, ADSL is
one of the most waited technology in networking area.
Wireless cable is a new technique for two-way
transmission of high speed digital data using microwave links to homes
and office. Wireless cable involves Multichannel Multipoint Distribution
Services (MMDS) which is expected to provide 10Mbps downstream
transmission rate for Internet access and telephone services in a way
not possible with present phone line moderns and at the same time can be
used for transmission of digital TV movies.
Since the system is wireless, this
system can be installed at only the cost of the equipment required for
those actually subscribing, rather than the cost of equipment I for
thousands of homes that must be passed by cable but are not yet
Wireless cable technology has great
potential for mobile communications. But, because of technological
complexity and high cost, it is likely to target the corporate segments
only. It is relatively new and has not caused much stir in the industry
Ethernet is the most popular LAN technology with very
large installed base. Most of the current Ethernet LAN use 10 Mbps
transfer rate, which is clogged by new graphic and multimedia
applications. Next generation of Ethernet, that is 100 Mbps Ethernet was
introduced in January 1995, which is steadily taking the market by
storm. The migration is made simple by LAFJ interface cards with dual
speed (10/100 Mbps) capability. If 100 Mbps network cards are used at
desktop then users will naturally seek more power at the backbone. This
is where the newborn Gigabit Ethernet takes its place.
Though Gigabit Ethernet is
relatively new technology industry is buzzing with it. Many vendors
already have products for it based on their own standard, this might
lead to incompatibility problem if they are not based on standard
specifications. Currently the IEEE 802.3 Ethernet task force is working
to develop standards that will allow 1000 Mbps connections between 100
Base Trousers and switches. Once the standards are set and
incompatibility issues are resolved, Gigabit Ethernet should go long
ATM has been one of the most talked about
technology in the communication industry for the last few years, but it
gathered much momentum in terms of actual deployment. This is mainly due
to its high cost and- constantly changing standards.
ATM is a cell-switching technology
which combines the high-speed efficiency of packet switching used in
data networks and the bandwidth reliability of circuit switching, which
is commonly used in voice
networks. ATM is extremely fast and scaleable, operating upto 2 Gbps.
Other feature advantages include high interpretability between desktop,
LAN, and WAN, as well as the ability to multiplex several data types
simultaneously across a single network.
Though ATM can bring extreme
capabilities to the LAN, at this point the technology seems most suited
for WANsmainly due to its high cost. Migrating from existing 10 Mbps
network to ATM will be many more times costlier than migrating to 100
Mbps network. However, at the WAN level it is competitive with other
existing technology such as Time Division Multiplexing. Because of its
ability to convert other data types into fixed 53-byte cells it uses,
ATM also can incorporate existing services such as Frame Relay, X.25,
and Internet traffic.
Currently ATM is taken as panacea by
the industry and developers are trying to use it with' everything that
exists today: IPXI IF, Apple Talk, and any other protocol. But in future
ATM will be mostly used in voice and video-conferencing areas.
to Look for Ahead?
It must be accented that one data transmission
technology will never solve the bandwidth problem. If network traffic is
not the bottleneck then servers, switches or even software can become
bottleneck. A high speed data communication technology will only be
useful if other network components can pump the data at the same or
higher speed. Obviously if data communication becomes faster, it will
give a drive to other network component vendors to match their products
with the transfer rate available.