ENTERPRISE EQUIPMENT MODEMS: Ready for a Makeover

TECHNOLOGY OPTIONS



Dial-up Modems: Dial-up modems are now gasping for their last few breaths. Most
external modems have now been replaced by internal ones. In terms of specs, 56

kb speeds with V.92 technology and V.PCM enhancement remain the dial-up’s last

bastions. V.92 offers features like Internet call notification (ICN),

streamlined call handling and modem-on-hold. V.PCM Upstream reaches upstream

speeds up to 48 kbps and lets the user choose either the fastest downstream

speed (up to 53 kbps) or a ‘balanced’ connection of downstream and upstream

communication.

l DSL Modems: A DSL modem

facilitates simultaneous voice and data transmission over the same line. It does

this by splitting the regular copper telephone line into two frequency ranges.

The frequencies below 4 KHz are reserved for voice, and the range above that is

used for data. The splitter, consequently, allows simultaneous access to the

line by the telephone and the computer.

Since a large number of DSL protocols have been developed, they are

collectively referred to as xDSL, including HDSL, SDSL, ADSL, and VDSL. High-bit

rate DSL (HDSL) provides T1 or E1 connections over two or three twisted-pair

copper lines respectively. Unlike most other forms of DSL HDSL is not a typical

consumer service, it is used mostly to replace traditional T1/E1 connections,

such as connecting PBXs to telcos.

A Single-pair High-speed Digital Subscriber Line (SDSL) is similar to HDSL,

but provides T1 or E1 connections over a single twisted-pair copper line.

Assymetric DSL (ADSL) is a form of DSL in which the bandwidth available for

downstream connection is significantly larger than for upstream. Although

designed to minimize the effect of cross talk between the upstream and

downstream channels, this is suited for Web browsing and client-server

applications as well as some emerging applications such as video on demand.

Very-high bitrate DSL (VDSL) is similar to ADSL but provides higher speeds at

reduced lengths.

l Cable Modems: Cable

modems convert Internet data into a radio frequency (RF) signal that can be

transmitted over co-axial cable. Cable is a shared medium and so transmission

speeds will slow down as more users log on. Cable networks are inherently

hierarchical in nature and thus require two paths, one for downstream and one

for upstream. This requires either a second cable plant for upstream or a second

frequency band allocated onto the existing system. Cable modems separate digital

and analog traffic and enable a PC to send and receive data using the coaxial

cable sharing its downstream and upstream frequencies with the Cable TV

channels. A cable modem interacts with a CMTS installed at the location of the

cable operator. The CMTS in turn interfaces with the CATV frequency spectrum.

Cable modems use various technologies like the TDMA based DOCSIS standard or the

more robust and modern SCDMA-based Terayon proprietary technology.

l Ethernet-to-the-Home (ETTH):

This Ethernet-based technology may soon replace the need for modems. Like

standard Ethernet, the bandwidth is 10 Mbps for home users, but can reach 50

Mbps using symmetrical data connectivity as for enterprise customers. While this

technology is Ethernet-based, it has been designed to run over existing coaxial

networks with minimal changes to the existing infrastructure. The customer end

connection is a standard RJ45 ethernet socket/plug, which can be connected

straight to the customer’s PC without a modem or adaptor. Unlike DSL, ETTH can

run over a long distance using amplifiers.

l Leased-line Modems: Leased

line modems are analog and not digital. These special modems are used on lines

leased from the service provider or sometimes on just a long direct wire hookup.

They often will also work as ordinary modems, but go into leased-line mode when

the AT command and L1 is given. Leased-line modems often use a ‘dumb mode’

where they ignore AT commands, disable result reporting, etc. One type of leased

line used two pairs of wires (one for each direction) using V.29 modulation at

9600 baud. Some brands of leased-line modems are incompatible with other brands.

l ISDN Modems: The ISDN

modem connects the computer to a ISDN line. The transmission is purely digital.

l LAN Modems: The

concept of shared Internet access has resulted in LAN modems. These modems have

a built-in IP router, 4-port 10BASE-T hub and voice ports. In effect, this

device allows the user to instantly create a 10Mbps LAN for the SOHO, and share

a printer, modem or fax.

BUYING TIPS

MARKET INFORMATION

The number of Internet connections is expected to rise by at least 40

percent (year-on-year) for the next five years. This should provide the required

surge to the modem market. There are many technologies available in the market

including dial-up, DSL and ETTH. The leased-line modem segment is expected to do

well as a market segment till 2005, but most predict that it will be overtaken

by broadband which is expected to account for 50 percent of the market by 2005.

But the Indian broadband modem market, consisting of cable and xDSL modems,

is yet to mature. Cable modems, which usually have an Ethernet output, can

provide Internet access to multiple PCs. The only hitch is that computers should

be connected by a local area network (LAN). The Ethernet output will enable a

cable modem to connect to a LAN with a standard Ethernet hub or router. However,

many feel that cable modems will be phased out in the next two years. Internal

modems are expected to replace the external modems by 2004. Dial-up 56 kbps

modems will transition to ETTH and broadband, which will be on board by 2005.

In countries where broadband enters late, xDSL would have the edge. In India,

the fight would be between xDSL and ETTH, with both technologies getting decent

market shares, though as of now, ETTH has an edge. But in many opinions, ETTH is

a better technology, as it provides higher bandwidth and networking performance

at up to 100 Mbps, and can be used for mass deployment.