HOW TO SET UP…

The

ability to connect remote areas spread over dispersed

geographical locations and inaccessible through terrestrial

infrastructure makes VSAT a natural option for communications.

Other considerations are of reliability and speed of data

access. A 99.5 plus percent uptime standard ensures that VSATs

support mission-critical applications such as ERP, online

billing applications, etc. Talking of speed, it delivers data at

up to 30 Mbps–that is 1,000 times faster than that provided

via ordinary 28.8 Kbps modem over phone lines. (For other

comparisons with leased-lines see Table 1.)

The Indian VSAT industry

presently might be worth less than Rs 500 crore, but it provides

vital communication links to companies whose combined turnover

exceeds a whopping Rs 50,000 crore! Worldwide there are 3,22,000

users of VSAT services and they include names like Wal-Mart,

General Motors, Ford, Coke, Cadbury, Pepsi, etc. to name a few.

Checkpoint#1

VSAT

networks outweigh the leased-line option on many accounts.

Checkpoint 1 gives some

idea about the advantages of VSATs over leased-lines. Other

benefits are enumerated below.

Company-wide access to information



It empowers the company employees by giving them a wide canvas
of data based on which they can take informed decisions.

Better integration of a company''''s

operations



Branch locations in remote corners are enveloped easily under a
satellite footprint. Hence, greater co-ordination and tighter

integration of business



processes is possible.

Lower communications costs



VSAT networks help save significant amounts on
telecommunications as well as travel costs. The ability of VSATs

to support videoconferencing and to act as a leased-line in the

sky has been a significant driver for increased use of this

technology.

Support for mission-critical applications



High reliability of these networks ensures that mission-critical
applications like ERP, billing & finance (customer care),

and data broadcast are effectively deployed. Setting up a

VSAT Network

VSAT

networks are of two types–Dedicated Hub Networks or Shared

Hubs. In a Dedicated Hub scenario, the hub infrastructure is

utilized by a single corporate entity with all the VSATs in the

network sharing the dedicated resources available. Purchase of

such hub is warranted only when the number of sites is huge and

the application is specific to the corporate. Typical users of

such hubs are banks, stock exchanges, etc. In a Shared Hub

scenario, different users share the hub infrastructure.

A VSAT system consists of

a satellite transponder, central hub or a master earth station,

and remote VSATs. The VSAT terminal has the capability to

receive as well as transmit signals via the satellite to other

VSATs in the network. Depending on the access technology used,

the signals are either sent via satellite to a central hub, or

directly to VSATs with the hub being used for monitoring and

control.

The VSAT comprises two

modules–an outdoor and an indoor unit. The outdoor unit

consists of an antenna and Radio Frequency Transceiver (RFT).

The antenna size is typically 1.8 metre or 2.4 metre in diameter

although smaller antennae are also in use. The indoor unit

functions as a modem and also interfaces with the end-user

equipment like standalone PCs, LANs, telephones or an EPABX.

The two basic access

technology alternatives are Time Designed Multiple Access (TDMA)

or Pre-Assigned Multiple Access/Demand Assigned Multiple Access

(PAMA/DAMA).

TDMA: In this

network, all remote VSATs communicate with the service provider''''s

central hub station. The hub station monitors and controls all

the VSATs in the network and all the customer traffic is routed

through it.

PAMA/DAMA: Implies

that the VSATs are pre-allocated a designated frequency.

Equivalent of the terrestrial leased-line solutions, PAMA

solutions use the satellite resources constantly. Consequently,

there is no call-up delay, which makes them most suited for

interactive data applications or high-traffic volumes. As such

PAMA connects high-data traffic sites within an organization.

Single Channel Per Carrier (SCPC) refers to the usage of a

single satellite carrier for carrying a single channel of user

traffic. The frequency is allocated on a pre-assigned basis in

case of "SCPC VSATs". This term is often used

interchangeably with PAMA VSAT. DAMA network uses a pool of

satellite channels, which are available for use by any station

in that network. On demand a pair of available channels are

assigned so that a call can be established. Once the call is

completed, the channels are returned to the pool for an

assignment to another call. Since the satellite resource is used

only in proportion to the active circuits and their holding

times, this is ideally suited for voice traffic and data traffic

in batch mode. DAMA offers point-to-point voice, fax, and data

requirements and supports videoconferencing. Hybrid

Services

Hybrid

VSAT services integrate TDMA and DAMA/PAMA access methods to

maximize benefits and minimize costs. They offer a customized

solution tailor-made just for your requirements.

Checkpoint#2

Compare the

technologies available

Before you go in for a

VSAT network, it is best to weigh different access technologies

available today. Table 2 compares these on certain parameters

essential for a VSAT network.

A typical corporate

requirement consists of a head office that hosts the application

server–a PAMA site–and remote TDMA VSATs which log-in to the

host site.

Checkpoint#3

Selecting the

service provider

Apart from decisions on

the appropriate technology, the selection of a VSAT service

provider is crucial as the services play a vital role in the

successful implementation and optimal utilization of your

network. Hence, these should form a vital part of the evaluation

criteria. Some of the aspects to be considered are:

• Programme management
  
  and installation capability

• Network and
  
  applications integration ability

• Process and
  
  infrastructure for delivering consistent services

• Service deliverable
  
  guarantees offered

• Ongoing service
  
  reports and review procedures

Detailed procedures, which

are outlined and adhered to, are crucial indicators of the

competence of a service provider. In an infrastructure project

such as a VSAT network, buyers cannot easily shift from one

service provider to another since the technology platform is

proprietary. Hence, one has to carefully evaluate the above

criterion when choosing a VSAT service provider. Checkpoint#4

Network design

While finalizing on the

network design aspects regarding VSAT topology, other networking

module requirements and network protocol usage, it is essential

to keep the bandwidth requirements in perspective. Some of the

factors which influence the required bandwidth are:

• Type of application

• Type of transaction
  
  (interactive/batch)

• No. of simultaneous
  
  users on the network

• Transaction size

• Response time expected

Once the order has been

placed on a VSAT service provider, site surveys are commissioned

where the various site locations are evaluated for feasibility

of installation. On installation of the equipment at the site,

the site is commissioned. The next step is systems integration

and applications integration. On completion of these stages, the

VSAT network is up and ready for use.