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November 24, 1997


N Vittal

R, R & R

Building a communications system? Better get your three
'R's right. Reliability, Ruggedness and Redundancy.

India successfully launched the IRS 1D satellite on board its Polar Satellite Launch Vehicle last September. But in the same week, the INSAT 2D satellite suddenly failed. That was Murphy's Law at work. If something can go wrong, it will, and at the most embarrassing moment.

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Satellite communication is becoming increasingly critical to our communication systems. Our television depends on it. A significant part of our telephone network depends on it. The National Stock Exchange depends on the 'very small aperture terminal' network linked to INSAT 2D. The failure of INSAT 2D upset the business on the National Stock Exchange for a week!

In short, our economy is becoming increasingly dependent on our communication systems. And to keep these systems up and running efficiently, despite Murphy's Law, we will need some strategic planning in designing our communication systems.

'Strategy' is very popular with the management types. It means that decisions must involve an investment of high order and, more importantly, must consider the long-term impact. Decisions regarding our communication systems have to be strategic.

And any communication systems design strategy cannot do without the three essential 'R's -- Reliability, Ruggedness and Redundancy.

A communication system, which is not reliable, is like a friend who is not helpful in the hour of need. Reliability derives from the two other 'R's -- redundancy and ruggedness.

Redundancy has a negative connotation because it is generally perceived to be wasteful. But in the design of critical systems like a communication system, it becomes a necessity. To ensure against failure we must have alternatives to fall back on. This will make the system fail-proof.

Ruggedness is called for because reliability requires communication systems to survive breakdown pressures like those of incorrect handling and hostile weather conditions.

Satellite communication is very glamorous, but has bandwidth limitation, the capacity to carry digital data in digital form.

According to Professor Viswanathan of the National Scientific Documentation Centre, "There are about 100 communication satellites in the sky and by 2000 there will be about 500. The aggregate bandwidth of all these satellites would then be about a hundredth of the bandwidth that can be offered by a single optic fibre cable!"

It is therefore obvious that we must have a system, which makes the best use of the high bandwidth of the optic fibre and the optimum use of satellite systems. The strategy will have to roll both, optic fibre and satellite communication, into a single system.

Our attitude should be that of the lawyer whose mother-in-law died. The funeral parlor offered him three choices: "Do you want your mother-in-law to be buried, cremated or embalmed?" Not to leave anything to chance, the lawyer had a strategy. "Do all the three. Don't take any chances!" he warned. Communication systems too cannot be left to chance.

Concentrating on satellite communication, the key issue is the effective use of the limited radio frequency spectrum, which is used to relay data back and forth.

In such wireless communication there are two broad technologies available. One is the analog system and the other is digital.

The digital system, which is more recent than the analog one, has certain advantages like better voice quality and, more importantly, tremendously more flexibility of use because digitised communication can be compressed. Digital compression allows the same radio frequency to carry significantly more content, helping conserve the limited bandwidth available.

The first element in our strategy should be to improve the productivity of our systems by going digital. Satellites carry devices called transponders to communicate with each other and Earth stations. In our satellite systems we have 63 transponders, even after the loss of the transponders in INSAT-2D satellite. Between the Department of Telecommunications and the ministry of information and broadcasting, nearly 52 transponders are used up.

INSAT is being used to provide inter-main, main-primary, remote and rural-area trunk communications by DoT. A large number of closed user-group networks, including government agencies, also operate in the INSAT system through their own dedicated ground segments.

Over 10 private service operators provide closed user-group VSAT networks through shared hub facilities.

Most of these networks operate in the digital mode. Some of these are the 'intermediate data rate' (IDR) carriers, 'multi-channel-per-carrier' (MCPC), VSATs, closed user-networks, private operator VSAT networks, NICNET, RABMN and ERNET.

Over the past decade, with the increasing establishment of digital exchanges, DoT has also started introducing digital transmissions in the INSAT network.

The analogue systems in the DoT network are limited to some of the inter-main routes and main-primary routes operating in the FM/SCPC mode. These analogue networks operate over only six transponders of the over 30 deployed in the telecom network.

These routes operate in analogue mode to avail of the already existing and working equipment. In the long term, these networks will be progressively converted to digital technology.

The television component of the INSAT system uses analogue techniques. There are 18 national and regional language channels in the Doordarshan network. Additionally, there are three educational and development communication channels operating in the INSAT system.

These services were introduced in the eighties and early nineties and operate in the analogue mode as compressed digital technology for broadcast television was not available then.

These services are not only received and rebroadcast by Doordarshan transmitters, but also are also received by a large number of cable operators. Doordarshan is aware of the trends in compressed digital television via satellite. The technology can reduce the space segment requirements by four times!

However, like in other parts of the world, introduction of digital techniques will be gradually phased out so as to not affect the existing analogue services for which a large investment, on ground, has already been made by Doordarshan and private companies. It is estimated that there are over a quarter million dish antennas in India today.

Again, there are two types of compressed digital television transmission over satellite.

One is the single-channel-per-carrier (SCPC), scheme. It allows television uplinks from different locations, a requirement of the Doordarshan network. Even today the digital satellite receiver (integrated receiver decode, or IRD) for the SCPC scheme costs about Rs 100,000 compared to less than Rs 5,000 for an analogue satellite television receiver.

The second scheme is the multi-channel-per-carrier (MCPC) system in which multiple television channels are multipexed and uplinked on a single carrier from one location.

For programmes originating from different locations, back-haul links would be required to bring them to the MCPC uplink location. This requires additional satellite resources. The cost of a digital satellite television receiver, like IRD, is about $ 600 for MCPC digital systems. The present MCPC digital television systems are proprietary in nature and the entire system of encoders, multiplexers and receivers have to be bought from a single vendor.

Even though MPEG-2-DVB standard is generally accepted for digital television compression, there are gray areas in the implementation of the standard, resulting in different proprietary systems in the market.

It is understood that Doordarshan is studying the options and evolving standards for implementing compressed digital television in their system.

The mess needs to be sorted out on a war footing. We must immediately launch a mission to campaign for completely switching over to digital systems.

One frequency channel of an analogue system can be used as three separate channels under a digital system! Hence going digital would mean squeezing out enormously more traffic out of our existing transponder capacity. The analogue to digital migration must take place as soon as possible.

While we may build more satellite systems and launch them quickly, making optimum use of the transponders already available makes eminent sense. Incidentally, it will also bring more revenue to the government, besides conserving the precious and limited radio bandwidth, an important natural resource.

The second element of our strategy should be to build redundancy. Even those, like the NSE, who are dependent on satellite systems, must be given the option of using leased telecom lines. This will let them switch to the leased lines and carry on business as usual even in the event of a major satellite failure.

I understand that by some peculiar logic, DoT does not permit VSAT operators to hire leased lines. At least the INSAT 2D experience should make us undertake a quick policy revision and build redundancy into critical systems like stock exchanges.

That brings me to the third element in our communication systems strategy -- optic fibre.

DoT has its own optic fibre system, running over 50,000 kilometres. The railways have about 10,000 kilometres of optic fibre and a potential to grow phenomenally along their rail tracks which runs over 63,000 kilometres of hinterland.

In addition, is the network of electricity boards, which crisscross the nation. The power grid also has come up with optic fibre networks. It is a healthy development that the new Internet policy has allowed the railways and the power grid people to participate in the building of the 'National Information Infrastructure'.

Private parties must be encouraged to build optic fibre systems using the infrastructure of the railways and electricity boards. Transparent conditions must be laid down for the laying of optic fibers on a 'build-operate-lease' basis or a 'build-operate-transfer' basis.

If tenders become unavoidable, learning from experience in basic voice telephony, clear transparent conditions should be laid down and quick decisions must be taken.

An alternative strategy could be the setting up of a negotiating committee of people with impeccable reputation as has been done in the power sector. This will help in expediting decisions and encouraging investment in the sector.

Before starting the exercise, it will be to be worthwhile to ask potential investors about the proposed business conditions and what would make the investment attractive to them and then redesign policies to meet their requirements.

We must dream of and aspire to wire the whole nation with a fibre optic network in the next five years.

This, along with an intelligent strategy for going digital, as far as telecommunication and broadcasting are concerned, will ensure sufficient resilience to overcome setbacks in the communications system like the premature death of a satellite.

Previous columns: Critical mass | T.R.a.I | Santa Clause 11(2) | The Broadcasting Bill | The death of distance | S.O.S, getting the message out of the bottle | Force 7 from FICCI | Of railroads and info highways | Techno Politics | Cheating death: Ways to resurrect ITI | The HAM-handed miracle | Electronic governance | Which came first? | The four-engine design | Learning to learn | Heads 'n hands | Post-mortem | Where's the cash | Mr T S Eliot's digital wisdom | Banking on IT

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