Saturday, January 04, 2014

Cellular Technology cannot help Disaster Victims Outside a Cell Phone Tower’s Reach

It is amazing that a terrorist can buy a satellite phone. He can even rent it in certain countries. I understand that a week’s rental is about a thousand US dollars. However, a peaceful citizen caught in an accident can die because he or she cannot call for help. A fisherman caught in hurricane's aftermath can drift for days on the high seas without being able to seek help. A village facing a disaster can suffer for a week because its communication channels are cut. Such a problem did occur last year when floods hit Himachal Pradesh. 

I would like engineering students to ask themselves this technical question: Can we find out a way to ensure that affordable cell phones can send an SMS to some disaster management agency from anywhere in India?  Of course this may require addition of some hardware and software to the cell phone itself. It may require legal and operational safeguards to ensure that some idiot does not send an SMS as a practical joke, making people run around for nothing. At the moment let us just focus on technology. The practical problems mentioned can be solved.

A satellite which can pick up a weak signal and deliver it in a readable form to a ground station could be part of the solution. Telecom guys ought to ask what it takes to receive a 160 Byte signal from a handheld battery operated device and send it down. The principle of complexity inversion says that it may be cost effective to put the sophistication into the satellite or into the ground station rather than into millions of cell phones. The trick is to be able add no more than a couple of thousand rupees to the cost of the cell phone itself, even if it means that we put millions of rupees worth of equipment into the satellite or into each ground station.

I don’t think we ought to limit ourselves to 1 or 1.5 W transmissions from a cell phone. We could use well known techniques to use only a cell phone battery and still spend 10 W for 100 milliseconds. The signal does not have to be sent once only; we can have the phone repeat it a hundred times in a day.  
You can be sure that the “authorities” would not want you to escape their surveillance. No problem, they can tap the ground station for all they want.

Cell phone operators will want their pound of flesh. No problem – we can let them set up the ground stations and charge us a hundred times the standard rate for delivering an emergency SMS.

Are there solutions that do not involve satellites? Is there some part of the wireless spectrum in which a MHz channel be set apart for some form of transmission that will travel hundred kilometers well enough? Short wave? VHF with meteor trail reflection? Artificial ion trails created by simple rockets being fired periodically, say every hour on the hour?

Does the radiation of an emergency signal from a cell phone have to be omni-directional? Can’t we have some indication from the cell phone as to where we should point it so that a signal being sent out in a cone of (say) 60 degrees beam-width has a chance hitting the receiver or the relevant reflecting surface? If there is an ion trail involved, can the cell phone get a signal through it to create an audible alert?   

I am sure that we are smart enough to create a system that a human cry for help can be made to reach us, irrespective of where it originates! It can also give us the location code to tell us its origin. It is the job of engineers to find out how to do all this!

Srinivasan Ramani 

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