Even today, cellphone towers triangulate cellphones. In fact they can narrow down a cell phone to a couple of meters, they can track the movement of the cellphone in near-real time.
Why can't a software re-program convert all these towers into a radar network?
Cellphones communicate with the cellular network or can be tricked into communicating with the network. The "time of arrival" and "angle of arrival" data required for positioning a cellphone comes from transmissions from the cellphone itself - which are in the uplink band. The typical GSM cellular network base-station is FDD (frequency division duplex). So the base-station's transmissions in the downlink band are completely filtered out by the base-station's own uplink receivers. This prevents receiver-blocking where the base-station's receivers would be deafened by the base-station's own transmitters.
Enemy aircraft are not going to communicate with the cellular network in the uplink band. Reflections in other frequency bands from the aircraft are physically filtered out. A software upgrade will not suffice. Also note that even if the radio interface is reconfigured, the radio signals cannot be trunked to a centralised processor in analog or digital form because the bandwidth available will be grossly insufficient. Digital signal processing equipment will need to be moved to the "front end" of the network, i.e. every base-station, so that processed reflection information which would be low in bitrate can be transmitted digitally to a centralised processor. So now we need not only a software upgrade but also a radio hardware reconfig and smart/expensive processors at the front end of the network.
I suggest that people first understand what the principle as well as difference between:
My personal opinion, as someone who works with cellular networks for a living, is that it would be far cheaper and better to make an independent network. The system would be completely reconfigurable as needs evolve over time. I also believe such a system is well within current Indian capability.
The highlighted part is for sure "Satya vachan".
However I differ on the prior part. There is many practical ways to use Cellular network to realize Bistatic , Mutistatic and/or Passive radars (or a hybrid combination there of). In all cases one needs additional hardware in addition to Cellular network to realize it.
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It is passive radar that is easiest to realize. http://en.wikipedia.org/wiki/Passive_radar
BTW US embargoed a Balkan country (Czech) that makes passive radars and later co-opted the manufacturer for money to not export to any other country, to ensure no other second/third world country can bye/own it.
IIRC Chinese also have Passive radars.
Indian hands are tied because they think their hands are tied.http://en.wikipedia.org/wiki/VERA_passive_sensorhttp://en.wikipedia.org/wiki/Kolchuga_passive_sensorhttp://en.wikipedia.org/wiki/Tamara_passive_sensor
Open literature sources claim VERA-E systems have been exported to Estonia, Pakistan and the United States. Newspaper reports also claimed that in January 2004 the Czech defence sales company, Omnipol, received licence to sell six systems to China. However, US government pressure on the Czech government resulted in the cancellation of this contract. Civil systems have been widely exported throughout Europe.