the higher the signal bandwidth, the higher the SNR required to extract info.
actually it is the other way around - you can trade off SNR for bandwidth and vice versa - Higher the bandwidth and you can go with very low SNR. The SNR of the signal from the Mars Rover is just slightly above white noise - so they use a terahertz bandwidth pipe for communication.
Someone told me, in China they use terabit LAN. Sat. freqs. are also in GHz. Nowadays digital formats in broadcasting have narrowed bandwidth utilisation yet provide high volume content. They are able to cut down on side bands.
terabit lan is actually commonplace in research labs all over the world - but they have yet to reach practical use because of the difficulty involved in the electronic switching at those data rates. Its not a limitation of the transmission channel. Imagine having to buffer about 10 seconds of data at those rates ? what would you write it to ?
cut down on side bands ? they can cut down on the time they need to broadcast each slice. in a typical sharing system, if you cut down the time slice of each broadcast, you will widen the frequency band required to transmit it. with digital broadcast, you can send a lot more information in the 4.7mhz channel space of a typical PAL broadcast channel, and thats the only real advantage - you need to approach shanon's limit for transmission channels, and so far digital broadcast is the best way to get there - even though it is a long way off from the ideal. Some ideas have also been proposed where authors think of using turbo codes for txmission,
What I want to know mainly is whether the concept of having such a ***high speed-high volume-repeatitive-serial file download facility*** is acceptable and worth implementing.
it has been implemented. check out moviebeam - its a relatively unsuccessful service based on the same idea. Recently tivo and netflix teamed up to offer similar service.
to-peer stuff like bittorrent. With newer modulation techniques like
UWB (1Gbps >bw and relatively "simple" recieving frontends) becoming commercially >viable "unlimited" bw for the masses is only an antenna away.
ultrawideband is actually severely limited by distance. UWB is actually the perfect example of trading off bandwidth for SNR. UWB uses a spectrum that is many Ghz wide (not 1Gbps as data rate is not bandwidth) and therefore can support an SNR almost at the level of the surrounding noise. One of the features that most uwb proponents talk about (incorrectly) is the anonymity that this low SNR guarantees. UWB is therefore a very good replacement for the 802.11g that is used to solve in-home connectivity issues - but is hardly something that can be used for public broadcast. data rates are then defined according to shanon limit on how much information you can send in this slice of the spectrum.
As a general comment - with the population density in India, and the amount of fiber put in the ground by reliance, wouldnt fiber based services be the way to go ? nothing can ever beat the data rate capability of fiber. Fiber can support a spectrum width of about 30Thz and that is only a limit imposed by the switching speed of the laser, and not the fiber. In any case, even with 30 thz, you can theoretically transmit all of mumbai's internet, cable and telephone traffic through a single fiber pair, provided it is fully utilized. so if youve laid fiber all over the city, the last mile problem is the only thing youve got to address with video delivery networks. satellites are really overkill for anything today.