On Thursday 09 September 2004 23:38, Rony Bill wrote:
Hello All,
Modulation is used to transport a signal on a carrier. In the earlier days frequencies were low and for sat. transmission they had to be mounted on a carrier. But today the freq. that is used for communication is so high that it is a carrier in itself. Eg. a gigabit LAN passes data in gbytes per second.
The moment you switch some component of a (phase, amplitude, frequency) signal you get side bands which depends on the amount of shift of the components. The center freq is the carrier and the info in the side bands. The info size is fixed by natural principles and named after a gent called Nyquist several decades ago. Now this carrier and side band has to be transported from point a to b thru some physical medium like Cu cable, fibre, or space. The ability of the medium to allow the signal+sideband to pass without distortion determines the final throughput. Incase of satellites, it is atmospheric characteristics, solar flares, antenna size, available power, etc that determines the data throughput. In general the higher the signal bandwidth, the higher the SNR required to extract info. Hence more complex and expensive electronics.
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.
Can we have a satt. carrier signal that is a fixed frequency but is made up of a constant data train?
You can. Infact all known wireless data transmissions use exactly this method.
As of now, what is the highest download speed achieved by satt. internet? What is the highest speed currently available in the satt. 'pipes' that big corporates use for international inter-office links ?
Afaik 384MBPS with a 6mtr dish. point to point.That is data from private networks. Dont know if anyone is interested in sending mundane webpages using this extremely expensive channel.
Anyway, this is the technical part which will be looked after by satt. designers and other techies.
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.
DAB on FM is already here. 250Kbps. Just get rid of the sattellite and things become practical. And adhoc wifi networks are even better when coupled with peer-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.
Many have mistaken this for another television broadcast. It will be similar but not the same. TV is only live entertainment. This is a normal serious ultra high speed file download system for the common man at
HEHE. all the computers and nerds are working hard on the serious stuff so that everbody can have free time for entertainment. At least for me computers are serious entertainment.
a very low monthly rental, for an *infinite number of users* within the footprint. That is the whole issue. How good and usefull is this idea?
If the Govt. opens up the airwaves to private net operators then the entire 58 (60 - existing 2) terrestrial TV channel spectrum could be utilised for digital serial file broadcasting in a similar
Teletext. Another flop. Currently used in Britian (Afaik). 120bps.
way but at a lower download speed than a satt.. Major companies like Red Hat, Novel, Microsoft and many many others can provide their heavy software files on the airwaves to be downloaded in our homes and offices in a fast and economical way. No wiring, no cable.
Carrier pigeon would be better. The bit error rates at BW more than a few 100 kbps over even short distance of 2 kms is so high that it would take forever to download one iso. And cable internet is what (supposed to) works better.