Dear Mr. Sharma,
First of all thanks for writing about (me) and my this thread with such a high regard.
However, I am of the feeling, that although there are serious participants here on the list, somehow their views are muted (they even choose to not say anything, at the thought of being ridiculed) because of flaunting of scanty knwoledge by a a select few (especially students from a reputed institute).
Such lists are meant for healthy discussions, where people share their views and ideas and substantiate the fact based on current happenings in the field of learning and knowledge. In this case LINUX in particular and information systems in general.
Both my threads on Broadband and Wireless (although OT) in general are aimed at encouraging all list users to read more and find more about these two fields in particular as these are the areas which will be one of the few key drivers of rapid employment and growth in the country.
Very often in socities and places where deep thought and hard work is not a part of the culture, such lists are overtaken by a select few aimed at unhealthy show off of their knowledge. These same individuals find such discussions berate "Andrew Tannenbaum" based on their reading of his old editions (without willing to pay and buy new editions of his books), without even understanding what we are talking about, they never know what is the cost of bandwidth as some institutes pay for their bandwidth usage where downloading of music (piracy) is rampant and misuse of subsidised (by tax paying citizens like us) educational bandwidth is very high, they get a degree and move on to a well paid job where the corporate pays for their bandwidth extravaganza. These students of today ultimately never become responsible citizens of tomorrow, if they are not checked and questioned in time about their accountability to society as students itself.
So far some people (irrespective of their learning and degrees in life) have attempted to apply their intelligence and answer the queries, however the students of the reputed institute, never botherd to contribute intelligently to this small and open society, clearly shows their responsible nature and their urge to learn. I am a strong advocate of NOT SUBSIDIZING higher education at all.
I will try to continue the threads, however I strongly believe these threads will come to an undesired and unsatisfactory end as long as others (presently mute and shy) do not come forward to offer their views (however silly they might be), I consider the silliest of the views offered forces one to think more deeply to provide more clarity in the replies.
with Regards, ASHWIN
----- Original Message ----- From: "peekay" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Thursday, February 24, 2005 9:12 AM
Subject: [ilug-cal] BroadBand tech specs for connection speeds .. Mbps for broadcast mode of cale tv channels (?) .. understanding the basics and IMPROVING/INNOVATING/IMPLEMENTING by ilug-cal
warning :
this is a very cut n dry issue .. not juicy or sensational .. so DON'T go thru this .. delete it and forget it
UNLESS
you are really really interested in this initiative .. its an excellent initiative by ashwin .. and i wish him all the best for a successful 'implementation' after the theory is elaborated, discussed, understood AND trials done
it CAN be implemented easily .. therefore it MUST ..
to be or not to be a part of this inititaive is a choice ..
read or delete .. as you wish .. but please don't spoil it
tks
..pi I
From: "Ashwin Mansinghka" <[EMAIL PROTECTED]>> > 1. cable tv is still co-axial .. not digital
Co-axial is just a cable type......Cable does not determine if it is digital or analog.
right ! .. its the signal passed over the medium .. adding : as of now, cable tv operators haven't gone 'digital' since the signals don't come in 0's and 1's .. like in hdtv signals
If> > 2. there is no digital speed on the co-axial for tv
Well there is, which is nearly 30 to 40 Mbps in shared mode, per channel.we combine more channels more speed.
i guess what this means is that rpg, siticable, etc use fibre optic cables
to
transmit tv data AFTER digitising it .. and that needs 30/40Mbps .. from
what
i see in my area's CVO's place, there is a h/w which converts the optic feed
into signals which are then sent over the coax cable as a non-digital feed.
i am SURE that my tv's tuner is NOT digital but just a tuner .. aka the radio tuner
i recall nn banerjee (gm, development, bsnl, assam now) telling me that to
send
video over a medium, a 4.5 to 5 Mbps capacity is sufficient .. strangely the
bandwidth
needs are miniscule to what fibre optic can carry !
> > 3. the analogue signal is the carrier
The signal carrier is RF
hmm .. so not 0's and 1's .. this would naturally mean issues like freq. modulation and amplitude modulation would be the issues.. as different from 'bit' manipulation
flowing along ("not through" the medium, like in case of electronic signal)
oops .. gaps in my understanding .. 'along' and 'through' ? .. i always understood that the mild milli/pico-watt currents gave RF type waves .. and that electrons were the particles that did this .. NOT by 'flowing' .. BUT by making electrons of adjoining atoms of copper shift to adjoining atoms of copper .. but i would really like to know the reality (it's now 35 years since i stood 19th in HigherSecondary from science :-( so things are better understood now, perhaps)
the co-axial cable which acts as the RF feeder.
would this mean that the wave propogation (radio freq) through/along the medium does the work of transferring the 'signal' ?
Therefore, we measure the signal in dB i.e. SNR - Signal to Noise Ratio.Thesignal type is analog definitely as long as it is on the co-axial cable.
hmm .. so it is not in 0's and 1's .. it is non-digital .. an addition here .. 'signal' or 'freq' by freq/amlitude modulation/demodulation does not compulsorily mean that it has to be electron based .. it can be thru short waves/medium waves/microwaves ('disturbances in the radio freq spectrum' which one tunes into) .. and can also be thru photons .. as in laser based optic fibres .. or even sound based .. like in the earlier 'modems' on which the telephone hand set had to be placed .. SNR would apply to all these scenarios.
> > 4. there are 99+ channels on ONE co-axial
Well yes, there are all those channels on ONE feeder.
and many frequencies .. for the many 'channels' .. and all in non-digital
mode too ..
DTH works on similar basis .. only that the medium is radio freq signal
direct
from the satellite in the sky to the dish antenna at consumer's premises ..
similar
to V-Sat dish antennas .. ONE feeder .. many many channels
frequencies> 5. frequencies of the channels are different
Very true, each channel occupies 6 Mhz bandwidth with the centerranging from 50 Mhz to 864 Mhz.
there .. so its not 4.5 or 5 Mbps .. but 6Mbps .. we do know that the
'hertz' in
the MegaHertz means cycles .. and i guess we also know that with the
enormous
progress in h/w .. each cycle CAN be made to carry more than a single bit ..
by
cutting up the + and - parts of the cycle into yet further segments (prior
half of +
part of the cycle to represent a bit and the latter half of a + part of the
cyle to
represent yet another bit)
Local cable tv provider can certify this for you.
oops .. these guys don't know how things work .. ketan may .. he is helping
on cable operator to give broadband (read shared rj45 wan) from beck bagan
to golf green as of now .. but even ketan can't authoritatively tell ..
for authoritative measurements, our list's geniuses are capable .. so is
tapan sengupta who joined us at the last meeting .. he even has the h/w and
s/w
to do such measurments .. and he did talk to me about signal types/levels
yesterday too
.. we are trying to put in a wi-fi wan .. hot spots .. in udita .. with
bsnl's broadband
connection being used by nodes to access internet (legal issues ARE
involved) .. at
the ilug-cal's recent meeting location : UDITA
PAL> > 6. a 'tuner' is used to get the channel of one's choice
Very true again.
> > 7. there is audio AND 'video' data
There is no data in strict sense as long as it is ANALOG that is regulartype TV signals. When the contents of a given channel are MODULATED at thecarries
HeadEnd i.e at Cable providers premises, then the particular channelDIGITAL DATA and is obtained at the customer's premises upon DEMODULATION,
this is simple to understand .. i believe the Mod/DeMod is tuning into the channel .. there are other things involved as well .. Mux-ing/DeMux-ing and also the Compression/DeCompression (digital only ?)
yes we are talking of Cable Modem.
.. ah ! .. music to our ears .. when ? how ? .. go on .. any installations up and running commercially yet ?
as of now, the cable tv operators are offering WAN thru RJ45 .. the CableModems are too costly to buy/install and the provider end equipment and s/w are costly too
we have been talking to RPG and others and they just seem to be blissfully ignorant of such things
breifly .. this would need a splitter .. at our end .. which sends the tv signals to the tv and the digital signals to the pc .. this CableModem is different from the DSL .. err .. ADSL based broadband implementations of bsnl .. then how in the world will bsnl provide video-on-demand thru THEIR broadband ? .. 'digital' video specifically
> > 8. pic res is 352 x 288 pixels (ugh !)
That is regular TV, not digital data. 30 Mbps can carry a lot.
are we talking about hdtv here .. or digital/digitised high-res but 'regular' tv channel signals ?
TV> 9. tv delivers (so do webcams, even digital ones .. where the pic IS > digitally recorded and can be played back in DVD format too)
Well we are not talking about TV anymore, when we want Internet on Cablenetwork we talk about digital data packets inside the shell of analog signal, quite like our regular DIAL-UP modem.
OK .. so we come to the main, core issue .. and let's work on this
> 10. non-digital in NOT analogue .. its just non-digital .. likenegatives> of > photos, older audio casettes/wax/vinyl records, video .. err .. movie > films, > video casettes, etc .. even human sound is not 'analogue' .. > electronically > that is ! .. it just NOT digital
Well this is again true. But we should remember about MOULATION-DEMODULATION.
and muxing and compression too ?
Now, I want some one to talk about possible Modulation methods (standards)
and Encoding methods (standards) which can provide us this data rate.
Just to provide a clue, we are talking about QAM and MPEG together.
Maybe one of our very learned friends here from a reputed institute will tell us about Error Correction applied in this case ;)
yep .. this will be a great help and a very fruitful discussion !
all geniuses, please contribute and let's work together .. but NOT against each other .. the issue needs to be addressed .. the level of knowledge of the participants in this discussion is NOT to be targetted please ! inputs are going to help .. criticism, comments, shooting-down won't help !
Finally, are we dreaming ?
NO, you can take my word for the same.
quoting from a recent email : those who dream with eyes open .. have the power to make their dreams happen too !
no, we are NOT dreaming ! we are working, discussing, co-operating, collaborating, IMPLEMENTING and wanting to be the early birds !
good luck .. and thank you for this very relevant tech topic co-ordinating ashwin !
..pi I
with Regards, ASHWIN
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