gar187erI do this for a living
|reply to tt0180 |
Re: Zoom 5341G (4x4) vs Zoom 5341J (8x4)
real snr/MER/BER? you mean measuresd by a calibrated SLM? yea thats what it is.....your moed is calibrated to read it....its too busy doing other things.....hell modems can show bad snr yet the channel is perfectly fine.....
whats perceived should matter at all....what the actual modulation error ratio should....
also measuring the rf from the noise floor has NOTHING to do with codewords....codewords are the actual data in the modulated CW...doesnt matter is your SNR is 32, or 39.....yes under 32 you have issues, but your codewords SHOULD not change inside of the range under the same conditions....if they do, something else is goin on....
and yes thats a good overview of TDMA...and waiting 1/10th of a second isnt that much of a deviation.....its just inherent in the docsis system....people should knwo if they want steady ping/low jitter, go to dsl
I'm better than you!
Well, I suppose what I am trying to say is this.
Lets say that I have horrible hearing and that my friend Jake has immaculate hearing. (You could even say that I have average hearing and that my friend has superhuman hearing. The point that I am trying to make is that not all Receivers perceive the world in the same way.)
Anyhow, lets move forward with my hearing is bad (I have this constant ringing at times) but I have no problem making out a conversation in a room with a few other people talking.
When it turns into a party however, I cannot make out a thing.
So, you have the real noise floor and then you have the perceived noise floor which is created by the less than perfect receiver.
When it comes to QAM, the modem needs to accurately measure voltages (amplitude) at very specific points in the carrier wave.
Yes, for the most part, once you are above a certain threshold you are good. The precision of the channel tuner will be one of the main factors when it comes to SNR.
Having a higher SNR will help you out when the noise floor jumps due to random outside interference.
Again, however, I do not have a lot of experience with the commercial cable end of things. All of my experience is in SATCOM and general commo.