How to select best possible modulation technique for a particular fixed bandwidth???

i need to discuss about to how to select best possible modulation technique for a particular fixed bandwidth??? There are alots of variables possible..... say i have 33MHZ bandwidth and i have to choose the most suitable modulation technique with some guard band....... one possible way is SHANNON'S CHANNEL CAPACITY limit equation.....that clearly depends on SNR value as bandwidth is fixed... what according to u can be the most appropriate criteria to solve this problem??? Bandwidth is fixed but can be of any value either 36 MHZ or 6MHZ. There is possibility to use multiple users with guard bands or only one user....... so alots of possibilities..... what according to u will be best possible?? Please help..

[Walter Roberson]

The most important criteria to solve the problem is to write the question clearly, using sentences and paragraphs and full words.

[Jan]

Please avoid the "plzzz" and the pile of dots. Concentrate on the problem.

Answer 1

[John BG]

You just asked a really broad question.

You should add more details, as is it a narrow band case?

you are either

1. really short of bandwidth, there is interference, jamming, it is a really expensive band, or

2. you are in broadband: the bandwidth of the BASEBAND signal you want to be received with as high as possible BER is quite lower than the available CHANNEL bandwidth.

And when you say 'THE BEST POSSIBLE MODULATION' it's again confusing,

because what is your (your customer/your boss: THE PRODUCER's) budget?

is it going to be ok with a single tone, QAM, coding, interleaving, off-the-shelf in-the-books technology.

Or your budget is secondary to a critical scenario where the most important thing is to get the right bits on time?

If you want to proceed with this question you need to elaborate:

BASEBAND signal: explain

expected channel noise levels:

expected channel problems:

BAND of choice: L, S Ku .. would you consider Laser?

In a single sentence: How much ($/£/EUR the currency doesn't really matter) are you prepared to invest per transmitted bit/byte/MB ..

The first Voyager is still transmitting, already passed Pluto, it has a mini-nuclear reactor on board.

Do you get a better picture now? hope it helps

John