about digital communication...

hello every one...
can you tell some real world application of digital communication?????
and is it economical OR NOT in comparison of analogue communication???????
thank you very much........

Hi, your question is VERY wide. I think you should better define which kind of communication you mean.
I have some real world experience with radio communications. Digital is more expensive, and this is true both for the radio terminal (handheld, vehicular and so on) and for the infrastructure, if you need one. Moreover, to achieve the same quality level the digital infrastructure needs 10-15% more BTS (this is my experience, at least).
On the other hand, you have several advantages like true point-to-point communication, data+voice, "high speed" data and so on.

Examples of digital communications -> morse code, cell phones, modern telephone exchanges, digital TVs, internet protocol.... It is a different beast to analogue. It can do much more then analogue. - self healing networks, packet switching etc. Morse code is the most basic of long distance communications, very slow, generation and reception kit is easy and cheap. If we call this technology 1 in cost, then the cell phone should be 300,000,000,000 in cost, but with modern technology and mass production, actual cost is 5(?)
Frank

digi-telecomm have some advantages:
1. In a limit bandwidth, it can have almost infinite users, due to CDMA/FDMA/TDMA/etc.
2. It has very high voice quality, data rate, etc.
3. It can be encrypted easily.
4. It can strongly anti-burst noise.
5. It need very low SNR/ENR, due to CDMA/Veterbi deoder, etc.

Not trying to be a prick, but in my opinion this is an area width wide misunderstanding.
Digital communication, I assume is when two equipment exchanges information in binary form such as between two digital IC's on a PCB. Morse is a protocol in a time multiplex form, not a way to communicate. Most common is this protocol used to modulates a audible sinus signal so from radio view is it then a very analog communication. Most modulation types can be used to transfer Morse or any else analog or digital information. AM FM PSK QAM are the most common modulation types and all off them are used to transfer both digital information as well as analog such as Audio or TV.
It it easy to forget that TV modulated as DVB-T or ATSC is analog communication even if it is sampled in digital pieces in a part of its modulation chain, compressed and repacked according to a protocol. Exampel of these protocol are DVB-t and ATSC. Resulting transport stream can then be feed to a RF modulator which often is of QAM type.
In some theoretical calculations is a QAM assumed to be a digital digital unit but as long as we not have transistors with infinite rise time must these modulators be built with very analog components.
For same reason are all modern transmitters/receivers analog amplifiers. These equipments don't care about if the information will end in a digital number or as analog sound in a Bluetooth headset. Some people even talks about digital antennas. Have not seen any yet and don't believe they exist.
And no, the RF waves have not been given some kind of smartness or self routing depending on what modulation it is based on.
Required SNR is depending on robustness of the protocol. DVB-t requires about 20 dB for good quality, PAL 40 dB, Morse over tone modulated AM transmitter and with a good operator requires less then 2 dB S/N.

About the cost is it mostly depending on needed coverage and type of protocol.
A complex protocol with high information density and a requirement of zero BER will be expansive to transfer over RF or wire or even storage on a CD with good reliability that the information can successfully be retrieved by final receiver. Complexity in software do often also require more expensive hardware such as relative fast CPU and plenty of memory, as for DVB-t. It is one of the main reason that DVB-t not have been possible to implement in a hand held phone. A power hungry TV CPU and a phone with a small battery is not a good combination.
Selected type of protocol is a important factor for cost. For a complete infrastructure to cover several hundred miles is a long wire and a car battery all you need if you use Morse as protocol and the receiver can be almost as simple. Low information density but the cost is hard to beat and reliability is excellent.