What is a modem, Computer Engineering

What is a Modem?

Modems are fundamentally used to interface digital circuits to transmit information on analogue channels as telephone systems. Modem is from modulator-demodulator only is a device which modulates an analogue carrier signal to encode digital information as well as demodulates a carrier signal to decode the transmitted information. The aim is to produce a signal which can be transmitted easily and decoded to reproduce the original signal data. These can be used over any means of transmitting analog signals. Two major modulation schemes are currently being utilized to implement ADSL: carrier less amplitude/ phase (CAP) a single carrier modulation scheme depends on discrete multi-tone (DMT) and quadrature amplitude modulation (OAM) i.e. a multichannel modulation scheme. The option between them naturally based on how well they perform in the presence of impairments on the existing copper twisted -pair access cabling as side bar, since these can limit the transmission capacity. Additionally, high bit rate services carried with ADSL should not interfere with other services. In essence, multicarrier modulation superimposes a number of carrier modulated waveforms to signify the input bit stream. The transmitted signal is the sum of these sub-channels (or tones), that has similar band width and similarly spaced center frequencies. The number of tones must be large enough to ensure good performance. In practice, a value of 256 gives near optimum performance whereas ensuring manageable implementation complexity.

Posted Date: 5/15/2013 6:04:23 AM | Location : United States







Related Discussions:- What is a modem, Assignment Help, Ask Question on What is a modem, Get Answer, Expert's Help, What is a modem Discussions

Write discussion on What is a modem
Your posts are moderated
Related Questions
Q. Program for interchanging the values of two Memory locations? Program for interchanging the values of two Memory locations  ; input: Two memory variables of same size:

Q. Explain Sample Instruction Format of MIPS instruction? All MIPS instructions are of same size and are 32 bits long. MIPS designers chose to keep all instructions of same len

Disadvantages of pipeline: Pipeline architecture has 2 major disadvantages.  First is its complexity and second is the inability to constantly run the pipeline at full speed,

This will be based on presentation of the report, complexity of the task, degree of completion and uniqueness of your problem.  As a part of this question, you should also inclu

Explain macro definition. A unit of specification for a program generation is termed as a macro. This consists of name, body of code and set of formal parameters.

Q. Illustrate about Compact Disk Rewritable? CD-RW optical disk can be repeatedly written and overwritten same as with a magnetic disk. Even though a number of techniques have

Differentiate between asynchronous and synchronous types of serial communication. Serial data communication uses two fundamental types, asynchronous andsynchronous. With synchr

VuGen have two options to help debug Vuser scripts-the Run Step by Step command and breakpoints. The Debug settings in the Options dialog box permit us to verify the extent of the

Define swapping.  A process needs to be in memory to be implemented. Though a process can be swapped temporarily out of memory to a backing store and then brought back into mem

What is the point of the REPLACING option of a copy statement? Ans) REPLACING permits for the similar copy to be used more than once in the similar code by changing the replac