Reference : Modulation
Four "old" telecom terms (i.e. modulation, spread
spectrum, multiplexing, and multiple access) are discussed here because the
concepts are very important in telecom and networking, especially
in the process of transmitting and receiving signals. The
following paragraphs describe the terms briefly.
Modulation is a technique that
puts a baseband signal on a
make it feasible and more efficient for transmission and reception. The baseband
signal is the message or information that will be transmitted. With modulation, the
carrier is modified by the
baseband signal. With demodulation, the baseband signal is taken
from the modulated carrier and the modulated carrier is returned to its
Spread spectrum is the spread of signal over much wider bandwidth
than is needed for transmission. Spread spectrum technique is used
to reduce the effect of interference.
Multiplexing is a technique that puts multiple baseband signals
that come from multiple stations in
one communication channel to maximize traffic-carrying
capacity of the channel. Multiplexing results in more efficient
use of bandwidth and faster transmission speed (higher data rate).
Multiple access is a method for
accessing and sharing a communication medium by multiple stations.
The table below lists some well-known techniques used in
telecom and networking. Click on each technique to see its definition.