Analog, digital
True Digital Signals (Wired)
Generally cheaper than analog signaling
Analog data, digital signal
analog data are encoded using codec to produce a digital bit stream
True Digital Signals (Wired)
A sequence of voltage pulses that may be transmitted over a copper wire medium
analog signal, digital transmission
Assumes that the analog signal represents digital data. Signal is propagatedthrough repeaters; ateach. repeater, digital data are recovered from inbound signal andused to generate a new analog outbound signal.
Radio Attenuation in Free Space
Attenuation loss varies with distance d between transmitter and receiver and with the wavelength lambda
Digital data, analog signal
Digital data are encoded using a modem to produce analog signal.
digital signal, digital transmission
Digital signal represents a stream of Is and Os, which may represent digital data or may be an encoding of analog data. Signal is propagated through repeaters; at each repeater, stream of Is and Os is recovered from inbound signal and used to generate a new digital outbound signal
True Digital Signals (Wired)
Digital signals can propagate (digitized) analog and digital data
analog signal, analog transmission
Is propagated through amplifiers; same treatment whethersignal is used to represent analog data or digital data.
True Digital Signals (Wired)
Less susceptible to noise interference
True Digital Signals (Wired)
Suffer more from attenuation
Digital data, digital signal
Two alternatives: (1) signal consists of two voltage levels to represent the two binary values; (2) digital data are encoded to produce a digital signal with desired properties.
Analog data, analog signal
Two alternatives: (l)signal occupies the same spectrum as the analog data; (2) analog data are encoded to occupy a different portion ofspectrum
Attenuation
depends on the medium and on frequency and distance travelled
Attenuation
is the gradual signal loss due to travel through a medium
digital signal, analog transmission
not used
