2. Why Carrier Modulation?
Until now we have been looking at
baseband communications
The information is sampled, quantized
pulse coded and transmitted in baseband
However, baseband transmission is not
suitable in many situations
Carrier modulation is needed in these
cases
Fe examples are listed in the next few
slides
3. Wireless Communications
Examples:
FM Radio: 88 – 108 MHz
WLAN – 2.4 or 5 GHz
Cellular Radio: 806-890 MHz
GPS: 1215 – 1240 MHz
The air-interface is shared by many different
users & services
Each service has a certain allocated frequency
Carrier modulation is needed to occupy only
the given spectrum
4. Digital Telephony/Cable Modem
Many of you may have Rogers Digital
Phone & Cable Modem
The voice and internet data is modulated
on a carrier frequency (not overlapping
with TV Bands) and transmitted via cable
in addition TV Channels using QPSK or
16QAM modulation
TV Bands: 60-88 MHz, 180 – 216 MHz
and 476-890 MHz