Modulation Schemes: DSB-SC, SSB-SC, VSB-SC, FM, PM

Modulation Schemes

DSB-SC

• Lower power consumption is an advantage
• Simple modulation system is present
• Complex detection is a disadvantage.
• Used in analog TV systems for transmitting color information.

SSB-SC

• Better management of the frequency spectrum is an advantage
• Exact SSB generation is difficult
• Used in two-way radio and frequency division multiplexing.

VSB-SC

• A compromise between DSB and SSB
• Easier to generate compared to SSB-SC
• Complex demodulation
• Bandwidth is about 25% greater than SSB-SC.
• Lower power efficiency is a disadvantage.
• Used in analog TV broadcast systems

Items 1^3 with carrier

• Envelope detection is possible
• Used in wireless broadcasting systems.

5, 8, 16 level VSB-SC

• Used in ATSC digital television standard.

FM

• Increased immunity to noise
• Requires a larger bandwidth
• Used in radio broadcasting and direct-satellite broadcasting

PM

• Increased immunity to noise
• More complex receiving hardware is needed
• Used in data-communications systems

PSK

• Power efficient, system is the simplest.
• Low bandwidth efficiency
• Used in low-speed communication

ASK

• Bandwidth efficient
• low power efficiency
• V-32 Telephone data/fax modems are applications
• Satellite transmission of DTVB programs are applications

M-ary PSK

• Requires more bandwidth
• Transmitted power is lower
• Used in V-32 Telephone data/fax modems are applications
• Used in Satellite transmission of DTVB programs are applications

QAM

• Alternative to SSB-SC
• Sharp cutoff band-pass filters are not needed.
• More complex carrier frequency and phase requirements than SSB.
• Used in cable communication for DTV & internet traffic.

SHD AM/FM RECEIVERS

• Increased selectivity against adjacent channels
• Interference from signal frequencies close to the intermediate frequency is a disadvantage
• Used in radio broadcasting.

LINE CODES

• Power efficiency and error detection/correction capability
• Zero Power Spectral Density (PSD) at f=0.
• Transmits one bit of information per T seconds
• Used in optical communications.

M-ary PAM

• Transmits more bits in a symbol time.
• Requires more power (M^2)
• Less system complexity
• Used in high-rate data links.