The digital modulation step gives the ability to provide more relevant information related to the source data. In keeping with the digital information services, higher data security, better quality communication and faster system availability are the key responsibilities of digital modulation.
The Developers who observe some limitations on the communication system which are:
► Available bandwidth
► Permissible power
► Inherent noise level of the system
The Users’ demand is increasing day by day and they want more information and security. Digital modulation schemes have capacity to convey large amounts of information than analog modulation schemes.
To transmit a signal, one should follow three main steps:
► A pure carrier signal should be generate from the transmitter.
► Other relevant information of original signals or signal properties must be modulated during transmitting. The signal properties can carry any reliably identifiable information.
► If anybody change any properties of the carrier, the receiver’s must be detect and de-modulate also. So, Changes in career properties must be consistent.
Here is a list which have some modulation types and its usages:
|MSK, GMSK||CDPD, GSM|
|BPSK||Deep space telemetry, Cable modems|
|QPSK, π/4 DQPSK||Satellite, CDMA, TETRA, NADC, PHS, LMDC, PDC, DVB-S, Cable Modems, TFTS|
|FSK, GFSK||RAM mobile data, DECT paging, CT2, AMPS, ERMES, public safety, land mobile.|
|8, 16-VSB||North American digital TV (ATV), cable, Broadcast|
|8 PSK||Aircraft, Satellite, Telemetry pilots for monitoring broadband video system.|
|16 QAM||Microwave digital radio, modems, DVB-C, DVB-T|
|32 QAM||Terrestrial microwave, DVB-T|
|64 QAM||DVB-C, broadband set top boxes, modems, MMDS|
|256 QAM||Modems, DVB-V(Europe), Digital video (US)|