What types of modulation are used in some of the various wireless applications?
Modulation is a technique in which a carrier wave is used to carry information from one place to another. The sine wave is modified in either amplitude, phase, or frequency, so that the information is present on the wave, and can be decoded at the receiving end. The three major types of digital modulation are: Amplitude Shift Keying (ASK) – ASK is rarely used in wireless applications because multipath effects can dramatically influence the amplitude of the information-bearing signal. This causes errors when the signal is received and decoded. Phase Shift Keying (PSK) Frequency Shift Keying (FSK) PSK and FSK are more common in wireless systems because of their robustness in the presence of multipath. Many hybrid forms of ASK, PSK, and FSK exist. For example, Binary Phase Shift Keying (BPSK) is a form of PSK where only two phase states are allowed. BPSK is highly clear of multipath propagation, but is unused in high data rate applications because of bandwidth inefficiency. Other forms of
