Two Types of CDMA

There are Two types of CDMA:

1. Frequency-Hopping

• Each user’s narrowband signal hops among discrete frequencies, and the receiver follows in sequence
• Frequency-HoppingSpread Spectrum(FHSS)CDMA is NOTcurrently used in wireless systems, although used by the military

1. Direct Sequence

• narrowband input from a user is coded (“spread”) by a user-unique broadband code, then transmitted
• broadband signal is received; receiver knows, applies user’s code, recovers users’data
• Direct SequenceSpread Spectrum(DSSS)CDMA IS the method used in IS-95 commercial systems