Performance analysis of M-ary code shift keying in code division multiple access systems

A performance evaluation of asynchronous code division multiple access systems, using M-ary code shift keying, is presented. The M-ary sequences are approximated either by biorthogonal or transorthogonal codes. Error probability expressions, due to CDMA interference and thermal noise, are derived as a function of the system processing gain and other parameters. The results indicate that the error probability decreases when the number of M-ary symbols is increased. Finally, the channel capacity is discussed and an upper bound on the size of the M-ary signal set is determined.