Performance of CSSS Signals with Orthogonal Overlay Codes

The use of orthogonal overlay codes in spread spectrum communication systems is relatively well known practice, most often to mitigate the interference of other narrowband communication signals in a shared channel [1] or to facilitate space-time coding in multi-carrier code division multiple access (MC-CDMA) [2] communications. This paper proposes an alternative usage of a variable duration wavelet-like overlay code that helps ensure optimal correlation in Gaussian distributed digital chaotic sequence spread spectrum (CSSS) systems. This process is shown analytically, through fixed precision simulations, and through hardware measurements to improve the effective signal-to-noise ratio (SNR) performance of receivers for these Gaussian chaotic signals, ultimately validating a computationally efficient mechanism for building sequence based carrier shift keying (CSK) modulations from non-constant envelope spreading signals.