Novel magic-square codes for hiding DS/SS signals from intercept receivers

The interest in operating spread spectrum (SS) modulation systems for quiet or covert co-channel communications is growing rapidly. The military require good low probability of intercept (LPI) performance whilst the civil mobile radio community is actively seeking additional spectrum utilisation efficiency through techniques such as co-channel DS/SS multiple access. Previously reported statistically-based chip coding showed considerable promise in its ability to suitably smear the PSDF of the output from a delay-and-multiply (DM) processing receiver thus hiding the chip-line structure. A novel code set has now been investigated in which DS/SS reference sequences are taken from selected numerical vector components of “magic square” arrays. Computer simulation shows that these magic codes produce excellent spectral sidelobe and chip-rate line suppression in a DM receiver. These results are compared with those previously obtained with temporal and/or spectral domain statistical chip code designs